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 printing 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 generate the outermost <book> element that wraps then 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 "4.86"
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 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 . --- the 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 the program,
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 the 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, the 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(http://www.uit.co.uk/exim-book/)).
397 This 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 the program 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 the program (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"
441 The main specification and the specification of the filtering language are also
442 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
443 &<<SECTavail>>& below tells you how to get hold of these.
447 .section "FTP and web sites" "SECID2"
450 The primary site for Exim source distributions is currently the University of
451 Cambridge's FTP site, whose contents are described in &'Where to find the Exim
452 distribution'& below. In addition, there is a web site and an FTP site at
453 &%exim.org%&. These are now also hosted at the University of Cambridge. The
454 &%exim.org%& site was previously hosted for a number of years by Energis
455 Squared, formerly Planet Online Ltd, whose support I gratefully acknowledge.
459 As well as Exim distribution tar files, the Exim web site contains a number of
460 differently formatted versions of the documentation. A recent addition to the
461 online information is the Exim wiki (&url(http://wiki.exim.org)),
462 which contains what used to be a separate FAQ, as well as various other
463 examples, tips, and know-how that have been contributed by Exim users.
466 An Exim Bugzilla exists at &url(http://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.
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(http://lists.alioth.debian.org/mailman/listinfo/pkg-exim4-users)
492 Please ask Debian-specific questions on this list and not on the general Exim
495 .section "Exim training" "SECID4"
496 .cindex "training courses"
497 Training courses in Cambridge (UK) used to be run annually by the author of
498 Exim, before he retired. At the time of writing, there are no plans to run
499 further Exim courses in Cambridge. However, if that changes, relevant
500 information will be posted at &url(http://www-tus.csx.cam.ac.uk/courses/exim/).
502 .section "Bug reports" "SECID5"
503 .cindex "bug reports"
504 .cindex "reporting bugs"
505 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
506 via the Bugzilla (&url(http://bugs.exim.org)). However, if you are unsure
507 whether some behaviour is a bug or not, the best thing to do is to post a
508 message to the &'exim-dev'& mailing list and have it discussed.
512 .section "Where to find the Exim distribution" "SECTavail"
514 .cindex "distribution" "ftp site"
515 The master ftp site for the Exim distribution is
517 &*ftp://ftp.csx.cam.ac.uk/pub/software/email/exim*&
521 &*ftp://ftp.exim.org/pub/exim*&
523 The file references that follow are relative to the &_exim_& directories at
524 these sites. There are now quite a number of independent mirror sites around
525 the world. Those that I know about are listed in the file called &_Mirrors_&.
527 Within the &_exim_& directory there are subdirectories called &_exim3_& (for
528 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
529 distributions), and &_Testing_& for testing versions. In the &_exim4_&
530 subdirectory, the current release can always be found in files called
533 &_exim-n.nn.tar.bz2_&
535 where &'n.nn'& is the highest such version number in the directory. The two
536 files contain identical data; the only difference is the type of compression.
537 The &_.bz2_& file is usually a lot smaller than the &_.gz_& file.
539 .cindex "distribution" "signing details"
540 .cindex "distribution" "public key"
541 .cindex "public key for signed distribution"
542 The distributions will be PGP signed by an individual key of the Release
543 Coordinator. This key will have a uid containing an email address in the
544 &'exim.org'& domain and will have signatures from other people, including
545 other Exim maintainers. We expect that the key will be in the "strong set" of
546 PGP keys. There should be a trust path to that key from Nigel Metheringham's
547 PGP key, a version of which can be found in the release directory in the file
548 &_nigel-pubkey.asc_&. All keys used will be available in public keyserver pools,
549 such as &'pool.sks-keyservers.net'&.
551 At time of last update, releases were being made by Phil Pennock and signed with
552 key &'0x403043153903637F'&, although that key is expected to be replaced in 2013.
553 A trust path from Nigel's key to Phil's can be observed at
554 &url(https://www.security.spodhuis.org/exim-trustpath).
556 Releases have also been authorized to be performed by Todd Lyons who signs with
557 key &'0xC4F4F94804D29EBA'&. A direct trust path exists between previous RE Phil
558 Pennock and Todd Lyons through a common associate.
560 The signatures for the tar bundles are in:
562 &_exim-n.nn.tar.gz.asc_&
563 &_exim-n.nn.tar.bz2.asc_&
565 For each released version, the log of changes is made separately available in a
566 separate file in the directory &_ChangeLogs_& so that it is possible to
567 find out what has changed without having to download the entire distribution.
569 .cindex "documentation" "available formats"
570 The main distribution contains ASCII versions of this specification and other
571 documentation; other formats of the documents are available in separate files
572 inside the &_exim4_& directory of the FTP site:
574 &_exim-html-n.nn.tar.gz_&
575 &_exim-pdf-n.nn.tar.gz_&
576 &_exim-postscript-n.nn.tar.gz_&
577 &_exim-texinfo-n.nn.tar.gz_&
579 These tar files contain only the &_doc_& directory, not the complete
580 distribution, and are also available in &_.bz2_& as well as &_.gz_& forms.
583 .section "Limitations" "SECID6"
585 .cindex "limitations of Exim"
586 .cindex "bang paths" "not handled by Exim"
587 Exim is designed for use as an Internet MTA, and therefore handles addresses in
588 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
589 simple two-component bang paths can be converted by a straightforward rewriting
590 configuration. This restriction does not prevent Exim from being interfaced to
591 UUCP as a transport mechanism, provided that domain addresses are used.
593 .cindex "domainless addresses"
594 .cindex "address" "without domain"
595 Exim insists that every address it handles has a domain attached. For incoming
596 local messages, domainless addresses are automatically qualified with a
597 configured domain value. Configuration options specify from which remote
598 systems unqualified addresses are acceptable. These are then qualified on
601 .cindex "transport" "external"
602 .cindex "external transports"
603 The only external transport mechanisms that are currently implemented are SMTP
604 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
605 transport is available, and there are facilities for writing messages to files
606 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
607 to send messages to other transport mechanisms such as UUCP, provided they can
608 handle domain-style addresses. Batched SMTP input is also catered for.
610 Exim is not designed for storing mail for dial-in hosts. When the volumes of
611 such mail are large, it is better to get the messages &"delivered"& into files
612 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
615 Although Exim does have basic facilities for scanning incoming messages, these
616 are not comprehensive enough to do full virus or spam scanning. Such operations
617 are best carried out using additional specialized software packages. If you
618 compile Exim with the content-scanning extension, straightforward interfaces to
619 a number of common scanners are provided.
623 .section "Run time configuration" "SECID7"
624 Exim's run time configuration is held in a single text file that is divided
625 into a number of sections. The entries in this file consist of keywords and
626 values, in the style of Smail 3 configuration files. A default configuration
627 file which is suitable for simple online installations is provided in the
628 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
631 .section "Calling interface" "SECID8"
632 .cindex "Sendmail compatibility" "command line interface"
633 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
634 can be a straight replacement for &_/usr/lib/sendmail_& or
635 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
636 about Sendmail in order to run Exim. For actions other than sending messages,
637 Sendmail-compatible options also exist, but those that produce output (for
638 example, &%-bp%&, which lists the messages on the queue) do so in Exim's own
639 format. There are also some additional options that are compatible with Smail
640 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
641 documents all Exim's command line options. This information is automatically
642 made into the man page that forms part of the Exim distribution.
644 Control of messages on the queue can be done via certain privileged command
645 line options. There is also an optional monitor program called &'eximon'&,
646 which displays current information in an X window, and which contains a menu
647 interface to Exim's command line administration options.
651 .section "Terminology" "SECID9"
652 .cindex "terminology definitions"
653 .cindex "body of message" "definition of"
654 The &'body'& of a message is the actual data that the sender wants to transmit.
655 It is the last part of a message, and is separated from the &'header'& (see
656 below) by a blank line.
658 .cindex "bounce message" "definition of"
659 When a message cannot be delivered, it is normally returned to the sender in a
660 delivery failure message or a &"non-delivery report"& (NDR). The term
661 &'bounce'& is commonly used for this action, and the error reports are often
662 called &'bounce messages'&. This is a convenient shorthand for &"delivery
663 failure error report"&. Such messages have an empty sender address in the
664 message's &'envelope'& (see below) to ensure that they cannot themselves give
665 rise to further bounce messages.
667 The term &'default'& appears frequently in this manual. It is used to qualify a
668 value which is used in the absence of any setting in the configuration. It may
669 also qualify an action which is taken unless a configuration setting specifies
672 The term &'defer'& is used when the delivery of a message to a specific
673 destination cannot immediately take place for some reason (a remote host may be
674 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
677 The word &'domain'& is sometimes used to mean all but the first component of a
678 host's name. It is &'not'& used in that sense here, where it normally refers to
679 the part of an email address following the @ sign.
681 .cindex "envelope, definition of"
682 .cindex "sender" "definition of"
683 A message in transit has an associated &'envelope'&, as well as a header and a
684 body. The envelope contains a sender address (to which bounce messages should
685 be delivered), and any number of recipient addresses. References to the
686 sender or the recipients of a message usually mean the addresses in the
687 envelope. An MTA uses these addresses for delivery, and for returning bounce
688 messages, not the addresses that appear in the header lines.
690 .cindex "message" "header, definition of"
691 .cindex "header section" "definition of"
692 The &'header'& of a message is the first part of a message's text, consisting
693 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
694 &'Subject:'&, etc. Long header lines can be split over several text lines by
695 indenting the continuations. The header is separated from the body by a blank
698 .cindex "local part" "definition of"
699 .cindex "domain" "definition of"
700 The term &'local part'&, which is taken from RFC 2822, is used to refer to that
701 part of an email address that precedes the @ sign. The part that follows the
702 @ sign is called the &'domain'& or &'mail domain'&.
704 .cindex "local delivery" "definition of"
705 .cindex "remote delivery, definition of"
706 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
707 delivery to a file or a pipe on the local host from delivery by SMTP over
708 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
709 host it is running on are &'remote'&.
711 .cindex "return path" "definition of"
712 &'Return path'& is another name that is used for the sender address in a
715 .cindex "queue" "definition of"
716 The term &'queue'& is used to refer to the set of messages awaiting delivery,
717 because this term is in widespread use in the context of MTAs. However, in
718 Exim's case the reality is more like a pool than a queue, because there is
719 normally no ordering of waiting messages.
721 .cindex "queue runner" "definition of"
722 The term &'queue runner'& is used to describe a process that scans the queue
723 and attempts to deliver those messages whose retry times have come. This term
724 is used by other MTAs, and also relates to the command &%runq%&, but in Exim
725 the waiting messages are normally processed in an unpredictable order.
727 .cindex "spool directory" "definition of"
728 The term &'spool directory'& is used for a directory in which Exim keeps the
729 messages on its queue &-- that is, those that it is in the process of
730 delivering. This should not be confused with the directory in which local
731 mailboxes are stored, which is called a &"spool directory"& by some people. In
732 the Exim documentation, &"spool"& is always used in the first sense.
739 . ////////////////////////////////////////////////////////////////////////////
740 . ////////////////////////////////////////////////////////////////////////////
742 .chapter "Incorporated code" "CHID2"
743 .cindex "incorporated code"
744 .cindex "regular expressions" "library"
747 A number of pieces of external code are included in the Exim distribution.
750 Regular expressions are supported in the main Exim program and in the
751 Exim monitor using the freely-distributable PCRE library, copyright
752 © University of Cambridge. The source to PCRE is no longer shipped with
753 Exim, so you will need to use the version of PCRE shipped with your system,
754 or obtain and install the full version of the library from
755 &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
757 .cindex "cdb" "acknowledgment"
758 Support for the cdb (Constant DataBase) lookup method is provided by code
759 contributed by Nigel Metheringham of (at the time he contributed it) Planet
760 Online Ltd. The implementation is completely contained within the code of Exim.
761 It does not link against an external cdb library. The code contains the
762 following statements:
765 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
767 This program is free software; you can redistribute it and/or modify it under
768 the terms of the GNU General Public License as published by the Free Software
769 Foundation; either version 2 of the License, or (at your option) any later
771 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
772 the spec and sample code for cdb can be obtained from
773 &url(http://www.pobox.com/~djb/cdb.html). This implementation borrows
774 some code from Dan Bernstein's implementation (which has no license
775 restrictions applied to it).
778 .cindex "SPA authentication"
779 .cindex "Samba project"
780 .cindex "Microsoft Secure Password Authentication"
781 Client support for Microsoft's &'Secure Password Authentication'& is provided
782 by code contributed by Marc Prud'hommeaux. Server support was contributed by
783 Tom Kistner. This includes code taken from the Samba project, which is released
787 .cindex "&'pwcheck'& daemon"
788 .cindex "&'pwauthd'& daemon"
789 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
790 by code taken from the Cyrus-SASL library and adapted by Alexander S.
791 Sabourenkov. The permission notice appears below, in accordance with the
792 conditions expressed therein.
795 Copyright © 2001 Carnegie Mellon University. All rights reserved.
797 Redistribution and use in source and binary forms, with or without
798 modification, are permitted provided that the following conditions
802 Redistributions of source code must retain the above copyright
803 notice, this list of conditions and the following disclaimer.
805 Redistributions in binary form must reproduce the above copyright
806 notice, this list of conditions and the following disclaimer in
807 the documentation and/or other materials provided with the
810 The name &"Carnegie Mellon University"& must not be used to
811 endorse or promote products derived from this software without
812 prior written permission. For permission or any other legal
813 details, please contact
815 Office of Technology Transfer
816 Carnegie Mellon University
818 Pittsburgh, PA 15213-3890
819 (412) 268-4387, fax: (412) 268-7395
820 tech-transfer@andrew.cmu.edu
823 Redistributions of any form whatsoever must retain the following
826 &"This product includes software developed by Computing Services
827 at Carnegie Mellon University (&url(http://www.cmu.edu/computing/)."&
829 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
830 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
831 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
832 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
833 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
834 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
835 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
840 .cindex "Exim monitor" "acknowledgment"
843 The Exim Monitor program, which is an X-Window application, includes
844 modified versions of the Athena StripChart and TextPop widgets.
845 This code is copyright by DEC and MIT, and their permission notice appears
846 below, in accordance with the conditions expressed therein.
849 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
850 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
854 Permission to use, copy, modify, and distribute this software and its
855 documentation for any purpose and without fee is hereby granted,
856 provided that the above copyright notice appear in all copies and that
857 both that copyright notice and this permission notice appear in
858 supporting documentation, and that the names of Digital or MIT not be
859 used in advertising or publicity pertaining to distribution of the
860 software without specific, written prior permission.
862 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
863 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
864 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
865 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
866 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
867 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
872 .cindex "opendmarc" "acknowledgment"
873 The DMARC implementation uses the OpenDMARC library which is Copyrighted by
874 The Trusted Domain Project. Portions of Exim source which use OpenDMARC
875 derived code are indicated in the respective source files. The full OpenDMARC
876 license is provided in the LICENSE.opendmarc file contained in the distributed
880 Many people have contributed code fragments, some large, some small, that were
881 not covered by any specific licence requirements. It is assumed that the
882 contributors are happy to see their code incorporated into Exim under the GPL.
889 . ////////////////////////////////////////////////////////////////////////////
890 . ////////////////////////////////////////////////////////////////////////////
892 .chapter "How Exim receives and delivers mail" "CHID11" &&&
893 "Receiving and delivering mail"
896 .section "Overall philosophy" "SECID10"
897 .cindex "design philosophy"
898 Exim is designed to work efficiently on systems that are permanently connected
899 to the Internet and are handling a general mix of mail. In such circumstances,
900 most messages can be delivered immediately. Consequently, Exim does not
901 maintain independent queues of messages for specific domains or hosts, though
902 it does try to send several messages in a single SMTP connection after a host
903 has been down, and it also maintains per-host retry information.
906 .section "Policy control" "SECID11"
907 .cindex "policy control" "overview"
908 Policy controls are now an important feature of MTAs that are connected to the
909 Internet. Perhaps their most important job is to stop MTAs being abused as
910 &"open relays"& by misguided individuals who send out vast amounts of
911 unsolicited junk, and want to disguise its source. Exim provides flexible
912 facilities for specifying policy controls on incoming mail:
915 .cindex "&ACL;" "introduction"
916 Exim 4 (unlike previous versions of Exim) implements policy controls on
917 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
918 series of statements that may either grant or deny access. ACLs can be used at
919 several places in the SMTP dialogue while receiving a message from a remote
920 host. However, the most common places are after each RCPT command, and at the
921 very end of the message. The sysadmin can specify conditions for accepting or
922 rejecting individual recipients or the entire message, respectively, at these
923 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
926 An ACL is also available for locally generated, non-SMTP messages. In this
927 case, the only available actions are to accept or deny the entire message.
929 When Exim is compiled with the content-scanning extension, facilities are
930 provided in the ACL mechanism for passing the message to external virus and/or
931 spam scanning software. The result of such a scan is passed back to the ACL,
932 which can then use it to decide what to do with the message.
934 When a message has been received, either from a remote host or from the local
935 host, but before the final acknowledgment has been sent, a locally supplied C
936 function called &[local_scan()]& can be run to inspect the message and decide
937 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
938 is accepted, the list of recipients can be modified by the function.
940 Using the &[local_scan()]& mechanism is another way of calling external scanner
941 software. The &%SA-Exim%& add-on package works this way. It does not require
942 Exim to be compiled with the content-scanning extension.
944 After a message has been accepted, a further checking mechanism is available in
945 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
946 runs at the start of every delivery process.
951 .section "User filters" "SECID12"
952 .cindex "filter" "introduction"
953 .cindex "Sieve filter"
954 In a conventional Exim configuration, users are able to run private filters by
955 setting up appropriate &_.forward_& files in their home directories. See
956 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
957 configuration needed to support this, and the separate document entitled
958 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
959 of filtering are available:
962 Sieve filters are written in the standard filtering language that is defined
965 Exim filters are written in a syntax that is unique to Exim, but which is more
966 powerful than Sieve, which it pre-dates.
969 User filters are run as part of the routing process, described below.
973 .section "Message identification" "SECTmessiden"
974 .cindex "message ids" "details of format"
975 .cindex "format" "of message id"
976 .cindex "id of message"
981 Every message handled by Exim is given a &'message id'& which is sixteen
982 characters long. It is divided into three parts, separated by hyphens, for
983 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
984 normally encoding numbers in base 62. However, in the Darwin operating
985 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
986 (avoiding the use of lower case letters) is used instead, because the message
987 id is used to construct file names, and the names of files in those systems are
988 not always case-sensitive.
990 .cindex "pid (process id)" "re-use of"
991 The detail of the contents of the message id have changed as Exim has evolved.
992 Earlier versions relied on the operating system not re-using a process id (pid)
993 within one second. On modern operating systems, this assumption can no longer
994 be made, so the algorithm had to be changed. To retain backward compatibility,
995 the format of the message id was retained, which is why the following rules are
999 The first six characters of the message id are the time at which the message
1000 started to be received, to a granularity of one second. That is, this field
1001 contains the number of seconds since the start of the epoch (the normal Unix
1002 way of representing the date and time of day).
1004 After the first hyphen, the next six characters are the id of the process that
1005 received the message.
1007 There are two different possibilities for the final two characters:
1009 .oindex "&%localhost_number%&"
1010 If &%localhost_number%& is not set, this value is the fractional part of the
1011 time of reception, normally in units of 1/2000 of a second, but for systems
1012 that must use base 36 instead of base 62 (because of case-insensitive file
1013 systems), the units are 1/1000 of a second.
1015 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
1016 the fractional part of the time, which in this case is in units of 1/200
1017 (1/100) of a second.
1021 After a message has been received, Exim waits for the clock to tick at the
1022 appropriate resolution before proceeding, so that if another message is
1023 received by the same process, or by another process with the same (re-used)
1024 pid, it is guaranteed that the time will be different. In most cases, the clock
1025 will already have ticked while the message was being received.
1028 .section "Receiving mail" "SECID13"
1029 .cindex "receiving mail"
1030 .cindex "message" "reception"
1031 The only way Exim can receive mail from another host is using SMTP over
1032 TCP/IP, in which case the sender and recipient addresses are transferred using
1033 SMTP commands. However, from a locally running process (such as a user's MUA),
1034 there are several possibilities:
1037 If the process runs Exim with the &%-bm%& option, the message is read
1038 non-interactively (usually via a pipe), with the recipients taken from the
1039 command line, or from the body of the message if &%-t%& is also used.
1041 If the process runs Exim with the &%-bS%& option, the message is also read
1042 non-interactively, but in this case the recipients are listed at the start of
1043 the message in a series of SMTP RCPT commands, terminated by a DATA
1044 command. This is so-called &"batch SMTP"& format,
1045 but it isn't really SMTP. The SMTP commands are just another way of passing
1046 envelope addresses in a non-interactive submission.
1048 If the process runs Exim with the &%-bs%& option, the message is read
1049 interactively, using the SMTP protocol. A two-way pipe is normally used for
1050 passing data between the local process and the Exim process.
1051 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1052 example, the ACLs for SMTP commands are used for this form of submission.
1054 A local process may also make a TCP/IP call to the host's loopback address
1055 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1056 does not treat the loopback address specially. It treats all such connections
1057 in the same way as connections from other hosts.
1061 .cindex "message sender, constructed by Exim"
1062 .cindex "sender" "constructed by Exim"
1063 In the three cases that do not involve TCP/IP, the sender address is
1064 constructed from the login name of the user that called Exim and a default
1065 qualification domain (which can be set by the &%qualify_domain%& configuration
1066 option). For local or batch SMTP, a sender address that is passed using the
1067 SMTP MAIL command is ignored. However, the system administrator may allow
1068 certain users (&"trusted users"&) to specify a different sender address
1069 unconditionally, or all users to specify certain forms of different sender
1070 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1071 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1072 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1073 users to change sender addresses.
1075 Messages received by either of the non-interactive mechanisms are subject to
1076 checking by the non-SMTP ACL, if one is defined. Messages received using SMTP
1077 (either over TCP/IP, or interacting with a local process) can be checked by a
1078 number of ACLs that operate at different times during the SMTP session. Either
1079 individual recipients, or the entire message, can be rejected if local policy
1080 requirements are not met. The &[local_scan()]& function (see chapter
1081 &<<CHAPlocalscan>>&) is run for all incoming messages.
1083 Exim can be configured not to start a delivery process when a message is
1084 received; this can be unconditional, or depend on the number of incoming SMTP
1085 connections or the system load. In these situations, new messages wait on the
1086 queue until a queue runner process picks them up. However, in standard
1087 configurations under normal conditions, delivery is started as soon as a
1088 message is received.
1094 .section "Handling an incoming message" "SECID14"
1095 .cindex "spool directory" "files that hold a message"
1096 .cindex "file" "how a message is held"
1097 When Exim accepts a message, it writes two files in its spool directory. The
1098 first contains the envelope information, the current status of the message, and
1099 the header lines, and the second contains the body of the message. The names of
1100 the two spool files consist of the message id, followed by &`-H`& for the
1101 file containing the envelope and header, and &`-D`& for the data file.
1103 .cindex "spool directory" "&_input_& sub-directory"
1104 By default all these message files are held in a single directory called
1105 &_input_& inside the general Exim spool directory. Some operating systems do
1106 not perform very well if the number of files in a directory gets large; to
1107 improve performance in such cases, the &%split_spool_directory%& option can be
1108 used. This causes Exim to split up the input files into 62 sub-directories
1109 whose names are single letters or digits. When this is done, the queue is
1110 processed one sub-directory at a time instead of all at once, which can improve
1111 overall performance even when there are not enough files in each directory to
1112 affect file system performance.
1114 The envelope information consists of the address of the message's sender and
1115 the addresses of the recipients. This information is entirely separate from
1116 any addresses contained in the header lines. The status of the message includes
1117 a list of recipients who have already received the message. The format of the
1118 first spool file is described in chapter &<<CHAPspool>>&.
1120 .cindex "rewriting" "addresses"
1121 Address rewriting that is specified in the rewrite section of the configuration
1122 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1123 both in the header lines and the envelope, at the time the message is accepted.
1124 If during the course of delivery additional addresses are generated (for
1125 example, via aliasing), these new addresses are rewritten as soon as they are
1126 generated. At the time a message is actually delivered (transported) further
1127 rewriting can take place; because this is a transport option, it can be
1128 different for different forms of delivery. It is also possible to specify the
1129 addition or removal of certain header lines at the time the message is
1130 delivered (see chapters &<<CHAProutergeneric>>& and
1131 &<<CHAPtransportgeneric>>&).
1135 .section "Life of a message" "SECID15"
1136 .cindex "message" "life of"
1137 .cindex "message" "frozen"
1138 A message remains in the spool directory until it is completely delivered to
1139 its recipients or to an error address, or until it is deleted by an
1140 administrator or by the user who originally created it. In cases when delivery
1141 cannot proceed &-- for example, when a message can neither be delivered to its
1142 recipients nor returned to its sender, the message is marked &"frozen"& on the
1143 spool, and no more deliveries are attempted.
1145 .cindex "frozen messages" "thawing"
1146 .cindex "message" "thawing frozen"
1147 An administrator can &"thaw"& such messages when the problem has been
1148 corrected, and can also freeze individual messages by hand if necessary. In
1149 addition, an administrator can force a delivery error, causing a bounce message
1152 .oindex "&%timeout_frozen_after%&"
1153 .oindex "&%ignore_bounce_errors_after%&"
1154 There are options called &%ignore_bounce_errors_after%& and
1155 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1156 The first applies only to frozen bounces, the second to any frozen messages.
1158 .cindex "message" "log file for"
1159 .cindex "log" "file for each message"
1160 While Exim is working on a message, it writes information about each delivery
1161 attempt to its main log file. This includes successful, unsuccessful, and
1162 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1163 lines are also written to a separate &'message log'& file for each message.
1164 These logs are solely for the benefit of the administrator, and are normally
1165 deleted along with the spool files when processing of a message is complete.
1166 The use of individual message logs can be disabled by setting
1167 &%no_message_logs%&; this might give an improvement in performance on very busy
1170 .cindex "journal file"
1171 .cindex "file" "journal"
1172 All the information Exim itself needs to set up a delivery is kept in the first
1173 spool file, along with the header lines. When a successful delivery occurs, the
1174 address is immediately written at the end of a journal file, whose name is the
1175 message id followed by &`-J`&. At the end of a delivery run, if there are some
1176 addresses left to be tried again later, the first spool file (the &`-H`& file)
1177 is updated to indicate which these are, and the journal file is then deleted.
1178 Updating the spool file is done by writing a new file and renaming it, to
1179 minimize the possibility of data loss.
1181 Should the system or the program crash after a successful delivery but before
1182 the spool file has been updated, the journal is left lying around. The next
1183 time Exim attempts to deliver the message, it reads the journal file and
1184 updates the spool file before proceeding. This minimizes the chances of double
1185 deliveries caused by crashes.
1189 .section "Processing an address for delivery" "SECTprocaddress"
1190 .cindex "drivers" "definition of"
1191 .cindex "router" "definition of"
1192 .cindex "transport" "definition of"
1193 The main delivery processing elements of Exim are called &'routers'& and
1194 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1195 number of them is provided in the source distribution, and compile-time options
1196 specify which ones are included in the binary. Run time options specify which
1197 ones are actually used for delivering messages.
1199 .cindex "drivers" "instance definition"
1200 Each driver that is specified in the run time configuration is an &'instance'&
1201 of that particular driver type. Multiple instances are allowed; for example,
1202 you can set up several different &(smtp)& transports, each with different
1203 option values that might specify different ports or different timeouts. Each
1204 instance has its own identifying name. In what follows we will normally use the
1205 instance name when discussing one particular instance (that is, one specific
1206 configuration of the driver), and the generic driver name when discussing
1207 the driver's features in general.
1209 A &'router'& is a driver that operates on an address, either determining how
1210 its delivery should happen, by assigning it to a specific transport, or
1211 converting the address into one or more new addresses (for example, via an
1212 alias file). A router may also explicitly choose to fail an address, causing it
1215 A &'transport'& is a driver that transmits a copy of the message from Exim's
1216 spool to some destination. There are two kinds of transport: for a &'local'&
1217 transport, the destination is a file or a pipe on the local host, whereas for a
1218 &'remote'& transport the destination is some other host. A message is passed
1219 to a specific transport as a result of successful routing. If a message has
1220 several recipients, it may be passed to a number of different transports.
1222 .cindex "preconditions" "definition of"
1223 An address is processed by passing it to each configured router instance in
1224 turn, subject to certain preconditions, until a router accepts the address or
1225 specifies that it should be bounced. We will describe this process in more
1226 detail shortly. First, as a simple example, we consider how each recipient
1227 address in a message is processed in a small configuration of three routers.
1229 To make this a more concrete example, it is described in terms of some actual
1230 routers, but remember, this is only an example. You can configure Exim's
1231 routers in many different ways, and there may be any number of routers in a
1234 The first router that is specified in a configuration is often one that handles
1235 addresses in domains that are not recognized specially by the local host. These
1236 are typically addresses for arbitrary domains on the Internet. A precondition
1237 is set up which looks for the special domains known to the host (for example,
1238 its own domain name), and the router is run for addresses that do &'not'&
1239 match. Typically, this is a router that looks up domains in the DNS in order to
1240 find the hosts to which this address routes. If it succeeds, the address is
1241 assigned to a suitable SMTP transport; if it does not succeed, the router is
1242 configured to fail the address.
1244 The second router is reached only when the domain is recognized as one that
1245 &"belongs"& to the local host. This router does redirection &-- also known as
1246 aliasing and forwarding. When it generates one or more new addresses from the
1247 original, each of them is routed independently from the start. Otherwise, the
1248 router may cause an address to fail, or it may simply decline to handle the
1249 address, in which case the address is passed to the next router.
1251 The final router in many configurations is one that checks to see if the
1252 address belongs to a local mailbox. The precondition may involve a check to
1253 see if the local part is the name of a login account, or it may look up the
1254 local part in a file or a database. If its preconditions are not met, or if
1255 the router declines, we have reached the end of the routers. When this happens,
1256 the address is bounced.
1260 .section "Processing an address for verification" "SECID16"
1261 .cindex "router" "for verification"
1262 .cindex "verifying address" "overview"
1263 As well as being used to decide how to deliver to an address, Exim's routers
1264 are also used for &'address verification'&. Verification can be requested as
1265 one of the checks to be performed in an ACL for incoming messages, on both
1266 sender and recipient addresses, and it can be tested using the &%-bv%& and
1267 &%-bvs%& command line options.
1269 When an address is being verified, the routers are run in &"verify mode"&. This
1270 does not affect the way the routers work, but it is a state that can be
1271 detected. By this means, a router can be skipped or made to behave differently
1272 when verifying. A common example is a configuration in which the first router
1273 sends all messages to a message-scanning program, unless they have been
1274 previously scanned. Thus, the first router accepts all addresses without any
1275 checking, making it useless for verifying. Normally, the &%no_verify%& option
1276 would be set for such a router, causing it to be skipped in verify mode.
1281 .section "Running an individual router" "SECTrunindrou"
1282 .cindex "router" "running details"
1283 .cindex "preconditions" "checking"
1284 .cindex "router" "result of running"
1285 As explained in the example above, a number of preconditions are checked before
1286 running a router. If any are not met, the router is skipped, and the address is
1287 passed to the next router. When all the preconditions on a router &'are'& met,
1288 the router is run. What happens next depends on the outcome, which is one of
1292 &'accept'&: The router accepts the address, and either assigns it to a
1293 transport, or generates one or more &"child"& addresses. Processing the
1294 original address ceases,
1295 .oindex "&%unseen%&"
1296 unless the &%unseen%& option is set on the router. This option
1297 can be used to set up multiple deliveries with different routing (for example,
1298 for keeping archive copies of messages). When &%unseen%& is set, the address is
1299 passed to the next router. Normally, however, an &'accept'& return marks the
1302 Any child addresses generated by the router are processed independently,
1303 starting with the first router by default. It is possible to change this by
1304 setting the &%redirect_router%& option to specify which router to start at for
1305 child addresses. Unlike &%pass_router%& (see below) the router specified by
1306 &%redirect_router%& may be anywhere in the router configuration.
1308 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1309 requests that the address be passed to another router. By default the address
1310 is passed to the next router, but this can be changed by setting the
1311 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1312 must be below the current router (to avoid loops).
1314 &'decline'&: The router declines to accept the address because it does not
1315 recognize it at all. By default, the address is passed to the next router, but
1316 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1317 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1318 &'decline'& into &'fail'&.
1320 &'fail'&: The router determines that the address should fail, and queues it for
1321 the generation of a bounce message. There is no further processing of the
1322 original address unless &%unseen%& is set on the router.
1324 &'defer'&: The router cannot handle the address at the present time. (A
1325 database may be offline, or a DNS lookup may have timed out.) No further
1326 processing of the address happens in this delivery attempt. It is tried again
1327 next time the message is considered for delivery.
1329 &'error'&: There is some error in the router (for example, a syntax error in
1330 its configuration). The action is as for defer.
1333 If an address reaches the end of the routers without having been accepted by
1334 any of them, it is bounced as unrouteable. The default error message in this
1335 situation is &"unrouteable address"&, but you can set your own message by
1336 making use of the &%cannot_route_message%& option. This can be set for any
1337 router; the value from the last router that &"saw"& the address is used.
1339 Sometimes while routing you want to fail a delivery when some conditions are
1340 met but others are not, instead of passing the address on for further routing.
1341 You can do this by having a second router that explicitly fails the delivery
1342 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1343 facility for this purpose.
1346 .section "Duplicate addresses" "SECID17"
1347 .cindex "case of local parts"
1348 .cindex "address duplicate, discarding"
1349 .cindex "duplicate addresses"
1350 Once routing is complete, Exim scans the addresses that are assigned to local
1351 and remote transports, and discards any duplicates that it finds. During this
1352 check, local parts are treated as case-sensitive. This happens only when
1353 actually delivering a message; when testing routers with &%-bt%&, all the
1354 routed addresses are shown.
1358 .section "Router preconditions" "SECTrouprecon"
1359 .cindex "router" "preconditions, order of processing"
1360 .cindex "preconditions" "order of processing"
1361 The preconditions that are tested for each router are listed below, in the
1362 order in which they are tested. The individual configuration options are
1363 described in more detail in chapter &<<CHAProutergeneric>>&.
1366 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1367 the local parts handled by the router may or must have certain prefixes and/or
1368 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1369 skipped. These conditions are tested first. When an affix is present, it is
1370 removed from the local part before further processing, including the evaluation
1371 of any other conditions.
1373 Routers can be designated for use only when not verifying an address, that is,
1374 only when routing it for delivery (or testing its delivery routing). If the
1375 &%verify%& option is set false, the router is skipped when Exim is verifying an
1377 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1378 &%verify_recipient%&, which independently control the use of the router for
1379 sender and recipient verification. You can set these options directly if
1380 you want a router to be used for only one type of verification.
1381 Note that cutthrough delivery is classed as a recipient verification for this purpose.
1383 If the &%address_test%& option is set false, the router is skipped when Exim is
1384 run with the &%-bt%& option to test an address routing. This can be helpful
1385 when the first router sends all new messages to a scanner of some sort; it
1386 makes it possible to use &%-bt%& to test subsequent delivery routing without
1387 having to simulate the effect of the scanner.
1389 Routers can be designated for use only when verifying an address, as
1390 opposed to routing it for delivery. The &%verify_only%& option controls this.
1391 Again, cutthrough delivery counts as a verification.
1393 Individual routers can be explicitly skipped when running the routers to
1394 check an address given in the SMTP EXPN command (see the &%expn%& option).
1396 If the &%domains%& option is set, the domain of the address must be in the set
1397 of domains that it defines.
1399 .vindex "&$local_part_prefix$&"
1400 .vindex "&$local_part$&"
1401 .vindex "&$local_part_suffix$&"
1402 If the &%local_parts%& option is set, the local part of the address must be in
1403 the set of local parts that it defines. If &%local_part_prefix%& or
1404 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1405 part before this check. If you want to do precondition tests on local parts
1406 that include affixes, you can do so by using a &%condition%& option (see below)
1407 that uses the variables &$local_part$&, &$local_part_prefix$&, and
1408 &$local_part_suffix$& as necessary.
1410 .vindex "&$local_user_uid$&"
1411 .vindex "&$local_user_gid$&"
1413 If the &%check_local_user%& option is set, the local part must be the name of
1414 an account on the local host. If this check succeeds, the uid and gid of the
1415 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1416 user's home directory is placed in &$home$&; these values can be used in the
1417 remaining preconditions.
1419 If the &%router_home_directory%& option is set, it is expanded at this point,
1420 because it overrides the value of &$home$&. If this expansion were left till
1421 later, the value of &$home$& as set by &%check_local_user%& would be used in
1422 subsequent tests. Having two different values of &$home$& in the same router
1423 could lead to confusion.
1425 If the &%senders%& option is set, the envelope sender address must be in the
1426 set of addresses that it defines.
1428 If the &%require_files%& option is set, the existence or non-existence of
1429 specified files is tested.
1431 .cindex "customizing" "precondition"
1432 If the &%condition%& option is set, it is evaluated and tested. This option
1433 uses an expanded string to allow you to set up your own custom preconditions.
1434 Expanded strings are described in chapter &<<CHAPexpand>>&.
1438 Note that &%require_files%& comes near the end of the list, so you cannot use
1439 it to check for the existence of a file in which to lookup up a domain, local
1440 part, or sender. However, as these options are all expanded, you can use the
1441 &%exists%& expansion condition to make such tests within each condition. The
1442 &%require_files%& option is intended for checking files that the router may be
1443 going to use internally, or which are needed by a specific transport (for
1444 example, &_.procmailrc_&).
1448 .section "Delivery in detail" "SECID18"
1449 .cindex "delivery" "in detail"
1450 When a message is to be delivered, the sequence of events is as follows:
1453 If a system-wide filter file is specified, the message is passed to it. The
1454 filter may add recipients to the message, replace the recipients, discard the
1455 message, cause a new message to be generated, or cause the message delivery to
1456 fail. The format of the system filter file is the same as for Exim user filter
1457 files, described in the separate document entitled &'Exim's interfaces to mail
1459 .cindex "Sieve filter" "not available for system filter"
1460 (&*Note*&: Sieve cannot be used for system filter files.)
1462 Some additional features are available in system filters &-- see chapter
1463 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1464 filter only once per delivery attempt, however many recipients it has. However,
1465 if there are several delivery attempts because one or more addresses could not
1466 be immediately delivered, the system filter is run each time. The filter
1467 condition &%first_delivery%& can be used to detect the first run of the system
1470 Each recipient address is offered to each configured router in turn, subject to
1471 its preconditions, until one is able to handle it. If no router can handle the
1472 address, that is, if they all decline, the address is failed. Because routers
1473 can be targeted at particular domains, several locally handled domains can be
1474 processed entirely independently of each other.
1476 .cindex "routing" "loops in"
1477 .cindex "loop" "while routing"
1478 A router that accepts an address may assign it to a local or a remote
1479 transport. However, the transport is not run at this time. Instead, the address
1480 is placed on a list for the particular transport, which will be run later.
1481 Alternatively, the router may generate one or more new addresses (typically
1482 from alias, forward, or filter files). New addresses are fed back into this
1483 process from the top, but in order to avoid loops, a router ignores any address
1484 which has an identically-named ancestor that was processed by itself.
1486 When all the routing has been done, addresses that have been successfully
1487 handled are passed to their assigned transports. When local transports are
1488 doing real local deliveries, they handle only one address at a time, but if a
1489 local transport is being used as a pseudo-remote transport (for example, to
1490 collect batched SMTP messages for transmission by some other means) multiple
1491 addresses can be handled. Remote transports can always handle more than one
1492 address at a time, but can be configured not to do so, or to restrict multiple
1493 addresses to the same domain.
1495 Each local delivery to a file or a pipe runs in a separate process under a
1496 non-privileged uid, and these deliveries are run one at a time. Remote
1497 deliveries also run in separate processes, normally under a uid that is private
1498 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1499 run in parallel. The maximum number of simultaneous remote deliveries for any
1500 one message is set by the &%remote_max_parallel%& option.
1501 The order in which deliveries are done is not defined, except that all local
1502 deliveries happen before any remote deliveries.
1504 .cindex "queue runner"
1505 When it encounters a local delivery during a queue run, Exim checks its retry
1506 database to see if there has been a previous temporary delivery failure for the
1507 address before running the local transport. If there was a previous failure,
1508 Exim does not attempt a new delivery until the retry time for the address is
1509 reached. However, this happens only for delivery attempts that are part of a
1510 queue run. Local deliveries are always attempted when delivery immediately
1511 follows message reception, even if retry times are set for them. This makes for
1512 better behaviour if one particular message is causing problems (for example,
1513 causing quota overflow, or provoking an error in a filter file).
1515 .cindex "delivery" "retry in remote transports"
1516 Remote transports do their own retry handling, since an address may be
1517 deliverable to one of a number of hosts, each of which may have a different
1518 retry time. If there have been previous temporary failures and no host has
1519 reached its retry time, no delivery is attempted, whether in a queue run or
1520 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1522 If there were any permanent errors, a bounce message is returned to an
1523 appropriate address (the sender in the common case), with details of the error
1524 for each failing address. Exim can be configured to send copies of bounce
1525 messages to other addresses.
1527 .cindex "delivery" "deferral"
1528 If one or more addresses suffered a temporary failure, the message is left on
1529 the queue, to be tried again later. Delivery of these addresses is said to be
1532 When all the recipient addresses have either been delivered or bounced,
1533 handling of the message is complete. The spool files and message log are
1534 deleted, though the message log can optionally be preserved if required.
1540 .section "Retry mechanism" "SECID19"
1541 .cindex "delivery" "retry mechanism"
1542 .cindex "retry" "description of mechanism"
1543 .cindex "queue runner"
1544 Exim's mechanism for retrying messages that fail to get delivered at the first
1545 attempt is the queue runner process. You must either run an Exim daemon that
1546 uses the &%-q%& option with a time interval to start queue runners at regular
1547 intervals, or use some other means (such as &'cron'&) to start them. If you do
1548 not arrange for queue runners to be run, messages that fail temporarily at the
1549 first attempt will remain on your queue for ever. A queue runner process works
1550 its way through the queue, one message at a time, trying each delivery that has
1551 passed its retry time.
1552 You can run several queue runners at once.
1554 Exim uses a set of configured rules to determine when next to retry the failing
1555 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1556 should give up trying to deliver to the address, at which point it generates a
1557 bounce message. If no retry rules are set for a particular host, address, and
1558 error combination, no retries are attempted, and temporary errors are treated
1563 .section "Temporary delivery failure" "SECID20"
1564 .cindex "delivery" "temporary failure"
1565 There are many reasons why a message may not be immediately deliverable to a
1566 particular address. Failure to connect to a remote machine (because it, or the
1567 connection to it, is down) is one of the most common. Temporary failures may be
1568 detected during routing as well as during the transport stage of delivery.
1569 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1570 is on a file system where the user is over quota. Exim can be configured to
1571 impose its own quotas on local mailboxes; where system quotas are set they will
1574 If a host is unreachable for a period of time, a number of messages may be
1575 waiting for it by the time it recovers, and sending them in a single SMTP
1576 connection is clearly beneficial. Whenever a delivery to a remote host is
1578 .cindex "hints database" "deferred deliveries"
1579 Exim makes a note in its hints database, and whenever a successful
1580 SMTP delivery has happened, it looks to see if any other messages are waiting
1581 for the same host. If any are found, they are sent over the same SMTP
1582 connection, subject to a configuration limit as to the maximum number in any
1587 .section "Permanent delivery failure" "SECID21"
1588 .cindex "delivery" "permanent failure"
1589 .cindex "bounce message" "when generated"
1590 When a message cannot be delivered to some or all of its intended recipients, a
1591 bounce message is generated. Temporary delivery failures turn into permanent
1592 errors when their timeout expires. All the addresses that fail in a given
1593 delivery attempt are listed in a single message. If the original message has
1594 many recipients, it is possible for some addresses to fail in one delivery
1595 attempt and others to fail subsequently, giving rise to more than one bounce
1596 message. The wording of bounce messages can be customized by the administrator.
1597 See chapter &<<CHAPemsgcust>>& for details.
1599 .cindex "&'X-Failed-Recipients:'& header line"
1600 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1601 failed addresses, for the benefit of programs that try to analyse such messages
1604 .cindex "bounce message" "recipient of"
1605 A bounce message is normally sent to the sender of the original message, as
1606 obtained from the message's envelope. For incoming SMTP messages, this is the
1607 address given in the MAIL command. However, when an address is expanded via a
1608 forward or alias file, an alternative address can be specified for delivery
1609 failures of the generated addresses. For a mailing list expansion (see section
1610 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1615 .section "Failures to deliver bounce messages" "SECID22"
1616 .cindex "bounce message" "failure to deliver"
1617 If a bounce message (either locally generated or received from a remote host)
1618 itself suffers a permanent delivery failure, the message is left on the queue,
1619 but it is frozen, awaiting the attention of an administrator. There are options
1620 that can be used to make Exim discard such failed messages, or to keep them
1621 for only a short time (see &%timeout_frozen_after%& and
1622 &%ignore_bounce_errors_after%&).
1628 . ////////////////////////////////////////////////////////////////////////////
1629 . ////////////////////////////////////////////////////////////////////////////
1631 .chapter "Building and installing Exim" "CHID3"
1632 .scindex IIDbuex "building Exim"
1634 .section "Unpacking" "SECID23"
1635 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1636 creates a directory with the name of the current release (for example,
1637 &_exim-&version()_&) into which the following files are placed:
1640 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1641 .irow &_CHANGES_& "contains a reference to where changes are &&&
1643 .irow &_LICENCE_& "the GNU General Public Licence"
1644 .irow &_Makefile_& "top-level make file"
1645 .irow &_NOTICE_& "conditions for the use of Exim"
1646 .irow &_README_& "list of files, directories and simple build &&&
1650 Other files whose names begin with &_README_& may also be present. The
1651 following subdirectories are created:
1654 .irow &_Local_& "an empty directory for local configuration files"
1655 .irow &_OS_& "OS-specific files"
1656 .irow &_doc_& "documentation files"
1657 .irow &_exim_monitor_& "source files for the Exim monitor"
1658 .irow &_scripts_& "scripts used in the build process"
1659 .irow &_src_& "remaining source files"
1660 .irow &_util_& "independent utilities"
1663 The main utility programs are contained in the &_src_& directory, and are built
1664 with the Exim binary. The &_util_& directory contains a few optional scripts
1665 that may be useful to some sites.
1668 .section "Multiple machine architectures and operating systems" "SECID24"
1669 .cindex "building Exim" "multiple OS/architectures"
1670 The building process for Exim is arranged to make it easy to build binaries for
1671 a number of different architectures and operating systems from the same set of
1672 source files. Compilation does not take place in the &_src_& directory.
1673 Instead, a &'build directory'& is created for each architecture and operating
1675 .cindex "symbolic link" "to build directory"
1676 Symbolic links to the sources are installed in this directory, which is where
1677 the actual building takes place. In most cases, Exim can discover the machine
1678 architecture and operating system for itself, but the defaults can be
1679 overridden if necessary.
1682 .section "PCRE library" "SECTpcre"
1683 .cindex "PCRE library"
1684 Exim no longer has an embedded PCRE library as the vast majority of
1685 modern systems include PCRE as a system library, although you may need
1686 to install the PCRE or PCRE development package for your operating
1687 system. If your system has a normal PCRE installation the Exim build
1688 process will need no further configuration. If the library or the
1689 headers are in an unusual location you will need to either set the PCRE_LIBS
1690 and INCLUDE directives appropriately,
1691 or set PCRE_CONFIG=yes to use the installed &(pcre-config)& command.
1692 If your operating system has no
1693 PCRE support then you will need to obtain and build the current PCRE
1694 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
1695 More information on PCRE is available at &url(http://www.pcre.org/).
1697 .section "DBM libraries" "SECTdb"
1698 .cindex "DBM libraries" "discussion of"
1699 .cindex "hints database" "DBM files used for"
1700 Even if you do not use any DBM files in your configuration, Exim still needs a
1701 DBM library in order to operate, because it uses indexed files for its hints
1702 databases. Unfortunately, there are a number of DBM libraries in existence, and
1703 different operating systems often have different ones installed.
1705 .cindex "Solaris" "DBM library for"
1706 .cindex "IRIX, DBM library for"
1707 .cindex "BSD, DBM library for"
1708 .cindex "Linux, DBM library for"
1709 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1710 Linux distribution, the DBM configuration should happen automatically, and you
1711 may be able to ignore this section. Otherwise, you may have to learn more than
1712 you would like about DBM libraries from what follows.
1714 .cindex "&'ndbm'& DBM library"
1715 Licensed versions of Unix normally contain a library of DBM functions operating
1716 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1717 versions of Unix seem to vary in what they contain as standard. In particular,
1718 some early versions of Linux have no default DBM library, and different
1719 distributors have chosen to bundle different libraries with their packaged
1720 versions. However, the more recent releases seem to have standardized on the
1721 Berkeley DB library.
1723 Different DBM libraries have different conventions for naming the files they
1724 use. When a program opens a file called &_dbmfile_&, there are several
1728 A traditional &'ndbm'& implementation, such as that supplied as part of
1729 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1731 .cindex "&'gdbm'& DBM library"
1732 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1733 compatibility interface it makes two different hard links to it with names
1734 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1735 file name is used unmodified.
1737 .cindex "Berkeley DB library"
1738 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1739 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1740 programmer exactly the same as the traditional &'ndbm'& implementation.
1742 If the Berkeley package is used in its native mode, it operates on a single
1743 file called &_dbmfile_&; the programmer's interface is somewhat different to
1744 the traditional &'ndbm'& interface.
1746 To complicate things further, there are several very different versions of the
1747 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1748 2.&'x'& and 3.&'x'& were current for a while, but the latest versions are now
1749 numbered 4.&'x'&. Maintenance of some of the earlier releases has ceased. All
1750 versions of Berkeley DB can be obtained from
1751 &url(http://www.sleepycat.com/).
1753 .cindex "&'tdb'& DBM library"
1754 Yet another DBM library, called &'tdb'&, is available from
1755 &url(http://download.sourceforge.net/tdb). It has its own interface, and also
1756 operates on a single file.
1760 .cindex "DBM libraries" "configuration for building"
1761 Exim and its utilities can be compiled to use any of these interfaces. In order
1762 to use any version of the Berkeley DB package in native mode, you must set
1763 USE_DB in an appropriate configuration file (typically
1764 &_Local/Makefile_&). For example:
1768 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1769 error is diagnosed if you set more than one of these.
1771 At the lowest level, the build-time configuration sets none of these options,
1772 thereby assuming an interface of type (1). However, some operating system
1773 configuration files (for example, those for the BSD operating systems and
1774 Linux) assume type (4) by setting USE_DB as their default, and the
1775 configuration files for Cygwin set USE_GDBM. Anything you set in
1776 &_Local/Makefile_&, however, overrides these system defaults.
1778 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1779 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1780 in one of these lines:
1785 Settings like that will work if the DBM library is installed in the standard
1786 place. Sometimes it is not, and the library's header file may also not be in
1787 the default path. You may need to set INCLUDE to specify where the header
1788 file is, and to specify the path to the library more fully in DBMLIB, as in
1791 INCLUDE=-I/usr/local/include/db-4.1
1792 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1794 There is further detailed discussion about the various DBM libraries in the
1795 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1799 .section "Pre-building configuration" "SECID25"
1800 .cindex "building Exim" "pre-building configuration"
1801 .cindex "configuration for building Exim"
1802 .cindex "&_Local/Makefile_&"
1803 .cindex "&_src/EDITME_&"
1804 Before building Exim, a local configuration file that specifies options
1805 independent of any operating system has to be created with the name
1806 &_Local/Makefile_&. A template for this file is supplied as the file
1807 &_src/EDITME_&, and it contains full descriptions of all the option settings
1808 therein. These descriptions are therefore not repeated here. If you are
1809 building Exim for the first time, the simplest thing to do is to copy
1810 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1812 There are three settings that you must supply, because Exim will not build
1813 without them. They are the location of the run time configuration file
1814 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1815 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1816 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1817 a colon-separated list of file names; Exim uses the first of them that exists.
1819 There are a few other parameters that can be specified either at build time or
1820 at run time, to enable the same binary to be used on a number of different
1821 machines. However, if the locations of Exim's spool directory and log file
1822 directory (if not within the spool directory) are fixed, it is recommended that
1823 you specify them in &_Local/Makefile_& instead of at run time, so that errors
1824 detected early in Exim's execution (such as a malformed configuration file) can
1827 .cindex "content scanning" "specifying at build time"
1828 Exim's interfaces for calling virus and spam scanning software directly from
1829 access control lists are not compiled by default. If you want to include these
1830 facilities, you need to set
1832 WITH_CONTENT_SCAN=yes
1834 in your &_Local/Makefile_&. For details of the facilities themselves, see
1835 chapter &<<CHAPexiscan>>&.
1838 .cindex "&_Local/eximon.conf_&"
1839 .cindex "&_exim_monitor/EDITME_&"
1840 If you are going to build the Exim monitor, a similar configuration process is
1841 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1842 your installation and saved under the name &_Local/eximon.conf_&. If you are
1843 happy with the default settings described in &_exim_monitor/EDITME_&,
1844 &_Local/eximon.conf_& can be empty, but it must exist.
1846 This is all the configuration that is needed in straightforward cases for known
1847 operating systems. However, the building process is set up so that it is easy
1848 to override options that are set by default or by operating-system-specific
1849 configuration files, for example to change the name of the C compiler, which
1850 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1855 .section "Support for iconv()" "SECID26"
1856 .cindex "&[iconv()]& support"
1858 The contents of header lines in messages may be encoded according to the rules
1859 described RFC 2047. This makes it possible to transmit characters that are not
1860 in the ASCII character set, and to label them as being in a particular
1861 character set. When Exim is inspecting header lines by means of the &%$h_%&
1862 mechanism, it decodes them, and translates them into a specified character set
1863 (default ISO-8859-1). The translation is possible only if the operating system
1864 supports the &[iconv()]& function.
1866 However, some of the operating systems that supply &[iconv()]& do not support
1867 very many conversions. The GNU &%libiconv%& library (available from
1868 &url(http://www.gnu.org/software/libiconv/)) can be installed on such
1869 systems to remedy this deficiency, as well as on systems that do not supply
1870 &[iconv()]& at all. After installing &%libiconv%&, you should add
1874 to your &_Local/Makefile_& and rebuild Exim.
1878 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1879 .cindex "TLS" "including support for TLS"
1880 .cindex "encryption" "including support for"
1881 .cindex "SUPPORT_TLS"
1882 .cindex "OpenSSL" "building Exim with"
1883 .cindex "GnuTLS" "building Exim with"
1884 Exim can be built to support encrypted SMTP connections, using the STARTTLS
1885 command as per RFC 2487. It can also support legacy clients that expect to
1886 start a TLS session immediately on connection to a non-standard port (see the
1887 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1890 If you want to build Exim with TLS support, you must first install either the
1891 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1894 If OpenSSL is installed, you should set
1897 TLS_LIBS=-lssl -lcrypto
1899 in &_Local/Makefile_&. You may also need to specify the locations of the
1900 OpenSSL library and include files. For example:
1903 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1904 TLS_INCLUDE=-I/usr/local/openssl/include/
1906 .cindex "pkg-config" "OpenSSL"
1907 If you have &'pkg-config'& available, then instead you can just use:
1910 USE_OPENSSL_PC=openssl
1912 .cindex "USE_GNUTLS"
1913 If GnuTLS is installed, you should set
1917 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1919 in &_Local/Makefile_&, and again you may need to specify the locations of the
1920 library and include files. For example:
1924 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1925 TLS_INCLUDE=-I/usr/gnu/include
1927 .cindex "pkg-config" "GnuTLS"
1928 If you have &'pkg-config'& available, then instead you can just use:
1932 USE_GNUTLS_PC=gnutls
1935 You do not need to set TLS_INCLUDE if the relevant directory is already
1936 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1937 given in chapter &<<CHAPTLS>>&.
1942 .section "Use of tcpwrappers" "SECID27"
1944 .cindex "tcpwrappers, building Exim to support"
1945 .cindex "USE_TCP_WRAPPERS"
1946 .cindex "TCP_WRAPPERS_DAEMON_NAME"
1947 .cindex "tcp_wrappers_daemon_name"
1948 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
1949 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
1950 alternative to Exim's own checking facilities for installations that are
1951 already making use of &'tcpwrappers'& for other purposes. To do this, you
1952 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
1953 &_tcpd.h_& to be available at compile time, and also ensure that the library
1954 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
1955 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
1958 USE_TCP_WRAPPERS=yes
1959 CFLAGS=-O -I/usr/local/include
1960 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
1962 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
1963 files is &"exim"&. For example, the line
1965 exim : LOCAL 192.168.1. .friendly.domain.example
1967 in your &_/etc/hosts.allow_& file allows connections from the local host, from
1968 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
1969 All other connections are denied. The daemon name used by &'tcpwrappers'&
1970 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
1971 &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
1972 configure file. Consult the &'tcpwrappers'& documentation for
1976 .section "Including support for IPv6" "SECID28"
1977 .cindex "IPv6" "including support for"
1978 Exim contains code for use on systems that have IPv6 support. Setting
1979 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
1980 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
1981 where the IPv6 support is not fully integrated into the normal include and
1984 Two different types of DNS record for handling IPv6 addresses have been
1985 defined. AAAA records (analogous to A records for IPv4) are in use, and are
1986 currently seen as the mainstream. Another record type called A6 was proposed
1987 as better than AAAA because it had more flexibility. However, it was felt to be
1988 over-complex, and its status was reduced to &"experimental"&.
1990 have a compile option for including A6 record support but this has now been
1995 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
1996 .cindex "lookup modules"
1997 .cindex "dynamic modules"
1998 .cindex ".so building"
1999 On some platforms, Exim supports not compiling all lookup types directly into
2000 the main binary, instead putting some into external modules which can be loaded
2002 This permits packagers to build Exim with support for lookups with extensive
2003 library dependencies without requiring all users to install all of those
2005 Most, but not all, lookup types can be built this way.
2007 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2008 installed; Exim will only load modules from that directory, as a security
2009 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2010 for your OS; see &_OS/Makefile-Linux_& for an example.
2011 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2012 see &_src/EDITME_& for details.
2014 Then, for each module to be loaded dynamically, define the relevant
2015 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2016 For example, this will build in lsearch but load sqlite and mysql support
2025 .section "The building process" "SECID29"
2026 .cindex "build directory"
2027 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2028 created, run &'make'& at the top level. It determines the architecture and
2029 operating system types, and creates a build directory if one does not exist.
2030 For example, on a Sun system running Solaris 8, the directory
2031 &_build-SunOS5-5.8-sparc_& is created.
2032 .cindex "symbolic link" "to source files"
2033 Symbolic links to relevant source files are installed in the build directory.
2035 If this is the first time &'make'& has been run, it calls a script that builds
2036 a make file inside the build directory, using the configuration files from the
2037 &_Local_& directory. The new make file is then passed to another instance of
2038 &'make'&. This does the real work, building a number of utility scripts, and
2039 then compiling and linking the binaries for the Exim monitor (if configured), a
2040 number of utility programs, and finally Exim itself. The command &`make
2041 makefile`& can be used to force a rebuild of the make file in the build
2042 directory, should this ever be necessary.
2044 If you have problems building Exim, check for any comments there may be in the
2045 &_README_& file concerning your operating system, and also take a look at the
2046 FAQ, where some common problems are covered.
2050 .section 'Output from &"make"&' "SECID283"
2051 The output produced by the &'make'& process for compile lines is often very
2052 unreadable, because these lines can be very long. For this reason, the normal
2053 output is suppressed by default, and instead output similar to that which
2054 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2055 each module that is being compiled or linked. However, it is still possible to
2056 get the full output, by calling &'make'& like this:
2060 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2061 command reflection in &'make'&. When you ask for the full output, it is
2062 given in addition to the short output.
2066 .section "Overriding build-time options for Exim" "SECToverride"
2067 .cindex "build-time options, overriding"
2068 The main make file that is created at the beginning of the building process
2069 consists of the concatenation of a number of files which set configuration
2070 values, followed by a fixed set of &'make'& instructions. If a value is set
2071 more than once, the last setting overrides any previous ones. This provides a
2072 convenient way of overriding defaults. The files that are concatenated are, in
2075 &_OS/Makefile-Default_&
2076 &_OS/Makefile-_&<&'ostype'&>
2078 &_Local/Makefile-_&<&'ostype'&>
2079 &_Local/Makefile-_&<&'archtype'&>
2080 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2081 &_OS/Makefile-Base_&
2083 .cindex "&_Local/Makefile_&"
2084 .cindex "building Exim" "operating system type"
2085 .cindex "building Exim" "architecture type"
2086 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2087 architecture type. &_Local/Makefile_& is required to exist, and the building
2088 process fails if it is absent. The other three &_Local_& files are optional,
2089 and are often not needed.
2091 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2092 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2093 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2094 values are used, thereby providing a means of forcing particular settings.
2095 Otherwise, the scripts try to get values from the &%uname%& command. If this
2096 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2097 of &'ad hoc'& transformations are then applied, to produce the standard names
2098 that Exim expects. You can run these scripts directly from the shell in order
2099 to find out what values are being used on your system.
2102 &_OS/Makefile-Default_& contains comments about the variables that are set
2103 therein. Some (but not all) are mentioned below. If there is something that
2104 needs changing, review the contents of this file and the contents of the make
2105 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2109 .cindex "building Exim" "overriding default settings"
2110 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2111 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2112 need to change the original files. Instead, you should make the changes by
2113 putting the new values in an appropriate &_Local_& file. For example,
2114 .cindex "Tru64-Unix build-time settings"
2115 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2116 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2117 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2118 called with the option &%-std1%&, to make it recognize some of the features of
2119 Standard C that Exim uses. (Most other compilers recognize Standard C by
2120 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2121 containing the lines
2126 If you are compiling for just one operating system, it may be easier to put
2127 these lines directly into &_Local/Makefile_&.
2129 Keeping all your local configuration settings separate from the distributed
2130 files makes it easy to transfer them to new versions of Exim simply by copying
2131 the contents of the &_Local_& directory.
2134 .cindex "NIS lookup type" "including support for"
2135 .cindex "NIS+ lookup type" "including support for"
2136 .cindex "LDAP" "including support for"
2137 .cindex "lookup" "inclusion in binary"
2138 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2139 lookup, but not all systems have these components installed, so the default is
2140 not to include the relevant code in the binary. All the different kinds of file
2141 and database lookup that Exim supports are implemented as separate code modules
2142 which are included only if the relevant compile-time options are set. In the
2143 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2149 and similar settings apply to the other lookup types. They are all listed in
2150 &_src/EDITME_&. In many cases the relevant include files and interface
2151 libraries need to be installed before compiling Exim.
2152 .cindex "cdb" "including support for"
2153 However, there are some optional lookup types (such as cdb) for which
2154 the code is entirely contained within Exim, and no external include
2155 files or libraries are required. When a lookup type is not included in the
2156 binary, attempts to configure Exim to use it cause run time configuration
2159 .cindex "pkg-config" "lookups"
2160 .cindex "pkg-config" "authenticators"
2161 Many systems now use a tool called &'pkg-config'& to encapsulate information
2162 about how to compile against a library; Exim has some initial support for
2163 being able to use pkg-config for lookups and authenticators. For any given
2164 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2165 variable with the &`_PC`& suffix in the name and assign as the value the
2166 name of the package to be queried. The results of querying via the
2167 &'pkg-config'& command will be added to the appropriate Makefile variables
2168 with &`+=`& directives, so your version of &'make'& will need to support that
2169 syntax. For instance:
2172 LOOKUP_SQLITE_PC=sqlite3
2174 AUTH_GSASL_PC=libgsasl
2175 AUTH_HEIMDAL_GSSAPI=yes
2176 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2179 .cindex "Perl" "including support for"
2180 Exim can be linked with an embedded Perl interpreter, allowing Perl
2181 subroutines to be called during string expansion. To enable this facility,
2185 must be defined in &_Local/Makefile_&. Details of this facility are given in
2186 chapter &<<CHAPperl>>&.
2188 .cindex "X11 libraries, location of"
2189 The location of the X11 libraries is something that varies a lot between
2190 operating systems, and there may be different versions of X11 to cope
2191 with. Exim itself makes no use of X11, but if you are compiling the Exim
2192 monitor, the X11 libraries must be available.
2193 The following three variables are set in &_OS/Makefile-Default_&:
2196 XINCLUDE=-I$(X11)/include
2197 XLFLAGS=-L$(X11)/lib
2199 These are overridden in some of the operating-system configuration files. For
2200 example, in &_OS/Makefile-SunOS5_& there is
2203 XINCLUDE=-I$(X11)/include
2204 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2206 If you need to override the default setting for your operating system, place a
2207 definition of all three of these variables into your
2208 &_Local/Makefile-<ostype>_& file.
2211 If you need to add any extra libraries to the link steps, these can be put in a
2212 variable called EXTRALIBS, which appears in all the link commands, but by
2213 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2214 command for linking the main Exim binary, and not for any associated utilities.
2216 .cindex "DBM libraries" "configuration for building"
2217 There is also DBMLIB, which appears in the link commands for binaries that
2218 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2219 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2220 binary, and which can be used, for example, to include additional X11
2223 .cindex "configuration file" "editing"
2224 The make file copes with rebuilding Exim correctly if any of the configuration
2225 files are edited. However, if an optional configuration file is deleted, it is
2226 necessary to touch the associated non-optional file (that is,
2227 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2230 .section "OS-specific header files" "SECID30"
2232 .cindex "building Exim" "OS-specific C header files"
2233 The &_OS_& directory contains a number of files with names of the form
2234 &_os.h-<ostype>_&. These are system-specific C header files that should not
2235 normally need to be changed. There is a list of macro settings that are
2236 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2237 are porting Exim to a new operating system.
2241 .section "Overriding build-time options for the monitor" "SECID31"
2242 .cindex "building Eximon"
2243 A similar process is used for overriding things when building the Exim monitor,
2244 where the files that are involved are
2246 &_OS/eximon.conf-Default_&
2247 &_OS/eximon.conf-_&<&'ostype'&>
2248 &_Local/eximon.conf_&
2249 &_Local/eximon.conf-_&<&'ostype'&>
2250 &_Local/eximon.conf-_&<&'archtype'&>
2251 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2253 .cindex "&_Local/eximon.conf_&"
2254 As with Exim itself, the final three files need not exist, and in this case the
2255 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2256 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2257 variables of the same name, preceded by EXIMON_. For example, setting
2258 EXIMON_LOG_DEPTH in the environment overrides the value of
2259 LOG_DEPTH at run time.
2263 .section "Installing Exim binaries and scripts" "SECID32"
2264 .cindex "installing Exim"
2265 .cindex "BIN_DIRECTORY"
2266 The command &`make install`& runs the &(exim_install)& script with no
2267 arguments. The script copies binaries and utility scripts into the directory
2268 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2269 .cindex "setuid" "installing Exim with"
2270 The install script copies files only if they are newer than the files they are
2271 going to replace. The Exim binary is required to be owned by root and have the
2272 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2273 install`& as root so that it can set up the Exim binary in this way. However, in
2274 some special situations (for example, if a host is doing no local deliveries)
2275 it may be possible to run Exim without making the binary setuid root (see
2276 chapter &<<CHAPsecurity>>& for details).
2278 .cindex "CONFIGURE_FILE"
2279 Exim's run time configuration file is named by the CONFIGURE_FILE setting
2280 in &_Local/Makefile_&. If this names a single file, and the file does not
2281 exist, the default configuration file &_src/configure.default_& is copied there
2282 by the installation script. If a run time configuration file already exists, it
2283 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2284 alternative files, no default is installed.
2286 .cindex "system aliases file"
2287 .cindex "&_/etc/aliases_&"
2288 One change is made to the default configuration file when it is installed: the
2289 default configuration contains a router that references a system aliases file.
2290 The path to this file is set to the value specified by
2291 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2292 If the system aliases file does not exist, the installation script creates it,
2293 and outputs a comment to the user.
2295 The created file contains no aliases, but it does contain comments about the
2296 aliases a site should normally have. Mail aliases have traditionally been
2297 kept in &_/etc/aliases_&. However, some operating systems are now using
2298 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2299 Exim's configuration if necessary.
2301 The default configuration uses the local host's name as the only local domain,
2302 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2303 running as the local user. System aliases and &_.forward_& files in users' home
2304 directories are supported, but no NIS or NIS+ support is configured. Domains
2305 other than the name of the local host are routed using the DNS, with delivery
2308 It is possible to install Exim for special purposes (such as building a binary
2309 distribution) in a private part of the file system. You can do this by a
2312 make DESTDIR=/some/directory/ install
2314 This has the effect of pre-pending the specified directory to all the file
2315 paths, except the name of the system aliases file that appears in the default
2316 configuration. (If a default alias file is created, its name &'is'& modified.)
2317 For backwards compatibility, ROOT is used if DESTDIR is not set,
2318 but this usage is deprecated.
2320 .cindex "installing Exim" "what is not installed"
2321 Running &'make install'& does not copy the Exim 4 conversion script
2322 &'convert4r4'&. You will probably run this only once if you are
2323 upgrading from Exim 3. None of the documentation files in the &_doc_&
2324 directory are copied, except for the info files when you have set
2325 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2327 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2328 to their names. The Exim binary itself, however, is handled differently. It is
2329 installed under a name that includes the version number and the compile number,
2330 for example &_exim-&version()-1_&. The script then arranges for a symbolic link
2331 called &_exim_& to point to the binary. If you are updating a previous version
2332 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2333 from the directory (as seen by other processes).
2335 .cindex "installing Exim" "testing the script"
2336 If you want to see what the &'make install'& will do before running it for
2337 real, you can pass the &%-n%& option to the installation script by this
2340 make INSTALL_ARG=-n install
2342 The contents of the variable INSTALL_ARG are passed to the installation
2343 script. You do not need to be root to run this test. Alternatively, you can run
2344 the installation script directly, but this must be from within the build
2345 directory. For example, from the top-level Exim directory you could use this
2348 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2350 .cindex "installing Exim" "install script options"
2351 There are two other options that can be supplied to the installation script.
2354 &%-no_chown%& bypasses the call to change the owner of the installed binary
2355 to root, and the call to make it a setuid binary.
2357 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2361 INSTALL_ARG can be used to pass these options to the script. For example:
2363 make INSTALL_ARG=-no_symlink install
2365 The installation script can also be given arguments specifying which files are
2366 to be copied. For example, to install just the Exim binary, and nothing else,
2367 without creating the symbolic link, you could use:
2369 make INSTALL_ARG='-no_symlink exim' install
2374 .section "Installing info documentation" "SECTinsinfdoc"
2375 .cindex "installing Exim" "&'info'& documentation"
2376 Not all systems use the GNU &'info'& system for documentation, and for this
2377 reason, the Texinfo source of Exim's documentation is not included in the main
2378 distribution. Instead it is available separately from the ftp site (see section
2381 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2382 source of the documentation is found in the source tree, running &`make
2383 install`& automatically builds the info files and installs them.
2387 .section "Setting up the spool directory" "SECID33"
2388 .cindex "spool directory" "creating"
2389 When it starts up, Exim tries to create its spool directory if it does not
2390 exist. The Exim uid and gid are used for the owner and group of the spool
2391 directory. Sub-directories are automatically created in the spool directory as
2397 .section "Testing" "SECID34"
2398 .cindex "testing" "installation"
2399 Having installed Exim, you can check that the run time configuration file is
2400 syntactically valid by running the following command, which assumes that the
2401 Exim binary directory is within your PATH environment variable:
2405 If there are any errors in the configuration file, Exim outputs error messages.
2406 Otherwise it outputs the version number and build date,
2407 the DBM library that is being used, and information about which drivers and
2408 other optional code modules are included in the binary.
2409 Some simple routing tests can be done by using the address testing option. For
2412 &`exim -bt`& <&'local username'&>
2414 should verify that it recognizes a local mailbox, and
2416 &`exim -bt`& <&'remote address'&>
2418 a remote one. Then try getting it to deliver mail, both locally and remotely.
2419 This can be done by passing messages directly to Exim, without going through a
2420 user agent. For example:
2422 exim -v postmaster@your.domain.example
2423 From: user@your.domain.example
2424 To: postmaster@your.domain.example
2425 Subject: Testing Exim
2427 This is a test message.
2430 The &%-v%& option causes Exim to output some verification of what it is doing.
2431 In this case you should see copies of three log lines, one for the message's
2432 arrival, one for its delivery, and one containing &"Completed"&.
2434 .cindex "delivery" "problems with"
2435 If you encounter problems, look at Exim's log files (&'mainlog'& and
2436 &'paniclog'&) to see if there is any relevant information there. Another source
2437 of information is running Exim with debugging turned on, by specifying the
2438 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2439 with debugging turned on by a command of the form
2441 &`exim -d -M`& <&'exim-message-id'&>
2443 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2444 produces rather a lot of output, but you can cut this down to specific areas.
2445 For example, if you use &%-d-all+route%& only the debugging information
2446 relevant to routing is included. (See the &%-d%& option in chapter
2447 &<<CHAPcommandline>>& for more details.)
2449 .cindex '&"sticky"& bit'
2450 .cindex "lock files"
2451 One specific problem that has shown up on some sites is the inability to do
2452 local deliveries into a shared mailbox directory, because it does not have the
2453 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2454 writing to a mailbox file, and if it cannot create the lock file, the delivery
2455 is deferred. You can get round this either by setting the &"sticky bit"& on the
2456 directory, or by setting a specific group for local deliveries and allowing
2457 that group to create files in the directory (see the comments above the
2458 &(local_delivery)& transport in the default configuration file). Another
2459 approach is to configure Exim not to use lock files, but just to rely on
2460 &[fcntl()]& locking instead. However, you should do this only if all user
2461 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2462 see chapter &<<CHAPappendfile>>&.
2464 One thing that cannot be tested on a system that is already running an MTA is
2465 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2466 &%-oX%& option can be used to run an Exim daemon that listens on some other
2467 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2468 &'exim_checkaccess'& utility can be used to check out policy controls on
2471 Testing a new version on a system that is already running Exim can most easily
2472 be done by building a binary with a different CONFIGURE_FILE setting. From
2473 within the run time configuration, all other file and directory names
2474 that Exim uses can be altered, in order to keep it entirely clear of the
2478 .section "Replacing another MTA with Exim" "SECID35"
2479 .cindex "replacing another MTA"
2480 Building and installing Exim for the first time does not of itself put it in
2481 general use. The name by which the system's MTA is called by mail user agents
2482 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2483 operating system), and it is necessary to make this name point to the &'exim'&
2484 binary in order to get the user agents to pass messages to Exim. This is
2485 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2486 or &_/usr/lib/sendmail_&
2487 .cindex "symbolic link" "to &'exim'& binary"
2488 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2489 privilege and executable status from the old MTA. It is then necessary to stop
2490 and restart the mailer daemon, if one is running.
2492 .cindex "FreeBSD, MTA indirection"
2493 .cindex "&_/etc/mail/mailer.conf_&"
2494 Some operating systems have introduced alternative ways of switching MTAs. For
2495 example, if you are running FreeBSD, you need to edit the file
2496 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2497 described. A typical example of the contents of this file for running Exim is
2500 sendmail /usr/exim/bin/exim
2501 send-mail /usr/exim/bin/exim
2502 mailq /usr/exim/bin/exim -bp
2503 newaliases /usr/bin/true
2505 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2506 your Exim installation is &"live"&. Check it by sending a message from your
2507 favourite user agent.
2509 You should consider what to tell your users about the change of MTA. Exim may
2510 have different capabilities to what was previously running, and there are
2511 various operational differences such as the text of messages produced by
2512 command line options and in bounce messages. If you allow your users to make
2513 use of Exim's filtering capabilities, you should make the document entitled
2514 &'Exim's interface to mail filtering'& available to them.
2518 .section "Upgrading Exim" "SECID36"
2519 .cindex "upgrading Exim"
2520 If you are already running Exim on your host, building and installing a new
2521 version automatically makes it available to MUAs, or any other programs that
2522 call the MTA directly. However, if you are running an Exim daemon, you do need
2523 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2524 new binary. You do not need to stop processing mail in order to install a new
2525 version of Exim. The install script does not modify an existing runtime
2531 .section "Stopping the Exim daemon on Solaris" "SECID37"
2532 .cindex "Solaris" "stopping Exim on"
2533 The standard command for stopping the mailer daemon on Solaris is
2535 /etc/init.d/sendmail stop
2537 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2538 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2539 for the text &"sendmail"&; this is not present because the actual program name
2540 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2541 solution is to replace the line that finds the process id with something like
2543 pid=`cat /var/spool/exim/exim-daemon.pid`
2545 to obtain the daemon's pid directly from the file that Exim saves it in.
2547 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2548 still be received from local processes, and if automatic delivery is configured
2549 (the normal case), deliveries will still occur.
2554 . ////////////////////////////////////////////////////////////////////////////
2555 . ////////////////////////////////////////////////////////////////////////////
2557 .chapter "The Exim command line" "CHAPcommandline"
2558 .scindex IIDclo1 "command line" "options"
2559 .scindex IIDclo2 "options" "command line"
2560 Exim's command line takes the standard Unix form of a sequence of options,
2561 each starting with a hyphen character, followed by a number of arguments. The
2562 options are compatible with the main options of Sendmail, and there are also
2563 some additional options, some of which are compatible with Smail 3. Certain
2564 combinations of options do not make sense, and provoke an error if used.
2565 The form of the arguments depends on which options are set.
2568 .section "Setting options by program name" "SECID38"
2570 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2571 were present before any other options.
2572 The &%-bp%& option requests a listing of the contents of the mail queue on the
2574 This feature is for compatibility with some systems that contain a command of
2575 that name in one of the standard libraries, symbolically linked to
2576 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2579 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2580 were present before any other options, for compatibility with Smail. The
2581 &%-bS%& option is used for reading in a number of messages in batched SMTP
2585 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2586 &%-oee%& options were present before any other options, for compatibility with
2587 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2590 .cindex "queue runner"
2591 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2592 were present before any other options, for compatibility with Smail. The &%-q%&
2593 option causes a single queue runner process to be started.
2595 .cindex "&'newaliases'&"
2596 .cindex "alias file" "building"
2597 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2598 If Exim is called under the name &'newaliases'& it behaves as if the option
2599 &%-bi%& were present before any other options, for compatibility with Sendmail.
2600 This option is used for rebuilding Sendmail's alias file. Exim does not have
2601 the concept of a single alias file, but can be configured to run a given
2602 command if called with the &%-bi%& option.
2605 .section "Trusted and admin users" "SECTtrustedadmin"
2606 Some Exim options are available only to &'trusted users'& and others are
2607 available only to &'admin users'&. In the description below, the phrases &"Exim
2608 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2609 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2610 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2613 .cindex "trusted users" "definition of"
2614 .cindex "user" "trusted definition of"
2615 The trusted users are root, the Exim user, any user listed in the
2616 &%trusted_users%& configuration option, and any user whose current group or any
2617 supplementary group is one of those listed in the &%trusted_groups%&
2618 configuration option. Note that the Exim group is not automatically trusted.
2620 .cindex '&"From"& line'
2621 .cindex "envelope sender"
2622 Trusted users are always permitted to use the &%-f%& option or a leading
2623 &"From&~"& line to specify the envelope sender of a message that is passed to
2624 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2625 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2626 users to set envelope senders.
2628 .cindex "&'From:'& header line"
2629 .cindex "&'Sender:'& header line"
2630 For a trusted user, there is never any check on the contents of the &'From:'&
2631 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2632 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2634 Trusted users may also specify a host name, host address, interface address,
2635 protocol name, ident value, and authentication data when submitting a message
2636 locally. Thus, they are able to insert messages into Exim's queue locally that
2637 have the characteristics of messages received from a remote host. Untrusted
2638 users may in some circumstances use &%-f%&, but can never set the other values
2639 that are available to trusted users.
2641 .cindex "user" "admin definition of"
2642 .cindex "admin user" "definition of"
2643 The admin users are root, the Exim user, and any user that is a member of the
2644 Exim group or of any group listed in the &%admin_groups%& configuration option.
2645 The current group does not have to be one of these groups.
2647 Admin users are permitted to list the queue, and to carry out certain
2648 operations on messages, for example, to force delivery failures. It is also
2649 necessary to be an admin user in order to see the full information provided by
2650 the Exim monitor, and full debugging output.
2652 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2653 Exim to attempt delivery of messages on its queue is restricted to admin users.
2654 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2655 option false (that is, specifying &%no_prod_requires_admin%&).
2657 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2658 is restricted to admin users unless &%queue_list_requires_admin%& is set
2663 &*Warning*&: If you configure your system so that admin users are able to
2664 edit Exim's configuration file, you are giving those users an easy way of
2665 getting root. There is further discussion of this issue at the start of chapter
2671 .section "Command line options" "SECID39"
2672 Exim's command line options are described in alphabetical order below. If none
2673 of the options that specifies a specific action (such as starting the daemon or
2674 a queue runner, or testing an address, or receiving a message in a specific
2675 format, or listing the queue) are present, and there is at least one argument
2676 on the command line, &%-bm%& (accept a local message on the standard input,
2677 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2678 outputs a brief message about itself and exits.
2680 . ////////////////////////////////////////////////////////////////////////////
2681 . Insert a stylized XML comment here, to identify the start of the command line
2682 . options. This is for the benefit of the Perl script that automatically
2683 . creates a man page for the options.
2684 . ////////////////////////////////////////////////////////////////////////////
2687 <!-- === Start of command line options === -->
2694 .cindex "options" "command line; terminating"
2695 This is a pseudo-option whose only purpose is to terminate the options and
2696 therefore to cause subsequent command line items to be treated as arguments
2697 rather than options, even if they begin with hyphens.
2700 .oindex "&%--help%&"
2701 This option causes Exim to output a few sentences stating what it is.
2702 The same output is generated if the Exim binary is called with no options and
2705 .vitem &%--version%&
2706 .oindex "&%--version%&"
2707 This option is an alias for &%-bV%& and causes version information to be
2714 These options are used by Sendmail for selecting configuration files and are
2717 .vitem &%-B%&<&'type'&>
2719 .cindex "8-bit characters"
2720 .cindex "Sendmail compatibility" "8-bit characters"
2721 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2722 clean; it ignores this option.
2727 .cindex "SMTP" "listener"
2728 .cindex "queue runner"
2729 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2730 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2731 that the daemon should also initiate periodic queue runs.
2733 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2734 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2735 disconnect from the controlling terminal. When running this way, it can be
2736 stopped by pressing ctrl-C.
2738 By default, Exim listens for incoming connections to the standard SMTP port on
2739 all the host's running interfaces. However, it is possible to listen on other
2740 ports, on multiple ports, and only on specific interfaces. Chapter
2741 &<<CHAPinterfaces>>& contains a description of the options that control this.
2743 When a listening daemon
2744 .cindex "daemon" "process id (pid)"
2745 .cindex "pid (process id)" "of daemon"
2746 is started without the use of &%-oX%& (that is, without overriding the normal
2747 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2748 in Exim's spool directory. This location can be overridden by setting
2749 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2752 When &%-oX%& is used on the command line to start a listening daemon, the
2753 process id is not written to the normal pid file path. However, &%-oP%& can be
2754 used to specify a path on the command line if a pid file is required.
2758 .cindex "daemon" "restarting"
2759 can be used to cause the daemon to re-execute itself. This should be done
2760 whenever Exim's configuration file, or any file that is incorporated into it by
2761 means of the &%.include%& facility, is changed, and also whenever a new version
2762 of Exim is installed. It is not necessary to do this when other files that are
2763 referenced from the configuration (for example, alias files) are changed,
2764 because these are reread each time they are used.
2768 This option has the same effect as &%-bd%& except that it never disconnects
2769 from the controlling terminal, even when no debugging is specified.
2773 .cindex "testing" "string expansion"
2774 .cindex "expansion" "testing"
2775 Run Exim in expansion testing mode. Exim discards its root privilege, to
2776 prevent ordinary users from using this mode to read otherwise inaccessible
2777 files. If no arguments are given, Exim runs interactively, prompting for lines
2778 of data. Otherwise, it processes each argument in turn.
2780 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2781 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2782 used without command line arguments. If successful, it uses the &[readline()]&
2783 function, which provides extensive line-editing facilities, for reading the
2784 test data. A line history is supported.
2786 Long expansion expressions can be split over several lines by using backslash
2787 continuations. As in Exim's run time configuration, white space at the start of
2788 continuation lines is ignored. Each argument or data line is passed through the
2789 string expansion mechanism, and the result is output. Variable values from the
2790 configuration file (for example, &$qualify_domain$&) are available, but no
2791 message-specific values (such as &$sender_domain$&) are set, because no message
2792 is being processed (but see &%-bem%& and &%-Mset%&).
2794 &*Note*&: If you use this mechanism to test lookups, and you change the data
2795 files or databases you are using, you must exit and restart Exim before trying
2796 the same lookup again. Otherwise, because each Exim process caches the results
2797 of lookups, you will just get the same result as before.
2799 .vitem &%-bem%&&~<&'filename'&>
2801 .cindex "testing" "string expansion"
2802 .cindex "expansion" "testing"
2803 This option operates like &%-be%& except that it must be followed by the name
2804 of a file. For example:
2806 exim -bem /tmp/testmessage
2808 The file is read as a message (as if receiving a locally-submitted non-SMTP
2809 message) before any of the test expansions are done. Thus, message-specific
2810 variables such as &$message_size$& and &$header_from:$& are available. However,
2811 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2812 recipients are read from the headers in the normal way, and are shown in the
2813 &$recipients$& variable. Note that recipients cannot be given on the command
2814 line, because further arguments are taken as strings to expand (just like
2817 .vitem &%-bF%&&~<&'filename'&>
2819 .cindex "system filter" "testing"
2820 .cindex "testing" "system filter"
2821 This option is the same as &%-bf%& except that it assumes that the filter being
2822 tested is a system filter. The additional commands that are available only in
2823 system filters are recognized.
2825 .vitem &%-bf%&&~<&'filename'&>
2827 .cindex "filter" "testing"
2828 .cindex "testing" "filter file"
2829 .cindex "forward file" "testing"
2830 .cindex "testing" "forward file"
2831 .cindex "Sieve filter" "testing"
2832 This option runs Exim in user filter testing mode; the file is the filter file
2833 to be tested, and a test message must be supplied on the standard input. If
2834 there are no message-dependent tests in the filter, an empty file can be
2837 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2838 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2839 filter and a user filter in the same run. For example:
2841 exim -bF /system/filter -bf /user/filter </test/message
2843 This is helpful when the system filter adds header lines or sets filter
2844 variables that are used by the user filter.
2846 If the test filter file does not begin with one of the special lines
2851 it is taken to be a normal &_.forward_& file, and is tested for validity under
2852 that interpretation. See sections &<<SECTitenonfilred>>& to
2853 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2856 The result of an Exim command that uses &%-bf%&, provided no errors are
2857 detected, is a list of the actions that Exim would try to take if presented
2858 with the message for real. More details of filter testing are given in the
2859 separate document entitled &'Exim's interfaces to mail filtering'&.
2861 When testing a filter file,
2862 .cindex "&""From""& line"
2863 .cindex "envelope sender"
2864 .oindex "&%-f%&" "for filter testing"
2865 the envelope sender can be set by the &%-f%& option,
2866 or by a &"From&~"& line at the start of the test message. Various parameters
2867 that would normally be taken from the envelope recipient address of the message
2868 can be set by means of additional command line options (see the next four
2871 .vitem &%-bfd%&&~<&'domain'&>
2873 .vindex "&$qualify_domain$&"
2874 This sets the domain of the recipient address when a filter file is being
2875 tested by means of the &%-bf%& option. The default is the value of
2878 .vitem &%-bfl%&&~<&'local&~part'&>
2880 This sets the local part of the recipient address when a filter file is being
2881 tested by means of the &%-bf%& option. The default is the username of the
2882 process that calls Exim. A local part should be specified with any prefix or
2883 suffix stripped, because that is how it appears to the filter when a message is
2884 actually being delivered.
2886 .vitem &%-bfp%&&~<&'prefix'&>
2888 This sets the prefix of the local part of the recipient address when a filter
2889 file is being tested by means of the &%-bf%& option. The default is an empty
2892 .vitem &%-bfs%&&~<&'suffix'&>
2894 This sets the suffix of the local part of the recipient address when a filter
2895 file is being tested by means of the &%-bf%& option. The default is an empty
2898 .vitem &%-bh%&&~<&'IP&~address'&>
2900 .cindex "testing" "incoming SMTP"
2901 .cindex "SMTP" "testing incoming"
2902 .cindex "testing" "relay control"
2903 .cindex "relaying" "testing configuration"
2904 .cindex "policy control" "testing"
2905 .cindex "debugging" "&%-bh%& option"
2906 This option runs a fake SMTP session as if from the given IP address, using the
2907 standard input and output. The IP address may include a port number at the end,
2908 after a full stop. For example:
2910 exim -bh 10.9.8.7.1234
2911 exim -bh fe80::a00:20ff:fe86:a061.5678
2913 When an IPv6 address is given, it is converted into canonical form. In the case
2914 of the second example above, the value of &$sender_host_address$& after
2915 conversion to the canonical form is
2916 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2918 Comments as to what is going on are written to the standard error file. These
2919 include lines beginning with &"LOG"& for anything that would have been logged.
2920 This facility is provided for testing configuration options for incoming
2921 messages, to make sure they implement the required policy. For example, you can
2922 test your relay controls using &%-bh%&.
2926 You can test features of the configuration that rely on ident (RFC 1413)
2927 information by using the &%-oMt%& option. However, Exim cannot actually perform
2928 an ident callout when testing using &%-bh%& because there is no incoming SMTP
2931 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2932 are also skipped when testing using &%-bh%&. If you want these callouts to
2933 occur, use &%-bhc%& instead.
2935 Messages supplied during the testing session are discarded, and nothing is
2936 written to any of the real log files. There may be pauses when DNS (and other)
2937 lookups are taking place, and of course these may time out. The &%-oMi%& option
2938 can be used to specify a specific IP interface and port if this is important,
2939 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
2940 session were authenticated.
2942 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2943 output just states whether a given recipient address from a given host is
2944 acceptable or not. See section &<<SECTcheckaccess>>&.
2946 Features such as authentication and encryption, where the client input is not
2947 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
2948 specialized SMTP test program such as
2949 &url(http://jetmore.org/john/code/#swaks,swaks).
2951 .vitem &%-bhc%&&~<&'IP&~address'&>
2953 This option operates in the same way as &%-bh%&, except that address
2954 verification callouts are performed if required. This includes consulting and
2955 updating the callout cache database.
2959 .cindex "alias file" "building"
2960 .cindex "building alias file"
2961 .cindex "Sendmail compatibility" "&%-bi%& option"
2962 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
2963 Exim does not have the concept of a single alias file, and so it cannot mimic
2964 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
2965 tend to appear in various scripts such as NIS make files, so the option must be
2968 If &%-bi%& is encountered, the command specified by the &%bi_command%&
2969 configuration option is run, under the uid and gid of the caller of Exim. If
2970 the &%-oA%& option is used, its value is passed to the command as an argument.
2971 The command set by &%bi_command%& may not contain arguments. The command can
2972 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
2973 if this is required. If the &%bi_command%& option is not set, calling Exim with
2976 . // Keep :help first, then the rest in alphabetical order
2978 .oindex "&%-bI:help%&"
2979 .cindex "querying exim information"
2980 We shall provide various options starting &`-bI:`& for querying Exim for
2981 information. The output of many of these will be intended for machine
2982 consumption. This one is not. The &%-bI:help%& option asks Exim for a
2983 synopsis of supported options beginning &`-bI:`&. Use of any of these
2984 options shall cause Exim to exit after producing the requested output.
2987 .oindex "&%-bI:dscp%&"
2988 .cindex "DSCP" "values"
2989 This option causes Exim to emit an alphabetically sorted list of all
2990 recognised DSCP names.
2992 .vitem &%-bI:sieve%&
2993 .oindex "&%-bI:sieve%&"
2994 .cindex "Sieve filter" "capabilities"
2995 This option causes Exim to emit an alphabetically sorted list of all supported
2996 Sieve protocol extensions on stdout, one per line. This is anticipated to be
2997 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
2998 &`SIEVE`& capability response line. As the precise list may depend upon
2999 compile-time build options, which this option will adapt to, this is the only
3000 way to guarantee a correct response.
3004 .cindex "local message reception"
3005 This option runs an Exim receiving process that accepts an incoming,
3006 locally-generated message on the standard input. The recipients are given as the
3007 command arguments (except when &%-t%& is also present &-- see below). Each
3008 argument can be a comma-separated list of RFC 2822 addresses. This is the
3009 default option for selecting the overall action of an Exim call; it is assumed
3010 if no other conflicting option is present.
3012 If any addresses in the message are unqualified (have no domain), they are
3013 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3014 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3015 suppressing this for special cases.
3017 Policy checks on the contents of local messages can be enforced by means of
3018 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3020 .cindex "return code" "for &%-bm%&"
3021 The return code is zero if the message is successfully accepted. Otherwise, the
3022 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3025 .cindex "message" "format"
3026 .cindex "format" "message"
3027 .cindex "&""From""& line"
3028 .cindex "UUCP" "&""From""& line"
3029 .cindex "Sendmail compatibility" "&""From""& line"
3030 of the message must be as defined in RFC 2822, except that, for
3031 compatibility with Sendmail and Smail, a line in one of the forms
3033 From sender Fri Jan 5 12:55 GMT 1997
3034 From sender Fri, 5 Jan 97 12:55:01
3036 (with the weekday optional, and possibly with additional text after the date)
3037 is permitted to appear at the start of the message. There appears to be no
3038 authoritative specification of the format of this line. Exim recognizes it by
3039 matching against the regular expression defined by the &%uucp_from_pattern%&
3040 option, which can be changed if necessary.
3042 .oindex "&%-f%&" "overriding &""From""& line"
3043 The specified sender is treated as if it were given as the argument to the
3044 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3045 preference to the address taken from the message. The caller of Exim must be a
3046 trusted user for the sender of a message to be set in this way.
3048 .vitem &%-bmalware%&&~<&'filename'&>
3049 .oindex "&%-bmalware%&"
3050 .cindex "testing", "malware"
3051 .cindex "malware scan test"
3052 This debugging option causes Exim to scan the given file,
3053 using the malware scanning framework. The option of &%av_scanner%& influences
3054 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3055 the expansion should have defaults which apply to this invocation. ACLs are
3056 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3057 will never be populated and &%-bmalware%& will fail.
3059 Exim will have changed working directory before resolving the filename, so
3060 using fully qualified pathnames is advisable. Exim will be running as the Exim
3061 user when it tries to open the file, rather than as the invoking user.
3062 This option requires admin privileges.
3064 The &%-bmalware%& option will not be extended to be more generally useful,
3065 there are better tools for file-scanning. This option exists to help
3066 administrators verify their Exim and AV scanner configuration.
3070 .cindex "address qualification, suppressing"
3071 By default, Exim automatically qualifies unqualified addresses (those
3072 without domains) that appear in messages that are submitted locally (that
3073 is, not over TCP/IP). This qualification applies both to addresses in
3074 envelopes, and addresses in header lines. Sender addresses are qualified using
3075 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3076 defaults to the value of &%qualify_domain%&).
3078 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3079 being used to re-submit messages that originally came from remote hosts after
3080 content scanning, you probably do not want to qualify unqualified addresses in
3081 header lines. (Such lines will be present only if you have not enabled a header
3082 syntax check in the appropriate ACL.)
3084 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3085 messages that originate on the local host. When this is used, unqualified
3086 addresses in the envelope provoke errors (causing message rejection) and
3087 unqualified addresses in header lines are left alone.
3092 .cindex "configuration options" "extracting"
3093 .cindex "options" "configuration &-- extracting"
3094 If this option is given with no arguments, it causes the values of all Exim's
3095 main configuration options to be written to the standard output. The values
3096 of one or more specific options can be requested by giving their names as
3097 arguments, for example:
3099 exim -bP qualify_domain hold_domains
3101 .cindex "hiding configuration option values"
3102 .cindex "configuration options" "hiding value of"
3103 .cindex "options" "hiding value of"
3104 However, any option setting that is preceded by the word &"hide"& in the
3105 configuration file is not shown in full, except to an admin user. For other
3106 users, the output is as in this example:
3108 mysql_servers = <value not displayable>
3110 If &%config%& is given as an argument, the config is
3111 output, as it was parsed, any include file resolved, any comment removed.
3113 If &%config_file%& is given as an argument, the name of the run time
3114 configuration file is output. (&%configure_file%& works too, for
3115 backward compatibility.)
3116 If a list of configuration files was supplied, the value that is output here
3117 is the name of the file that was actually used.
3119 .cindex "options" "hiding name of"
3120 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3121 name will not be output.
3123 .cindex "daemon" "process id (pid)"
3124 .cindex "pid (process id)" "of daemon"
3125 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3126 directories where log files and daemon pid files are written are output,
3127 respectively. If these values are unset, log files are written in a
3128 sub-directory of the spool directory called &%log%&, and the pid file is
3129 written directly into the spool directory.
3131 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3133 exim -bP +local_domains
3135 it searches for a matching named list of any type (domain, host, address, or
3136 local part) and outputs what it finds.
3138 .cindex "options" "router &-- extracting"
3139 .cindex "options" "transport &-- extracting"
3140 .cindex "options" "authenticator &-- extracting"
3141 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3142 followed by the name of an appropriate driver instance, the option settings for
3143 that driver are output. For example:
3145 exim -bP transport local_delivery
3147 The generic driver options are output first, followed by the driver's private
3148 options. A list of the names of drivers of a particular type can be obtained by
3149 using one of the words &%router_list%&, &%transport_list%&, or
3150 &%authenticator_list%&, and a complete list of all drivers with their option
3151 settings can be obtained by using &%routers%&, &%transports%&, or
3154 .cindex "options" "macro &-- extracting"
3155 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3156 are available, similarly to the drivers. Because macros are sometimes used
3157 for storing passwords, this option is restricted.
3158 The output format is one item per line.
3162 .cindex "queue" "listing messages on"
3163 .cindex "listing" "messages on the queue"
3164 This option requests a listing of the contents of the mail queue on the
3165 standard output. If the &%-bp%& option is followed by a list of message ids,
3166 just those messages are listed. By default, this option can be used only by an
3167 admin user. However, the &%queue_list_requires_admin%& option can be set false
3168 to allow any user to see the queue.
3170 Each message on the queue is displayed as in the following example:
3172 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3173 red.king@looking-glass.fict.example
3176 .cindex "message" "size in queue listing"
3177 .cindex "size" "of message"
3178 The first line contains the length of time the message has been on the queue
3179 (in this case 25 minutes), the size of the message (2.9K), the unique local
3180 identifier for the message, and the message sender, as contained in the
3181 envelope. For bounce messages, the sender address is empty, and appears as
3182 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3183 the default sender address, the user's login name is shown in parentheses
3184 before the sender address.
3186 .cindex "frozen messages" "in queue listing"
3187 If the message is frozen (attempts to deliver it are suspended) then the text
3188 &"*** frozen ***"& is displayed at the end of this line.
3190 The recipients of the message (taken from the envelope, not the headers) are
3191 displayed on subsequent lines. Those addresses to which the message has already
3192 been delivered are marked with the letter D. If an original address gets
3193 expanded into several addresses via an alias or forward file, the original is
3194 displayed with a D only when deliveries for all of its child addresses are
3200 This option operates like &%-bp%&, but in addition it shows delivered addresses
3201 that were generated from the original top level address(es) in each message by
3202 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3208 .cindex "queue" "count of messages on"
3209 This option counts the number of messages on the queue, and writes the total
3210 to the standard output. It is restricted to admin users, unless
3211 &%queue_list_requires_admin%& is set false.
3216 This option operates like &%-bp%&, but the output is not sorted into
3217 chronological order of message arrival. This can speed it up when there are
3218 lots of messages on the queue, and is particularly useful if the output is
3219 going to be post-processed in a way that doesn't need the sorting.
3223 This option is a combination of &%-bpr%& and &%-bpa%&.
3227 This option is a combination of &%-bpr%& and &%-bpu%&.
3232 This option operates like &%-bp%& but shows only undelivered top-level
3233 addresses for each message displayed. Addresses generated by aliasing or
3234 forwarding are not shown, unless the message was deferred after processing by a
3235 router with the &%one_time%& option set.
3240 .cindex "testing" "retry configuration"
3241 .cindex "retry" "configuration testing"
3242 This option is for testing retry rules, and it must be followed by up to three
3243 arguments. It causes Exim to look for a retry rule that matches the values
3244 and to write it to the standard output. For example:
3246 exim -brt bach.comp.mus.example
3247 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3249 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3250 argument, which is required, can be a complete address in the form
3251 &'local_part@domain'&, or it can be just a domain name. If the second argument
3252 contains a dot, it is interpreted as an optional second domain name; if no
3253 retry rule is found for the first argument, the second is tried. This ties in
3254 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3255 rule is found that matches the host, one that matches the mail domain is
3256 sought. Finally, an argument that is the name of a specific delivery error, as
3257 used in setting up retry rules, can be given. For example:
3259 exim -brt haydn.comp.mus.example quota_3d
3260 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3265 .cindex "testing" "rewriting"
3266 .cindex "rewriting" "testing"
3267 This option is for testing address rewriting rules, and it must be followed by
3268 a single argument, consisting of either a local part without a domain, or a
3269 complete address with a fully qualified domain. Exim outputs how this address
3270 would be rewritten for each possible place it might appear. See chapter
3271 &<<CHAPrewrite>>& for further details.
3275 .cindex "SMTP" "batched incoming"
3276 .cindex "batched SMTP input"
3277 This option is used for batched SMTP input, which is an alternative interface
3278 for non-interactive local message submission. A number of messages can be
3279 submitted in a single run. However, despite its name, this is not really SMTP
3280 input. Exim reads each message's envelope from SMTP commands on the standard
3281 input, but generates no responses. If the caller is trusted, or
3282 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3283 believed; otherwise the sender is always the caller of Exim.
3285 The message itself is read from the standard input, in SMTP format (leading
3286 dots doubled), terminated by a line containing just a single dot. An error is
3287 provoked if the terminating dot is missing. A further message may then follow.
3289 As for other local message submissions, the contents of incoming batch SMTP
3290 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3291 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3292 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3294 Some other SMTP commands are recognized in the input. HELO and EHLO act
3295 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3296 QUIT quits, ignoring the rest of the standard input.
3298 .cindex "return code" "for &%-bS%&"
3299 If any error is encountered, reports are written to the standard output and
3300 error streams, and Exim gives up immediately. The return code is 0 if no error
3301 was detected; it is 1 if one or more messages were accepted before the error
3302 was detected; otherwise it is 2.
3304 More details of input using batched SMTP are given in section
3305 &<<SECTincomingbatchedSMTP>>&.
3309 .cindex "SMTP" "local input"
3310 .cindex "local SMTP input"
3311 This option causes Exim to accept one or more messages by reading SMTP commands
3312 on the standard input, and producing SMTP replies on the standard output. SMTP
3313 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3314 Some user agents use this interface as a way of passing locally-generated
3315 messages to the MTA.
3318 .cindex "sender" "source of"
3319 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3320 set, the senders of messages are taken from the SMTP MAIL commands.
3321 Otherwise the content of these commands is ignored and the sender is set up as
3322 the calling user. Unqualified addresses are automatically qualified using
3323 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3324 &%-bnq%& option is used.
3328 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3329 using a listening daemon. Exim can distinguish the two cases by checking
3330 whether the standard input is a TCP/IP socket. When Exim is called from
3331 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3332 above concerning senders and qualification do not apply. In this situation,
3333 Exim behaves in exactly the same way as it does when receiving a message via
3334 the listening daemon.
3338 .cindex "testing" "addresses"
3339 .cindex "address" "testing"
3340 This option runs Exim in address testing mode, in which each argument is taken
3341 as a recipient address to be tested for deliverability. The results are
3342 written to the standard output. If a test fails, and the caller is not an admin
3343 user, no details of the failure are output, because these might contain
3344 sensitive information such as usernames and passwords for database lookups.
3346 If no arguments are given, Exim runs in an interactive manner, prompting with a
3347 right angle bracket for addresses to be tested.
3349 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3350 &[readline()]& function, because it is running as &'root'& and there are
3353 Each address is handled as if it were the recipient address of a message
3354 (compare the &%-bv%& option). It is passed to the routers and the result is
3355 written to the standard output. However, any router that has
3356 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3357 genuine routing tests if your first router passes everything to a scanner
3360 .cindex "return code" "for &%-bt%&"
3361 The return code is 2 if any address failed outright; it is 1 if no address
3362 failed outright but at least one could not be resolved for some reason. Return
3363 code 0 is given only when all addresses succeed.
3365 .cindex "duplicate addresses"
3366 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3367 addresses after routing is complete, so that only one delivery takes place.
3368 This does not happen when testing with &%-bt%&; the full results of routing are
3371 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3372 routers in the configuration makes any tests on the sender address of a
3374 .oindex "&%-f%&" "for address testing"
3375 you can use the &%-f%& option to set an appropriate sender when running
3376 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3377 default qualifying domain. However, if you have set up (for example) routers
3378 whose behaviour depends on the contents of an incoming message, you cannot test
3379 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3384 .cindex "version number of Exim"
3385 This option causes Exim to write the current version number, compilation
3386 number, and compilation date of the &'exim'& binary to the standard output.
3387 It also lists the DBM library that is being used, the optional modules (such as
3388 specific lookup types), the drivers that are included in the binary, and the
3389 name of the run time configuration file that is in use.
3391 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3392 configuration file. However, this is a static check only. It cannot check
3393 values that are to be expanded. For example, although a misspelt ACL verb is
3394 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3395 alone to discover (for example) all the typos in the configuration; some
3396 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3397 dynamic testing facilities.
3401 .cindex "verifying address" "using &%-bv%&"
3402 .cindex "address" "verification"
3403 This option runs Exim in address verification mode, in which each argument is
3404 taken as a recipient address to be verified by the routers. (This does
3405 not involve any verification callouts). During normal operation, verification
3406 happens mostly as a consequence processing a &%verify%& condition in an ACL
3407 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3408 including callouts, see the &%-bh%& and &%-bhc%& options.
3410 If verification fails, and the caller is not an admin user, no details of the
3411 failure are output, because these might contain sensitive information such as
3412 usernames and passwords for database lookups.
3414 If no arguments are given, Exim runs in an interactive manner, prompting with a
3415 right angle bracket for addresses to be verified.
3417 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3418 &[readline()]& function, because it is running as &'exim'& and there are
3421 Verification differs from address testing (the &%-bt%& option) in that routers
3422 that have &%no_verify%& set are skipped, and if the address is accepted by a
3423 router that has &%fail_verify%& set, verification fails. The address is
3424 verified as a recipient if &%-bv%& is used; to test verification for a sender
3425 address, &%-bvs%& should be used.
3427 If the &%-v%& option is not set, the output consists of a single line for each
3428 address, stating whether it was verified or not, and giving a reason in the
3429 latter case. Without &%-v%&, generating more than one address by redirection
3430 causes verification to end successfully, without considering the generated
3431 addresses. However, if just one address is generated, processing continues,
3432 and the generated address must verify successfully for the overall verification
3435 When &%-v%& is set, more details are given of how the address has been handled,
3436 and in the case of address redirection, all the generated addresses are also
3437 considered. Verification may succeed for some and fail for others.
3440 .cindex "return code" "for &%-bv%&"
3441 return code is 2 if any address failed outright; it is 1 if no address
3442 failed outright but at least one could not be resolved for some reason. Return
3443 code 0 is given only when all addresses succeed.
3445 If any of the routers in the configuration makes any tests on the sender
3446 address of a message, you should use the &%-f%& option to set an appropriate
3447 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3448 calling user at the default qualifying domain.
3452 This option acts like &%-bv%&, but verifies the address as a sender rather
3453 than a recipient address. This affects any rewriting and qualification that
3460 .cindex "inetd" "wait mode"
3461 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3462 similarly to the &%-bd%& option. All port specifications on the command-line
3463 and in the configuration file are ignored. Queue-running may not be specified.
3465 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3466 listening for connections. This permits the system to start up and have
3467 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3468 each port only when the first connection is received.
3470 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3471 which the daemon will exit, which should cause inetd to listen once more.
3473 .vitem &%-C%&&~<&'filelist'&>
3475 .cindex "configuration file" "alternate"
3476 .cindex "CONFIGURE_FILE"
3477 .cindex "alternate configuration file"
3478 This option causes Exim to find the run time configuration file from the given
3479 list instead of from the list specified by the CONFIGURE_FILE
3480 compile-time setting. Usually, the list will consist of just a single file
3481 name, but it can be a colon-separated list of names. In this case, the first
3482 file that exists is used. Failure to open an existing file stops Exim from
3483 proceeding any further along the list, and an error is generated.
3485 When this option is used by a caller other than root, and the list is different
3486 from the compiled-in list, Exim gives up its root privilege immediately, and
3487 runs with the real and effective uid and gid set to those of the caller.
3488 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3489 file contains a list of full pathnames, one per line, for configuration files
3490 which are trusted. Root privilege is retained for any configuration file so
3491 listed, as long as the caller is the Exim user (or the user specified in the
3492 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3493 not writeable by inappropriate users or groups.
3495 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3496 configuration using &%-C%& right through message reception and delivery,
3497 even if the caller is root. The reception works, but by that time, Exim is
3498 running as the Exim user, so when it re-executes to regain privilege for the
3499 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3500 test reception and delivery using two separate commands (one to put a message
3501 on the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3503 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3504 prefix string with which any file named in a &%-C%& command line option
3505 must start. In addition, the file name must not contain the sequence &`/../`&.
3506 However, if the value of the &%-C%& option is identical to the value of
3507 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3508 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3509 unset, any file name can be used with &%-C%&.
3511 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3512 to a directory to which only root has access. This prevents someone who has
3513 broken into the Exim account from running a privileged Exim with an arbitrary
3516 The &%-C%& facility is useful for ensuring that configuration files are
3517 syntactically correct, but cannot be used for test deliveries, unless the
3518 caller is privileged, or unless it is an exotic configuration that does not
3519 require privilege. No check is made on the owner or group of the files
3520 specified by this option.
3523 .vitem &%-D%&<&'macro'&>=<&'value'&>
3525 .cindex "macro" "setting on command line"
3526 This option can be used to override macro definitions in the configuration file
3527 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3528 unprivileged caller, it causes Exim to give up its root privilege.
3529 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3530 completely disabled, and its use causes an immediate error exit.
3532 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3533 colon-separated list of macros which are considered safe and, if &%-D%& only
3534 supplies macros from this list, and the values are acceptable, then Exim will
3535 not give up root privilege if the caller is root, the Exim run-time user, or
3536 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3537 to be removed in the future. Acceptable values for the macros satisfy the
3538 regexp: &`^[A-Za-z0-9_/.-]*$`&
3540 The entire option (including equals sign if present) must all be within one
3541 command line item. &%-D%& can be used to set the value of a macro to the empty
3542 string, in which case the equals sign is optional. These two commands are
3548 To include spaces in a macro definition item, quotes must be used. If you use
3549 quotes, spaces are permitted around the macro name and the equals sign. For
3552 exim '-D ABC = something' ...
3554 &%-D%& may be repeated up to 10 times on a command line.
3557 .vitem &%-d%&<&'debug&~options'&>
3559 .cindex "debugging" "list of selectors"
3560 .cindex "debugging" "&%-d%& option"
3561 This option causes debugging information to be written to the standard
3562 error stream. It is restricted to admin users because debugging output may show
3563 database queries that contain password information. Also, the details of users'
3564 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3565 writes an error message to the standard error stream and exits with a non-zero
3568 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3569 standard debugging data is output. This can be reduced, or increased to include
3570 some more rarely needed information, by directly following &%-d%& with a string
3571 made up of names preceded by plus or minus characters. These add or remove sets
3572 of debugging data, respectively. For example, &%-d+filter%& adds filter
3573 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3574 no spaces are allowed in the debug setting. The available debugging categories
3577 &`acl `& ACL interpretation
3578 &`auth `& authenticators
3579 &`deliver `& general delivery logic
3580 &`dns `& DNS lookups (see also resolver)
3581 &`dnsbl `& DNS black list (aka RBL) code
3582 &`exec `& arguments for &[execv()]& calls
3583 &`expand `& detailed debugging for string expansions
3584 &`filter `& filter handling
3585 &`hints_lookup `& hints data lookups
3586 &`host_lookup `& all types of name-to-IP address handling
3587 &`ident `& ident lookup
3588 &`interface `& lists of local interfaces
3589 &`lists `& matching things in lists
3590 &`load `& system load checks
3591 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3592 &<<CHAPlocalscan>>&)
3593 &`lookup `& general lookup code and all lookups
3594 &`memory `& memory handling
3595 &`pid `& add pid to debug output lines
3596 &`process_info `& setting info for the process log
3597 &`queue_run `& queue runs
3598 &`receive `& general message reception logic
3599 &`resolver `& turn on the DNS resolver's debugging output
3600 &`retry `& retry handling
3601 &`rewrite `& address rewriting
3602 &`route `& address routing
3603 &`timestamp `& add timestamp to debug output lines
3605 &`transport `& transports
3606 &`uid `& changes of uid/gid and looking up uid/gid
3607 &`verify `& address verification logic
3608 &`all `& almost all of the above (see below), and also &%-v%&
3610 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3611 for &`-all`&. The reason for this is that &`+all`& is something that people
3612 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3613 is included, an awful lot of output that is very rarely of interest is
3614 generated, so it now has to be explicitly requested. However, &`-all`& does
3615 turn everything off.
3617 .cindex "resolver, debugging output"
3618 .cindex "DNS resolver, debugging output"
3619 The &`resolver`& option produces output only if the DNS resolver was compiled
3620 with DEBUG enabled. This is not the case in some operating systems. Also,
3621 unfortunately, debugging output from the DNS resolver is written to stdout
3624 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3625 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3626 However, the &`pid`& selector is forced when debugging is turned on for a
3627 daemon, which then passes it on to any re-executed Exims. Exim also
3628 automatically adds the pid to debug lines when several remote deliveries are
3631 The &`timestamp`& selector causes the current time to be inserted at the start
3632 of all debug output lines. This can be useful when trying to track down delays
3635 If the &%debug_print%& option is set in any driver, it produces output whenever
3636 any debugging is selected, or if &%-v%& is used.
3638 .vitem &%-dd%&<&'debug&~options'&>
3640 This option behaves exactly like &%-d%& except when used on a command that
3641 starts a daemon process. In that case, debugging is turned off for the
3642 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3643 behaviour of the daemon without creating as much output as full debugging does.
3646 .oindex "&%-dropcr%&"
3647 This is an obsolete option that is now a no-op. It used to affect the way Exim
3648 handled CR and LF characters in incoming messages. What happens now is
3649 described in section &<<SECTlineendings>>&.
3653 .cindex "bounce message" "generating"
3654 This option specifies that an incoming message is a locally-generated delivery
3655 failure report. It is used internally by Exim when handling delivery failures
3656 and is not intended for external use. Its only effect is to stop Exim
3657 generating certain messages to the postmaster, as otherwise message cascades
3658 could occur in some situations. As part of the same option, a message id may
3659 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3660 new message contains the id, following &"R="&, as a cross-reference.
3663 .oindex "&%-e%&&'x'&"
3664 There are a number of Sendmail options starting with &%-oe%& which seem to be
3665 called by various programs without the leading &%o%& in the option. For
3666 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3667 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3669 .vitem &%-F%&&~<&'string'&>
3671 .cindex "sender" "name"
3672 .cindex "name" "of sender"
3673 This option sets the sender's full name for use when a locally-generated
3674 message is being accepted. In the absence of this option, the user's &'gecos'&
3675 entry from the password data is used. As users are generally permitted to alter
3676 their &'gecos'& entries, no security considerations are involved. White space
3677 between &%-F%& and the <&'string'&> is optional.
3679 .vitem &%-f%&&~<&'address'&>
3681 .cindex "sender" "address"
3682 .cindex "address" "sender"
3683 .cindex "trusted users"
3684 .cindex "envelope sender"
3685 .cindex "user" "trusted"
3686 This option sets the address of the envelope sender of a locally-generated
3687 message (also known as the return path). The option can normally be used only
3688 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3691 Processes running as root or the Exim user are always trusted. Other
3692 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3693 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3694 of a local message is set to the caller's login name at the default qualify
3697 There is one exception to the restriction on the use of &%-f%&: an empty sender
3698 can be specified by any user, trusted or not, to create a message that can
3699 never provoke a bounce. An empty sender can be specified either as an empty
3700 string, or as a pair of angle brackets with nothing between them, as in these
3701 examples of shell commands:
3703 exim -f '<>' user@domain
3704 exim -f "" user@domain
3706 In addition, the use of &%-f%& is not restricted when testing a filter file
3707 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3710 Allowing untrusted users to change the sender address does not of itself make
3711 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3712 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3713 though this can be overridden by setting &%no_local_from_check%&.
3716 .cindex "&""From""& line"
3717 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3718 given as two arguments or one combined argument). The sender of a
3719 locally-generated message can also be set (when permitted) by an initial
3720 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3721 if &%-f%& is also present, it overrides &"From&~"&.
3725 .cindex "submission fixups, suppressing (command-line)"
3726 This option is equivalent to an ACL applying:
3728 control = suppress_local_fixups
3730 for every message received. Note that Sendmail will complain about such
3731 bad formatting, where Exim silently just does not fix it up. This may change
3734 As this affects audit information, the caller must be a trusted user to use
3737 .vitem &%-h%&&~<&'number'&>
3739 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3740 This option is accepted for compatibility with Sendmail, but has no effect. (In
3741 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3746 .cindex "Solaris" "&'mail'& command"
3747 .cindex "dot" "in incoming non-SMTP message"
3748 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3749 line by itself should not terminate an incoming, non-SMTP message. I can find
3750 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3751 command in Solaris 2.4 uses it. See also &%-ti%&.
3753 .vitem &%-L%&&~<&'tag'&>
3755 .cindex "syslog" "process name; set with flag"
3756 This option is equivalent to setting &%syslog_processname%& in the config
3757 file and setting &%log_file_path%& to &`syslog`&.
3758 Its use is restricted to administrators. The configuration file has to be
3759 read and parsed, to determine access rights, before this is set and takes
3760 effect, so early configuration file errors will not honour this flag.
3762 The tag should not be longer than 32 characters.
3764 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3766 .cindex "forcing delivery"
3767 .cindex "delivery" "forcing attempt"
3768 .cindex "frozen messages" "forcing delivery"
3769 This option requests Exim to run a delivery attempt on each message in turn. If
3770 any of the messages are frozen, they are automatically thawed before the
3771 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3772 and &%hold_domains%& are ignored.
3775 .cindex "hints database" "overriding retry hints"
3776 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3777 the normal retry time has not yet been reached. This option requires the caller
3778 to be an admin user. However, there is an option called &%prod_requires_admin%&
3779 which can be set false to relax this restriction (and also the same requirement
3780 for the &%-q%&, &%-R%&, and &%-S%& options).
3782 The deliveries happen synchronously, that is, the original Exim process does
3783 not terminate until all the delivery attempts have finished. No output is
3784 produced unless there is a serious error. If you want to see what is happening,
3785 use the &%-v%& option as well, or inspect Exim's main log.
3787 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3789 .cindex "message" "adding recipients"
3790 .cindex "recipient" "adding"
3791 This option requests Exim to add the addresses to the list of recipients of the
3792 message (&"ar"& for &"add recipients"&). The first argument must be a message
3793 id, and the remaining ones must be email addresses. However, if the message is
3794 active (in the middle of a delivery attempt), it is not altered. This option
3795 can be used only by an admin user.
3797 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3798 &~<&'message&~id'&>"
3800 .cindex "SMTP" "passed connection"
3801 .cindex "SMTP" "multiple deliveries"
3802 .cindex "multiple SMTP deliveries"
3803 This option is not intended for use by external callers. It is used internally
3804 by Exim to invoke another instance of itself to deliver a waiting message using
3805 an existing SMTP connection, which is passed as the standard input. Details are
3806 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3807 must be root or the Exim user in order to use it.
3811 This option is not intended for use by external callers. It is used internally
3812 by Exim in conjunction with the &%-MC%& option. It signifies that the
3813 connection to the remote host has been authenticated.
3817 This option is not intended for use by external callers. It is used internally
3818 by Exim in conjunction with the &%-MC%& option. It signifies that the
3819 remote host supports the ESMTP &_DSN_& extension.
3823 This option is not intended for use by external callers. It is used internally
3824 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3825 which Exim is connected supports pipelining.
3827 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3829 This option is not intended for use by external callers. It is used internally
3830 by Exim in conjunction with the &%-MC%& option when the original delivery was
3831 started by a queue runner. It passes on the process id of the queue runner,
3832 together with the file descriptor number of an open pipe. Closure of the pipe
3833 signals the final completion of the sequence of processes that are passing
3834 messages through the same SMTP connection.
3838 This option is not intended for use by external callers. It is used internally
3839 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3840 SMTP SIZE option should be used on messages delivered down the existing
3845 This option is not intended for use by external callers. It is used internally
3846 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3847 host to which Exim is connected supports TLS encryption.
3849 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3851 .cindex "hints database" "not overridden by &%-Mc%&"
3852 .cindex "delivery" "manually started &-- not forced"
3853 This option requests Exim to run a delivery attempt on each message in turn,
3854 but unlike the &%-M%& option, it does check for retry hints, and respects any
3855 that are found. This option is not very useful to external callers. It is
3856 provided mainly for internal use by Exim when it needs to re-invoke itself in
3857 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3858 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3859 respects retry times and other options such as &%hold_domains%& that are
3860 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3861 If you want to run a specific delivery as if in a queue run, you should use
3862 &%-q%& with a message id argument. A distinction between queue run deliveries
3863 and other deliveries is made in one or two places.
3865 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3867 .cindex "message" "changing sender"
3868 .cindex "sender" "changing"
3869 This option requests Exim to change the sender address in the message to the
3870 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3871 &"edit sender"&). There must be exactly two arguments. The first argument must
3872 be a message id, and the second one an email address. However, if the message
3873 is active (in the middle of a delivery attempt), its status is not altered.
3874 This option can be used only by an admin user.
3876 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3878 .cindex "freezing messages"
3879 .cindex "message" "manually freezing"
3880 This option requests Exim to mark each listed message as &"frozen"&. This
3881 prevents any delivery attempts taking place until the message is &"thawed"&,
3882 either manually or as a result of the &%auto_thaw%& configuration option.
3883 However, if any of the messages are active (in the middle of a delivery
3884 attempt), their status is not altered. This option can be used only by an admin
3887 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3889 .cindex "giving up on messages"
3890 .cindex "message" "abandoning delivery attempts"
3891 .cindex "delivery" "abandoning further attempts"
3892 This option requests Exim to give up trying to deliver the listed messages,
3893 including any that are frozen. However, if any of the messages are active,
3894 their status is not altered. For non-bounce messages, a delivery error message
3895 is sent to the sender, containing the text &"cancelled by administrator"&.
3896 Bounce messages are just discarded. This option can be used only by an admin
3899 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3901 .cindex "delivery" "cancelling all"
3902 This option requests Exim to mark all the recipient addresses in the messages
3903 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
3904 message is active (in the middle of a delivery attempt), its status is not
3905 altered. This option can be used only by an admin user.
3907 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3909 .cindex "delivery" "cancelling by address"
3910 .cindex "recipient" "removing"
3911 .cindex "removing recipients"
3912 This option requests Exim to mark the given addresses as already delivered
3913 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
3914 the remaining ones must be email addresses. These are matched to recipient
3915 addresses in the message in a case-sensitive manner. If the message is active
3916 (in the middle of a delivery attempt), its status is not altered. This option
3917 can be used only by an admin user.
3919 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3921 .cindex "removing messages"
3922 .cindex "abandoning mail"
3923 .cindex "message" "manually discarding"
3924 This option requests Exim to remove the given messages from the queue. No
3925 bounce messages are sent; each message is simply forgotten. However, if any of
3926 the messages are active, their status is not altered. This option can be used
3927 only by an admin user or by the user who originally caused the message to be
3928 placed on the queue.
3930 .vitem &%-Mset%&&~<&'message&~id'&>
3932 .cindex "testing" "string expansion"
3933 .cindex "expansion" "testing"
3934 This option is useful only in conjunction with &%-be%& (that is, when testing
3935 string expansions). Exim loads the given message from its spool before doing
3936 the test expansions, thus setting message-specific variables such as
3937 &$message_size$& and the header variables. The &$recipients$& variable is made
3938 available. This feature is provided to make it easier to test expansions that
3939 make use of these variables. However, this option can be used only by an admin
3940 user. See also &%-bem%&.
3942 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3944 .cindex "thawing messages"
3945 .cindex "unfreezing messages"
3946 .cindex "frozen messages" "thawing"
3947 .cindex "message" "thawing frozen"
3948 This option requests Exim to &"thaw"& any of the listed messages that are
3949 &"frozen"&, so that delivery attempts can resume. However, if any of the
3950 messages are active, their status is not altered. This option can be used only
3953 .vitem &%-Mvb%&&~<&'message&~id'&>
3955 .cindex "listing" "message body"
3956 .cindex "message" "listing body of"
3957 This option causes the contents of the message body (-D) spool file to be
3958 written to the standard output. This option can be used only by an admin user.
3960 .vitem &%-Mvc%&&~<&'message&~id'&>
3962 .cindex "message" "listing in RFC 2822 format"
3963 .cindex "listing" "message in RFC 2822 format"
3964 This option causes a copy of the complete message (header lines plus body) to
3965 be written to the standard output in RFC 2822 format. This option can be used
3966 only by an admin user.
3968 .vitem &%-Mvh%&&~<&'message&~id'&>
3970 .cindex "listing" "message headers"
3971 .cindex "header lines" "listing"
3972 .cindex "message" "listing header lines"
3973 This option causes the contents of the message headers (-H) spool file to be
3974 written to the standard output. This option can be used only by an admin user.
3976 .vitem &%-Mvl%&&~<&'message&~id'&>
3978 .cindex "listing" "message log"
3979 .cindex "message" "listing message log"
3980 This option causes the contents of the message log spool file to be written to
3981 the standard output. This option can be used only by an admin user.
3985 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
3986 treats it that way too.
3990 .cindex "debugging" "&%-N%& option"
3991 .cindex "debugging" "suppressing delivery"
3992 This is a debugging option that inhibits delivery of a message at the transport
3993 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
3994 it just doesn't actually transport the message, but instead behaves as if it
3995 had successfully done so. However, it does not make any updates to the retry
3996 database, and the log entries for deliveries are flagged with &"*>"& rather
3999 Because &%-N%& discards any message to which it applies, only root or the Exim
4000 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
4001 words, an ordinary user can use it only when supplying an incoming message to
4002 which it will apply. Although transportation never fails when &%-N%& is set, an
4003 address may be deferred because of a configuration problem on a transport, or a
4004 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
4005 the message, and applies to any subsequent delivery attempts that may happen
4010 This option is interpreted by Sendmail to mean &"no aliasing"&.
4011 For normal modes of operation, it is ignored by Exim.
4012 When combined with &%-bP%& it suppresses the name of an option from being output.
4014 .vitem &%-O%&&~<&'data'&>
4016 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4019 .vitem &%-oA%&&~<&'file&~name'&>
4021 .cindex "Sendmail compatibility" "&%-oA%& option"
4022 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4023 alternative alias file name. Exim handles &%-bi%& differently; see the
4026 .vitem &%-oB%&&~<&'n'&>
4028 .cindex "SMTP" "passed connection"
4029 .cindex "SMTP" "multiple deliveries"
4030 .cindex "multiple SMTP deliveries"
4031 This is a debugging option which limits the maximum number of messages that can
4032 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4033 transport. If <&'n'&> is omitted, the limit is set to 1.
4037 .cindex "background delivery"
4038 .cindex "delivery" "in the background"
4039 This option applies to all modes in which Exim accepts incoming messages,
4040 including the listening daemon. It requests &"background"& delivery of such
4041 messages, which means that the accepting process automatically starts a
4042 delivery process for each message received, but does not wait for the delivery
4043 processes to finish.
4045 When all the messages have been received, the reception process exits,
4046 leaving the delivery processes to finish in their own time. The standard output
4047 and error streams are closed at the start of each delivery process.
4048 This is the default action if none of the &%-od%& options are present.
4050 If one of the queueing options in the configuration file
4051 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4052 overrides it if &%queue_only_override%& is set true, which is the default
4053 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4057 .cindex "foreground delivery"
4058 .cindex "delivery" "in the foreground"
4059 This option requests &"foreground"& (synchronous) delivery when Exim has
4060 accepted a locally-generated message. (For the daemon it is exactly the same as
4061 &%-odb%&.) A delivery process is automatically started to deliver the message,
4062 and Exim waits for it to complete before proceeding.
4064 The original Exim reception process does not finish until the delivery
4065 process for the final message has ended. The standard error stream is left open
4068 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4069 false and one of the queueing options in the configuration file is in effect.
4071 If there is a temporary delivery error during foreground delivery, the
4072 message is left on the queue for later delivery, and the original reception
4073 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4074 restricted configuration that never queues messages.
4079 This option is synonymous with &%-odf%&. It is provided for compatibility with
4084 .cindex "non-immediate delivery"
4085 .cindex "delivery" "suppressing immediate"
4086 .cindex "queueing incoming messages"
4087 This option applies to all modes in which Exim accepts incoming messages,
4088 including the listening daemon. It specifies that the accepting process should
4089 not automatically start a delivery process for each message received. Messages
4090 are placed on the queue, and remain there until a subsequent queue runner
4091 process encounters them. There are several configuration options (such as
4092 &%queue_only%&) that can be used to queue incoming messages under certain
4093 conditions. This option overrides all of them and also &%-odqs%&. It always
4098 .cindex "SMTP" "delaying delivery"
4099 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4100 However, like &%-odb%& and &%-odi%&, this option has no effect if
4101 &%queue_only_override%& is false and one of the queueing options in the
4102 configuration file is in effect.
4104 When &%-odqs%& does operate, a delivery process is started for each incoming
4105 message, in the background by default, but in the foreground if &%-odi%& is
4106 also present. The recipient addresses are routed, and local deliveries are done
4107 in the normal way. However, if any SMTP deliveries are required, they are not
4108 done at this time, so the message remains on the queue until a subsequent queue
4109 runner process encounters it. Because routing was done, Exim knows which
4110 messages are waiting for which hosts, and so a number of messages for the same
4111 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4112 configuration option has the same effect for specific domains. See also the
4117 .cindex "error" "reporting"
4118 If an error is detected while a non-SMTP message is being received (for
4119 example, a malformed address), the error is reported to the sender in a mail
4122 .cindex "return code" "for &%-oee%&"
4124 this error message is successfully sent, the Exim receiving process
4125 exits with a return code of zero. If not, the return code is 2 if the problem
4126 is that the original message has no recipients, or 1 for any other error.
4127 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4131 .cindex "error" "reporting"
4132 .cindex "return code" "for &%-oem%&"
4133 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4134 return code, whether or not the error message was successfully sent.
4135 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4139 .cindex "error" "reporting"
4140 If an error is detected while a non-SMTP message is being received, the
4141 error is reported by writing a message to the standard error file (stderr).
4142 .cindex "return code" "for &%-oep%&"
4143 The return code is 1 for all errors.
4147 .cindex "error" "reporting"
4148 This option is supported for compatibility with Sendmail, but has the same
4153 .cindex "error" "reporting"
4154 This option is supported for compatibility with Sendmail, but has the same
4159 .cindex "dot" "in incoming non-SMTP message"
4160 This option, which has the same effect as &%-i%&, specifies that a dot on a
4161 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4162 single dot does terminate, though Exim does no special processing for other
4163 lines that start with a dot. This option is set by default if Exim is called as
4164 &'rmail'&. See also &%-ti%&.
4167 .oindex "&%-oitrue%&"
4168 This option is treated as synonymous with &%-oi%&.
4170 .vitem &%-oMa%&&~<&'host&~address'&>
4172 .cindex "sender" "host address, specifying for local message"
4173 A number of options starting with &%-oM%& can be used to set values associated
4174 with remote hosts on locally-submitted messages (that is, messages not received
4175 over TCP/IP). These options can be used by any caller in conjunction with the
4176 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4177 other circumstances, they are ignored unless the caller is trusted.
4179 The &%-oMa%& option sets the sender host address. This may include a port
4180 number at the end, after a full stop (period). For example:
4182 exim -bs -oMa 10.9.8.7.1234
4184 An alternative syntax is to enclose the IP address in square brackets,
4185 followed by a colon and the port number:
4187 exim -bs -oMa [10.9.8.7]:1234
4189 The IP address is placed in the &$sender_host_address$& variable, and the
4190 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4191 are present on the command line, the sender host IP address is taken from
4192 whichever one is last.
4194 .vitem &%-oMaa%&&~<&'name'&>
4196 .cindex "authentication" "name, specifying for local message"
4197 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4198 option sets the value of &$sender_host_authenticated$& (the authenticator
4199 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4200 This option can be used with &%-bh%& and &%-bs%& to set up an
4201 authenticated SMTP session without actually using the SMTP AUTH command.
4203 .vitem &%-oMai%&&~<&'string'&>
4205 .cindex "authentication" "id, specifying for local message"
4206 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4207 option sets the value of &$authenticated_id$& (the id that was authenticated).
4208 This overrides the default value (the caller's login id, except with &%-bh%&,
4209 where there is no default) for messages from local sources. See chapter
4210 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4212 .vitem &%-oMas%&&~<&'address'&>
4214 .cindex "authentication" "sender, specifying for local message"
4215 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4216 option sets the authenticated sender value in &$authenticated_sender$&. It
4217 overrides the sender address that is created from the caller's login id for
4218 messages from local sources, except when &%-bh%& is used, when there is no
4219 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4220 specified on a MAIL command overrides this value. See chapter
4221 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4223 .vitem &%-oMi%&&~<&'interface&~address'&>
4225 .cindex "interface" "address, specifying for local message"
4226 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4227 option sets the IP interface address value. A port number may be included,
4228 using the same syntax as for &%-oMa%&. The interface address is placed in
4229 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4231 .vitem &%-oMm%&&~<&'message&~reference'&>
4233 .cindex "message reference" "message reference, specifying for local message"
4234 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4235 option sets the message reference, e.g. message-id, and is logged during
4236 delivery. This is useful when some kind of audit trail is required to tie
4237 messages together. The format of the message reference is checked and will
4238 abort if the format is invalid. The option will only be accepted if exim is
4239 running in trusted mode, not as any regular user.
4241 The best example of a message reference is when Exim sends a bounce message.
4242 The message reference is the message-id of the original message for which Exim
4243 is sending the bounce.
4245 .vitem &%-oMr%&&~<&'protocol&~name'&>
4247 .cindex "protocol, specifying for local message"
4248 .vindex "&$received_protocol$&"
4249 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4250 option sets the received protocol value that is stored in
4251 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4252 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4253 SMTP protocol names (see the description of &$received_protocol$& in section
4254 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4255 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4258 .vitem &%-oMs%&&~<&'host&~name'&>
4260 .cindex "sender" "host name, specifying for local message"
4261 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4262 option sets the sender host name in &$sender_host_name$&. When this option is
4263 present, Exim does not attempt to look up a host name from an IP address; it
4264 uses the name it is given.
4266 .vitem &%-oMt%&&~<&'ident&~string'&>
4268 .cindex "sender" "ident string, specifying for local message"
4269 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4270 option sets the sender ident value in &$sender_ident$&. The default setting for
4271 local callers is the login id of the calling process, except when &%-bh%& is
4272 used, when there is no default.
4276 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4277 In Sendmail, this option means &"me too"&, indicating that the sender of a
4278 message should receive a copy of the message if the sender appears in an alias
4279 expansion. Exim always does this, so the option does nothing.
4283 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4284 This option is ignored. In Sendmail it specifies &"old style headers"&,
4285 whatever that means.
4287 .vitem &%-oP%&&~<&'path'&>
4289 .cindex "pid (process id)" "of daemon"
4290 .cindex "daemon" "process id (pid)"
4291 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4292 value. The option specifies the file to which the process id of the daemon is
4293 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4294 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4295 because in those cases, the normal pid file is not used.
4297 .vitem &%-or%&&~<&'time'&>
4299 .cindex "timeout" "for non-SMTP input"
4300 This option sets a timeout value for incoming non-SMTP messages. If it is not
4301 set, Exim will wait forever for the standard input. The value can also be set
4302 by the &%receive_timeout%& option. The format used for specifying times is
4303 described in section &<<SECTtimeformat>>&.
4305 .vitem &%-os%&&~<&'time'&>
4307 .cindex "timeout" "for SMTP input"
4308 .cindex "SMTP" "input timeout"
4309 This option sets a timeout value for incoming SMTP messages. The timeout
4310 applies to each SMTP command and block of data. The value can also be set by
4311 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4312 for specifying times is described in section &<<SECTtimeformat>>&.
4316 This option has exactly the same effect as &%-v%&.
4318 .vitem &%-oX%&&~<&'number&~or&~string'&>
4320 .cindex "TCP/IP" "setting listening ports"
4321 .cindex "TCP/IP" "setting listening interfaces"
4322 .cindex "port" "receiving TCP/IP"
4323 This option is relevant only when the &%-bd%& (start listening daemon) option
4324 is also given. It controls which ports and interfaces the daemon uses. Details
4325 of the syntax, and how it interacts with configuration file options, are given
4326 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4327 file is written unless &%-oP%& is also present to specify a pid file name.
4331 .cindex "Perl" "starting the interpreter"
4332 This option applies when an embedded Perl interpreter is linked with Exim (see
4333 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4334 option, forcing the starting of the interpreter to be delayed until it is
4339 .cindex "Perl" "starting the interpreter"
4340 This option applies when an embedded Perl interpreter is linked with Exim (see
4341 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4342 option, forcing the starting of the interpreter to occur as soon as Exim is
4345 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4347 For compatibility with Sendmail, this option is equivalent to
4349 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4351 It sets the incoming protocol and host name (for trusted callers). The
4352 host name and its colon can be omitted when only the protocol is to be set.
4353 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4354 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4355 or &`s`& using this option (but that does not seem a real limitation).
4359 .cindex "queue runner" "starting manually"
4360 This option is normally restricted to admin users. However, there is a
4361 configuration option called &%prod_requires_admin%& which can be set false to
4362 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4363 and &%-S%& options).
4365 .cindex "queue runner" "description of operation"
4366 The &%-q%& option starts one queue runner process. This scans the queue of
4367 waiting messages, and runs a delivery process for each one in turn. It waits
4368 for each delivery process to finish before starting the next one. A delivery
4369 process may not actually do any deliveries if the retry times for the addresses
4370 have not been reached. Use &%-qf%& (see below) if you want to override this.
4373 .cindex "SMTP" "passed connection"
4374 .cindex "SMTP" "multiple deliveries"
4375 .cindex "multiple SMTP deliveries"
4376 the delivery process spawns other processes to deliver other messages down
4377 passed SMTP connections, the queue runner waits for these to finish before
4380 When all the queued messages have been considered, the original queue runner
4381 process terminates. In other words, a single pass is made over the waiting
4382 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4383 this to be repeated periodically.
4385 Exim processes the waiting messages in an unpredictable order. It isn't very
4386 random, but it is likely to be different each time, which is all that matters.
4387 If one particular message screws up a remote MTA, other messages to the same
4388 MTA have a chance of getting through if they get tried first.
4390 It is possible to cause the messages to be processed in lexical message id
4391 order, which is essentially the order in which they arrived, by setting the
4392 &%queue_run_in_order%& option, but this is not recommended for normal use.
4394 .vitem &%-q%&<&'qflags'&>
4395 The &%-q%& option may be followed by one or more flag letters that change its
4396 behaviour. They are all optional, but if more than one is present, they must
4397 appear in the correct order. Each flag is described in a separate item below.
4401 .cindex "queue" "double scanning"
4402 .cindex "queue" "routing"
4403 .cindex "routing" "whole queue before delivery"
4404 An option starting with &%-qq%& requests a two-stage queue run. In the first
4405 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4406 every domain. Addresses are routed, local deliveries happen, but no remote
4409 .cindex "hints database" "remembering routing"
4410 The hints database that remembers which messages are waiting for specific hosts
4411 is updated, as if delivery to those hosts had been deferred. After this is
4412 complete, a second, normal queue scan happens, with routing and delivery taking
4413 place as normal. Messages that are routed to the same host should mostly be
4414 delivered down a single SMTP
4415 .cindex "SMTP" "passed connection"
4416 .cindex "SMTP" "multiple deliveries"
4417 .cindex "multiple SMTP deliveries"
4418 connection because of the hints that were set up during the first queue scan.
4419 This option may be useful for hosts that are connected to the Internet
4422 .vitem &%-q[q]i...%&
4424 .cindex "queue" "initial delivery"
4425 If the &'i'& flag is present, the queue runner runs delivery processes only for
4426 those messages that haven't previously been tried. (&'i'& stands for &"initial
4427 delivery"&.) This can be helpful if you are putting messages on the queue using
4428 &%-odq%& and want a queue runner just to process the new messages.
4430 .vitem &%-q[q][i]f...%&
4432 .cindex "queue" "forcing delivery"
4433 .cindex "delivery" "forcing in queue run"
4434 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4435 message, whereas without &'f'& only those non-frozen addresses that have passed
4436 their retry times are tried.
4438 .vitem &%-q[q][i]ff...%&
4440 .cindex "frozen messages" "forcing delivery"
4441 If &'ff'& is present, a delivery attempt is forced for every message, whether
4444 .vitem &%-q[q][i][f[f]]l%&
4446 .cindex "queue" "local deliveries only"
4447 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4448 be done. If a message requires any remote deliveries, it remains on the queue
4451 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4452 .cindex "queue" "delivering specific messages"
4453 When scanning the queue, Exim can be made to skip over messages whose ids are
4454 lexically less than a given value by following the &%-q%& option with a
4455 starting message id. For example:
4457 exim -q 0t5C6f-0000c8-00
4459 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4460 second message id is given, messages whose ids are lexically greater than it
4461 are also skipped. If the same id is given twice, for example,
4463 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4465 just one delivery process is started, for that message. This differs from
4466 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4467 that it counts as a delivery from a queue run. Note that the selection
4468 mechanism does not affect the order in which the messages are scanned. There
4469 are also other ways of selecting specific sets of messages for delivery in a
4470 queue run &-- see &%-R%& and &%-S%&.
4472 .vitem &%-q%&<&'qflags'&><&'time'&>
4473 .cindex "queue runner" "starting periodically"
4474 .cindex "periodic queue running"
4475 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4476 starting a queue runner process at intervals specified by the given time value
4477 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4478 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4479 single daemon process handles both functions. A common way of starting up a
4480 combined daemon at system boot time is to use a command such as
4482 /usr/exim/bin/exim -bd -q30m
4484 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4485 process every 30 minutes.
4487 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4488 pid file is written unless one is explicitly requested by the &%-oP%& option.
4490 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4492 This option is synonymous with &%-R%&. It is provided for Sendmail
4495 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4497 This option is synonymous with &%-S%&.
4499 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4501 .cindex "queue runner" "for specific recipients"
4502 .cindex "delivery" "to given domain"
4503 .cindex "domain" "delivery to"
4504 The <&'rsflags'&> may be empty, in which case the white space before the string
4505 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4506 which are the possible values for <&'rsflags'&>. White space is required if
4507 <&'rsflags'&> is not empty.
4509 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4510 perform a single queue run, except that, when scanning the messages on the
4511 queue, Exim processes only those that have at least one undelivered recipient
4512 address containing the given string, which is checked in a case-independent
4513 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4514 regular expression; otherwise it is a literal string.
4516 If you want to do periodic queue runs for messages with specific recipients,
4517 you can combine &%-R%& with &%-q%& and a time value. For example:
4519 exim -q25m -R @special.domain.example
4521 This example does a queue run for messages with recipients in the given domain
4522 every 25 minutes. Any additional flags that are specified with &%-q%& are
4523 applied to each queue run.
4525 Once a message is selected for delivery by this mechanism, all its addresses
4526 are processed. For the first selected message, Exim overrides any retry
4527 information and forces a delivery attempt for each undelivered address. This
4528 means that if delivery of any address in the first message is successful, any
4529 existing retry information is deleted, and so delivery attempts for that
4530 address in subsequently selected messages (which are processed without forcing)
4531 will run. However, if delivery of any address does not succeed, the retry
4532 information is updated, and in subsequently selected messages, the failing
4533 address will be skipped.
4535 .cindex "frozen messages" "forcing delivery"
4536 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4537 all selected messages, not just the first; frozen messages are included when
4540 The &%-R%& option makes it straightforward to initiate delivery of all messages
4541 to a given domain after a host has been down for some time. When the SMTP
4542 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4543 effect is to run Exim with the &%-R%& option, but it can be configured to run
4544 an arbitrary command instead.
4548 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4550 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4552 .cindex "delivery" "from given sender"
4553 .cindex "queue runner" "for specific senders"
4554 This option acts like &%-R%& except that it checks the string against each
4555 message's sender instead of against the recipients. If &%-R%& is also set, both
4556 conditions must be met for a message to be selected. If either of the options
4557 has &'f'& or &'ff'& in its flags, the associated action is taken.
4559 .vitem &%-Tqt%&&~<&'times'&>
4561 This is an option that is exclusively for use by the Exim testing suite. It is not
4562 recognized when Exim is run normally. It allows for the setting up of explicit
4563 &"queue times"& so that various warning/retry features can be tested.
4567 .cindex "recipient" "extracting from header lines"
4568 .cindex "&'Bcc:'& header line"
4569 .cindex "&'Cc:'& header line"
4570 .cindex "&'To:'& header line"
4571 When Exim is receiving a locally-generated, non-SMTP message on its standard
4572 input, the &%-t%& option causes the recipients of the message to be obtained
4573 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4574 from the command arguments. The addresses are extracted before any rewriting
4575 takes place and the &'Bcc:'& header line, if present, is then removed.
4577 .cindex "Sendmail compatibility" "&%-t%& option"
4578 If the command has any arguments, they specify addresses to which the message
4579 is &'not'& to be delivered. That is, the argument addresses are removed from
4580 the recipients list obtained from the headers. This is compatible with Smail 3
4581 and in accordance with the documented behaviour of several versions of
4582 Sendmail, as described in man pages on a number of operating systems (e.g.
4583 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4584 argument addresses to those obtained from the headers, and the O'Reilly
4585 Sendmail book documents it that way. Exim can be made to add argument addresses
4586 instead of subtracting them by setting the option
4587 &%extract_addresses_remove_arguments%& false.
4589 .cindex "&%Resent-%& header lines" "with &%-t%&"
4590 If there are any &%Resent-%& header lines in the message, Exim extracts
4591 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4592 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4593 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4594 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4596 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4597 message is resent several times). The RFC also specifies that they should be
4598 added at the front of the message, and separated by &'Received:'& lines. It is
4599 not at all clear how &%-t%& should operate in the present of multiple sets,
4600 nor indeed exactly what constitutes a &"set"&.
4601 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4602 are often added at the end of the header, and if a message is resent more than
4603 once, it is common for the original set of &%Resent-%& headers to be renamed as
4604 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4608 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4609 compatibility with Sendmail.
4611 .vitem &%-tls-on-connect%&
4612 .oindex "&%-tls-on-connect%&"
4613 .cindex "TLS" "use without STARTTLS"
4614 .cindex "TLS" "automatic start"
4615 This option is available when Exim is compiled with TLS support. It forces all
4616 incoming SMTP connections to behave as if the incoming port is listed in the
4617 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4618 &<<CHAPTLS>>& for further details.
4623 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4624 Sendmail uses this option for &"initial message submission"&, and its
4625 documentation states that in future releases, it may complain about
4626 syntactically invalid messages rather than fixing them when this flag is not
4627 set. Exim ignores this option.
4631 This option causes Exim to write information to the standard error stream,
4632 describing what it is doing. In particular, it shows the log lines for
4633 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4634 dialogue is shown. Some of the log lines shown may not actually be written to
4635 the log if the setting of &%log_selector%& discards them. Any relevant
4636 selectors are shown with each log line. If none are shown, the logging is
4641 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4642 National Language Support extended characters in the body of the mail item"&).
4643 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4646 .vitem &%-X%&&~<&'logfile'&>
4648 This option is interpreted by Sendmail to cause debug information to be sent
4649 to the named file. It is ignored by Exim.
4651 .vitem &%-z%&&~<&'log-line'&>
4653 This option writes its argument to Exim's logfile.
4654 Use is restricted to administrators; the intent is for operational notes.
4655 Quotes should be used to maintain a multi-word item as a single argument,
4663 . ////////////////////////////////////////////////////////////////////////////
4664 . Insert a stylized DocBook comment here, to identify the end of the command
4665 . line options. This is for the benefit of the Perl script that automatically
4666 . creates a man page for the options.
4667 . ////////////////////////////////////////////////////////////////////////////
4670 <!-- === End of command line options === -->
4677 . ////////////////////////////////////////////////////////////////////////////
4678 . ////////////////////////////////////////////////////////////////////////////
4681 .chapter "The Exim run time configuration file" "CHAPconf" &&&
4682 "The runtime configuration file"
4684 .cindex "run time configuration"
4685 .cindex "configuration file" "general description"
4686 .cindex "CONFIGURE_FILE"
4687 .cindex "configuration file" "errors in"
4688 .cindex "error" "in configuration file"
4689 .cindex "return code" "for bad configuration"
4690 Exim uses a single run time configuration file that is read whenever an Exim
4691 binary is executed. Note that in normal operation, this happens frequently,
4692 because Exim is designed to operate in a distributed manner, without central
4695 If a syntax error is detected while reading the configuration file, Exim
4696 writes a message on the standard error, and exits with a non-zero return code.
4697 The message is also written to the panic log. &*Note*&: Only simple syntax
4698 errors can be detected at this time. The values of any expanded options are
4699 not checked until the expansion happens, even when the expansion does not
4700 actually alter the string.
4702 The name of the configuration file is compiled into the binary for security
4703 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4704 most configurations, this specifies a single file. However, it is permitted to
4705 give a colon-separated list of file names, in which case Exim uses the first
4706 existing file in the list.
4709 .cindex "EXIM_GROUP"
4710 .cindex "CONFIGURE_OWNER"
4711 .cindex "CONFIGURE_GROUP"
4712 .cindex "configuration file" "ownership"
4713 .cindex "ownership" "configuration file"
4714 The run time configuration file must be owned by root or by the user that is
4715 specified at compile time by the CONFIGURE_OWNER option (if set). The
4716 configuration file must not be world-writeable, or group-writeable unless its
4717 group is the root group or the one specified at compile time by the
4718 CONFIGURE_GROUP option.
4720 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4721 to root, anybody who is able to edit the run time configuration file has an
4722 easy way to run commands as root. If you specify a user or group in the
4723 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4724 who are members of that group will trivially be able to obtain root privileges.
4726 Up to Exim version 4.72, the run time configuration file was also permitted to
4727 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4728 since it offered a simple privilege escalation for any attacker who managed to
4729 compromise the Exim user account.
4731 A default configuration file, which will work correctly in simple situations,
4732 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4733 defines just one file name, the installation process copies the default
4734 configuration to a new file of that name if it did not previously exist. If
4735 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4736 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4741 .section "Using a different configuration file" "SECID40"
4742 .cindex "configuration file" "alternate"
4743 A one-off alternate configuration can be specified by the &%-C%& command line
4744 option, which may specify a single file or a list of files. However, when
4745 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4746 unless the argument for &%-C%& is identical to the built-in value from
4747 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4748 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4749 is useful mainly for checking the syntax of configuration files before
4750 installing them. No owner or group checks are done on a configuration file
4751 specified by &%-C%&, if root privilege has been dropped.
4753 Even the Exim user is not trusted to specify an arbitrary configuration file
4754 with the &%-C%& option to be used with root privileges, unless that file is
4755 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
4756 testing a configuration using &%-C%& right through message reception and
4757 delivery, even if the caller is root. The reception works, but by that time,
4758 Exim is running as the Exim user, so when it re-execs to regain privilege for
4759 the delivery, the use of &%-C%& causes privilege to be lost. However, root
4760 can test reception and delivery using two separate commands (one to put a
4761 message on the queue, using &%-odq%&, and another to do the delivery, using
4764 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4765 prefix string with which any file named in a &%-C%& command line option must
4766 start. In addition, the file name must not contain the sequence &"&`/../`&"&.
4767 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any file
4768 name can be used with &%-C%&.
4770 One-off changes to a configuration can be specified by the &%-D%& command line
4771 option, which defines and overrides values for macros used inside the
4772 configuration file. However, like &%-C%&, the use of this option by a
4773 non-privileged user causes Exim to discard its root privilege.
4774 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4775 completely disabled, and its use causes an immediate error exit.
4777 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
4778 to declare certain macro names trusted, such that root privilege will not
4779 necessarily be discarded.
4780 WHITELIST_D_MACROS defines a colon-separated list of macros which are
4781 considered safe and, if &%-D%& only supplies macros from this list, and the
4782 values are acceptable, then Exim will not give up root privilege if the caller
4783 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
4784 transition mechanism and is expected to be removed in the future. Acceptable
4785 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
4787 Some sites may wish to use the same Exim binary on different machines that
4788 share a file system, but to use different configuration files on each machine.
4789 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4790 looks for a file whose name is the configuration file name followed by a dot
4791 and the machine's node name, as obtained from the &[uname()]& function. If this
4792 file does not exist, the standard name is tried. This processing occurs for
4793 each file name in the list given by CONFIGURE_FILE or &%-C%&.
4795 In some esoteric situations different versions of Exim may be run under
4796 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4797 help with this. See the comments in &_src/EDITME_& for details.
4801 .section "Configuration file format" "SECTconffilfor"
4802 .cindex "configuration file" "format of"
4803 .cindex "format" "configuration file"
4804 Exim's configuration file is divided into a number of different parts. General
4805 option settings must always appear at the start of the file. The other parts
4806 are all optional, and may appear in any order. Each part other than the first
4807 is introduced by the word &"begin"& followed by at least one literal
4808 space, and the name of the part. The optional parts are:
4811 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
4814 .cindex "AUTH" "configuration"
4815 &'authenticators'&: Configuration settings for the authenticator drivers. These
4816 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4818 &'routers'&: Configuration settings for the router drivers. Routers process
4819 addresses and determine how the message is to be delivered (see chapters
4820 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
4822 &'transports'&: Configuration settings for the transport drivers. Transports
4823 define mechanisms for copying messages to destinations (see chapters
4824 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
4826 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
4827 If there is no retry section, or if it is empty (that is, no retry rules are
4828 defined), Exim will not retry deliveries. In this situation, temporary errors
4829 are treated the same as permanent errors. Retry rules are discussed in chapter
4832 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4833 when new addresses are generated during delivery. Rewriting is discussed in
4834 chapter &<<CHAPrewrite>>&.
4836 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4837 want to use this feature, you must set
4839 LOCAL_SCAN_HAS_OPTIONS=yes
4841 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
4842 facility are given in chapter &<<CHAPlocalscan>>&.
4845 .cindex "configuration file" "leading white space in"
4846 .cindex "configuration file" "trailing white space in"
4847 .cindex "white space" "in configuration file"
4848 Leading and trailing white space in configuration lines is always ignored.
4850 Blank lines in the file, and lines starting with a # character (ignoring
4851 leading white space) are treated as comments and are ignored. &*Note*&: A
4852 # character other than at the beginning of a line is not treated specially,
4853 and does not introduce a comment.
4855 Any non-comment line can be continued by ending it with a backslash. Note that
4856 the general rule for white space means that trailing white space after the
4857 backslash and leading white space at the start of continuation
4858 lines is ignored. Comment lines beginning with # (but not empty lines) may
4859 appear in the middle of a sequence of continuation lines.
4861 A convenient way to create a configuration file is to start from the
4862 default, which is supplied in &_src/configure.default_&, and add, delete, or
4863 change settings as required.
4865 The ACLs, retry rules, and rewriting rules have their own syntax which is
4866 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
4867 respectively. The other parts of the configuration file have some syntactic
4868 items in common, and these are described below, from section &<<SECTcos>>&
4869 onwards. Before that, the inclusion, macro, and conditional facilities are
4874 .section "File inclusions in the configuration file" "SECID41"
4875 .cindex "inclusions in configuration file"
4876 .cindex "configuration file" "including other files"
4877 .cindex "&`.include`& in configuration file"
4878 .cindex "&`.include_if_exists`& in configuration file"
4879 You can include other files inside Exim's run time configuration file by
4882 &`.include`& <&'file name'&>
4883 &`.include_if_exists`& <&'file name'&>
4885 on a line by itself. Double quotes round the file name are optional. If you use
4886 the first form, a configuration error occurs if the file does not exist; the
4887 second form does nothing for non-existent files. In all cases, an absolute file
4890 Includes may be nested to any depth, but remember that Exim reads its
4891 configuration file often, so it is a good idea to keep them to a minimum.
4892 If you change the contents of an included file, you must HUP the daemon,
4893 because an included file is read only when the configuration itself is read.
4895 The processing of inclusions happens early, at a physical line level, so, like
4896 comment lines, an inclusion can be used in the middle of an option setting,
4899 hosts_lookup = a.b.c \
4902 Include processing happens after macro processing (see below). Its effect is to
4903 process the lines of the included file as if they occurred inline where the
4908 .section "Macros in the configuration file" "SECTmacrodefs"
4909 .cindex "macro" "description of"
4910 .cindex "configuration file" "macros"
4911 If a line in the main part of the configuration (that is, before the first
4912 &"begin"& line) begins with an upper case letter, it is taken as a macro
4913 definition, and must be of the form
4915 <&'name'&> = <&'rest of line'&>
4917 The name must consist of letters, digits, and underscores, and need not all be
4918 in upper case, though that is recommended. The rest of the line, including any
4919 continuations, is the replacement text, and has leading and trailing white
4920 space removed. Quotes are not removed. The replacement text can never end with
4921 a backslash character, but this doesn't seem to be a serious limitation.
4923 Macros may also be defined between router, transport, authenticator, or ACL
4924 definitions. They may not, however, be defined within an individual driver or
4925 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
4927 .section "Macro substitution" "SECID42"
4928 Once a macro is defined, all subsequent lines in the file (and any included
4929 files) are scanned for the macro name; if there are several macros, the line is
4930 scanned for each in turn, in the order in which the macros are defined. The
4931 replacement text is not re-scanned for the current macro, though it is scanned
4932 for subsequently defined macros. For this reason, a macro name may not contain
4933 the name of a previously defined macro as a substring. You could, for example,
4936 &`ABCD_XYZ = `&<&'something'&>
4937 &`ABCD = `&<&'something else'&>
4939 but putting the definitions in the opposite order would provoke a configuration
4940 error. Macro expansion is applied to individual physical lines from the file,
4941 before checking for line continuation or file inclusion (see above). If a line
4942 consists solely of a macro name, and the expansion of the macro is empty, the
4943 line is ignored. A macro at the start of a line may turn the line into a
4944 comment line or a &`.include`& line.
4947 .section "Redefining macros" "SECID43"
4948 Once defined, the value of a macro can be redefined later in the configuration
4949 (or in an included file). Redefinition is specified by using &'=='& instead of
4954 MAC == updated value
4956 Redefinition does not alter the order in which the macros are applied to the
4957 subsequent lines of the configuration file. It is still the same order in which
4958 the macros were originally defined. All that changes is the macro's value.
4959 Redefinition makes it possible to accumulate values. For example:
4963 MAC == MAC and something added
4965 This can be helpful in situations where the configuration file is built
4966 from a number of other files.
4968 .section "Overriding macro values" "SECID44"
4969 The values set for macros in the configuration file can be overridden by the
4970 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
4971 used, unless called by root or the Exim user. A definition on the command line
4972 using the &%-D%& option causes all definitions and redefinitions within the
4977 .section "Example of macro usage" "SECID45"
4978 As an example of macro usage, consider a configuration where aliases are looked
4979 up in a MySQL database. It helps to keep the file less cluttered if long
4980 strings such as SQL statements are defined separately as macros, for example:
4982 ALIAS_QUERY = select mailbox from user where \
4983 login='${quote_mysql:$local_part}';
4985 This can then be used in a &(redirect)& router setting like this:
4987 data = ${lookup mysql{ALIAS_QUERY}}
4989 In earlier versions of Exim macros were sometimes used for domain, host, or
4990 address lists. In Exim 4 these are handled better by named lists &-- see
4991 section &<<SECTnamedlists>>&.
4994 .section "Conditional skips in the configuration file" "SECID46"
4995 .cindex "configuration file" "conditional skips"
4996 .cindex "&`.ifdef`&"
4997 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
4998 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
4999 portions of the configuration file. The processing happens whenever the file is
5000 read (that is, when an Exim binary starts to run).
5002 The implementation is very simple. Instances of the first four directives must
5003 be followed by text that includes the names of one or macros. The condition
5004 that is tested is whether or not any macro substitution has taken place in the
5008 message_size_limit = 50M
5010 message_size_limit = 100M
5013 sets a message size limit of 50M if the macro &`AAA`& is defined
5014 (or &`A`& or &`AA`&), and 100M
5015 otherwise. If there is more than one macro named on the line, the condition
5016 is true if any of them are defined. That is, it is an &"or"& condition. To
5017 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5019 Although you can use a macro expansion to generate one of these directives,
5020 it is not very useful, because the condition &"there was a macro substitution
5021 in this line"& will always be true.
5023 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5024 to clarify complicated nestings.
5028 .section "Common option syntax" "SECTcos"
5029 .cindex "common option syntax"
5030 .cindex "syntax of common options"
5031 .cindex "configuration file" "common option syntax"
5032 For the main set of options, driver options, and &[local_scan()]& options,
5033 each setting is on a line by itself, and starts with a name consisting of
5034 lower-case letters and underscores. Many options require a data value, and in
5035 these cases the name must be followed by an equals sign (with optional white
5036 space) and then the value. For example:
5038 qualify_domain = mydomain.example.com
5040 .cindex "hiding configuration option values"
5041 .cindex "configuration options" "hiding value of"
5042 .cindex "options" "hiding value of"
5043 Some option settings may contain sensitive data, for example, passwords for
5044 accessing databases. To stop non-admin users from using the &%-bP%& command
5045 line option to read these values, you can precede the option settings with the
5046 word &"hide"&. For example:
5048 hide mysql_servers = localhost/users/admin/secret-password
5050 For non-admin users, such options are displayed like this:
5052 mysql_servers = <value not displayable>
5054 If &"hide"& is used on a driver option, it hides the value of that option on
5055 all instances of the same driver.
5057 The following sections describe the syntax used for the different data types
5058 that are found in option settings.
5061 .section "Boolean options" "SECID47"
5062 .cindex "format" "boolean"
5063 .cindex "boolean configuration values"
5064 .oindex "&%no_%&&'xxx'&"
5065 .oindex "&%not_%&&'xxx'&"
5066 Options whose type is given as boolean are on/off switches. There are two
5067 different ways of specifying such options: with and without a data value. If
5068 the option name is specified on its own without data, the switch is turned on;
5069 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5070 boolean options may be followed by an equals sign and one of the words
5071 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5072 the following two settings have exactly the same effect:
5077 The following two lines also have the same (opposite) effect:
5082 You can use whichever syntax you prefer.
5087 .section "Integer values" "SECID48"
5088 .cindex "integer configuration values"
5089 .cindex "format" "integer"
5090 If an option's type is given as &"integer"&, the value can be given in decimal,
5091 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5092 number is assumed. Otherwise, it is treated as an octal number unless it starts
5093 with the characters &"0x"&, in which case the remainder is interpreted as a
5096 If an integer value is followed by the letter K, it is multiplied by 1024; if
5097 it is followed by the letter M, it is multiplied by 1024x1024. When the values
5098 of integer option settings are output, values which are an exact multiple of
5099 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5100 and M. The printing style is independent of the actual input format that was
5104 .section "Octal integer values" "SECID49"
5105 .cindex "integer format"
5106 .cindex "format" "octal integer"
5107 If an option's type is given as &"octal integer"&, its value is always
5108 interpreted as an octal number, whether or not it starts with the digit zero.
5109 Such options are always output in octal.
5112 .section "Fixed point numbers" "SECID50"
5113 .cindex "fixed point configuration values"
5114 .cindex "format" "fixed point"
5115 If an option's type is given as &"fixed-point"&, its value must be a decimal
5116 integer, optionally followed by a decimal point and up to three further digits.
5120 .section "Time intervals" "SECTtimeformat"
5121 .cindex "time interval" "specifying in configuration"
5122 .cindex "format" "time interval"
5123 A time interval is specified as a sequence of numbers, each followed by one of
5124 the following letters, with no intervening white space:
5134 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5135 intervals are output in the same format. Exim does not restrict the values; it
5136 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5140 .section "String values" "SECTstrings"
5141 .cindex "string" "format of configuration values"
5142 .cindex "format" "string"
5143 If an option's type is specified as &"string"&, the value can be specified with
5144 or without double-quotes. If it does not start with a double-quote, the value
5145 consists of the remainder of the line plus any continuation lines, starting at
5146 the first character after any leading white space, with trailing white space
5147 removed, and with no interpretation of the characters in the string. Because
5148 Exim removes comment lines (those beginning with #) at an early stage, they can
5149 appear in the middle of a multi-line string. The following two settings are
5150 therefore equivalent:
5152 trusted_users = uucp:mail
5153 trusted_users = uucp:\
5154 # This comment line is ignored
5157 .cindex "string" "quoted"
5158 .cindex "escape characters in quoted strings"
5159 If a string does start with a double-quote, it must end with a closing
5160 double-quote, and any backslash characters other than those used for line
5161 continuation are interpreted as escape characters, as follows:
5164 .irow &`\\`& "single backslash"
5165 .irow &`\n`& "newline"
5166 .irow &`\r`& "carriage return"
5168 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5169 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5173 If a backslash is followed by some other character, including a double-quote
5174 character, that character replaces the pair.
5176 Quoting is necessary only if you want to make use of the backslash escapes to
5177 insert special characters, or if you need to specify a value with leading or
5178 trailing spaces. These cases are rare, so quoting is almost never needed in
5179 current versions of Exim. In versions of Exim before 3.14, quoting was required
5180 in order to continue lines, so you may come across older configuration files
5181 and examples that apparently quote unnecessarily.
5184 .section "Expanded strings" "SECID51"
5185 .cindex "expansion" "definition of"
5186 Some strings in the configuration file are subjected to &'string expansion'&,
5187 by which means various parts of the string may be changed according to the
5188 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5189 is as just described; in particular, the handling of backslashes in quoted
5190 strings is done as part of the input process, before expansion takes place.
5191 However, backslash is also an escape character for the expander, so any
5192 backslashes that are required for that reason must be doubled if they are
5193 within a quoted configuration string.
5196 .section "User and group names" "SECID52"
5197 .cindex "user name" "format of"
5198 .cindex "format" "user name"
5199 .cindex "groups" "name format"
5200 .cindex "format" "group name"
5201 User and group names are specified as strings, using the syntax described
5202 above, but the strings are interpreted specially. A user or group name must
5203 either consist entirely of digits, or be a name that can be looked up using the
5204 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5207 .section "List construction" "SECTlistconstruct"
5208 .cindex "list" "syntax of in configuration"
5209 .cindex "format" "list item in configuration"
5210 .cindex "string" "list, definition of"
5211 The data for some configuration options is a list of items, with colon as the
5212 default separator. Many of these options are shown with type &"string list"& in
5213 the descriptions later in this document. Others are listed as &"domain list"&,
5214 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5215 are all the same; however, those other than &"string list"& are subject to
5216 particular kinds of interpretation, as described in chapter
5217 &<<CHAPdomhosaddlists>>&.
5219 In all these cases, the entire list is treated as a single string as far as the
5220 input syntax is concerned. The &%trusted_users%& setting in section
5221 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5222 in a list, it must be entered as two colons. Leading and trailing white space
5223 on each item in a list is ignored. This makes it possible to include items that
5224 start with a colon, and in particular, certain forms of IPv6 address. For
5227 local_interfaces = 127.0.0.1 : ::::1
5229 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5231 &*Note*&: Although leading and trailing white space is ignored in individual
5232 list items, it is not ignored when parsing the list. The space after the first
5233 colon in the example above is necessary. If it were not there, the list would
5234 be interpreted as the two items 127.0.0.1:: and 1.
5236 .section "Changing list separators" "SECTlistsepchange"
5237 .cindex "list separator" "changing"
5238 .cindex "IPv6" "addresses in lists"
5239 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5240 introduced to allow the separator character to be changed. If a list begins
5241 with a left angle bracket, followed by any punctuation character, that
5242 character is used instead of colon as the list separator. For example, the list
5243 above can be rewritten to use a semicolon separator like this:
5245 local_interfaces = <; 127.0.0.1 ; ::1
5247 This facility applies to all lists, with the exception of the list in
5248 &%log_file_path%&. It is recommended that the use of non-colon separators be
5249 confined to circumstances where they really are needed.
5251 .cindex "list separator" "newline as"
5252 .cindex "newline" "as list separator"
5253 It is also possible to use newline and other control characters (those with
5254 code values less than 32, plus DEL) as separators in lists. Such separators
5255 must be provided literally at the time the list is processed. For options that
5256 are string-expanded, you can write the separator using a normal escape
5257 sequence. This will be processed by the expander before the string is
5258 interpreted as a list. For example, if a newline-separated list of domains is
5259 generated by a lookup, you can process it directly by a line such as this:
5261 domains = <\n ${lookup mysql{.....}}
5263 This avoids having to change the list separator in such data. You are unlikely
5264 to want to use a control character as a separator in an option that is not
5265 expanded, because the value is literal text. However, it can be done by giving
5266 the value in quotes. For example:
5268 local_interfaces = "<\n 127.0.0.1 \n ::1"
5270 Unlike printing character separators, which can be included in list items by
5271 doubling, it is not possible to include a control character as data when it is
5272 set as the separator. Two such characters in succession are interpreted as
5273 enclosing an empty list item.
5277 .section "Empty items in lists" "SECTempitelis"
5278 .cindex "list" "empty item in"
5279 An empty item at the end of a list is always ignored. In other words, trailing
5280 separator characters are ignored. Thus, the list in
5282 senders = user@domain :
5284 contains only a single item. If you want to include an empty string as one item
5285 in a list, it must not be the last item. For example, this list contains three
5286 items, the second of which is empty:
5288 senders = user1@domain : : user2@domain
5290 &*Note*&: There must be white space between the two colons, as otherwise they
5291 are interpreted as representing a single colon data character (and the list
5292 would then contain just one item). If you want to specify a list that contains
5293 just one, empty item, you can do it as in this example:
5297 In this case, the first item is empty, and the second is discarded because it
5298 is at the end of the list.
5303 .section "Format of driver configurations" "SECTfordricon"
5304 .cindex "drivers" "configuration format"
5305 There are separate parts in the configuration for defining routers, transports,
5306 and authenticators. In each part, you are defining a number of driver
5307 instances, each with its own set of options. Each driver instance is defined by
5308 a sequence of lines like this:
5310 <&'instance name'&>:
5315 In the following example, the instance name is &(localuser)&, and it is
5316 followed by three options settings:
5321 transport = local_delivery
5323 For each driver instance, you specify which Exim code module it uses &-- by the
5324 setting of the &%driver%& option &-- and (optionally) some configuration
5325 settings. For example, in the case of transports, if you want a transport to
5326 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5327 a local file you would use the &(appendfile)& driver. Each of the drivers is
5328 described in detail in its own separate chapter later in this manual.
5330 You can have several routers, transports, or authenticators that are based on
5331 the same underlying driver (each must have a different instance name).
5333 The order in which routers are defined is important, because addresses are
5334 passed to individual routers one by one, in order. The order in which
5335 transports are defined does not matter at all. The order in which
5336 authenticators are defined is used only when Exim, as a client, is searching
5337 them to find one that matches an authentication mechanism offered by the
5340 .cindex "generic options"
5341 .cindex "options" "generic &-- definition of"
5342 Within a driver instance definition, there are two kinds of option: &'generic'&
5343 and &'private'&. The generic options are those that apply to all drivers of the
5344 same type (that is, all routers, all transports or all authenticators). The
5345 &%driver%& option is a generic option that must appear in every definition.
5346 .cindex "private options"
5347 The private options are special for each driver, and none need appear, because
5348 they all have default values.
5350 The options may appear in any order, except that the &%driver%& option must
5351 precede any private options, since these depend on the particular driver. For
5352 this reason, it is recommended that &%driver%& always be the first option.
5354 Driver instance names, which are used for reference in log entries and
5355 elsewhere, can be any sequence of letters, digits, and underscores (starting
5356 with a letter) and must be unique among drivers of the same type. A router and
5357 a transport (for example) can each have the same name, but no two router
5358 instances can have the same name. The name of a driver instance should not be
5359 confused with the name of the underlying driver module. For example, the
5360 configuration lines:
5365 create an instance of the &(smtp)& transport driver whose name is
5366 &(remote_smtp)&. The same driver code can be used more than once, with
5367 different instance names and different option settings each time. A second
5368 instance of the &(smtp)& transport, with different options, might be defined
5374 command_timeout = 10s
5376 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5377 these transport instances from routers, and these names would appear in log
5380 Comment lines may be present in the middle of driver specifications. The full
5381 list of option settings for any particular driver instance, including all the
5382 defaulted values, can be extracted by making use of the &%-bP%& command line
5390 . ////////////////////////////////////////////////////////////////////////////
5391 . ////////////////////////////////////////////////////////////////////////////
5393 .chapter "The default configuration file" "CHAPdefconfil"
5394 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5395 .cindex "default" "configuration file &""walk through""&"
5396 The default configuration file supplied with Exim as &_src/configure.default_&
5397 is sufficient for a host with simple mail requirements. As an introduction to
5398 the way Exim is configured, this chapter &"walks through"& the default
5399 configuration, giving brief explanations of the settings. Detailed descriptions
5400 of the options are given in subsequent chapters. The default configuration file
5401 itself contains extensive comments about ways you might want to modify the
5402 initial settings. However, note that there are many options that are not
5403 mentioned at all in the default configuration.
5407 .section "Main configuration settings" "SECTdefconfmain"
5408 The main (global) configuration option settings must always come first in the
5409 file. The first thing you'll see in the file, after some initial comments, is
5412 # primary_hostname =
5414 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5415 to know the official, fully qualified name of your host, and this is where you
5416 can specify it. However, in most cases you do not need to set this option. When
5417 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5419 The first three non-comment configuration lines are as follows:
5421 domainlist local_domains = @
5422 domainlist relay_to_domains =
5423 hostlist relay_from_hosts = 127.0.0.1
5425 These are not, in fact, option settings. They are definitions of two named
5426 domain lists and one named host list. Exim allows you to give names to lists of
5427 domains, hosts, and email addresses, in order to make it easier to manage the
5428 configuration file (see section &<<SECTnamedlists>>&).
5430 The first line defines a domain list called &'local_domains'&; this is used
5431 later in the configuration to identify domains that are to be delivered
5434 .cindex "@ in a domain list"
5435 There is just one item in this list, the string &"@"&. This is a special form
5436 of entry which means &"the name of the local host"&. Thus, if the local host is
5437 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5438 be delivered locally. Because the local host's name is referenced indirectly,
5439 the same configuration file can be used on different hosts.
5441 The second line defines a domain list called &'relay_to_domains'&, but the
5442 list itself is empty. Later in the configuration we will come to the part that
5443 controls mail relaying through the local host; it allows relaying to any
5444 domains in this list. By default, therefore, no relaying on the basis of a mail
5445 domain is permitted.
5447 The third line defines a host list called &'relay_from_hosts'&. This list is
5448 used later in the configuration to permit relaying from any host or IP address
5449 that matches the list. The default contains just the IP address of the IPv4
5450 loopback interface, which means that processes on the local host are able to
5451 submit mail for relaying by sending it over TCP/IP to that interface. No other
5452 hosts are permitted to submit messages for relaying.
5454 Just to be sure there's no misunderstanding: at this point in the configuration
5455 we aren't actually setting up any controls. We are just defining some domains
5456 and hosts that will be used in the controls that are specified later.
5458 The next two configuration lines are genuine option settings:
5460 acl_smtp_rcpt = acl_check_rcpt
5461 acl_smtp_data = acl_check_data
5463 These options specify &'Access Control Lists'& (ACLs) that are to be used
5464 during an incoming SMTP session for every recipient of a message (every RCPT
5465 command), and after the contents of the message have been received,
5466 respectively. The names of the lists are &'acl_check_rcpt'& and
5467 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5468 section of the configuration. The RCPT ACL controls which recipients are
5469 accepted for an incoming message &-- if a configuration does not provide an ACL
5470 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5471 contents of a message to be checked.
5473 Two commented-out option settings are next:
5475 # av_scanner = clamd:/tmp/clamd
5476 # spamd_address = 127.0.0.1 783
5478 These are example settings that can be used when Exim is compiled with the
5479 content-scanning extension. The first specifies the interface to the virus
5480 scanner, and the second specifies the interface to SpamAssassin. Further
5481 details are given in chapter &<<CHAPexiscan>>&.
5483 Three more commented-out option settings follow:
5485 # tls_advertise_hosts = *
5486 # tls_certificate = /etc/ssl/exim.crt
5487 # tls_privatekey = /etc/ssl/exim.pem
5489 These are example settings that can be used when Exim is compiled with
5490 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5491 first one specifies the list of clients that are allowed to use TLS when
5492 connecting to this server; in this case the wildcard means all clients. The
5493 other options specify where Exim should find its TLS certificate and private
5494 key, which together prove the server's identity to any clients that connect.
5495 More details are given in chapter &<<CHAPTLS>>&.
5497 Another two commented-out option settings follow:
5499 # daemon_smtp_ports = 25 : 465 : 587
5500 # tls_on_connect_ports = 465
5502 .cindex "port" "465 and 587"
5503 .cindex "port" "for message submission"
5504 .cindex "message" "submission, ports for"
5505 .cindex "ssmtp protocol"
5506 .cindex "smtps protocol"
5507 .cindex "SMTP" "ssmtp protocol"
5508 .cindex "SMTP" "smtps protocol"
5509 These options provide better support for roaming users who wish to use this
5510 server for message submission. They are not much use unless you have turned on
5511 TLS (as described in the previous paragraph) and authentication (about which
5512 more in section &<<SECTdefconfauth>>&). The usual SMTP port 25 is often blocked
5513 on end-user networks, so RFC 4409 specifies that message submission should use
5514 port 587 instead. However some software (notably Microsoft Outlook) cannot be
5515 configured to use port 587 correctly, so these settings also enable the
5516 non-standard &"smtps"& (aka &"ssmtp"&) port 465 (see section
5517 &<<SECTsupobssmt>>&).
5519 Two more commented-out options settings follow:
5522 # qualify_recipient =
5524 The first of these specifies a domain that Exim uses when it constructs a
5525 complete email address from a local login name. This is often needed when Exim
5526 receives a message from a local process. If you do not set &%qualify_domain%&,
5527 the value of &%primary_hostname%& is used. If you set both of these options,
5528 you can have different qualification domains for sender and recipient
5529 addresses. If you set only the first one, its value is used in both cases.
5531 .cindex "domain literal" "recognizing format"
5532 The following line must be uncommented if you want Exim to recognize
5533 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5534 (an IP address within square brackets) instead of a named domain.
5536 # allow_domain_literals
5538 The RFCs still require this form, but many people think that in the modern
5539 Internet it makes little sense to permit mail to be sent to specific hosts by
5540 quoting their IP addresses. This ancient format has been used by people who
5541 try to abuse hosts by using them for unwanted relaying. However, some
5542 people believe there are circumstances (for example, messages addressed to
5543 &'postmaster'&) where domain literals are still useful.
5545 The next configuration line is a kind of trigger guard:
5549 It specifies that no delivery must ever be run as the root user. The normal
5550 convention is to set up &'root'& as an alias for the system administrator. This
5551 setting is a guard against slips in the configuration.
5552 The list of users specified by &%never_users%& is not, however, the complete
5553 list; the build-time configuration in &_Local/Makefile_& has an option called
5554 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5555 contents of &%never_users%& are added to this list. By default
5556 FIXED_NEVER_USERS also specifies root.
5558 When a remote host connects to Exim in order to send mail, the only information
5559 Exim has about the host's identity is its IP address. The next configuration
5564 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5565 in order to get a host name. This improves the quality of the logging
5566 information, but if you feel it is too expensive, you can remove it entirely,
5567 or restrict the lookup to hosts on &"nearby"& networks.
5568 Note that it is not always possible to find a host name from an IP address,
5569 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5572 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5573 1413 (hence their names):
5576 rfc1413_query_timeout = 0s
5578 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5579 Few hosts offer RFC1413 service these days; calls have to be
5580 terminated by a timeout and this needlessly delays the startup
5581 of an incoming SMTP connection.
5582 If you have hosts for which you trust RFC1413 and need this
5583 information, you can change this.
5585 This line enables an efficiency SMTP option. It is negotiated by clients
5586 and not expected to cause problems but can be disabled if needed.
5591 When Exim receives messages over SMTP connections, it expects all addresses to
5592 be fully qualified with a domain, as required by the SMTP definition. However,
5593 if you are running a server to which simple clients submit messages, you may
5594 find that they send unqualified addresses. The two commented-out options:
5596 # sender_unqualified_hosts =
5597 # recipient_unqualified_hosts =
5599 show how you can specify hosts that are permitted to send unqualified sender
5600 and recipient addresses, respectively.
5602 The &%log_selector%& option is used to increase the detail of logging
5605 log_selector = +smtp_protocol_error +smtp_syntax_error \
5606 +tls_certificate_verified
5609 The &%percent_hack_domains%& option is also commented out:
5611 # percent_hack_domains =
5613 It provides a list of domains for which the &"percent hack"& is to operate.
5614 This is an almost obsolete form of explicit email routing. If you do not know
5615 anything about it, you can safely ignore this topic.
5617 The last two settings in the main part of the default configuration are
5618 concerned with messages that have been &"frozen"& on Exim's queue. When a
5619 message is frozen, Exim no longer continues to try to deliver it. Freezing
5620 occurs when a bounce message encounters a permanent failure because the sender
5621 address of the original message that caused the bounce is invalid, so the
5622 bounce cannot be delivered. This is probably the most common case, but there
5623 are also other conditions that cause freezing, and frozen messages are not
5624 always bounce messages.
5626 ignore_bounce_errors_after = 2d
5627 timeout_frozen_after = 7d
5629 The first of these options specifies that failing bounce messages are to be
5630 discarded after 2 days on the queue. The second specifies that any frozen
5631 message (whether a bounce message or not) is to be timed out (and discarded)
5632 after a week. In this configuration, the first setting ensures that no failing
5633 bounce message ever lasts a week.
5637 .section "ACL configuration" "SECID54"
5638 .cindex "default" "ACLs"
5639 .cindex "&ACL;" "default configuration"
5640 In the default configuration, the ACL section follows the main configuration.
5641 It starts with the line
5645 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5646 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5647 and &%acl_smtp_data%& above.
5649 .cindex "RCPT" "ACL for"
5650 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5651 RCPT command specifies one of the message's recipients. The ACL statements
5652 are considered in order, until the recipient address is either accepted or
5653 rejected. The RCPT command is then accepted or rejected, according to the
5654 result of the ACL processing.
5658 This line, consisting of a name terminated by a colon, marks the start of the
5663 This ACL statement accepts the recipient if the sending host matches the list.
5664 But what does that strange list mean? It doesn't actually contain any host
5665 names or IP addresses. The presence of the colon puts an empty item in the
5666 list; Exim matches this only if the incoming message did not come from a remote
5667 host, because in that case, the remote hostname is empty. The colon is
5668 important. Without it, the list itself is empty, and can never match anything.
5670 What this statement is doing is to accept unconditionally all recipients in
5671 messages that are submitted by SMTP from local processes using the standard
5672 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5675 deny message = Restricted characters in address
5676 domains = +local_domains
5677 local_parts = ^[.] : ^.*[@%!/|]
5679 deny message = Restricted characters in address
5680 domains = !+local_domains
5681 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5683 These statements are concerned with local parts that contain any of the
5684 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5685 Although these characters are entirely legal in local parts (in the case of
5686 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5687 in Internet mail addresses.
5689 The first three have in the past been associated with explicitly routed
5690 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5691 option). Addresses containing these characters are regularly tried by spammers
5692 in an attempt to bypass relaying restrictions, and also by open relay testing
5693 programs. Unless you really need them it is safest to reject these characters
5694 at this early stage. This configuration is heavy-handed in rejecting these
5695 characters for all messages it accepts from remote hosts. This is a deliberate
5696 policy of being as safe as possible.
5698 The first rule above is stricter, and is applied to messages that are addressed
5699 to one of the local domains handled by this host. This is implemented by the
5700 first condition, which restricts it to domains that are listed in the
5701 &'local_domains'& domain list. The &"+"& character is used to indicate a
5702 reference to a named list. In this configuration, there is just one domain in
5703 &'local_domains'&, but in general there may be many.
5705 The second condition on the first statement uses two regular expressions to
5706 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5707 or &"|"&. If you have local accounts that include these characters, you will
5708 have to modify this rule.
5710 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5711 allows them because they have been encountered in practice. (Consider the
5712 common convention of local parts constructed as
5713 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5714 the author of Exim, who has no second initial.) However, a local part starting
5715 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5716 file name (for example, for a mailing list). This is also true for local parts
5717 that contain slashes. A pipe symbol can also be troublesome if the local part
5718 is incorporated unthinkingly into a shell command line.
5720 The second rule above applies to all other domains, and is less strict. This
5721 allows your own users to send outgoing messages to sites that use slashes
5722 and vertical bars in their local parts. It blocks local parts that begin
5723 with a dot, slash, or vertical bar, but allows these characters within the
5724 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5725 and &"!"& is blocked, as before. The motivation here is to prevent your users
5726 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5728 accept local_parts = postmaster
5729 domains = +local_domains
5731 This statement, which has two conditions, accepts an incoming address if the
5732 local part is &'postmaster'& and the domain is one of those listed in the
5733 &'local_domains'& domain list. The &"+"& character is used to indicate a
5734 reference to a named list. In this configuration, there is just one domain in
5735 &'local_domains'&, but in general there may be many.
5737 The presence of this statement means that mail to postmaster is never blocked
5738 by any of the subsequent tests. This can be helpful while sorting out problems
5739 in cases where the subsequent tests are incorrectly denying access.
5741 require verify = sender
5743 This statement requires the sender address to be verified before any subsequent
5744 ACL statement can be used. If verification fails, the incoming recipient
5745 address is refused. Verification consists of trying to route the address, to
5746 see if a bounce message could be delivered to it. In the case of remote
5747 addresses, basic verification checks only the domain, but &'callouts'& can be
5748 used for more verification if required. Section &<<SECTaddressverification>>&
5749 discusses the details of address verification.
5751 accept hosts = +relay_from_hosts
5752 control = submission
5754 This statement accepts the address if the message is coming from one of the
5755 hosts that are defined as being allowed to relay through this host. Recipient
5756 verification is omitted here, because in many cases the clients are dumb MUAs
5757 that do not cope well with SMTP error responses. For the same reason, the
5758 second line specifies &"submission mode"& for messages that are accepted. This
5759 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
5760 messages that are deficient in some way, for example, because they lack a
5761 &'Date:'& header line. If you are actually relaying out from MTAs, you should
5762 probably add recipient verification here, and disable submission mode.
5764 accept authenticated = *
5765 control = submission
5767 This statement accepts the address if the client host has authenticated itself.
5768 Submission mode is again specified, on the grounds that such messages are most
5769 likely to come from MUAs. The default configuration does not define any
5770 authenticators, though it does include some nearly complete commented-out
5771 examples described in &<<SECTdefconfauth>>&. This means that no client can in
5772 fact authenticate until you complete the authenticator definitions.
5774 require message = relay not permitted
5775 domains = +local_domains : +relay_to_domains
5777 This statement rejects the address if its domain is neither a local domain nor
5778 one of the domains for which this host is a relay.
5780 require verify = recipient
5782 This statement requires the recipient address to be verified; if verification
5783 fails, the address is rejected.
5785 # deny message = rejected because $sender_host_address \
5786 # is in a black list at $dnslist_domain\n\
5788 # dnslists = black.list.example
5790 # warn dnslists = black.list.example
5791 # add_header = X-Warning: $sender_host_address is in \
5792 # a black list at $dnslist_domain
5793 # log_message = found in $dnslist_domain
5795 These commented-out lines are examples of how you could configure Exim to check
5796 sending hosts against a DNS black list. The first statement rejects messages
5797 from blacklisted hosts, whereas the second just inserts a warning header
5800 # require verify = csa
5802 This commented-out line is an example of how you could turn on client SMTP
5803 authorization (CSA) checking. Such checks do DNS lookups for special SRV
5808 The final statement in the first ACL unconditionally accepts any recipient
5809 address that has successfully passed all the previous tests.
5813 This line marks the start of the second ACL, and names it. Most of the contents
5814 of this ACL are commented out:
5817 # message = This message contains a virus \
5820 These lines are examples of how to arrange for messages to be scanned for
5821 viruses when Exim has been compiled with the content-scanning extension, and a
5822 suitable virus scanner is installed. If the message is found to contain a
5823 virus, it is rejected with the given custom error message.
5825 # warn spam = nobody
5826 # message = X-Spam_score: $spam_score\n\
5827 # X-Spam_score_int: $spam_score_int\n\
5828 # X-Spam_bar: $spam_bar\n\
5829 # X-Spam_report: $spam_report
5831 These lines are an example of how to arrange for messages to be scanned by
5832 SpamAssassin when Exim has been compiled with the content-scanning extension,
5833 and SpamAssassin has been installed. The SpamAssassin check is run with
5834 &`nobody`& as its user parameter, and the results are added to the message as a
5835 series of extra header line. In this case, the message is not rejected,
5836 whatever the spam score.
5840 This final line in the DATA ACL accepts the message unconditionally.
5843 .section "Router configuration" "SECID55"
5844 .cindex "default" "routers"
5845 .cindex "routers" "default"
5846 The router configuration comes next in the default configuration, introduced
5851 Routers are the modules in Exim that make decisions about where to send
5852 messages. An address is passed to each router in turn, until it is either
5853 accepted, or failed. This means that the order in which you define the routers
5854 matters. Each router is fully described in its own chapter later in this
5855 manual. Here we give only brief overviews.
5858 # driver = ipliteral
5859 # domains = !+local_domains
5860 # transport = remote_smtp
5862 .cindex "domain literal" "default router"
5863 This router is commented out because the majority of sites do not want to
5864 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
5865 you uncomment this router, you also need to uncomment the setting of
5866 &%allow_domain_literals%& in the main part of the configuration.
5870 domains = ! +local_domains
5871 transport = remote_smtp
5872 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
5875 The first uncommented router handles addresses that do not involve any local
5876 domains. This is specified by the line
5878 domains = ! +local_domains
5880 The &%domains%& option lists the domains to which this router applies, but the
5881 exclamation mark is a negation sign, so the router is used only for domains
5882 that are not in the domain list called &'local_domains'& (which was defined at
5883 the start of the configuration). The plus sign before &'local_domains'&
5884 indicates that it is referring to a named list. Addresses in other domains are
5885 passed on to the following routers.
5887 The name of the router driver is &(dnslookup)&,
5888 and is specified by the &%driver%& option. Do not be confused by the fact that
5889 the name of this router instance is the same as the name of the driver. The
5890 instance name is arbitrary, but the name set in the &%driver%& option must be
5891 one of the driver modules that is in the Exim binary.
5893 The &(dnslookup)& router routes addresses by looking up their domains in the
5894 DNS in order to obtain a list of hosts to which the address is routed. If the
5895 router succeeds, the address is queued for the &(remote_smtp)& transport, as
5896 specified by the &%transport%& option. If the router does not find the domain
5897 in the DNS, no further routers are tried because of the &%no_more%& setting, so
5898 the address fails and is bounced.
5900 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
5901 be entirely ignored. This option is present because a number of cases have been
5902 encountered where MX records in the DNS point to host names
5903 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
5904 Completely ignoring these IP addresses causes Exim to fail to route the
5905 email address, so it bounces. Otherwise, Exim would log a routing problem, and
5906 continue to try to deliver the message periodically until the address timed
5913 data = ${lookup{$local_part}lsearch{/etc/aliases}}
5915 file_transport = address_file
5916 pipe_transport = address_pipe
5918 Control reaches this and subsequent routers only for addresses in the local
5919 domains. This router checks to see whether the local part is defined as an
5920 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
5921 data that it looks up from that file. If no data is found for the local part,
5922 the value of the &%data%& option is empty, causing the address to be passed to
5925 &_/etc/aliases_& is a conventional name for the system aliases file that is
5926 often used. That is why it is referenced by from the default configuration
5927 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
5928 &_Local/Makefile_& before building Exim.
5933 # local_part_suffix = +* : -*
5934 # local_part_suffix_optional
5935 file = $home/.forward
5940 file_transport = address_file
5941 pipe_transport = address_pipe
5942 reply_transport = address_reply
5944 This is the most complicated router in the default configuration. It is another
5945 redirection router, but this time it is looking for forwarding data set up by
5946 individual users. The &%check_local_user%& setting specifies a check that the
5947 local part of the address is the login name of a local user. If it is not, the
5948 router is skipped. The two commented options that follow &%check_local_user%&,
5951 # local_part_suffix = +* : -*
5952 # local_part_suffix_optional
5954 .vindex "&$local_part_suffix$&"
5955 show how you can specify the recognition of local part suffixes. If the first
5956 is uncommented, a suffix beginning with either a plus or a minus sign, followed
5957 by any sequence of characters, is removed from the local part and placed in the
5958 variable &$local_part_suffix$&. The second suffix option specifies that the
5959 presence of a suffix in the local part is optional. When a suffix is present,
5960 the check for a local login uses the local part with the suffix removed.
5962 When a local user account is found, the file called &_.forward_& in the user's
5963 home directory is consulted. If it does not exist, or is empty, the router
5964 declines. Otherwise, the contents of &_.forward_& are interpreted as
5965 redirection data (see chapter &<<CHAPredirect>>& for more details).
5967 .cindex "Sieve filter" "enabling in default router"
5968 Traditional &_.forward_& files contain just a list of addresses, pipes, or
5969 files. Exim supports this by default. However, if &%allow_filter%& is set (it
5970 is commented out by default), the contents of the file are interpreted as a set
5971 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
5972 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
5973 separate document entitled &'Exim's interfaces to mail filtering'&.
5975 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
5976 verifying addresses, or when running as a consequence of an SMTP EXPN command.
5977 There are two reasons for doing this:
5980 Whether or not a local user has a &_.forward_& file is not really relevant when
5981 checking an address for validity; it makes sense not to waste resources doing
5984 More importantly, when Exim is verifying addresses or handling an EXPN
5985 command during an SMTP session, it is running as the Exim user, not as root.
5986 The group is the Exim group, and no additional groups are set up.
5987 It may therefore not be possible for Exim to read users' &_.forward_& files at
5991 The setting of &%check_ancestor%& prevents the router from generating a new
5992 address that is the same as any previous address that was redirected. (This
5993 works round a problem concerning a bad interaction between aliasing and
5994 forwarding &-- see section &<<SECTredlocmai>>&).
5996 The final three option settings specify the transports that are to be used when
5997 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
5998 auto-reply, respectively. For example, if a &_.forward_& file contains
6000 a.nother@elsewhere.example, /home/spqr/archive
6002 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
6008 # local_part_suffix = +* : -*
6009 # local_part_suffix_optional
6010 transport = local_delivery
6012 The final router sets up delivery into local mailboxes, provided that the local
6013 part is the name of a local login, by accepting the address and assigning it to
6014 the &(local_delivery)& transport. Otherwise, we have reached the end of the
6015 routers, so the address is bounced. The commented suffix settings fulfil the
6016 same purpose as they do for the &(userforward)& router.
6019 .section "Transport configuration" "SECID56"
6020 .cindex "default" "transports"
6021 .cindex "transports" "default"
6022 Transports define mechanisms for actually delivering messages. They operate
6023 only when referenced from routers, so the order in which they are defined does
6024 not matter. The transports section of the configuration starts with
6028 One remote transport and four local transports are defined.
6034 This transport is used for delivering messages over SMTP connections.
6035 The list of remote hosts comes from the router.
6036 The &%hosts_try_prdr%& option enables an efficiency SMTP option.
6037 It is negotiated between client and server
6038 and not expected to cause problems but can be disabled if needed.
6039 All other options are defaulted.
6043 file = /var/mail/$local_part
6050 This &(appendfile)& transport is used for local delivery to user mailboxes in
6051 traditional BSD mailbox format. By default it runs under the uid and gid of the
6052 local user, which requires the sticky bit to be set on the &_/var/mail_&
6053 directory. Some systems use the alternative approach of running mail deliveries
6054 under a particular group instead of using the sticky bit. The commented options
6055 show how this can be done.
6057 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6058 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6059 similarly-named options above.
6065 This transport is used for handling deliveries to pipes that are generated by
6066 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6067 option specifies that any output on stdout or stderr generated by the pipe is to
6068 be returned to the sender.
6076 This transport is used for handling deliveries to files that are generated by
6077 redirection. The name of the file is not specified in this instance of
6078 &(appendfile)&, because it comes from the &(redirect)& router.
6083 This transport is used for handling automatic replies generated by users'
6088 .section "Default retry rule" "SECID57"
6089 .cindex "retry" "default rule"
6090 .cindex "default" "retry rule"
6091 The retry section of the configuration file contains rules which affect the way
6092 Exim retries deliveries that cannot be completed at the first attempt. It is
6093 introduced by the line
6097 In the default configuration, there is just one rule, which applies to all
6100 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6102 This causes any temporarily failing address to be retried every 15 minutes for
6103 2 hours, then at intervals starting at one hour and increasing by a factor of
6104 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6105 is not delivered after 4 days of temporary failure, it is bounced.
6107 If the retry section is removed from the configuration, or is empty (that is,
6108 if no retry rules are defined), Exim will not retry deliveries. This turns
6109 temporary errors into permanent errors.
6112 .section "Rewriting configuration" "SECID58"
6113 The rewriting section of the configuration, introduced by
6117 contains rules for rewriting addresses in messages as they arrive. There are no
6118 rewriting rules in the default configuration file.
6122 .section "Authenticators configuration" "SECTdefconfauth"
6123 .cindex "AUTH" "configuration"
6124 The authenticators section of the configuration, introduced by
6126 begin authenticators
6128 defines mechanisms for the use of the SMTP AUTH command. The default
6129 configuration file contains two commented-out example authenticators
6130 which support plaintext username/password authentication using the
6131 standard PLAIN mechanism and the traditional but non-standard LOGIN
6132 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6133 to support most MUA software.
6135 The example PLAIN authenticator looks like this:
6138 # driver = plaintext
6139 # server_set_id = $auth2
6140 # server_prompts = :
6141 # server_condition = Authentication is not yet configured
6142 # server_advertise_condition = ${if def:tls_in_cipher }
6144 And the example LOGIN authenticator looks like this:
6147 # driver = plaintext
6148 # server_set_id = $auth1
6149 # server_prompts = <| Username: | Password:
6150 # server_condition = Authentication is not yet configured
6151 # server_advertise_condition = ${if def:tls_in_cipher }
6154 The &%server_set_id%& option makes Exim remember the authenticated username
6155 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6156 &%server_prompts%& option configures the &(plaintext)& authenticator so
6157 that it implements the details of the specific authentication mechanism,
6158 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6159 when Exim offers authentication to clients; in the examples, this is only
6160 when TLS or SSL has been started, so to enable the authenticators you also
6161 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6163 The &%server_condition%& setting defines how to verify that the username and
6164 password are correct. In the examples it just produces an error message.
6165 To make the authenticators work, you can use a string expansion
6166 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6168 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6169 usercode and password are in different positions.
6170 Chapter &<<CHAPplaintext>>& covers both.
6172 .ecindex IIDconfiwal
6176 . ////////////////////////////////////////////////////////////////////////////
6177 . ////////////////////////////////////////////////////////////////////////////
6179 .chapter "Regular expressions" "CHAPregexp"
6181 .cindex "regular expressions" "library"
6183 Exim supports the use of regular expressions in many of its options. It
6184 uses the PCRE regular expression library; this provides regular expression
6185 matching that is compatible with Perl 5. The syntax and semantics of
6186 regular expressions is discussed in many Perl reference books, and also in
6187 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6188 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6190 The documentation for the syntax and semantics of the regular expressions that
6191 are supported by PCRE is included in the PCRE distribution, and no further
6192 description is included here. The PCRE functions are called from Exim using
6193 the default option settings (that is, with no PCRE options set), except that
6194 the PCRE_CASELESS option is set when the matching is required to be
6197 In most cases, when a regular expression is required in an Exim configuration,
6198 it has to start with a circumflex, in order to distinguish it from plain text
6199 or an &"ends with"& wildcard. In this example of a configuration setting, the
6200 second item in the colon-separated list is a regular expression.
6202 domains = a.b.c : ^\\d{3} : *.y.z : ...
6204 The doubling of the backslash is required because of string expansion that
6205 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6206 of this issue, and a way of avoiding the need for doubling backslashes. The
6207 regular expression that is eventually used in this example contains just one
6208 backslash. The circumflex is included in the regular expression, and has the
6209 normal effect of &"anchoring"& it to the start of the string that is being
6212 There are, however, two cases where a circumflex is not required for the
6213 recognition of a regular expression: these are the &%match%& condition in a
6214 string expansion, and the &%matches%& condition in an Exim filter file. In
6215 these cases, the relevant string is always treated as a regular expression; if
6216 it does not start with a circumflex, the expression is not anchored, and can
6217 match anywhere in the subject string.
6219 In all cases, if you want a regular expression to match at the end of a string,
6220 you must code the $ metacharacter to indicate this. For example:
6222 domains = ^\\d{3}\\.example
6224 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6227 domains = ^\\d{3}\\.example\$
6229 if you want &'example'& to be the top-level domain. The backslash before the
6230 $ is needed because string expansion also interprets dollar characters.
6234 . ////////////////////////////////////////////////////////////////////////////
6235 . ////////////////////////////////////////////////////////////////////////////
6237 .chapter "File and database lookups" "CHAPfdlookup"
6238 .scindex IIDfidalo1 "file" "lookups"
6239 .scindex IIDfidalo2 "database" "lookups"
6240 .cindex "lookup" "description of"
6241 Exim can be configured to look up data in files or databases as it processes
6242 messages. Two different kinds of syntax are used:
6245 A string that is to be expanded may contain explicit lookup requests. These
6246 cause parts of the string to be replaced by data that is obtained from the
6247 lookup. Lookups of this type are conditional expansion items. Different results
6248 can be defined for the cases of lookup success and failure. See chapter
6249 &<<CHAPexpand>>&, where string expansions are described in detail.
6250 The key for the lookup is specified as part of the string expansion.
6252 Lists of domains, hosts, and email addresses can contain lookup requests as a
6253 way of avoiding excessively long linear lists. In this case, the data that is
6254 returned by the lookup is often (but not always) discarded; whether the lookup
6255 succeeds or fails is what really counts. These kinds of list are described in
6256 chapter &<<CHAPdomhosaddlists>>&.
6257 The key for the lookup is given by the context in which the list is expanded.
6260 String expansions, lists, and lookups interact with each other in such a way
6261 that there is no order in which to describe any one of them that does not
6262 involve references to the others. Each of these three chapters makes more sense
6263 if you have read the other two first. If you are reading this for the first
6264 time, be aware that some of it will make a lot more sense after you have read
6265 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6267 .section "Examples of different lookup syntax" "SECID60"
6268 It is easy to confuse the two different kinds of lookup, especially as the
6269 lists that may contain the second kind are always expanded before being
6270 processed as lists. Therefore, they may also contain lookups of the first kind.
6271 Be careful to distinguish between the following two examples:
6273 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6274 domains = lsearch;/some/file
6276 The first uses a string expansion, the result of which must be a domain list.
6277 No strings have been specified for a successful or a failing lookup; the
6278 defaults in this case are the looked-up data and an empty string, respectively.
6279 The expansion takes place before the string is processed as a list, and the
6280 file that is searched could contain lines like this:
6282 192.168.3.4: domain1:domain2:...
6283 192.168.1.9: domain3:domain4:...
6285 When the lookup succeeds, the result of the expansion is a list of domains (and
6286 possibly other types of item that are allowed in domain lists).
6288 In the second example, the lookup is a single item in a domain list. It causes
6289 Exim to use a lookup to see if the domain that is being processed can be found
6290 in the file. The file could contains lines like this:
6295 Any data that follows the keys is not relevant when checking that the domain
6296 matches the list item.
6298 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6299 Consider a file containing lines like this:
6301 192.168.5.6: lsearch;/another/file
6303 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6304 first &%domains%& setting above generates the second setting, which therefore
6305 causes a second lookup to occur.
6307 The rest of this chapter describes the different lookup types that are
6308 available. Any of them can be used in any part of the configuration where a
6309 lookup is permitted.
6312 .section "Lookup types" "SECID61"
6313 .cindex "lookup" "types of"
6314 .cindex "single-key lookup" "definition of"
6315 Two different types of data lookup are implemented:
6318 The &'single-key'& type requires the specification of a file in which to look,
6319 and a single key to search for. The key must be a non-empty string for the
6320 lookup to succeed. The lookup type determines how the file is searched.
6322 .cindex "query-style lookup" "definition of"
6323 The &'query-style'& type accepts a generalized database query. No particular
6324 key value is assumed by Exim for query-style lookups. You can use whichever
6325 Exim variables you need to construct the database query.
6328 The code for each lookup type is in a separate source file that is included in
6329 the binary of Exim only if the corresponding compile-time option is set. The
6330 default settings in &_src/EDITME_& are:
6335 which means that only linear searching and DBM lookups are included by default.
6336 For some types of lookup (e.g. SQL databases), you need to install appropriate
6337 libraries and header files before building Exim.
6342 .section "Single-key lookup types" "SECTsinglekeylookups"
6343 .cindex "lookup" "single-key types"
6344 .cindex "single-key lookup" "list of types"
6345 The following single-key lookup types are implemented:
6348 .cindex "cdb" "description of"
6349 .cindex "lookup" "cdb"
6350 .cindex "binary zero" "in lookup key"
6351 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6352 string without a terminating binary zero. The cdb format is designed for
6353 indexed files that are read frequently and never updated, except by total
6354 re-creation. As such, it is particularly suitable for large files containing
6355 aliases or other indexed data referenced by an MTA. Information about cdb can
6356 be found in several places:
6358 &url(http://www.pobox.com/~djb/cdb.html)
6359 &url(ftp://ftp.corpit.ru/pub/tinycdb/)
6360 &url(http://packages.debian.org/stable/utils/freecdb.html)
6362 A cdb distribution is not needed in order to build Exim with cdb support,
6363 because the code for reading cdb files is included directly in Exim itself.
6364 However, no means of building or testing cdb files is provided with Exim, so
6365 you need to obtain a cdb distribution in order to do this.
6367 .cindex "DBM" "lookup type"
6368 .cindex "lookup" "dbm"
6369 .cindex "binary zero" "in lookup key"
6370 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6371 DBM file by looking up the record with the given key. A terminating binary
6372 zero is included in the key that is passed to the DBM library. See section
6373 &<<SECTdb>>& for a discussion of DBM libraries.
6375 .cindex "Berkeley DB library" "file format"
6376 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6377 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6378 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6379 the DB_UNKNOWN option. This enables it to handle any of the types of database
6380 that the library supports, and can be useful for accessing DBM files created by
6381 other applications. (For earlier DB versions, DB_HASH is always used.)
6383 .cindex "lookup" "dbmjz"
6384 .cindex "lookup" "dbm &-- embedded NULs"
6386 .cindex "dbmjz lookup type"
6387 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6388 interpreted as an Exim list; the elements of the list are joined together with
6389 ASCII NUL characters to form the lookup key. An example usage would be to
6390 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6391 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6392 &(cram_md5)& authenticator.
6394 .cindex "lookup" "dbmnz"
6395 .cindex "lookup" "dbm &-- terminating zero"
6396 .cindex "binary zero" "in lookup key"
6398 .cindex "&_/etc/userdbshadow.dat_&"
6399 .cindex "dbmnz lookup type"
6400 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6401 is not included in the key that is passed to the DBM library. You may need this
6402 if you want to look up data in files that are created by or shared with some
6403 other application that does not use terminating zeros. For example, you need to
6404 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6405 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6406 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6407 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6409 .cindex "lookup" "dsearch"
6410 .cindex "dsearch lookup type"
6411 &(dsearch)&: The given file must be a directory; this is searched for an entry
6412 whose name is the key by calling the &[lstat()]& function. The key may not
6413 contain any forward slash characters. If &[lstat()]& succeeds, the result of
6414 the lookup is the name of the entry, which may be a file, directory,
6415 symbolic link, or any other kind of directory entry. An example of how this
6416 lookup can be used to support virtual domains is given in section
6417 &<<SECTvirtualdomains>>&.
6419 .cindex "lookup" "iplsearch"
6420 .cindex "iplsearch lookup type"
6421 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6422 terminated by a colon or white space or the end of the line. The keys in the
6423 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6424 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6425 being interpreted as a key terminator. For example:
6427 1.2.3.4: data for 1.2.3.4
6428 192.168.0.0/16: data for 192.168.0.0/16
6429 "abcd::cdab": data for abcd::cdab
6430 "abcd:abcd::/32" data for abcd:abcd::/32
6432 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6433 file is searched linearly, using the CIDR masks where present, until a matching
6434 key is found. The first key that matches is used; there is no attempt to find a
6435 &"best"& match. Apart from the way the keys are matched, the processing for
6436 &(iplsearch)& is the same as for &(lsearch)&.
6438 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6439 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6440 lookup types support only literal keys.
6442 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6443 the implicit key is the host's IP address rather than its name (see section
6444 &<<SECThoslispatsikey>>&).
6446 .cindex "linear search"
6447 .cindex "lookup" "lsearch"
6448 .cindex "lsearch lookup type"
6449 .cindex "case sensitivity" "in lsearch lookup"
6450 &(lsearch)&: The given file is a text file that is searched linearly for a
6451 line beginning with the search key, terminated by a colon or white space or the
6452 end of the line. The search is case-insensitive; that is, upper and lower case
6453 letters are treated as the same. The first occurrence of the key that is found
6454 in the file is used.
6456 White space between the key and the colon is permitted. The remainder of the
6457 line, with leading and trailing white space removed, is the data. This can be
6458 continued onto subsequent lines by starting them with any amount of white
6459 space, but only a single space character is included in the data at such a
6460 junction. If the data begins with a colon, the key must be terminated by a
6465 Empty lines and lines beginning with # are ignored, even if they occur in the
6466 middle of an item. This is the traditional textual format of alias files. Note
6467 that the keys in an &(lsearch)& file are literal strings. There is no
6468 wildcarding of any kind.
6470 .cindex "lookup" "lsearch &-- colons in keys"
6471 .cindex "white space" "in lsearch key"
6472 In most &(lsearch)& files, keys are not required to contain colons or #
6473 characters, or white space. However, if you need this feature, it is available.
6474 If a key begins with a doublequote character, it is terminated only by a
6475 matching quote (or end of line), and the normal escaping rules apply to its
6476 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6477 quoted keys (exactly as for unquoted keys). There is no special handling of
6478 quotes for the data part of an &(lsearch)& line.
6481 .cindex "NIS lookup type"
6482 .cindex "lookup" "NIS"
6483 .cindex "binary zero" "in lookup key"
6484 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
6485 the given key, without a terminating binary zero. There is a variant called
6486 &(nis0)& which does include the terminating binary zero in the key. This is
6487 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6488 aliases; the full map names must be used.
6491 .cindex "wildlsearch lookup type"
6492 .cindex "lookup" "wildlsearch"
6493 .cindex "nwildlsearch lookup type"
6494 .cindex "lookup" "nwildlsearch"
6495 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6496 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6497 the file may be wildcarded. The difference between these two lookup types is
6498 that for &(wildlsearch)&, each key in the file is string-expanded before being
6499 used, whereas for &(nwildlsearch)&, no expansion takes place.
6501 .cindex "case sensitivity" "in (n)wildlsearch lookup"
6502 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
6503 file that are regular expressions can be made case-sensitive by the use of
6504 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
6506 . ==== As this is a nested list, any displays it contains must be indented
6507 . ==== as otherwise they are too far to the left.
6510 The string may begin with an asterisk to mean &"ends with"&. For example:
6512 *.a.b.c data for anything.a.b.c
6513 *fish data for anythingfish
6516 The string may begin with a circumflex to indicate a regular expression. For
6517 example, for &(wildlsearch)&:
6519 ^\N\d+\.a\.b\N data for <digits>.a.b
6521 Note the use of &`\N`& to disable expansion of the contents of the regular
6522 expression. If you are using &(nwildlsearch)&, where the keys are not
6523 string-expanded, the equivalent entry is:
6525 ^\d+\.a\.b data for <digits>.a.b
6527 The case-insensitive flag is set at the start of compiling the regular
6528 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
6529 For example, to make the entire pattern case-sensitive:
6531 ^(?-i)\d+\.a\.b data for <digits>.a.b
6534 If the regular expression contains white space or colon characters, you must
6535 either quote it (see &(lsearch)& above), or represent these characters in other
6536 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
6537 colon. This may be easier than quoting, because if you quote, you have to
6538 escape all the backslashes inside the quotes.
6540 &*Note*&: It is not possible to capture substrings in a regular expression
6541 match for later use, because the results of all lookups are cached. If a lookup
6542 is repeated, the result is taken from the cache, and no actual pattern matching
6543 takes place. The values of all the numeric variables are unset after a
6544 &((n)wildlsearch)& match.
6547 Although I cannot see it being of much use, the general matching function that
6548 is used to implement &((n)wildlsearch)& means that the string may begin with a
6549 lookup name terminated by a semicolon, and followed by lookup data. For
6552 cdb;/some/file data for keys that match the file
6554 The data that is obtained from the nested lookup is discarded.
6557 Keys that do not match any of these patterns are interpreted literally. The
6558 continuation rules for the data are the same as for &(lsearch)&, and keys may
6559 be followed by optional colons.
6561 &*Warning*&: Unlike most other single-key lookup types, a file of data for
6562 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
6563 lookup types support only literal keys.
6567 .section "Query-style lookup types" "SECID62"
6568 .cindex "lookup" "query-style types"
6569 .cindex "query-style lookup" "list of types"
6570 The supported query-style lookup types are listed below. Further details about
6571 many of them are given in later sections.
6574 .cindex "DNS" "as a lookup type"
6575 .cindex "lookup" "DNS"
6576 &(dnsdb)&: This does a DNS search for one or more records whose domain names
6577 are given in the supplied query. The resulting data is the contents of the
6578 records. See section &<<SECTdnsdb>>&.
6580 .cindex "InterBase lookup type"
6581 .cindex "lookup" "InterBase"
6582 &(ibase)&: This does a lookup in an InterBase database.
6584 .cindex "LDAP" "lookup type"
6585 .cindex "lookup" "LDAP"
6586 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
6587 returns attributes from a single entry. There is a variant called &(ldapm)&
6588 that permits values from multiple entries to be returned. A third variant
6589 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
6590 any attribute values. See section &<<SECTldap>>&.
6592 .cindex "MySQL" "lookup type"
6593 .cindex "lookup" "MySQL"
6594 &(mysql)&: The format of the query is an SQL statement that is passed to a
6595 MySQL database. See section &<<SECTsql>>&.
6597 .cindex "NIS+ lookup type"
6598 .cindex "lookup" "NIS+"
6599 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
6600 the field to be returned. See section &<<SECTnisplus>>&.
6602 .cindex "Oracle" "lookup type"
6603 .cindex "lookup" "Oracle"
6604 &(oracle)&: The format of the query is an SQL statement that is passed to an
6605 Oracle database. See section &<<SECTsql>>&.
6607 .cindex "lookup" "passwd"
6608 .cindex "passwd lookup type"
6609 .cindex "&_/etc/passwd_&"
6610 &(passwd)& is a query-style lookup with queries that are just user names. The
6611 lookup calls &[getpwnam()]& to interrogate the system password data, and on
6612 success, the result string is the same as you would get from an &(lsearch)&
6613 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
6614 password value. For example:
6616 *:42:42:King Rat:/home/kr:/bin/bash
6619 .cindex "PostgreSQL lookup type"
6620 .cindex "lookup" "PostgreSQL"
6621 &(pgsql)&: The format of the query is an SQL statement that is passed to a
6622 PostgreSQL database. See section &<<SECTsql>>&.
6625 .cindex "sqlite lookup type"
6626 .cindex "lookup" "sqlite"
6627 &(sqlite)&: The format of the query is a file name followed by an SQL statement
6628 that is passed to an SQLite database. See section &<<SECTsqlite>>&.
6631 &(testdb)&: This is a lookup type that is used for testing Exim. It is
6632 not likely to be useful in normal operation.
6634 .cindex "whoson lookup type"
6635 .cindex "lookup" "whoson"
6636 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
6637 allows a server to check whether a particular (dynamically allocated) IP
6638 address is currently allocated to a known (trusted) user and, optionally, to
6639 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
6640 at one time for &"POP before SMTP"& authentication, but that approach has been
6641 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
6642 &"POP before SMTP"& checking using ACL statements such as
6644 require condition = \
6645 ${lookup whoson {$sender_host_address}{yes}{no}}
6647 The query consists of a single IP address. The value returned is the name of
6648 the authenticated user, which is stored in the variable &$value$&. However, in
6649 this example, the data in &$value$& is not used; the result of the lookup is
6650 one of the fixed strings &"yes"& or &"no"&.
6655 .section "Temporary errors in lookups" "SECID63"
6656 .cindex "lookup" "temporary error in"
6657 Lookup functions can return temporary error codes if the lookup cannot be
6658 completed. For example, an SQL or LDAP database might be unavailable. For this
6659 reason, it is not advisable to use a lookup that might do this for critical
6660 options such as a list of local domains.
6662 When a lookup cannot be completed in a router or transport, delivery
6663 of the message (to the relevant address) is deferred, as for any other
6664 temporary error. In other circumstances Exim may assume the lookup has failed,
6665 or may give up altogether.
6669 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
6670 .cindex "wildcard lookups"
6671 .cindex "lookup" "default values"
6672 .cindex "lookup" "wildcard"
6673 .cindex "lookup" "* added to type"
6674 .cindex "default" "in single-key lookups"
6675 In this context, a &"default value"& is a value specified by the administrator
6676 that is to be used if a lookup fails.
6678 &*Note:*& This section applies only to single-key lookups. For query-style
6679 lookups, the facilities of the query language must be used. An attempt to
6680 specify a default for a query-style lookup provokes an error.
6682 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
6683 and the initial lookup fails, the key &"*"& is looked up in the file to
6684 provide a default value. See also the section on partial matching below.
6686 .cindex "*@ with single-key lookup"
6687 .cindex "lookup" "*@ added to type"
6688 .cindex "alias file" "per-domain default"
6689 Alternatively, if &"*@"& is added to a single-key lookup type (for example
6690 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
6691 character, a second lookup is done with everything before the last @ replaced
6692 by *. This makes it possible to provide per-domain defaults in alias files
6693 that include the domains in the keys. If the second lookup fails (or doesn't
6694 take place because there is no @ in the key), &"*"& is looked up.
6695 For example, a &(redirect)& router might contain:
6697 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
6699 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
6700 looks up these keys, in this order:
6706 The data is taken from whichever key it finds first. &*Note*&: In an
6707 &(lsearch)& file, this does not mean the first of these keys in the file. A
6708 complete scan is done for each key, and only if it is not found at all does
6709 Exim move on to try the next key.
6713 .section "Partial matching in single-key lookups" "SECTpartiallookup"
6714 .cindex "partial matching"
6715 .cindex "wildcard lookups"
6716 .cindex "lookup" "partial matching"
6717 .cindex "lookup" "wildcard"
6718 .cindex "asterisk" "in search type"
6719 The normal operation of a single-key lookup is to search the file for an exact
6720 match with the given key. However, in a number of situations where domains are
6721 being looked up, it is useful to be able to do partial matching. In this case,
6722 information in the file that has a key starting with &"*."& is matched by any
6723 domain that ends with the components that follow the full stop. For example, if
6724 a key in a DBM file is
6726 *.dates.fict.example
6728 then when partial matching is enabled this is matched by (amongst others)
6729 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
6730 by &'dates.fict.example'&, if that does not appear as a separate key in the
6733 &*Note*&: Partial matching is not available for query-style lookups. It is
6734 also not available for any lookup items in address lists (see section
6735 &<<SECTaddresslist>>&).
6737 Partial matching is implemented by doing a series of separate lookups using
6738 keys constructed by modifying the original subject key. This means that it can
6739 be used with any of the single-key lookup types, provided that
6740 partial matching keys
6741 beginning with a special prefix (default &"*."&) are included in the data file.
6742 Keys in the file that do not begin with the prefix are matched only by
6743 unmodified subject keys when partial matching is in use.
6745 Partial matching is requested by adding the string &"partial-"& to the front of
6746 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
6747 is done, the subject key is first looked up unmodified; if that fails, &"*."&
6748 is added at the start of the subject key, and it is looked up again. If that
6749 fails, further lookups are tried with dot-separated components removed from the
6750 start of the subject key, one-by-one, and &"*."& added on the front of what
6753 A minimum number of two non-* components are required. This can be adjusted
6754 by including a number before the hyphen in the search type. For example,
6755 &%partial3-lsearch%& specifies a minimum of three non-* components in the
6756 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
6757 subject key is &'2250.dates.fict.example'& then the following keys are looked
6758 up when the minimum number of non-* components is two:
6760 2250.dates.fict.example
6761 *.2250.dates.fict.example
6762 *.dates.fict.example
6765 As soon as one key in the sequence is successfully looked up, the lookup
6768 .cindex "lookup" "partial matching &-- changing prefix"
6769 .cindex "prefix" "for partial matching"
6770 The use of &"*."& as the partial matching prefix is a default that can be
6771 changed. The motivation for this feature is to allow Exim to operate with file
6772 formats that are used by other MTAs. A different prefix can be supplied in
6773 parentheses instead of the hyphen after &"partial"&. For example:
6775 domains = partial(.)lsearch;/some/file
6777 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
6778 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
6779 components is unchanged). The prefix may consist of any punctuation characters
6780 other than a closing parenthesis. It may be empty, for example:
6782 domains = partial1()cdb;/some/file
6784 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
6785 &`a.b.c`&, &`b.c`&, and &`c`&.
6787 If &"partial0"& is specified, what happens at the end (when the lookup with
6788 just one non-wild component has failed, and the original key is shortened right
6789 down to the null string) depends on the prefix:
6792 If the prefix has zero length, the whole lookup fails.
6794 If the prefix has length 1, a lookup for just the prefix is done. For
6795 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
6797 Otherwise, if the prefix ends in a dot, the dot is removed, and the
6798 remainder is looked up. With the default prefix, therefore, the final lookup is
6799 for &"*"& on its own.
6801 Otherwise, the whole prefix is looked up.
6805 If the search type ends in &"*"& or &"*@"& (see section
6806 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
6807 this implies happens after all partial lookups have failed. If &"partial0"& is
6808 specified, adding &"*"& to the search type has no effect with the default
6809 prefix, because the &"*"& key is already included in the sequence of partial
6810 lookups. However, there might be a use for lookup types such as
6811 &"partial0(.)lsearch*"&.
6813 The use of &"*"& in lookup partial matching differs from its use as a wildcard
6814 in domain lists and the like. Partial matching works only in terms of
6815 dot-separated components; a key such as &`*fict.example`&
6816 in a database file is useless, because the asterisk in a partial matching
6817 subject key is always followed by a dot.
6822 .section "Lookup caching" "SECID64"
6823 .cindex "lookup" "caching"
6824 .cindex "caching" "lookup data"
6825 Exim caches all lookup results in order to avoid needless repetition of
6826 lookups. However, because (apart from the daemon) Exim operates as a collection
6827 of independent, short-lived processes, this caching applies only within a
6828 single Exim process. There is no inter-process lookup caching facility.
6830 For single-key lookups, Exim keeps the relevant files open in case there is
6831 another lookup that needs them. In some types of configuration this can lead to
6832 many files being kept open for messages with many recipients. To avoid hitting
6833 the operating system limit on the number of simultaneously open files, Exim
6834 closes the least recently used file when it needs to open more files than its
6835 own internal limit, which can be changed via the &%lookup_open_max%& option.
6837 The single-key lookup files are closed and the lookup caches are flushed at
6838 strategic points during delivery &-- for example, after all routing is
6844 .section "Quoting lookup data" "SECID65"
6845 .cindex "lookup" "quoting"
6846 .cindex "quoting" "in lookups"
6847 When data from an incoming message is included in a query-style lookup, there
6848 is the possibility of special characters in the data messing up the syntax of
6849 the query. For example, a NIS+ query that contains
6853 will be broken if the local part happens to contain a closing square bracket.
6854 For NIS+, data can be enclosed in double quotes like this:
6856 [name="$local_part"]
6858 but this still leaves the problem of a double quote in the data. The rule for
6859 NIS+ is that double quotes must be doubled. Other lookup types have different
6860 rules, and to cope with the differing requirements, an expansion operator
6861 of the following form is provided:
6863 ${quote_<lookup-type>:<string>}
6865 For example, the safest way to write the NIS+ query is
6867 [name="${quote_nisplus:$local_part}"]
6869 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
6870 operator can be used for all lookup types, but has no effect for single-key
6871 lookups, since no quoting is ever needed in their key strings.
6876 .section "More about dnsdb" "SECTdnsdb"
6877 .cindex "dnsdb lookup"
6878 .cindex "lookup" "dnsdb"
6879 .cindex "DNS" "as a lookup type"
6880 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
6881 of a record type and a domain name, separated by an equals sign. For example,
6882 an expansion string could contain:
6884 ${lookup dnsdb{mx=a.b.example}{$value}fail}
6886 If the lookup succeeds, the result is placed in &$value$&, which in this case
6887 is used on its own as the result. If the lookup does not succeed, the
6888 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
6889 &<<SECTforexpfai>>& for an explanation of what this means.
6891 The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
6892 and TXT, and, when Exim is compiled with IPv6 support, AAAA.
6893 If no type is given, TXT is assumed.
6895 For any record type, if multiple records are found, the data is returned as a
6896 concatenation, with newline as the default separator. The order, of course,
6897 depends on the DNS resolver. You can specify a different separator character
6898 between multiple records by putting a right angle-bracket followed immediately
6899 by the new separator at the start of the query. For example:
6901 ${lookup dnsdb{>: a=host1.example}}
6903 It is permitted to specify a space as the separator character. Further
6904 white space is ignored.
6905 For lookup types that return multiple fields per record,
6906 an alternate field separator can be specified using a comma after the main
6907 separator character, followed immediately by the field separator.
6909 .cindex "PTR record" "in &(dnsdb)& lookup"
6910 When the type is PTR,
6911 the data can be an IP address, written as normal; inversion and the addition of
6912 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
6914 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
6916 If the data for a PTR record is not a syntactically valid IP address, it is not
6917 altered and nothing is added.
6919 .cindex "MX record" "in &(dnsdb)& lookup"
6920 .cindex "SRV record" "in &(dnsdb)& lookup"
6921 For an MX lookup, both the preference value and the host name are returned for
6922 each record, separated by a space. For an SRV lookup, the priority, weight,
6923 port, and host name are returned for each record, separated by spaces.
6924 The field separator can be modified as above.
6926 .cindex "TXT record" "in &(dnsdb)& lookup"
6927 .cindex "SPF record" "in &(dnsdb)& lookup"
6928 For TXT records with multiple items of data, only the first item is returned,
6929 unless a field separator is specified.
6930 To concatenate items without a separator, use a semicolon instead.
6932 default behaviour is to concatenate multiple items without using a separator.
6934 ${lookup dnsdb{>\n,: txt=a.b.example}}
6935 ${lookup dnsdb{>\n; txt=a.b.example}}
6936 ${lookup dnsdb{spf=example.org}}
6938 It is permitted to specify a space as the separator character. Further
6939 white space is ignored.
6941 .cindex "SOA record" "in &(dnsdb)& lookup"
6942 For an SOA lookup, while no result is obtained the lookup is redone with
6943 successively more leading components dropped from the given domain.
6944 Only the primary-nameserver field is returned unless a field separator is
6947 ${lookup dnsdb{>:,; soa=a.b.example.com}}
6950 .section "Dnsdb lookup modifiers" "SECTdnsdb_mod"
6951 .cindex "dnsdb modifiers"
6952 .cindex "modifiers" "dnsdb"
6953 .cindex "options" "dnsdb"
6954 Modifiers for &(dnsdb)& lookups are given by optional keywords,
6955 each followed by a comma,
6956 that may appear before the record type.
6958 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
6959 temporary DNS error for any of them, the behaviour is controlled by
6960 a defer-option modifier.
6961 The possible keywords are
6962 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
6963 With &"strict"& behaviour, any temporary DNS error causes the
6964 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
6965 ignored, and the behaviour is as if the DNS lookup failed to find anything.
6966 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
6967 error causes the whole lookup to defer only if none of the other lookups
6968 succeed. The default is &"lax"&, so the following lookups are equivalent:
6970 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
6971 ${lookup dnsdb{a=one.host.com:two.host.com}}
6973 Thus, in the default case, as long as at least one of the DNS lookups
6974 yields some data, the lookup succeeds.
6976 .cindex "DNSSEC" "dns lookup"
6977 Use of &(DNSSEC)& is controlled by a dnssec modifier.
6978 The possible keywords are
6979 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
6980 With &"strict"& or &"lax"& DNSSEC information is requested
6982 With &"strict"& a response from the DNS resolver that
6983 is not labelled as authenticated data
6984 is treated as equivalent to a temporary DNS error.
6985 The default is &"never"&.
6987 See also the &$lookup_dnssec_authenticated$& variable.
6989 .cindex timeout "dns lookup"
6990 .cindex "DNS" timeout
6991 Timeout for the dnsdb lookup can be controlled by a retrans modifier.
6992 The form is &"retrans_VAL"& where VAL is an Exim time specification
6994 The default value is set by the main configuration option &%dns_retrans%&.
6996 Retries for the dnsdb lookup can be controlled by a retry modifier.
6997 The form if &"retry_VAL"& where VAL is an integer.
6998 The default count is set by the main configuration option &%dns_retry%&.
7001 .cindex cacheing "of dns lookup"
7002 .cindex TTL "of dns lookup"
7004 Dnsdb lookup results are cached within a single process (and its children).
7005 The cache entry lifetime is limited to the smallest time-to-live (TTL)
7006 value of the set of returned DNS records.
7010 .section "Pseudo dnsdb record types" "SECID66"
7011 .cindex "MX record" "in &(dnsdb)& lookup"
7012 By default, both the preference value and the host name are returned for
7013 each MX record, separated by a space. If you want only host names, you can use
7014 the pseudo-type MXH:
7016 ${lookup dnsdb{mxh=a.b.example}}
7018 In this case, the preference values are omitted, and just the host names are
7021 .cindex "name server for enclosing domain"
7022 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
7023 records on the given domain, but if none are found, it removes the first
7024 component of the domain name, and tries again. This process continues until NS
7025 records are found or there are no more components left (or there is a DNS
7026 error). In other words, it may return the name servers for a top-level domain,
7027 but it never returns the root name servers. If there are no NS records for the
7028 top-level domain, the lookup fails. Consider these examples:
7030 ${lookup dnsdb{zns=xxx.quercite.com}}
7031 ${lookup dnsdb{zns=xxx.edu}}
7033 Assuming that in each case there are no NS records for the full domain name,
7034 the first returns the name servers for &%quercite.com%&, and the second returns
7035 the name servers for &%edu%&.
7037 You should be careful about how you use this lookup because, unless the
7038 top-level domain does not exist, the lookup always returns some host names. The
7039 sort of use to which this might be put is for seeing if the name servers for a
7040 given domain are on a blacklist. You can probably assume that the name servers
7041 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
7044 .cindex "CSA" "in &(dnsdb)& lookup"
7045 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
7046 records according to the CSA rules, which are described in section
7047 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
7048 not sufficient because of the extra parent domain search behaviour of CSA. The
7049 result of a successful lookup such as:
7051 ${lookup dnsdb {csa=$sender_helo_name}}
7053 has two space-separated fields: an authorization code and a target host name.
7054 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
7055 authorization required but absent, or &"?"& for unknown.
7057 .cindex "A+" "in &(dnsdb)& lookup"
7058 The pseudo-type A+ performs an AAAA
7059 and then an A lookup. All results are returned; defer processing
7060 (see below) is handled separately for each lookup. Example:
7062 ${lookup dnsdb {>; a+=$sender_helo_name}}
7066 .section "Multiple dnsdb lookups" "SECID67"
7067 In the previous sections, &(dnsdb)& lookups for a single domain are described.
7068 However, you can specify a list of domains or IP addresses in a single
7069 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
7070 the default separator, but with the ability to change this. For example:
7072 ${lookup dnsdb{one.domain.com:two.domain.com}}
7073 ${lookup dnsdb{a=one.host.com:two.host.com}}
7074 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
7076 In order to retain backwards compatibility, there is one special case: if
7077 the lookup type is PTR and no change of separator is specified, Exim looks
7078 to see if the rest of the string is precisely one IPv6 address. In this
7079 case, it does not treat it as a list.
7081 The data from each lookup is concatenated, with newline separators by default,
7082 in the same way that multiple DNS records for a single item are handled. A
7083 different separator can be specified, as described above.
7088 .section "More about LDAP" "SECTldap"
7089 .cindex "LDAP" "lookup, more about"
7090 .cindex "lookup" "LDAP"
7091 .cindex "Solaris" "LDAP"
7092 The original LDAP implementation came from the University of Michigan; this has
7093 become &"Open LDAP"&, and there are now two different releases. Another
7094 implementation comes from Netscape, and Solaris 7 and subsequent releases
7095 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7096 the lookup function level, their error handling is different. For this reason
7097 it is necessary to set a compile-time variable when building Exim with LDAP, to
7098 indicate which LDAP library is in use. One of the following should appear in
7099 your &_Local/Makefile_&:
7101 LDAP_LIB_TYPE=UMICHIGAN
7102 LDAP_LIB_TYPE=OPENLDAP1
7103 LDAP_LIB_TYPE=OPENLDAP2
7104 LDAP_LIB_TYPE=NETSCAPE
7105 LDAP_LIB_TYPE=SOLARIS
7107 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7108 same interface as the University of Michigan version.
7110 There are three LDAP lookup types in Exim. These behave slightly differently in
7111 the way they handle the results of a query:
7114 &(ldap)& requires the result to contain just one entry; if there are more, it
7117 &(ldapdn)& also requires the result to contain just one entry, but it is the
7118 Distinguished Name that is returned rather than any attribute values.
7120 &(ldapm)& permits the result to contain more than one entry; the attributes
7121 from all of them are returned.
7125 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7126 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7127 the data returned by a successful lookup is described in the next section.
7128 First we explain how LDAP queries are coded.
7131 .section "Format of LDAP queries" "SECTforldaque"
7132 .cindex "LDAP" "query format"
7133 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7134 the configuration of a &(redirect)& router one might have this setting:
7136 data = ${lookup ldap \
7137 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7138 c=UK?mailbox?base?}}
7140 .cindex "LDAP" "with TLS"
7141 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7142 secure (encrypted) LDAP connections. The second of these ensures that an
7143 encrypted TLS connection is used.
7145 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7146 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7147 See the &%ldap_start_tls%& option.
7149 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7150 controlled. Every part of the TLS configuration can be configured by settings in
7151 &_exim.conf_&. Depending on the version of the client libraries installed on
7152 your system, some of the initialization may have required setting options in
7153 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7154 certificates. This revealed a nuance where the current UID that exim was
7155 running as could affect which config files it read. With Exim 4.83, these
7156 methods become optional, only taking effect if not specifically set in
7160 .section "LDAP quoting" "SECID68"
7161 .cindex "LDAP" "quoting"
7162 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7163 and the second because the LDAP query is represented as a URL. Furthermore,
7164 within an LDAP query, two different kinds of quoting are required. For this
7165 reason, there are two different LDAP-specific quoting operators.
7167 The &%quote_ldap%& operator is designed for use on strings that are part of
7168 filter specifications. Conceptually, it first does the following conversions on
7176 in accordance with RFC 2254. The resulting string is then quoted according
7177 to the rules for URLs, that is, all non-alphanumeric characters except
7181 are converted to their hex values, preceded by a percent sign. For example:
7183 ${quote_ldap: a(bc)*, a<yz>; }
7187 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7189 Removing the URL quoting, this is (with a leading and a trailing space):
7191 a\28bc\29\2A, a<yz>;
7193 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7194 base DN specifications in queries. Conceptually, it first converts the string
7195 by inserting a backslash in front of any of the following characters:
7199 It also inserts a backslash before any leading spaces or # characters, and
7200 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7201 is then quoted according to the rules for URLs. For example:
7203 ${quote_ldap_dn: a(bc)*, a<yz>; }
7207 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7209 Removing the URL quoting, this is (with a trailing space):
7211 \ a(bc)*\, a\<yz\>\;\
7213 There are some further comments about quoting in the section on LDAP
7214 authentication below.
7217 .section "LDAP connections" "SECID69"
7218 .cindex "LDAP" "connections"
7219 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7220 is in use, via a Unix domain socket. The example given above does not specify
7221 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7224 ldap://<hostname>:<port>/...
7226 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7227 used. When no server is specified in a query, a list of default servers is
7228 taken from the &%ldap_default_servers%& configuration option. This supplies a
7229 colon-separated list of servers which are tried in turn until one successfully
7230 handles a query, or there is a serious error. Successful handling either
7231 returns the requested data, or indicates that it does not exist. Serious errors
7232 are syntactical, or multiple values when only a single value is expected.
7233 Errors which cause the next server to be tried are connection failures, bind
7234 failures, and timeouts.
7236 For each server name in the list, a port number can be given. The standard way
7237 of specifying a host and port is to use a colon separator (RFC 1738). Because
7238 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7239 doubled. For example
7241 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7243 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7244 to the LDAP library with no server name, and the library's default (normally
7245 the local host) is used.
7247 If you are using the OpenLDAP library, you can connect to an LDAP server using
7248 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7249 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7250 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7253 For this type of connection, instead of a host name for the server, a pathname
7254 for the socket is required, and the port number is not relevant. The pathname
7255 can be specified either as an item in &%ldap_default_servers%&, or inline in
7256 the query. In the former case, you can have settings such as
7258 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7260 When the pathname is given in the query, you have to escape the slashes as
7261 &`%2F`& to fit in with the LDAP URL syntax. For example:
7263 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7265 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7266 a pathname, it uses the Unix domain socket code, even if the query actually
7267 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7268 socket connection. This behaviour means that you can use a setting of
7269 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7270 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7271 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7274 If an explicit &`ldapi`& type is given in a query when a host name is
7275 specified, an error is diagnosed. However, if there are more items in
7276 &%ldap_default_servers%&, they are tried. In other words:
7279 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7282 Using &`ldapi`& with a host name causes an error.
7286 Using &`ldapi`& with no host or path in the query, and no setting of
7287 &%ldap_default_servers%&, does whatever the library does by default.
7291 .section "LDAP authentication and control information" "SECID70"
7292 .cindex "LDAP" "authentication"
7293 The LDAP URL syntax provides no way of passing authentication and other control
7294 information to the server. To make this possible, the URL in an LDAP query may
7295 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7296 spaces. If a value contains spaces it must be enclosed in double quotes, and
7297 when double quotes are used, backslash is interpreted in the usual way inside
7298 them. The following names are recognized:
7300 &`DEREFERENCE`& set the dereferencing parameter
7301 &`NETTIME `& set a timeout for a network operation
7302 &`USER `& set the DN, for authenticating the LDAP bind
7303 &`PASS `& set the password, likewise
7304 &`REFERRALS `& set the referrals parameter
7305 &`SERVERS `& set alternate server list for this query only
7306 &`SIZE `& set the limit for the number of entries returned
7307 &`TIME `& set the maximum waiting time for a query
7309 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7310 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7311 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7312 library from trying to follow referrals issued by the LDAP server.
7314 The name CONNECT is an obsolete name for NETTIME, retained for
7315 backwards compatibility. This timeout (specified as a number of seconds) is
7316 enforced from the client end for operations that can be carried out over a
7317 network. Specifically, it applies to network connections and calls to the
7318 &'ldap_result()'& function. If the value is greater than zero, it is used if
7319 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7320 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7321 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7322 Netscape SDK; for OpenLDAP no action is taken.
7324 The TIME parameter (also a number of seconds) is passed to the server to
7325 set a server-side limit on the time taken to complete a search.
7327 The SERVERS parameter allows you to specify an alternate list of ldap servers
7328 to use for an individual lookup. The global &%ldap_default_servers%& option provides a
7329 default list of ldap servers, and a single lookup can specify a single ldap
7330 server to use. But when you need to do a lookup with a list of servers that is
7331 different than the default list (maybe different order, maybe a completely
7332 different set of servers), the SERVERS parameter allows you to specify this
7333 alternate list (colon-separated).
7335 Here is an example of an LDAP query in an Exim lookup that uses some of these
7336 values. This is a single line, folded to fit on the page:
7339 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7340 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7343 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7344 any of the auxiliary data. Exim configuration settings that include lookups
7345 which contain password information should be preceded by &"hide"& to prevent
7346 non-admin users from using the &%-bP%& option to see their values.
7348 The auxiliary data items may be given in any order. The default is no
7349 connection timeout (the system timeout is used), no user or password, no limit
7350 on the number of entries returned, and no time limit on queries.
7352 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7353 removes any URL quoting that it may contain before passing it LDAP. Apparently
7354 some libraries do this for themselves, but some do not. Removing the URL
7355 quoting has two advantages:
7358 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7359 DNs as with DNs inside actual queries.
7361 It permits spaces inside USER= DNs.
7364 For example, a setting such as
7366 USER=cn=${quote_ldap_dn:$1}
7368 should work even if &$1$& contains spaces.
7370 Expanded data for the PASS= value should be quoted using the &%quote%&
7371 expansion operator, rather than the LDAP quote operators. The only reason this
7372 field needs quoting is to ensure that it conforms to the Exim syntax, which
7373 does not allow unquoted spaces. For example:
7377 The LDAP authentication mechanism can be used to check passwords as part of
7378 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7383 .section "Format of data returned by LDAP" "SECID71"
7384 .cindex "LDAP" "returned data formats"
7385 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7386 as a sequence of values, for example
7388 cn=manager, o=University of Cambridge, c=UK
7390 The &(ldap)& lookup type generates an error if more than one entry matches the
7391 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7392 the result between the data from different entries. It is possible for multiple
7393 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7394 you know that whatever values are returned all came from a single entry in the
7397 In the common case where you specify a single attribute in your LDAP query, the
7398 result is not quoted, and does not contain the attribute name. If the attribute
7399 has multiple values, they are separated by commas.
7401 If you specify multiple attributes, the result contains space-separated, quoted
7402 strings, each preceded by the attribute name and an equals sign. Within the
7403 quotes, the quote character, backslash, and newline are escaped with
7404 backslashes, and commas are used to separate multiple values for the attribute.
7405 Any commas in attribute values are doubled
7406 (permitting treatment of the values as a comma-separated list).
7407 Apart from the escaping, the string within quotes takes the same form as the
7408 output when a single attribute is requested. Specifying no attributes is the
7409 same as specifying all of an entry's attributes.
7411 Here are some examples of the output format. The first line of each pair is an
7412 LDAP query, and the second is the data that is returned. The attribute called
7413 &%attr1%& has two values, one of them with an embedded comma, whereas
7414 &%attr2%& has only one value:
7416 ldap:///o=base?attr1?sub?(uid=fred)
7419 ldap:///o=base?attr2?sub?(uid=fred)
7422 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7423 attr1="value1.1,value1,,2" attr2="value two"
7425 ldap:///o=base??sub?(uid=fred)
7426 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
7429 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7430 results of LDAP lookups.
7431 The &%extract%& operator in string expansions can be used to pick out
7432 individual fields from data that consists of &'key'&=&'value'& pairs.
7433 The &%listextract%& operator should be used to pick out individual values
7434 of attributes, even when only a single value is expected.
7435 The doubling of embedded commas allows you to use the returned data as a
7436 comma separated list (using the "<," syntax for changing the input list separator).
7441 .section "More about NIS+" "SECTnisplus"
7442 .cindex "NIS+ lookup type"
7443 .cindex "lookup" "NIS+"
7444 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7445 and field name. If this is given, the result of a successful query is the
7446 contents of the named field; otherwise the result consists of a concatenation
7447 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
7448 values containing spaces are quoted. For example, the query
7450 [name=mg1456],passwd.org_dir
7452 might return the string
7454 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
7455 home=/home/mg1456 shell=/bin/bash shadow=""
7457 (split over two lines here to fit on the page), whereas
7459 [name=mg1456],passwd.org_dir:gcos
7465 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
7466 for the given indexed key. The effect of the &%quote_nisplus%& expansion
7467 operator is to double any quote characters within the text.
7471 .section "SQL lookups" "SECTsql"
7472 .cindex "SQL lookup types"
7473 .cindex "MySQL" "lookup type"
7474 .cindex "PostgreSQL lookup type"
7475 .cindex "lookup" "MySQL"
7476 .cindex "lookup" "PostgreSQL"
7477 .cindex "Oracle" "lookup type"
7478 .cindex "lookup" "Oracle"
7479 .cindex "InterBase lookup type"
7480 .cindex "lookup" "InterBase"
7481 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, and SQLite
7482 databases. Queries for these databases contain SQL statements, so an example
7485 ${lookup mysql{select mailbox from users where id='userx'}\
7488 If the result of the query contains more than one field, the data for each
7489 field in the row is returned, preceded by its name, so the result of
7491 ${lookup pgsql{select home,name from users where id='userx'}\
7496 home=/home/userx name="Mister X"
7498 Empty values and values containing spaces are double quoted, with embedded
7499 quotes escaped by a backslash. If the result of the query contains just one
7500 field, the value is passed back verbatim, without a field name, for example:
7504 If the result of the query yields more than one row, it is all concatenated,
7505 with a newline between the data for each row.
7508 .section "More about MySQL, PostgreSQL, Oracle, and InterBase" "SECID72"
7509 .cindex "MySQL" "lookup type"
7510 .cindex "PostgreSQL lookup type"
7511 .cindex "lookup" "MySQL"
7512 .cindex "lookup" "PostgreSQL"
7513 .cindex "Oracle" "lookup type"
7514 .cindex "lookup" "Oracle"
7515 .cindex "InterBase lookup type"
7516 .cindex "lookup" "InterBase"
7517 If any MySQL, PostgreSQL, Oracle, or InterBase lookups are used, the
7518 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, or &%ibase_servers%&
7519 option (as appropriate) must be set to a colon-separated list of server
7521 (For MySQL and PostgreSQL only, the global option need not be set if all
7522 queries contain their own server information &-- see section
7523 &<<SECTspeserque>>&.) Each item in the list is a slash-separated list of four
7524 items: host name, database name, user name, and password. In the case of
7525 Oracle, the host name field is used for the &"service name"&, and the database
7526 name field is not used and should be empty. For example:
7528 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
7530 Because password data is sensitive, you should always precede the setting with
7531 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
7532 option. Here is an example where two MySQL servers are listed:
7534 hide mysql_servers = localhost/users/root/secret:\
7535 otherhost/users/root/othersecret
7537 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
7538 because this is a colon-separated list, the colon has to be doubled. For each
7539 query, these parameter groups are tried in order until a connection is made and
7540 a query is successfully processed. The result of a query may be that no data is
7541 found, but that is still a successful query. In other words, the list of
7542 servers provides a backup facility, not a list of different places to look.
7545 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
7546 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
7547 respectively, and the characters single-quote, double-quote, and backslash
7548 itself are escaped with backslashes.
7551 .section "Specifying the server in the query" "SECTspeserque"
7552 For MySQL and PostgreSQL lookups (but not currently for Oracle and InterBase),
7553 it is possible to specify a list of servers with an individual query. This is
7554 done by starting the query with
7556 &`servers=`&&'server1:server2:server3:...'&&`;`&
7558 Each item in the list may take one of two forms:
7560 If it contains no slashes it is assumed to be just a host name. The appropriate
7561 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
7562 of the same name, and the remaining parameters (database, user, password) are
7565 If it contains any slashes, it is taken as a complete parameter set.
7567 The list of servers is used in exactly the same way as the global list.
7568 Once a connection to a server has happened and a query has been
7569 successfully executed, processing of the lookup ceases.
7571 This feature is intended for use in master/slave situations where updates
7572 are occurring and you want to update the master rather than a slave. If the
7573 master is in the list as a backup for reading, you might have a global setting
7576 mysql_servers = slave1/db/name/pw:\
7580 In an updating lookup, you could then write:
7582 ${lookup mysql{servers=master; UPDATE ...} }
7584 That query would then be sent only to the master server. If, on the other hand,
7585 the master is not to be used for reading, and so is not present in the global
7586 option, you can still update it by a query of this form:
7588 ${lookup pgsql{servers=master/db/name/pw; UPDATE ...} }
7592 .section "Special MySQL features" "SECID73"
7593 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
7594 causes a connection to the server on the local host by means of a Unix domain
7595 socket. An alternate socket can be specified in parentheses.
7597 An option group name for MySQL option files can be specified in square brackets;
7598 the default value is &"exim"&.
7600 The full syntax of each item in &%mysql_servers%& is:
7602 <&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
7603 <&'database'&>/<&'user'&>/<&'password'&>
7605 Any of the four sub-parts of the first field can be omitted. For normal use on
7606 the local host it can be left blank or set to just &"localhost"&.
7608 No database need be supplied &-- but if it is absent here, it must be given in
7611 If a MySQL query is issued that does not request any data (an insert, update,
7612 or delete command), the result of the lookup is the number of rows affected.
7614 &*Warning*&: This can be misleading. If an update does not actually change
7615 anything (for example, setting a field to the value it already has), the result
7616 is zero because no rows are affected.
7619 .section "Special PostgreSQL features" "SECID74"
7620 PostgreSQL lookups can also use Unix domain socket connections to the database.
7621 This is usually faster and costs less CPU time than a TCP/IP connection.
7622 However it can be used only if the mail server runs on the same machine as the
7623 database server. A configuration line for PostgreSQL via Unix domain sockets
7626 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
7628 In other words, instead of supplying a host name, a path to the socket is
7629 given. The path name is enclosed in parentheses so that its slashes aren't
7630 visually confused with the delimiters for the other server parameters.
7632 If a PostgreSQL query is issued that does not request any data (an insert,
7633 update, or delete command), the result of the lookup is the number of rows
7636 .section "More about SQLite" "SECTsqlite"
7637 .cindex "lookup" "SQLite"
7638 .cindex "sqlite lookup type"
7639 SQLite is different to the other SQL lookups because a file name is required in
7640 addition to the SQL query. An SQLite database is a single file, and there is no
7641 daemon as in the other SQL databases. The interface to Exim requires the name
7642 of the file, as an absolute path, to be given at the start of the query. It is
7643 separated from the query by white space. This means that the path name cannot
7644 contain white space. Here is a lookup expansion example:
7646 ${lookup sqlite {/some/thing/sqlitedb \
7647 select name from aliases where id='userx';}}
7649 In a list, the syntax is similar. For example:
7651 domainlist relay_to_domains = sqlite;/some/thing/sqlitedb \
7652 select * from relays where ip='$sender_host_address';
7654 The only character affected by the &%quote_sqlite%& operator is a single
7655 quote, which it doubles.
7657 The SQLite library handles multiple simultaneous accesses to the database
7658 internally. Multiple readers are permitted, but only one process can
7659 update at once. Attempts to access the database while it is being updated
7660 are rejected after a timeout period, during which the SQLite library
7661 waits for the lock to be released. In Exim, the default timeout is set
7662 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
7668 . ////////////////////////////////////////////////////////////////////////////
7669 . ////////////////////////////////////////////////////////////////////////////
7671 .chapter "Domain, host, address, and local part lists" &&&
7672 "CHAPdomhosaddlists" &&&
7673 "Domain, host, and address lists"
7674 .scindex IIDdohoadli "lists of domains; hosts; etc."
7675 A number of Exim configuration options contain lists of domains, hosts,
7676 email addresses, or local parts. For example, the &%hold_domains%& option
7677 contains a list of domains whose delivery is currently suspended. These lists
7678 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
7679 arguments to expansion conditions such as &%match_domain%&.
7681 Each item in one of these lists is a pattern to be matched against a domain,
7682 host, email address, or local part, respectively. In the sections below, the
7683 different types of pattern for each case are described, but first we cover some
7684 general facilities that apply to all four kinds of list.
7686 Note that other parts of Exim use a &'string list'& which does not
7687 support all the complexity available in
7688 domain, host, address and local part lists.
7692 .section "Expansion of lists" "SECID75"
7693 .cindex "expansion" "of lists"
7694 Each list is expanded as a single string before it is used. The result of
7695 expansion must be a list, possibly containing empty items, which is split up
7696 into separate items for matching. By default, colon is the separator character,
7697 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
7698 &<<SECTempitelis>>& for details of the list syntax; the second of these
7699 discusses the way to specify empty list items.
7702 If the string expansion is forced to fail, Exim behaves as if the item it is
7703 testing (domain, host, address, or local part) is not in the list. Other
7704 expansion failures cause temporary errors.
7706 If an item in a list is a regular expression, backslashes, dollars and possibly
7707 other special characters in the expression must be protected against
7708 misinterpretation by the string expander. The easiest way to do this is to use
7709 the &`\N`& expansion feature to indicate that the contents of the regular
7710 expression should not be expanded. For example, in an ACL you might have:
7712 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
7713 ${lookup{$domain}lsearch{/badsenders/bydomain}}
7715 The first item is a regular expression that is protected from expansion by
7716 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
7717 senders based on the receiving domain.
7722 .section "Negated items in lists" "SECID76"
7723 .cindex "list" "negation"
7724 .cindex "negation" "in lists"
7725 Items in a list may be positive or negative. Negative items are indicated by a
7726 leading exclamation mark, which may be followed by optional white space. A list
7727 defines a set of items (domains, etc). When Exim processes one of these lists,
7728 it is trying to find out whether a domain, host, address, or local part
7729 (respectively) is in the set that is defined by the list. It works like this:
7731 The list is scanned from left to right. If a positive item is matched, the
7732 subject that is being checked is in the set; if a negative item is matched, the
7733 subject is not in the set. If the end of the list is reached without the
7734 subject having matched any of the patterns, it is in the set if the last item
7735 was a negative one, but not if it was a positive one. For example, the list in
7737 domainlist relay_to_domains = !a.b.c : *.b.c
7739 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
7740 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
7741 list is positive. However, if the setting were
7743 domainlist relay_to_domains = !a.b.c
7745 then all domains other than &'a.b.c'& would match because the last item in the
7746 list is negative. In other words, a list that ends with a negative item behaves
7747 as if it had an extra item &`:*`& on the end.
7749 Another way of thinking about positive and negative items in lists is to read
7750 the connector as &"or"& after a positive item and as &"and"& after a negative
7755 .section "File names in lists" "SECTfilnamlis"
7756 .cindex "list" "file name in"
7757 If an item in a domain, host, address, or local part list is an absolute file
7758 name (beginning with a slash character), each line of the file is read and
7759 processed as if it were an independent item in the list, except that further
7760 file names are not allowed,
7761 and no expansion of the data from the file takes place.
7762 Empty lines in the file are ignored, and the file may also contain comment
7766 For domain and host lists, if a # character appears anywhere in a line of the
7767 file, it and all following characters are ignored.
7769 Because local parts may legitimately contain # characters, a comment in an
7770 address list or local part list file is recognized only if # is preceded by
7771 white space or the start of the line. For example:
7773 not#comment@x.y.z # but this is a comment
7777 Putting a file name in a list has the same effect as inserting each line of the
7778 file as an item in the list (blank lines and comments excepted). However, there
7779 is one important difference: the file is read each time the list is processed,
7780 so if its contents vary over time, Exim's behaviour changes.
7782 If a file name is preceded by an exclamation mark, the sense of any match
7783 within the file is inverted. For example, if
7785 hold_domains = !/etc/nohold-domains
7787 and the file contains the lines
7792 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
7793 any domain matching &`*.b.c`& is not.
7797 .section "An lsearch file is not an out-of-line list" "SECID77"
7798 As will be described in the sections that follow, lookups can be used in lists
7799 to provide indexed methods of checking list membership. There has been some
7800 confusion about the way &(lsearch)& lookups work in lists. Because
7801 an &(lsearch)& file contains plain text and is scanned sequentially, it is
7802 sometimes thought that it is allowed to contain wild cards and other kinds of
7803 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
7804 always fixed strings, just as for any other single-key lookup type.
7806 If you want to use a file to contain wild-card patterns that form part of a
7807 list, just give the file name on its own, without a search type, as described
7808 in the previous section. You could also use the &(wildlsearch)& or
7809 &(nwildlsearch)&, but there is no advantage in doing this.
7814 .section "Named lists" "SECTnamedlists"
7815 .cindex "named lists"
7816 .cindex "list" "named"
7817 A list of domains, hosts, email addresses, or local parts can be given a name
7818 which is then used to refer to the list elsewhere in the configuration. This is
7819 particularly convenient if the same list is required in several different
7820 places. It also allows lists to be given meaningful names, which can improve
7821 the readability of the configuration. For example, it is conventional to define
7822 a domain list called &'local_domains'& for all the domains that are handled
7823 locally on a host, using a configuration line such as
7825 domainlist local_domains = localhost:my.dom.example
7827 Named lists are referenced by giving their name preceded by a plus sign, so,
7828 for example, a router that is intended to handle local domains would be
7829 configured with the line
7831 domains = +local_domains
7833 The first router in a configuration is often one that handles all domains
7834 except the local ones, using a configuration with a negated item like this:
7838 domains = ! +local_domains
7839 transport = remote_smtp
7842 The four kinds of named list are created by configuration lines starting with
7843 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
7844 respectively. Then there follows the name that you are defining, followed by an
7845 equals sign and the list itself. For example:
7847 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
7848 addresslist bad_senders = cdb;/etc/badsenders
7850 A named list may refer to other named lists:
7852 domainlist dom1 = first.example : second.example
7853 domainlist dom2 = +dom1 : third.example
7854 domainlist dom3 = fourth.example : +dom2 : fifth.example
7856 &*Warning*&: If the last item in a referenced list is a negative one, the
7857 effect may not be what you intended, because the negation does not propagate
7858 out to the higher level. For example, consider:
7860 domainlist dom1 = !a.b
7861 domainlist dom2 = +dom1 : *.b
7863 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
7864 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
7865 means it matches the second list as well. The effect is not the same as
7867 domainlist dom2 = !a.b : *.b
7869 where &'x.y'& does not match. It's best to avoid negation altogether in
7870 referenced lists if you can.
7872 Named lists may have a performance advantage. When Exim is routing an
7873 address or checking an incoming message, it caches the result of tests on named
7874 lists. So, if you have a setting such as
7876 domains = +local_domains
7878 on several of your routers
7879 or in several ACL statements,
7880 the actual test is done only for the first one. However, the caching works only
7881 if there are no expansions within the list itself or any sublists that it
7882 references. In other words, caching happens only for lists that are known to be
7883 the same each time they are referenced.
7885 By default, there may be up to 16 named lists of each type. This limit can be
7886 extended by changing a compile-time variable. The use of domain and host lists
7887 is recommended for concepts such as local domains, relay domains, and relay
7888 hosts. The default configuration is set up like this.
7892 .section "Named lists compared with macros" "SECID78"
7893 .cindex "list" "named compared with macro"
7894 .cindex "macro" "compared with named list"
7895 At first sight, named lists might seem to be no different from macros in the
7896 configuration file. However, macros are just textual substitutions. If you
7899 ALIST = host1 : host2
7900 auth_advertise_hosts = !ALIST
7902 it probably won't do what you want, because that is exactly the same as
7904 auth_advertise_hosts = !host1 : host2
7906 Notice that the second host name is not negated. However, if you use a host
7909 hostlist alist = host1 : host2
7910 auth_advertise_hosts = ! +alist
7912 the negation applies to the whole list, and so that is equivalent to
7914 auth_advertise_hosts = !host1 : !host2
7918 .section "Named list caching" "SECID79"
7919 .cindex "list" "caching of named"
7920 .cindex "caching" "named lists"
7921 While processing a message, Exim caches the result of checking a named list if
7922 it is sure that the list is the same each time. In practice, this means that
7923 the cache operates only if the list contains no $ characters, which guarantees
7924 that it will not change when it is expanded. Sometimes, however, you may have
7925 an expanded list that you know will be the same each time within a given
7926 message. For example:
7928 domainlist special_domains = \
7929 ${lookup{$sender_host_address}cdb{/some/file}}
7931 This provides a list of domains that depends only on the sending host's IP
7932 address. If this domain list is referenced a number of times (for example,
7933 in several ACL lines, or in several routers) the result of the check is not
7934 cached by default, because Exim does not know that it is going to be the
7935 same list each time.
7937 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
7938 cache the result anyway. For example:
7940 domainlist_cache special_domains = ${lookup{...
7942 If you do this, you should be absolutely sure that caching is going to do
7943 the right thing in all cases. When in doubt, leave it out.
7947 .section "Domain lists" "SECTdomainlist"
7948 .cindex "domain list" "patterns for"
7949 .cindex "list" "domain list"
7950 Domain lists contain patterns that are to be matched against a mail domain.
7951 The following types of item may appear in domain lists:
7954 .cindex "primary host name"
7955 .cindex "host name" "matched in domain list"
7956 .oindex "&%primary_hostname%&"
7957 .cindex "domain list" "matching primary host name"
7958 .cindex "@ in a domain list"
7959 If a pattern consists of a single @ character, it matches the local host name,
7960 as set by the &%primary_hostname%& option (or defaulted). This makes it
7961 possible to use the same configuration file on several different hosts that
7962 differ only in their names.
7964 .cindex "@[] in a domain list"
7965 .cindex "domain list" "matching local IP interfaces"
7966 .cindex "domain literal"
7967 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
7968 in square brackets (as in an email address that contains a domain literal), but
7969 only if that IP address is recognized as local for email routing purposes. The
7970 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
7971 control which of a host's several IP addresses are treated as local.
7972 In today's Internet, the use of domain literals is controversial.
7975 .cindex "@mx_primary"
7976 .cindex "@mx_secondary"
7977 .cindex "domain list" "matching MX pointers to local host"
7978 If a pattern consists of the string &`@mx_any`& it matches any domain that
7979 has an MX record pointing to the local host or to any host that is listed in
7980 .oindex "&%hosts_treat_as_local%&"
7981 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
7982 are similar, except that the first matches only when a primary MX target is the
7983 local host, and the second only when no primary MX target is the local host,
7984 but a secondary MX target is. &"Primary"& means an MX record with the lowest
7985 preference value &-- there may of course be more than one of them.
7987 The MX lookup that takes place when matching a pattern of this type is
7988 performed with the resolver options for widening names turned off. Thus, for
7989 example, a single-component domain will &'not'& be expanded by adding the
7990 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
7991 options of the &(dnslookup)& router for a discussion of domain widening.
7993 Sometimes you may want to ignore certain IP addresses when using one of these
7994 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
7995 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
7996 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
7997 on a router). For example:
7999 domains = @mx_any/ignore=127.0.0.1
8001 This example matches any domain that has an MX record pointing to one of
8002 the local host's IP addresses other than 127.0.0.1.
8004 The list of IP addresses is in fact processed by the same code that processes
8005 host lists, so it may contain CIDR-coded network specifications and it may also
8006 contain negative items.
8008 Because the list of IP addresses is a sublist within a domain list, you have to
8009 be careful about delimiters if there is more than one address. Like any other
8010 list, the default delimiter can be changed. Thus, you might have:
8012 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
8013 an.other.domain : ...
8015 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
8016 involved, it is easiest to change the delimiter for the main list as well:
8018 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
8019 an.other.domain ? ...
8022 .cindex "asterisk" "in domain list"
8023 .cindex "domain list" "asterisk in"
8024 .cindex "domain list" "matching &""ends with""&"
8025 If a pattern starts with an asterisk, the remaining characters of the pattern
8026 are compared with the terminating characters of the domain. The use of &"*"& in
8027 domain lists differs from its use in partial matching lookups. In a domain
8028 list, the character following the asterisk need not be a dot, whereas partial
8029 matching works only in terms of dot-separated components. For example, a domain
8030 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
8034 .cindex "regular expressions" "in domain list"
8035 .cindex "domain list" "matching regular expression"
8036 If a pattern starts with a circumflex character, it is treated as a regular
8037 expression, and matched against the domain using a regular expression matching
8038 function. The circumflex is treated as part of the regular expression.
8039 Email domains are case-independent, so this regular expression match is by
8040 default case-independent, but you can make it case-dependent by starting it
8041 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
8042 are given in chapter &<<CHAPregexp>>&.
8044 &*Warning*&: Because domain lists are expanded before being processed, you
8045 must escape any backslash and dollar characters in the regular expression, or
8046 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
8047 it is not to be expanded (unless you really do want to build a regular
8048 expression by expansion, of course).
8050 .cindex "lookup" "in domain list"
8051 .cindex "domain list" "matching by lookup"
8052 If a pattern starts with the name of a single-key lookup type followed by a
8053 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
8054 must be a file name in a suitable format for the lookup type. For example, for
8055 &"cdb;"& it must be an absolute path:
8057 domains = cdb;/etc/mail/local_domains.cdb
8059 The appropriate type of lookup is done on the file using the domain name as the
8060 key. In most cases, the data that is looked up is not used; Exim is interested
8061 only in whether or not the key is present in the file. However, when a lookup
8062 is used for the &%domains%& option on a router
8063 or a &%domains%& condition in an ACL statement, the data is preserved in the
8064 &$domain_data$& variable and can be referred to in other router options or
8065 other statements in the same ACL.
8068 Any of the single-key lookup type names may be preceded by
8069 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8071 domains = partial-dbm;/partial/domains
8073 This causes partial matching logic to be invoked; a description of how this
8074 works is given in section &<<SECTpartiallookup>>&.
8077 .cindex "asterisk" "in lookup type"
8078 Any of the single-key lookup types may be followed by an asterisk. This causes
8079 a default lookup for a key consisting of a single asterisk to be done if the
8080 original lookup fails. This is not a useful feature when using a domain list to
8081 select particular domains (because any domain would match), but it might have
8082 value if the result of the lookup is being used via the &$domain_data$&
8085 If the pattern starts with the name of a query-style lookup type followed by a
8086 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8087 pattern must be an appropriate query for the lookup type, as described in
8088 chapter &<<CHAPfdlookup>>&. For example:
8090 hold_domains = mysql;select domain from holdlist \
8091 where domain = '${quote_mysql:$domain}';
8093 In most cases, the data that is looked up is not used (so for an SQL query, for
8094 example, it doesn't matter what field you select). Exim is interested only in
8095 whether or not the query succeeds. However, when a lookup is used for the
8096 &%domains%& option on a router, the data is preserved in the &$domain_data$&
8097 variable and can be referred to in other options.
8099 .cindex "domain list" "matching literal domain name"
8100 If none of the above cases apply, a caseless textual comparison is made
8101 between the pattern and the domain.
8104 Here is an example that uses several different kinds of pattern:
8106 domainlist funny_domains = \
8109 *.foundation.fict.example : \
8110 \N^[1-2]\d{3}\.fict\.example$\N : \
8111 partial-dbm;/opt/data/penguin/book : \
8112 nis;domains.byname : \
8113 nisplus;[name=$domain,status=local],domains.org_dir
8115 There are obvious processing trade-offs among the various matching modes. Using
8116 an asterisk is faster than a regular expression, and listing a few names
8117 explicitly probably is too. The use of a file or database lookup is expensive,
8118 but may be the only option if hundreds of names are required. Because the
8119 patterns are tested in order, it makes sense to put the most commonly matched
8124 .section "Host lists" "SECThostlist"
8125 .cindex "host list" "patterns in"
8126 .cindex "list" "host list"
8127 Host lists are used to control what remote hosts are allowed to do. For
8128 example, some hosts may be allowed to use the local host as a relay, and some
8129 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8130 two different ways, by name or by IP address. In a host list, some types of
8131 pattern are matched to a host name, and some are matched to an IP address.
8132 You need to be particularly careful with this when single-key lookups are
8133 involved, to ensure that the right value is being used as the key.
8136 .section "Special host list patterns" "SECID80"
8137 .cindex "empty item in hosts list"
8138 .cindex "host list" "empty string in"
8139 If a host list item is the empty string, it matches only when no remote host is
8140 involved. This is the case when a message is being received from a local
8141 process using SMTP on the standard input, that is, when a TCP/IP connection is
8144 .cindex "asterisk" "in host list"
8145 The special pattern &"*"& in a host list matches any host or no host. Neither
8146 the IP address nor the name is actually inspected.
8150 .section "Host list patterns that match by IP address" "SECThoslispatip"
8151 .cindex "host list" "matching IP addresses"
8152 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8153 the incoming address actually appears in the IPv6 host as
8154 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8155 list, it is converted into a traditional IPv4 address first. (Not all operating
8156 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8159 The following types of pattern in a host list check the remote host by
8160 inspecting its IP address:
8163 If the pattern is a plain domain name (not a regular expression, not starting
8164 with *, not a lookup of any kind), Exim calls the operating system function
8165 to find the associated IP address(es). Exim uses the newer
8166 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8167 This typically causes a forward DNS lookup of the name. The result is compared
8168 with the IP address of the subject host.
8170 If there is a temporary problem (such as a DNS timeout) with the host name
8171 lookup, a temporary error occurs. For example, if the list is being used in an
8172 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8173 temporary SMTP error code. If no IP address can be found for the host name,
8174 what happens is described in section &<<SECTbehipnot>>& below.
8177 .cindex "@ in a host list"
8178 If the pattern is &"@"&, the primary host name is substituted and used as a
8179 domain name, as just described.
8182 If the pattern is an IP address, it is matched against the IP address of the
8183 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8184 IPv6 addresses can be given in colon-separated format, but the colons have to
8185 be doubled so as not to be taken as item separators when the default list
8186 separator is used. IPv6 addresses are recognized even when Exim is compiled
8187 without IPv6 support. This means that if they appear in a host list on an
8188 IPv4-only host, Exim will not treat them as host names. They are just addresses
8189 that can never match a client host.
8192 .cindex "@[] in a host list"
8193 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8194 the local host. For example, if the local host is an IPv4 host with one
8195 interface address 10.45.23.56, these two ACL statements have the same effect:
8197 accept hosts = 127.0.0.1 : 10.45.23.56
8201 .cindex "CIDR notation"
8202 If the pattern is an IP address followed by a slash and a mask length (for
8203 example 10.11.42.0/24), it is matched against the IP address of the subject
8204 host under the given mask. This allows, an entire network of hosts to be
8205 included (or excluded) by a single item. The mask uses CIDR notation; it
8206 specifies the number of address bits that must match, starting from the most
8207 significant end of the address.
8209 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8210 of a range of addresses. It is the number of bits in the network portion of the
8211 address. The above example specifies a 24-bit netmask, so it matches all 256
8212 addresses in the 10.11.42.0 network. An item such as
8216 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8217 32 for an IPv4 address is the same as no mask at all; just a single address
8220 Here is another example which shows an IPv4 and an IPv6 network:
8222 recipient_unqualified_hosts = 192.168.0.0/16: \
8223 3ffe::ffff::836f::::/48
8225 The doubling of list separator characters applies only when these items
8226 appear inline in a host list. It is not required when indirecting via a file.
8229 recipient_unqualified_hosts = /opt/exim/unqualnets
8231 could make use of a file containing
8236 to have exactly the same effect as the previous example. When listing IPv6
8237 addresses inline, it is usually more convenient to use the facility for
8238 changing separator characters. This list contains the same two networks:
8240 recipient_unqualified_hosts = <; 172.16.0.0/12; \
8243 The separator is changed to semicolon by the leading &"<;"& at the start of the
8249 .section "Host list patterns for single-key lookups by host address" &&&
8250 "SECThoslispatsikey"
8251 .cindex "host list" "lookup of IP address"
8252 When a host is to be identified by a single-key lookup of its complete IP
8253 address, the pattern takes this form:
8255 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8259 hosts_lookup = net-cdb;/hosts-by-ip.db
8261 The text form of the IP address of the subject host is used as the lookup key.
8262 IPv6 addresses are converted to an unabbreviated form, using lower case
8263 letters, with dots as separators because colon is the key terminator in
8264 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
8265 quoting the keys, but this is a facility that was added later.] The data
8266 returned by the lookup is not used.
8268 .cindex "IP address" "masking"
8269 .cindex "host list" "masked IP address"
8270 Single-key lookups can also be performed using masked IP addresses, using
8271 patterns of this form:
8273 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8277 net24-dbm;/networks.db
8279 The IP address of the subject host is masked using <&'number'&> as the mask
8280 length. A textual string is constructed from the masked value, followed by the
8281 mask, and this is used as the lookup key. For example, if the host's IP address
8282 is 192.168.34.6, the key that is looked up for the above example is
8283 &"192.168.34.0/24"&.
8285 When an IPv6 address is converted to a string, dots are normally used instead
8286 of colons, so that keys in &(lsearch)& files need not contain colons (which
8287 terminate &(lsearch)& keys). This was implemented some time before the ability
8288 to quote keys was made available in &(lsearch)& files. However, the more
8289 recently implemented &(iplsearch)& files do require colons in IPv6 keys
8290 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
8291 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
8292 converted using colons and not dots. In all cases, full, unabbreviated IPv6
8293 addresses are always used.
8295 Ideally, it would be nice to tidy up this anomalous situation by changing to
8296 colons in all cases, given that quoting is now available for &(lsearch)&.
8297 However, this would be an incompatible change that might break some existing
8300 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
8301 IPv6 address) is not the same as specifying just &%net-%& without a number. In
8302 the former case the key strings include the mask value, whereas in the latter
8303 case the IP address is used on its own.
8307 .section "Host list patterns that match by host name" "SECThoslispatnam"
8308 .cindex "host" "lookup failures"
8309 .cindex "unknown host name"
8310 .cindex "host list" "matching host name"
8311 There are several types of pattern that require Exim to know the name of the
8312 remote host. These are either wildcard patterns or lookups by name. (If a
8313 complete hostname is given without any wildcarding, it is used to find an IP
8314 address to match against, as described in section &<<SECThoslispatip>>&
8317 If the remote host name is not already known when Exim encounters one of these
8318 patterns, it has to be found from the IP address.
8319 Although many sites on the Internet are conscientious about maintaining reverse
8320 DNS data for their hosts, there are also many that do not do this.
8321 Consequently, a name cannot always be found, and this may lead to unwanted
8322 effects. Take care when configuring host lists with wildcarded name patterns.
8323 Consider what will happen if a name cannot be found.
8325 Because of the problems of determining host names from IP addresses, matching
8326 against host names is not as common as matching against IP addresses.
8328 By default, in order to find a host name, Exim first does a reverse DNS lookup;
8329 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
8330 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
8331 are done can be changed by setting the &%host_lookup_order%& option. For
8332 security, once Exim has found one or more names, it looks up the IP addresses
8333 for these names and compares them with the IP address that it started with.
8334 Only those names whose IP addresses match are accepted. Any other names are
8335 discarded. If no names are left, Exim behaves as if the host name cannot be
8336 found. In the most common case there is only one name and one IP address.
8338 There are some options that control what happens if a host name cannot be
8339 found. These are described in section &<<SECTbehipnot>>& below.
8341 .cindex "host" "alias for"
8342 .cindex "alias for host"
8343 As a result of aliasing, hosts may have more than one name. When processing any
8344 of the following types of pattern, all the host's names are checked:
8347 .cindex "asterisk" "in host list"
8348 If a pattern starts with &"*"& the remainder of the item must match the end of
8349 the host name. For example, &`*.b.c`& matches all hosts whose names end in
8350 &'.b.c'&. This special simple form is provided because this is a very common
8351 requirement. Other kinds of wildcarding require the use of a regular
8354 .cindex "regular expressions" "in host list"
8355 .cindex "host list" "regular expression in"
8356 If the item starts with &"^"& it is taken to be a regular expression which is
8357 matched against the host name. Host names are case-independent, so this regular
8358 expression match is by default case-independent, but you can make it
8359 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
8360 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
8365 is a regular expression that matches either of the two hosts &'a.c.d'& or
8366 &'b.c.d'&. When a regular expression is used in a host list, you must take care
8367 that backslash and dollar characters are not misinterpreted as part of the
8368 string expansion. The simplest way to do this is to use &`\N`& to mark that
8369 part of the string as non-expandable. For example:
8371 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
8373 &*Warning*&: If you want to match a complete host name, you must include the
8374 &`$`& terminating metacharacter in the regular expression, as in the above
8375 example. Without it, a match at the start of the host name is all that is
8382 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
8383 .cindex "host" "lookup failures, permanent"
8384 While processing a host list, Exim may need to look up an IP address from a
8385 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
8386 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
8387 behaviour when it fails to find the information it is seeking is the same.
8389 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
8390 apply to temporary DNS errors, whose handling is described in the next section.
8392 .cindex "&`+include_unknown`&"
8393 .cindex "&`+ignore_unknown`&"
8394 Exim parses a host list from left to right. If it encounters a permanent
8395 lookup failure in any item in the host list before it has found a match,
8396 Exim treats it as a failure and the default behavior is as if the host
8397 does not match the list. This may not always be what you want to happen.
8398 To change Exim's behaviour, the special items &`+include_unknown`& or
8399 &`+ignore_unknown`& may appear in the list (at top level &-- they are
8400 not recognized in an indirected file).
8403 If any item that follows &`+include_unknown`& requires information that
8404 cannot found, Exim behaves as if the host does match the list. For example,
8406 host_reject_connection = +include_unknown:*.enemy.ex
8408 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
8409 any hosts whose name it cannot find.
8412 If any item that follows &`+ignore_unknown`& requires information that cannot
8413 be found, Exim ignores that item and proceeds to the rest of the list. For
8416 accept hosts = +ignore_unknown : friend.example : \
8419 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
8420 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
8421 name can be found for 192.168.4.5, it is rejected.
8424 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
8425 list. The effect of each one lasts until the next, or until the end of the
8428 .section "Mixing wildcarded host names and addresses in host lists" &&&
8430 .cindex "host list" "mixing names and addresses in"
8432 This section explains the host/ip processing logic with the same concepts
8433 as the previous section, but specifically addresses what happens when a
8434 wildcarded hostname is one of the items in the hostlist.
8437 If you have name lookups or wildcarded host names and
8438 IP addresses in the same host list, you should normally put the IP
8439 addresses first. For example, in an ACL you could have:
8441 accept hosts = 10.9.8.7 : *.friend.example
8443 The reason you normally would order it this way lies in the
8444 left-to-right way that Exim processes lists. It can test IP addresses
8445 without doing any DNS lookups, but when it reaches an item that requires
8446 a host name, it fails if it cannot find a host name to compare with the
8447 pattern. If the above list is given in the opposite order, the
8448 &%accept%& statement fails for a host whose name cannot be found, even
8449 if its IP address is 10.9.8.7.
8452 If you really do want to do the name check first, and still recognize the IP
8453 address, you can rewrite the ACL like this:
8455 accept hosts = *.friend.example
8456 accept hosts = 10.9.8.7
8458 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
8459 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
8460 &`+ignore_unknown`&, which was discussed in depth in the first example in
8465 .section "Temporary DNS errors when looking up host information" &&&
8467 .cindex "host" "lookup failures, temporary"
8468 .cindex "&`+include_defer`&"
8469 .cindex "&`+ignore_defer`&"
8470 A temporary DNS lookup failure normally causes a defer action (except when
8471 &%dns_again_means_nonexist%& converts it into a permanent error). However,
8472 host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
8473 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
8474 section. These options should be used with care, probably only in non-critical
8475 host lists such as whitelists.
8479 .section "Host list patterns for single-key lookups by host name" &&&
8480 "SECThoslispatnamsk"
8481 .cindex "unknown host name"
8482 .cindex "host list" "matching host name"
8483 If a pattern is of the form
8485 <&'single-key-search-type'&>;<&'search-data'&>
8489 dbm;/host/accept/list
8491 a single-key lookup is performed, using the host name as its key. If the
8492 lookup succeeds, the host matches the item. The actual data that is looked up
8495 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
8496 keys in the file, not IP addresses. If you want to do lookups based on IP
8497 addresses, you must precede the search type with &"net-"& (see section
8498 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
8499 two items in the same list, one doing an address lookup and one doing a name
8500 lookup, both using the same file.
8504 .section "Host list patterns for query-style lookups" "SECID81"
8505 If a pattern is of the form
8507 <&'query-style-search-type'&>;<&'query'&>
8509 the query is obeyed, and if it succeeds, the host matches the item. The actual
8510 data that is looked up is not used. The variables &$sender_host_address$& and
8511 &$sender_host_name$& can be used in the query. For example:
8513 hosts_lookup = pgsql;\
8514 select ip from hostlist where ip='$sender_host_address'
8516 The value of &$sender_host_address$& for an IPv6 address contains colons. You
8517 can use the &%sg%& expansion item to change this if you need to. If you want to
8518 use masked IP addresses in database queries, you can use the &%mask%& expansion
8521 If the query contains a reference to &$sender_host_name$&, Exim automatically
8522 looks up the host name if it has not already done so. (See section
8523 &<<SECThoslispatnam>>& for comments on finding host names.)
8525 Historical note: prior to release 4.30, Exim would always attempt to find a
8526 host name before running the query, unless the search type was preceded by
8527 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
8528 still recognized for query-style lookups, but its presence or absence has no
8529 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
8530 See section &<<SECThoslispatsikey>>&.)
8536 .section "Address lists" "SECTaddresslist"
8537 .cindex "list" "address list"
8538 .cindex "address list" "empty item"
8539 .cindex "address list" "patterns"
8540 Address lists contain patterns that are matched against mail addresses. There
8541 is one special case to be considered: the sender address of a bounce message is
8542 always empty. You can test for this by providing an empty item in an address
8543 list. For example, you can set up a router to process bounce messages by
8544 using this option setting:
8548 The presence of the colon creates an empty item. If you do not provide any
8549 data, the list is empty and matches nothing. The empty sender can also be
8550 detected by a regular expression that matches an empty string,
8551 and by a query-style lookup that succeeds when &$sender_address$& is empty.
8553 Non-empty items in an address list can be straightforward email addresses. For
8556 senders = jbc@askone.example : hs@anacreon.example
8558 A certain amount of wildcarding is permitted. If a pattern contains an @
8559 character, but is not a regular expression and does not begin with a
8560 semicolon-terminated lookup type (described below), the local part of the
8561 subject address is compared with the local part of the pattern, which may start
8562 with an asterisk. If the local parts match, the domain is checked in exactly
8563 the same way as for a pattern in a domain list. For example, the domain can be
8564 wildcarded, refer to a named list, or be a lookup:
8566 deny senders = *@*.spamming.site:\
8567 *@+hostile_domains:\
8568 bozo@partial-lsearch;/list/of/dodgy/sites:\
8569 *@dbm;/bad/domains.db
8571 .cindex "local part" "starting with !"
8572 .cindex "address list" "local part starting with !"
8573 If a local part that begins with an exclamation mark is required, it has to be
8574 specified using a regular expression, because otherwise the exclamation mark is
8575 treated as a sign of negation, as is standard in lists.
8577 If a non-empty pattern that is not a regular expression or a lookup does not
8578 contain an @ character, it is matched against the domain part of the subject
8579 address. The only two formats that are recognized this way are a literal
8580 domain, or a domain pattern that starts with *. In both these cases, the effect
8581 is the same as if &`*@`& preceded the pattern. For example:
8583 deny senders = enemy.domain : *.enemy.domain
8586 The following kinds of more complicated address list pattern can match any
8587 address, including the empty address that is characteristic of bounce message
8591 .cindex "regular expressions" "in address list"
8592 .cindex "address list" "regular expression in"
8593 If (after expansion) a pattern starts with &"^"&, a regular expression match is
8594 done against the complete address, with the pattern as the regular expression.
8595 You must take care that backslash and dollar characters are not misinterpreted
8596 as part of the string expansion. The simplest way to do this is to use &`\N`&
8597 to mark that part of the string as non-expandable. For example:
8599 deny senders = \N^.*this.*@example\.com$\N : \
8600 \N^\d{8}.+@spamhaus.example$\N : ...
8602 The &`\N`& sequences are removed by the expansion, so these items do indeed
8603 start with &"^"& by the time they are being interpreted as address patterns.
8606 .cindex "address list" "lookup for complete address"
8607 Complete addresses can be looked up by using a pattern that starts with a
8608 lookup type terminated by a semicolon, followed by the data for the lookup. For
8611 deny senders = cdb;/etc/blocked.senders : \
8612 mysql;select address from blocked where \
8613 address='${quote_mysql:$sender_address}'
8615 Both query-style and single-key lookup types can be used. For a single-key
8616 lookup type, Exim uses the complete address as the key. However, empty keys are
8617 not supported for single-key lookups, so a match against the empty address
8618 always fails. This restriction does not apply to query-style lookups.
8620 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
8621 cannot be used, and is ignored if specified, with an entry being written to the
8623 .cindex "*@ with single-key lookup"
8624 However, you can configure lookup defaults, as described in section
8625 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
8626 default. For example, with this lookup:
8628 accept senders = lsearch*@;/some/file
8630 the file could contains lines like this:
8632 user1@domain1.example
8635 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
8638 nimrod@jaeger.example
8642 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
8643 would mean that every address matches, thus rendering the test useless.
8645 &*Warning 2*&: Do not confuse these two kinds of item:
8647 deny recipients = dbm*@;/some/file
8648 deny recipients = *@dbm;/some/file
8650 The first does a whole address lookup, with defaulting, as just described,
8651 because it starts with a lookup type. The second matches the local part and
8652 domain independently, as described in a bullet point below.
8656 The following kinds of address list pattern can match only non-empty addresses.
8657 If the subject address is empty, a match against any of these pattern types
8662 .cindex "@@ with single-key lookup"
8663 .cindex "address list" "@@ lookup type"
8664 .cindex "address list" "split local part and domain"
8665 If a pattern starts with &"@@"& followed by a single-key lookup item
8666 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
8667 split into a local part and a domain. The domain is looked up in the file. If
8668 it is not found, there is no match. If it is found, the data that is looked up
8669 from the file is treated as a colon-separated list of local part patterns, each
8670 of which is matched against the subject local part in turn.
8672 .cindex "asterisk" "in address list"
8673 The lookup may be a partial one, and/or one involving a search for a default
8674 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
8675 patterns that are looked up can be regular expressions or begin with &"*"&, or
8676 even be further lookups. They may also be independently negated. For example,
8679 deny senders = @@dbm;/etc/reject-by-domain
8681 the data from which the DBM file is built could contain lines like
8683 baddomain.com: !postmaster : *
8685 to reject all senders except &%postmaster%& from that domain.
8687 .cindex "local part" "starting with !"
8688 If a local part that actually begins with an exclamation mark is required, it
8689 has to be specified using a regular expression. In &(lsearch)& files, an entry
8690 may be split over several lines by indenting the second and subsequent lines,
8691 but the separating colon must still be included at line breaks. White space
8692 surrounding the colons is ignored. For example:
8694 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
8697 As in all colon-separated lists in Exim, a colon can be included in an item by
8700 If the last item in the list starts with a right angle-bracket, the remainder
8701 of the item is taken as a new key to look up in order to obtain a continuation
8702 list of local parts. The new key can be any sequence of characters. Thus one
8703 might have entries like
8705 aol.com: spammer1 : spammer 2 : >*
8706 xyz.com: spammer3 : >*
8709 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
8710 local parts for all domains, in addition to the specific local parts listed for
8711 each domain. Of course, using this feature costs another lookup each time a
8712 chain is followed, but the effort needed to maintain the data is reduced.
8714 .cindex "loop" "in lookups"
8715 It is possible to construct loops using this facility, and in order to catch
8716 them, the chains may be no more than fifty items long.
8719 The @@<&'lookup'&> style of item can also be used with a query-style
8720 lookup, but in this case, the chaining facility is not available. The lookup
8721 can only return a single list of local parts.
8724 &*Warning*&: There is an important difference between the address list items
8725 in these two examples:
8728 senders = *@+my_list
8730 In the first one, &`my_list`& is a named address list, whereas in the second
8731 example it is a named domain list.
8736 .section "Case of letters in address lists" "SECTcasletadd"
8737 .cindex "case of local parts"
8738 .cindex "address list" "case forcing"
8739 .cindex "case forcing in address lists"
8740 Domains in email addresses are always handled caselessly, but for local parts
8741 case may be significant on some systems (see &%caseful_local_part%& for how
8742 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
8743 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
8744 blocking lists should be done in a case-independent manner. Since most address
8745 lists in Exim are used for this kind of control, Exim attempts to do this by
8748 The domain portion of an address is always lowercased before matching it to an
8749 address list. The local part is lowercased by default, and any string
8750 comparisons that take place are done caselessly. This means that the data in
8751 the address list itself, in files included as plain file names, and in any file
8752 that is looked up using the &"@@"& mechanism, can be in any case. However, the
8753 keys in files that are looked up by a search type other than &(lsearch)& (which
8754 works caselessly) must be in lower case, because these lookups are not
8757 .cindex "&`+caseful`&"
8758 To allow for the possibility of caseful address list matching, if an item in
8759 an address list is the string &"+caseful"&, the original case of the local
8760 part is restored for any comparisons that follow, and string comparisons are no
8761 longer case-independent. This does not affect the domain, which remains in
8762 lower case. However, although independent matches on the domain alone are still
8763 performed caselessly, regular expressions that match against an entire address
8764 become case-sensitive after &"+caseful"& has been seen.
8768 .section "Local part lists" "SECTlocparlis"
8769 .cindex "list" "local part list"
8770 .cindex "local part" "list"
8771 Case-sensitivity in local part lists is handled in the same way as for address
8772 lists, as just described. The &"+caseful"& item can be used if required. In a
8773 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
8774 set false, the subject is lowercased and the matching is initially
8775 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
8776 matching in the local part list, but not elsewhere in the router. If
8777 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
8778 option is case-sensitive from the start.
8780 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
8781 comments are handled in the same way as address lists &-- they are recognized
8782 only if the # is preceded by white space or the start of the line.
8783 Otherwise, local part lists are matched in the same way as domain lists, except
8784 that the special items that refer to the local host (&`@`&, &`@[]`&,
8785 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
8786 Refer to section &<<SECTdomainlist>>& for details of the other available item
8788 .ecindex IIDdohoadli
8793 . ////////////////////////////////////////////////////////////////////////////
8794 . ////////////////////////////////////////////////////////////////////////////
8796 .chapter "String expansions" "CHAPexpand"
8797 .scindex IIDstrexp "expansion" "of strings"
8798 Many strings in Exim's run time configuration are expanded before use. Some of
8799 them are expanded every time they are used; others are expanded only once.
8801 When a string is being expanded it is copied verbatim from left to right except
8802 when a dollar or backslash character is encountered. A dollar specifies the
8803 start of a portion of the string that is interpreted and replaced as described
8804 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
8805 escape character, as described in the following section.
8807 Whether a string is expanded depends upon the context. Usually this is solely
8808 dependent upon the option for which a value is sought; in this documentation,
8809 options for which string expansion is performed are marked with † after
8810 the data type. ACL rules always expand strings. A couple of expansion
8811 conditions do not expand some of the brace-delimited branches, for security
8816 .section "Literal text in expanded strings" "SECTlittext"
8817 .cindex "expansion" "including literal text"
8818 An uninterpreted dollar can be included in an expanded string by putting a
8819 backslash in front of it. A backslash can be used to prevent any special
8820 character being treated specially in an expansion, including backslash itself.
8821 If the string appears in quotes in the configuration file, two backslashes are
8822 required because the quotes themselves cause interpretation of backslashes when
8823 the string is read in (see section &<<SECTstrings>>&).
8825 .cindex "expansion" "non-expandable substrings"
8826 A portion of the string can specified as non-expandable by placing it between
8827 two occurrences of &`\N`&. This is particularly useful for protecting regular
8828 expressions, which often contain backslashes and dollar signs. For example:
8830 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
8832 On encountering the first &`\N`&, the expander copies subsequent characters
8833 without interpretation until it reaches the next &`\N`& or the end of the
8838 .section "Character escape sequences in expanded strings" "SECID82"
8839 .cindex "expansion" "escape sequences"
8840 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
8841 expanded string is recognized as an escape sequence for the character newline,
8842 carriage return, or tab, respectively. A backslash followed by up to three
8843 octal digits is recognized as an octal encoding for a single character, and a
8844 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
8847 These escape sequences are also recognized in quoted strings when they are read
8848 in. Their interpretation in expansions as well is useful for unquoted strings,
8849 and for other cases such as looked-up strings that are then expanded.
8852 .section "Testing string expansions" "SECID83"
8853 .cindex "expansion" "testing"
8854 .cindex "testing" "string expansion"
8856 Many expansions can be tested by calling Exim with the &%-be%& option. This
8857 takes the command arguments, or lines from the standard input if there are no
8858 arguments, runs them through the string expansion code, and writes the results
8859 to the standard output. Variables based on configuration values are set up, but
8860 since no message is being processed, variables such as &$local_part$& have no
8861 value. Nevertheless the &%-be%& option can be useful for checking out file and
8862 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
8865 Exim gives up its root privilege when it is called with the &%-be%& option, and
8866 instead runs under the uid and gid it was called with, to prevent users from
8867 using &%-be%& for reading files to which they do not have access.
8870 If you want to test expansions that include variables whose values are taken
8871 from a message, there are two other options that can be used. The &%-bem%&
8872 option is like &%-be%& except that it is followed by a file name. The file is
8873 read as a message before doing the test expansions. For example:
8875 exim -bem /tmp/test.message '$h_subject:'
8877 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
8878 Exim message identifier. For example:
8880 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
8882 This loads the message from Exim's spool before doing the test expansions, and
8883 is therefore restricted to admin users.
8886 .section "Forced expansion failure" "SECTforexpfai"
8887 .cindex "expansion" "forced failure"
8888 A number of expansions that are described in the following section have
8889 alternative &"true"& and &"false"& substrings, enclosed in brace characters
8890 (which are sometimes called &"curly brackets"&). Which of the two strings is
8891 used depends on some condition that is evaluated as part of the expansion. If,
8892 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
8893 the entire string expansion fails in a way that can be detected by the code
8894 that requested the expansion. This is called &"forced expansion failure"&, and
8895 its consequences depend on the circumstances. In some cases it is no different
8896 from any other expansion failure, but in others a different action may be
8897 taken. Such variations are mentioned in the documentation of the option that is
8903 .section "Expansion items" "SECTexpansionitems"
8904 The following items are recognized in expanded strings. White space may be used
8905 between sub-items that are keywords or substrings enclosed in braces inside an
8906 outer set of braces, to improve readability. &*Warning*&: Within braces,
8907 white space is significant.
8910 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
8911 .cindex "expansion" "variables"
8912 Substitute the contents of the named variable, for example:
8917 The second form can be used to separate the name from subsequent alphanumeric
8918 characters. This form (using braces) is available only for variables; it does
8919 &'not'& apply to message headers. The names of the variables are given in
8920 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
8921 given, the expansion fails.
8923 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
8924 .cindex "expansion" "operators"
8925 The string is first itself expanded, and then the operation specified by
8926 <&'op'&> is applied to it. For example:
8930 The string starts with the first character after the colon, which may be
8931 leading white space. A list of operators is given in section &<<SECTexpop>>&
8932 below. The operator notation is used for simple expansion items that have just
8933 one argument, because it reduces the number of braces and therefore makes the
8934 string easier to understand.
8936 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
8937 This item inserts &"basic"& header lines. It is described with the &%header%&
8938 expansion item below.
8941 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
8942 .cindex "expansion" "calling an acl"
8943 .cindex "&%acl%&" "call from expansion"
8944 The name and zero to nine argument strings are first expanded separately. The expanded
8945 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
8946 Any unused are made empty. The variable &$acl_narg$& is set to the number of
8947 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
8948 and may use the variables; if another acl expansion is used the values
8949 are restored after it returns. If the ACL sets
8950 a value using a "message =" modifier and returns accept or deny, the value becomes
8951 the result of the expansion.
8952 If no message is set and the ACL returns accept or deny
8953 the expansion result is an empty string.
8954 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
8957 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
8958 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
8959 .cindex "expansion" "extracting cerificate fields"
8960 .cindex "&%certextract%&" "certificate fields"
8961 .cindex "certificate" "extracting fields"
8962 The <&'certificate'&> must be a variable of type certificate.
8963 The field name is expanded and used to retrieve the relevant field from
8964 the certificate. Supported fields are:
8968 &`subject `& RFC4514 DN
8969 &`issuer `& RFC4514 DN
8974 &`subj_altname `& tagged list
8978 If the field is found,
8979 <&'string2'&> is expanded, and replaces the whole item;
8980 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
8981 variable &$value$& contains the value that has been extracted. Afterwards, it
8982 is restored to any previous value it might have had.
8984 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
8985 key is not found. If {<&'string2'&>} is also omitted, the value that was
8988 Some field names take optional modifiers, appended and separated by commas.
8990 The field selectors marked as "RFC4514" above
8991 output a Distinguished Name string which is
8993 parseable by Exim as a comma-separated tagged list
8994 (the exceptions being elements containing commas).
8995 RDN elements of a single type may be selected by
8996 a modifier of the type label; if so the expansion
8997 result is a list (newline-separated by default).
8998 The separator may be changed by another modifier of
8999 a right angle-bracket followed immediately by the new separator.
9000 Recognised RDN type labels include "CN", "O", "OU" and "DC".
9002 The field selectors marked as "time" above
9003 take an optional modifier of "int"
9004 for which the result is the number of seconds since epoch.
9005 Otherwise the result is a human-readable string
9006 in the timezone selected by the main "timezone" option.
9008 The field selectors marked as "list" above return a list,
9009 newline-separated by default,
9010 (embedded separator characters in elements are doubled).
9011 The separator may be changed by a modifier of
9012 a right angle-bracket followed immediately by the new separator.
9014 The field selectors marked as "tagged" above
9015 prefix each list element with a type string and an equals sign.
9016 Elements of only one type may be selected by a modifier
9017 which is one of "dns", "uri" or "mail";
9018 if so the element tags are omitted.
9020 If not otherwise noted field values are presented in human-readable form.
9022 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
9023 {*&<&'arg'&>&*}...}*&"
9025 This expansion dynamically loads and then calls a locally-written C function.
9026 This functionality is available only if Exim is compiled with
9030 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
9031 object so that it doesn't reload the same object file in the same Exim process
9032 (but of course Exim does start new processes frequently).
9034 There may be from zero to eight arguments to the function. When compiling
9035 a local function that is to be called in this way, &_local_scan.h_& should be
9036 included. The Exim variables and functions that are defined by that API
9037 are also available for dynamically loaded functions. The function itself
9038 must have the following type:
9040 int dlfunction(uschar **yield, int argc, uschar *argv[])
9042 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
9043 function should return one of the following values:
9045 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
9046 into the expanded string that is being built.
9048 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
9049 from &'yield'&, if it is set.
9051 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
9052 taken from &'yield'& if it is set.
9054 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
9056 When compiling a function that is to be used in this way with gcc,
9057 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
9058 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
9061 .vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
9062 .cindex "expansion" "extracting value from environment"
9063 .cindex "environment" "value from"
9064 The key is first expanded separately, and leading and trailing white space
9066 This is then searched for as a name in the environment.
9067 If a variable is found then its value is placed in &$value$&
9068 and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
9070 Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
9071 appear, for example:
9073 ${env{USER}{$value} fail }
9075 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9076 {<&'string1'&>} must be present for &"fail"& to be recognized.
9078 If {<&'string2'&>} is omitted an empty string is substituted on
9080 If {<&'string1'&>} is omitted the search result is substituted on
9084 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9085 {*&<&'string3'&>&*}}*&"
9086 .cindex "expansion" "extracting substrings by key"
9087 .cindex "&%extract%&" "substrings by key"
9088 The key and <&'string1'&> are first expanded separately. Leading and trailing
9089 white space is removed from the key (but not from any of the strings). The key
9090 must not consist entirely of digits. The expanded <&'string1'&> must be of the
9093 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9096 where the equals signs and spaces (but not both) are optional. If any of the
9097 values contain white space, they must be enclosed in double quotes, and any
9098 values that are enclosed in double quotes are subject to escape processing as
9099 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9100 for the value that corresponds to the key. The search is case-insensitive. If
9101 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9102 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9103 variable &$value$& contains the value that has been extracted. Afterwards, it
9104 is restored to any previous value it might have had.
9106 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9107 key is not found. If {<&'string2'&>} is also omitted, the value that was
9108 extracted is used. Thus, for example, these two expansions are identical, and
9111 ${extract{gid}{uid=1984 gid=2001}}
9112 ${extract{gid}{uid=1984 gid=2001}{$value}}
9114 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9115 appear, for example:
9117 ${extract{Z}{A=... B=...}{$value} fail }
9119 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9120 {<&'string2'&>} must be present for &"fail"& to be recognized.
9123 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
9124 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9125 .cindex "expansion" "extracting substrings by number"
9126 .cindex "&%extract%&" "substrings by number"
9127 The <&'number'&> argument must consist entirely of decimal digits,
9128 apart from leading and trailing white space, which is ignored.
9129 This is what distinguishes this form of &%extract%& from the previous kind. It
9130 behaves in the same way, except that, instead of extracting a named field, it
9131 extracts from <&'string1'&> the field whose number is given as the first
9132 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
9133 <&'string3'&> as before.
9135 The fields in the string are separated by any one of the characters in the
9136 separator string. These may include space or tab characters.
9137 The first field is numbered one. If the number is negative, the fields are
9138 counted from the end of the string, with the rightmost one numbered -1. If the
9139 number given is zero, the entire string is returned. If the modulus of the
9140 number is greater than the number of fields in the string, the result is the
9141 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
9142 provided. For example:
9144 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
9148 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
9150 yields &"99"&. Two successive separators mean that the field between them is
9151 empty (for example, the fifth field above).
9154 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
9155 .cindex "list" "selecting by condition"
9156 .cindex "expansion" "selecting from list by condition"
9158 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9159 default, but the separator can be changed in the usual way. For each item
9160 in this list, its value is place in &$item$&, and then the condition is
9161 evaluated. If the condition is true, &$item$& is added to the output as an
9162 item in a new list; if the condition is false, the item is discarded. The
9163 separator used for the output list is the same as the one used for the
9164 input, but a separator setting is not included in the output. For example:
9166 ${filter{a:b:c}{!eq{$item}{b}}
9168 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
9169 to what it was before. See also the &*map*& and &*reduce*& expansion items.
9172 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9173 .cindex "hash function" "textual"
9174 .cindex "expansion" "textual hash"
9175 This is a textual hashing function, and was the first to be implemented in
9176 early versions of Exim. In current releases, there are other hashing functions
9177 (numeric, MD5, and SHA-1), which are described below.
9179 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
9180 <&'n'&>. If you are using fixed values for these numbers, that is, if
9181 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
9182 use the simpler operator notation that avoids some of the braces:
9184 ${hash_<n>_<m>:<string>}
9186 The second number is optional (in both notations). If <&'n'&> is greater than
9187 or equal to the length of the string, the expansion item returns the string.
9188 Otherwise it computes a new string of length <&'n'&> by applying a hashing
9189 function to the string. The new string consists of characters taken from the
9190 first <&'m'&> characters of the string
9192 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
9194 If <&'m'&> is not present the value 26 is used, so that only lower case
9195 letters appear. For example:
9197 &`$hash{3}{monty}} `& yields &`jmg`&
9198 &`$hash{5}{monty}} `& yields &`monty`&
9199 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
9202 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
9203 &*$h_*&<&'header&~name'&>&*:*&" &&&
9204 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9205 &*$bh_*&<&'header&~name'&>&*:*&" &&&
9206 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9207 &*$rh_*&<&'header&~name'&>&*:*&"
9208 .cindex "expansion" "header insertion"
9209 .vindex "&$header_$&"
9210 .vindex "&$bheader_$&"
9211 .vindex "&$rheader_$&"
9212 .cindex "header lines" "in expansion strings"
9213 .cindex "header lines" "character sets"
9214 .cindex "header lines" "decoding"
9215 Substitute the contents of the named message header line, for example
9219 The newline that terminates a header line is not included in the expansion, but
9220 internal newlines (caused by splitting the header line over several physical
9221 lines) may be present.
9223 The difference between &%rheader%&, &%bheader%&, and &%header%& is in the way
9224 the data in the header line is interpreted.
9227 .cindex "white space" "in header lines"
9228 &%rheader%& gives the original &"raw"& content of the header line, with no
9229 processing at all, and without the removal of leading and trailing white space.
9232 .cindex "base64 encoding" "in header lines"
9233 &%bheader%& removes leading and trailing white space, and then decodes base64
9234 or quoted-printable MIME &"words"& within the header text, but does no
9235 character set translation. If decoding of what looks superficially like a MIME
9236 &"word"& fails, the raw string is returned. If decoding
9237 .cindex "binary zero" "in header line"
9238 produces a binary zero character, it is replaced by a question mark &-- this is
9239 what Exim does for binary zeros that are actually received in header lines.
9242 &%header%& tries to translate the string as decoded by &%bheader%& to a
9243 standard character set. This is an attempt to produce the same string as would
9244 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
9245 returned. Translation is attempted only on operating systems that support the
9246 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
9247 a system Makefile or in &_Local/Makefile_&.
9250 In a filter file, the target character set for &%header%& can be specified by a
9251 command of the following form:
9253 headers charset "UTF-8"
9255 This command affects all references to &$h_$& (or &$header_$&) expansions in
9256 subsequently obeyed filter commands. In the absence of this command, the target
9257 character set in a filter is taken from the setting of the &%headers_charset%&
9258 option in the runtime configuration. The value of this option defaults to the
9259 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
9262 Header names follow the syntax of RFC 2822, which states that they may contain
9263 any printing characters except space and colon. Consequently, curly brackets
9264 &'do not'& terminate header names, and should not be used to enclose them as
9265 if they were variables. Attempting to do so causes a syntax error.
9267 Only header lines that are common to all copies of a message are visible to
9268 this mechanism. These are the original header lines that are received with the
9269 message, and any that are added by an ACL statement or by a system
9270 filter. Header lines that are added to a particular copy of a message by a
9271 router or transport are not accessible.
9273 For incoming SMTP messages, no header lines are visible in ACLs that are obeyed
9274 before the DATA ACL, because the header structure is not set up until the
9275 message is received. Header lines that are added in a RCPT ACL (for example)
9276 are saved until the message's incoming header lines are available, at which
9277 point they are added. When a DATA ACL is running, however, header lines added
9278 by earlier ACLs are visible.
9280 Upper case and lower case letters are synonymous in header names. If the
9281 following character is white space, the terminating colon may be omitted, but
9282 this is not recommended, because you may then forget it when it is needed. When
9283 white space terminates the header name, this white space is included in the
9284 expanded string. If the message does not contain the given header, the
9285 expansion item is replaced by an empty string. (See the &%def%& condition in
9286 section &<<SECTexpcond>>& for a means of testing for the existence of a
9289 If there is more than one header with the same name, they are all concatenated
9290 to form the substitution string, up to a maximum length of 64K. Unless
9291 &%rheader%& is being used, leading and trailing white space is removed from
9292 each header before concatenation, and a completely empty header is ignored. A
9293 newline character is then inserted between non-empty headers, but there is no
9294 newline at the very end. For the &%header%& and &%bheader%& expansion, for
9295 those headers that contain lists of addresses, a comma is also inserted at the
9296 junctions between headers. This does not happen for the &%rheader%& expansion.
9299 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
9300 .cindex "expansion" "hmac hashing"
9302 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
9303 shared secret and some text into a message authentication code, as specified in
9304 RFC 2104. This differs from &`${md5:secret_text...}`& or
9305 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
9306 cryptographic hash, allowing for authentication that is not possible with MD5
9307 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
9308 present. For example:
9310 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
9312 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
9315 dd97e3ba5d1a61b5006108f8c8252953
9317 As an example of how this might be used, you might put in the main part of
9318 an Exim configuration:
9320 SPAMSCAN_SECRET=cohgheeLei2thahw
9322 In a router or a transport you could then have:
9325 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
9326 ${hmac{md5}{SPAMSCAN_SECRET}\
9327 {${primary_hostname},${message_exim_id},$h_message-id:}}
9329 Then given a message, you can check where it was scanned by looking at the
9330 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
9331 this header line is authentic by recomputing the authentication code from the
9332 host name, message ID and the &'Message-id:'& header line. This can be done
9333 using Exim's &%-be%& option, or by other means, for example by using the
9334 &'hmac_md5_hex()'& function in Perl.
9337 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9338 .cindex "expansion" "conditional"
9339 .cindex "&%if%&, expansion item"
9340 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
9341 item; otherwise <&'string2'&> is used. The available conditions are described
9342 in section &<<SECTexpcond>>& below. For example:
9344 ${if eq {$local_part}{postmaster} {yes}{no} }
9346 The second string need not be present; if it is not and the condition is not
9347 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
9348 be present instead of the second string (without any curly brackets). In this
9349 case, the expansion is forced to fail if the condition is not true (see section
9350 &<<SECTforexpfai>>&).
9352 If both strings are omitted, the result is the string &`true`& if the condition
9353 is true, and the empty string if the condition is false. This makes it less
9354 cumbersome to write custom ACL and router conditions. For example, instead of
9356 condition = ${if >{$acl_m4}{3}{true}{false}}
9360 condition = ${if >{$acl_m4}{3}}
9363 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9364 .cindex "expansion" "string truncation"
9365 .cindex "&%length%& expansion item"
9366 The &%length%& item is used to extract the initial portion of a string. Both
9367 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
9368 you are using a fixed value for the number, that is, if <&'string1'&> does not
9369 change when expanded, you can use the simpler operator notation that avoids
9372 ${length_<n>:<string>}
9374 The result of this item is either the first <&'n'&> characters or the whole
9375 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
9376 &%strlen%&, which gives the length of a string.
9379 .vitem "&*${listextract{*&<&'number'&>&*}&&&
9380 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9381 .cindex "expansion" "extracting list elements by number"
9382 .cindex "&%listextract%&" "extract list elements by number"
9383 .cindex "list" "extracting elements by number"
9384 The <&'number'&> argument must consist entirely of decimal digits,
9385 apart from an optional leading minus,
9386 and leading and trailing white space (which is ignored).
9388 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9389 default, but the separator can be changed in the usual way.
9391 The first field of the list is numbered one.
9392 If the number is negative, the fields are
9393 counted from the end of the list, with the rightmost one numbered -1.
9394 The numbered element of the list is extracted and placed in &$value$&,
9395 then <&'string2'&> is expanded as the result.
9397 If the modulus of the
9398 number is zero or greater than the number of fields in the string,
9399 the result is the expansion of <&'string3'&>.
9403 ${listextract{2}{x:42:99}}
9407 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
9409 yields &"result: 42"&.
9411 If {<&'string3'&>} is omitted, an empty string is used for string3.
9412 If {<&'string2'&>} is also omitted, the value that was
9414 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
9417 .vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
9418 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9419 This is the first of one of two different types of lookup item, which are both
9420 described in the next item.
9422 .vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
9423 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9424 .cindex "expansion" "lookup in"
9425 .cindex "file" "lookups"
9426 .cindex "lookup" "in expanded string"
9427 The two forms of lookup item specify data lookups in files and databases, as
9428 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
9429 lookups, and the second is used for query-style lookups. The <&'key'&>,
9430 <&'file'&>, and <&'query'&> strings are expanded before use.
9432 If there is any white space in a lookup item which is part of a filter command,
9433 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
9434 other place where white space is significant, the lookup item must be enclosed
9435 in double quotes. The use of data lookups in users' filter files may be locked
9436 out by the system administrator.
9439 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
9440 During its expansion, the variable &$value$& contains the data returned by the
9441 lookup. Afterwards it reverts to the value it had previously (at the outer
9442 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
9443 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
9444 string on failure. If <&'string2'&> is provided, it can itself be a nested
9445 lookup, thus providing a mechanism for looking up a default value when the
9446 original lookup fails.
9448 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
9449 data for the outer lookup while the parameters of the second lookup are
9450 expanded, and also while <&'string2'&> of the second lookup is expanded, should
9451 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
9452 appear, and in this case, if the lookup fails, the entire expansion is forced
9453 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
9454 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
9455 successful lookup, and nothing in the case of failure.
9457 For single-key lookups, the string &"partial"& is permitted to precede the
9458 search type in order to do partial matching, and * or *@ may follow a search
9459 type to request default lookups if the key does not match (see sections
9460 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
9462 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
9463 If a partial search is used, the variables &$1$& and &$2$& contain the wild
9464 and non-wild parts of the key during the expansion of the replacement text.
9465 They return to their previous values at the end of the lookup item.
9467 This example looks up the postmaster alias in the conventional alias file:
9469 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
9471 This example uses NIS+ to look up the full name of the user corresponding to
9472 the local part of an address, forcing the expansion to fail if it is not found:
9474 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
9479 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9480 .cindex "expansion" "list creation"
9482 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9483 default, but the separator can be changed in the usual way. For each item
9484 in this list, its value is place in &$item$&, and then <&'string2'&> is
9485 expanded and added to the output as an item in a new list. The separator used
9486 for the output list is the same as the one used for the input, but a separator
9487 setting is not included in the output. For example:
9489 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
9491 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
9492 value of &$item$& is restored to what it was before. See also the &*filter*&
9493 and &*reduce*& expansion items.
9495 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9496 .cindex "expansion" "numeric hash"
9497 .cindex "hash function" "numeric"
9498 The three strings are expanded; the first two must yield numbers. Call them
9499 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9500 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9501 can use the simpler operator notation that avoids some of the braces:
9503 ${nhash_<n>_<m>:<string>}
9505 The second number is optional (in both notations). If there is only one number,
9506 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
9507 processed by a div/mod hash function that returns two numbers, separated by a
9508 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
9511 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
9513 returns the string &"6/33"&.
9517 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
9518 .cindex "Perl" "use in expanded string"
9519 .cindex "expansion" "calling Perl from"
9520 This item is available only if Exim has been built to include an embedded Perl
9521 interpreter. The subroutine name and the arguments are first separately
9522 expanded, and then the Perl subroutine is called with those arguments. No
9523 additional arguments need be given; the maximum number permitted, including the
9524 name of the subroutine, is nine.
9526 The return value of the subroutine is inserted into the expanded string, unless
9527 the return value is &%undef%&. In that case, the expansion fails in the same
9528 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
9529 Whatever you return is evaluated in a scalar context. For example, if you
9530 return the name of a Perl vector, the return value is the size of the vector,
9533 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
9534 with the error message that was passed to &%die%&. More details of the embedded
9535 Perl facility are given in chapter &<<CHAPperl>>&.
9537 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
9538 out the use of this expansion item in filter files.
9541 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
9542 .cindex "&%prvs%& expansion item"
9543 The first argument is a complete email address and the second is secret
9544 keystring. The third argument, specifying a key number, is optional. If absent,
9545 it defaults to 0. The result of the expansion is a prvs-signed email address,
9546 to be typically used with the &%return_path%& option on an &(smtp)& transport
9547 as part of a bounce address tag validation (BATV) scheme. For more discussion
9548 and an example, see section &<<SECTverifyPRVS>>&.
9550 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
9551 {*&<&'string'&>&*}}*&"
9552 .cindex "&%prvscheck%& expansion item"
9553 This expansion item is the complement of the &%prvs%& item. It is used for
9554 checking prvs-signed addresses. If the expansion of the first argument does not
9555 yield a syntactically valid prvs-signed address, the whole item expands to the
9556 empty string. When the first argument does expand to a syntactically valid
9557 prvs-signed address, the second argument is expanded, with the prvs-decoded
9558 version of the address and the key number extracted from the address in the
9559 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
9561 These two variables can be used in the expansion of the second argument to
9562 retrieve the secret. The validity of the prvs-signed address is then checked
9563 against the secret. The result is stored in the variable &$prvscheck_result$&,
9564 which is empty for failure or &"1"& for success.
9566 The third argument is optional; if it is missing, it defaults to an empty
9567 string. This argument is now expanded. If the result is an empty string, the
9568 result of the expansion is the decoded version of the address. This is the case
9569 whether or not the signature was valid. Otherwise, the result of the expansion
9570 is the expansion of the third argument.
9572 All three variables can be used in the expansion of the third argument.
9573 However, once the expansion is complete, only &$prvscheck_result$& remains set.
9574 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
9576 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
9577 .cindex "expansion" "inserting an entire file"
9578 .cindex "file" "inserting into expansion"
9579 .cindex "&%readfile%& expansion item"
9580 The file name and end-of-line string are first expanded separately. The file is
9581 then read, and its contents replace the entire item. All newline characters in
9582 the file are replaced by the end-of-line string if it is present. Otherwise,
9583 newlines are left in the string.
9584 String expansion is not applied to the contents of the file. If you want this,
9585 you must wrap the item in an &%expand%& operator. If the file cannot be read,
9586 the string expansion fails.
9588 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
9589 locks out the use of this expansion item in filter files.
9593 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
9594 {*&<&'timeout'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
9595 .cindex "expansion" "inserting from a socket"
9596 .cindex "socket, use of in expansion"
9597 .cindex "&%readsocket%& expansion item"
9598 This item inserts data from a Unix domain or TCP socket into the expanded
9599 string. The minimal way of using it uses just two arguments, as in these
9602 ${readsocket{/socket/name}{request string}}
9603 ${readsocket{inet:some.host:1234}{request string}}
9605 For a Unix domain socket, the first substring must be the path to the socket.
9606 For an Internet socket, the first substring must contain &`inet:`& followed by
9607 a host name or IP address, followed by a colon and a port, which can be a
9608 number or the name of a TCP port in &_/etc/services_&. An IP address may
9609 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
9612 ${readsocket{inet:[::1]:1234}{request string}}
9614 Only a single host name may be given, but if looking it up yields more than
9615 one IP address, they are each tried in turn until a connection is made. For
9616 both kinds of socket, Exim makes a connection, writes the request string
9617 (unless it is an empty string) and reads from the socket until an end-of-file
9618 is read. A timeout of 5 seconds is applied. Additional, optional arguments
9619 extend what can be done. Firstly, you can vary the timeout. For example:
9621 ${readsocket{/socket/name}{request string}{3s}}
9623 A fourth argument allows you to change any newlines that are in the data
9624 that is read, in the same way as for &%readfile%& (see above). This example
9625 turns them into spaces:
9627 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
9629 As with all expansions, the substrings are expanded before the processing
9630 happens. Errors in these sub-expansions cause the expansion to fail. In
9631 addition, the following errors can occur:
9634 Failure to create a socket file descriptor;
9636 Failure to connect the socket;
9638 Failure to write the request string;
9640 Timeout on reading from the socket.
9643 By default, any of these errors causes the expansion to fail. However, if
9644 you supply a fifth substring, it is expanded and used when any of the above
9645 errors occurs. For example:
9647 ${readsocket{/socket/name}{request string}{3s}{\n}\
9650 You can test for the existence of a Unix domain socket by wrapping this
9651 expansion in &`${if exists`&, but there is a race condition between that test
9652 and the actual opening of the socket, so it is safer to use the fifth argument
9653 if you want to be absolutely sure of avoiding an expansion error for a
9654 non-existent Unix domain socket, or a failure to connect to an Internet socket.
9656 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
9657 locks out the use of this expansion item in filter files.
9660 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9661 .cindex "expansion" "reducing a list to a scalar"
9662 .cindex "list" "reducing to a scalar"
9665 This operation reduces a list to a single, scalar string. After expansion,
9666 <&'string1'&> is interpreted as a list, colon-separated by default, but the
9667 separator can be changed in the usual way. Then <&'string2'&> is expanded and
9668 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
9669 list is assigned to &$item$& in turn, and <&'string3'&> is expanded for each of
9670 them. The result of that expansion is assigned to &$value$& before the next
9671 iteration. When the end of the list is reached, the final value of &$value$& is
9672 added to the expansion output. The &*reduce*& expansion item can be used in a
9673 number of ways. For example, to add up a list of numbers:
9675 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
9677 The result of that expansion would be &`6`&. The maximum of a list of numbers
9680 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
9682 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
9683 restored to what they were before. See also the &*filter*& and &*map*&
9686 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
9687 This item inserts &"raw"& header lines. It is described with the &%header%&
9688 expansion item above.
9690 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
9691 {*&<&'string2'&>&*}}*&"
9692 .cindex "expansion" "running a command"
9693 .cindex "&%run%& expansion item"
9694 The command and its arguments are first expanded as one string. The string is
9695 split apart into individual arguments by spaces, and then the command is run
9696 in a separate process, but under the same uid and gid. As in other command
9697 executions from Exim, a shell is not used by default. If the command requires
9698 a shell, you must explicitly code it.
9700 Since the arguments are split by spaces, when there is a variable expansion
9701 which has an empty result, it will cause the situation that the argument will
9702 simply be omitted when the program is actually executed by Exim. If the
9703 script/program requires a specific number of arguments and the expanded
9704 variable could possibly result in this empty expansion, the variable must be
9705 quoted. This is more difficult if the expanded variable itself could result
9706 in a string containing quotes, because it would interfere with the quotes
9707 around the command arguments. A possible guard against this is to wrap the
9708 variable in the &%sg%& operator to change any quote marks to some other
9711 The standard input for the command exists, but is empty. The standard output
9712 and standard error are set to the same file descriptor.
9713 .cindex "return code" "from &%run%& expansion"
9715 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
9716 and replaces the entire item; during this expansion, the standard output/error
9717 from the command is in the variable &$value$&. If the command fails,
9718 <&'string2'&>, if present, is expanded and used. Once again, during the
9719 expansion, the standard output/error from the command is in the variable
9722 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
9723 can be the word &"fail"& (not in braces) to force expansion failure if the
9724 command does not succeed. If both strings are omitted, the result is contents
9725 of the standard output/error on success, and nothing on failure.
9727 .vindex "&$run_in_acl$&"
9728 The standard output/error of the command is put in the variable &$value$&.
9729 In this ACL example, the output of a command is logged for the admin to
9732 warn condition = ${run{/usr/bin/id}{yes}{no}}
9733 log_message = Output of id: $value
9735 If the command requires shell idioms, such as the > redirect operator, the
9736 shell must be invoked directly, such as with:
9738 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
9742 The return code from the command is put in the variable &$runrc$&, and this
9743 remains set afterwards, so in a filter file you can do things like this:
9745 if "${run{x y z}{}}$runrc" is 1 then ...
9746 elif $runrc is 2 then ...
9750 If execution of the command fails (for example, the command does not exist),
9751 the return code is 127 &-- the same code that shells use for non-existent
9754 &*Warning*&: In a router or transport, you cannot assume the order in which
9755 option values are expanded, except for those preconditions whose order of
9756 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
9757 by the expansion of one option, and use it in another.
9759 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
9760 out the use of this expansion item in filter files.
9763 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
9764 .cindex "expansion" "string substitution"
9765 .cindex "&%sg%& expansion item"
9766 This item works like Perl's substitution operator (s) with the global (/g)
9767 option; hence its name. However, unlike the Perl equivalent, Exim does not
9768 modify the subject string; instead it returns the modified string for insertion
9769 into the overall expansion. The item takes three arguments: the subject string,
9770 a regular expression, and a substitution string. For example:
9772 ${sg{abcdefabcdef}{abc}{xyz}}
9774 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
9775 if any $ or \ characters are required in the regular expression or in the
9776 substitution string, they have to be escaped. For example:
9778 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
9780 yields &"defabc"&, and
9782 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
9784 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
9785 the regular expression from string expansion.
9789 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
9790 .cindex sorting "a list"
9791 .cindex list sorting
9792 .cindex expansion "list sorting"
9793 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9794 default, but the separator can be changed in the usual way.
9795 The <&'comparator'&> argument is interpreted as the operator
9796 of a two-argument expansion condition.
9797 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
9798 The comparison should return true when applied to two values
9799 if the first value should sort before the second value.
9800 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
9801 the element being placed in &$item$&,
9802 to give values for comparison.
9804 The item result is a sorted list,
9805 with the original list separator,
9806 of the list elements (in full) of the original.
9810 ${sort{3:2:1:4}{<}{$item}}
9812 sorts a list of numbers, and
9814 ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
9816 will sort an MX lookup into priority order.
9819 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9820 .cindex "&%substr%& expansion item"
9821 .cindex "substring extraction"
9822 .cindex "expansion" "substring extraction"
9823 The three strings are expanded; the first two must yield numbers. Call them
9824 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9825 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9826 can use the simpler operator notation that avoids some of the braces:
9828 ${substr_<n>_<m>:<string>}
9830 The second number is optional (in both notations).
9831 If it is absent in the simpler format, the preceding underscore must also be
9834 The &%substr%& item can be used to extract more general substrings than
9835 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
9836 length required. For example
9838 ${substr{3}{2}{$local_part}}
9840 If the starting offset is greater than the string length the result is the
9841 null string; if the length plus starting offset is greater than the string
9842 length, the result is the right-hand part of the string, starting from the
9843 given offset. The first character in the string has offset zero.
9845 The &%substr%& expansion item can take negative offset values to count
9846 from the right-hand end of its operand. The last character is offset -1, the
9847 second-last is offset -2, and so on. Thus, for example,
9849 ${substr{-5}{2}{1234567}}
9851 yields &"34"&. If the absolute value of a negative offset is greater than the
9852 length of the string, the substring starts at the beginning of the string, and
9853 the length is reduced by the amount of overshoot. Thus, for example,
9855 ${substr{-5}{2}{12}}
9857 yields an empty string, but
9859 ${substr{-3}{2}{12}}
9863 When the second number is omitted from &%substr%&, the remainder of the string
9864 is taken if the offset is positive. If it is negative, all characters in the
9865 string preceding the offset point are taken. For example, an offset of -1 and
9866 no length, as in these semantically identical examples:
9869 ${substr{-1}{abcde}}
9871 yields all but the last character of the string, that is, &"abcd"&.
9875 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
9876 {*&<&'replacements'&>&*}}*&"
9877 .cindex "expansion" "character translation"
9878 .cindex "&%tr%& expansion item"
9879 This item does single-character translation on its subject string. The second
9880 argument is a list of characters to be translated in the subject string. Each
9881 matching character is replaced by the corresponding character from the
9882 replacement list. For example
9884 ${tr{abcdea}{ac}{13}}
9886 yields &`1b3de1`&. If there are duplicates in the second character string, the
9887 last occurrence is used. If the third string is shorter than the second, its
9888 last character is replicated. However, if it is empty, no translation takes
9894 .section "Expansion operators" "SECTexpop"
9895 .cindex "expansion" "operators"
9896 For expansion items that perform transformations on a single argument string,
9897 the &"operator"& notation is used because it is simpler and uses fewer braces.
9898 The substring is first expanded before the operation is applied to it. The
9899 following operations can be performed:
9902 .vitem &*${address:*&<&'string'&>&*}*&
9903 .cindex "expansion" "RFC 2822 address handling"
9904 .cindex "&%address%& expansion item"
9905 The string is interpreted as an RFC 2822 address, as it might appear in a
9906 header line, and the effective address is extracted from it. If the string does
9907 not parse successfully, the result is empty.
9910 .vitem &*${addresses:*&<&'string'&>&*}*&
9911 .cindex "expansion" "RFC 2822 address handling"
9912 .cindex "&%addresses%& expansion item"
9913 The string (after expansion) is interpreted as a list of addresses in RFC
9914 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
9915 operative address (&'local-part@domain'&) is extracted from each item, and the
9916 result of the expansion is a colon-separated list, with appropriate
9917 doubling of colons should any happen to be present in the email addresses.
9918 Syntactically invalid RFC2822 address items are omitted from the output.
9920 It is possible to specify a character other than colon for the output
9921 separator by starting the string with > followed by the new separator
9922 character. For example:
9924 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
9926 expands to &`ceo@up.stairs&&sec@base.ment`&. Compare the &*address*& (singular)
9927 expansion item, which extracts the working address from a single RFC2822
9928 address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
9931 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
9932 a strict interpretation of header line formatting. Exim parses the bare,
9933 unquoted portion of an email address and if it finds a comma, treats it as an
9934 email address separator. For the example header line:
9936 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
9938 The first example below demonstrates that Q-encoded email addresses are parsed
9939 properly if it is given the raw header (in this example, &`$rheader_from:`&).
9940 It does not see the comma because it's still encoded as "=2C". The second
9941 example below is passed the contents of &`$header_from:`&, meaning it gets
9942 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
9943 The third example shows that the presence of a comma is skipped when it is
9946 # exim -be '${addresses:From: \
9947 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
9949 # exim -be '${addresses:From: Last, First <user@example.com>}'
9950 Last:user@example.com
9951 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
9955 .vitem &*${base62:*&<&'digits'&>&*}*&
9956 .cindex "&%base62%& expansion item"
9957 .cindex "expansion" "conversion to base 62"
9958 The string must consist entirely of decimal digits. The number is converted to
9959 base 62 and output as a string of six characters, including leading zeros. In
9960 the few operating environments where Exim uses base 36 instead of base 62 for
9961 its message identifiers (because those systems do not have case-sensitive file
9962 names), base 36 is used by this operator, despite its name. &*Note*&: Just to
9963 be absolutely clear: this is &'not'& base64 encoding.
9965 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
9966 .cindex "&%base62d%& expansion item"
9967 .cindex "expansion" "conversion to base 62"
9968 The string must consist entirely of base-62 digits, or, in operating
9969 environments where Exim uses base 36 instead of base 62 for its message
9970 identifiers, base-36 digits. The number is converted to decimal and output as a
9974 .vitem &*${domain:*&<&'string'&>&*}*&
9975 .cindex "domain" "extraction"
9976 .cindex "expansion" "domain extraction"
9977 The string is interpreted as an RFC 2822 address and the domain is extracted
9978 from it. If the string does not parse successfully, the result is empty.
9981 .vitem &*${escape:*&<&'string'&>&*}*&
9982 .cindex "expansion" "escaping non-printing characters"
9983 .cindex "&%escape%& expansion item"
9984 If the string contains any non-printing characters, they are converted to
9985 escape sequences starting with a backslash. Whether characters with the most
9986 significant bit set (so-called &"8-bit characters"&) count as printing or not
9987 is controlled by the &%print_topbitchars%& option.
9990 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
9991 .cindex "expansion" "expression evaluation"
9992 .cindex "expansion" "arithmetic expression"
9993 .cindex "&%eval%& expansion item"
9994 These items supports simple arithmetic and bitwise logical operations in
9995 expansion strings. The string (after expansion) must be a conventional
9996 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
9997 logical operators, and parentheses. All operations are carried out using
9998 integer arithmetic. The operator priorities are as follows (the same as in the
9999 C programming language):
10001 .irow &'highest:'& "not (~), negate (-)"
10002 .irow "" "multiply (*), divide (/), remainder (%)"
10003 .irow "" "plus (+), minus (-)"
10004 .irow "" "shift-left (<<), shift-right (>>)"
10005 .irow "" "and (&&)"
10007 .irow &'lowest:'& "or (|)"
10009 Binary operators with the same priority are evaluated from left to right. White
10010 space is permitted before or after operators.
10012 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
10013 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
10014 decimal, even if they start with a leading zero; hexadecimal numbers are not
10015 permitted. This can be useful when processing numbers extracted from dates or
10016 times, which often do have leading zeros.
10018 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
10020 respectively. Negative numbers are supported. The result of the computation is
10021 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
10024 &`${eval:1+1} `& yields 2
10025 &`${eval:1+2*3} `& yields 7
10026 &`${eval:(1+2)*3} `& yields 9
10027 &`${eval:2+42%5} `& yields 4
10028 &`${eval:0xc&5} `& yields 4
10029 &`${eval:0xc|5} `& yields 13
10030 &`${eval:0xc^5} `& yields 9
10031 &`${eval:0xc>>1} `& yields 6
10032 &`${eval:0xc<<1} `& yields 24
10033 &`${eval:~255&0x1234} `& yields 4608
10034 &`${eval:-(~255&0x1234)} `& yields -4608
10037 As a more realistic example, in an ACL you might have
10039 deny message = Too many bad recipients
10042 {>{$rcpt_count}{10}} \
10045 {$recipients_count} \
10046 {${eval:$rcpt_count/2}} \
10050 The condition is true if there have been more than 10 RCPT commands and
10051 fewer than half of them have resulted in a valid recipient.
10054 .vitem &*${expand:*&<&'string'&>&*}*&
10055 .cindex "expansion" "re-expansion of substring"
10056 The &%expand%& operator causes a string to be expanded for a second time. For
10059 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
10061 first looks up a string in a file while expanding the operand for &%expand%&,
10062 and then re-expands what it has found.
10065 .vitem &*${from_utf8:*&<&'string'&>&*}*&
10067 .cindex "UTF-8" "conversion from"
10068 .cindex "expansion" "UTF-8 conversion"
10069 .cindex "&%from_utf8%& expansion item"
10070 The world is slowly moving towards Unicode, although there are no standards for
10071 email yet. However, other applications (including some databases) are starting
10072 to store data in Unicode, using UTF-8 encoding. This operator converts from a
10073 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
10074 converted to underscores. The input must be a valid UTF-8 string. If it is not,
10075 the result is an undefined sequence of bytes.
10077 Unicode code points with values less than 256 are compatible with ASCII and
10078 ISO-8859-1 (also known as Latin-1).
10079 For example, character 169 is the copyright symbol in both cases, though the
10080 way it is encoded is different. In UTF-8, more than one byte is needed for
10081 characters with code values greater than 127, whereas ISO-8859-1 is a
10082 single-byte encoding (but thereby limited to 256 characters). This makes
10083 translation from UTF-8 to ISO-8859-1 straightforward.
10086 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10087 .cindex "hash function" "textual"
10088 .cindex "expansion" "textual hash"
10089 The &%hash%& operator is a simpler interface to the hashing function that can
10090 be used when the two parameters are fixed numbers (as opposed to strings that
10091 change when expanded). The effect is the same as
10093 ${hash{<n>}{<m>}{<string>}}
10095 See the description of the general &%hash%& item above for details. The
10096 abbreviation &%h%& can be used when &%hash%& is used as an operator.
10100 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
10101 .cindex "base64 encoding" "conversion from hex"
10102 .cindex "expansion" "hex to base64"
10103 .cindex "&%hex2b64%& expansion item"
10104 This operator converts a hex string into one that is base64 encoded. This can
10105 be useful for processing the output of the MD5 and SHA-1 hashing functions.
10109 .vitem &*${hexquote:*&<&'string'&>&*}*&
10110 .cindex "quoting" "hex-encoded unprintable characters"
10111 .cindex "&%hexquote%& expansion item"
10112 This operator converts non-printable characters in a string into a hex
10113 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
10114 as is, and other byte values are converted to &`\xNN`&, for example a
10115 byte value 127 is converted to &`\x7f`&.
10119 .vitem &*${ipv6denorm:*&<&'string'&>&*}*&
10120 .cindex "&%ipv6denorm%& expansion item"
10121 .cindex "IP address" normalisation
10122 This expands an IPv6 address to a full eight-element colon-separated set
10123 of hex digits including leading zeroes.
10124 A trailing ipv4-style dotted-decimal set is converted to hex.
10125 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
10127 .vitem &*${ipv6norm:*&<&'string'&>&*}*&
10128 .cindex "&%ipv6norm%& expansion item"
10129 .cindex "IP address" normalisation
10130 .cindex "IP address" "canonical form"
10131 This converts an IPv6 address to canonical form.
10132 Leading zeroes of groups are omitted, and the longest
10133 set of zero-valued groups is replaced with a double colon.
10134 A trailing ipv4-style dotted-decimal set is converted to hex.
10135 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
10139 .vitem &*${lc:*&<&'string'&>&*}*&
10140 .cindex "case forcing in strings"
10141 .cindex "string" "case forcing"
10142 .cindex "lower casing"
10143 .cindex "expansion" "case forcing"
10144 .cindex "&%lc%& expansion item"
10145 This forces the letters in the string into lower-case, for example:
10150 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
10151 .cindex "expansion" "string truncation"
10152 .cindex "&%length%& expansion item"
10153 The &%length%& operator is a simpler interface to the &%length%& function that
10154 can be used when the parameter is a fixed number (as opposed to a string that
10155 changes when expanded). The effect is the same as
10157 ${length{<number>}{<string>}}
10159 See the description of the general &%length%& item above for details. Note that
10160 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
10161 when &%length%& is used as an operator.
10164 .vitem &*${listcount:*&<&'string'&>&*}*&
10165 .cindex "expansion" "list item count"
10166 .cindex "list" "item count"
10167 .cindex "list" "count of items"
10168 .cindex "&%listcount%& expansion item"
10169 The string is interpreted as a list and the number of items is returned.
10172 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
10173 .cindex "expansion" "named list"
10174 .cindex "&%listnamed%& expansion item"
10175 The name is interpreted as a named list and the content of the list is returned,
10176 expanding any referenced lists, re-quoting as needed for colon-separation.
10177 If the optional type is given it must be one of "a", "d", "h" or "l"
10178 and selects address-, domain-, host- or localpart- lists to search among respectively.
10179 Otherwise all types are searched in an undefined order and the first
10180 matching list is returned.
10183 .vitem &*${local_part:*&<&'string'&>&*}*&
10184 .cindex "expansion" "local part extraction"
10185 .cindex "&%local_part%& expansion item"
10186 The string is interpreted as an RFC 2822 address and the local part is
10187 extracted from it. If the string does not parse successfully, the result is
10191 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
10192 .cindex "masked IP address"
10193 .cindex "IP address" "masking"
10194 .cindex "CIDR notation"
10195 .cindex "expansion" "IP address masking"
10196 .cindex "&%mask%& expansion item"
10197 If the form of the string to be operated on is not an IP address followed by a
10198 slash and an integer (that is, a network address in CIDR notation), the
10199 expansion fails. Otherwise, this operator converts the IP address to binary,
10200 masks off the least significant bits according to the bit count, and converts
10201 the result back to text, with mask appended. For example,
10203 ${mask:10.111.131.206/28}
10205 returns the string &"10.111.131.192/28"&. Since this operation is expected to
10206 be mostly used for looking up masked addresses in files, the result for an IPv6
10207 address uses dots to separate components instead of colons, because colon
10208 terminates a key string in lsearch files. So, for example,
10210 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
10214 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
10216 Letters in IPv6 addresses are always output in lower case.
10219 .vitem &*${md5:*&<&'string'&>&*}*&
10221 .cindex "expansion" "MD5 hash"
10222 .cindex "certificate fingerprint"
10223 .cindex "&%md5%& expansion item"
10224 The &%md5%& operator computes the MD5 hash value of the string, and returns it
10225 as a 32-digit hexadecimal number, in which any letters are in lower case.
10228 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10229 .cindex "expansion" "numeric hash"
10230 .cindex "hash function" "numeric"
10231 The &%nhash%& operator is a simpler interface to the numeric hashing function
10232 that can be used when the two parameters are fixed numbers (as opposed to
10233 strings that change when expanded). The effect is the same as
10235 ${nhash{<n>}{<m>}{<string>}}
10237 See the description of the general &%nhash%& item above for details.
10240 .vitem &*${quote:*&<&'string'&>&*}*&
10241 .cindex "quoting" "in string expansions"
10242 .cindex "expansion" "quoting"
10243 .cindex "&%quote%& expansion item"
10244 The &%quote%& operator puts its argument into double quotes if it
10245 is an empty string or
10246 contains anything other than letters, digits, underscores, dots, and hyphens.
10247 Any occurrences of double quotes and backslashes are escaped with a backslash.
10248 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
10249 respectively For example,
10257 The place where this is useful is when the argument is a substitution from a
10258 variable or a message header.
10260 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
10261 .cindex "&%quote_local_part%& expansion item"
10262 This operator is like &%quote%&, except that it quotes the string only if
10263 required to do so by the rules of RFC 2822 for quoting local parts. For
10264 example, a plus sign would not cause quoting (but it would for &%quote%&).
10265 If you are creating a new email address from the contents of &$local_part$&
10266 (or any other unknown data), you should always use this operator.
10269 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
10270 .cindex "quoting" "lookup-specific"
10271 This operator applies lookup-specific quoting rules to the string. Each
10272 query-style lookup type has its own quoting rules which are described with
10273 the lookups in chapter &<<CHAPfdlookup>>&. For example,
10275 ${quote_ldap:two * two}
10281 For single-key lookup types, no quoting is ever necessary and this operator
10282 yields an unchanged string.
10285 .vitem &*${randint:*&<&'n'&>&*}*&
10286 .cindex "random number"
10287 This operator returns a somewhat random number which is less than the
10288 supplied number and is at least 0. The quality of this randomness depends
10289 on how Exim was built; the values are not suitable for keying material.
10290 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
10291 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
10292 for versions of GnuTLS with that function.
10293 Otherwise, the implementation may be arc4random(), random() seeded by
10294 srandomdev() or srandom(), or a custom implementation even weaker than
10298 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
10299 .cindex "expansion" "IP address"
10300 This operator reverses an IP address; for IPv4 addresses, the result is in
10301 dotted-quad decimal form, while for IPv6 addresses the result is in
10302 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
10303 for DNS. For example,
10305 ${reverse_ip:192.0.2.4}
10306 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
10311 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
10315 .vitem &*${rfc2047:*&<&'string'&>&*}*&
10316 .cindex "expansion" "RFC 2047"
10317 .cindex "RFC 2047" "expansion operator"
10318 .cindex "&%rfc2047%& expansion item"
10319 This operator encodes text according to the rules of RFC 2047. This is an
10320 encoding that is used in header lines to encode non-ASCII characters. It is
10321 assumed that the input string is in the encoding specified by the
10322 &%headers_charset%& option, which defaults to ISO-8859-1. If the string
10323 contains only characters in the range 33&--126, and no instances of the
10326 ? = ( ) < > @ , ; : \ " . [ ] _
10328 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
10329 string, using as many &"encoded words"& as necessary to encode all the
10333 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
10334 .cindex "expansion" "RFC 2047"
10335 .cindex "RFC 2047" "decoding"
10336 .cindex "&%rfc2047d%& expansion item"
10337 This operator decodes strings that are encoded as per RFC 2047. Binary zero
10338 bytes are replaced by question marks. Characters are converted into the
10339 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
10340 not recognized unless &%check_rfc2047_length%& is set false.
10342 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
10343 access a header line, RFC 2047 decoding is done automatically. You do not need
10344 to use this operator as well.
10348 .vitem &*${rxquote:*&<&'string'&>&*}*&
10349 .cindex "quoting" "in regular expressions"
10350 .cindex "regular expressions" "quoting"
10351 .cindex "&%rxquote%& expansion item"
10352 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
10353 characters in its argument. This is useful when substituting the values of
10354 variables or headers inside regular expressions.
10357 .vitem &*${sha1:*&<&'string'&>&*}*&
10358 .cindex "SHA-1 hash"
10359 .cindex "expansion" "SHA-1 hashing"
10360 .cindex "certificate fingerprint"
10361 .cindex "&%sha2%& expansion item"
10362 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
10363 it as a 40-digit hexadecimal number, in which any letters are in upper case.
10366 .vitem &*${sha256:*&<&'certificate'&>&*}*&
10367 .cindex "SHA-256 hash"
10368 .cindex "certificate fingerprint"
10369 .cindex "expansion" "SHA-256 hashing"
10370 .cindex "&%sha256%& expansion item"
10371 The &%sha256%& operator computes the SHA-256 hash fingerprint of the
10374 it as a 64-digit hexadecimal number, in which any letters are in upper case.
10375 Only arguments which are a single variable of certificate type are supported.
10378 .vitem &*${stat:*&<&'string'&>&*}*&
10379 .cindex "expansion" "statting a file"
10380 .cindex "file" "extracting characteristics"
10381 .cindex "&%stat%& expansion item"
10382 The string, after expansion, must be a file path. A call to the &[stat()]&
10383 function is made for this path. If &[stat()]& fails, an error occurs and the
10384 expansion fails. If it succeeds, the data from the stat replaces the item, as a
10385 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
10386 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
10387 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
10388 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
10389 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
10390 can extract individual fields using the &%extract%& expansion item.
10392 The use of the &%stat%& expansion in users' filter files can be locked out by
10393 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
10394 systems for files larger than 2GB.
10396 .vitem &*${str2b64:*&<&'string'&>&*}*&
10397 .cindex "expansion" "base64 encoding"
10398 .cindex "base64 encoding" "in string expansion"
10399 .cindex "&%str2b64%& expansion item"
10400 This operator converts a string into one that is base64 encoded.
10404 .vitem &*${strlen:*&<&'string'&>&*}*&
10405 .cindex "expansion" "string length"
10406 .cindex "string" "length in expansion"
10407 .cindex "&%strlen%& expansion item"
10408 The item is replace by the length of the expanded string, expressed as a
10409 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
10412 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
10413 .cindex "&%substr%& expansion item"
10414 .cindex "substring extraction"
10415 .cindex "expansion" "substring expansion"
10416 The &%substr%& operator is a simpler interface to the &%substr%& function that
10417 can be used when the two parameters are fixed numbers (as opposed to strings
10418 that change when expanded). The effect is the same as
10420 ${substr{<start>}{<length>}{<string>}}
10422 See the description of the general &%substr%& item above for details. The
10423 abbreviation &%s%& can be used when &%substr%& is used as an operator.
10425 .vitem &*${time_eval:*&<&'string'&>&*}*&
10426 .cindex "&%time_eval%& expansion item"
10427 .cindex "time interval" "decoding"
10428 This item converts an Exim time interval such as &`2d4h5m`& into a number of
10431 .vitem &*${time_interval:*&<&'string'&>&*}*&
10432 .cindex "&%time_interval%& expansion item"
10433 .cindex "time interval" "formatting"
10434 The argument (after sub-expansion) must be a sequence of decimal digits that
10435 represents an interval of time as a number of seconds. It is converted into a
10436 number of larger units and output in Exim's normal time format, for example,
10439 .vitem &*${uc:*&<&'string'&>&*}*&
10440 .cindex "case forcing in strings"
10441 .cindex "string" "case forcing"
10442 .cindex "upper casing"
10443 .cindex "expansion" "case forcing"
10444 .cindex "&%uc%& expansion item"
10445 This forces the letters in the string into upper-case.
10447 .vitem &*${utf8clean:*&<&'string'&>&*}*&
10448 .cindex "correction of invalid utf-8 sequences in strings"
10449 .cindex "utf-8" "utf-8 sequences"
10450 .cindex "incorrect utf-8"
10451 .cindex "expansion" "utf-8 forcing"
10452 .cindex "&%utf8clean%& expansion item"
10453 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
10461 .section "Expansion conditions" "SECTexpcond"
10462 .scindex IIDexpcond "expansion" "conditions"
10463 The following conditions are available for testing by the &%${if%& construct
10464 while expanding strings:
10467 .vitem &*!*&<&'condition'&>
10468 .cindex "expansion" "negating a condition"
10469 .cindex "negation" "in expansion condition"
10470 Preceding any condition with an exclamation mark negates the result of the
10473 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10474 .cindex "numeric comparison"
10475 .cindex "expansion" "numeric comparison"
10476 There are a number of symbolic operators for doing numeric comparisons. They
10482 &`>= `& greater or equal
10484 &`<= `& less or equal
10488 ${if >{$message_size}{10M} ...
10490 Note that the general negation operator provides for inequality testing. The
10491 two strings must take the form of optionally signed decimal integers,
10492 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
10493 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
10494 As a special case, the numerical value of an empty string is taken as
10497 In all cases, a relative comparator OP is testing if <&'string1'&> OP
10498 <&'string2'&>; the above example is checking if &$message_size$& is larger than
10499 10M, not if 10M is larger than &$message_size$&.
10502 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
10503 {*&<&'arg2'&>&*}...}*&
10504 .cindex "expansion" "calling an acl"
10505 .cindex "&%acl%&" "expansion condition"
10506 The name and zero to nine argument strings are first expanded separately. The expanded
10507 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
10508 Any unused are made empty. The variable &$acl_narg$& is set to the number of
10509 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
10510 and may use the variables; if another acl expansion is used the values
10511 are restored after it returns. If the ACL sets
10512 a value using a "message =" modifier the variable $value becomes
10513 the result of the expansion, otherwise it is empty.
10514 If the ACL returns accept the condition is true; if deny, false.
10515 If the ACL returns defer the result is a forced-fail.
10517 .vitem &*bool&~{*&<&'string'&>&*}*&
10518 .cindex "expansion" "boolean parsing"
10519 .cindex "&%bool%& expansion condition"
10520 This condition turns a string holding a true or false representation into
10521 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
10522 (case-insensitively); also integer numbers map to true if non-zero,
10524 An empty string is treated as false.
10525 Leading and trailing whitespace is ignored;
10526 thus a string consisting only of whitespace is false.
10527 All other string values will result in expansion failure.
10529 When combined with ACL variables, this expansion condition will let you
10530 make decisions in one place and act on those decisions in another place.
10533 ${if bool{$acl_m_privileged_sender} ...
10537 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
10538 .cindex "expansion" "boolean parsing"
10539 .cindex "&%bool_lax%& expansion condition"
10540 Like &%bool%&, this condition turns a string into a boolean state. But
10541 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
10542 loose definition that the Router &%condition%& option uses. The empty string
10543 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
10544 true. Leading and trailing whitespace is ignored.
10546 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
10548 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10549 .cindex "expansion" "encrypted comparison"
10550 .cindex "encrypted strings, comparing"
10551 .cindex "&%crypteq%& expansion condition"
10552 This condition is included in the Exim binary if it is built to support any
10553 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
10554 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
10555 included in the binary.
10557 The &%crypteq%& condition has two arguments. The first is encrypted and
10558 compared against the second, which is already encrypted. The second string may
10559 be in the LDAP form for storing encrypted strings, which starts with the
10560 encryption type in curly brackets, followed by the data. If the second string
10561 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
10562 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
10563 Typically this will be a field from a password file. An example of an encrypted
10564 string in LDAP form is:
10566 {md5}CY9rzUYh03PK3k6DJie09g==
10568 If such a string appears directly in an expansion, the curly brackets have to
10569 be quoted, because they are part of the expansion syntax. For example:
10571 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
10573 The following encryption types (whose names are matched case-independently) are
10578 .cindex "base64 encoding" "in encrypted password"
10579 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
10580 printable characters to compare with the remainder of the second string. If the
10581 length of the comparison string is 24, Exim assumes that it is base64 encoded
10582 (as in the above example). If the length is 32, Exim assumes that it is a
10583 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
10587 .cindex "SHA-1 hash"
10588 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
10589 printable characters to compare with the remainder of the second string. If the
10590 length of the comparison string is 28, Exim assumes that it is base64 encoded.
10591 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
10592 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
10595 .cindex "&[crypt()]&"
10596 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
10597 only the first eight characters of the password. However, in modern operating
10598 systems this is no longer true, and in many cases the entire password is used,
10599 whatever its length.
10602 .cindex "&[crypt16()]&"
10603 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
10604 use up to 16 characters of the password in some operating systems. Again, in
10605 modern operating systems, more characters may be used.
10607 Exim has its own version of &[crypt16()]&, which is just a double call to
10608 &[crypt()]&. For operating systems that have their own version, setting
10609 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
10610 operating system version instead of its own. This option is set by default in
10611 the OS-dependent &_Makefile_& for those operating systems that are known to
10612 support &[crypt16()]&.
10614 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
10615 it was not using the same algorithm as some operating systems' versions. It
10616 turns out that as well as &[crypt16()]& there is a function called
10617 &[bigcrypt()]& in some operating systems. This may or may not use the same
10618 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
10620 However, since there is now a move away from the traditional &[crypt()]&
10621 functions towards using SHA1 and other algorithms, tidying up this area of
10622 Exim is seen as very low priority.
10624 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
10625 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
10626 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
10627 default is &`{crypt}`&. Whatever the default, you can always use either
10628 function by specifying it explicitly in curly brackets.
10630 .vitem &*def:*&<&'variable&~name'&>
10631 .cindex "expansion" "checking for empty variable"
10632 .cindex "&%def%& expansion condition"
10633 The &%def%& condition must be followed by the name of one of the expansion
10634 variables defined in section &<<SECTexpvar>>&. The condition is true if the
10635 variable does not contain the empty string. For example:
10637 ${if def:sender_ident {from $sender_ident}}
10639 Note that the variable name is given without a leading &%$%& character. If the
10640 variable does not exist, the expansion fails.
10642 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
10643 &~&*def:h_*&<&'header&~name'&>&*:*&"
10644 .cindex "expansion" "checking header line existence"
10645 This condition is true if a message is being processed and the named header
10646 exists in the message. For example,
10648 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
10650 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
10651 the header name must be terminated by a colon if white space does not follow.
10653 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10654 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10655 .cindex "string" "comparison"
10656 .cindex "expansion" "string comparison"
10657 .cindex "&%eq%& expansion condition"
10658 .cindex "&%eqi%& expansion condition"
10659 The two substrings are first expanded. The condition is true if the two
10660 resulting strings are identical. For &%eq%& the comparison includes the case of
10661 letters, whereas for &%eqi%& the comparison is case-independent.
10663 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
10664 .cindex "expansion" "file existence test"
10665 .cindex "file" "existence test"
10666 .cindex "&%exists%&, expansion condition"
10667 The substring is first expanded and then interpreted as an absolute path. The
10668 condition is true if the named file (or directory) exists. The existence test
10669 is done by calling the &[stat()]& function. The use of the &%exists%& test in
10670 users' filter files may be locked out by the system administrator.
10672 .vitem &*first_delivery*&
10673 .cindex "delivery" "first"
10674 .cindex "first delivery"
10675 .cindex "expansion" "first delivery test"
10676 .cindex "&%first_delivery%& expansion condition"
10677 This condition, which has no data, is true during a message's first delivery
10678 attempt. It is false during any subsequent delivery attempts.
10681 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
10682 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
10683 .cindex "list" "iterative conditions"
10684 .cindex "expansion" "&*forall*& condition"
10685 .cindex "expansion" "&*forany*& condition"
10687 These conditions iterate over a list. The first argument is expanded to form
10688 the list. By default, the list separator is a colon, but it can be changed by
10689 the normal method. The second argument is interpreted as a condition that is to
10690 be applied to each item in the list in turn. During the interpretation of the
10691 condition, the current list item is placed in a variable called &$item$&.
10693 For &*forany*&, interpretation stops if the condition is true for any item, and
10694 the result of the whole condition is true. If the condition is false for all
10695 items in the list, the overall condition is false.
10697 For &*forall*&, interpretation stops if the condition is false for any item,
10698 and the result of the whole condition is false. If the condition is true for
10699 all items in the list, the overall condition is true.
10701 Note that negation of &*forany*& means that the condition must be false for all
10702 items for the overall condition to succeed, and negation of &*forall*& means
10703 that the condition must be false for at least one item. In this example, the
10704 list separator is changed to a comma:
10706 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
10708 The value of &$item$& is saved and restored while &*forany*& or &*forall*& is
10709 being processed, to enable these expansion items to be nested.
10711 To scan a named list, expand it with the &*listnamed*& operator.
10714 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10715 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10716 .cindex "string" "comparison"
10717 .cindex "expansion" "string comparison"
10718 .cindex "&%ge%& expansion condition"
10719 .cindex "&%gei%& expansion condition"
10720 The two substrings are first expanded. The condition is true if the first
10721 string is lexically greater than or equal to the second string. For &%ge%& the
10722 comparison includes the case of letters, whereas for &%gei%& the comparison is
10725 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10726 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10727 .cindex "string" "comparison"
10728 .cindex "expansion" "string comparison"
10729 .cindex "&%gt%& expansion condition"
10730 .cindex "&%gti%& expansion condition"
10731 The two substrings are first expanded. The condition is true if the first
10732 string is lexically greater than the second string. For &%gt%& the comparison
10733 includes the case of letters, whereas for &%gti%& the comparison is
10736 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10737 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10738 .cindex "string" "comparison"
10739 .cindex "list" "iterative conditions"
10740 Both strings are expanded; the second string is treated as a list of simple
10741 strings; if the first string is a member of the second, then the condition
10744 These are simpler to use versions of the more powerful &*forany*& condition.
10745 Examples, and the &*forany*& equivalents:
10747 ${if inlist{needle}{foo:needle:bar}}
10748 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
10749 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
10750 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
10753 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
10754 &*isip4&~{*&<&'string'&>&*}*& &&&
10755 &*isip6&~{*&<&'string'&>&*}*&
10756 .cindex "IP address" "testing string format"
10757 .cindex "string" "testing for IP address"
10758 .cindex "&%isip%& expansion condition"
10759 .cindex "&%isip4%& expansion condition"
10760 .cindex "&%isip6%& expansion condition"
10761 The substring is first expanded, and then tested to see if it has the form of
10762 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
10763 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
10765 For an IPv4 address, the test is for four dot-separated components, each of
10766 which consists of from one to three digits. For an IPv6 address, up to eight
10767 colon-separated components are permitted, each containing from one to four
10768 hexadecimal digits. There may be fewer than eight components if an empty
10769 component (adjacent colons) is present. Only one empty component is permitted.
10771 &*Note*&: The checks are just on the form of the address; actual numerical
10772 values are not considered. Thus, for example, 999.999.999.999 passes the IPv4
10773 check. The main use of these tests is to distinguish between IP addresses and
10774 host names, or between IPv4 and IPv6 addresses. For example, you could use
10776 ${if isip4{$sender_host_address}...
10778 to test which IP version an incoming SMTP connection is using.
10780 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
10781 .cindex "LDAP" "use for authentication"
10782 .cindex "expansion" "LDAP authentication test"
10783 .cindex "&%ldapauth%& expansion condition"
10784 This condition supports user authentication using LDAP. See section
10785 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
10786 queries. For this use, the query must contain a user name and password. The
10787 query itself is not used, and can be empty. The condition is true if the
10788 password is not empty, and the user name and password are accepted by the LDAP
10789 server. An empty password is rejected without calling LDAP because LDAP binds
10790 with an empty password are considered anonymous regardless of the username, and
10791 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
10792 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
10796 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10797 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10798 .cindex "string" "comparison"
10799 .cindex "expansion" "string comparison"
10800 .cindex "&%le%& expansion condition"
10801 .cindex "&%lei%& expansion condition"
10802 The two substrings are first expanded. The condition is true if the first
10803 string is lexically less than or equal to the second string. For &%le%& the
10804 comparison includes the case of letters, whereas for &%lei%& the comparison is
10807 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10808 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10809 .cindex "string" "comparison"
10810 .cindex "expansion" "string comparison"
10811 .cindex "&%lt%& expansion condition"
10812 .cindex "&%lti%& expansion condition"
10813 The two substrings are first expanded. The condition is true if the first
10814 string is lexically less than the second string. For &%lt%& the comparison
10815 includes the case of letters, whereas for &%lti%& the comparison is
10819 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10820 .cindex "expansion" "regular expression comparison"
10821 .cindex "regular expressions" "match in expanded string"
10822 .cindex "&%match%& expansion condition"
10823 The two substrings are first expanded. The second is then treated as a regular
10824 expression and applied to the first. Because of the pre-expansion, if the
10825 regular expression contains dollar, or backslash characters, they must be
10826 escaped. Care must also be taken if the regular expression contains braces
10827 (curly brackets). A closing brace must be escaped so that it is not taken as a
10828 premature termination of <&'string2'&>. The easiest approach is to use the
10829 &`\N`& feature to disable expansion of the regular expression.
10832 ${if match {$local_part}{\N^\d{3}\N} ...
10834 If the whole expansion string is in double quotes, further escaping of
10835 backslashes is also required.
10837 The condition is true if the regular expression match succeeds.
10838 The regular expression is not required to begin with a circumflex
10839 metacharacter, but if there is no circumflex, the expression is not anchored,
10840 and it may match anywhere in the subject, not just at the start. If you want
10841 the pattern to match at the end of the subject, you must include the &`$`&
10842 metacharacter at an appropriate point.
10844 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
10845 At the start of an &%if%& expansion the values of the numeric variable
10846 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
10847 succeeds causes them to be reset to the substrings of that condition and they
10848 will have these values during the expansion of the success string. At the end
10849 of the &%if%& expansion, the previous values are restored. After testing a
10850 combination of conditions using &%or%&, the subsequent values of the numeric
10851 variables are those of the condition that succeeded.
10853 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10854 .cindex "&%match_address%& expansion condition"
10855 See &*match_local_part*&.
10857 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10858 .cindex "&%match_domain%& expansion condition"
10859 See &*match_local_part*&.
10861 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10862 .cindex "&%match_ip%& expansion condition"
10863 This condition matches an IP address to a list of IP address patterns. It must
10864 be followed by two argument strings. The first (after expansion) must be an IP
10865 address or an empty string. The second (not expanded) is a restricted host
10866 list that can match only an IP address, not a host name. For example:
10868 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
10870 The specific types of host list item that are permitted in the list are:
10873 An IP address, optionally with a CIDR mask.
10875 A single asterisk, which matches any IP address.
10877 An empty item, which matches only if the IP address is empty. This could be
10878 useful for testing for a locally submitted message or one from specific hosts
10879 in a single test such as
10880 . ==== As this is a nested list, any displays it contains must be indented
10881 . ==== as otherwise they are too far to the left. This comment applies to
10882 . ==== the use of xmlto plus fop. There's no problem when formatting with
10883 . ==== sdop, with or without the extra indent.
10885 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
10887 where the first item in the list is the empty string.
10889 The item @[] matches any of the local host's interface addresses.
10891 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
10892 even if &`net-`& is not specified. There is never any attempt to turn the IP
10893 address into a host name. The most common type of linear search for
10894 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
10895 masks. For example:
10897 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
10899 It is of course possible to use other kinds of lookup, and in such a case, you
10900 do need to specify the &`net-`& prefix if you want to specify a specific
10901 address mask, for example:
10903 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
10905 However, unless you are combining a &%match_ip%& condition with others, it is
10906 just as easy to use the fact that a lookup is itself a condition, and write:
10908 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
10912 Note that <&'string2'&> is not itself subject to string expansion, unless
10913 Exim was built with the EXPAND_LISTMATCH_RHS option.
10915 Consult section &<<SECThoslispatip>>& for further details of these patterns.
10917 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10918 .cindex "domain list" "in expansion condition"
10919 .cindex "address list" "in expansion condition"
10920 .cindex "local part" "list, in expansion condition"
10921 .cindex "&%match_local_part%& expansion condition"
10922 This condition, together with &%match_address%& and &%match_domain%&, make it
10923 possible to test domain, address, and local part lists within expansions. Each
10924 condition requires two arguments: an item and a list to match. A trivial
10927 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
10929 In each case, the second argument may contain any of the allowable items for a
10930 list of the appropriate type. Also, because the second argument (after
10931 expansion) is a standard form of list, it is possible to refer to a named list.
10932 Thus, you can use conditions like this:
10934 ${if match_domain{$domain}{+local_domains}{...
10936 .cindex "&`+caseful`&"
10937 For address lists, the matching starts off caselessly, but the &`+caseful`&
10938 item can be used, as in all address lists, to cause subsequent items to
10939 have their local parts matched casefully. Domains are always matched
10942 Note that <&'string2'&> is not itself subject to string expansion, unless
10943 Exim was built with the EXPAND_LISTMATCH_RHS option.
10945 &*Note*&: Host lists are &'not'& supported in this way. This is because
10946 hosts have two identities: a name and an IP address, and it is not clear
10947 how to specify cleanly how such a test would work. However, IP addresses can be
10948 matched using &%match_ip%&.
10950 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
10951 .cindex "PAM authentication"
10952 .cindex "AUTH" "with PAM"
10953 .cindex "Solaris" "PAM support"
10954 .cindex "expansion" "PAM authentication test"
10955 .cindex "&%pam%& expansion condition"
10956 &'Pluggable Authentication Modules'&
10957 (&url(http://www.kernel.org/pub/linux/libs/pam/)) are a facility that is
10958 available in the latest releases of Solaris and in some GNU/Linux
10959 distributions. The Exim support, which is intended for use in conjunction with
10960 the SMTP AUTH command, is available only if Exim is compiled with
10964 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
10965 in some releases of GNU/Linux &%-ldl%& is also needed.
10967 The argument string is first expanded, and the result must be a
10968 colon-separated list of strings. Leading and trailing white space is ignored.
10969 The PAM module is initialized with the service name &"exim"& and the user name
10970 taken from the first item in the colon-separated data string (<&'string1'&>).
10971 The remaining items in the data string are passed over in response to requests
10972 from the authentication function. In the simple case there will only be one
10973 request, for a password, so the data consists of just two strings.
10975 There can be problems if any of the strings are permitted to contain colon
10976 characters. In the usual way, these have to be doubled to avoid being taken as
10977 separators. If the data is being inserted from a variable, the &%sg%& expansion
10978 item can be used to double any existing colons. For example, the configuration
10979 of a LOGIN authenticator might contain this setting:
10981 server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
10983 For a PLAIN authenticator you could use:
10985 server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
10987 In some operating systems, PAM authentication can be done only from a process
10988 running as root. Since Exim is running as the Exim user when receiving
10989 messages, this means that PAM cannot be used directly in those systems.
10990 A patched version of the &'pam_unix'& module that comes with the
10991 Linux PAM package is available from &url(http://www.e-admin.de/pam_exim/).
10992 The patched module allows one special uid/gid combination, in addition to root,
10993 to authenticate. If you build the patched module to allow the Exim user and
10994 group, PAM can then be used from an Exim authenticator.
10997 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
10998 .cindex "&'pwcheck'& daemon"
11000 .cindex "expansion" "&'pwcheck'& authentication test"
11001 .cindex "&%pwcheck%& expansion condition"
11002 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
11003 This is one way of making it possible for passwords to be checked by a process
11004 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
11005 deprecated. Its replacement is &'saslauthd'& (see below).
11007 The pwcheck support is not included in Exim by default. You need to specify
11008 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
11009 building Exim. For example:
11011 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
11013 You do not need to install the full Cyrus software suite in order to use
11014 the pwcheck daemon. You can compile and install just the daemon alone
11015 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
11016 access to the &_/var/pwcheck_& directory.
11018 The &%pwcheck%& condition takes one argument, which must be the user name and
11019 password, separated by a colon. For example, in a LOGIN authenticator
11020 configuration, you might have this:
11022 server_condition = ${if pwcheck{$auth1:$auth2}}
11024 Again, for a PLAIN authenticator configuration, this would be:
11026 server_condition = ${if pwcheck{$auth2:$auth3}}
11028 .vitem &*queue_running*&
11029 .cindex "queue runner" "detecting when delivering from"
11030 .cindex "expansion" "queue runner test"
11031 .cindex "&%queue_running%& expansion condition"
11032 This condition, which has no data, is true during delivery attempts that are
11033 initiated by queue runner processes, and false otherwise.
11036 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
11038 .cindex "expansion" "Radius authentication"
11039 .cindex "&%radius%& expansion condition"
11040 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
11041 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
11042 the Radius client configuration file in order to build Exim with Radius
11045 With just that one setting, Exim expects to be linked with the &%radiusclient%&
11046 library, using the original API. If you are using release 0.4.0 or later of
11047 this library, you need to set
11049 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
11051 in &_Local/Makefile_& when building Exim. You can also link Exim with the
11052 &%libradius%& library that comes with FreeBSD. To do this, set
11054 RADIUS_LIB_TYPE=RADLIB
11056 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
11057 You may also have to supply a suitable setting in EXTRALIBS so that the
11058 Radius library can be found when Exim is linked.
11060 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
11061 Radius client library, which calls the Radius server. The condition is true if
11062 the authentication is successful. For example:
11064 server_condition = ${if radius{<arguments>}}
11068 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
11069 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
11070 .cindex "&'saslauthd'& daemon"
11072 .cindex "expansion" "&'saslauthd'& authentication test"
11073 .cindex "&%saslauthd%& expansion condition"
11074 This condition supports user authentication using the Cyrus &'saslauthd'&
11075 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
11076 Using this daemon is one way of making it possible for passwords to be checked
11077 by a process that is not running as root.
11079 The saslauthd support is not included in Exim by default. You need to specify
11080 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
11081 building Exim. For example:
11083 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
11085 You do not need to install the full Cyrus software suite in order to use
11086 the saslauthd daemon. You can compile and install just the daemon alone
11087 from the Cyrus SASL library.
11089 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
11090 two are mandatory. For example:
11092 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
11094 The service and the realm are optional (which is why the arguments are enclosed
11095 in their own set of braces). For details of the meaning of the service and
11096 realm, and how to run the daemon, consult the Cyrus documentation.
11101 .section "Combining expansion conditions" "SECID84"
11102 .cindex "expansion" "combining conditions"
11103 Several conditions can be tested at once by combining them using the &%and%&
11104 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
11105 conditions on their own, and precede their lists of sub-conditions. Each
11106 sub-condition must be enclosed in braces within the overall braces that contain
11107 the list. No repetition of &%if%& is used.
11111 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
11112 .cindex "&""or""& expansion condition"
11113 .cindex "expansion" "&""or""& of conditions"
11114 The sub-conditions are evaluated from left to right. The condition is true if
11115 any one of the sub-conditions is true.
11118 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
11120 When a true sub-condition is found, the following ones are parsed but not
11121 evaluated. If there are several &"match"& sub-conditions the values of the
11122 numeric variables afterwards are taken from the first one that succeeds.
11124 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
11125 .cindex "&""and""& expansion condition"
11126 .cindex "expansion" "&""and""& of conditions"
11127 The sub-conditions are evaluated from left to right. The condition is true if
11128 all of the sub-conditions are true. If there are several &"match"&
11129 sub-conditions, the values of the numeric variables afterwards are taken from
11130 the last one. When a false sub-condition is found, the following ones are
11131 parsed but not evaluated.
11133 .ecindex IIDexpcond
11138 .section "Expansion variables" "SECTexpvar"
11139 .cindex "expansion" "variables, list of"
11140 This section contains an alphabetical list of all the expansion variables. Some
11141 of them are available only when Exim is compiled with specific options such as
11142 support for TLS or the content scanning extension.
11145 .vitem "&$0$&, &$1$&, etc"
11146 .cindex "numerical variables (&$1$& &$2$& etc)"
11147 When a &%match%& expansion condition succeeds, these variables contain the
11148 captured substrings identified by the regular expression during subsequent
11149 processing of the success string of the containing &%if%& expansion item.
11150 In the expansion condition case
11151 they do not retain their values afterwards; in fact, their previous
11152 values are restored at the end of processing an &%if%& item. The numerical
11153 variables may also be set externally by some other matching process which
11154 precedes the expansion of the string. For example, the commands available in
11155 Exim filter files include an &%if%& command with its own regular expression
11156 matching condition.
11158 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
11159 Within an acl condition, expansion condition or expansion item
11160 any arguments are copied to these variables,
11161 any unused variables being made empty.
11163 .vitem "&$acl_c...$&"
11164 Values can be placed in these variables by the &%set%& modifier in an ACL. They
11165 can be given any name that starts with &$acl_c$& and is at least six characters
11166 long, but the sixth character must be either a digit or an underscore. For
11167 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
11168 variables persist throughout the lifetime of an SMTP connection. They can be
11169 used to pass information between ACLs and between different invocations of the
11170 same ACL. When a message is received, the values of these variables are saved
11171 with the message, and can be accessed by filters, routers, and transports
11172 during subsequent delivery.
11174 .vitem "&$acl_m...$&"
11175 These variables are like the &$acl_c...$& variables, except that their values
11176 are reset after a message has been received. Thus, if several messages are
11177 received in one SMTP connection, &$acl_m...$& values are not passed on from one
11178 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
11179 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
11180 message is received, the values of these variables are saved with the message,
11181 and can be accessed by filters, routers, and transports during subsequent
11184 .vitem &$acl_narg$&
11185 Within an acl condition, expansion condition or expansion item
11186 this variable has the number of arguments.
11188 .vitem &$acl_verify_message$&
11189 .vindex "&$acl_verify_message$&"
11190 After an address verification has failed, this variable contains the failure
11191 message. It retains its value for use in subsequent modifiers. The message can
11192 be preserved by coding like this:
11194 warn !verify = sender
11195 set acl_m0 = $acl_verify_message
11197 You can use &$acl_verify_message$& during the expansion of the &%message%& or
11198 &%log_message%& modifiers, to include information about the verification
11201 .vitem &$address_data$&
11202 .vindex "&$address_data$&"
11203 This variable is set by means of the &%address_data%& option in routers. The
11204 value then remains with the address while it is processed by subsequent routers
11205 and eventually a transport. If the transport is handling multiple addresses,
11206 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
11207 for more details. &*Note*&: The contents of &$address_data$& are visible in
11210 If &$address_data$& is set when the routers are called from an ACL to verify
11211 a recipient address, the final value is still in the variable for subsequent
11212 conditions and modifiers of the ACL statement. If routing the address caused it
11213 to be redirected to just one address, the child address is also routed as part
11214 of the verification, and in this case the final value of &$address_data$& is
11215 from the child's routing.
11217 If &$address_data$& is set when the routers are called from an ACL to verify a
11218 sender address, the final value is also preserved, but this time in
11219 &$sender_address_data$&, to distinguish it from data from a recipient
11222 In both cases (recipient and sender verification), the value does not persist
11223 after the end of the current ACL statement. If you want to preserve
11224 these values for longer, you can save them in ACL variables.
11226 .vitem &$address_file$&
11227 .vindex "&$address_file$&"
11228 When, as a result of aliasing, forwarding, or filtering, a message is directed
11229 to a specific file, this variable holds the name of the file when the transport
11230 is running. At other times, the variable is empty. For example, using the
11231 default configuration, if user &%r2d2%& has a &_.forward_& file containing
11233 /home/r2d2/savemail
11235 then when the &(address_file)& transport is running, &$address_file$&
11236 contains the text string &`/home/r2d2/savemail`&.
11237 .cindex "Sieve filter" "value of &$address_file$&"
11238 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
11239 then up to the transport configuration to generate an appropriate absolute path
11240 to the relevant file.
11242 .vitem &$address_pipe$&
11243 .vindex "&$address_pipe$&"
11244 When, as a result of aliasing or forwarding, a message is directed to a pipe,
11245 this variable holds the pipe command when the transport is running.
11247 .vitem "&$auth1$& &-- &$auth3$&"
11248 .vindex "&$auth1$&, &$auth2$&, etc"
11249 These variables are used in SMTP authenticators (see chapters
11250 &<<CHAPplaintext>>&&--&<<CHAPspa>>&). Elsewhere, they are empty.
11252 .vitem &$authenticated_id$&
11253 .cindex "authentication" "id"
11254 .vindex "&$authenticated_id$&"
11255 When a server successfully authenticates a client it may be configured to
11256 preserve some of the authentication information in the variable
11257 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
11258 user/password authenticator configuration might preserve the user name for use
11259 in the routers. Note that this is not the same information that is saved in
11260 &$sender_host_authenticated$&.
11261 When a message is submitted locally (that is, not over a TCP connection)
11262 the value of &$authenticated_id$& is normally the login name of the calling
11263 process. However, a trusted user can override this by means of the &%-oMai%&
11264 command line option.
11266 .vitem &$authenticated_fail_id$&
11267 .cindex "authentication" "fail" "id"
11268 .vindex "&$authenticated_fail_id$&"
11269 When an authentication attempt fails, the variable &$authenticated_fail_id$&
11270 will contain the failed authentication id. If more than one authentication
11271 id is attempted, it will contain only the last one. The variable is
11272 available for processing in the ACL's, generally the quit or notquit ACL.
11273 A message to a local recipient could still be accepted without requiring
11274 authentication, which means this variable could also be visible in all of
11278 .vitem &$authenticated_sender$&
11279 .cindex "sender" "authenticated"
11280 .cindex "authentication" "sender"
11281 .cindex "AUTH" "on MAIL command"
11282 .vindex "&$authenticated_sender$&"
11283 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
11284 SMTP MAIL command if it believes the sender is sufficiently trusted, as
11285 described in section &<<SECTauthparamail>>&. Unless the data is the string
11286 &"<>"&, it is set as the authenticated sender of the message, and the value is
11287 available during delivery in the &$authenticated_sender$& variable. If the
11288 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
11290 .vindex "&$qualify_domain$&"
11291 When a message is submitted locally (that is, not over a TCP connection), the
11292 value of &$authenticated_sender$& is an address constructed from the login
11293 name of the calling process and &$qualify_domain$&, except that a trusted user
11294 can override this by means of the &%-oMas%& command line option.
11297 .vitem &$authentication_failed$&
11298 .cindex "authentication" "failure"
11299 .vindex "&$authentication_failed$&"
11300 This variable is set to &"1"& in an Exim server if a client issues an AUTH
11301 command that does not succeed. Otherwise it is set to &"0"&. This makes it
11302 possible to distinguish between &"did not try to authenticate"&
11303 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
11304 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
11305 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
11306 negative response to an AUTH command, including (for example) an attempt to use
11307 an undefined mechanism.
11309 .vitem &$av_failed$&
11310 .cindex "content scanning" "AV scanner failure"
11311 This variable is available when Exim is compiled with the content-scanning
11312 extension. It is set to &"0"& by default, but will be set to &"1"& if any
11313 problem occurs with the virus scanner (specified by &%av_scanner%&) during
11314 the ACL malware condition.
11316 .vitem &$body_linecount$&
11317 .cindex "message body" "line count"
11318 .cindex "body of message" "line count"
11319 .vindex "&$body_linecount$&"
11320 When a message is being received or delivered, this variable contains the
11321 number of lines in the message's body. See also &$message_linecount$&.
11323 .vitem &$body_zerocount$&
11324 .cindex "message body" "binary zero count"
11325 .cindex "body of message" "binary zero count"
11326 .cindex "binary zero" "in message body"
11327 .vindex "&$body_zerocount$&"
11328 When a message is being received or delivered, this variable contains the
11329 number of binary zero bytes (ASCII NULs) in the message's body.
11331 .vitem &$bounce_recipient$&
11332 .vindex "&$bounce_recipient$&"
11333 This is set to the recipient address of a bounce message while Exim is creating
11334 it. It is useful if a customized bounce message text file is in use (see
11335 chapter &<<CHAPemsgcust>>&).
11337 .vitem &$bounce_return_size_limit$&
11338 .vindex "&$bounce_return_size_limit$&"
11339 This contains the value set in the &%bounce_return_size_limit%& option, rounded
11340 up to a multiple of 1000. It is useful when a customized error message text
11341 file is in use (see chapter &<<CHAPemsgcust>>&).
11343 .vitem &$caller_gid$&
11344 .cindex "gid (group id)" "caller"
11345 .vindex "&$caller_gid$&"
11346 The real group id under which the process that called Exim was running. This is
11347 not the same as the group id of the originator of a message (see
11348 &$originator_gid$&). If Exim re-execs itself, this variable in the new
11349 incarnation normally contains the Exim gid.
11351 .vitem &$caller_uid$&
11352 .cindex "uid (user id)" "caller"
11353 .vindex "&$caller_uid$&"
11354 The real user id under which the process that called Exim was running. This is
11355 not the same as the user id of the originator of a message (see
11356 &$originator_uid$&). If Exim re-execs itself, this variable in the new
11357 incarnation normally contains the Exim uid.
11359 .vitem &$callout_address$&
11360 .vindex "&$callout_address$&"
11361 After a callout for verification, spamd or malware daemon service, the
11362 address that was connected to.
11364 .vitem &$compile_number$&
11365 .vindex "&$compile_number$&"
11366 The building process for Exim keeps a count of the number
11367 of times it has been compiled. This serves to distinguish different
11368 compilations of the same version of the program.
11370 .vitem &$config_dir$&
11371 .vindex "&$config_dir$&"
11372 The directory name of the main configuration file. That is, the content of
11373 &$config_file$& with the last component stripped. The value does not
11374 contain the trailing slash. If &$config_file$& does not contain a slash,
11375 &$config_dir$& is ".".
11377 .vitem &$config_file$&
11378 .vindex "&$config_file$&"
11379 The name of the main configuration file Exim is using.
11381 .vitem &$demime_errorlevel$&
11382 .vindex "&$demime_errorlevel$&"
11383 This variable is available when Exim is compiled with
11384 the content-scanning extension and the obsolete &%demime%& condition. For
11385 details, see section &<<SECTdemimecond>>&.
11387 .vitem &$demime_reason$&
11388 .vindex "&$demime_reason$&"
11389 This variable is available when Exim is compiled with the
11390 content-scanning extension and the obsolete &%demime%& condition. For details,
11391 see section &<<SECTdemimecond>>&.
11393 .vitem &$dkim_cur_signer$& &&&
11394 &$dkim_verify_status$& &&&
11395 &$dkim_verify_reason$& &&&
11396 &$dkim_domain$& &&&
11397 &$dkim_identity$& &&&
11398 &$dkim_selector$& &&&
11400 &$dkim_canon_body$& &&&
11401 &$dkim_canon_headers$& &&&
11402 &$dkim_copiedheaders$& &&&
11403 &$dkim_bodylength$& &&&
11404 &$dkim_created$& &&&
11405 &$dkim_expires$& &&&
11406 &$dkim_headernames$& &&&
11407 &$dkim_key_testing$& &&&
11408 &$dkim_key_nosubdomains$& &&&
11409 &$dkim_key_srvtype$& &&&
11410 &$dkim_key_granularity$& &&&
11412 These variables are only available within the DKIM ACL.
11413 For details see chapter &<<CHAPdkim>>&.
11415 .vitem &$dkim_signers$&
11416 .vindex &$dkim_signers$&
11417 When a message has been received this variable contains
11418 a colon-separated list of signer domains and identities for the message.
11419 For details see chapter &<<CHAPdkim>>&.
11421 .vitem &$dnslist_domain$& &&&
11422 &$dnslist_matched$& &&&
11423 &$dnslist_text$& &&&
11425 .vindex "&$dnslist_domain$&"
11426 .vindex "&$dnslist_matched$&"
11427 .vindex "&$dnslist_text$&"
11428 .vindex "&$dnslist_value$&"
11429 .cindex "black list (DNS)"
11430 When a DNS (black) list lookup succeeds, these variables are set to contain
11431 the following data from the lookup: the list's domain name, the key that was
11432 looked up, the contents of any associated TXT record, and the value from the
11433 main A record. See section &<<SECID204>>& for more details.
11436 .vindex "&$domain$&"
11437 When an address is being routed, or delivered on its own, this variable
11438 contains the domain. Uppercase letters in the domain are converted into lower
11439 case for &$domain$&.
11441 Global address rewriting happens when a message is received, so the value of
11442 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
11443 is set during user filtering, but not during system filtering, because a
11444 message may have many recipients and the system filter is called just once.
11446 When more than one address is being delivered at once (for example, several
11447 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
11448 have the same domain. Transports can be restricted to handling only one domain
11449 at a time if the value of &$domain$& is required at transport time &-- this is
11450 the default for local transports. For further details of the environment in
11451 which local transports are run, see chapter &<<CHAPenvironment>>&.
11453 .oindex "&%delay_warning_condition%&"
11454 At the end of a delivery, if all deferred addresses have the same domain, it is
11455 set in &$domain$& during the expansion of &%delay_warning_condition%&.
11457 The &$domain$& variable is also used in some other circumstances:
11460 When an ACL is running for a RCPT command, &$domain$& contains the domain of
11461 the recipient address. The domain of the &'sender'& address is in
11462 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
11463 normally set during the running of the MAIL ACL. However, if the sender address
11464 is verified with a callout during the MAIL ACL, the sender domain is placed in
11465 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
11466 the &(smtp)& transport.
11469 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
11470 &$domain$& contains the domain portion of the address that is being rewritten;
11471 it can be used in the expansion of the replacement address, for example, to
11472 rewrite domains by file lookup.
11475 With one important exception, whenever a domain list is being scanned,
11476 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
11477 a &%sender_domains%& condition in an ACL is being processed, the subject domain
11478 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
11479 that, in a RCPT ACL, the sender domain list can be dependent on the
11480 recipient domain (which is what is in &$domain$& at this time).
11483 .cindex "ETRN" "value of &$domain$&"
11484 .oindex "&%smtp_etrn_command%&"
11485 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
11486 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
11490 .vitem &$domain_data$&
11491 .vindex "&$domain_data$&"
11492 When the &%domains%& option on a router matches a domain by
11493 means of a lookup, the data read by the lookup is available during the running
11494 of the router as &$domain_data$&. In addition, if the driver routes the
11495 address to a transport, the value is available in that transport. If the
11496 transport is handling multiple addresses, the value from the first address is
11499 &$domain_data$& is also set when the &%domains%& condition in an ACL matches a
11500 domain by means of a lookup. The data read by the lookup is available during
11501 the rest of the ACL statement. In all other situations, this variable expands
11504 .vitem &$exim_gid$&
11505 .vindex "&$exim_gid$&"
11506 This variable contains the numerical value of the Exim group id.
11508 .vitem &$exim_path$&
11509 .vindex "&$exim_path$&"
11510 This variable contains the path to the Exim binary.
11512 .vitem &$exim_uid$&
11513 .vindex "&$exim_uid$&"
11514 This variable contains the numerical value of the Exim user id.
11516 .vitem &$exim_version$&
11517 .vindex "&$exim_version$&"
11518 This variable contains the version string of the Exim build.
11519 The first character is a major version number, currently 4.
11520 Then after a dot, the next group of digits is a minor version number.
11521 There may be other characters following the minor version.
11523 .vitem &$found_extension$&
11524 .vindex "&$found_extension$&"
11525 This variable is available when Exim is compiled with the
11526 content-scanning extension and the obsolete &%demime%& condition. For details,
11527 see section &<<SECTdemimecond>>&.
11529 .vitem &$header_$&<&'name'&>
11530 This is not strictly an expansion variable. It is expansion syntax for
11531 inserting the message header line with the given name. Note that the name must
11532 be terminated by colon or white space, because it may contain a wide variety of
11533 characters. Note also that braces must &'not'& be used.
11535 .vitem &$headers_added$&
11536 .vindex "&$headers_added$&"
11537 Within an ACL this variable contains the headers added so far by
11538 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
11539 The headers are a newline-separated list.
11543 When the &%check_local_user%& option is set for a router, the user's home
11544 directory is placed in &$home$& when the check succeeds. In particular, this
11545 means it is set during the running of users' filter files. A router may also
11546 explicitly set a home directory for use by a transport; this can be overridden
11547 by a setting on the transport itself.
11549 When running a filter test via the &%-bf%& option, &$home$& is set to the value
11550 of the environment variable HOME.
11554 If a router assigns an address to a transport (any transport), and passes a
11555 list of hosts with the address, the value of &$host$& when the transport starts
11556 to run is the name of the first host on the list. Note that this applies both
11557 to local and remote transports.
11559 .cindex "transport" "filter"
11560 .cindex "filter" "transport filter"
11561 For the &(smtp)& transport, if there is more than one host, the value of
11562 &$host$& changes as the transport works its way through the list. In
11563 particular, when the &(smtp)& transport is expanding its options for encryption
11564 using TLS, or for specifying a transport filter (see chapter
11565 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
11568 When used in the client part of an authenticator configuration (see chapter
11569 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
11570 client is connected.
11573 .vitem &$host_address$&
11574 .vindex "&$host_address$&"
11575 This variable is set to the remote host's IP address whenever &$host$& is set
11576 for a remote connection. It is also set to the IP address that is being checked
11577 when the &%ignore_target_hosts%& option is being processed.
11579 .vitem &$host_data$&
11580 .vindex "&$host_data$&"
11581 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
11582 result of the lookup is made available in the &$host_data$& variable. This
11583 allows you, for example, to do things like this:
11585 deny hosts = net-lsearch;/some/file
11586 message = $host_data
11588 .vitem &$host_lookup_deferred$&
11589 .cindex "host name" "lookup, failure of"
11590 .vindex "&$host_lookup_deferred$&"
11591 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
11592 message comes from a remote host and there is an attempt to look up the host's
11593 name from its IP address, and the attempt is not successful, one of these
11594 variables is set to &"1"&.
11597 If the lookup receives a definite negative response (for example, a DNS lookup
11598 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
11601 If there is any kind of problem during the lookup, such that Exim cannot
11602 tell whether or not the host name is defined (for example, a timeout for a DNS
11603 lookup), &$host_lookup_deferred$& is set to &"1"&.
11606 Looking up a host's name from its IP address consists of more than just a
11607 single reverse lookup. Exim checks that a forward lookup of at least one of the
11608 names it receives from a reverse lookup yields the original IP address. If this
11609 is not the case, Exim does not accept the looked up name(s), and
11610 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
11611 IP address (for example, the existence of a PTR record in the DNS) is not
11612 sufficient on its own for the success of a host name lookup. If the reverse
11613 lookup succeeds, but there is a lookup problem such as a timeout when checking
11614 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
11615 &"1"&. See also &$sender_host_name$&.
11617 .vitem &$host_lookup_failed$&
11618 .vindex "&$host_lookup_failed$&"
11619 See &$host_lookup_deferred$&.
11621 .vitem &$host_port$&
11622 .vindex "&$host_port$&"
11623 This variable is set to the remote host's TCP port whenever &$host$& is set
11624 for an outbound connection.
11628 .vindex "&$inode$&"
11629 The only time this variable is set is while expanding the &%directory_file%&
11630 option in the &(appendfile)& transport. The variable contains the inode number
11631 of the temporary file which is about to be renamed. It can be used to construct
11632 a unique name for the file.
11634 .vitem &$interface_address$&
11635 .vindex "&$interface_address$&"
11636 This is an obsolete name for &$received_ip_address$&.
11638 .vitem &$interface_port$&
11639 .vindex "&$interface_port$&"
11640 This is an obsolete name for &$received_port$&.
11644 This variable is used during the expansion of &*forall*& and &*forany*&
11645 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
11646 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
11650 .vindex "&$ldap_dn$&"
11651 This variable, which is available only when Exim is compiled with LDAP support,
11652 contains the DN from the last entry in the most recently successful LDAP
11655 .vitem &$load_average$&
11656 .vindex "&$load_average$&"
11657 This variable contains the system load average, multiplied by 1000 so that it
11658 is an integer. For example, if the load average is 0.21, the value of the
11659 variable is 210. The value is recomputed every time the variable is referenced.
11661 .vitem &$local_part$&
11662 .vindex "&$local_part$&"
11663 When an address is being routed, or delivered on its own, this
11664 variable contains the local part. When a number of addresses are being
11665 delivered together (for example, multiple RCPT commands in an SMTP
11666 session), &$local_part$& is not set.
11668 Global address rewriting happens when a message is received, so the value of
11669 &$local_part$& during routing and delivery is the value after rewriting.
11670 &$local_part$& is set during user filtering, but not during system filtering,
11671 because a message may have many recipients and the system filter is called just
11674 .vindex "&$local_part_prefix$&"
11675 .vindex "&$local_part_suffix$&"
11676 If a local part prefix or suffix has been recognized, it is not included in the
11677 value of &$local_part$& during routing and subsequent delivery. The values of
11678 any prefix or suffix are in &$local_part_prefix$& and
11679 &$local_part_suffix$&, respectively.
11681 When a message is being delivered to a file, pipe, or autoreply transport as a
11682 result of aliasing or forwarding, &$local_part$& is set to the local part of
11683 the parent address, not to the file name or command (see &$address_file$& and
11686 When an ACL is running for a RCPT command, &$local_part$& contains the
11687 local part of the recipient address.
11689 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
11690 &$local_part$& contains the local part of the address that is being rewritten;
11691 it can be used in the expansion of the replacement address, for example.
11693 In all cases, all quoting is removed from the local part. For example, for both
11696 "abc:xyz"@test.example
11697 abc\:xyz@test.example
11699 the value of &$local_part$& is
11703 If you use &$local_part$& to create another address, you should always wrap it
11704 inside a quoting operator. For example, in a &(redirect)& router you could
11707 data = ${quote_local_part:$local_part}@new.domain.example
11709 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
11710 to process local parts in a case-dependent manner in a router, you can set the
11711 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
11713 .vitem &$local_part_data$&
11714 .vindex "&$local_part_data$&"
11715 When the &%local_parts%& option on a router matches a local part by means of a
11716 lookup, the data read by the lookup is available during the running of the
11717 router as &$local_part_data$&. In addition, if the driver routes the address
11718 to a transport, the value is available in that transport. If the transport is
11719 handling multiple addresses, the value from the first address is used.
11721 &$local_part_data$& is also set when the &%local_parts%& condition in an ACL
11722 matches a local part by means of a lookup. The data read by the lookup is
11723 available during the rest of the ACL statement. In all other situations, this
11724 variable expands to nothing.
11726 .vitem &$local_part_prefix$&
11727 .vindex "&$local_part_prefix$&"
11728 When an address is being routed or delivered, and a
11729 specific prefix for the local part was recognized, it is available in this
11730 variable, having been removed from &$local_part$&.
11732 .vitem &$local_part_suffix$&
11733 .vindex "&$local_part_suffix$&"
11734 When an address is being routed or delivered, and a
11735 specific suffix for the local part was recognized, it is available in this
11736 variable, having been removed from &$local_part$&.
11738 .vitem &$local_scan_data$&
11739 .vindex "&$local_scan_data$&"
11740 This variable contains the text returned by the &[local_scan()]& function when
11741 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
11743 .vitem &$local_user_gid$&
11744 .vindex "&$local_user_gid$&"
11745 See &$local_user_uid$&.
11747 .vitem &$local_user_uid$&
11748 .vindex "&$local_user_uid$&"
11749 This variable and &$local_user_gid$& are set to the uid and gid after the
11750 &%check_local_user%& router precondition succeeds. This means that their values
11751 are available for the remaining preconditions (&%senders%&, &%require_files%&,
11752 and &%condition%&), for the &%address_data%& expansion, and for any
11753 router-specific expansions. At all other times, the values in these variables
11754 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
11756 .vitem &$localhost_number$&
11757 .vindex "&$localhost_number$&"
11758 This contains the expanded value of the
11759 &%localhost_number%& option. The expansion happens after the main options have
11762 .vitem &$log_inodes$&
11763 .vindex "&$log_inodes$&"
11764 The number of free inodes in the disk partition where Exim's
11765 log files are being written. The value is recalculated whenever the variable is
11766 referenced. If the relevant file system does not have the concept of inodes,
11767 the value of is -1. See also the &%check_log_inodes%& option.
11769 .vitem &$log_space$&
11770 .vindex "&$log_space$&"
11771 The amount of free space (as a number of kilobytes) in the disk
11772 partition where Exim's log files are being written. The value is recalculated
11773 whenever the variable is referenced. If the operating system does not have the
11774 ability to find the amount of free space (only true for experimental systems),
11775 the space value is -1. See also the &%check_log_space%& option.
11778 .vitem &$lookup_dnssec_authenticated$&
11779 .vindex "&$lookup_dnssec_authenticated$&"
11780 This variable is set after a DNS lookup done by
11781 a dnsdb lookup expansion, dnslookup router or smtp transport.
11782 .cindex "DNS" "DNSSEC"
11783 It will be empty if &(DNSSEC)& was not requested,
11784 &"no"& if the result was not labelled as authenticated data
11785 and &"yes"& if it was.
11786 Results that are labelled as authoritative answer that match
11787 the &%dns_trust_aa%& configuration variable count also
11788 as authenticated data.
11790 .vitem &$mailstore_basename$&
11791 .vindex "&$mailstore_basename$&"
11792 This variable is set only when doing deliveries in &"mailstore"& format in the
11793 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
11794 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
11795 contains the basename of the files that are being written, that is, the name
11796 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
11799 .vitem &$malware_name$&
11800 .vindex "&$malware_name$&"
11801 This variable is available when Exim is compiled with the
11802 content-scanning extension. It is set to the name of the virus that was found
11803 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
11805 .vitem &$max_received_linelength$&
11806 .vindex "&$max_received_linelength$&"
11807 .cindex "maximum" "line length"
11808 .cindex "line length" "maximum"
11809 This variable contains the number of bytes in the longest line that was
11810 received as part of the message, not counting the line termination
11813 .vitem &$message_age$&
11814 .cindex "message" "age of"
11815 .vindex "&$message_age$&"
11816 This variable is set at the start of a delivery attempt to contain the number
11817 of seconds since the message was received. It does not change during a single
11820 .vitem &$message_body$&
11821 .cindex "body of message" "expansion variable"
11822 .cindex "message body" "in expansion"
11823 .cindex "binary zero" "in message body"
11824 .vindex "&$message_body$&"
11825 .oindex "&%message_body_visible%&"
11826 This variable contains the initial portion of a message's body while it is
11827 being delivered, and is intended mainly for use in filter files. The maximum
11828 number of characters of the body that are put into the variable is set by the
11829 &%message_body_visible%& configuration option; the default is 500.
11831 .oindex "&%message_body_newlines%&"
11832 By default, newlines are converted into spaces in &$message_body$&, to make it
11833 easier to search for phrases that might be split over a line break. However,
11834 this can be disabled by setting &%message_body_newlines%& to be true. Binary
11835 zeros are always converted into spaces.
11837 .vitem &$message_body_end$&
11838 .cindex "body of message" "expansion variable"
11839 .cindex "message body" "in expansion"
11840 .vindex "&$message_body_end$&"
11841 This variable contains the final portion of a message's
11842 body while it is being delivered. The format and maximum size are as for
11845 .vitem &$message_body_size$&
11846 .cindex "body of message" "size"
11847 .cindex "message body" "size"
11848 .vindex "&$message_body_size$&"
11849 When a message is being delivered, this variable contains the size of the body
11850 in bytes. The count starts from the character after the blank line that
11851 separates the body from the header. Newlines are included in the count. See
11852 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
11854 .vitem &$message_exim_id$&
11855 .vindex "&$message_exim_id$&"
11856 When a message is being received or delivered, this variable contains the
11857 unique message id that is generated and used by Exim to identify the message.
11858 An id is not created for a message until after its header has been successfully
11859 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
11860 line; it is the local id that Exim assigns to the message, for example:
11861 &`1BXTIK-0001yO-VA`&.
11863 .vitem &$message_headers$&
11864 .vindex &$message_headers$&
11865 This variable contains a concatenation of all the header lines when a message
11866 is being processed, except for lines added by routers or transports. The header
11867 lines are separated by newline characters. Their contents are decoded in the
11868 same way as a header line that is inserted by &%bheader%&.
11870 .vitem &$message_headers_raw$&
11871 .vindex &$message_headers_raw$&
11872 This variable is like &$message_headers$& except that no processing of the
11873 contents of header lines is done.
11875 .vitem &$message_id$&
11876 This is an old name for &$message_exim_id$&. It is now deprecated.
11878 .vitem &$message_linecount$&
11879 .vindex "&$message_linecount$&"
11880 This variable contains the total number of lines in the header and body of the
11881 message. Compare &$body_linecount$&, which is the count for the body only.
11882 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
11883 number of lines received. Before delivery happens (that is, before filters,
11884 routers, and transports run) the count is increased to include the
11885 &'Received:'& header line that Exim standardly adds, and also any other header
11886 lines that are added by ACLs. The blank line that separates the message header
11887 from the body is not counted.
11889 As with the special case of &$message_size$&, during the expansion of the
11890 appendfile transport's maildir_tag option in maildir format, the value of
11891 &$message_linecount$& is the precise size of the number of newlines in the
11892 file that has been written (minus one for the blank line between the
11893 header and the body).
11895 Here is an example of the use of this variable in a DATA ACL:
11897 deny message = Too many lines in message header
11899 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
11901 In the MAIL and RCPT ACLs, the value is zero because at that stage the
11902 message has not yet been received.
11904 .vitem &$message_size$&
11905 .cindex "size" "of message"
11906 .cindex "message" "size"
11907 .vindex "&$message_size$&"
11908 When a message is being processed, this variable contains its size in bytes. In
11909 most cases, the size includes those headers that were received with the
11910 message, but not those (such as &'Envelope-to:'&) that are added to individual
11911 deliveries as they are written. However, there is one special case: during the
11912 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
11913 doing a delivery in maildir format, the value of &$message_size$& is the
11914 precise size of the file that has been written. See also
11915 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
11917 .cindex "RCPT" "value of &$message_size$&"
11918 While running a per message ACL (mail/rcpt/predata), &$message_size$&
11919 contains the size supplied on the MAIL command, or -1 if no size was given. The
11920 value may not, of course, be truthful.
11922 .vitem &$mime_$&&'xxx'&
11923 A number of variables whose names start with &$mime$& are
11924 available when Exim is compiled with the content-scanning extension. For
11925 details, see section &<<SECTscanmimepart>>&.
11927 .vitem "&$n0$& &-- &$n9$&"
11928 These variables are counters that can be incremented by means
11929 of the &%add%& command in filter files.
11931 .vitem &$original_domain$&
11932 .vindex "&$domain$&"
11933 .vindex "&$original_domain$&"
11934 When a top-level address is being processed for delivery, this contains the
11935 same value as &$domain$&. However, if a &"child"& address (for example,
11936 generated by an alias, forward, or filter file) is being processed, this
11937 variable contains the domain of the original address (lower cased). This
11938 differs from &$parent_domain$& only when there is more than one level of
11939 aliasing or forwarding. When more than one address is being delivered in a
11940 single transport run, &$original_domain$& is not set.
11942 If a new address is created by means of a &%deliver%& command in a system
11943 filter, it is set up with an artificial &"parent"& address. This has the local
11944 part &'system-filter'& and the default qualify domain.
11946 .vitem &$original_local_part$&
11947 .vindex "&$local_part$&"
11948 .vindex "&$original_local_part$&"
11949 When a top-level address is being processed for delivery, this contains the
11950 same value as &$local_part$&, unless a prefix or suffix was removed from the
11951 local part, because &$original_local_part$& always contains the full local
11952 part. When a &"child"& address (for example, generated by an alias, forward, or
11953 filter file) is being processed, this variable contains the full local part of
11954 the original address.
11956 If the router that did the redirection processed the local part
11957 case-insensitively, the value in &$original_local_part$& is in lower case.
11958 This variable differs from &$parent_local_part$& only when there is more than
11959 one level of aliasing or forwarding. When more than one address is being
11960 delivered in a single transport run, &$original_local_part$& is not set.
11962 If a new address is created by means of a &%deliver%& command in a system
11963 filter, it is set up with an artificial &"parent"& address. This has the local
11964 part &'system-filter'& and the default qualify domain.
11966 .vitem &$originator_gid$&
11967 .cindex "gid (group id)" "of originating user"
11968 .cindex "sender" "gid"
11969 .vindex "&$caller_gid$&"
11970 .vindex "&$originator_gid$&"
11971 This variable contains the value of &$caller_gid$& that was set when the
11972 message was received. For messages received via the command line, this is the
11973 gid of the sending user. For messages received by SMTP over TCP/IP, this is
11974 normally the gid of the Exim user.
11976 .vitem &$originator_uid$&
11977 .cindex "uid (user id)" "of originating user"
11978 .cindex "sender" "uid"
11979 .vindex "&$caller_uid$&"
11980 .vindex "&$originaltor_uid$&"
11981 The value of &$caller_uid$& that was set when the message was received. For
11982 messages received via the command line, this is the uid of the sending user.
11983 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
11986 .vitem &$parent_domain$&
11987 .vindex "&$parent_domain$&"
11988 This variable is similar to &$original_domain$& (see
11989 above), except that it refers to the immediately preceding parent address.
11991 .vitem &$parent_local_part$&
11992 .vindex "&$parent_local_part$&"
11993 This variable is similar to &$original_local_part$&
11994 (see above), except that it refers to the immediately preceding parent address.
11997 .cindex "pid (process id)" "of current process"
11999 This variable contains the current process id.
12001 .vitem &$pipe_addresses$&
12002 .cindex "filter" "transport filter"
12003 .cindex "transport" "filter"
12004 .vindex "&$pipe_addresses$&"
12005 This is not an expansion variable, but is mentioned here because the string
12006 &`$pipe_addresses`& is handled specially in the command specification for the
12007 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
12008 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
12009 It cannot be used in general expansion strings, and provokes an &"unknown
12010 variable"& error if encountered.
12012 .vitem &$primary_hostname$&
12013 .vindex "&$primary_hostname$&"
12014 This variable contains the value set by &%primary_hostname%& in the
12015 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
12016 a single-component name, Exim calls &[gethostbyname()]& (or
12017 &[getipnodebyname()]& where available) in an attempt to acquire a fully
12018 qualified host name. See also &$smtp_active_hostname$&.
12022 .vitem &$prdr_requested$&
12023 .cindex "PRDR" "variable for"
12024 This variable is set to &"yes"& if PRDR was requested by the client for the
12025 current message, otherwise &"no"&.
12028 .vitem &$prvscheck_address$&
12029 This variable is used in conjunction with the &%prvscheck%& expansion item,
12030 which is described in sections &<<SECTexpansionitems>>& and
12031 &<<SECTverifyPRVS>>&.
12033 .vitem &$prvscheck_keynum$&
12034 This variable is used in conjunction with the &%prvscheck%& expansion item,
12035 which is described in sections &<<SECTexpansionitems>>& and
12036 &<<SECTverifyPRVS>>&.
12038 .vitem &$prvscheck_result$&
12039 This variable is used in conjunction with the &%prvscheck%& expansion item,
12040 which is described in sections &<<SECTexpansionitems>>& and
12041 &<<SECTverifyPRVS>>&.
12043 .vitem &$qualify_domain$&
12044 .vindex "&$qualify_domain$&"
12045 The value set for the &%qualify_domain%& option in the configuration file.
12047 .vitem &$qualify_recipient$&
12048 .vindex "&$qualify_recipient$&"
12049 The value set for the &%qualify_recipient%& option in the configuration file,
12050 or if not set, the value of &$qualify_domain$&.
12052 .vitem &$rcpt_count$&
12053 .vindex "&$rcpt_count$&"
12054 When a message is being received by SMTP, this variable contains the number of
12055 RCPT commands received for the current message. If this variable is used in a
12056 RCPT ACL, its value includes the current command.
12058 .vitem &$rcpt_defer_count$&
12059 .vindex "&$rcpt_defer_count$&"
12060 .cindex "4&'xx'& responses" "count of"
12061 When a message is being received by SMTP, this variable contains the number of
12062 RCPT commands in the current message that have previously been rejected with a
12063 temporary (4&'xx'&) response.
12065 .vitem &$rcpt_fail_count$&
12066 .vindex "&$rcpt_fail_count$&"
12067 When a message is being received by SMTP, this variable contains the number of
12068 RCPT commands in the current message that have previously been rejected with a
12069 permanent (5&'xx'&) response.
12071 .vitem &$received_count$&
12072 .vindex "&$received_count$&"
12073 This variable contains the number of &'Received:'& header lines in the message,
12074 including the one added by Exim (so its value is always greater than zero). It
12075 is available in the DATA ACL, the non-SMTP ACL, and while routing and
12078 .vitem &$received_for$&
12079 .vindex "&$received_for$&"
12080 If there is only a single recipient address in an incoming message, this
12081 variable contains that address when the &'Received:'& header line is being
12082 built. The value is copied after recipient rewriting has happened, but before
12083 the &[local_scan()]& function is run.
12085 .vitem &$received_ip_address$&
12086 .vindex "&$received_ip_address$&"
12087 As soon as an Exim server starts processing an incoming TCP/IP connection, this
12088 variable is set to the address of the local IP interface, and &$received_port$&
12089 is set to the local port number. (The remote IP address and port are in
12090 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
12091 the port value is -1 unless it has been set using the &%-oMi%& command line
12094 As well as being useful in ACLs (including the &"connect"& ACL), these variable
12095 could be used, for example, to make the file name for a TLS certificate depend
12096 on which interface and/or port is being used for the incoming connection. The
12097 values of &$received_ip_address$& and &$received_port$& are saved with any
12098 messages that are received, thus making these variables available at delivery
12100 For outbound connections see &$sending_ip_address$&.
12102 .vitem &$received_port$&
12103 .vindex "&$received_port$&"
12104 See &$received_ip_address$&.
12106 .vitem &$received_protocol$&
12107 .vindex "&$received_protocol$&"
12108 When a message is being processed, this variable contains the name of the
12109 protocol by which it was received. Most of the names used by Exim are defined
12110 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
12111 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
12112 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
12113 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
12114 connection and the client was successfully authenticated.
12116 Exim uses the protocol name &"smtps"& for the case when encryption is
12117 automatically set up on connection without the use of STARTTLS (see
12118 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
12119 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
12120 where the client initially uses EHLO, sets up an encrypted connection using
12121 STARTTLS, and then uses HELO afterwards.
12123 The &%-oMr%& option provides a way of specifying a custom protocol name for
12124 messages that are injected locally by trusted callers. This is commonly used to
12125 identify messages that are being re-injected after some kind of scanning.
12127 .vitem &$received_time$&
12128 .vindex "&$received_time$&"
12129 This variable contains the date and time when the current message was received,
12130 as a number of seconds since the start of the Unix epoch.
12132 .vitem &$recipient_data$&
12133 .vindex "&$recipient_data$&"
12134 This variable is set after an indexing lookup success in an ACL &%recipients%&
12135 condition. It contains the data from the lookup, and the value remains set
12136 until the next &%recipients%& test. Thus, you can do things like this:
12138 &`require recipients = cdb*@;/some/file`&
12139 &`deny `&&'some further test involving'& &`$recipient_data`&
12141 &*Warning*&: This variable is set only when a lookup is used as an indexing
12142 method in the address list, using the semicolon syntax as in the example above.
12143 The variable is not set for a lookup that is used as part of the string
12144 expansion that all such lists undergo before being interpreted.
12146 .vitem &$recipient_verify_failure$&
12147 .vindex "&$recipient_verify_failure$&"
12148 In an ACL, when a recipient verification fails, this variable contains
12149 information about the failure. It is set to one of the following words:
12152 &"qualify"&: The address was unqualified (no domain), and the message
12153 was neither local nor came from an exempted host.
12156 &"route"&: Routing failed.
12159 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
12160 or before the MAIL command (that is, on initial connection, HELO, or
12164 &"recipient"&: The RCPT command in a callout was rejected.
12167 &"postmaster"&: The postmaster check in a callout was rejected.
12170 The main use of this variable is expected to be to distinguish between
12171 rejections of MAIL and rejections of RCPT.
12173 .vitem &$recipients$&
12174 .vindex "&$recipients$&"
12175 This variable contains a list of envelope recipients for a message. A comma and
12176 a space separate the addresses in the replacement text. However, the variable
12177 is not generally available, to prevent exposure of Bcc recipients in
12178 unprivileged users' filter files. You can use &$recipients$& only in these
12182 In a system filter file.
12184 In the ACLs associated with the DATA command and with non-SMTP messages, that
12185 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
12186 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
12187 &%acl_not_smtp_mime%&.
12189 From within a &[local_scan()]& function.
12193 .vitem &$recipients_count$&
12194 .vindex "&$recipients_count$&"
12195 When a message is being processed, this variable contains the number of
12196 envelope recipients that came with the message. Duplicates are not excluded
12197 from the count. While a message is being received over SMTP, the number
12198 increases for each accepted recipient. It can be referenced in an ACL.
12201 .vitem &$regex_match_string$&
12202 .vindex "&$regex_match_string$&"
12203 This variable is set to contain the matching regular expression after a
12204 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
12206 .vitem "&$regex1$&, &$regex2$&, etc"
12207 .cindex "regex submatch variables (&$1regex$& &$2regex$& etc)"
12208 When a &%regex%& or &%mime_regex%& ACL condition succeeds,
12209 these variables contain the
12210 captured substrings identified by the regular expression.
12213 .vitem &$reply_address$&
12214 .vindex "&$reply_address$&"
12215 When a message is being processed, this variable contains the contents of the
12216 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
12217 contents of the &'From:'& header line. Apart from the removal of leading
12218 white space, the value is not processed in any way. In particular, no RFC 2047
12219 decoding or character code translation takes place.
12221 .vitem &$return_path$&
12222 .vindex "&$return_path$&"
12223 When a message is being delivered, this variable contains the return path &--
12224 the sender field that will be sent as part of the envelope. It is not enclosed
12225 in <> characters. At the start of routing an address, &$return_path$& has the
12226 same value as &$sender_address$&, but if, for example, an incoming message to a
12227 mailing list has been expanded by a router which specifies a different address
12228 for bounce messages, &$return_path$& subsequently contains the new bounce
12229 address, whereas &$sender_address$& always contains the original sender address
12230 that was received with the message. In other words, &$sender_address$& contains
12231 the incoming envelope sender, and &$return_path$& contains the outgoing
12234 .vitem &$return_size_limit$&
12235 .vindex "&$return_size_limit$&"
12236 This is an obsolete name for &$bounce_return_size_limit$&.
12238 .vitem &$router_name$&
12239 .cindex "router" "name"
12240 .cindex "name" "of router"
12241 .vindex "&$router_name$&"
12242 During the running of a router this variable contains its name.
12245 .cindex "return code" "from &%run%& expansion"
12246 .vindex "&$runrc$&"
12247 This variable contains the return code from a command that is run by the
12248 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
12249 assume the order in which option values are expanded, except for those
12250 preconditions whose order of testing is documented. Therefore, you cannot
12251 reliably expect to set &$runrc$& by the expansion of one option, and use it in
12254 .vitem &$self_hostname$&
12255 .oindex "&%self%&" "value of host name"
12256 .vindex "&$self_hostname$&"
12257 When an address is routed to a supposedly remote host that turns out to be the
12258 local host, what happens is controlled by the &%self%& generic router option.
12259 One of its values causes the address to be passed to another router. When this
12260 happens, &$self_hostname$& is set to the name of the local host that the
12261 original router encountered. In other circumstances its contents are null.
12263 .vitem &$sender_address$&
12264 .vindex "&$sender_address$&"
12265 When a message is being processed, this variable contains the sender's address
12266 that was received in the message's envelope. The case of letters in the address
12267 is retained, in both the local part and the domain. For bounce messages, the
12268 value of this variable is the empty string. See also &$return_path$&.
12270 .vitem &$sender_address_data$&
12271 .vindex "&$address_data$&"
12272 .vindex "&$sender_address_data$&"
12273 If &$address_data$& is set when the routers are called from an ACL to verify a
12274 sender address, the final value is preserved in &$sender_address_data$&, to
12275 distinguish it from data from a recipient address. The value does not persist
12276 after the end of the current ACL statement. If you want to preserve it for
12277 longer, you can save it in an ACL variable.
12279 .vitem &$sender_address_domain$&
12280 .vindex "&$sender_address_domain$&"
12281 The domain portion of &$sender_address$&.
12283 .vitem &$sender_address_local_part$&
12284 .vindex "&$sender_address_local_part$&"
12285 The local part portion of &$sender_address$&.
12287 .vitem &$sender_data$&
12288 .vindex "&$sender_data$&"
12289 This variable is set after a lookup success in an ACL &%senders%& condition or
12290 in a router &%senders%& option. It contains the data from the lookup, and the
12291 value remains set until the next &%senders%& test. Thus, you can do things like
12294 &`require senders = cdb*@;/some/file`&
12295 &`deny `&&'some further test involving'& &`$sender_data`&
12297 &*Warning*&: This variable is set only when a lookup is used as an indexing
12298 method in the address list, using the semicolon syntax as in the example above.
12299 The variable is not set for a lookup that is used as part of the string
12300 expansion that all such lists undergo before being interpreted.
12302 .vitem &$sender_fullhost$&
12303 .vindex "&$sender_fullhost$&"
12304 When a message is received from a remote host, this variable contains the host
12305 name and IP address in a single string. It ends with the IP address in square
12306 brackets, followed by a colon and a port number if the logging of ports is
12307 enabled. The format of the rest of the string depends on whether the host
12308 issued a HELO or EHLO SMTP command, and whether the host name was verified by
12309 looking up its IP address. (Looking up the IP address can be forced by the
12310 &%host_lookup%& option, independent of verification.) A plain host name at the
12311 start of the string is a verified host name; if this is not present,
12312 verification either failed or was not requested. A host name in parentheses is
12313 the argument of a HELO or EHLO command. This is omitted if it is identical to
12314 the verified host name or to the host's IP address in square brackets.
12316 .vitem &$sender_helo_dnssec$&
12317 .vindex "&$sender_helo_dnssec$&"
12318 This boolean variable is true if a successful HELO verification was
12319 .cindex "DNS" "DNSSEC"
12320 done using DNS information the resolver library stated was authenticated data.
12322 .vitem &$sender_helo_name$&
12323 .vindex "&$sender_helo_name$&"
12324 When a message is received from a remote host that has issued a HELO or EHLO
12325 command, the argument of that command is placed in this variable. It is also
12326 set if HELO or EHLO is used when a message is received using SMTP locally via
12327 the &%-bs%& or &%-bS%& options.
12329 .vitem &$sender_host_address$&
12330 .vindex "&$sender_host_address$&"
12331 When a message is received from a remote host using SMTP,
12332 this variable contains that
12333 host's IP address. For locally non-SMTP submitted messages, it is empty.
12335 .vitem &$sender_host_authenticated$&
12336 .vindex "&$sender_host_authenticated$&"
12337 This variable contains the name (not the public name) of the authenticator
12338 driver that successfully authenticated the client from which the message was
12339 received. It is empty if there was no successful authentication. See also
12340 &$authenticated_id$&.
12342 .vitem &$sender_host_dnssec$&
12343 .vindex "&$sender_host_dnssec$&"
12344 If an attempt to populate &$sender_host_name$& has been made
12345 (by reference, &%hosts_lookup%& or
12346 otherwise) then this boolean will have been set true if, and only if, the
12347 resolver library states that both
12348 the reverse and forward DNS were authenticated data. At all
12349 other times, this variable is false.
12351 .cindex "DNS" "DNSSEC"
12352 It is likely that you will need to coerce DNSSEC support on in the resolver
12353 library, by setting:
12358 Exim does not perform DNSSEC validation itself, instead leaving that to a
12359 validating resolver (e.g. unbound, or bind with suitable configuration).
12361 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
12362 mechanism in the list, then this variable will be false.
12365 .vitem &$sender_host_name$&
12366 .vindex "&$sender_host_name$&"
12367 When a message is received from a remote host, this variable contains the
12368 host's name as obtained by looking up its IP address. For messages received by
12369 other means, this variable is empty.
12371 .vindex "&$host_lookup_failed$&"
12372 If the host name has not previously been looked up, a reference to
12373 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
12374 A looked up name is accepted only if it leads back to the original IP address
12375 via a forward lookup. If either the reverse or the forward lookup fails to find
12376 any data, or if the forward lookup does not yield the original IP address,
12377 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
12379 .vindex "&$host_lookup_deferred$&"
12380 However, if either of the lookups cannot be completed (for example, there is a
12381 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
12382 &$host_lookup_failed$& remains set to &"0"&.
12384 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
12385 host name again if there is a subsequent reference to &$sender_host_name$&
12386 in the same Exim process, but it does try again if &$host_lookup_deferred$&
12389 Exim does not automatically look up every calling host's name. If you want
12390 maximum efficiency, you should arrange your configuration so that it avoids
12391 these lookups altogether. The lookup happens only if one or more of the
12392 following are true:
12395 A string containing &$sender_host_name$& is expanded.
12397 The calling host matches the list in &%host_lookup%&. In the default
12398 configuration, this option is set to *, so it must be changed if lookups are
12399 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
12401 Exim needs the host name in order to test an item in a host list. The items
12402 that require this are described in sections &<<SECThoslispatnam>>& and
12403 &<<SECThoslispatnamsk>>&.
12405 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
12406 In this case, the host name is required to compare with the name quoted in any
12407 EHLO or HELO commands that the client issues.
12409 The remote host issues a EHLO or HELO command that quotes one of the
12410 domains in &%helo_lookup_domains%&. The default value of this option is
12411 . ==== As this is a nested list, any displays it contains must be indented
12412 . ==== as otherwise they are too far to the left.
12414 helo_lookup_domains = @ : @[]
12416 which causes a lookup if a remote host (incorrectly) gives the server's name or
12417 IP address in an EHLO or HELO command.
12421 .vitem &$sender_host_port$&
12422 .vindex "&$sender_host_port$&"
12423 When a message is received from a remote host, this variable contains the port
12424 number that was used on the remote host.
12426 .vitem &$sender_ident$&
12427 .vindex "&$sender_ident$&"
12428 When a message is received from a remote host, this variable contains the
12429 identification received in response to an RFC 1413 request. When a message has
12430 been received locally, this variable contains the login name of the user that
12433 .vitem &$sender_rate_$&&'xxx'&
12434 A number of variables whose names begin &$sender_rate_$& are set as part of the
12435 &%ratelimit%& ACL condition. Details are given in section
12436 &<<SECTratelimiting>>&.
12438 .vitem &$sender_rcvhost$&
12439 .cindex "DNS" "reverse lookup"
12440 .cindex "reverse DNS lookup"
12441 .vindex "&$sender_rcvhost$&"
12442 This is provided specifically for use in &'Received:'& headers. It starts with
12443 either the verified host name (as obtained from a reverse DNS lookup) or, if
12444 there is no verified host name, the IP address in square brackets. After that
12445 there may be text in parentheses. When the first item is a verified host name,
12446 the first thing in the parentheses is the IP address in square brackets,
12447 followed by a colon and a port number if port logging is enabled. When the
12448 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
12451 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
12452 was used and its argument was not identical to the real host name or IP
12453 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
12454 all three items are present in the parentheses, a newline and tab are inserted
12455 into the string, to improve the formatting of the &'Received:'& header.
12457 .vitem &$sender_verify_failure$&
12458 .vindex "&$sender_verify_failure$&"
12459 In an ACL, when a sender verification fails, this variable contains information
12460 about the failure. The details are the same as for
12461 &$recipient_verify_failure$&.
12463 .vitem &$sending_ip_address$&
12464 .vindex "&$sending_ip_address$&"
12465 This variable is set whenever an outgoing SMTP connection to another host has
12466 been set up. It contains the IP address of the local interface that is being
12467 used. This is useful if a host that has more than one IP address wants to take
12468 on different personalities depending on which one is being used. For incoming
12469 connections, see &$received_ip_address$&.
12471 .vitem &$sending_port$&
12472 .vindex "&$sending_port$&"
12473 This variable is set whenever an outgoing SMTP connection to another host has
12474 been set up. It contains the local port that is being used. For incoming
12475 connections, see &$received_port$&.
12477 .vitem &$smtp_active_hostname$&
12478 .vindex "&$smtp_active_hostname$&"
12479 During an incoming SMTP session, this variable contains the value of the active
12480 host name, as specified by the &%smtp_active_hostname%& option. The value of
12481 &$smtp_active_hostname$& is saved with any message that is received, so its
12482 value can be consulted during routing and delivery.
12484 .vitem &$smtp_command$&
12485 .vindex "&$smtp_command$&"
12486 During the processing of an incoming SMTP command, this variable contains the
12487 entire command. This makes it possible to distinguish between HELO and EHLO in
12488 the HELO ACL, and also to distinguish between commands such as these:
12493 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
12494 command, the address in &$smtp_command$& is the original address before any
12495 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
12496 the address after SMTP-time rewriting.
12498 .vitem &$smtp_command_argument$&
12499 .cindex "SMTP" "command, argument for"
12500 .vindex "&$smtp_command_argument$&"
12501 While an ACL is running to check an SMTP command, this variable contains the
12502 argument, that is, the text that follows the command name, with leading white
12503 space removed. Following the introduction of &$smtp_command$&, this variable is
12504 somewhat redundant, but is retained for backwards compatibility.
12506 .vitem &$smtp_count_at_connection_start$&
12507 .vindex "&$smtp_count_at_connection_start$&"
12508 This variable is set greater than zero only in processes spawned by the Exim
12509 daemon for handling incoming SMTP connections. The name is deliberately long,
12510 in order to emphasize what the contents are. When the daemon accepts a new
12511 connection, it increments this variable. A copy of the variable is passed to
12512 the child process that handles the connection, but its value is fixed, and
12513 never changes. It is only an approximation of how many incoming connections
12514 there actually are, because many other connections may come and go while a
12515 single connection is being processed. When a child process terminates, the
12516 daemon decrements its copy of the variable.
12518 .vitem "&$sn0$& &-- &$sn9$&"
12519 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
12520 that were current at the end of the system filter file. This allows a system
12521 filter file to set values that can be tested in users' filter files. For
12522 example, a system filter could set a value indicating how likely it is that a
12523 message is junk mail.
12525 .vitem &$spam_$&&'xxx'&
12526 A number of variables whose names start with &$spam$& are available when Exim
12527 is compiled with the content-scanning extension. For details, see section
12528 &<<SECTscanspamass>>&.
12531 .vitem &$spool_directory$&
12532 .vindex "&$spool_directory$&"
12533 The name of Exim's spool directory.
12535 .vitem &$spool_inodes$&
12536 .vindex "&$spool_inodes$&"
12537 The number of free inodes in the disk partition where Exim's spool files are
12538 being written. The value is recalculated whenever the variable is referenced.
12539 If the relevant file system does not have the concept of inodes, the value of
12540 is -1. See also the &%check_spool_inodes%& option.
12542 .vitem &$spool_space$&
12543 .vindex "&$spool_space$&"
12544 The amount of free space (as a number of kilobytes) in the disk partition where
12545 Exim's spool files are being written. The value is recalculated whenever the
12546 variable is referenced. If the operating system does not have the ability to
12547 find the amount of free space (only true for experimental systems), the space
12548 value is -1. For example, to check in an ACL that there is at least 50
12549 megabytes free on the spool, you could write:
12551 condition = ${if > {$spool_space}{50000}}
12553 See also the &%check_spool_space%& option.
12556 .vitem &$thisaddress$&
12557 .vindex "&$thisaddress$&"
12558 This variable is set only during the processing of the &%foranyaddress%&
12559 command in a filter file. Its use is explained in the description of that
12560 command, which can be found in the separate document entitled &'Exim's
12561 interfaces to mail filtering'&.
12563 .vitem &$tls_in_bits$&
12564 .vindex "&$tls_in_bits$&"
12565 Contains an approximation of the TLS cipher's bit-strength
12566 on the inbound connection; the meaning of
12567 this depends upon the TLS implementation used.
12568 If TLS has not been negotiated, the value will be 0.
12569 The value of this is automatically fed into the Cyrus SASL authenticator
12570 when acting as a server, to specify the "external SSF" (a SASL term).
12572 The deprecated &$tls_bits$& variable refers to the inbound side
12573 except when used in the context of an outbound SMTP delivery, when it refers to
12576 .vitem &$tls_out_bits$&
12577 .vindex "&$tls_out_bits$&"
12578 Contains an approximation of the TLS cipher's bit-strength
12579 on an outbound SMTP connection; the meaning of
12580 this depends upon the TLS implementation used.
12581 If TLS has not been negotiated, the value will be 0.
12583 .vitem &$tls_in_ourcert$&
12584 .vindex "&$tls_in_ourcert$&"
12585 This variable refers to the certificate presented to the peer of an
12586 inbound connection when the message was received.
12587 It is only useful as the argument of a
12588 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12589 or a &%def%& condition.
12591 .vitem &$tls_in_peercert$&
12592 .vindex "&$tls_in_peercert$&"
12593 This variable refers to the certificate presented by the peer of an
12594 inbound connection when the message was received.
12595 It is only useful as the argument of a
12596 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12597 or a &%def%& condition.
12598 If certificate verification fails it may refer to a failing chain element
12599 which is not the leaf.
12601 .vitem &$tls_out_ourcert$&
12602 .vindex "&$tls_out_ourcert$&"
12603 This variable refers to the certificate presented to the peer of an
12604 outbound connection. It is only useful as the argument of a
12605 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12606 or a &%def%& condition.
12608 .vitem &$tls_out_peercert$&
12609 .vindex "&$tls_out_peercert$&"
12610 This variable refers to the certificate presented by the peer of an
12611 outbound connection. It is only useful as the argument of a
12612 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12613 or a &%def%& condition.
12614 If certificate verification fails it may refer to a failing chain element
12615 which is not the leaf.
12617 .vitem &$tls_in_certificate_verified$&
12618 .vindex "&$tls_in_certificate_verified$&"
12619 This variable is set to &"1"& if a TLS certificate was verified when the
12620 message was received, and &"0"& otherwise.
12622 The deprecated &$tls_certificate_verified$& variable refers to the inbound side
12623 except when used in the context of an outbound SMTP delivery, when it refers to
12626 .vitem &$tls_out_certificate_verified$&
12627 .vindex "&$tls_out_certificate_verified$&"
12628 This variable is set to &"1"& if a TLS certificate was verified when an
12629 outbound SMTP connection was made,
12630 and &"0"& otherwise.
12632 .vitem &$tls_in_cipher$&
12633 .vindex "&$tls_in_cipher$&"
12634 .vindex "&$tls_cipher$&"
12635 When a message is received from a remote host over an encrypted SMTP
12636 connection, this variable is set to the cipher suite that was negotiated, for
12637 example DES-CBC3-SHA. In other circumstances, in particular, for message
12638 received over unencrypted connections, the variable is empty. Testing
12639 &$tls_cipher$& for emptiness is one way of distinguishing between encrypted and
12640 non-encrypted connections during ACL processing.
12642 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
12643 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
12644 becomes the same as &$tls_out_cipher$&.
12646 .vitem &$tls_out_cipher$&
12647 .vindex "&$tls_out_cipher$&"
12649 cleared before any outgoing SMTP connection is made,
12650 and then set to the outgoing cipher suite if one is negotiated. See chapter
12651 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
12652 details of the &(smtp)& transport.
12654 .vitem &$tls_in_ocsp$&
12655 .vindex "&$tls_in_ocsp$&"
12656 When a message is received from a remote client connection
12657 the result of any OCSP request from the client is encoded in this variable:
12659 0 OCSP proof was not requested (default value)
12660 1 No response to request
12661 2 Response not verified
12662 3 Verification failed
12663 4 Verification succeeded
12666 .vitem &$tls_out_ocsp$&
12667 .vindex "&$tls_out_ocsp$&"
12668 When a message is sent to a remote host connection
12669 the result of any OCSP request made is encoded in this variable.
12670 See &$tls_in_ocsp$& for values.
12672 .vitem &$tls_in_peerdn$&
12673 .vindex "&$tls_in_peerdn$&"
12674 .vindex "&$tls_peerdn$&"
12675 When a message is received from a remote host over an encrypted SMTP
12676 connection, and Exim is configured to request a certificate from the client,
12677 the value of the Distinguished Name of the certificate is made available in the
12678 &$tls_in_peerdn$& during subsequent processing.
12679 If certificate verification fails it may refer to a failing chain element
12680 which is not the leaf.
12682 The deprecated &$tls_peerdn$& variable refers to the inbound side
12683 except when used in the context of an outbound SMTP delivery, when it refers to
12686 .vitem &$tls_out_peerdn$&
12687 .vindex "&$tls_out_peerdn$&"
12688 When a message is being delivered to a remote host over an encrypted SMTP
12689 connection, and Exim is configured to request a certificate from the server,
12690 the value of the Distinguished Name of the certificate is made available in the
12691 &$tls_out_peerdn$& during subsequent processing.
12692 If certificate verification fails it may refer to a failing chain element
12693 which is not the leaf.
12695 .vitem &$tls_in_sni$&
12696 .vindex "&$tls_in_sni$&"
12697 .vindex "&$tls_sni$&"
12698 .cindex "TLS" "Server Name Indication"
12699 When a TLS session is being established, if the client sends the Server
12700 Name Indication extension, the value will be placed in this variable.
12701 If the variable appears in &%tls_certificate%& then this option and
12702 some others, described in &<<SECTtlssni>>&,
12703 will be re-expanded early in the TLS session, to permit
12704 a different certificate to be presented (and optionally a different key to be
12705 used) to the client, based upon the value of the SNI extension.
12707 The deprecated &$tls_sni$& variable refers to the inbound side
12708 except when used in the context of an outbound SMTP delivery, when it refers to
12711 .vitem &$tls_out_sni$&
12712 .vindex "&$tls_out_sni$&"
12713 .cindex "TLS" "Server Name Indication"
12715 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
12718 .vitem &$tod_bsdinbox$&
12719 .vindex "&$tod_bsdinbox$&"
12720 The time of day and the date, in the format required for BSD-style mailbox
12721 files, for example: Thu Oct 17 17:14:09 1995.
12723 .vitem &$tod_epoch$&
12724 .vindex "&$tod_epoch$&"
12725 The time and date as a number of seconds since the start of the Unix epoch.
12727 .vitem &$tod_epoch_l$&
12728 .vindex "&$tod_epoch_l$&"
12729 The time and date as a number of microseconds since the start of the Unix epoch.
12731 .vitem &$tod_full$&
12732 .vindex "&$tod_full$&"
12733 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
12734 +0100. The timezone is always given as a numerical offset from UTC, with
12735 positive values used for timezones that are ahead (east) of UTC, and negative
12736 values for those that are behind (west).
12739 .vindex "&$tod_log$&"
12740 The time and date in the format used for writing Exim's log files, for example:
12741 1995-10-12 15:32:29, but without a timezone.
12743 .vitem &$tod_logfile$&
12744 .vindex "&$tod_logfile$&"
12745 This variable contains the date in the format yyyymmdd. This is the format that
12746 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
12749 .vitem &$tod_zone$&
12750 .vindex "&$tod_zone$&"
12751 This variable contains the numerical value of the local timezone, for example:
12754 .vitem &$tod_zulu$&
12755 .vindex "&$tod_zulu$&"
12756 This variable contains the UTC date and time in &"Zulu"& format, as specified
12757 by ISO 8601, for example: 20030221154023Z.
12759 .vitem &$transport_name$&
12760 .cindex "transport" "name"
12761 .cindex "name" "of transport"
12762 .vindex "&$transport_name$&"
12763 During the running of a transport, this variable contains its name.
12766 .vindex "&$value$&"
12767 This variable contains the result of an expansion lookup, extraction operation,
12768 or external command, as described above. It is also used during a
12769 &*reduce*& expansion.
12771 .vitem &$verify_mode$&
12772 .vindex "&$verify_mode$&"
12773 While a router or transport is being run in verify mode
12774 or for cutthrough delivery,
12775 contains "S" for sender-verification or "R" for recipient-verification.
12778 .vitem &$version_number$&
12779 .vindex "&$version_number$&"
12780 The version number of Exim.
12782 .vitem &$warn_message_delay$&
12783 .vindex "&$warn_message_delay$&"
12784 This variable is set only during the creation of a message warning about a
12785 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
12787 .vitem &$warn_message_recipients$&
12788 .vindex "&$warn_message_recipients$&"
12789 This variable is set only during the creation of a message warning about a
12790 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
12796 . ////////////////////////////////////////////////////////////////////////////
12797 . ////////////////////////////////////////////////////////////////////////////
12799 .chapter "Embedded Perl" "CHAPperl"
12800 .scindex IIDperl "Perl" "calling from Exim"
12801 Exim can be built to include an embedded Perl interpreter. When this is done,
12802 Perl subroutines can be called as part of the string expansion process. To make
12803 use of the Perl support, you need version 5.004 or later of Perl installed on
12804 your system. To include the embedded interpreter in the Exim binary, include
12809 in your &_Local/Makefile_& and then build Exim in the normal way.
12812 .section "Setting up so Perl can be used" "SECID85"
12813 .oindex "&%perl_startup%&"
12814 Access to Perl subroutines is via a global configuration option called
12815 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
12816 no &%perl_startup%& option in the Exim configuration file then no Perl
12817 interpreter is started and there is almost no overhead for Exim (since none of
12818 the Perl library will be paged in unless used). If there is a &%perl_startup%&
12819 option then the associated value is taken to be Perl code which is executed in
12820 a newly created Perl interpreter.
12822 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
12823 need backslashes before any characters to escape special meanings. The option
12824 should usually be something like
12826 perl_startup = do '/etc/exim.pl'
12828 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
12829 use from Exim. Exim can be configured either to start up a Perl interpreter as
12830 soon as it is entered, or to wait until the first time it is needed. Starting
12831 the interpreter at the beginning ensures that it is done while Exim still has
12832 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
12833 fact used in a particular run. Also, note that this does not mean that Exim is
12834 necessarily running as root when Perl is called at a later time. By default,
12835 the interpreter is started only when it is needed, but this can be changed in
12839 .oindex "&%perl_at_start%&"
12840 Setting &%perl_at_start%& (a boolean option) in the configuration requests
12841 a startup when Exim is entered.
12843 The command line option &%-ps%& also requests a startup when Exim is entered,
12844 overriding the setting of &%perl_at_start%&.
12847 There is also a command line option &%-pd%& (for delay) which suppresses the
12848 initial startup, even if &%perl_at_start%& is set.
12851 .section "Calling Perl subroutines" "SECID86"
12852 When the configuration file includes a &%perl_startup%& option you can make use
12853 of the string expansion item to call the Perl subroutines that are defined
12854 by the &%perl_startup%& code. The operator is used in any of the following
12858 ${perl{foo}{argument}}
12859 ${perl{foo}{argument1}{argument2} ... }
12861 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
12862 arguments may be passed. Passing more than this results in an expansion failure
12863 with an error message of the form
12865 Too many arguments passed to Perl subroutine "foo" (max is 8)
12867 The return value of the Perl subroutine is evaluated in a scalar context before
12868 it is passed back to Exim to be inserted into the expanded string. If the
12869 return value is &'undef'&, the expansion is forced to fail in the same way as
12870 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
12871 by obeying Perl's &%die%& function, the expansion fails with the error message
12872 that was passed to &%die%&.
12875 .section "Calling Exim functions from Perl" "SECID87"
12876 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
12877 is available to call back into Exim's string expansion function. For example,
12880 my $lp = Exim::expand_string('$local_part');
12882 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
12883 Note those are single quotes and not double quotes to protect against
12884 &$local_part$& being interpolated as a Perl variable.
12886 If the string expansion is forced to fail by a &"fail"& item, the result of
12887 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
12888 expansion string, the Perl call from the original expansion string fails with
12889 an appropriate error message, in the same way as if &%die%& were used.
12891 .cindex "debugging" "from embedded Perl"
12892 .cindex "log" "writing from embedded Perl"
12893 Two other Exim functions are available for use from within Perl code.
12894 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
12895 debugging is enabled. If you want a newline at the end, you must supply it.
12896 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
12897 timestamp. In this case, you should not supply a terminating newline.
12900 .section "Use of standard output and error by Perl" "SECID88"
12901 .cindex "Perl" "standard output and error"
12902 You should not write to the standard error or output streams from within your
12903 Perl code, as it is not defined how these are set up. In versions of Exim
12904 before 4.50, it is possible for the standard output or error to refer to the
12905 SMTP connection during message reception via the daemon. Writing to this stream
12906 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
12907 error streams are connected to &_/dev/null_& in the daemon. The chaos is
12908 avoided, but the output is lost.
12910 .cindex "Perl" "use of &%warn%&"
12911 The Perl &%warn%& statement writes to the standard error stream by default.
12912 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
12913 you have no control. When Exim starts up the Perl interpreter, it arranges for
12914 output from the &%warn%& statement to be written to the Exim main log. You can
12915 change this by including appropriate Perl magic somewhere in your Perl code.
12916 For example, to discard &%warn%& output completely, you need this:
12918 $SIG{__WARN__} = sub { };
12920 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
12921 example, the code for the subroutine is empty, so it does nothing, but you can
12922 include any Perl code that you like. The text of the &%warn%& message is passed
12923 as the first subroutine argument.
12927 . ////////////////////////////////////////////////////////////////////////////
12928 . ////////////////////////////////////////////////////////////////////////////
12930 .chapter "Starting the daemon and the use of network interfaces" &&&
12931 "CHAPinterfaces" &&&
12932 "Starting the daemon"
12933 .cindex "daemon" "starting"
12934 .cindex "interface" "listening"
12935 .cindex "network interface"
12936 .cindex "interface" "network"
12937 .cindex "IP address" "for listening"
12938 .cindex "daemon" "listening IP addresses"
12939 .cindex "TCP/IP" "setting listening interfaces"
12940 .cindex "TCP/IP" "setting listening ports"
12941 A host that is connected to a TCP/IP network may have one or more physical
12942 hardware network interfaces. Each of these interfaces may be configured as one
12943 or more &"logical"& interfaces, which are the entities that a program actually
12944 works with. Each of these logical interfaces is associated with an IP address.
12945 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
12946 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
12947 knowledge about the host's interfaces for use in three different circumstances:
12950 When a listening daemon is started, Exim needs to know which interfaces
12951 and ports to listen on.
12953 When Exim is routing an address, it needs to know which IP addresses
12954 are associated with local interfaces. This is required for the correct
12955 processing of MX lists by removing the local host and others with the
12956 same or higher priority values. Also, Exim needs to detect cases
12957 when an address is routed to an IP address that in fact belongs to the
12958 local host. Unless the &%self%& router option or the &%allow_localhost%&
12959 option of the smtp transport is set (as appropriate), this is treated
12960 as an error situation.
12962 When Exim connects to a remote host, it may need to know which interface to use
12963 for the outgoing connection.
12967 Exim's default behaviour is likely to be appropriate in the vast majority
12968 of cases. If your host has only one interface, and you want all its IP
12969 addresses to be treated in the same way, and you are using only the
12970 standard SMTP port, you should not need to take any special action. The
12971 rest of this chapter does not apply to you.
12973 In a more complicated situation you may want to listen only on certain
12974 interfaces, or on different ports, and for this reason there are a number of
12975 options that can be used to influence Exim's behaviour. The rest of this
12976 chapter describes how they operate.
12978 When a message is received over TCP/IP, the interface and port that were
12979 actually used are set in &$received_ip_address$& and &$received_port$&.
12983 .section "Starting a listening daemon" "SECID89"
12984 When a listening daemon is started (by means of the &%-bd%& command line
12985 option), the interfaces and ports on which it listens are controlled by the
12989 &%daemon_smtp_ports%& contains a list of default ports
12991 (For backward compatibility, this option can also be specified in the singular.)
12993 &%local_interfaces%& contains list of interface IP addresses on which to
12994 listen. Each item may optionally also specify a port.
12997 The default list separator in both cases is a colon, but this can be changed as
12998 described in section &<<SECTlistconstruct>>&. When IPv6 addresses are involved,
12999 it is usually best to change the separator to avoid having to double all the
13000 colons. For example:
13002 local_interfaces = <; 127.0.0.1 ; \
13005 3ffe:ffff:836f::fe86:a061
13007 There are two different formats for specifying a port along with an IP address
13008 in &%local_interfaces%&:
13011 The port is added onto the address with a dot separator. For example, to listen
13012 on port 1234 on two different IP addresses:
13014 local_interfaces = <; 192.168.23.65.1234 ; \
13015 3ffe:ffff:836f::fe86:a061.1234
13018 The IP address is enclosed in square brackets, and the port is added
13019 with a colon separator, for example:
13021 local_interfaces = <; [192.168.23.65]:1234 ; \
13022 [3ffe:ffff:836f::fe86:a061]:1234
13026 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
13027 default setting contains just one port:
13029 daemon_smtp_ports = smtp
13031 If more than one port is listed, each interface that does not have its own port
13032 specified listens on all of them. Ports that are listed in
13033 &%daemon_smtp_ports%& can be identified either by name (defined in
13034 &_/etc/services_&) or by number. However, when ports are given with individual
13035 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
13039 .section "Special IP listening addresses" "SECID90"
13040 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
13041 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
13042 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
13043 instead of setting up separate listening sockets for each interface. The
13044 default value of &%local_interfaces%& is
13046 local_interfaces = 0.0.0.0
13048 when Exim is built without IPv6 support; otherwise it is:
13050 local_interfaces = <; ::0 ; 0.0.0.0
13052 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
13056 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
13057 The &%-oX%& command line option can be used to override the values of
13058 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
13059 instance. Another way of doing this would be to use macros and the &%-D%&
13060 option. However, &%-oX%& can be used by any admin user, whereas modification of
13061 the runtime configuration by &%-D%& is allowed only when the caller is root or
13064 The value of &%-oX%& is a list of items. The default colon separator can be
13065 changed in the usual way if required. If there are any items that do not
13066 contain dots or colons (that is, are not IP addresses), the value of
13067 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
13068 items that do contain dots or colons, the value of &%local_interfaces%& is
13069 replaced by those items. Thus, for example,
13073 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
13076 -oX 192.168.34.5.1125
13078 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
13079 (However, since &%local_interfaces%& now contains no items without ports, the
13080 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
13084 .section "Support for the obsolete SSMTP (or SMTPS) protocol" "SECTsupobssmt"
13085 .cindex "ssmtp protocol"
13086 .cindex "smtps protocol"
13087 .cindex "SMTP" "ssmtp protocol"
13088 .cindex "SMTP" "smtps protocol"
13089 Exim supports the obsolete SSMTP protocol (also known as SMTPS) that was used
13090 before the STARTTLS command was standardized for SMTP. Some legacy clients
13091 still use this protocol. If the &%tls_on_connect_ports%& option is set to a
13092 list of port numbers or service names,
13093 connections to those ports must use SSMTP. The most
13094 common use of this option is expected to be
13096 tls_on_connect_ports = 465
13098 because 465 is the usual port number used by the legacy clients. There is also
13099 a command line option &%-tls-on-connect%&, which forces all ports to behave in
13100 this way when a daemon is started.
13102 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
13103 daemon to listen on those ports. You must still specify them in
13104 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
13105 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
13106 connections via the daemon.)
13111 .section "IPv6 address scopes" "SECID92"
13112 .cindex "IPv6" "address scopes"
13113 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
13114 can, in principle, have the same link-local IPv6 address on different
13115 interfaces. Thus, additional information is needed, over and above the IP
13116 address, to distinguish individual interfaces. A convention of using a
13117 percent sign followed by something (often the interface name) has been
13118 adopted in some cases, leading to addresses like this:
13120 fe80::202:b3ff:fe03:45c1%eth0
13122 To accommodate this usage, a percent sign followed by an arbitrary string is
13123 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
13124 to convert a textual IPv6 address for actual use. This function recognizes the
13125 percent convention in operating systems that support it, and it processes the
13126 address appropriately. Unfortunately, some older libraries have problems with
13127 &[getaddrinfo()]&. If
13129 IPV6_USE_INET_PTON=yes
13131 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
13132 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
13133 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
13134 function.) Of course, this means that the additional functionality of
13135 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
13137 .section "Disabling IPv6" "SECID93"
13138 .cindex "IPv6" "disabling"
13139 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
13140 run on a host whose kernel does not support IPv6. The binary will fall back to
13141 using IPv4, but it may waste resources looking up AAAA records, and trying to
13142 connect to IPv6 addresses, causing delays to mail delivery. If you set the
13143 .oindex "&%disable_ipv6%&"
13144 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
13145 activities take place. AAAA records are never looked up, and any IPv6 addresses
13146 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
13147 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
13148 to handle IPv6 literal addresses.
13150 On the other hand, when IPv6 is in use, there may be times when you want to
13151 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
13152 option to globally suppress the lookup of AAAA records for specified domains,
13153 and you can use the &%ignore_target_hosts%& generic router option to ignore
13154 IPv6 addresses in an individual router.
13158 .section "Examples of starting a listening daemon" "SECID94"
13159 The default case in an IPv6 environment is
13161 daemon_smtp_ports = smtp
13162 local_interfaces = <; ::0 ; 0.0.0.0
13164 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
13165 Either one or two sockets may be used, depending on the characteristics of
13166 the TCP/IP stack. (This is complicated and messy; for more information,
13167 read the comments in the &_daemon.c_& source file.)
13169 To specify listening on ports 25 and 26 on all interfaces:
13171 daemon_smtp_ports = 25 : 26
13173 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
13175 local_interfaces = <; ::0.25 ; ::0.26 \
13176 0.0.0.0.25 ; 0.0.0.0.26
13178 To listen on the default port on all IPv4 interfaces, and on port 26 on the
13179 IPv4 loopback address only:
13181 local_interfaces = 0.0.0.0 : 127.0.0.1.26
13183 To specify listening on the default port on specific interfaces only:
13185 local_interfaces = 10.0.0.67 : 192.168.34.67
13187 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
13191 .section "Recognizing the local host" "SECTreclocipadd"
13192 The &%local_interfaces%& option is also used when Exim needs to determine
13193 whether or not an IP address refers to the local host. That is, the IP
13194 addresses of all the interfaces on which a daemon is listening are always
13197 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
13198 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
13199 available interfaces from the operating system, and extracts the relevant
13200 (that is, IPv4 or IPv6) addresses to use for checking.
13202 Some systems set up large numbers of virtual interfaces in order to provide
13203 many virtual web servers. In this situation, you may want to listen for
13204 email on only a few of the available interfaces, but nevertheless treat all
13205 interfaces as local when routing. You can do this by setting
13206 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
13207 &"all"& wildcard values. These addresses are recognized as local, but are not
13208 used for listening. Consider this example:
13210 local_interfaces = <; 127.0.0.1 ; ::1 ; \
13212 3ffe:2101:12:1:a00:20ff:fe86:a061
13214 extra_local_interfaces = <; ::0 ; 0.0.0.0
13216 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
13217 address, but all available interface addresses are treated as local when
13220 In some environments the local host name may be in an MX list, but with an IP
13221 address that is not assigned to any local interface. In other cases it may be
13222 desirable to treat other host names as if they referred to the local host. Both
13223 these cases can be handled by setting the &%hosts_treat_as_local%& option.
13224 This contains host names rather than IP addresses. When a host is referenced
13225 during routing, either via an MX record or directly, it is treated as the local
13226 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
13227 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
13231 .section "Delivering to a remote host" "SECID95"
13232 Delivery to a remote host is handled by the smtp transport. By default, it
13233 allows the system's TCP/IP functions to choose which interface to use (if
13234 there is more than one) when connecting to a remote host. However, the
13235 &%interface%& option can be set to specify which interface is used. See the
13236 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
13242 . ////////////////////////////////////////////////////////////////////////////
13243 . ////////////////////////////////////////////////////////////////////////////
13245 .chapter "Main configuration" "CHAPmainconfig"
13246 .scindex IIDconfima "configuration file" "main section"
13247 .scindex IIDmaiconf "main configuration"
13248 The first part of the run time configuration file contains three types of item:
13251 Macro definitions: These lines start with an upper case letter. See section
13252 &<<SECTmacrodefs>>& for details of macro processing.
13254 Named list definitions: These lines start with one of the words &"domainlist"&,
13255 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
13256 section &<<SECTnamedlists>>&.
13258 Main configuration settings: Each setting occupies one line of the file
13259 (with possible continuations). If any setting is preceded by the word
13260 &"hide"&, the &%-bP%& command line option displays its value to admin users
13261 only. See section &<<SECTcos>>& for a description of the syntax of these option
13265 This chapter specifies all the main configuration options, along with their
13266 types and default values. For ease of finding a particular option, they appear
13267 in alphabetical order in section &<<SECTalomo>>& below. However, because there
13268 are now so many options, they are first listed briefly in functional groups, as
13269 an aid to finding the name of the option you are looking for. Some options are
13270 listed in more than one group.
13272 .section "Miscellaneous" "SECID96"
13274 .row &%bi_command%& "to run for &%-bi%& command line option"
13275 .row &%disable_ipv6%& "do no IPv6 processing"
13276 .row &%keep_malformed%& "for broken files &-- should not happen"
13277 .row &%localhost_number%& "for unique message ids in clusters"
13278 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
13279 .row &%message_body_visible%& "how much to show in &$message_body$&"
13280 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
13281 .row &%print_topbitchars%& "top-bit characters are printing"
13282 .row &%timezone%& "force time zone"
13286 .section "Exim parameters" "SECID97"
13288 .row &%exim_group%& "override compiled-in value"
13289 .row &%exim_path%& "override compiled-in value"
13290 .row &%exim_user%& "override compiled-in value"
13291 .row &%primary_hostname%& "default from &[uname()]&"
13292 .row &%split_spool_directory%& "use multiple directories"
13293 .row &%spool_directory%& "override compiled-in value"
13298 .section "Privilege controls" "SECID98"
13300 .row &%admin_groups%& "groups that are Exim admin users"
13301 .row &%deliver_drop_privilege%& "drop root for delivery processes"
13302 .row &%local_from_check%& "insert &'Sender:'& if necessary"
13303 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
13304 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
13305 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
13306 .row &%never_users%& "do not run deliveries as these"
13307 .row &%prod_requires_admin%& "forced delivery requires admin user"
13308 .row &%queue_list_requires_admin%& "queue listing requires admin user"
13309 .row &%trusted_groups%& "groups that are trusted"
13310 .row &%trusted_users%& "users that are trusted"
13315 .section "Logging" "SECID99"
13317 .row &%hosts_connection_nolog%& "exemption from connect logging"
13318 .row &%log_file_path%& "override compiled-in value"
13319 .row &%log_selector%& "set/unset optional logging"
13320 .row &%log_timezone%& "add timezone to log lines"
13321 .row &%message_logs%& "create per-message logs"
13322 .row &%preserve_message_logs%& "after message completion"
13323 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
13324 .row &%slow_lookup_log%& "control logging of slow DNS lookups"
13325 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
13326 .row &%syslog_facility%& "set syslog &""facility""& field"
13327 .row &%syslog_processname%& "set syslog &""ident""& field"
13328 .row &%syslog_timestamp%& "timestamp syslog lines"
13329 .row &%write_rejectlog%& "control use of message log"
13334 .section "Frozen messages" "SECID100"
13336 .row &%auto_thaw%& "sets time for retrying frozen messages"
13337 .row &%freeze_tell%& "send message when freezing"
13338 .row &%move_frozen_messages%& "to another directory"
13339 .row &%timeout_frozen_after%& "keep frozen messages only so long"
13344 .section "Data lookups" "SECID101"
13346 .row &%ibase_servers%& "InterBase servers"
13347 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
13348 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
13349 .row &%ldap_cert_file%& "client cert file for LDAP"
13350 .row &%ldap_cert_key%& "client key file for LDAP"
13351 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
13352 .row &%ldap_default_servers%& "used if no server in query"
13353 .row &%ldap_require_cert%& "action to take without LDAP server cert"
13354 .row &%ldap_start_tls%& "require TLS within LDAP"
13355 .row &%ldap_version%& "set protocol version"
13356 .row &%lookup_open_max%& "lookup files held open"
13357 .row &%mysql_servers%& "default MySQL servers"
13358 .row &%oracle_servers%& "Oracle servers"
13359 .row &%pgsql_servers%& "default PostgreSQL servers"
13360 .row &%sqlite_lock_timeout%& "as it says"
13365 .section "Message ids" "SECID102"
13367 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
13368 .row &%message_id_header_text%& "ditto"
13373 .section "Embedded Perl Startup" "SECID103"
13375 .row &%perl_at_start%& "always start the interpreter"
13376 .row &%perl_startup%& "code to obey when starting Perl"
13381 .section "Daemon" "SECID104"
13383 .row &%daemon_smtp_ports%& "default ports"
13384 .row &%daemon_startup_retries%& "number of times to retry"
13385 .row &%daemon_startup_sleep%& "time to sleep between tries"
13386 .row &%extra_local_interfaces%& "not necessarily listened on"
13387 .row &%local_interfaces%& "on which to listen, with optional ports"
13388 .row &%pid_file_path%& "override compiled-in value"
13389 .row &%queue_run_max%& "maximum simultaneous queue runners"
13394 .section "Resource control" "SECID105"
13396 .row &%check_log_inodes%& "before accepting a message"
13397 .row &%check_log_space%& "before accepting a message"
13398 .row &%check_spool_inodes%& "before accepting a message"
13399 .row &%check_spool_space%& "before accepting a message"
13400 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
13401 .row &%queue_only_load%& "queue incoming if load high"
13402 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
13403 .row &%queue_run_max%& "maximum simultaneous queue runners"
13404 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
13405 .row &%smtp_accept_max%& "simultaneous incoming connections"
13406 .row &%smtp_accept_max_nonmail%& "non-mail commands"
13407 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
13408 .row &%smtp_accept_max_per_connection%& "messages per connection"
13409 .row &%smtp_accept_max_per_host%& "connections from one host"
13410 .row &%smtp_accept_queue%& "queue mail if more connections"
13411 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
13413 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
13414 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
13415 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
13416 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
13417 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
13422 .section "Policy controls" "SECID106"
13424 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
13425 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
13426 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
13427 .row &%acl_smtp_auth%& "ACL for AUTH"
13428 .row &%acl_smtp_connect%& "ACL for connection"
13429 .row &%acl_smtp_data%& "ACL for DATA"
13430 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
13431 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
13432 .row &%acl_smtp_etrn%& "ACL for ETRN"
13433 .row &%acl_smtp_expn%& "ACL for EXPN"
13434 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
13435 .row &%acl_smtp_mail%& "ACL for MAIL"
13436 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
13437 .row &%acl_smtp_mime%& "ACL for MIME parts"
13438 .row &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
13439 .row &%acl_smtp_predata%& "ACL for start of data"
13440 .row &%acl_smtp_quit%& "ACL for QUIT"
13441 .row &%acl_smtp_rcpt%& "ACL for RCPT"
13442 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
13443 .row &%acl_smtp_vrfy%& "ACL for VRFY"
13444 .row &%av_scanner%& "specify virus scanner"
13445 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
13447 .row &%dns_csa_search_limit%& "control CSA parent search depth"
13448 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
13449 .row &%header_maxsize%& "total size of message header"
13450 .row &%header_line_maxsize%& "individual header line limit"
13451 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
13452 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
13453 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
13454 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
13455 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
13456 .row &%host_lookup%& "host name looked up for these hosts"
13457 .row &%host_lookup_order%& "order of DNS and local name lookups"
13458 .row &%host_reject_connection%& "reject connection from these hosts"
13459 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
13460 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
13461 .row &%message_size_limit%& "for all messages"
13462 .row &%percent_hack_domains%& "recognize %-hack for these domains"
13463 .row &%spamd_address%& "set interface to SpamAssassin"
13464 .row &%strict_acl_vars%& "object to unset ACL variables"
13469 .section "Callout cache" "SECID107"
13471 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
13473 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
13475 .row &%callout_negative_expire%& "timeout for negative address cache item"
13476 .row &%callout_positive_expire%& "timeout for positive address cache item"
13477 .row &%callout_random_local_part%& "string to use for &""random""& testing"
13482 .section "TLS" "SECID108"
13484 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
13485 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
13486 .row &%openssl_options%& "adjust OpenSSL compatibility options"
13487 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
13488 .row &%tls_certificate%& "location of server certificate"
13489 .row &%tls_crl%& "certificate revocation list"
13490 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
13491 .row &%tls_dhparam%& "DH parameters for server"
13492 .row &%tls_eccurve%& "EC curve selection for server"
13493 .row &%tls_ocsp_file%& "location of server certificate status proof"
13494 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
13495 .row &%tls_privatekey%& "location of server private key"
13496 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
13497 .row &%tls_require_ciphers%& "specify acceptable ciphers"
13498 .row &%tls_try_verify_hosts%& "try to verify client certificate"
13499 .row &%tls_verify_certificates%& "expected client certificates"
13500 .row &%tls_verify_hosts%& "insist on client certificate verify"
13505 .section "Local user handling" "SECID109"
13507 .row &%finduser_retries%& "useful in NIS environments"
13508 .row &%gecos_name%& "used when creating &'Sender:'&"
13509 .row &%gecos_pattern%& "ditto"
13510 .row &%max_username_length%& "for systems that truncate"
13511 .row &%unknown_login%& "used when no login name found"
13512 .row &%unknown_username%& "ditto"
13513 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
13514 .row &%uucp_from_sender%& "ditto"
13519 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
13521 .row &%header_maxsize%& "total size of message header"
13522 .row &%header_line_maxsize%& "individual header line limit"
13523 .row &%message_size_limit%& "applies to all messages"
13524 .row &%percent_hack_domains%& "recognize %-hack for these domains"
13525 .row &%received_header_text%& "expanded to make &'Received:'&"
13526 .row &%received_headers_max%& "for mail loop detection"
13527 .row &%recipients_max%& "limit per message"
13528 .row &%recipients_max_reject%& "permanently reject excess recipients"
13534 .section "Non-SMTP incoming messages" "SECID111"
13536 .row &%receive_timeout%& "for non-SMTP messages"
13543 .section "Incoming SMTP messages" "SECID112"
13544 See also the &'Policy controls'& section above.
13547 .row &%dkim_verify_signers%& "DKIM domain for which DKIM ACL is run"
13548 .row &%host_lookup%& "host name looked up for these hosts"
13549 .row &%host_lookup_order%& "order of DNS and local name lookups"
13550 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
13551 .row &%rfc1413_hosts%& "make ident calls to these hosts"
13552 .row &%rfc1413_query_timeout%& "zero disables ident calls"
13553 .row &%sender_unqualified_hosts%& "may send unqualified senders"
13554 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
13555 .row &%smtp_accept_max%& "simultaneous incoming connections"
13556 .row &%smtp_accept_max_nonmail%& "non-mail commands"
13557 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
13558 .row &%smtp_accept_max_per_connection%& "messages per connection"
13559 .row &%smtp_accept_max_per_host%& "connections from one host"
13560 .row &%smtp_accept_queue%& "queue mail if more connections"
13561 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
13563 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
13564 .row &%smtp_active_hostname%& "host name to use in messages"
13565 .row &%smtp_banner%& "text for welcome banner"
13566 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
13567 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
13568 .row &%smtp_enforce_sync%& "of SMTP command/responses"
13569 .row &%smtp_etrn_command%& "what to run for ETRN"
13570 .row &%smtp_etrn_serialize%& "only one at once"
13571 .row &%smtp_load_reserve%& "only reserve hosts if this load"
13572 .row &%smtp_max_unknown_commands%& "before dropping connection"
13573 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
13574 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
13575 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
13576 .row &%smtp_receive_timeout%& "per command or data line"
13577 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
13578 .row &%smtp_return_error_details%& "give detail on rejections"
13583 .section "SMTP extensions" "SECID113"
13585 .row &%accept_8bitmime%& "advertise 8BITMIME"
13586 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
13587 .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
13588 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
13589 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
13590 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
13591 .row &%prdr_enable%& "advertise PRDR to all hosts"
13592 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
13597 .section "Processing messages" "SECID114"
13599 .row &%allow_domain_literals%& "recognize domain literal syntax"
13600 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
13601 .row &%allow_utf8_domains%& "in addresses"
13602 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
13604 .row &%delivery_date_remove%& "from incoming messages"
13605 .row &%envelope_to_remove%& "from incoming messages"
13606 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
13607 .row &%headers_charset%& "default for translations"
13608 .row &%qualify_domain%& "default for senders"
13609 .row &%qualify_recipient%& "default for recipients"
13610 .row &%return_path_remove%& "from incoming messages"
13611 .row &%strip_excess_angle_brackets%& "in addresses"
13612 .row &%strip_trailing_dot%& "at end of addresses"
13613 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
13618 .section "System filter" "SECID115"
13620 .row &%system_filter%& "locate system filter"
13621 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
13623 .row &%system_filter_file_transport%& "transport for delivery to a file"
13624 .row &%system_filter_group%& "group for filter running"
13625 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
13626 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
13627 .row &%system_filter_user%& "user for filter running"
13632 .section "Routing and delivery" "SECID116"
13634 .row &%disable_ipv6%& "do no IPv6 processing"
13635 .row &%dns_again_means_nonexist%& "for broken domains"
13636 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
13637 .row &%dns_dnssec_ok%& "parameter for resolver"
13638 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
13639 .row &%dns_retrans%& "parameter for resolver"
13640 .row &%dns_retry%& "parameter for resolver"
13641 .row &%dns_trust_aa%& "DNS zones trusted as authentic"
13642 .row &%dns_use_edns0%& "parameter for resolver"
13643 .row &%hold_domains%& "hold delivery for these domains"
13644 .row &%local_interfaces%& "for routing checks"
13645 .row &%queue_domains%& "no immediate delivery for these"
13646 .row &%queue_only%& "no immediate delivery at all"
13647 .row &%queue_only_file%& "no immediate delivery if file exists"
13648 .row &%queue_only_load%& "no immediate delivery if load is high"
13649 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
13650 .row &%queue_only_override%& "allow command line to override"
13651 .row &%queue_run_in_order%& "order of arrival"
13652 .row &%queue_run_max%& "of simultaneous queue runners"
13653 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
13654 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
13655 .row &%remote_sort_domains%& "order of remote deliveries"
13656 .row &%retry_data_expire%& "timeout for retry data"
13657 .row &%retry_interval_max%& "safety net for retry rules"
13662 .section "Bounce and warning messages" "SECID117"
13664 .row &%bounce_message_file%& "content of bounce"
13665 .row &%bounce_message_text%& "content of bounce"
13666 .row &%bounce_return_body%& "include body if returning message"
13667 .row &%bounce_return_message%& "include original message in bounce"
13668 .row &%bounce_return_size_limit%& "limit on returned message"
13669 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
13670 .row &%dsn_from%& "set &'From:'& contents in bounces"
13671 .row &%errors_copy%& "copy bounce messages"
13672 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
13673 .row &%delay_warning%& "time schedule"
13674 .row &%delay_warning_condition%& "condition for warning messages"
13675 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
13676 .row &%smtp_return_error_details%& "give detail on rejections"
13677 .row &%warn_message_file%& "content of warning message"
13682 .section "Alphabetical list of main options" "SECTalomo"
13683 Those options that undergo string expansion before use are marked with
13686 .option accept_8bitmime main boolean true
13688 .cindex "8-bit characters"
13689 .cindex "log" "selectors"
13690 .cindex "log" "8BITMIME"
13691 This option causes Exim to send 8BITMIME in its response to an SMTP
13692 EHLO command, and to accept the BODY= parameter on MAIL commands.
13693 However, though Exim is 8-bit clean, it is not a protocol converter, and it
13694 takes no steps to do anything special with messages received by this route.
13696 Historically Exim kept this option off by default, but the maintainers
13697 feel that in today's Internet, this causes more problems than it solves.
13698 It now defaults to true.
13699 A more detailed analysis of the issues is provided by Dan Bernstein:
13701 &url(http://cr.yp.to/smtp/8bitmime.html)
13704 To log received 8BITMIME status use
13706 log_selector = +8bitmime
13709 .option acl_not_smtp main string&!! unset
13710 .cindex "&ACL;" "for non-SMTP messages"
13711 .cindex "non-SMTP messages" "ACLs for"
13712 This option defines the ACL that is run when a non-SMTP message has been
13713 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
13716 .option acl_not_smtp_mime main string&!! unset
13717 This option defines the ACL that is run for individual MIME parts of non-SMTP
13718 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
13721 .option acl_not_smtp_start main string&!! unset
13722 .cindex "&ACL;" "at start of non-SMTP message"
13723 .cindex "non-SMTP messages" "ACLs for"
13724 This option defines the ACL that is run before Exim starts reading a
13725 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
13727 .option acl_smtp_auth main string&!! unset
13728 .cindex "&ACL;" "setting up for SMTP commands"
13729 .cindex "AUTH" "ACL for"
13730 This option defines the ACL that is run when an SMTP AUTH command is
13731 received. See chapter &<<CHAPACL>>& for further details.
13733 .option acl_smtp_connect main string&!! unset
13734 .cindex "&ACL;" "on SMTP connection"
13735 This option defines the ACL that is run when an SMTP connection is received.
13736 See chapter &<<CHAPACL>>& for further details.
13738 .option acl_smtp_data main string&!! unset
13739 .cindex "DATA" "ACL for"
13740 This option defines the ACL that is run after an SMTP DATA command has been
13741 processed and the message itself has been received, but before the final
13742 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
13744 .option acl_smtp_data_prdr main string&!! accept
13745 .cindex "PRDR" "ACL for"
13746 .cindex "DATA" "PRDR ACL for"
13747 .cindex "&ACL;" "PRDR-related"
13748 .cindex "&ACL;" "per-user data processing"
13749 This option defines the ACL that,
13750 if the PRDR feature has been negotiated,
13751 is run for each recipient after an SMTP DATA command has been
13752 processed and the message itself has been received, but before the
13753 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
13755 .option acl_smtp_dkim main string&!! unset
13756 .cindex DKIM "ACL for"
13757 This option defines the ACL that is run for each DKIM signature
13758 of a received message.
13759 See chapter &<<CHAPdkim>>& for further details.
13761 .option acl_smtp_etrn main string&!! unset
13762 .cindex "ETRN" "ACL for"
13763 This option defines the ACL that is run when an SMTP ETRN command is
13764 received. See chapter &<<CHAPACL>>& for further details.
13766 .option acl_smtp_expn main string&!! unset
13767 .cindex "EXPN" "ACL for"
13768 This option defines the ACL that is run when an SMTP EXPN command is
13769 received. See chapter &<<CHAPACL>>& for further details.
13771 .option acl_smtp_helo main string&!! unset
13772 .cindex "EHLO" "ACL for"
13773 .cindex "HELO" "ACL for"
13774 This option defines the ACL that is run when an SMTP EHLO or HELO
13775 command is received. See chapter &<<CHAPACL>>& for further details.
13778 .option acl_smtp_mail main string&!! unset
13779 .cindex "MAIL" "ACL for"
13780 This option defines the ACL that is run when an SMTP MAIL command is
13781 received. See chapter &<<CHAPACL>>& for further details.
13783 .option acl_smtp_mailauth main string&!! unset
13784 .cindex "AUTH" "on MAIL command"
13785 This option defines the ACL that is run when there is an AUTH parameter on
13786 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
13787 &<<CHAPSMTPAUTH>>& for details of authentication.
13789 .option acl_smtp_mime main string&!! unset
13790 .cindex "MIME content scanning" "ACL for"
13791 This option is available when Exim is built with the content-scanning
13792 extension. It defines the ACL that is run for each MIME part in a message. See
13793 section &<<SECTscanmimepart>>& for details.
13795 .option acl_smtp_notquit main string&!! unset
13796 .cindex "not-QUIT, ACL for"
13797 This option defines the ACL that is run when an SMTP session
13798 ends without a QUIT command being received.
13799 See chapter &<<CHAPACL>>& for further details.
13801 .option acl_smtp_predata main string&!! unset
13802 This option defines the ACL that is run when an SMTP DATA command is
13803 received, before the message itself is received. See chapter &<<CHAPACL>>& for
13806 .option acl_smtp_quit main string&!! unset
13807 .cindex "QUIT, ACL for"
13808 This option defines the ACL that is run when an SMTP QUIT command is
13809 received. See chapter &<<CHAPACL>>& for further details.
13811 .option acl_smtp_rcpt main string&!! unset
13812 .cindex "RCPT" "ACL for"
13813 This option defines the ACL that is run when an SMTP RCPT command is
13814 received. See chapter &<<CHAPACL>>& for further details.
13816 .option acl_smtp_starttls main string&!! unset
13817 .cindex "STARTTLS, ACL for"
13818 This option defines the ACL that is run when an SMTP STARTTLS command is
13819 received. See chapter &<<CHAPACL>>& for further details.
13821 .option acl_smtp_vrfy main string&!! unset
13822 .cindex "VRFY" "ACL for"
13823 This option defines the ACL that is run when an SMTP VRFY command is
13824 received. See chapter &<<CHAPACL>>& for further details.
13826 .option admin_groups main "string list&!!" unset
13827 .cindex "admin user"
13828 This option is expanded just once, at the start of Exim's processing. If the
13829 current group or any of the supplementary groups of an Exim caller is in this
13830 colon-separated list, the caller has admin privileges. If all your system
13831 programmers are in a specific group, for example, you can give them all Exim
13832 admin privileges by putting that group in &%admin_groups%&. However, this does
13833 not permit them to read Exim's spool files (whose group owner is the Exim gid).
13834 To permit this, you have to add individuals to the Exim group.
13836 .option allow_domain_literals main boolean false
13837 .cindex "domain literal"
13838 If this option is set, the RFC 2822 domain literal format is permitted in
13839 email addresses. The option is not set by default, because the domain literal
13840 format is not normally required these days, and few people know about it. It
13841 has, however, been exploited by mail abusers.
13843 Unfortunately, it seems that some DNS black list maintainers are using this
13844 format to report black listing to postmasters. If you want to accept messages
13845 addressed to your hosts by IP address, you need to set
13846 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
13847 domains (defined in the named domain list &%local_domains%& in the default
13848 configuration). This &"magic string"& matches the domain literal form of all
13849 the local host's IP addresses.
13852 .option allow_mx_to_ip main boolean false
13853 .cindex "MX record" "pointing to IP address"
13854 It appears that more and more DNS zone administrators are breaking the rules
13855 and putting domain names that look like IP addresses on the right hand side of
13856 MX records. Exim follows the rules and rejects this, giving an error message
13857 that explains the misconfiguration. However, some other MTAs support this
13858 practice, so to avoid &"Why can't Exim do this?"& complaints,
13859 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
13860 recommended, except when you have no other choice.
13862 .option allow_utf8_domains main boolean false
13863 .cindex "domain" "UTF-8 characters in"
13864 .cindex "UTF-8" "in domain name"
13865 Lots of discussion is going on about internationalized domain names. One
13866 camp is strongly in favour of just using UTF-8 characters, and it seems
13867 that at least two other MTAs permit this. This option allows Exim users to
13868 experiment if they wish.
13870 If it is set true, Exim's domain parsing function allows valid
13871 UTF-8 multicharacters to appear in domain name components, in addition to
13872 letters, digits, and hyphens. However, just setting this option is not
13873 enough; if you want to look up these domain names in the DNS, you must also
13874 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
13875 suitable setting is:
13877 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
13878 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
13880 Alternatively, you can just disable this feature by setting
13882 dns_check_names_pattern =
13884 That is, set the option to an empty string so that no check is done.
13887 .option auth_advertise_hosts main "host list&!!" *
13888 .cindex "authentication" "advertising"
13889 .cindex "AUTH" "advertising"
13890 If any server authentication mechanisms are configured, Exim advertises them in
13891 response to an EHLO command only if the calling host matches this list.
13892 Otherwise, Exim does not advertise AUTH.
13893 Exim does not accept AUTH commands from clients to which it has not
13894 advertised the availability of AUTH. The advertising of individual
13895 authentication mechanisms can be controlled by the use of the
13896 &%server_advertise_condition%& generic authenticator option on the individual
13897 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
13899 Certain mail clients (for example, Netscape) require the user to provide a name
13900 and password for authentication if AUTH is advertised, even though it may
13901 not be needed (the host may accept messages from hosts on its local LAN without
13902 authentication, for example). The &%auth_advertise_hosts%& option can be used
13903 to make these clients more friendly by excluding them from the set of hosts to
13904 which Exim advertises AUTH.
13906 .cindex "AUTH" "advertising when encrypted"
13907 If you want to advertise the availability of AUTH only when the connection
13908 is encrypted using TLS, you can make use of the fact that the value of this
13909 option is expanded, with a setting like this:
13911 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
13913 .vindex "&$tls_in_cipher$&"
13914 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
13915 the expansion is empty, thus matching no hosts. Otherwise, the result of the
13916 expansion is *, which matches all hosts.
13919 .option auto_thaw main time 0s
13920 .cindex "thawing messages"
13921 .cindex "unfreezing messages"
13922 If this option is set to a time greater than zero, a queue runner will try a
13923 new delivery attempt on any frozen message, other than a bounce message, if
13924 this much time has passed since it was frozen. This may result in the message
13925 being re-frozen if nothing has changed since the last attempt. It is a way of
13926 saying &"keep on trying, even though there are big problems"&.
13928 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
13929 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
13930 thought to be very useful any more, and its use should probably be avoided.
13933 .option av_scanner main string "see below"
13934 This option is available if Exim is built with the content-scanning extension.
13935 It specifies which anti-virus scanner to use. The default value is:
13937 sophie:/var/run/sophie
13939 If the value of &%av_scanner%& starts with a dollar character, it is expanded
13940 before use. See section &<<SECTscanvirus>>& for further details.
13943 .option bi_command main string unset
13945 This option supplies the name of a command that is run when Exim is called with
13946 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
13947 just the command name, it is not a complete command line. If an argument is
13948 required, it must come from the &%-oA%& command line option.
13951 .option bounce_message_file main string unset
13952 .cindex "bounce message" "customizing"
13953 .cindex "customizing" "bounce message"
13954 This option defines a template file containing paragraphs of text to be used
13955 for constructing bounce messages. Details of the file's contents are given in
13956 chapter &<<CHAPemsgcust>>&. See also &%warn_message_file%&.
13959 .option bounce_message_text main string unset
13960 When this option is set, its contents are included in the default bounce
13961 message immediately after &"This message was created automatically by mail
13962 delivery software."& It is not used if &%bounce_message_file%& is set.
13964 .option bounce_return_body main boolean true
13965 .cindex "bounce message" "including body"
13966 This option controls whether the body of an incoming message is included in a
13967 bounce message when &%bounce_return_message%& is true. The default setting
13968 causes the entire message, both header and body, to be returned (subject to the
13969 value of &%bounce_return_size_limit%&). If this option is false, only the
13970 message header is included. In the case of a non-SMTP message containing an
13971 error that is detected during reception, only those header lines preceding the
13972 point at which the error was detected are returned.
13973 .cindex "bounce message" "including original"
13975 .option bounce_return_message main boolean true
13976 If this option is set false, none of the original message is included in
13977 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
13978 &%bounce_return_body%&.
13981 .option bounce_return_size_limit main integer 100K
13982 .cindex "size" "of bounce, limit"
13983 .cindex "bounce message" "size limit"
13984 .cindex "limit" "bounce message size"
13985 This option sets a limit in bytes on the size of messages that are returned to
13986 senders as part of bounce messages when &%bounce_return_message%& is true. The
13987 limit should be less than the value of the global &%message_size_limit%& and of
13988 any &%message_size_limit%& settings on transports, to allow for the bounce text
13989 that Exim generates. If this option is set to zero there is no limit.
13991 When the body of any message that is to be included in a bounce message is
13992 greater than the limit, it is truncated, and a comment pointing this out is
13993 added at the top. The actual cutoff may be greater than the value given, owing
13994 to the use of buffering for transferring the message in chunks (typically 8K in
13995 size). The idea is to save bandwidth on those undeliverable 15-megabyte
13998 .option bounce_sender_authentication main string unset
13999 .cindex "bounce message" "sender authentication"
14000 .cindex "authentication" "bounce message"
14001 .cindex "AUTH" "on bounce message"
14002 This option provides an authenticated sender address that is sent with any
14003 bounce messages generated by Exim that are sent over an authenticated SMTP
14004 connection. A typical setting might be:
14006 bounce_sender_authentication = mailer-daemon@my.domain.example
14008 which would cause bounce messages to be sent using the SMTP command:
14010 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
14012 The value of &%bounce_sender_authentication%& must always be a complete email
14015 .option callout_domain_negative_expire main time 3h
14016 .cindex "caching" "callout timeouts"
14017 .cindex "callout" "caching timeouts"
14018 This option specifies the expiry time for negative callout cache data for a
14019 domain. See section &<<SECTcallver>>& for details of callout verification, and
14020 section &<<SECTcallvercache>>& for details of the caching.
14023 .option callout_domain_positive_expire main time 7d
14024 This option specifies the expiry time for positive callout cache data for a
14025 domain. See section &<<SECTcallver>>& for details of callout verification, and
14026 section &<<SECTcallvercache>>& for details of the caching.
14029 .option callout_negative_expire main time 2h
14030 This option specifies the expiry time for negative callout cache data for an
14031 address. See section &<<SECTcallver>>& for details of callout verification, and
14032 section &<<SECTcallvercache>>& for details of the caching.
14035 .option callout_positive_expire main time 24h
14036 This option specifies the expiry time for positive callout cache data for an
14037 address. See section &<<SECTcallver>>& for details of callout verification, and
14038 section &<<SECTcallvercache>>& for details of the caching.
14041 .option callout_random_local_part main string&!! "see below"
14042 This option defines the &"random"& local part that can be used as part of
14043 callout verification. The default value is
14045 $primary_hostname-$tod_epoch-testing
14047 See section &<<CALLaddparcall>>& for details of how this value is used.
14050 .option check_log_inodes main integer 0
14051 See &%check_spool_space%& below.
14054 .option check_log_space main integer 0
14055 See &%check_spool_space%& below.
14057 .oindex "&%check_rfc2047_length%&"
14058 .cindex "RFC 2047" "disabling length check"
14059 .option check_rfc2047_length main boolean true
14060 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
14061 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
14062 word; strings to be encoded that exceed this length are supposed to use
14063 multiple encoded words. By default, Exim does not recognize encoded words that
14064 exceed the maximum length. However, it seems that some software, in violation
14065 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
14066 set false, Exim recognizes encoded words of any length.
14069 .option check_spool_inodes main integer 0
14070 See &%check_spool_space%& below.
14073 .option check_spool_space main integer 0
14074 .cindex "checking disk space"
14075 .cindex "disk space, checking"
14076 .cindex "spool directory" "checking space"
14077 The four &%check_...%& options allow for checking of disk resources before a
14078 message is accepted.
14080 .vindex "&$log_inodes$&"
14081 .vindex "&$log_space$&"
14082 .vindex "&$spool_inodes$&"
14083 .vindex "&$spool_space$&"
14084 When any of these options are set, they apply to all incoming messages. If you
14085 want to apply different checks to different kinds of message, you can do so by
14086 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
14087 &$spool_space$& in an ACL with appropriate additional conditions.
14090 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
14091 either value is greater than zero, for example:
14093 check_spool_space = 10M
14094 check_spool_inodes = 100
14096 The spool partition is the one that contains the directory defined by
14097 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
14100 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
14101 files are written if either is greater than zero. These should be set only if
14102 &%log_file_path%& and &%spool_directory%& refer to different partitions.
14104 If there is less space or fewer inodes than requested, Exim refuses to accept
14105 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
14106 error response to the MAIL command. If ESMTP is in use and there was a
14107 SIZE parameter on the MAIL command, its value is added to the
14108 &%check_spool_space%& value, and the check is performed even if
14109 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
14111 The values for &%check_spool_space%& and &%check_log_space%& are held as a
14112 number of kilobytes. If a non-multiple of 1024 is specified, it is rounded up.
14114 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
14115 failure a message is written to stderr and Exim exits with a non-zero code, as
14116 it obviously cannot send an error message of any kind.
14118 .option daemon_smtp_ports main string &`smtp`&
14119 .cindex "port" "for daemon"
14120 .cindex "TCP/IP" "setting listening ports"
14121 This option specifies one or more default SMTP ports on which the Exim daemon
14122 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
14123 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
14125 .option daemon_startup_retries main integer 9
14126 .cindex "daemon startup, retrying"
14127 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
14128 the daemon at startup when it cannot immediately bind a listening socket
14129 (typically because the socket is already in use): &%daemon_startup_retries%&
14130 defines the number of retries after the first failure, and
14131 &%daemon_startup_sleep%& defines the length of time to wait between retries.
14133 .option daemon_startup_sleep main time 30s
14134 See &%daemon_startup_retries%&.
14136 .option delay_warning main "time list" 24h
14137 .cindex "warning of delay"
14138 .cindex "delay warning, specifying"
14139 When a message is delayed, Exim sends a warning message to the sender at
14140 intervals specified by this option. The data is a colon-separated list of times
14141 after which to send warning messages. If the value of the option is an empty
14142 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
14143 message has been on the queue for longer than the last time, the last interval
14144 between the times is used to compute subsequent warning times. For example,
14147 delay_warning = 4h:8h:24h
14149 the first message is sent after 4 hours, the second after 8 hours, and
14150 the third one after 24 hours. After that, messages are sent every 16 hours,
14151 because that is the interval between the last two times on the list. If you set
14152 just one time, it specifies the repeat interval. For example, with:
14156 messages are repeated every six hours. To stop warnings after a given time, set
14157 a very large time at the end of the list. For example:
14159 delay_warning = 2h:12h:99d
14161 Note that the option is only evaluated at the time a delivery attempt fails,
14162 which depends on retry and queue-runner configuration.
14163 Typically retries will be configured more frequently than warning messages.
14165 .option delay_warning_condition main string&!! "see below"
14166 .vindex "&$domain$&"
14167 The string is expanded at the time a warning message might be sent. If all the
14168 deferred addresses have the same domain, it is set in &$domain$& during the
14169 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
14170 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
14171 &"false"& (the comparison being done caselessly) then the warning message is
14172 not sent. The default is:
14174 delay_warning_condition = ${if or {\
14175 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
14176 { match{$h_precedence:}{(?i)bulk|list|junk} }\
14177 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
14180 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
14181 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
14182 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
14183 &"auto-replied"& in an &'Auto-Submitted:'& header.
14185 .option deliver_drop_privilege main boolean false
14186 .cindex "unprivileged delivery"
14187 .cindex "delivery" "unprivileged"
14188 If this option is set true, Exim drops its root privilege at the start of a
14189 delivery process, and runs as the Exim user throughout. This severely restricts
14190 the kinds of local delivery that are possible, but is viable in certain types
14191 of configuration. There is a discussion about the use of root privilege in
14192 chapter &<<CHAPsecurity>>&.
14194 .option deliver_queue_load_max main fixed-point unset
14195 .cindex "load average"
14196 .cindex "queue runner" "abandoning"
14197 When this option is set, a queue run is abandoned if the system load average
14198 becomes greater than the value of the option. The option has no effect on
14199 ancient operating systems on which Exim cannot determine the load average.
14200 See also &%queue_only_load%& and &%smtp_load_reserve%&.
14203 .option delivery_date_remove main boolean true
14204 .cindex "&'Delivery-date:'& header line"
14205 Exim's transports have an option for adding a &'Delivery-date:'& header to a
14206 message when it is delivered, in exactly the same way as &'Return-path:'& is
14207 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
14208 should not be present in incoming messages, and this option causes them to be
14209 removed at the time the message is received, to avoid any problems that might
14210 occur when a delivered message is subsequently sent on to some other recipient.
14212 .option disable_fsync main boolean false
14213 .cindex "&[fsync()]&, disabling"
14214 This option is available only if Exim was built with the compile-time option
14215 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
14216 a runtime configuration generates an &"unknown option"& error. You should not
14217 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
14218 really, really, really understand what you are doing. &'No pre-compiled
14219 distributions of Exim should ever make this option available.'&
14221 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
14222 updated files' data to be written to disc before continuing. Unexpected events
14223 such as crashes and power outages may cause data to be lost or scrambled.
14224 Here be Dragons. &*Beware.*&
14227 .option disable_ipv6 main boolean false
14228 .cindex "IPv6" "disabling"
14229 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
14230 activities take place. AAAA records are never looked up, and any IPv6 addresses
14231 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
14232 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14233 to handle IPv6 literal addresses.
14236 .option dkim_verify_signers main "domain list&!!" $dkim_signers
14237 .cindex DKIM "controlling calls to the ACL"
14238 This option gives a list of DKIM domains for which the DKIM ACL is run.
14239 It is expanded after the message is received; by default it runs
14240 the ACL once for each signature in the message.
14241 See chapter &<<CHAPdkim>>&.
14244 .option dns_again_means_nonexist main "domain list&!!" unset
14245 .cindex "DNS" "&""try again""& response; overriding"
14246 DNS lookups give a &"try again"& response for the DNS errors
14247 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
14248 keep trying to deliver a message, or to give repeated temporary errors to
14249 incoming mail. Sometimes the effect is caused by a badly set up name server and
14250 may persist for a long time. If a domain which exhibits this problem matches
14251 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
14252 This option should be used with care. You can make it apply to reverse lookups
14253 by a setting such as this:
14255 dns_again_means_nonexist = *.in-addr.arpa
14257 This option applies to all DNS lookups that Exim does. It also applies when the
14258 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
14259 since these are most likely to be caused by DNS lookup problems. The
14260 &(dnslookup)& router has some options of its own for controlling what happens
14261 when lookups for MX or SRV records give temporary errors. These more specific
14262 options are applied after this global option.
14264 .option dns_check_names_pattern main string "see below"
14265 .cindex "DNS" "pre-check of name syntax"
14266 When this option is set to a non-empty string, it causes Exim to check domain
14267 names for characters that are not allowed in host names before handing them to
14268 the DNS resolver, because some resolvers give temporary errors for names that
14269 contain unusual characters. If a domain name contains any unwanted characters,
14270 a &"not found"& result is forced, and the resolver is not called. The check is
14271 done by matching the domain name against a regular expression, which is the
14272 value of this option. The default pattern is
14274 dns_check_names_pattern = \
14275 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
14277 which permits only letters, digits, slashes, and hyphens in components, but
14278 they must start and end with a letter or digit. Slashes are not, in fact,
14279 permitted in host names, but they are found in certain NS records (which can be
14280 accessed in Exim by using a &%dnsdb%& lookup). If you set
14281 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
14284 .option dns_csa_search_limit main integer 5
14285 This option controls the depth of parental searching for CSA SRV records in the
14286 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
14288 .option dns_csa_use_reverse main boolean true
14289 This option controls whether or not an IP address, given as a CSA domain, is
14290 reversed and looked up in the reverse DNS, as described in more detail in
14291 section &<<SECTverifyCSA>>&.
14294 .option dns_dnssec_ok main integer -1
14295 .cindex "DNS" "resolver options"
14296 .cindex "DNS" "DNSSEC"
14297 If this option is set to a non-negative number then Exim will initialise the
14298 DNS resolver library to either use or not use DNSSEC, overriding the system
14299 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
14301 If the resolver library does not support DNSSEC then this option has no effect.
14304 .option dns_ipv4_lookup main "domain list&!!" unset
14305 .cindex "IPv6" "DNS lookup for AAAA records"
14306 .cindex "DNS" "IPv6 lookup for AAAA records"
14307 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
14308 looks for IPv6 address records (AAAA records) as well as IPv4 address records
14309 (A records) when trying to find IP addresses for hosts, unless the host's
14310 domain matches this list.
14312 This is a fudge to help with name servers that give big delays or otherwise do
14313 not work for the AAAA record type. In due course, when the world's name
14314 servers have all been upgraded, there should be no need for this option.
14317 .option dns_retrans main time 0s
14318 .cindex "DNS" "resolver options"
14319 .cindex timeout "dns lookup"
14320 .cindex "DNS" timeout
14321 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
14322 retransmission and retry parameters for DNS lookups. Values of zero (the
14323 defaults) leave the system default settings unchanged. The first value is the
14324 time between retries, and the second is the number of retries. It isn't
14325 totally clear exactly how these settings affect the total time a DNS lookup may
14326 take. I haven't found any documentation about timeouts on DNS lookups; these
14327 parameter values are available in the external resolver interface structure,
14328 but nowhere does it seem to describe how they are used or what you might want
14330 See also the &%slow_lookup_log%& option.
14333 .option dns_retry main integer 0
14334 See &%dns_retrans%& above.
14337 .option dns_trust_aa main "domain list&!!" unset
14338 .cindex "DNS" "resolver options"
14339 .cindex "DNS" "DNSSEC"
14340 If this option is set then lookup results marked with the AA bit
14341 (Authoritative Answer) are trusted the same way as if they were
14342 DNSSEC-verified. The authority section's name of the answer must
14343 match with this expanded domain list.
14345 Use this option only if you talk directly to a resolver that is
14346 authoritative for some zones and does not set the AD (Authentic Data)
14347 bit in the answer. Some DNS servers may have an configuration option to
14348 mark the answers from their own zones as verified (they set the AD bit).
14349 Others do not have this option. It is considered as poor practice using
14350 a resolver that is an authoritative server for some zones.
14352 Use this option only if you really have to (e.g. if you want
14353 to use DANE for remote delivery to a server that is listed in the DNS
14354 zones that your resolver is authoritative for).
14356 If the DNS answer packet has the AA bit set and contains resource record
14357 in the answer section, the name of the first NS record appearing in the
14358 authority section is compared against the list. If the answer packet is
14359 authoritative but the answer section is empty, the name of the first SOA
14360 record in the authoritative section is used instead.
14362 .cindex "DNS" "resolver options"
14363 .option dns_use_edns0 main integer -1
14364 .cindex "DNS" "resolver options"
14365 .cindex "DNS" "EDNS0"
14366 If this option is set to a non-negative number then Exim will initialise the
14367 DNS resolver library to either use or not use EDNS0 extensions, overriding
14368 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
14371 If the resolver library does not support EDNS0 then this option has no effect.
14374 .option drop_cr main boolean false
14375 This is an obsolete option that is now a no-op. It used to affect the way Exim
14376 handled CR and LF characters in incoming messages. What happens now is
14377 described in section &<<SECTlineendings>>&.
14379 .option dsn_advertise_hosts main "host list&!!" unset
14380 .cindex "bounce messages" "success"
14381 .cindex "DSN" "success"
14382 .cindex "Delivery Status Notification" "success"
14383 DSN extensions (RFC3461) will be advertised in the EHLO message to,
14384 and accepted from, these hosts.
14385 Hosts may use the NOTIFY and ENVID options on RCPT TO commands,
14386 and RET and ORCPT options on MAIL FROM commands.
14387 A NOTIFY=SUCCESS option requests success-DSN messages.
14388 A NOTIFY= option with no argument requests that no delay or failure DSNs
14391 .option dsn_from main "string&!!" "see below"
14392 .cindex "&'From:'& header line" "in bounces"
14393 .cindex "bounce messages" "&'From:'& line, specifying"
14394 This option can be used to vary the contents of &'From:'& header lines in
14395 bounces and other automatically generated messages (&"Delivery Status
14396 Notifications"& &-- hence the name of the option). The default setting is:
14398 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
14400 The value is expanded every time it is needed. If the expansion fails, a
14401 panic is logged, and the default value is used.
14403 .option envelope_to_remove main boolean true
14404 .cindex "&'Envelope-to:'& header line"
14405 Exim's transports have an option for adding an &'Envelope-to:'& header to a
14406 message when it is delivered, in exactly the same way as &'Return-path:'& is
14407 handled. &'Envelope-to:'& records the original recipient address from the
14408 message's envelope that caused the delivery to happen. Such headers should not
14409 be present in incoming messages, and this option causes them to be removed at
14410 the time the message is received, to avoid any problems that might occur when a
14411 delivered message is subsequently sent on to some other recipient.
14414 .option errors_copy main "string list&!!" unset
14415 .cindex "bounce message" "copy to other address"
14416 .cindex "copy of bounce message"
14417 Setting this option causes Exim to send bcc copies of bounce messages that it
14418 generates to other addresses. &*Note*&: This does not apply to bounce messages
14419 coming from elsewhere. The value of the option is a colon-separated list of
14420 items. Each item consists of a pattern, terminated by white space, followed by
14421 a comma-separated list of email addresses. If a pattern contains spaces, it
14422 must be enclosed in double quotes.
14424 Each pattern is processed in the same way as a single item in an address list
14425 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
14426 the bounce message, the message is copied to the addresses on the list. The
14427 items are scanned in order, and once a matching one is found, no further items
14428 are examined. For example:
14430 errors_copy = spqr@mydomain postmaster@mydomain.example :\
14431 rqps@mydomain hostmaster@mydomain.example,\
14432 postmaster@mydomain.example
14434 .vindex "&$domain$&"
14435 .vindex "&$local_part$&"
14436 The address list is expanded before use. The expansion variables &$local_part$&
14437 and &$domain$& are set from the original recipient of the error message, and if
14438 there was any wildcard matching in the pattern, the expansion
14439 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
14440 variables &$0$&, &$1$&, etc. are set in the normal way.
14443 .option errors_reply_to main string unset
14444 .cindex "bounce message" "&'Reply-to:'& in"
14445 By default, Exim's bounce and delivery warning messages contain the header line
14447 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
14449 .oindex &%quota_warn_message%&
14450 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
14451 A warning message that is generated by the &%quota_warn_message%& option in an
14452 &(appendfile)& transport may contain its own &'From:'& header line that
14453 overrides the default.
14455 Experience shows that people reply to bounce messages. If the
14456 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
14457 and warning messages. For example:
14459 errors_reply_to = postmaster@my.domain.example
14461 The value of the option is not expanded. It must specify a valid RFC 2822
14462 address. However, if a warning message that is generated by the
14463 &%quota_warn_message%& option in an &(appendfile)& transport contain its
14464 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
14468 .option exim_group main string "compile-time configured"
14469 .cindex "gid (group id)" "Exim's own"
14470 .cindex "Exim group"
14471 This option changes the gid under which Exim runs when it gives up root
14472 privilege. The default value is compiled into the binary. The value of this
14473 option is used only when &%exim_user%& is also set. Unless it consists entirely
14474 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
14475 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
14479 .option exim_path main string "see below"
14480 .cindex "Exim binary, path name"
14481 This option specifies the path name of the Exim binary, which is used when Exim
14482 needs to re-exec itself. The default is set up to point to the file &'exim'& in
14483 the directory configured at compile time by the BIN_DIRECTORY setting. It
14484 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
14486 &*Warning*&: Do not use a macro to define the value of this option, because
14487 you will break those Exim utilities that scan the configuration file to find
14488 where the binary is. (They then use the &%-bP%& option to extract option
14489 settings such as the value of &%spool_directory%&.)
14492 .option exim_user main string "compile-time configured"
14493 .cindex "uid (user id)" "Exim's own"
14494 .cindex "Exim user"
14495 This option changes the uid under which Exim runs when it gives up root
14496 privilege. The default value is compiled into the binary. Ownership of the run
14497 time configuration file and the use of the &%-C%& and &%-D%& command line
14498 options is checked against the values in the binary, not what is set here.
14500 Unless it consists entirely of digits, the string is looked up using
14501 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
14502 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
14503 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
14506 .option extra_local_interfaces main "string list" unset
14507 This option defines network interfaces that are to be considered local when
14508 routing, but which are not used for listening by the daemon. See section
14509 &<<SECTreclocipadd>>& for details.
14512 . Allow this long option name to split; give it unsplit as a fifth argument
14513 . for the automatic .oindex that is generated by .option.
14515 .option "extract_addresses_remove_arguments" main boolean true &&&
14516 extract_addresses_remove_arguments
14518 .cindex "command line" "addresses with &%-t%&"
14519 .cindex "Sendmail compatibility" "&%-t%& option"
14520 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
14521 are present on the command line when the &%-t%& option is used to build an
14522 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
14523 line addresses are removed from the recipients list. This is also how Smail
14524 behaves. However, other Sendmail documentation (the O'Reilly book) states that
14525 command line addresses are added to those obtained from the header lines. When
14526 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
14527 argument headers. If it is set false, Exim adds rather than removes argument
14531 .option finduser_retries main integer 0
14532 .cindex "NIS, retrying user lookups"
14533 On systems running NIS or other schemes in which user and group information is
14534 distributed from a remote system, there can be times when &[getpwnam()]& and
14535 related functions fail, even when given valid data, because things time out.
14536 Unfortunately these failures cannot be distinguished from genuine &"not found"&
14537 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
14538 many extra times to find a user or a group, waiting for one second between
14541 .cindex "&_/etc/passwd_&" "multiple reading of"
14542 You should not set this option greater than zero if your user information is in
14543 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
14544 search the file multiple times for non-existent users, and also cause delay.
14548 .option freeze_tell main "string list, comma separated" unset
14549 .cindex "freezing messages" "sending a message when freezing"
14550 On encountering certain errors, or when configured to do so in a system filter,
14551 ACL, or special router, Exim freezes a message. This means that no further
14552 delivery attempts take place until an administrator thaws the message, or the
14553 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
14554 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
14555 warning message whenever it freezes something, unless the message it is
14556 freezing is a locally-generated bounce message. (Without this exception there
14557 is the possibility of looping.) The warning message is sent to the addresses
14558 supplied as the comma-separated value of this option. If several of the
14559 message's addresses cause freezing, only a single message is sent. If the
14560 freezing was automatic, the reason(s) for freezing can be found in the message
14561 log. If you configure freezing in a filter or ACL, you must arrange for any
14562 logging that you require.
14565 .option gecos_name main string&!! unset
14567 .cindex "&""gecos""& field, parsing"
14568 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
14569 password file to hold other information in addition to users' real names. Exim
14570 looks up this field for use when it is creating &'Sender:'& or &'From:'&
14571 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
14572 of the field are used unchanged, except that, if an ampersand is encountered,
14573 it is replaced by the user's login name with the first character forced to
14574 upper case, since this is a convention that is observed on many systems.
14576 When these options are set, &%gecos_pattern%& is treated as a regular
14577 expression that is to be applied to the field (again with && replaced by the
14578 login name), and if it matches, &%gecos_name%& is expanded and used as the
14581 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
14582 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
14583 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
14584 name terminates at the first comma, the following can be used:
14586 gecos_pattern = ([^,]*)
14590 .option gecos_pattern main string unset
14591 See &%gecos_name%& above.
14594 .option gnutls_compat_mode main boolean unset
14595 This option controls whether GnuTLS is used in compatibility mode in an Exim
14596 server. This reduces security slightly, but improves interworking with older
14597 implementations of TLS.
14600 option gnutls_allow_auto_pkcs11 main boolean unset
14601 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
14602 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
14605 &url(http://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
14610 .option headers_charset main string "see below"
14611 This option sets a default character set for translating from encoded MIME
14612 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
14613 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
14614 ultimate default is ISO-8859-1. For more details see the description of header
14615 insertions in section &<<SECTexpansionitems>>&.
14619 .option header_maxsize main integer "see below"
14620 .cindex "header section" "maximum size of"
14621 .cindex "limit" "size of message header section"
14622 This option controls the overall maximum size of a message's header
14623 section. The default is the value of HEADER_MAXSIZE in
14624 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
14625 sections are rejected.
14628 .option header_line_maxsize main integer 0
14629 .cindex "header lines" "maximum size of"
14630 .cindex "limit" "size of one header line"
14631 This option limits the length of any individual header line in a message, after
14632 all the continuations have been joined together. Messages with individual
14633 header lines that are longer than the limit are rejected. The default value of
14634 zero means &"no limit"&.
14639 .option helo_accept_junk_hosts main "host list&!!" unset
14640 .cindex "HELO" "accepting junk data"
14641 .cindex "EHLO" "accepting junk data"
14642 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
14643 mail, and gives an error response for invalid data. Unfortunately, there are
14644 some SMTP clients that send syntactic junk. They can be accommodated by setting
14645 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
14646 if you want to do semantic checking.
14647 See also &%helo_allow_chars%& for a way of extending the permitted character
14651 .option helo_allow_chars main string unset
14652 .cindex "HELO" "underscores in"
14653 .cindex "EHLO" "underscores in"
14654 .cindex "underscore in EHLO/HELO"
14655 This option can be set to a string of rogue characters that are permitted in
14656 all EHLO and HELO names in addition to the standard letters, digits,
14657 hyphens, and dots. If you really must allow underscores, you can set
14659 helo_allow_chars = _
14661 Note that the value is one string, not a list.
14664 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
14665 .cindex "HELO" "forcing reverse lookup"
14666 .cindex "EHLO" "forcing reverse lookup"
14667 If the domain given by a client in a HELO or EHLO command matches this
14668 list, a reverse lookup is done in order to establish the host's true name. The
14669 default forces a lookup if the client host gives the server's name or any of
14670 its IP addresses (in brackets), something that broken clients have been seen to
14674 .option helo_try_verify_hosts main "host list&!!" unset
14675 .cindex "HELO verifying" "optional"
14676 .cindex "EHLO" "verifying, optional"
14677 By default, Exim just checks the syntax of HELO and EHLO commands (see
14678 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
14679 to do more extensive checking of the data supplied by these commands. The ACL
14680 condition &`verify = helo`& is provided to make this possible.
14681 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
14682 to force the check to occur. From release 4.53 onwards, this is no longer
14683 necessary. If the check has not been done before &`verify = helo`& is
14684 encountered, it is done at that time. Consequently, this option is obsolete.
14685 Its specification is retained here for backwards compatibility.
14687 When an EHLO or HELO command is received, if the calling host matches
14688 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
14689 EHLO command either:
14692 is an IP literal matching the calling address of the host, or
14694 .cindex "DNS" "reverse lookup"
14695 .cindex "reverse DNS lookup"
14696 matches the host name that Exim obtains by doing a reverse lookup of the
14697 calling host address, or
14699 when looked up in DNS yields the calling host address.
14702 However, the EHLO or HELO command is not rejected if any of the checks
14703 fail. Processing continues, but the result of the check is remembered, and can
14704 be detected later in an ACL by the &`verify = helo`& condition.
14706 If DNS was used for successful verification, the variable
14707 .cindex "DNS" "DNSSEC"
14708 &$helo_verify_dnssec$& records the DNSSEC status of the lookups.
14710 .option helo_verify_hosts main "host list&!!" unset
14711 .cindex "HELO verifying" "mandatory"
14712 .cindex "EHLO" "verifying, mandatory"
14713 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
14714 backwards compatibility. For hosts that match this option, Exim checks the host
14715 name given in the HELO or EHLO in the same way as for
14716 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
14717 rejected with a 550 error, and entries are written to the main and reject logs.
14718 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
14721 .option hold_domains main "domain list&!!" unset
14722 .cindex "domain" "delaying delivery"
14723 .cindex "delivery" "delaying certain domains"
14724 This option allows mail for particular domains to be held on the queue
14725 manually. The option is overridden if a message delivery is forced with the
14726 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
14727 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
14728 item in &%hold_domains%&, no routing or delivery for that address is done, and
14729 it is deferred every time the message is looked at.
14731 This option is intended as a temporary operational measure for delaying the
14732 delivery of mail while some problem is being sorted out, or some new
14733 configuration tested. If you just want to delay the processing of some
14734 domains until a queue run occurs, you should use &%queue_domains%& or
14735 &%queue_smtp_domains%&, not &%hold_domains%&.
14737 A setting of &%hold_domains%& does not override Exim's code for removing
14738 messages from the queue if they have been there longer than the longest retry
14739 time in any retry rule. If you want to hold messages for longer than the normal
14740 retry times, insert a dummy retry rule with a long retry time.
14743 .option host_lookup main "host list&!!" unset
14744 .cindex "host name" "lookup, forcing"
14745 Exim does not look up the name of a calling host from its IP address unless it
14746 is required to compare against some host list, or the host matches
14747 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
14748 option (which normally contains IP addresses rather than host names). The
14749 default configuration file contains
14753 which causes a lookup to happen for all hosts. If the expense of these lookups
14754 is felt to be too great, the setting can be changed or removed.
14756 After a successful reverse lookup, Exim does a forward lookup on the name it
14757 has obtained, to verify that it yields the IP address that it started with. If
14758 this check fails, Exim behaves as if the name lookup failed.
14760 .vindex "&$host_lookup_failed$&"
14761 .vindex "&$sender_host_name$&"
14762 After any kind of failure, the host name (in &$sender_host_name$&) remains
14763 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
14764 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
14765 &`verify = reverse_host_lookup`& in ACLs.
14768 .option host_lookup_order main "string list" &`bydns:byaddr`&
14769 This option specifies the order of different lookup methods when Exim is trying
14770 to find a host name from an IP address. The default is to do a DNS lookup
14771 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
14772 if that fails. You can change the order of these lookups, or omit one entirely,
14775 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
14776 multiple PTR records in the DNS and the IP address is not listed in
14777 &_/etc/hosts_&. Different operating systems give different results in this
14778 case. That is why the default tries a DNS lookup first.
14782 .option host_reject_connection main "host list&!!" unset
14783 .cindex "host" "rejecting connections from"
14784 If this option is set, incoming SMTP calls from the hosts listed are rejected
14785 as soon as the connection is made.
14786 This option is obsolete, and retained only for backward compatibility, because
14787 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
14788 connections immediately.
14790 The ability to give an immediate rejection (either by this option or using an
14791 ACL) is provided for use in unusual cases. Many hosts will just try again,
14792 sometimes without much delay. Normally, it is better to use an ACL to reject
14793 incoming messages at a later stage, such as after RCPT commands. See
14794 chapter &<<CHAPACL>>&.
14797 .option hosts_connection_nolog main "host list&!!" unset
14798 .cindex "host" "not logging connections from"
14799 This option defines a list of hosts for which connection logging does not
14800 happen, even though the &%smtp_connection%& log selector is set. For example,
14801 you might want not to log SMTP connections from local processes, or from
14802 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
14803 the daemon; you should therefore strive to restrict its value to a short inline
14804 list of IP addresses and networks. To disable logging SMTP connections from
14805 local processes, you must create a host list with an empty item. For example:
14807 hosts_connection_nolog = :
14809 If the &%smtp_connection%& log selector is not set, this option has no effect.
14813 .option hosts_treat_as_local main "domain list&!!" unset
14814 .cindex "local host" "domains treated as"
14815 .cindex "host" "treated as local"
14816 If this option is set, any host names that match the domain list are treated as
14817 if they were the local host when Exim is scanning host lists obtained from MX
14819 or other sources. Note that the value of this option is a domain list, not a
14820 host list, because it is always used to check host names, not IP addresses.
14822 This option also applies when Exim is matching the special items
14823 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
14824 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
14825 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
14826 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
14827 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
14828 interfaces and recognizing the local host.
14831 .option ibase_servers main "string list" unset
14832 .cindex "InterBase" "server list"
14833 This option provides a list of InterBase servers and associated connection data,
14834 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
14835 The option is available only if Exim has been built with InterBase support.
14839 .option ignore_bounce_errors_after main time 10w
14840 .cindex "bounce message" "discarding"
14841 .cindex "discarding bounce message"
14842 This option affects the processing of bounce messages that cannot be delivered,
14843 that is, those that suffer a permanent delivery failure. (Bounce messages that
14844 suffer temporary delivery failures are of course retried in the usual way.)
14846 After a permanent delivery failure, bounce messages are frozen,
14847 because there is no sender to whom they can be returned. When a frozen bounce
14848 message has been on the queue for more than the given time, it is unfrozen at
14849 the next queue run, and a further delivery is attempted. If delivery fails
14850 again, the bounce message is discarded. This makes it possible to keep failed
14851 bounce messages around for a shorter time than the normal maximum retry time
14852 for frozen messages. For example,
14854 ignore_bounce_errors_after = 12h
14856 retries failed bounce message deliveries after 12 hours, discarding any further
14857 failures. If the value of this option is set to a zero time period, bounce
14858 failures are discarded immediately. Setting a very long time (as in the default
14859 value) has the effect of disabling this option. For ways of automatically
14860 dealing with other kinds of frozen message, see &%auto_thaw%& and
14861 &%timeout_frozen_after%&.
14864 .option ignore_fromline_hosts main "host list&!!" unset
14865 .cindex "&""From""& line"
14866 .cindex "UUCP" "&""From""& line"
14867 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
14868 the headers of a message. By default this is treated as the start of the
14869 message's body, which means that any following headers are not recognized as
14870 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
14871 match those hosts that insist on sending it. If the sender is actually a local
14872 process rather than a remote host, and is using &%-bs%& to inject the messages,
14873 &%ignore_fromline_local%& must be set to achieve this effect.
14876 .option ignore_fromline_local main boolean false
14877 See &%ignore_fromline_hosts%& above.
14880 .option keep_malformed main time 4d
14881 This option specifies the length of time to keep messages whose spool files
14882 have been corrupted in some way. This should, of course, never happen. At the
14883 next attempt to deliver such a message, it gets removed. The incident is
14887 .option ldap_ca_cert_dir main string unset
14888 .cindex "LDAP", "TLS CA certificate directory"
14889 This option indicates which directory contains CA certificates for verifying
14890 a TLS certificate presented by an LDAP server.
14891 While Exim does not provide a default value, your SSL library may.
14892 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
14893 and constrained to be a directory.
14896 .option ldap_ca_cert_file main string unset
14897 .cindex "LDAP", "TLS CA certificate file"
14898 This option indicates which file contains CA certificates for verifying
14899 a TLS certificate presented by an LDAP server.
14900 While Exim does not provide a default value, your SSL library may.
14901 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
14902 and constrained to be a file.
14905 .option ldap_cert_file main string unset
14906 .cindex "LDAP" "TLS client certificate file"
14907 This option indicates which file contains an TLS client certificate which
14908 Exim should present to the LDAP server during TLS negotiation.
14909 Should be used together with &%ldap_cert_key%&.
14912 .option ldap_cert_key main string unset
14913 .cindex "LDAP" "TLS client key file"
14914 This option indicates which file contains the secret/private key to use
14915 to prove identity to the LDAP server during TLS negotiation.
14916 Should be used together with &%ldap_cert_file%&, which contains the
14917 identity to be proven.
14920 .option ldap_cipher_suite main string unset
14921 .cindex "LDAP" "TLS cipher suite"
14922 This controls the TLS cipher-suite negotiation during TLS negotiation with
14923 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
14924 cipher-suite options with OpenSSL (as used by LDAP client libraries).
14927 .option ldap_default_servers main "string list" unset
14928 .cindex "LDAP" "default servers"
14929 This option provides a list of LDAP servers which are tried in turn when an
14930 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
14931 details of LDAP queries. This option is available only when Exim has been built
14935 .option ldap_require_cert main string unset.
14936 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
14937 This should be one of the values "hard", "demand", "allow", "try" or "never".
14938 A value other than one of these is interpreted as "never".
14939 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
14940 Although Exim does not set a default, the LDAP library probably defaults
14944 .option ldap_start_tls main boolean false
14945 .cindex "LDAP" "whether or not to negotiate TLS"
14946 If set, Exim will attempt to negotiate TLS with the LDAP server when
14947 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
14948 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
14950 In the event of failure to negotiate TLS, the action taken is controlled
14951 by &%ldap_require_cert%&.
14954 .option ldap_version main integer unset
14955 .cindex "LDAP" "protocol version, forcing"
14956 This option can be used to force Exim to set a specific protocol version for
14957 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
14958 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
14959 the LDAP headers; otherwise it is 2. This option is available only when Exim
14960 has been built with LDAP support.
14964 .option local_from_check main boolean true
14965 .cindex "&'Sender:'& header line" "disabling addition of"
14966 .cindex "&'From:'& header line" "disabling checking of"
14967 When a message is submitted locally (that is, not over a TCP/IP connection) by
14968 an untrusted user, Exim removes any existing &'Sender:'& header line, and
14969 checks that the &'From:'& header line matches the login of the calling user and
14970 the domain specified by &%qualify_domain%&.
14972 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
14973 locally submitted message is automatically qualified by Exim, unless the
14974 &%-bnq%& command line option is used.
14976 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
14977 on the local part. If the &'From:'& header line does not match, Exim adds a
14978 &'Sender:'& header with an address constructed from the calling user's login
14979 and the default qualify domain.
14981 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
14982 and no &'Sender:'& header is ever added. If, in addition, you want to retain
14983 &'Sender:'& header lines supplied by untrusted users, you must also set
14984 &%local_sender_retain%& to be true.
14986 .cindex "envelope sender"
14987 These options affect only the header lines in the message. The envelope sender
14988 is still forced to be the login id at the qualify domain unless
14989 &%untrusted_set_sender%& permits the user to supply an envelope sender.
14991 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
14992 request similar header line checking. See section &<<SECTthesenhea>>&, which
14993 has more details about &'Sender:'& processing.
14998 .option local_from_prefix main string unset
14999 When Exim checks the &'From:'& header line of locally submitted messages for
15000 matching the login id (see &%local_from_check%& above), it can be configured to
15001 ignore certain prefixes and suffixes in the local part of the address. This is
15002 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
15003 appropriate lists, in the same form as the &%local_part_prefix%& and
15004 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
15007 local_from_prefix = *-
15009 is set, a &'From:'& line containing
15011 From: anything-user@your.domain.example
15013 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
15014 matches the actual sender address that is constructed from the login name and
15018 .option local_from_suffix main string unset
15019 See &%local_from_prefix%& above.
15022 .option local_interfaces main "string list" "see below"
15023 This option controls which network interfaces are used by the daemon for
15024 listening; they are also used to identify the local host when routing. Chapter
15025 &<<CHAPinterfaces>>& contains a full description of this option and the related
15026 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
15027 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
15028 &%local_interfaces%& is
15030 local_interfaces = 0.0.0.0
15032 when Exim is built without IPv6 support; otherwise it is
15034 local_interfaces = <; ::0 ; 0.0.0.0
15037 .option local_scan_timeout main time 5m
15038 .cindex "timeout" "for &[local_scan()]& function"
15039 .cindex "&[local_scan()]& function" "timeout"
15040 This timeout applies to the &[local_scan()]& function (see chapter
15041 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
15042 the incoming message is rejected with a temporary error if it is an SMTP
15043 message. For a non-SMTP message, the message is dropped and Exim ends with a
15044 non-zero code. The incident is logged on the main and reject logs.
15048 .option local_sender_retain main boolean false
15049 .cindex "&'Sender:'& header line" "retaining from local submission"
15050 When a message is submitted locally (that is, not over a TCP/IP connection) by
15051 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
15052 do not want this to happen, you must set &%local_sender_retain%&, and you must
15053 also set &%local_from_check%& to be false (Exim will complain if you do not).
15054 See also the ACL modifier &`control = suppress_local_fixups`&. Section
15055 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
15060 .option localhost_number main string&!! unset
15061 .cindex "host" "locally unique number for"
15062 .cindex "message ids" "with multiple hosts"
15063 .vindex "&$localhost_number$&"
15064 Exim's message ids are normally unique only within the local host. If
15065 uniqueness among a set of hosts is required, each host must set a different
15066 value for the &%localhost_number%& option. The string is expanded immediately
15067 after reading the configuration file (so that a number can be computed from the
15068 host name, for example) and the result of the expansion must be a number in the
15069 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
15070 systems). This is available in subsequent string expansions via the variable
15071 &$localhost_number$&. When &%localhost_number is set%&, the final two
15072 characters of the message id, instead of just being a fractional part of the
15073 time, are computed from the time and the local host number as described in
15074 section &<<SECTmessiden>>&.
15078 .option log_file_path main "string list&!!" "set at compile time"
15079 .cindex "log" "file path for"
15080 This option sets the path which is used to determine the names of Exim's log
15081 files, or indicates that logging is to be to syslog, or both. It is expanded
15082 when Exim is entered, so it can, for example, contain a reference to the host
15083 name. If no specific path is set for the log files at compile or run time,
15084 or if the option is unset at run time (i.e. &`log_file_path = `&)
15085 they are written in a sub-directory called &_log_& in Exim's spool directory.
15086 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
15087 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
15088 used. If this string is fixed at your installation (contains no expansion
15089 variables) it is recommended that you do not set this option in the
15090 configuration file, but instead supply the path using LOG_FILE_PATH in
15091 &_Local/Makefile_& so that it is available to Exim for logging errors detected
15092 early on &-- in particular, failure to read the configuration file.
15095 .option log_selector main string unset
15096 .cindex "log" "selectors"
15097 This option can be used to reduce or increase the number of things that Exim
15098 writes to its log files. Its argument is made up of names preceded by plus or
15099 minus characters. For example:
15101 log_selector = +arguments -retry_defer
15103 A list of possible names and what they control is given in the chapter on
15104 logging, in section &<<SECTlogselector>>&.
15107 .option log_timezone main boolean false
15108 .cindex "log" "timezone for entries"
15109 .vindex "&$tod_log$&"
15110 .vindex "&$tod_zone$&"
15111 By default, the timestamps on log lines are in local time without the
15112 timezone. This means that if your timezone changes twice a year, the timestamps
15113 in log lines are ambiguous for an hour when the clocks go back. One way of
15114 avoiding this problem is to set the timezone to UTC. An alternative is to set
15115 &%log_timezone%& true. This turns on the addition of the timezone offset to
15116 timestamps in log lines. Turning on this option can add quite a lot to the size
15117 of log files because each line is extended by 6 characters. Note that the
15118 &$tod_log$& variable contains the log timestamp without the zone, but there is
15119 another variable called &$tod_zone$& that contains just the timezone offset.
15122 .option lookup_open_max main integer 25
15123 .cindex "too many open files"
15124 .cindex "open files, too many"
15125 .cindex "file" "too many open"
15126 .cindex "lookup" "maximum open files"
15127 .cindex "limit" "open files for lookups"
15128 This option limits the number of simultaneously open files for single-key
15129 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
15130 Exim normally keeps these files open during routing, because often the same
15131 file is required several times. If the limit is reached, Exim closes the least
15132 recently used file. Note that if you are using the &'ndbm'& library, it
15133 actually opens two files for each logical DBM database, though it still counts
15134 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
15135 open files"& errors with NDBM, you need to reduce the value of
15136 &%lookup_open_max%&.
15139 .option max_username_length main integer 0
15140 .cindex "length of login name"
15141 .cindex "user name" "maximum length"
15142 .cindex "limit" "user name length"
15143 Some operating systems are broken in that they truncate long arguments to
15144 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
15145 this option is set greater than zero, any attempt to call &[getpwnam()]& with
15146 an argument that is longer behaves as if &[getpwnam()]& failed.
15149 .option message_body_newlines main bool false
15150 .cindex "message body" "newlines in variables"
15151 .cindex "newline" "in message body variables"
15152 .vindex "&$message_body$&"
15153 .vindex "&$message_body_end$&"
15154 By default, newlines in the message body are replaced by spaces when setting
15155 the &$message_body$& and &$message_body_end$& expansion variables. If this
15156 option is set true, this no longer happens.
15159 .option message_body_visible main integer 500
15160 .cindex "body of message" "visible size"
15161 .cindex "message body" "visible size"
15162 .vindex "&$message_body$&"
15163 .vindex "&$message_body_end$&"
15164 This option specifies how much of a message's body is to be included in the
15165 &$message_body$& and &$message_body_end$& expansion variables.
15168 .option message_id_header_domain main string&!! unset
15169 .cindex "&'Message-ID:'& header line"
15170 If this option is set, the string is expanded and used as the right hand side
15171 (domain) of the &'Message-ID:'& header that Exim creates if a
15172 locally-originated incoming message does not have one. &"Locally-originated"&
15173 means &"not received over TCP/IP."&
15174 Otherwise, the primary host name is used.
15175 Only letters, digits, dot and hyphen are accepted; any other characters are
15176 replaced by hyphens. If the expansion is forced to fail, or if the result is an
15177 empty string, the option is ignored.
15180 .option message_id_header_text main string&!! unset
15181 If this variable is set, the string is expanded and used to augment the text of
15182 the &'Message-id:'& header that Exim creates if a locally-originated incoming
15183 message does not have one. The text of this header is required by RFC 2822 to
15184 take the form of an address. By default, Exim uses its internal message id as
15185 the local part, and the primary host name as the domain. If this option is set,
15186 it is expanded, and provided the expansion is not forced to fail, and does not
15187 yield an empty string, the result is inserted into the header immediately
15188 before the @, separated from the internal message id by a dot. Any characters
15189 that are illegal in an address are automatically converted into hyphens. This
15190 means that variables such as &$tod_log$& can be used, because the spaces and
15191 colons will become hyphens.
15194 .option message_logs main boolean true
15195 .cindex "message logs" "disabling"
15196 .cindex "log" "message log; disabling"
15197 If this option is turned off, per-message log files are not created in the
15198 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
15199 Exim, by reducing the number of files involved in handling a message from a
15200 minimum of four (header spool file, body spool file, delivery journal, and
15201 per-message log) to three. The other major I/O activity is Exim's main log,
15202 which is not affected by this option.
15205 .option message_size_limit main string&!! 50M
15206 .cindex "message" "size limit"
15207 .cindex "limit" "message size"
15208 .cindex "size" "of message, limit"
15209 This option limits the maximum size of message that Exim will process. The
15210 value is expanded for each incoming connection so, for example, it can be made
15211 to depend on the IP address of the remote host for messages arriving via
15212 TCP/IP. After expansion, the value must be a sequence of decimal digits,
15213 optionally followed by K or M.
15215 &*Note*&: This limit cannot be made to depend on a message's sender or any
15216 other properties of an individual message, because it has to be advertised in
15217 the server's response to EHLO. String expansion failure causes a temporary
15218 error. A value of zero means no limit, but its use is not recommended. See also
15219 &%bounce_return_size_limit%&.
15221 Incoming SMTP messages are failed with a 552 error if the limit is
15222 exceeded; locally-generated messages either get a stderr message or a delivery
15223 failure message to the sender, depending on the &%-oe%& setting. Rejection of
15224 an oversized message is logged in both the main and the reject logs. See also
15225 the generic transport option &%message_size_limit%&, which limits the size of
15226 message that an individual transport can process.
15228 If you use a virus-scanner and set this option to to a value larger than the
15229 maximum size that your virus-scanner is configured to support, you may get
15230 failures triggered by large mails. The right size to configure for the
15231 virus-scanner depends upon what data is passed and the options in use but it's
15232 probably safest to just set it to a little larger than this value. E.g., with a
15233 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
15234 some problems may result.
15236 A value of 0 will disable size limit checking; Exim will still advertise the
15237 SIZE extension in an EHLO response, but without a limit, so as to permit
15238 SMTP clients to still indicate the message size along with the MAIL verb.
15241 .option move_frozen_messages main boolean false
15242 .cindex "frozen messages" "moving"
15243 This option, which is available only if Exim has been built with the setting
15245 SUPPORT_MOVE_FROZEN_MESSAGES=yes
15247 in &_Local/Makefile_&, causes frozen messages and their message logs to be
15248 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
15249 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
15250 standard utilities for handling such moved messages, and they do not show up in
15251 lists generated by &%-bp%& or by the Exim monitor.
15254 .option mua_wrapper main boolean false
15255 Setting this option true causes Exim to run in a very restrictive mode in which
15256 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
15257 contains a full description of this facility.
15261 .option mysql_servers main "string list" unset
15262 .cindex "MySQL" "server list"
15263 This option provides a list of MySQL servers and associated connection data, to
15264 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
15265 option is available only if Exim has been built with MySQL support.
15268 .option never_users main "string list&!!" unset
15269 This option is expanded just once, at the start of Exim's processing. Local
15270 message deliveries are normally run in processes that are setuid to the
15271 recipient, and remote deliveries are normally run under Exim's own uid and gid.
15272 It is usually desirable to prevent any deliveries from running as root, as a
15275 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
15276 list of users that must not be used for local deliveries. This list is fixed in
15277 the binary and cannot be overridden by the configuration file. By default, it
15278 contains just the single user name &"root"&. The &%never_users%& runtime option
15279 can be used to add more users to the fixed list.
15281 If a message is to be delivered as one of the users on the fixed list or the
15282 &%never_users%& list, an error occurs, and delivery is deferred. A common
15285 never_users = root:daemon:bin
15287 Including root is redundant if it is also on the fixed list, but it does no
15288 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
15292 .option openssl_options main "string list" "+no_sslv2"
15293 .cindex "OpenSSL "compatibility options"
15294 This option allows an administrator to adjust the SSL options applied
15295 by OpenSSL to connections. It is given as a space-separated list of items,
15296 each one to be +added or -subtracted from the current value.
15298 This option is only available if Exim is built against OpenSSL. The values
15299 available for this option vary according to the age of your OpenSSL install.
15300 The &"all"& value controls a subset of flags which are available, typically
15301 the bug workaround options. The &'SSL_CTX_set_options'& man page will
15302 list the values known on your system and Exim should support all the
15303 &"bug workaround"& options and many of the &"modifying"& options. The Exim
15304 names lose the leading &"SSL_OP_"& and are lower-cased.
15306 Note that adjusting the options can have severe impact upon the security of
15307 SSL as used by Exim. It is possible to disable safety checks and shoot
15308 yourself in the foot in various unpleasant ways. This option should not be
15309 adjusted lightly. An unrecognised item will be detected at startup, by
15310 invoking Exim with the &%-bV%& flag.
15312 The option affects Exim operating both as a server and as a client.
15314 Historical note: prior to release 4.80, Exim defaulted this value to
15315 "+dont_insert_empty_fragments", which may still be needed for compatibility
15316 with some clients, but which lowers security by increasing exposure to
15317 some now infamous attacks.
15321 # Make both old MS and old Eudora happy:
15322 openssl_options = -all +microsoft_big_sslv3_buffer \
15323 +dont_insert_empty_fragments
15325 # Disable older protocol versions:
15326 openssl_options = +no_sslv2 +no_sslv3
15329 Possible options may include:
15333 &`allow_unsafe_legacy_renegotiation`&
15335 &`cipher_server_preference`&
15337 &`dont_insert_empty_fragments`&
15341 &`legacy_server_connect`&
15343 &`microsoft_big_sslv3_buffer`&
15345 &`microsoft_sess_id_bug`&
15347 &`msie_sslv2_rsa_padding`&
15349 &`netscape_challenge_bug`&
15351 &`netscape_reuse_cipher_change_bug`&
15355 &`no_session_resumption_on_renegotiation`&
15369 &`safari_ecdhe_ecdsa_bug`&
15373 &`single_ecdh_use`&
15375 &`ssleay_080_client_dh_bug`&
15377 &`sslref2_reuse_cert_type_bug`&
15379 &`tls_block_padding_bug`&
15383 &`tls_rollback_bug`&
15386 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
15387 all clients connecting using the MacOS SecureTransport TLS facility prior
15388 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
15389 to negotiate TLS then this option value might help, provided that your OpenSSL
15390 release is new enough to contain this work-around. This may be a situation
15391 where you have to upgrade OpenSSL to get buggy clients working.
15394 .option oracle_servers main "string list" unset
15395 .cindex "Oracle" "server list"
15396 This option provides a list of Oracle servers and associated connection data,
15397 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
15398 The option is available only if Exim has been built with Oracle support.
15401 .option percent_hack_domains main "domain list&!!" unset
15402 .cindex "&""percent hack""&"
15403 .cindex "source routing" "in email address"
15404 .cindex "address" "source-routed"
15405 The &"percent hack"& is the convention whereby a local part containing a
15406 percent sign is re-interpreted as a new email address, with the percent
15407 replaced by @. This is sometimes called &"source routing"&, though that term is
15408 also applied to RFC 2822 addresses that begin with an @ character. If this
15409 option is set, Exim implements the percent facility for those domains listed,
15410 but no others. This happens before an incoming SMTP address is tested against
15413 &*Warning*&: The &"percent hack"& has often been abused by people who are
15414 trying to get round relaying restrictions. For this reason, it is best avoided
15415 if at all possible. Unfortunately, a number of less security-conscious MTAs
15416 implement it unconditionally. If you are running Exim on a gateway host, and
15417 routing mail through to internal MTAs without processing the local parts, it is
15418 a good idea to reject recipient addresses with percent characters in their
15419 local parts. Exim's default configuration does this.
15422 .option perl_at_start main boolean false
15423 This option is available only when Exim is built with an embedded Perl
15424 interpreter. See chapter &<<CHAPperl>>& for details of its use.
15427 .option perl_startup main string unset
15428 This option is available only when Exim is built with an embedded Perl
15429 interpreter. See chapter &<<CHAPperl>>& for details of its use.
15432 .option pgsql_servers main "string list" unset
15433 .cindex "PostgreSQL lookup type" "server list"
15434 This option provides a list of PostgreSQL servers and associated connection
15435 data, to be used in conjunction with &(pgsql)& lookups (see section
15436 &<<SECID72>>&). The option is available only if Exim has been built with
15437 PostgreSQL support.
15440 .option pid_file_path main string&!! "set at compile time"
15441 .cindex "daemon" "pid file path"
15442 .cindex "pid file, path for"
15443 This option sets the name of the file to which the Exim daemon writes its
15444 process id. The string is expanded, so it can contain, for example, references
15447 pid_file_path = /var/log/$primary_hostname/exim.pid
15449 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
15451 The value set by the option can be overridden by the &%-oP%& command line
15452 option. A pid file is not written if a &"non-standard"& daemon is run by means
15453 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
15456 .option pipelining_advertise_hosts main "host list&!!" *
15457 .cindex "PIPELINING" "suppressing advertising"
15458 This option can be used to suppress the advertisement of the SMTP
15459 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
15460 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
15461 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
15462 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
15463 that clients will use it; &"out of order"& commands that are &"expected"& do
15464 not count as protocol errors (see &%smtp_max_synprot_errors%&).
15467 .option prdr_enable main boolean false
15468 .cindex "PRDR" "enabling on server"
15469 This option can be used to enable the Per-Recipient Data Response extension
15470 to SMTP, defined by Eric Hall.
15471 If the option is set, PRDR is advertised by Exim when operating as a server.
15472 If the client requests PRDR, and more than one recipient, for a message
15473 an additional ACL is called for each recipient after the message content
15474 is received. See section &<<SECTPRDRACL>>&.
15476 .option preserve_message_logs main boolean false
15477 .cindex "message logs" "preserving"
15478 If this option is set, message log files are not deleted when messages are
15479 completed. Instead, they are moved to a sub-directory of the spool directory
15480 called &_msglog.OLD_&, where they remain available for statistical or debugging
15481 purposes. This is a dangerous option to set on systems with any appreciable
15482 volume of mail. Use with care!
15485 .option primary_hostname main string "see below"
15486 .cindex "name" "of local host"
15487 .cindex "host" "name of local"
15488 .cindex "local host" "name of"
15489 .vindex "&$primary_hostname$&"
15490 This specifies the name of the current host. It is used in the default EHLO or
15491 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
15492 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
15493 The value is also used by default in some SMTP response messages from an Exim
15494 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
15496 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
15497 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
15498 contains only one component, Exim passes it to &[gethostbyname()]& (or
15499 &[getipnodebyname()]& when available) in order to obtain the fully qualified
15500 version. The variable &$primary_hostname$& contains the host name, whether set
15501 explicitly by this option, or defaulted.
15504 .option print_topbitchars main boolean false
15505 .cindex "printing characters"
15506 .cindex "8-bit characters"
15507 By default, Exim considers only those characters whose codes lie in the range
15508 32&--126 to be printing characters. In a number of circumstances (for example,
15509 when writing log entries) non-printing characters are converted into escape
15510 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
15511 is set, code values of 128 and above are also considered to be printing
15514 This option also affects the header syntax checks performed by the
15515 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
15516 the user's full name when constructing From: and Sender: addresses (as
15517 described in section &<<SECTconstr>>&). Setting this option can cause
15518 Exim to generate eight bit message headers that do not conform to the
15522 .option process_log_path main string unset
15523 .cindex "process log path"
15524 .cindex "log" "process log"
15525 .cindex "&'exiwhat'&"
15526 This option sets the name of the file to which an Exim process writes its
15527 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
15528 utility script. If this option is unset, the file called &_exim-process.info_&
15529 in Exim's spool directory is used. The ability to specify the name explicitly
15530 can be useful in environments where two different Exims are running, using
15531 different spool directories.
15534 .option prod_requires_admin main boolean true
15538 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
15539 admin user unless &%prod_requires_admin%& is set false. See also
15540 &%queue_list_requires_admin%&.
15543 .option qualify_domain main string "see below"
15544 .cindex "domain" "for qualifying addresses"
15545 .cindex "address" "qualification"
15546 This option specifies the domain name that is added to any envelope sender
15547 addresses that do not have a domain qualification. It also applies to
15548 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
15549 are accepted by default only for locally-generated messages. Qualification is
15550 also applied to addresses in header lines such as &'From:'& and &'To:'& for
15551 locally-generated messages, unless the &%-bnq%& command line option is used.
15553 Messages from external sources must always contain fully qualified addresses,
15554 unless the sending host matches &%sender_unqualified_hosts%& or
15555 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
15556 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
15557 necessary. Internally, Exim always works with fully qualified envelope
15558 addresses. If &%qualify_domain%& is not set, it defaults to the
15559 &%primary_hostname%& value.
15562 .option qualify_recipient main string "see below"
15563 This option allows you to specify a different domain for qualifying recipient
15564 addresses to the one that is used for senders. See &%qualify_domain%& above.
15568 .option queue_domains main "domain list&!!" unset
15569 .cindex "domain" "specifying non-immediate delivery"
15570 .cindex "queueing incoming messages"
15571 .cindex "message" "queueing certain domains"
15572 This option lists domains for which immediate delivery is not required.
15573 A delivery process is started whenever a message is received, but only those
15574 domains that do not match are processed. All other deliveries wait until the
15575 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
15578 .option queue_list_requires_admin main boolean true
15580 The &%-bp%& command-line option, which lists the messages that are on the
15581 queue, requires the caller to be an admin user unless
15582 &%queue_list_requires_admin%& is set false. See also &%prod_requires_admin%&.
15585 .option queue_only main boolean false
15586 .cindex "queueing incoming messages"
15587 .cindex "message" "queueing unconditionally"
15588 If &%queue_only%& is set, a delivery process is not automatically started
15589 whenever a message is received. Instead, the message waits on the queue for the
15590 next queue run. Even if &%queue_only%& is false, incoming messages may not get
15591 delivered immediately when certain conditions (such as heavy load) occur.
15593 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
15594 and &%-odi%& command line options override &%queue_only%& unless
15595 &%queue_only_override%& is set false. See also &%queue_only_file%&,
15596 &%queue_only_load%&, and &%smtp_accept_queue%&.
15599 .option queue_only_file main string unset
15600 .cindex "queueing incoming messages"
15601 .cindex "message" "queueing by file existence"
15602 This option can be set to a colon-separated list of absolute path names, each
15603 one optionally preceded by &"smtp"&. When Exim is receiving a message,
15604 it tests for the existence of each listed path using a call to &[stat()]&. For
15605 each path that exists, the corresponding queueing option is set.
15606 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
15607 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
15609 queue_only_file = smtp/some/file
15611 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
15612 &_/some/file_& exists.
15615 .option queue_only_load main fixed-point unset
15616 .cindex "load average"
15617 .cindex "queueing incoming messages"
15618 .cindex "message" "queueing by load"
15619 If the system load average is higher than this value, incoming messages from
15620 all sources are queued, and no automatic deliveries are started. If this
15621 happens during local or remote SMTP input, all subsequent messages received on
15622 the same SMTP connection are queued by default, whatever happens to the load in
15623 the meantime, but this can be changed by setting &%queue_only_load_latch%&
15626 Deliveries will subsequently be performed by queue runner processes. This
15627 option has no effect on ancient operating systems on which Exim cannot
15628 determine the load average. See also &%deliver_queue_load_max%& and
15629 &%smtp_load_reserve%&.
15632 .option queue_only_load_latch main boolean true
15633 .cindex "load average" "re-evaluating per message"
15634 When this option is true (the default), once one message has been queued
15635 because the load average is higher than the value set by &%queue_only_load%&,
15636 all subsequent messages received on the same SMTP connection are also queued.
15637 This is a deliberate choice; even though the load average may fall below the
15638 threshold, it doesn't seem right to deliver later messages on the same
15639 connection when not delivering earlier ones. However, there are special
15640 circumstances such as very long-lived connections from scanning appliances
15641 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
15642 should be set false. This causes the value of the load average to be
15643 re-evaluated for each message.
15646 .option queue_only_override main boolean true
15647 .cindex "queueing incoming messages"
15648 When this option is true, the &%-od%&&'x'& command line options override the
15649 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
15650 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
15651 to override; they are accepted, but ignored.
15654 .option queue_run_in_order main boolean false
15655 .cindex "queue runner" "processing messages in order"
15656 If this option is set, queue runs happen in order of message arrival instead of
15657 in an arbitrary order. For this to happen, a complete list of the entire queue
15658 must be set up before the deliveries start. When the queue is all held in a
15659 single directory (the default), a single list is created for both the ordered
15660 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
15661 single list is not created when &%queue_run_in_order%& is false. In this case,
15662 the sub-directories are processed one at a time (in a random order), and this
15663 avoids setting up one huge list for the whole queue. Thus, setting
15664 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
15665 when the queue is large, because of the extra work in setting up the single,
15666 large list. In most situations, &%queue_run_in_order%& should not be set.
15670 .option queue_run_max main integer 5
15671 .cindex "queue runner" "maximum number of"
15672 This controls the maximum number of queue runner processes that an Exim daemon
15673 can run simultaneously. This does not mean that it starts them all at once,
15674 but rather that if the maximum number are still running when the time comes to
15675 start another one, it refrains from starting another one. This can happen with
15676 very large queues and/or very sluggish deliveries. This option does not,
15677 however, interlock with other processes, so additional queue runners can be
15678 started by other means, or by killing and restarting the daemon.
15680 Setting this option to zero does not suppress queue runs; rather, it disables
15681 the limit, allowing any number of simultaneous queue runner processes to be
15682 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
15683 the daemon's command line.
15685 .option queue_smtp_domains main "domain list&!!" unset
15686 .cindex "queueing incoming messages"
15687 .cindex "message" "queueing remote deliveries"
15688 When this option is set, a delivery process is started whenever a message is
15689 received, routing is performed, and local deliveries take place.
15690 However, if any SMTP deliveries are required for domains that match
15691 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
15692 message waits on the queue for the next queue run. Since routing of the message
15693 has taken place, Exim knows to which remote hosts it must be delivered, and so
15694 when the queue run happens, multiple messages for the same host are delivered
15695 over a single SMTP connection. The &%-odqs%& command line option causes all
15696 SMTP deliveries to be queued in this way, and is equivalent to setting
15697 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
15701 .option receive_timeout main time 0s
15702 .cindex "timeout" "for non-SMTP input"
15703 This option sets the timeout for accepting a non-SMTP message, that is, the
15704 maximum time that Exim waits when reading a message on the standard input. If
15705 the value is zero, it will wait for ever. This setting is overridden by the
15706 &%-or%& command line option. The timeout for incoming SMTP messages is
15707 controlled by &%smtp_receive_timeout%&.
15709 .option received_header_text main string&!! "see below"
15710 .cindex "customizing" "&'Received:'& header"
15711 .cindex "&'Received:'& header line" "customizing"
15712 This string defines the contents of the &'Received:'& message header that is
15713 added to each message, except for the timestamp, which is automatically added
15714 on at the end (preceded by a semicolon). The string is expanded each time it is
15715 used. If the expansion yields an empty string, no &'Received:'& header line is
15716 added to the message. Otherwise, the string should start with the text
15717 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
15718 header lines. The default setting is:
15721 received_header_text = Received: \
15722 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
15723 {${if def:sender_ident \
15724 {from ${quote_local_part:$sender_ident} }}\
15725 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
15726 by $primary_hostname \
15727 ${if def:received_protocol {with $received_protocol}} \
15728 ${if def:tls_in_cipher {($tls_in_cipher)\n\t}}\
15729 (Exim $version_number)\n\t\
15730 ${if def:sender_address \
15731 {(envelope-from <$sender_address>)\n\t}}\
15732 id $message_exim_id\
15733 ${if def:received_for {\n\tfor $received_for}}
15736 The reference to the TLS cipher is omitted when Exim is built without TLS
15737 support. The use of conditional expansions ensures that this works for both
15738 locally generated messages and messages received from remote hosts, giving
15739 header lines such as the following:
15741 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
15742 by marley.carol.example with esmtp (Exim 4.00)
15743 (envelope-from <bob@carol.example>)
15744 id 16IOWa-00019l-00
15745 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
15746 Received: by scrooge.carol.example with local (Exim 4.00)
15747 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
15749 Until the body of the message has been received, the timestamp is the time when
15750 the message started to be received. Once the body has arrived, and all policy
15751 checks have taken place, the timestamp is updated to the time at which the
15752 message was accepted.
15755 .option received_headers_max main integer 30
15756 .cindex "loop" "prevention"
15757 .cindex "mail loop prevention"
15758 .cindex "&'Received:'& header line" "counting"
15759 When a message is to be delivered, the number of &'Received:'& headers is
15760 counted, and if it is greater than this parameter, a mail loop is assumed to
15761 have occurred, the delivery is abandoned, and an error message is generated.
15762 This applies to both local and remote deliveries.
15765 .option recipient_unqualified_hosts main "host list&!!" unset
15766 .cindex "unqualified addresses"
15767 .cindex "host" "unqualified addresses from"
15768 This option lists those hosts from which Exim is prepared to accept unqualified
15769 recipient addresses in message envelopes. The addresses are made fully
15770 qualified by the addition of the &%qualify_recipient%& value. This option also
15771 affects message header lines. Exim does not reject unqualified recipient
15772 addresses in headers, but it qualifies them only if the message came from a
15773 host that matches &%recipient_unqualified_hosts%&,
15774 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
15775 option was not set.
15778 .option recipients_max main integer 0
15779 .cindex "limit" "number of recipients"
15780 .cindex "recipient" "maximum number"
15781 If this option is set greater than zero, it specifies the maximum number of
15782 original recipients for any message. Additional recipients that are generated
15783 by aliasing or forwarding do not count. SMTP messages get a 452 response for
15784 all recipients over the limit; earlier recipients are delivered as normal.
15785 Non-SMTP messages with too many recipients are failed, and no deliveries are
15788 .cindex "RCPT" "maximum number of incoming"
15789 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
15790 RCPT commands in a single message.
15793 .option recipients_max_reject main boolean false
15794 If this option is set true, Exim rejects SMTP messages containing too many
15795 recipients by giving 552 errors to the surplus RCPT commands, and a 554
15796 error to the eventual DATA command. Otherwise (the default) it gives a 452
15797 error to the surplus RCPT commands and accepts the message on behalf of the
15798 initial set of recipients. The remote server should then re-send the message
15799 for the remaining recipients at a later time.
15802 .option remote_max_parallel main integer 2
15803 .cindex "delivery" "parallelism for remote"
15804 This option controls parallel delivery of one message to a number of remote
15805 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
15806 does all the remote deliveries for a message one by one. Otherwise, if a single
15807 message has to be delivered to more than one remote host, or if several copies
15808 have to be sent to the same remote host, up to &%remote_max_parallel%&
15809 deliveries are done simultaneously. If more than &%remote_max_parallel%&
15810 deliveries are required, the maximum number of processes are started, and as
15811 each one finishes, another is begun. The order of starting processes is the
15812 same as if sequential delivery were being done, and can be controlled by the
15813 &%remote_sort_domains%& option. If parallel delivery takes place while running
15814 with debugging turned on, the debugging output from each delivery process is
15815 tagged with its process id.
15817 This option controls only the maximum number of parallel deliveries for one
15818 message in one Exim delivery process. Because Exim has no central queue
15819 manager, there is no way of controlling the total number of simultaneous
15820 deliveries if the configuration allows a delivery attempt as soon as a message
15823 .cindex "number of deliveries"
15824 .cindex "delivery" "maximum number of"
15825 If you want to control the total number of deliveries on the system, you
15826 need to set the &%queue_only%& option. This ensures that all incoming messages
15827 are added to the queue without starting a delivery process. Then set up an Exim
15828 daemon to start queue runner processes at appropriate intervals (probably
15829 fairly often, for example, every minute), and limit the total number of queue
15830 runners by setting the &%queue_run_max%& parameter. Because each queue runner
15831 delivers only one message at a time, the maximum number of deliveries that can
15832 then take place at once is &%queue_run_max%& multiplied by
15833 &%remote_max_parallel%&.
15835 If it is purely remote deliveries you want to control, use
15836 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
15837 doing the SMTP routing before queueing, so that several messages for the same
15838 host will eventually get delivered down the same connection.
15841 .option remote_sort_domains main "domain list&!!" unset
15842 .cindex "sorting remote deliveries"
15843 .cindex "delivery" "sorting remote"
15844 When there are a number of remote deliveries for a message, they are sorted by
15845 domain into the order given by this list. For example,
15847 remote_sort_domains = *.cam.ac.uk:*.uk
15849 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
15850 then to those in the &%uk%& domain, then to any others.
15853 .option retry_data_expire main time 7d
15854 .cindex "hints database" "data expiry"
15855 This option sets a &"use before"& time on retry information in Exim's hints
15856 database. Any older retry data is ignored. This means that, for example, once a
15857 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
15861 .option retry_interval_max main time 24h
15862 .cindex "retry" "limit on interval"
15863 .cindex "limit" "on retry interval"
15864 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
15865 intervals between delivery attempts for messages that cannot be delivered
15866 straight away. This option sets an overall limit to the length of time between
15867 retries. It cannot be set greater than 24 hours; any attempt to do so forces
15871 .option return_path_remove main boolean true
15872 .cindex "&'Return-path:'& header line" "removing"
15873 RFC 2821, section 4.4, states that an SMTP server must insert a
15874 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
15875 The &'Return-path:'& header preserves the sender address as received in the
15876 MAIL command. This description implies that this header should not be present
15877 in an incoming message. If &%return_path_remove%& is true, any existing
15878 &'Return-path:'& headers are removed from messages at the time they are
15879 received. Exim's transports have options for adding &'Return-path:'& headers at
15880 the time of delivery. They are normally used only for final local deliveries.
15883 .option return_size_limit main integer 100K
15884 This option is an obsolete synonym for &%bounce_return_size_limit%&.
15887 .option rfc1413_hosts main "host list&!!" @[]
15889 .cindex "host" "for RFC 1413 calls"
15890 RFC 1413 identification calls are made to any client host which matches
15891 an item in the list.
15892 The default value specifies just this host, being any local interface
15895 .option rfc1413_query_timeout main time 0s
15896 .cindex "RFC 1413" "query timeout"
15897 .cindex "timeout" "for RFC 1413 call"
15898 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
15899 no RFC 1413 calls are ever made.
15902 .option sender_unqualified_hosts main "host list&!!" unset
15903 .cindex "unqualified addresses"
15904 .cindex "host" "unqualified addresses from"
15905 This option lists those hosts from which Exim is prepared to accept unqualified
15906 sender addresses. The addresses are made fully qualified by the addition of
15907 &%qualify_domain%&. This option also affects message header lines. Exim does
15908 not reject unqualified addresses in headers that contain sender addresses, but
15909 it qualifies them only if the message came from a host that matches
15910 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
15911 using TCP/IP), and the &%-bnq%& option was not set.
15914 .option slow_lookup_log main integer 0
15915 .cindex "logging" "slow lookups"
15916 .cindex "dns" "logging slow lookups"
15917 This option controls logging of slow lookups.
15918 If the value is nonzero it is taken as a number of milliseconds
15919 and lookups taking longer than this are logged.
15920 Currently this applies only to DNS lookups.
15924 .option smtp_accept_keepalive main boolean true
15925 .cindex "keepalive" "on incoming connection"
15926 This option controls the setting of the SO_KEEPALIVE option on incoming
15927 TCP/IP socket connections. When set, it causes the kernel to probe idle
15928 connections periodically, by sending packets with &"old"& sequence numbers. The
15929 other end of the connection should send an acknowledgment if the connection is
15930 still okay or a reset if the connection has been aborted. The reason for doing
15931 this is that it has the beneficial effect of freeing up certain types of
15932 connection that can get stuck when the remote host is disconnected without
15933 tidying up the TCP/IP call properly. The keepalive mechanism takes several
15934 hours to detect unreachable hosts.
15938 .option smtp_accept_max main integer 20
15939 .cindex "limit" "incoming SMTP connections"
15940 .cindex "SMTP" "incoming connection count"
15942 This option specifies the maximum number of simultaneous incoming SMTP calls
15943 that Exim will accept. It applies only to the listening daemon; there is no
15944 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
15945 value is set to zero, no limit is applied. However, it is required to be
15946 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
15947 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
15949 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
15950 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
15951 that limit has not been reached for the client host, &%smtp_accept_reserve%&
15952 and &%smtp_load_reserve%& are then checked before accepting the connection.
15955 .option smtp_accept_max_nonmail main integer 10
15956 .cindex "limit" "non-mail SMTP commands"
15957 .cindex "SMTP" "limiting non-mail commands"
15958 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
15959 the connection if there are too many. This option defines &"too many"&. The
15960 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
15961 client looping sending EHLO, for example. The check is applied only if the
15962 client host matches &%smtp_accept_max_nonmail_hosts%&.
15964 When a new message is expected, one occurrence of RSET is not counted. This
15965 allows a client to send one RSET between messages (this is not necessary,
15966 but some clients do it). Exim also allows one uncounted occurrence of HELO
15967 or EHLO, and one occurrence of STARTTLS between messages. After
15968 starting up a TLS session, another EHLO is expected, and so it too is not
15969 counted. The first occurrence of AUTH in a connection, or immediately
15970 following STARTTLS is not counted. Otherwise, all commands other than
15971 MAIL, RCPT, DATA, and QUIT are counted.
15974 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
15975 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
15976 check by setting this option. The default value makes it apply to all hosts. By
15977 changing the value, you can exclude any badly-behaved hosts that you have to
15981 . Allow this long option name to split; give it unsplit as a fifth argument
15982 . for the automatic .oindex that is generated by .option.
15983 . We insert " &~&~" which is both pretty nasty visually and results in
15984 . non-searchable text. HowItWorks.txt mentions an option for inserting
15985 . zero-width-space, which would be nicer visually and results in (at least)
15986 . html that Firefox will split on when it's forced to reflow (rather than
15987 . inserting a horizontal scrollbar). However, the text is still not
15988 . searchable. NM changed this occurrence for bug 1197 to no longer allow
15989 . the option name to split.
15991 .option "smtp_accept_max_per_connection" main integer 1000 &&&
15992 smtp_accept_max_per_connection
15993 .cindex "SMTP" "limiting incoming message count"
15994 .cindex "limit" "messages per SMTP connection"
15995 The value of this option limits the number of MAIL commands that Exim is
15996 prepared to accept over a single SMTP connection, whether or not each command
15997 results in the transfer of a message. After the limit is reached, a 421
15998 response is given to subsequent MAIL commands. This limit is a safety
15999 precaution against a client that goes mad (incidents of this type have been
16003 .option smtp_accept_max_per_host main string&!! unset
16004 .cindex "limit" "SMTP connections from one host"
16005 .cindex "host" "limiting SMTP connections from"
16006 This option restricts the number of simultaneous IP connections from a single
16007 host (strictly, from a single IP address) to the Exim daemon. The option is
16008 expanded, to enable different limits to be applied to different hosts by
16009 reference to &$sender_host_address$&. Once the limit is reached, additional
16010 connection attempts from the same host are rejected with error code 421. This
16011 is entirely independent of &%smtp_accept_reserve%&. The option's default value
16012 of zero imposes no limit. If this option is set greater than zero, it is
16013 required that &%smtp_accept_max%& be non-zero.
16015 &*Warning*&: When setting this option you should not use any expansion
16016 constructions that take an appreciable amount of time. The expansion and test
16017 happen in the main daemon loop, in order to reject additional connections
16018 without forking additional processes (otherwise a denial-of-service attack
16019 could cause a vast number or processes to be created). While the daemon is
16020 doing this processing, it cannot accept any other incoming connections.
16024 .option smtp_accept_queue main integer 0
16025 .cindex "SMTP" "incoming connection count"
16026 .cindex "queueing incoming messages"
16027 .cindex "message" "queueing by SMTP connection count"
16028 If the number of simultaneous incoming SMTP connections being handled via the
16029 listening daemon exceeds this value, messages received by SMTP are just placed
16030 on the queue; no delivery processes are started automatically. The count is
16031 fixed at the start of an SMTP connection. It cannot be updated in the
16032 subprocess that receives messages, and so the queueing or not queueing applies
16033 to all messages received in the same connection.
16035 A value of zero implies no limit, and clearly any non-zero value is useful only
16036 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
16037 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
16038 various &%-od%&&'x'& command line options.
16041 . See the comment on smtp_accept_max_per_connection
16043 .option "smtp_accept_queue_per_connection" main integer 10 &&&
16044 smtp_accept_queue_per_connection
16045 .cindex "queueing incoming messages"
16046 .cindex "message" "queueing by message count"
16047 This option limits the number of delivery processes that Exim starts
16048 automatically when receiving messages via SMTP, whether via the daemon or by
16049 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
16050 and the number of messages received in a single SMTP session exceeds this
16051 number, subsequent messages are placed on the queue, but no delivery processes
16052 are started. This helps to limit the number of Exim processes when a server
16053 restarts after downtime and there is a lot of mail waiting for it on other
16054 systems. On large systems, the default should probably be increased, and on
16055 dial-in client systems it should probably be set to zero (that is, disabled).
16058 .option smtp_accept_reserve main integer 0
16059 .cindex "SMTP" "incoming call count"
16060 .cindex "host" "reserved"
16061 When &%smtp_accept_max%& is set greater than zero, this option specifies a
16062 number of SMTP connections that are reserved for connections from the hosts
16063 that are specified in &%smtp_reserve_hosts%&. The value set in
16064 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
16065 restricted to this number of connections; the option specifies a minimum number
16066 of connection slots for them, not a maximum. It is a guarantee that this group
16067 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
16068 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
16071 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
16072 set to 5, once there are 45 active connections (from any hosts), new
16073 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
16074 provided the other criteria for acceptance are met.
16077 .option smtp_active_hostname main string&!! unset
16078 .cindex "host" "name in SMTP responses"
16079 .cindex "SMTP" "host name in responses"
16080 .vindex "&$primary_hostname$&"
16081 This option is provided for multi-homed servers that want to masquerade as
16082 several different hosts. At the start of an incoming SMTP connection, its value
16083 is expanded and used instead of the value of &$primary_hostname$& in SMTP
16084 responses. For example, it is used as domain name in the response to an
16085 incoming HELO or EHLO command.
16087 .vindex "&$smtp_active_hostname$&"
16088 The active hostname is placed in the &$smtp_active_hostname$& variable, which
16089 is saved with any messages that are received. It is therefore available for use
16090 in routers and transports when the message is later delivered.
16092 If this option is unset, or if its expansion is forced to fail, or if the
16093 expansion results in an empty string, the value of &$primary_hostname$& is
16094 used. Other expansion failures cause a message to be written to the main and
16095 panic logs, and the SMTP command receives a temporary error. Typically, the
16096 value of &%smtp_active_hostname%& depends on the incoming interface address.
16099 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
16100 {cox.mydomain}{box.mydomain}}
16103 Although &$smtp_active_hostname$& is primarily concerned with incoming
16104 messages, it is also used as the default for HELO commands in callout
16105 verification if there is no remote transport from which to obtain a
16106 &%helo_data%& value.
16108 .option smtp_banner main string&!! "see below"
16109 .cindex "SMTP" "welcome banner"
16110 .cindex "banner for SMTP"
16111 .cindex "welcome banner for SMTP"
16112 .cindex "customizing" "SMTP banner"
16113 This string, which is expanded every time it is used, is output as the initial
16114 positive response to an SMTP connection. The default setting is:
16116 smtp_banner = $smtp_active_hostname ESMTP Exim \
16117 $version_number $tod_full
16119 Failure to expand the string causes a panic error. If you want to create a
16120 multiline response to the initial SMTP connection, use &"\n"& in the string at
16121 appropriate points, but not at the end. Note that the 220 code is not included
16122 in this string. Exim adds it automatically (several times in the case of a
16123 multiline response).
16126 .option smtp_check_spool_space main boolean true
16127 .cindex "checking disk space"
16128 .cindex "disk space, checking"
16129 .cindex "spool directory" "checking space"
16130 When this option is set, if an incoming SMTP session encounters the SIZE
16131 option on a MAIL command, it checks that there is enough space in the
16132 spool directory's partition to accept a message of that size, while still
16133 leaving free the amount specified by &%check_spool_space%& (even if that value
16134 is zero). If there isn't enough space, a temporary error code is returned.
16137 .option smtp_connect_backlog main integer 20
16138 .cindex "connection backlog"
16139 .cindex "SMTP" "connection backlog"
16140 .cindex "backlog of connections"
16141 This option specifies a maximum number of waiting SMTP connections. Exim passes
16142 this value to the TCP/IP system when it sets up its listener. Once this number
16143 of connections are waiting for the daemon's attention, subsequent connection
16144 attempts are refused at the TCP/IP level. At least, that is what the manuals
16145 say; in some circumstances such connection attempts have been observed to time
16146 out instead. For large systems it is probably a good idea to increase the
16147 value (to 50, say). It also gives some protection against denial-of-service
16148 attacks by SYN flooding.
16151 .option smtp_enforce_sync main boolean true
16152 .cindex "SMTP" "synchronization checking"
16153 .cindex "synchronization checking in SMTP"
16154 The SMTP protocol specification requires the client to wait for a response from
16155 the server at certain points in the dialogue. Without PIPELINING these
16156 synchronization points are after every command; with PIPELINING they are
16157 fewer, but they still exist.
16159 Some spamming sites send out a complete set of SMTP commands without waiting
16160 for any response. Exim protects against this by rejecting a message if the
16161 client has sent further input when it should not have. The error response &"554
16162 SMTP synchronization error"& is sent, and the connection is dropped. Testing
16163 for this error cannot be perfect because of transmission delays (unexpected
16164 input may be on its way but not yet received when Exim checks). However, it
16165 does detect many instances.
16167 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
16168 If you want to disable the check selectively (for example, only for certain
16169 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
16170 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
16174 .option smtp_etrn_command main string&!! unset
16175 .cindex "ETRN" "command to be run"
16176 .vindex "&$domain$&"
16177 If this option is set, the given command is run whenever an SMTP ETRN
16178 command is received from a host that is permitted to issue such commands (see
16179 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
16180 are independently expanded. The expansion variable &$domain$& is set to the
16181 argument of the ETRN command, and no syntax checking is done on it. For
16184 smtp_etrn_command = /etc/etrn_command $domain \
16185 $sender_host_address
16187 A new process is created to run the command, but Exim does not wait for it to
16188 complete. Consequently, its status cannot be checked. If the command cannot be
16189 run, a line is written to the panic log, but the ETRN caller still receives
16190 a 250 success response. Exim is normally running under its own uid when
16191 receiving SMTP, so it is not possible for it to change the uid before running
16195 .option smtp_etrn_serialize main boolean true
16196 .cindex "ETRN" "serializing"
16197 When this option is set, it prevents the simultaneous execution of more than
16198 one identical command as a result of ETRN in an SMTP connection. See
16199 section &<<SECTETRN>>& for details.
16202 .option smtp_load_reserve main fixed-point unset
16203 .cindex "load average"
16204 If the system load average ever gets higher than this, incoming SMTP calls are
16205 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
16206 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
16207 the load is over the limit. The option has no effect on ancient operating
16208 systems on which Exim cannot determine the load average. See also
16209 &%deliver_queue_load_max%& and &%queue_only_load%&.
16213 .option smtp_max_synprot_errors main integer 3
16214 .cindex "SMTP" "limiting syntax and protocol errors"
16215 .cindex "limit" "SMTP syntax and protocol errors"
16216 Exim rejects SMTP commands that contain syntax or protocol errors. In
16217 particular, a syntactically invalid email address, as in this command:
16219 RCPT TO:<abc xyz@a.b.c>
16221 causes immediate rejection of the command, before any other tests are done.
16222 (The ACL cannot be run if there is no valid address to set up for it.) An
16223 example of a protocol error is receiving RCPT before MAIL. If there are
16224 too many syntax or protocol errors in one SMTP session, the connection is
16225 dropped. The limit is set by this option.
16227 .cindex "PIPELINING" "expected errors"
16228 When the PIPELINING extension to SMTP is in use, some protocol errors are
16229 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
16230 Exim assumes that PIPELINING will be used if it advertises it (see
16231 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
16232 not count towards the limit.
16236 .option smtp_max_unknown_commands main integer 3
16237 .cindex "SMTP" "limiting unknown commands"
16238 .cindex "limit" "unknown SMTP commands"
16239 If there are too many unrecognized commands in an incoming SMTP session, an
16240 Exim server drops the connection. This is a defence against some kinds of abuse
16243 into making connections to SMTP ports; in these circumstances, a number of
16244 non-SMTP command lines are sent first.
16248 .option smtp_ratelimit_hosts main "host list&!!" unset
16249 .cindex "SMTP" "rate limiting"
16250 .cindex "limit" "rate of message arrival"
16251 .cindex "RCPT" "rate limiting"
16252 Some sites find it helpful to be able to limit the rate at which certain hosts
16253 can send them messages, and the rate at which an individual message can specify
16256 Exim has two rate-limiting facilities. This section describes the older
16257 facility, which can limit rates within a single connection. The newer
16258 &%ratelimit%& ACL condition can limit rates across all connections. See section
16259 &<<SECTratelimiting>>& for details of the newer facility.
16261 When a host matches &%smtp_ratelimit_hosts%&, the values of
16262 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
16263 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
16264 respectively. Each option, if set, must contain a set of four comma-separated
16268 A threshold, before which there is no rate limiting.
16270 An initial time delay. Unlike other times in Exim, numbers with decimal
16271 fractional parts are allowed here.
16273 A factor by which to increase the delay each time.
16275 A maximum value for the delay. This should normally be less than 5 minutes,
16276 because after that time, the client is liable to timeout the SMTP command.
16279 For example, these settings have been used successfully at the site which
16280 first suggested this feature, for controlling mail from their customers:
16282 smtp_ratelimit_mail = 2,0.5s,1.05,4m
16283 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
16285 The first setting specifies delays that are applied to MAIL commands after
16286 two have been received over a single connection. The initial delay is 0.5
16287 seconds, increasing by a factor of 1.05 each time. The second setting applies
16288 delays to RCPT commands when more than four occur in a single message.
16291 .option smtp_ratelimit_mail main string unset
16292 See &%smtp_ratelimit_hosts%& above.
16295 .option smtp_ratelimit_rcpt main string unset
16296 See &%smtp_ratelimit_hosts%& above.
16299 .option smtp_receive_timeout main time&!! 5m
16300 .cindex "timeout" "for SMTP input"
16301 .cindex "SMTP" "input timeout"
16302 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
16303 input, including batch SMTP. If a line of input (either an SMTP command or a
16304 data line) is not received within this time, the SMTP connection is dropped and
16305 the message is abandoned.
16306 A line is written to the log containing one of the following messages:
16308 SMTP command timeout on connection from...
16309 SMTP data timeout on connection from...
16311 The former means that Exim was expecting to read an SMTP command; the latter
16312 means that it was in the DATA phase, reading the contents of a message.
16314 If the first character of the option is a &"$"& the option is
16315 expanded before use and may depend on
16316 &$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
16320 The value set by this option can be overridden by the
16321 &%-os%& command-line option. A setting of zero time disables the timeout, but
16322 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
16323 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
16324 timeout is controlled by &%receive_timeout%& and &%-or%&.
16327 .option smtp_reserve_hosts main "host list&!!" unset
16328 This option defines hosts for which SMTP connections are reserved; see
16329 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
16332 .option smtp_return_error_details main boolean false
16333 .cindex "SMTP" "details policy failures"
16334 .cindex "policy control" "rejection, returning details"
16335 In the default state, Exim uses bland messages such as
16336 &"Administrative prohibition"& when it rejects SMTP commands for policy
16337 reasons. Many sysadmins like this because it gives away little information
16338 to spammers. However, some other sysadmins who are applying strict checking
16339 policies want to give out much fuller information about failures. Setting
16340 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
16341 example, instead of &"Administrative prohibition"&, it might give:
16343 550-Rejected after DATA: '>' missing at end of address:
16344 550 failing address in "From" header is: <user@dom.ain
16347 .option spamd_address main string "see below"
16348 This option is available when Exim is compiled with the content-scanning
16349 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
16350 The default value is
16354 See section &<<SECTscanspamass>>& for more details.
16358 .option split_spool_directory main boolean false
16359 .cindex "multiple spool directories"
16360 .cindex "spool directory" "split"
16361 .cindex "directories, multiple"
16362 If this option is set, it causes Exim to split its input directory into 62
16363 subdirectories, each with a single alphanumeric character as its name. The
16364 sixth character of the message id is used to allocate messages to
16365 subdirectories; this is the least significant base-62 digit of the time of
16366 arrival of the message.
16368 Splitting up the spool in this way may provide better performance on systems
16369 where there are long mail queues, by reducing the number of files in any one
16370 directory. The msglog directory is also split up in a similar way to the input
16371 directory; however, if &%preserve_message_logs%& is set, all old msglog files
16372 are still placed in the single directory &_msglog.OLD_&.
16374 It is not necessary to take any special action for existing messages when
16375 changing &%split_spool_directory%&. Exim notices messages that are in the
16376 &"wrong"& place, and continues to process them. If the option is turned off
16377 after a period of being on, the subdirectories will eventually empty and be
16378 automatically deleted.
16380 When &%split_spool_directory%& is set, the behaviour of queue runner processes
16381 changes. Instead of creating a list of all messages in the queue, and then
16382 trying to deliver each one in turn, it constructs a list of those in one
16383 sub-directory and tries to deliver them, before moving on to the next
16384 sub-directory. The sub-directories are processed in a random order. This
16385 spreads out the scanning of the input directories, and uses less memory. It is
16386 particularly beneficial when there are lots of messages on the queue. However,
16387 if &%queue_run_in_order%& is set, none of this new processing happens. The
16388 entire queue has to be scanned and sorted before any deliveries can start.
16391 .option spool_directory main string&!! "set at compile time"
16392 .cindex "spool directory" "path to"
16393 This defines the directory in which Exim keeps its spool, that is, the messages
16394 it is waiting to deliver. The default value is taken from the compile-time
16395 configuration setting, if there is one. If not, this option must be set. The
16396 string is expanded, so it can contain, for example, a reference to
16397 &$primary_hostname$&.
16399 If the spool directory name is fixed on your installation, it is recommended
16400 that you set it at build time rather than from this option, particularly if the
16401 log files are being written to the spool directory (see &%log_file_path%&).
16402 Otherwise log files cannot be used for errors that are detected early on, such
16403 as failures in the configuration file.
16405 By using this option to override the compiled-in path, it is possible to run
16406 tests of Exim without using the standard spool.
16408 .option sqlite_lock_timeout main time 5s
16409 .cindex "sqlite lookup type" "lock timeout"
16410 This option controls the timeout that the &(sqlite)& lookup uses when trying to
16411 access an SQLite database. See section &<<SECTsqlite>>& for more details.
16413 .option strict_acl_vars main boolean false
16414 .cindex "&ACL;" "variables, handling unset"
16415 This option controls what happens if a syntactically valid but undefined ACL
16416 variable is referenced. If it is false (the default), an empty string
16417 is substituted; if it is true, an error is generated. See section
16418 &<<SECTaclvariables>>& for details of ACL variables.
16420 .option strip_excess_angle_brackets main boolean false
16421 .cindex "angle brackets, excess"
16422 If this option is set, redundant pairs of angle brackets round &"route-addr"&
16423 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
16424 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
16425 passed on to another MTA, the excess angle brackets are not passed on. If this
16426 option is not set, multiple pairs of angle brackets cause a syntax error.
16429 .option strip_trailing_dot main boolean false
16430 .cindex "trailing dot on domain"
16431 .cindex "dot" "trailing on domain"
16432 If this option is set, a trailing dot at the end of a domain in an address is
16433 ignored. If this is in the envelope and the message is passed on to another
16434 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
16435 domain causes a syntax error.
16436 However, addresses in header lines are checked only when an ACL requests header
16440 .option syslog_duplication main boolean true
16441 .cindex "syslog" "duplicate log lines; suppressing"
16442 When Exim is logging to syslog, it writes the log lines for its three
16443 separate logs at different syslog priorities so that they can in principle
16444 be separated on the logging hosts. Some installations do not require this
16445 separation, and in those cases, the duplication of certain log lines is a
16446 nuisance. If &%syslog_duplication%& is set false, only one copy of any
16447 particular log line is written to syslog. For lines that normally go to
16448 both the main log and the reject log, the reject log version (possibly
16449 containing message header lines) is written, at LOG_NOTICE priority.
16450 Lines that normally go to both the main and the panic log are written at
16451 the LOG_ALERT priority.
16454 .option syslog_facility main string unset
16455 .cindex "syslog" "facility; setting"
16456 This option sets the syslog &"facility"& name, used when Exim is logging to
16457 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
16458 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
16459 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
16460 details of Exim's logging.
16464 .option syslog_processname main string &`exim`&
16465 .cindex "syslog" "process name; setting"
16466 This option sets the syslog &"ident"& name, used when Exim is logging to
16467 syslog. The value must be no longer than 32 characters. See chapter
16468 &<<CHAPlog>>& for details of Exim's logging.
16472 .option syslog_timestamp main boolean true
16473 .cindex "syslog" "timestamps"
16474 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
16475 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
16476 details of Exim's logging.
16479 .option system_filter main string&!! unset
16480 .cindex "filter" "system filter"
16481 .cindex "system filter" "specifying"
16482 .cindex "Sieve filter" "not available for system filter"
16483 This option specifies an Exim filter file that is applied to all messages at
16484 the start of each delivery attempt, before any routing is done. System filters
16485 must be Exim filters; they cannot be Sieve filters. If the system filter
16486 generates any deliveries to files or pipes, or any new mail messages, the
16487 appropriate &%system_filter_..._transport%& option(s) must be set, to define
16488 which transports are to be used. Details of this facility are given in chapter
16489 &<<CHAPsystemfilter>>&.
16492 .option system_filter_directory_transport main string&!! unset
16493 .vindex "&$address_file$&"
16494 This sets the name of the transport driver that is to be used when the
16495 &%save%& command in a system message filter specifies a path ending in &"/"&,
16496 implying delivery of each message into a separate file in some directory.
16497 During the delivery, the variable &$address_file$& contains the path name.
16500 .option system_filter_file_transport main string&!! unset
16501 .cindex "file" "transport for system filter"
16502 This sets the name of the transport driver that is to be used when the &%save%&
16503 command in a system message filter specifies a path not ending in &"/"&. During
16504 the delivery, the variable &$address_file$& contains the path name.
16506 .option system_filter_group main string unset
16507 .cindex "gid (group id)" "system filter"
16508 This option is used only when &%system_filter_user%& is also set. It sets the
16509 gid under which the system filter is run, overriding any gid that is associated
16510 with the user. The value may be numerical or symbolic.
16512 .option system_filter_pipe_transport main string&!! unset
16513 .cindex "&(pipe)& transport" "for system filter"
16514 .vindex "&$address_pipe$&"
16515 This specifies the transport driver that is to be used when a &%pipe%& command
16516 is used in a system filter. During the delivery, the variable &$address_pipe$&
16517 contains the pipe command.
16520 .option system_filter_reply_transport main string&!! unset
16521 .cindex "&(autoreply)& transport" "for system filter"
16522 This specifies the transport driver that is to be used when a &%mail%& command
16523 is used in a system filter.
16526 .option system_filter_user main string unset
16527 .cindex "uid (user id)" "system filter"
16528 If this option is set to root, the system filter is run in the main Exim
16529 delivery process, as root. Otherwise, the system filter runs in a separate
16530 process, as the given user, defaulting to the Exim run-time user.
16531 Unless the string consists entirely of digits, it
16532 is looked up in the password data. Failure to find the named user causes a
16533 configuration error. The gid is either taken from the password data, or
16534 specified by &%system_filter_group%&. When the uid is specified numerically,
16535 &%system_filter_group%& is required to be set.
16537 If the system filter generates any pipe, file, or reply deliveries, the uid
16538 under which the filter is run is used when transporting them, unless a
16539 transport option overrides.
16542 .option tcp_nodelay main boolean true
16543 .cindex "daemon" "TCP_NODELAY on sockets"
16544 .cindex "Nagle algorithm"
16545 .cindex "TCP_NODELAY on listening sockets"
16546 If this option is set false, it stops the Exim daemon setting the
16547 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
16548 turns off the &"Nagle algorithm"&, which is a way of improving network
16549 performance in interactive (character-by-character) situations. Turning it off
16550 should improve Exim's performance a bit, so that is what happens by default.
16551 However, it appears that some broken clients cannot cope, and time out. Hence
16552 this option. It affects only those sockets that are set up for listening by the
16553 daemon. Sockets created by the smtp transport for delivering mail always set
16557 .option timeout_frozen_after main time 0s
16558 .cindex "frozen messages" "timing out"
16559 .cindex "timeout" "frozen messages"
16560 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
16561 message of any kind that has been on the queue for longer than the given time
16562 is automatically cancelled at the next queue run. If the frozen message is a
16563 bounce message, it is just discarded; otherwise, a bounce is sent to the
16564 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
16565 If you want to timeout frozen bounce messages earlier than other kinds of
16566 frozen message, see &%ignore_bounce_errors_after%&.
16568 &*Note:*& the default value of zero means no timeouts; with this setting,
16569 frozen messages remain on the queue forever (except for any frozen bounce
16570 messages that are released by &%ignore_bounce_errors_after%&).
16573 .option timezone main string unset
16574 .cindex "timezone, setting"
16575 The value of &%timezone%& is used to set the environment variable TZ while
16576 running Exim (if it is different on entry). This ensures that all timestamps
16577 created by Exim are in the required timezone. If you want all your timestamps
16578 to be in UTC (aka GMT) you should set
16582 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
16583 or, if that is not set, from the value of the TZ environment variable when Exim
16584 is built. If &%timezone%& is set to the empty string, either at build or run
16585 time, any existing TZ variable is removed from the environment when Exim
16586 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
16587 unfortunately not all, operating systems.
16591 .option tls_advertise_hosts main "host list&!!" *
16593 .cindex "TLS" "advertising"
16594 .cindex "encryption" "on SMTP connection"
16595 .cindex "SMTP" "encrypted connection"
16596 When Exim is built with support for TLS encrypted connections, the availability
16597 of the STARTTLS command to set up an encrypted session is advertised in
16598 response to EHLO only to those client hosts that match this option. See
16599 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
16601 Note that the default value requires that a certificate be supplied
16602 using the &%tls_certificate%& option. If no certificate is available then
16603 the &%tls_advertise_hosts%& option should be set empty.
16607 .option tls_certificate main string&!! unset
16608 .cindex "TLS" "server certificate; location of"
16609 .cindex "certificate" "server, location of"
16610 The value of this option is expanded, and must then be the absolute path to a
16611 file which contains the server's certificates. The server's private key is also
16612 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
16613 &<<CHAPTLS>>& for further details.
16615 &*Note*&: The certificates defined by this option are used only when Exim is
16616 receiving incoming messages as a server. If you want to supply certificates for
16617 use when sending messages as a client, you must set the &%tls_certificate%&
16618 option in the relevant &(smtp)& transport.
16620 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
16621 if the OpenSSL build supports TLS extensions and the TLS client sends the
16622 Server Name Indication extension, then this option and others documented in
16623 &<<SECTtlssni>>& will be re-expanded.
16625 .option tls_crl main string&!! unset
16626 .cindex "TLS" "server certificate revocation list"
16627 .cindex "certificate" "revocation list for server"
16628 This option specifies a certificate revocation list. The expanded value must
16629 be the name of a file that contains a CRL in PEM format.
16631 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
16634 .option tls_dh_max_bits main integer 2236
16635 .cindex "TLS" "D-H bit count"
16636 The number of bits used for Diffie-Hellman key-exchange may be suggested by
16637 the chosen TLS library. That value might prove to be too high for
16638 interoperability. This option provides a maximum clamp on the value
16639 suggested, trading off security for interoperability.
16641 The value must be at least 1024.
16643 The value 2236 was chosen because, at time of adding the option, it was the
16644 hard-coded maximum value supported by the NSS cryptographic library, as used
16645 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
16647 If you prefer more security and are willing to break some clients, raise this
16650 Note that the value passed to GnuTLS for *generating* a new prime may be a
16651 little less than this figure, because GnuTLS is inexact and may produce a
16652 larger prime than requested.
16655 .option tls_dhparam main string&!! unset
16656 .cindex "TLS" "D-H parameters for server"
16657 The value of this option is expanded and indicates the source of DH parameters
16658 to be used by Exim.
16660 If it is a filename starting with a &`/`&, then it names a file from which DH
16661 parameters should be loaded. If the file exists, it should hold a PEM-encoded
16662 PKCS#3 representation of the DH prime. If the file does not exist, for
16663 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
16664 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
16665 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
16666 and treated as though the &%tls_dhparam%& were set to "none".
16668 If this option expands to the string "none", then no DH parameters will be
16671 If this option expands to the string "historic" and Exim is using GnuTLS, then
16672 Exim will attempt to load a file from inside the spool directory. If the file
16673 does not exist, Exim will attempt to create it.
16674 See section &<<SECTgnutlsparam>>& for further details.
16676 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
16677 a default DH prime; the default is the 2048 bit prime described in section
16678 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
16679 in IKE is assigned number 23.
16681 Otherwise, the option must expand to the name used by Exim for any of a number
16682 of DH primes specified in RFC 2409, RFC 3526 and RFC 5114. As names, Exim uses
16683 "ike" followed by the number used by IKE, of "default" which corresponds to
16686 The available primes are:
16687 &`ike1`&, &`ike2`&, &`ike5`&,
16688 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
16689 &`ike22`&, &`ike23`& (aka &`default`&) and &`ike24`&.
16691 Some of these will be too small to be accepted by clients.
16692 Some may be too large to be accepted by clients.
16694 The TLS protocol does not negotiate an acceptable size for this; clients tend
16695 to hard-drop connections if what is offered by the server is unacceptable,
16696 whether too large or too small, and there's no provision for the client to
16697 tell the server what these constraints are. Thus, as a server operator, you
16698 need to make an educated guess as to what is most likely to work for your
16701 Some known size constraints suggest that a bit-size in the range 2048 to 2236
16702 is most likely to maximise interoperability. The upper bound comes from
16703 applications using the Mozilla Network Security Services (NSS) library, which
16704 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
16705 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
16706 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
16707 acceptable bound from 1024 to 2048.
16710 .option tls_eccurve main string&!! prime256v1
16711 .cindex TLS "EC cryptography"
16712 If built with a recent-enough version of OpenSSL,
16713 this option selects a EC curve for use by Exim.
16715 Curve names of the form &'prime256v1'& are accepted.
16716 For even more-recent library versions, names of the form &'P-512'&
16717 are also accepted, plus the special value &'auto'&
16718 which tell the library to choose.
16720 If the option is set to an empty string, no EC curves will be enabled.
16723 .option tls_ocsp_file main string&!! unset
16724 .cindex TLS "certificate status"
16725 .cindex TLS "OCSP proof file"
16727 must if set expand to the absolute path to a file which contains a current
16728 status proof for the server's certificate, as obtained from the
16729 Certificate Authority.
16732 Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
16736 .option tls_on_connect_ports main "string list" unset
16739 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
16740 operate the obsolete SSMTP (SMTPS) protocol, where a TLS session is immediately
16741 set up without waiting for the client to issue a STARTTLS command. For
16742 further details, see section &<<SECTsupobssmt>>&.
16746 .option tls_privatekey main string&!! unset
16747 .cindex "TLS" "server private key; location of"
16748 The value of this option is expanded, and must then be the absolute path to a
16749 file which contains the server's private key. If this option is unset, or if
16750 the expansion is forced to fail, or the result is an empty string, the private
16751 key is assumed to be in the same file as the server's certificates. See chapter
16752 &<<CHAPTLS>>& for further details.
16754 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
16757 .option tls_remember_esmtp main boolean false
16758 .cindex "TLS" "esmtp state; remembering"
16759 .cindex "TLS" "broken clients"
16760 If this option is set true, Exim violates the RFCs by remembering that it is in
16761 &"esmtp"& state after successfully negotiating a TLS session. This provides
16762 support for broken clients that fail to send a new EHLO after starting a
16766 .option tls_require_ciphers main string&!! unset
16767 .cindex "TLS" "requiring specific ciphers"
16768 .cindex "cipher" "requiring specific"
16769 This option controls which ciphers can be used for incoming TLS connections.
16770 The &(smtp)& transport has an option of the same name for controlling outgoing
16771 connections. This option is expanded for each connection, so can be varied for
16772 different clients if required. The value of this option must be a list of
16773 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
16774 in somewhat different ways. If GnuTLS is being used, the client controls the
16775 preference order of the available ciphers. Details are given in sections
16776 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
16779 .option tls_try_verify_hosts main "host list&!!" unset
16780 .cindex "TLS" "client certificate verification"
16781 .cindex "certificate" "verification of client"
16782 See &%tls_verify_hosts%& below.
16785 .option tls_verify_certificates main string&!! system
16786 .cindex "TLS" "client certificate verification"
16787 .cindex "certificate" "verification of client"
16788 The value of this option is expanded, and must then be either the
16790 or the absolute path to
16791 a file or directory containing permitted certificates for clients that
16792 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
16794 The "system" value for the option will use a
16795 system default location compiled into the SSL library.
16796 This is not available for GnuTLS versions preceding 3.0.20,
16797 and will be taken as empty; an explicit location
16800 The use of a directory for the option value is not available for GnuTLS versions
16801 preceding 3.3.6 and a single file must be used.
16803 With OpenSSL the certificates specified
16805 either by file or directory
16806 are added to those given by the system default location.
16808 These certificates should be for the certificate authorities trusted, rather
16809 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
16810 the value is a file then the certificates are sent by Exim as a server to
16811 connecting clients, defining the list of accepted certificate authorities.
16812 Thus the values defined should be considered public data. To avoid this,
16813 use the explicit directory version.
16815 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
16817 A forced expansion failure or setting to an empty string is equivalent to
16821 .option tls_verify_hosts main "host list&!!" unset
16822 .cindex "TLS" "client certificate verification"
16823 .cindex "certificate" "verification of client"
16824 This option, along with &%tls_try_verify_hosts%&, controls the checking of
16825 certificates from clients. The expected certificates are defined by
16826 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
16827 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
16828 &%tls_verify_certificates%& is not set.
16830 Any client that matches &%tls_verify_hosts%& is constrained by
16831 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
16832 present one of the listed certificates. If it does not, the connection is
16833 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
16834 the host to use TLS. It can still send SMTP commands through unencrypted
16835 connections. Forcing a client to use TLS has to be done separately using an
16836 ACL to reject inappropriate commands when the connection is not encrypted.
16838 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
16839 matches this option (but not &%tls_verify_hosts%&), Exim requests a
16840 certificate and checks it against &%tls_verify_certificates%&, but does not
16841 abort the connection if there is no certificate or if it does not match. This
16842 state can be detected in an ACL, which makes it possible to implement policies
16843 such as &"accept for relay only if a verified certificate has been received,
16844 but accept for local delivery if encrypted, even without a verified
16847 Client hosts that match neither of these lists are not asked to present
16851 .option trusted_groups main "string list&!!" unset
16852 .cindex "trusted groups"
16853 .cindex "groups" "trusted"
16854 This option is expanded just once, at the start of Exim's processing. If this
16855 option is set, any process that is running in one of the listed groups, or
16856 which has one of them as a supplementary group, is trusted. The groups can be
16857 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
16858 details of what trusted callers are permitted to do. If neither
16859 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
16862 .option trusted_users main "string list&!!" unset
16863 .cindex "trusted users"
16864 .cindex "user" "trusted"
16865 This option is expanded just once, at the start of Exim's processing. If this
16866 option is set, any process that is running as one of the listed users is
16867 trusted. The users can be specified numerically or by name. See section
16868 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
16869 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
16870 Exim user are trusted.
16872 .option unknown_login main string&!! unset
16873 .cindex "uid (user id)" "unknown caller"
16874 .vindex "&$caller_uid$&"
16875 This is a specialized feature for use in unusual configurations. By default, if
16876 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
16877 gives up. The &%unknown_login%& option can be used to set a login name to be
16878 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
16879 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
16880 is used for the user's real name (gecos field), unless this has been set by the
16883 .option unknown_username main string unset
16884 See &%unknown_login%&.
16886 .option untrusted_set_sender main "address list&!!" unset
16887 .cindex "trusted users"
16888 .cindex "sender" "setting by untrusted user"
16889 .cindex "untrusted user setting sender"
16890 .cindex "user" "untrusted setting sender"
16891 .cindex "envelope sender"
16892 When an untrusted user submits a message to Exim using the standard input, Exim
16893 normally creates an envelope sender address from the user's login and the
16894 default qualification domain. Data from the &%-f%& option (for setting envelope
16895 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
16896 is used) is ignored.
16898 However, untrusted users are permitted to set an empty envelope sender address,
16899 to declare that a message should never generate any bounces. For example:
16901 exim -f '<>' user@domain.example
16903 .vindex "&$sender_ident$&"
16904 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
16905 other envelope sender addresses in a controlled way. When it is set, untrusted
16906 users are allowed to set envelope sender addresses that match any of the
16907 patterns in the list. Like all address lists, the string is expanded. The
16908 identity of the user is in &$sender_ident$&, so you can, for example, restrict
16909 users to setting senders that start with their login ids
16910 followed by a hyphen
16911 by a setting like this:
16913 untrusted_set_sender = ^$sender_ident-
16915 If you want to allow untrusted users to set envelope sender addresses without
16916 restriction, you can use
16918 untrusted_set_sender = *
16920 The &%untrusted_set_sender%& option applies to all forms of local input, but
16921 only to the setting of the envelope sender. It does not permit untrusted users
16922 to use the other options which trusted user can use to override message
16923 parameters. Furthermore, it does not stop Exim from removing an existing
16924 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
16925 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
16926 overriding these actions. The handling of the &'Sender:'& header is also
16927 described in section &<<SECTthesenhea>>&.
16929 The log line for a message's arrival shows the envelope sender following
16930 &"<="&. For local messages, the user's login always follows, after &"U="&. In
16931 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
16932 envelope sender address, the user's login is shown in parentheses after the
16936 .option uucp_from_pattern main string "see below"
16937 .cindex "&""From""& line"
16938 .cindex "UUCP" "&""From""& line"
16939 Some applications that pass messages to an MTA via a command line interface use
16940 an initial line starting with &"From&~"& to pass the envelope sender. In
16941 particular, this is used by UUCP software. Exim recognizes such a line by means
16942 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
16943 matches, the sender address is constructed by expanding the contents of
16944 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
16945 default pattern recognizes lines in the following two forms:
16947 From ph10 Fri Jan 5 12:35 GMT 1996
16948 From ph10 Fri, 7 Jan 97 14:00:00 GMT
16950 The pattern can be seen by running
16952 exim -bP uucp_from_pattern
16954 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
16955 year in the second case. The first word after &"From&~"& is matched in the
16956 regular expression by a parenthesized subpattern. The default value for
16957 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
16958 (&"ph10"& in the example above) as the message's sender. See also
16959 &%ignore_fromline_hosts%&.
16962 .option uucp_from_sender main string&!! &`$1`&
16963 See &%uucp_from_pattern%& above.
16966 .option warn_message_file main string unset
16967 .cindex "warning of delay" "customizing the message"
16968 .cindex "customizing" "warning message"
16969 This option defines a template file containing paragraphs of text to be used
16970 for constructing the warning message which is sent by Exim when a message has
16971 been on the queue for a specified amount of time, as specified by
16972 &%delay_warning%&. Details of the file's contents are given in chapter
16973 &<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
16976 .option write_rejectlog main boolean true
16977 .cindex "reject log" "disabling"
16978 If this option is set false, Exim no longer writes anything to the reject log.
16979 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
16980 .ecindex IIDconfima
16981 .ecindex IIDmaiconf
16986 . ////////////////////////////////////////////////////////////////////////////
16987 . ////////////////////////////////////////////////////////////////////////////
16989 .chapter "Generic options for routers" "CHAProutergeneric"
16990 .scindex IIDgenoprou1 "options" "generic; for routers"
16991 .scindex IIDgenoprou2 "generic options" "router"
16992 This chapter describes the generic options that apply to all routers.
16993 Those that are preconditions are marked with ‡ in the &"use"& field.
16995 For a general description of how a router operates, see sections
16996 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
16997 which the preconditions are tested. The order of expansion of the options that
16998 provide data for a transport is: &%errors_to%&, &%headers_add%&,
16999 &%headers_remove%&, &%transport%&.
17003 .option address_data routers string&!! unset
17004 .cindex "router" "data attached to address"
17005 The string is expanded just before the router is run, that is, after all the
17006 precondition tests have succeeded. If the expansion is forced to fail, the
17007 router declines, the value of &%address_data%& remains unchanged, and the
17008 &%more%& option controls what happens next. Other expansion failures cause
17009 delivery of the address to be deferred.
17011 .vindex "&$address_data$&"
17012 When the expansion succeeds, the value is retained with the address, and can be
17013 accessed using the variable &$address_data$& in the current router, subsequent
17014 routers, and the eventual transport.
17016 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
17017 that runs a user's filter file, the contents of &$address_data$& are accessible
17018 in the filter. This is not normally a problem, because such data is usually
17019 either not confidential or it &"belongs"& to the current user, but if you do
17020 put confidential data into &$address_data$& you need to remember this point.
17022 Even if the router declines or passes, the value of &$address_data$& remains
17023 with the address, though it can be changed by another &%address_data%& setting
17024 on a subsequent router. If a router generates child addresses, the value of
17025 &$address_data$& propagates to them. This also applies to the special kind of
17026 &"child"& that is generated by a router with the &%unseen%& option.
17028 The idea of &%address_data%& is that you can use it to look up a lot of data
17029 for the address once, and then pick out parts of the data later. For example,
17030 you could use a single LDAP lookup to return a string of the form
17032 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
17034 In the transport you could pick out the mailbox by a setting such as
17036 file = ${extract{mailbox}{$address_data}}
17038 This makes the configuration file less messy, and also reduces the number of
17039 lookups (though Exim does cache lookups).
17041 .vindex "&$sender_address_data$&"
17042 .vindex "&$address_data$&"
17043 The &%address_data%& facility is also useful as a means of passing information
17044 from one router to another, and from a router to a transport. In addition, if
17045 &$address_data$& is set by a router when verifying a recipient address from an
17046 ACL, it remains available for use in the rest of the ACL statement. After
17047 verifying a sender, the value is transferred to &$sender_address_data$&.
17051 .option address_test routers&!? boolean true
17053 .cindex "router" "skipping when address testing"
17054 If this option is set false, the router is skipped when routing is being tested
17055 by means of the &%-bt%& command line option. This can be a convenience when
17056 your first router sends messages to an external scanner, because it saves you
17057 having to set the &"already scanned"& indicator when testing real address
17062 .option cannot_route_message routers string&!! unset
17063 .cindex "router" "customizing &""cannot route""& message"
17064 .cindex "customizing" "&""cannot route""& message"
17065 This option specifies a text message that is used when an address cannot be
17066 routed because Exim has run out of routers. The default message is
17067 &"Unrouteable address"&. This option is useful only on routers that have
17068 &%more%& set false, or on the very last router in a configuration, because the
17069 value that is used is taken from the last router that is considered. This
17070 includes a router that is skipped because its preconditions are not met, as
17071 well as a router that declines. For example, using the default configuration,
17074 cannot_route_message = Remote domain not found in DNS
17076 on the first router, which is a &(dnslookup)& router with &%more%& set false,
17079 cannot_route_message = Unknown local user
17081 on the final router that checks for local users. If string expansion fails for
17082 this option, the default message is used. Unless the expansion failure was
17083 explicitly forced, a message about the failure is written to the main and panic
17084 logs, in addition to the normal message about the routing failure.
17087 .option caseful_local_part routers boolean false
17088 .cindex "case of local parts"
17089 .cindex "router" "case of local parts"
17090 By default, routers handle the local parts of addresses in a case-insensitive
17091 manner, though the actual case is preserved for transmission with the message.
17092 If you want the case of letters to be significant in a router, you must set
17093 this option true. For individual router options that contain address or local
17094 part lists (for example, &%local_parts%&), case-sensitive matching can be
17095 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
17098 .vindex "&$local_part$&"
17099 .vindex "&$original_local_part$&"
17100 .vindex "&$parent_local_part$&"
17101 The value of the &$local_part$& variable is forced to lower case while a
17102 router is running unless &%caseful_local_part%& is set. When a router assigns
17103 an address to a transport, the value of &$local_part$& when the transport runs
17104 is the same as it was in the router. Similarly, when a router generates child
17105 addresses by aliasing or forwarding, the values of &$original_local_part$&
17106 and &$parent_local_part$& are those that were used by the redirecting router.
17108 This option applies to the processing of an address by a router. When a
17109 recipient address is being processed in an ACL, there is a separate &%control%&
17110 modifier that can be used to specify case-sensitive processing within the ACL
17111 (see section &<<SECTcontrols>>&).
17115 .option check_local_user routers&!? boolean false
17116 .cindex "local user, checking in router"
17117 .cindex "router" "checking for local user"
17118 .cindex "&_/etc/passwd_&"
17120 When this option is true, Exim checks that the local part of the recipient
17121 address (with affixes removed if relevant) is the name of an account on the
17122 local system. The check is done by calling the &[getpwnam()]& function rather
17123 than trying to read &_/etc/passwd_& directly. This means that other methods of
17124 holding password data (such as NIS) are supported. If the local part is a local
17125 user, &$home$& is set from the password data, and can be tested in other
17126 preconditions that are evaluated after this one (the order of evaluation is
17127 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
17128 overridden by &%router_home_directory%&. If the local part is not a local user,
17129 the router is skipped.
17131 If you want to check that the local part is either the name of a local user
17132 or matches something else, you cannot combine &%check_local_user%& with a
17133 setting of &%local_parts%&, because that specifies the logical &'and'& of the
17134 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
17135 setting to achieve this. For example:
17137 local_parts = passwd;$local_part : lsearch;/etc/other/users
17139 Note, however, that the side effects of &%check_local_user%& (such as setting
17140 up a home directory) do not occur when a &(passwd)& lookup is used in a
17141 &%local_parts%& (or any other) precondition.
17145 .option condition routers&!? string&!! unset
17146 .cindex "router" "customized precondition"
17147 This option specifies a general precondition test that has to succeed for the
17148 router to be called. The &%condition%& option is the last precondition to be
17149 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
17150 result is a forced failure, or an empty string, or one of the strings &"0"& or
17151 &"no"& or &"false"& (checked without regard to the case of the letters), the
17152 router is skipped, and the address is offered to the next one.
17154 If the result is any other value, the router is run (as this is the last
17155 precondition to be evaluated, all the other preconditions must be true).
17157 This option is unusual in that multiple &%condition%& options may be present.
17158 All &%condition%& options must succeed.
17160 The &%condition%& option provides a means of applying custom conditions to the
17161 running of routers. Note that in the case of a simple conditional expansion,
17162 the default expansion values are exactly what is wanted. For example:
17164 condition = ${if >{$message_age}{600}}
17166 Because of the default behaviour of the string expansion, this is equivalent to
17168 condition = ${if >{$message_age}{600}{true}{}}
17171 A multiple condition example, which succeeds:
17173 condition = ${if >{$message_age}{600}}
17174 condition = ${if !eq{${lc:$local_part}}{postmaster}}
17178 If the expansion fails (other than forced failure) delivery is deferred. Some
17179 of the other precondition options are common special cases that could in fact
17180 be specified using &%condition%&.
17182 Historical note: We have &%condition%& on ACLs and on Routers. Routers
17183 are far older, and use one set of semantics. ACLs are newer and when
17184 they were created, the ACL &%condition%& process was given far stricter
17185 parse semantics. The &%bool{}%& expansion condition uses the same rules as
17186 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
17187 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
17188 Router rules processing behavior.
17190 This is best illustrated in an example:
17192 # If used in an ACL condition will fail with a syntax error, but
17193 # in a router condition any extra characters are treated as a string
17195 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
17198 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
17201 In each example above, the &%if%& statement actually ends after
17202 &"{google.com}}"&. Since no true or false braces were defined, the
17203 default &%if%& behavior is to return a boolean true or a null answer
17204 (which evaluates to false). The rest of the line is then treated as a
17205 string. So the first example resulted in the boolean answer &"true"&
17206 with the string &" {yes} {no}}"& appended to it. The second example
17207 resulted in the null output (indicating false) with the string
17208 &" {yes} {no}}"& appended to it.
17210 In fact you can put excess forward braces in too. In the router
17211 &%condition%&, Exim's parser only looks for &"{"& symbols when they
17212 mean something, like after a &"$"& or when required as part of a
17213 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
17216 Thus, in a Router, the above expansion strings will both always evaluate
17217 true, as the result of expansion is a non-empty string which doesn't
17218 match an explicit false value. This can be tricky to debug. By
17219 contrast, in an ACL either of those strings will always result in an
17220 expansion error because the result doesn't look sufficiently boolean.
17223 .option debug_print routers string&!! unset
17224 .cindex "testing" "variables in drivers"
17225 If this option is set and debugging is enabled (see the &%-d%& command line
17226 option) or in address-testing mode (see the &%-bt%& command line option),
17227 the string is expanded and included in the debugging output.
17228 If expansion of the string fails, the error message is written to the debugging
17229 output, and Exim carries on processing.
17230 This option is provided to help with checking out the values of variables and
17231 so on when debugging router configurations. For example, if a &%condition%&
17232 option appears not to be working, &%debug_print%& can be used to output the
17233 variables it references. The output happens after checks for &%domains%&,
17234 &%local_parts%&, and &%check_local_user%& but before any other preconditions
17235 are tested. A newline is added to the text if it does not end with one.
17236 The variable &$router_name$& contains the name of the router.
17240 .option disable_logging routers boolean false
17241 If this option is set true, nothing is logged for any routing errors
17242 or for any deliveries caused by this router. You should not set this option
17243 unless you really, really know what you are doing. See also the generic
17244 transport option of the same name.
17246 .option dnssec_request_domains routers "domain list&!!" unset
17247 .cindex "MX record" "security"
17248 .cindex "DNSSEC" "MX lookup"
17249 .cindex "security" "MX lookup"
17250 .cindex "DNS" "DNSSEC"
17251 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
17252 the dnssec request bit set.
17253 This applies to all of the SRV, MX, AAAA, A lookup sequence.
17255 .option dnssec_require_domains routers "domain list&!!" unset
17256 .cindex "MX record" "security"
17257 .cindex "DNSSEC" "MX lookup"
17258 .cindex "security" "MX lookup"
17259 .cindex "DNS" "DNSSEC"
17260 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
17261 the dnssec request bit set. Any returns not having the Authenticated Data bit
17262 (AD bit) set will be ignored and logged as a host-lookup failure.
17263 This applies to all of the SRV, MX, AAAA, A lookup sequence.
17266 .option domains routers&!? "domain list&!!" unset
17267 .cindex "router" "restricting to specific domains"
17268 .vindex "&$domain_data$&"
17269 If this option is set, the router is skipped unless the current domain matches
17270 the list. If the match is achieved by means of a file lookup, the data that the
17271 lookup returned for the domain is placed in &$domain_data$& for use in string
17272 expansions of the driver's private options. See section &<<SECTrouprecon>>& for
17273 a list of the order in which preconditions are evaluated.
17277 .option driver routers string unset
17278 This option must always be set. It specifies which of the available routers is
17282 .option dsn_lasthop routers boolean false
17283 .cindex "DSN" "success"
17284 .cindex "Delivery Status Notification" "success"
17285 If this option is set true, and extended DSN (RFC3461) processing is in effect,
17286 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
17287 instead send a success DSN as if the next hop does not support DSN.
17288 Not effective on redirect routers.
17292 .option errors_to routers string&!! unset
17293 .cindex "envelope sender"
17294 .cindex "router" "changing address for errors"
17295 If a router successfully handles an address, it may assign the address to a
17296 transport for delivery or it may generate child addresses. In both cases, if
17297 there is a delivery problem during later processing, the resulting bounce
17298 message is sent to the address that results from expanding this string,
17299 provided that the address verifies successfully. The &%errors_to%& option is
17300 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
17302 The &%errors_to%& setting associated with an address can be overridden if it
17303 subsequently passes through other routers that have their own &%errors_to%&
17304 settings, or if the message is delivered by a transport with a &%return_path%&
17307 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
17308 the expansion fails to verify, the errors address associated with the incoming
17309 address is used. At top level, this is the envelope sender. A non-forced
17310 expansion failure causes delivery to be deferred.
17312 If an address for which &%errors_to%& has been set ends up being delivered over
17313 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
17314 any bounces that are generated by other MTAs on the delivery route are also
17315 sent there. You can set &%errors_to%& to the empty string by either of these
17321 An expansion item that yields an empty string has the same effect. If you do
17322 this, a locally detected delivery error for addresses processed by this router
17323 no longer gives rise to a bounce message; the error is discarded. If the
17324 address is delivered to a remote host, the return path is set to &`<>`&, unless
17325 overridden by the &%return_path%& option on the transport.
17327 .vindex "&$address_data$&"
17328 If for some reason you want to discard local errors, but use a non-empty
17329 MAIL command for remote delivery, you can preserve the original return
17330 path in &$address_data$& in the router, and reinstate it in the transport by
17331 setting &%return_path%&.
17333 The most common use of &%errors_to%& is to direct mailing list bounces to the
17334 manager of the list, as described in section &<<SECTmailinglists>>&, or to
17335 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
17339 .option expn routers&!? boolean true
17340 .cindex "address" "testing"
17341 .cindex "testing" "addresses"
17342 .cindex "EXPN" "router skipping"
17343 .cindex "router" "skipping for EXPN"
17344 If this option is turned off, the router is skipped when testing an address
17345 as a result of processing an SMTP EXPN command. You might, for example,
17346 want to turn it off on a router for users' &_.forward_& files, while leaving it
17347 on for the system alias file.
17348 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17351 The use of the SMTP EXPN command is controlled by an ACL (see chapter
17352 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
17353 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
17357 .option fail_verify routers boolean false
17358 .cindex "router" "forcing verification failure"
17359 Setting this option has the effect of setting both &%fail_verify_sender%& and
17360 &%fail_verify_recipient%& to the same value.
17364 .option fail_verify_recipient routers boolean false
17365 If this option is true and an address is accepted by this router when
17366 verifying a recipient, verification fails.
17370 .option fail_verify_sender routers boolean false
17371 If this option is true and an address is accepted by this router when
17372 verifying a sender, verification fails.
17376 .option fallback_hosts routers "string list" unset
17377 .cindex "router" "fallback hosts"
17378 .cindex "fallback" "hosts specified on router"
17379 String expansion is not applied to this option. The argument must be a
17380 colon-separated list of host names or IP addresses. The list separator can be
17381 changed (see section &<<SECTlistconstruct>>&), and a port can be specified with
17382 each name or address. In fact, the format of each item is exactly the same as
17383 defined for the list of hosts in a &(manualroute)& router (see section
17384 &<<SECTformatonehostitem>>&).
17386 If a router queues an address for a remote transport, this host list is
17387 associated with the address, and used instead of the transport's fallback host
17388 list. If &%hosts_randomize%& is set on the transport, the order of the list is
17389 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
17390 transport for further details.
17393 .option group routers string&!! "see below"
17394 .cindex "gid (group id)" "local delivery"
17395 .cindex "local transports" "uid and gid"
17396 .cindex "transport" "local"
17397 .cindex "router" "setting group"
17398 When a router queues an address for a transport, and the transport does not
17399 specify a group, the group given here is used when running the delivery
17401 The group may be specified numerically or by name. If expansion fails, the
17402 error is logged and delivery is deferred.
17403 The default is unset, unless &%check_local_user%& is set, when the default
17404 is taken from the password information. See also &%initgroups%& and &%user%&
17405 and the discussion in chapter &<<CHAPenvironment>>&.
17409 .option headers_add routers list&!! unset
17410 .cindex "header lines" "adding"
17411 .cindex "router" "adding header lines"
17412 This option specifies a list of text headers,
17413 newline-separated (by default, changeable in the usual way),
17414 that is associated with any addresses that are accepted by the router.
17415 Each item is separately expanded, at routing time. However, this
17416 option has no effect when an address is just being verified. The way in which
17417 the text is used to add header lines at transport time is described in section
17418 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
17419 message is in the process of being transported. This means that references to
17420 header lines in string expansions in the transport's configuration do not
17421 &"see"& the added header lines.
17423 The &%headers_add%& option is expanded after &%errors_to%&, but before
17424 &%headers_remove%& and &%transport%&. If an item is empty, or if
17425 an item expansion is forced to fail, the item has no effect. Other expansion
17426 failures are treated as configuration errors.
17428 Unlike most options, &%headers_add%& can be specified multiple times
17429 for a router; all listed headers are added.
17431 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
17432 router that has the &%one_time%& option set.
17434 .cindex "duplicate addresses"
17435 .oindex "&%unseen%&"
17436 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
17437 additions are deleted when the address is passed on to subsequent routers.
17438 For a &%redirect%& router, if a generated address is the same as the incoming
17439 address, this can lead to duplicate addresses with different header
17440 modifications. Exim does not do duplicate deliveries (except, in certain
17441 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
17442 which of the duplicates is discarded, so this ambiguous situation should be
17443 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
17447 .option headers_remove routers list&!! unset
17448 .cindex "header lines" "removing"
17449 .cindex "router" "removing header lines"
17450 This option specifies a list of text headers,
17451 colon-separated (by default, changeable in the usual way),
17452 that is associated with any addresses that are accepted by the router.
17453 Each item is separately expanded, at routing time. However, this
17454 option has no effect when an address is just being verified. The way in which
17455 the text is used to remove header lines at transport time is described in
17456 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
17457 the message is in the process of being transported. This means that references
17458 to header lines in string expansions in the transport's configuration still
17459 &"see"& the original header lines.
17461 The &%headers_remove%& option is expanded after &%errors_to%& and
17462 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
17463 the item has no effect. Other expansion failures are treated as configuration
17466 Unlike most options, &%headers_remove%& can be specified multiple times
17467 for a router; all listed headers are removed.
17469 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
17470 router that has the &%one_time%& option set.
17472 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
17473 removal requests are deleted when the address is passed on to subsequent
17474 routers, and this can lead to problems with duplicates -- see the similar
17475 warning for &%headers_add%& above.
17477 &*Warning 3*&: Because of the separate expansion of the list items,
17478 items that contain a list separator must have it doubled.
17479 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
17483 .option ignore_target_hosts routers "host list&!!" unset
17484 .cindex "IP address" "discarding"
17485 .cindex "router" "discarding IP addresses"
17486 Although this option is a host list, it should normally contain IP address
17487 entries rather than names. If any host that is looked up by the router has an
17488 IP address that matches an item in this list, Exim behaves as if that IP
17489 address did not exist. This option allows you to cope with rogue DNS entries
17492 remote.domain.example. A 127.0.0.1
17496 ignore_target_hosts = 127.0.0.1
17498 on the relevant router. If all the hosts found by a &(dnslookup)& router are
17499 discarded in this way, the router declines. In a conventional configuration, an
17500 attempt to mail to such a domain would normally provoke the &"unrouteable
17501 domain"& error, and an attempt to verify an address in the domain would fail.
17502 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
17503 router declines if presented with one of the listed addresses.
17505 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
17506 means of the first or the second of the following settings, respectively:
17508 ignore_target_hosts = 0.0.0.0/0
17509 ignore_target_hosts = <; 0::0/0
17511 The pattern in the first line matches all IPv4 addresses, whereas the pattern
17512 in the second line matches all IPv6 addresses.
17514 This option may also be useful for ignoring link-local and site-local IPv6
17515 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
17516 is expanded before use as a list, it is possible to make it dependent on the
17517 domain that is being routed.
17519 .vindex "&$host_address$&"
17520 During its expansion, &$host_address$& is set to the IP address that is being
17523 .option initgroups routers boolean false
17524 .cindex "additional groups"
17525 .cindex "groups" "additional"
17526 .cindex "local transports" "uid and gid"
17527 .cindex "transport" "local"
17528 If the router queues an address for a transport, and this option is true, and
17529 the uid supplied by the router is not overridden by the transport, the
17530 &[initgroups()]& function is called when running the transport to ensure that
17531 any additional groups associated with the uid are set up. See also &%group%&
17532 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
17536 .option local_part_prefix routers&!? "string list" unset
17537 .cindex "router" "prefix for local part"
17538 .cindex "prefix" "for local part, used in router"
17539 If this option is set, the router is skipped unless the local part starts with
17540 one of the given strings, or &%local_part_prefix_optional%& is true. See
17541 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
17544 The list is scanned from left to right, and the first prefix that matches is
17545 used. A limited form of wildcard is available; if the prefix begins with an
17546 asterisk, it matches the longest possible sequence of arbitrary characters at
17547 the start of the local part. An asterisk should therefore always be followed by
17548 some character that does not occur in normal local parts.
17549 .cindex "multiple mailboxes"
17550 .cindex "mailbox" "multiple"
17551 Wildcarding can be used to set up multiple user mailboxes, as described in
17552 section &<<SECTmulbox>>&.
17554 .vindex "&$local_part$&"
17555 .vindex "&$local_part_prefix$&"
17556 During the testing of the &%local_parts%& option, and while the router is
17557 running, the prefix is removed from the local part, and is available in the
17558 expansion variable &$local_part_prefix$&. When a message is being delivered, if
17559 the router accepts the address, this remains true during subsequent delivery by
17560 a transport. In particular, the local part that is transmitted in the RCPT
17561 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
17562 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
17563 the relevant transport.
17565 When an address is being verified, &%local_part_prefix%& affects only the
17566 behaviour of the router. If the callout feature of verification is in use, this
17567 means that the full address, including the prefix, will be used during the
17570 The prefix facility is commonly used to handle local parts of the form
17571 &%owner-something%&. Another common use is to support local parts of the form
17572 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
17573 to tell a user their forwarding is broken &-- by placing a router like this one
17574 immediately before the router that handles &_.forward_& files:
17578 local_part_prefix = real-
17580 transport = local_delivery
17582 For security, it would probably be a good idea to restrict the use of this
17583 router to locally-generated messages, using a condition such as this:
17585 condition = ${if match {$sender_host_address}\
17586 {\N^(|127\.0\.0\.1)$\N}}
17589 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
17590 both conditions must be met if not optional. Care must be taken if wildcards
17591 are used in both a prefix and a suffix on the same router. Different
17592 separator characters must be used to avoid ambiguity.
17595 .option local_part_prefix_optional routers boolean false
17596 See &%local_part_prefix%& above.
17600 .option local_part_suffix routers&!? "string list" unset
17601 .cindex "router" "suffix for local part"
17602 .cindex "suffix for local part" "used in router"
17603 This option operates in the same way as &%local_part_prefix%&, except that the
17604 local part must end (rather than start) with the given string, the
17605 &%local_part_suffix_optional%& option determines whether the suffix is
17606 mandatory, and the wildcard * character, if present, must be the last
17607 character of the suffix. This option facility is commonly used to handle local
17608 parts of the form &%something-request%& and multiple user mailboxes of the form
17612 .option local_part_suffix_optional routers boolean false
17613 See &%local_part_suffix%& above.
17617 .option local_parts routers&!? "local part list&!!" unset
17618 .cindex "router" "restricting to specific local parts"
17619 .cindex "local part" "checking in router"
17620 The router is run only if the local part of the address matches the list.
17621 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17623 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
17624 string is expanded, it is possible to make it depend on the domain, for
17627 local_parts = dbm;/usr/local/specials/$domain
17629 .vindex "&$local_part_data$&"
17630 If the match is achieved by a lookup, the data that the lookup returned
17631 for the local part is placed in the variable &$local_part_data$& for use in
17632 expansions of the router's private options. You might use this option, for
17633 example, if you have a large number of local virtual domains, and you want to
17634 send all postmaster mail to the same place without having to set up an alias in
17635 each virtual domain:
17639 local_parts = postmaster
17640 data = postmaster@real.domain.example
17644 .option log_as_local routers boolean "see below"
17645 .cindex "log" "delivery line"
17646 .cindex "delivery" "log line format"
17647 Exim has two logging styles for delivery, the idea being to make local
17648 deliveries stand out more visibly from remote ones. In the &"local"& style, the
17649 recipient address is given just as the local part, without a domain. The use of
17650 this style is controlled by this option. It defaults to true for the &(accept)&
17651 router, and false for all the others. This option applies only when a
17652 router assigns an address to a transport. It has no effect on routers that
17653 redirect addresses.
17657 .option more routers boolean&!! true
17658 The result of string expansion for this option must be a valid boolean value,
17659 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
17660 result causes an error, and delivery is deferred. If the expansion is forced to
17661 fail, the default value for the option (true) is used. Other failures cause
17662 delivery to be deferred.
17664 If this option is set false, and the router declines to handle the address, no
17665 further routers are tried, routing fails, and the address is bounced.
17667 However, if the router explicitly passes an address to the following router by
17668 means of the setting
17672 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
17673 does not affect the behaviour if one of the precondition tests fails. In that
17674 case, the address is always passed to the next router.
17676 Note that &%address_data%& is not considered to be a precondition. If its
17677 expansion is forced to fail, the router declines, and the value of &%more%&
17678 controls what happens next.
17681 .option pass_on_timeout routers boolean false
17682 .cindex "timeout" "of router"
17683 .cindex "router" "timeout"
17684 If a router times out during a host lookup, it normally causes deferral of the
17685 address. If &%pass_on_timeout%& is set, the address is passed on to the next
17686 router, overriding &%no_more%&. This may be helpful for systems that are
17687 intermittently connected to the Internet, or those that want to pass to a smart
17688 host any messages that cannot immediately be delivered.
17690 There are occasional other temporary errors that can occur while doing DNS
17691 lookups. They are treated in the same way as a timeout, and this option
17692 applies to all of them.
17696 .option pass_router routers string unset
17697 .cindex "router" "go to after &""pass""&"
17698 Routers that recognize the generic &%self%& option (&(dnslookup)&,
17699 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
17700 routing to continue, and overriding a false setting of &%more%&. When one of
17701 these routers returns &"pass"&, the address is normally handed on to the next
17702 router in sequence. This can be changed by setting &%pass_router%& to the name
17703 of another router. However (unlike &%redirect_router%&) the named router must
17704 be below the current router, to avoid loops. Note that this option applies only
17705 to the special case of &"pass"&. It does not apply when a router returns
17706 &"decline"& because it cannot handle an address.
17710 .option redirect_router routers string unset
17711 .cindex "router" "start at after redirection"
17712 Sometimes an administrator knows that it is pointless to reprocess addresses
17713 generated from alias or forward files with the same router again. For
17714 example, if an alias file translates real names into login ids there is no
17715 point searching the alias file a second time, especially if it is a large file.
17717 The &%redirect_router%& option can be set to the name of any router instance.
17718 It causes the routing of any generated addresses to start at the named router
17719 instead of at the first router. This option has no effect if the router in
17720 which it is set does not generate new addresses.
17724 .option require_files routers&!? "string list&!!" unset
17725 .cindex "file" "requiring for router"
17726 .cindex "router" "requiring file existence"
17727 This option provides a general mechanism for predicating the running of a
17728 router on the existence or non-existence of certain files or directories.
17729 Before running a router, as one of its precondition tests, Exim works its way
17730 through the &%require_files%& list, expanding each item separately.
17732 Because the list is split before expansion, any colons in expansion items must
17733 be doubled, or the facility for using a different list separator must be used.
17734 If any expansion is forced to fail, the item is ignored. Other expansion
17735 failures cause routing of the address to be deferred.
17737 If any expanded string is empty, it is ignored. Otherwise, except as described
17738 below, each string must be a fully qualified file path, optionally preceded by
17739 &"!"&. The paths are passed to the &[stat()]& function to test for the
17740 existence of the files or directories. The router is skipped if any paths not
17741 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
17744 If &[stat()]& cannot determine whether a file exists or not, delivery of
17745 the message is deferred. This can happen when NFS-mounted filesystems are
17748 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
17749 options, so you cannot use it to check for the existence of a file in which to
17750 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
17751 full list of the order in which preconditions are evaluated.) However, as
17752 these options are all expanded, you can use the &%exists%& expansion condition
17753 to make such tests. The &%require_files%& option is intended for checking files
17754 that the router may be going to use internally, or which are needed by a
17755 transport (for example &_.procmailrc_&).
17757 During delivery, the &[stat()]& function is run as root, but there is a
17758 facility for some checking of the accessibility of a file by another user.
17759 This is not a proper permissions check, but just a &"rough"& check that
17760 operates as follows:
17762 If an item in a &%require_files%& list does not contain any forward slash
17763 characters, it is taken to be the user (and optional group, separated by a
17764 comma) to be checked for subsequent files in the list. If no group is specified
17765 but the user is specified symbolically, the gid associated with the uid is
17768 require_files = mail:/some/file
17769 require_files = $local_part:$home/.procmailrc
17771 If a user or group name in a &%require_files%& list does not exist, the
17772 &%require_files%& condition fails.
17774 Exim performs the check by scanning along the components of the file path, and
17775 checking the access for the given uid and gid. It checks for &"x"& access on
17776 directories, and &"r"& access on the final file. Note that this means that file
17777 access control lists, if the operating system has them, are ignored.
17779 &*Warning 1*&: When the router is being run to verify addresses for an
17780 incoming SMTP message, Exim is not running as root, but under its own uid. This
17781 may affect the result of a &%require_files%& check. In particular, &[stat()]&
17782 may yield the error EACCES (&"Permission denied"&). This means that the Exim
17783 user is not permitted to read one of the directories on the file's path.
17785 &*Warning 2*&: Even when Exim is running as root while delivering a message,
17786 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
17787 without root access. In this case, if a check for access by a particular user
17788 is requested, Exim creates a subprocess that runs as that user, and tries the
17789 check again in that process.
17791 The default action for handling an unresolved EACCES is to consider it to
17792 be caused by a configuration error, and routing is deferred because the
17793 existence or non-existence of the file cannot be determined. However, in some
17794 circumstances it may be desirable to treat this condition as if the file did
17795 not exist. If the file name (or the exclamation mark that precedes the file
17796 name for non-existence) is preceded by a plus sign, the EACCES error is treated
17797 as if the file did not exist. For example:
17799 require_files = +/some/file
17801 If the router is not an essential part of verification (for example, it
17802 handles users' &_.forward_& files), another solution is to set the &%verify%&
17803 option false so that the router is skipped when verifying.
17807 .option retry_use_local_part routers boolean "see below"
17808 .cindex "hints database" "retry keys"
17809 .cindex "local part" "in retry keys"
17810 When a delivery suffers a temporary routing failure, a retry record is created
17811 in Exim's hints database. For addresses whose routing depends only on the
17812 domain, the key for the retry record should not involve the local part, but for
17813 other addresses, both the domain and the local part should be included.
17814 Usually, remote routing is of the former kind, and local routing is of the
17817 This option controls whether the local part is used to form the key for retry
17818 hints for addresses that suffer temporary errors while being handled by this
17819 router. The default value is true for any router that has &%check_local_user%&
17820 set, and false otherwise. Note that this option does not apply to hints keys
17821 for transport delays; they are controlled by a generic transport option of the
17824 The setting of &%retry_use_local_part%& applies only to the router on which it
17825 appears. If the router generates child addresses, they are routed
17826 independently; this setting does not become attached to them.
17830 .option router_home_directory routers string&!! unset
17831 .cindex "router" "home directory for"
17832 .cindex "home directory" "for router"
17834 This option sets a home directory for use while the router is running. (Compare
17835 &%transport_home_directory%&, which sets a home directory for later
17836 transporting.) In particular, if used on a &(redirect)& router, this option
17837 sets a value for &$home$& while a filter is running. The value is expanded;
17838 forced expansion failure causes the option to be ignored &-- other failures
17839 cause the router to defer.
17841 Expansion of &%router_home_directory%& happens immediately after the
17842 &%check_local_user%& test (if configured), before any further expansions take
17844 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17846 While the router is running, &%router_home_directory%& overrides the value of
17847 &$home$& that came from &%check_local_user%&.
17849 When a router accepts an address and assigns it to a local transport (including
17850 the cases when a &(redirect)& router generates a pipe, file, or autoreply
17851 delivery), the home directory setting for the transport is taken from the first
17852 of these values that is set:
17855 The &%home_directory%& option on the transport;
17857 The &%transport_home_directory%& option on the router;
17859 The password data if &%check_local_user%& is set on the router;
17861 The &%router_home_directory%& option on the router.
17864 In other words, &%router_home_directory%& overrides the password data for the
17865 router, but not for the transport.
17869 .option self routers string freeze
17870 .cindex "MX record" "pointing to local host"
17871 .cindex "local host" "MX pointing to"
17872 This option applies to those routers that use a recipient address to find a
17873 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
17874 and &(manualroute)& routers.
17875 Certain configurations of the &(queryprogram)& router can also specify a list
17877 Usually such routers are configured to send the message to a remote host via an
17878 &(smtp)& transport. The &%self%& option specifies what happens when the first
17879 host on the list turns out to be the local host.
17880 The way in which Exim checks for the local host is described in section
17881 &<<SECTreclocipadd>>&.
17883 Normally this situation indicates either an error in Exim's configuration (for
17884 example, the router should be configured not to process this domain), or an
17885 error in the DNS (for example, the MX should not point to this host). For this
17886 reason, the default action is to log the incident, defer the address, and
17887 freeze the message. The following alternatives are provided for use in special
17892 Delivery of the message is tried again later, but the message is not frozen.
17894 .vitem "&%reroute%&: <&'domain'&>"
17895 The domain is changed to the given domain, and the address is passed back to
17896 be reprocessed by the routers. No rewriting of headers takes place. This
17897 behaviour is essentially a redirection.
17899 .vitem "&%reroute: rewrite:%& <&'domain'&>"
17900 The domain is changed to the given domain, and the address is passed back to be
17901 reprocessed by the routers. Any headers that contain the original domain are
17906 .vindex "&$self_hostname$&"
17907 The router passes the address to the next router, or to the router named in the
17908 &%pass_router%& option if it is set. This overrides &%no_more%&. During
17909 subsequent routing and delivery, the variable &$self_hostname$& contains the
17910 name of the local host that the router encountered. This can be used to
17911 distinguish between different cases for hosts with multiple names. The
17917 ensures that only those addresses that routed to the local host are passed on.
17918 Without &%no_more%&, addresses that were declined for other reasons would also
17919 be passed to the next router.
17922 Delivery fails and an error report is generated.
17925 .cindex "local host" "sending to"
17926 The anomaly is ignored and the address is queued for the transport. This
17927 setting should be used with extreme caution. For an &(smtp)& transport, it
17928 makes sense only in cases where the program that is listening on the SMTP port
17929 is not this version of Exim. That is, it must be some other MTA, or Exim with a
17930 different configuration file that handles the domain in another way.
17935 .option senders routers&!? "address list&!!" unset
17936 .cindex "router" "checking senders"
17937 If this option is set, the router is skipped unless the message's sender
17938 address matches something on the list.
17939 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17942 There are issues concerning verification when the running of routers is
17943 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
17944 setting, it sets the sender to the null string. When using the &%-bt%& option
17945 to check a configuration file, it is necessary also to use the &%-f%& option to
17946 set an appropriate sender. For incoming mail, the sender is unset when
17947 verifying the sender, but is available when verifying any recipients. If the
17948 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
17952 .option translate_ip_address routers string&!! unset
17953 .cindex "IP address" "translating"
17954 .cindex "packet radio"
17955 .cindex "router" "IP address translation"
17956 There exist some rare networking situations (for example, packet radio) where
17957 it is helpful to be able to translate IP addresses generated by normal routing
17958 mechanisms into other IP addresses, thus performing a kind of manual IP
17959 routing. This should be done only if the normal IP routing of the TCP/IP stack
17960 is inadequate or broken. Because this is an extremely uncommon requirement, the
17961 code to support this option is not included in the Exim binary unless
17962 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
17964 .vindex "&$host_address$&"
17965 The &%translate_ip_address%& string is expanded for every IP address generated
17966 by the router, with the generated address set in &$host_address$&. If the
17967 expansion is forced to fail, no action is taken.
17968 For any other expansion error, delivery of the message is deferred.
17969 If the result of the expansion is an IP address, that replaces the original
17970 address; otherwise the result is assumed to be a host name &-- this is looked
17971 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
17972 produce one or more replacement IP addresses. For example, to subvert all IP
17973 addresses in some specific networks, this could be added to a router:
17975 translate_ip_address = \
17976 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
17979 The file would contain lines like
17981 10.2.3.128/26 some.host
17982 10.8.4.34/26 10.44.8.15
17984 You should not make use of this facility unless you really understand what you
17989 .option transport routers string&!! unset
17990 This option specifies the transport to be used when a router accepts an address
17991 and sets it up for delivery. A transport is never needed if a router is used
17992 only for verification. The value of the option is expanded at routing time,
17993 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
17994 and result must be the name of one of the configured transports. If it is not,
17995 delivery is deferred.
17997 The &%transport%& option is not used by the &(redirect)& router, but it does
17998 have some private options that set up transports for pipe and file deliveries
17999 (see chapter &<<CHAPredirect>>&).
18003 .option transport_current_directory routers string&!! unset
18004 .cindex "current directory for local transport"
18005 This option associates a current directory with any address that is routed
18006 to a local transport. This can happen either because a transport is
18007 explicitly configured for the router, or because it generates a delivery to a
18008 file or a pipe. During the delivery process (that is, at transport time), this
18009 option string is expanded and is set as the current directory, unless
18010 overridden by a setting on the transport.
18011 If the expansion fails for any reason, including forced failure, an error is
18012 logged, and delivery is deferred.
18013 See chapter &<<CHAPenvironment>>& for details of the local delivery
18019 .option transport_home_directory routers string&!! "see below"
18020 .cindex "home directory" "for local transport"
18021 This option associates a home directory with any address that is routed to a
18022 local transport. This can happen either because a transport is explicitly
18023 configured for the router, or because it generates a delivery to a file or a
18024 pipe. During the delivery process (that is, at transport time), the option
18025 string is expanded and is set as the home directory, unless overridden by a
18026 setting of &%home_directory%& on the transport.
18027 If the expansion fails for any reason, including forced failure, an error is
18028 logged, and delivery is deferred.
18030 If the transport does not specify a home directory, and
18031 &%transport_home_directory%& is not set for the router, the home directory for
18032 the transport is taken from the password data if &%check_local_user%& is set for
18033 the router. Otherwise it is taken from &%router_home_directory%& if that option
18034 is set; if not, no home directory is set for the transport.
18036 See chapter &<<CHAPenvironment>>& for further details of the local delivery
18042 .option unseen routers boolean&!! false
18043 .cindex "router" "carrying on after success"
18044 The result of string expansion for this option must be a valid boolean value,
18045 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
18046 result causes an error, and delivery is deferred. If the expansion is forced to
18047 fail, the default value for the option (false) is used. Other failures cause
18048 delivery to be deferred.
18050 When this option is set true, routing does not cease if the router accepts the
18051 address. Instead, a copy of the incoming address is passed to the next router,
18052 overriding a false setting of &%more%&. There is little point in setting
18053 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
18054 the value of &%unseen%& contains expansion items (and therefore, presumably, is
18055 sometimes true and sometimes false).
18057 .cindex "copy of message (&%unseen%& option)"
18058 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
18059 qualifier in filter files. It can be used to cause copies of messages to be
18060 delivered to some other destination, while also carrying out a normal delivery.
18061 In effect, the current address is made into a &"parent"& that has two children
18062 &-- one that is delivered as specified by this router, and a clone that goes on
18063 to be routed further. For this reason, &%unseen%& may not be combined with the
18064 &%one_time%& option in a &(redirect)& router.
18066 &*Warning*&: Header lines added to the address (or specified for removal) by
18067 this router or by previous routers affect the &"unseen"& copy of the message
18068 only. The clone that continues to be processed by further routers starts with
18069 no added headers and none specified for removal. For a &%redirect%& router, if
18070 a generated address is the same as the incoming address, this can lead to
18071 duplicate addresses with different header modifications. Exim does not do
18072 duplicate deliveries (except, in certain circumstances, to pipes -- see section
18073 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
18074 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
18075 &%redirect%& router may be of help.
18077 Unlike the handling of header modifications, any data that was set by the
18078 &%address_data%& option in the current or previous routers &'is'& passed on to
18079 subsequent routers.
18082 .option user routers string&!! "see below"
18083 .cindex "uid (user id)" "local delivery"
18084 .cindex "local transports" "uid and gid"
18085 .cindex "transport" "local"
18086 .cindex "router" "user for filter processing"
18087 .cindex "filter" "user for processing"
18088 When a router queues an address for a transport, and the transport does not
18089 specify a user, the user given here is used when running the delivery process.
18090 The user may be specified numerically or by name. If expansion fails, the
18091 error is logged and delivery is deferred.
18092 This user is also used by the &(redirect)& router when running a filter file.
18093 The default is unset, except when &%check_local_user%& is set. In this case,
18094 the default is taken from the password information. If the user is specified as
18095 a name, and &%group%& is not set, the group associated with the user is used.
18096 See also &%initgroups%& and &%group%& and the discussion in chapter
18097 &<<CHAPenvironment>>&.
18101 .option verify routers&!? boolean true
18102 Setting this option has the effect of setting &%verify_sender%& and
18103 &%verify_recipient%& to the same value.
18106 .option verify_only routers&!? boolean false
18107 .cindex "EXPN" "with &%verify_only%&"
18109 .cindex "router" "used only when verifying"
18110 If this option is set, the router is used only when verifying an address,
18111 delivering in cutthrough mode or
18112 testing with the &%-bv%& option, not when actually doing a delivery, testing
18113 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
18114 restricted to verifying only senders or recipients by means of
18115 &%verify_sender%& and &%verify_recipient%&.
18117 &*Warning*&: When the router is being run to verify addresses for an incoming
18118 SMTP message, Exim is not running as root, but under its own uid. If the router
18119 accesses any files, you need to make sure that they are accessible to the Exim
18123 .option verify_recipient routers&!? boolean true
18124 If this option is false, the router is skipped when verifying recipient
18126 delivering in cutthrough mode
18127 or testing recipient verification using &%-bv%&.
18128 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18130 See also the &$verify_mode$& variable.
18133 .option verify_sender routers&!? boolean true
18134 If this option is false, the router is skipped when verifying sender addresses
18135 or testing sender verification using &%-bvs%&.
18136 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18138 See also the &$verify_mode$& variable.
18139 .ecindex IIDgenoprou1
18140 .ecindex IIDgenoprou2
18147 . ////////////////////////////////////////////////////////////////////////////
18148 . ////////////////////////////////////////////////////////////////////////////
18150 .chapter "The accept router" "CHID4"
18151 .cindex "&(accept)& router"
18152 .cindex "routers" "&(accept)&"
18153 The &(accept)& router has no private options of its own. Unless it is being
18154 used purely for verification (see &%verify_only%&) a transport is required to
18155 be defined by the generic &%transport%& option. If the preconditions that are
18156 specified by generic options are met, the router accepts the address and queues
18157 it for the given transport. The most common use of this router is for setting
18158 up deliveries to local mailboxes. For example:
18162 domains = mydomain.example
18164 transport = local_delivery
18166 The &%domains%& condition in this example checks the domain of the address, and
18167 &%check_local_user%& checks that the local part is the login of a local user.
18168 When both preconditions are met, the &(accept)& router runs, and queues the
18169 address for the &(local_delivery)& transport.
18176 . ////////////////////////////////////////////////////////////////////////////
18177 . ////////////////////////////////////////////////////////////////////////////
18179 .chapter "The dnslookup router" "CHAPdnslookup"
18180 .scindex IIDdnsrou1 "&(dnslookup)& router"
18181 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
18182 The &(dnslookup)& router looks up the hosts that handle mail for the
18183 recipient's domain in the DNS. A transport must always be set for this router,
18184 unless &%verify_only%& is set.
18186 If SRV support is configured (see &%check_srv%& below), Exim first searches for
18187 SRV records. If none are found, or if SRV support is not configured,
18188 MX records are looked up. If no MX records exist, address records are sought.
18189 However, &%mx_domains%& can be set to disable the direct use of address
18192 MX records of equal priority are sorted by Exim into a random order. Exim then
18193 looks for address records for the host names obtained from MX or SRV records.
18194 When a host has more than one IP address, they are sorted into a random order,
18195 except that IPv6 addresses are always sorted before IPv4 addresses. If all the
18196 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
18197 generic option, the router declines.
18199 Unless they have the highest priority (lowest MX value), MX records that point
18200 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
18201 are discarded, together with any other MX records of equal or lower priority.
18203 .cindex "MX record" "pointing to local host"
18204 .cindex "local host" "MX pointing to"
18205 .oindex "&%self%&" "in &(dnslookup)& router"
18206 If the host pointed to by the highest priority MX record, or looked up as an
18207 address record, is the local host, or matches &%hosts_treat_as_local%&, what
18208 happens is controlled by the generic &%self%& option.
18211 .section "Problems with DNS lookups" "SECTprowitdnsloo"
18212 There have been problems with DNS servers when SRV records are looked up.
18213 Some misbehaving servers return a DNS error or timeout when a non-existent
18214 SRV record is sought. Similar problems have in the past been reported for
18215 MX records. The global &%dns_again_means_nonexist%& option can help with this
18216 problem, but it is heavy-handed because it is a global option.
18218 For this reason, there are two options, &%srv_fail_domains%& and
18219 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
18220 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
18221 an attempt to look up an SRV or MX record causes one of these results, and the
18222 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
18223 such record"&. In the case of an SRV lookup, this means that the router
18224 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
18225 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
18226 case routing fails.
18229 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
18230 .cindex "&(dnslookup)& router" "declines"
18231 There are a few cases where a &(dnslookup)& router will decline to accept
18232 an address; if such a router is expected to handle "all remaining non-local
18233 domains", then it is important to set &%no_more%&.
18235 The router will defer rather than decline if the domain
18236 is found in the &%fail_defer_domains%& router option.
18238 Reasons for a &(dnslookup)& router to decline currently include:
18240 The domain does not exist in DNS
18242 The domain exists but the MX record's host part is just "."; this is a common
18243 convention (borrowed from SRV) used to indicate that there is no such service
18244 for this domain and to not fall back to trying A/AAAA records.
18246 Ditto, but for SRV records, when &%check_srv%& is set on this router.
18248 MX record points to a non-existent host.
18250 MX record points to an IP address and the main section option
18251 &%allow_mx_to_ip%& is not set.
18253 MX records exist and point to valid hosts, but all hosts resolve only to
18254 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
18256 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
18257 &%dns_check_names_pattern%& for handling one variant of this)
18259 &%check_secondary_mx%& is set on this router but the local host can
18260 not be found in the MX records (see below)
18266 .section "Private options for dnslookup" "SECID118"
18267 .cindex "options" "&(dnslookup)& router"
18268 The private options for the &(dnslookup)& router are as follows:
18270 .option check_secondary_mx dnslookup boolean false
18271 .cindex "MX record" "checking for secondary"
18272 If this option is set, the router declines unless the local host is found in
18273 (and removed from) the list of hosts obtained by MX lookup. This can be used to
18274 process domains for which the local host is a secondary mail exchanger
18275 differently to other domains. The way in which Exim decides whether a host is
18276 the local host is described in section &<<SECTreclocipadd>>&.
18279 .option check_srv dnslookup string&!! unset
18280 .cindex "SRV record" "enabling use of"
18281 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
18282 addition to MX and address records. The support is disabled by default. To
18283 enable SRV support, set the &%check_srv%& option to the name of the service
18284 required. For example,
18288 looks for SRV records that refer to the normal smtp service. The option is
18289 expanded, so the service name can vary from message to message or address
18290 to address. This might be helpful if SRV records are being used for a
18291 submission service. If the expansion is forced to fail, the &%check_srv%&
18292 option is ignored, and the router proceeds to look for MX records in the
18295 When the expansion succeeds, the router searches first for SRV records for
18296 the given service (it assumes TCP protocol). A single SRV record with a
18297 host name that consists of just a single dot indicates &"no such service for
18298 this domain"&; if this is encountered, the router declines. If other kinds of
18299 SRV record are found, they are used to construct a host list for delivery
18300 according to the rules of RFC 2782. MX records are not sought in this case.
18302 When no SRV records are found, MX records (and address records) are sought in
18303 the traditional way. In other words, SRV records take precedence over MX
18304 records, just as MX records take precedence over address records. Note that
18305 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
18306 defined it. It is apparently believed that MX records are sufficient for email
18307 and that SRV records should not be used for this purpose. However, SRV records
18308 have an additional &"weight"& feature which some people might find useful when
18309 trying to split an SMTP load between hosts of different power.
18311 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
18312 when there is a DNS lookup error.
18317 .option fail_defer_domains dnslookup "domain list&!!" unset
18318 .cindex "MX record" "not found"
18319 DNS lookups for domains matching &%fail_defer_domains%&
18320 which find no matching record will cause the router to defer
18321 rather than the default behaviour of decline.
18322 This maybe be useful for queueing messages for a newly created
18323 domain while the DNS configuration is not ready.
18324 However, it will result in any message with mistyped domains
18328 .option mx_domains dnslookup "domain list&!!" unset
18329 .cindex "MX record" "required to exist"
18330 .cindex "SRV record" "required to exist"
18331 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
18332 record in order to be recognized. (The name of this option could be improved.)
18333 For example, if all the mail hosts in &'fict.example'& are known to have MX
18334 records, except for those in &'discworld.fict.example'&, you could use this
18337 mx_domains = ! *.discworld.fict.example : *.fict.example
18339 This specifies that messages addressed to a domain that matches the list but
18340 has no MX record should be bounced immediately instead of being routed using
18341 the address record.
18344 .option mx_fail_domains dnslookup "domain list&!!" unset
18345 If the DNS lookup for MX records for one of the domains in this list causes a
18346 DNS lookup error, Exim behaves as if no MX records were found. See section
18347 &<<SECTprowitdnsloo>>& for more discussion.
18352 .option qualify_single dnslookup boolean true
18353 .cindex "DNS" "resolver options"
18354 .cindex "DNS" "qualifying single-component names"
18355 When this option is true, the resolver option RES_DEFNAMES is set for DNS
18356 lookups. Typically, but not standardly, this causes the resolver to qualify
18357 single-component names with the default domain. For example, on a machine
18358 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
18359 &'thesaurus.ref.example'& inside the resolver. For details of what your
18360 resolver actually does, consult your man pages for &'resolver'& and
18365 .option rewrite_headers dnslookup boolean true
18366 .cindex "rewriting" "header lines"
18367 .cindex "header lines" "rewriting"
18368 If the domain name in the address that is being processed is not fully
18369 qualified, it may be expanded to its full form by a DNS lookup. For example, if
18370 an address is specified as &'dormouse@teaparty'&, the domain might be
18371 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
18372 occur as a result of setting the &%widen_domains%& option. If
18373 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
18374 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
18375 header lines of the message are rewritten with the full domain name.
18377 This option should be turned off only when it is known that no message is
18378 ever going to be sent outside an environment where the abbreviation makes
18381 When an MX record is looked up in the DNS and matches a wildcard record, name
18382 servers normally return a record containing the name that has been looked up,
18383 making it impossible to detect whether a wildcard was present or not. However,
18384 some name servers have recently been seen to return the wildcard entry. If the
18385 name returned by a DNS lookup begins with an asterisk, it is not used for
18389 .option same_domain_copy_routing dnslookup boolean false
18390 .cindex "address" "copying routing"
18391 Addresses with the same domain are normally routed by the &(dnslookup)& router
18392 to the same list of hosts. However, this cannot be presumed, because the router
18393 options and preconditions may refer to the local part of the address. By
18394 default, therefore, Exim routes each address in a message independently. DNS
18395 servers run caches, so repeated DNS lookups are not normally expensive, and in
18396 any case, personal messages rarely have more than a few recipients.
18398 If you are running mailing lists with large numbers of subscribers at the same
18399 domain, and you are using a &(dnslookup)& router which is independent of the
18400 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
18401 lookups for identical domains in one message. In this case, when &(dnslookup)&
18402 routes an address to a remote transport, any other unrouted addresses in the
18403 message that have the same domain are automatically given the same routing
18404 without processing them independently,
18405 provided the following conditions are met:
18408 No router that processed the address specified &%headers_add%& or
18409 &%headers_remove%&.
18411 The router did not change the address in any way, for example, by &"widening"&
18418 .option search_parents dnslookup boolean false
18419 .cindex "DNS" "resolver options"
18420 When this option is true, the resolver option RES_DNSRCH is set for DNS
18421 lookups. This is different from the &%qualify_single%& option in that it
18422 applies to domains containing dots. Typically, but not standardly, it causes
18423 the resolver to search for the name in the current domain and in parent
18424 domains. For example, on a machine in the &'fict.example'& domain, if looking
18425 up &'teaparty.wonderland'& failed, the resolver would try
18426 &'teaparty.wonderland.fict.example'&. For details of what your resolver
18427 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
18429 Setting this option true can cause problems in domains that have a wildcard MX
18430 record, because any domain that does not have its own MX record matches the
18435 .option srv_fail_domains dnslookup "domain list&!!" unset
18436 If the DNS lookup for SRV records for one of the domains in this list causes a
18437 DNS lookup error, Exim behaves as if no SRV records were found. See section
18438 &<<SECTprowitdnsloo>>& for more discussion.
18443 .option widen_domains dnslookup "string list" unset
18444 .cindex "domain" "partial; widening"
18445 If a DNS lookup fails and this option is set, each of its strings in turn is
18446 added onto the end of the domain, and the lookup is tried again. For example,
18449 widen_domains = fict.example:ref.example
18451 is set and a lookup of &'klingon.dictionary'& fails,
18452 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
18453 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
18454 and &%search_parents%& options can cause some widening to be undertaken inside
18455 the DNS resolver. &%widen_domains%& is not applied to sender addresses
18456 when verifying, unless &%rewrite_headers%& is false (not the default).
18459 .section "Effect of qualify_single and search_parents" "SECID119"
18460 When a domain from an envelope recipient is changed by the resolver as a result
18461 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
18462 corresponding address in the message's header lines unless &%rewrite_headers%&
18463 is set false. Exim then re-routes the address, using the full domain.
18465 These two options affect only the DNS lookup that takes place inside the router
18466 for the domain of the address that is being routed. They do not affect lookups
18467 such as that implied by
18471 that may happen while processing a router precondition before the router is
18472 entered. No widening ever takes place for these lookups.
18473 .ecindex IIDdnsrou1
18474 .ecindex IIDdnsrou2
18484 . ////////////////////////////////////////////////////////////////////////////
18485 . ////////////////////////////////////////////////////////////////////////////
18487 .chapter "The ipliteral router" "CHID5"
18488 .cindex "&(ipliteral)& router"
18489 .cindex "domain literal" "routing"
18490 .cindex "routers" "&(ipliteral)&"
18491 This router has no private options. Unless it is being used purely for
18492 verification (see &%verify_only%&) a transport is required to be defined by the
18493 generic &%transport%& option. The router accepts the address if its domain part
18494 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
18495 router handles the address
18499 by setting up delivery to the host with that IP address. IPv4 domain literals
18500 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
18501 are similar, but the address is preceded by &`ipv6:`&. For example:
18503 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
18505 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
18506 grounds that sooner or later somebody will try it.
18508 .oindex "&%self%&" "in &(ipliteral)& router"
18509 If the IP address matches something in &%ignore_target_hosts%&, the router
18510 declines. If an IP literal turns out to refer to the local host, the generic
18511 &%self%& option determines what happens.
18513 The RFCs require support for domain literals; however, their use is
18514 controversial in today's Internet. If you want to use this router, you must
18515 also set the main configuration option &%allow_domain_literals%&. Otherwise,
18516 Exim will not recognize the domain literal syntax in addresses.
18520 . ////////////////////////////////////////////////////////////////////////////
18521 . ////////////////////////////////////////////////////////////////////////////
18523 .chapter "The iplookup router" "CHID6"
18524 .cindex "&(iplookup)& router"
18525 .cindex "routers" "&(iplookup)&"
18526 The &(iplookup)& router was written to fulfil a specific requirement in
18527 Cambridge University (which in fact no longer exists). For this reason, it is
18528 not included in the binary of Exim by default. If you want to include it, you
18531 ROUTER_IPLOOKUP=yes
18533 in your &_Local/Makefile_& configuration file.
18535 The &(iplookup)& router routes an address by sending it over a TCP or UDP
18536 connection to one or more specific hosts. The host can then return the same or
18537 a different address &-- in effect rewriting the recipient address in the
18538 message's envelope. The new address is then passed on to subsequent routers. If
18539 this process fails, the address can be passed on to other routers, or delivery
18540 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
18541 must not be specified for it.
18543 .cindex "options" "&(iplookup)& router"
18544 .option hosts iplookup string unset
18545 This option must be supplied. Its value is a colon-separated list of host
18546 names. The hosts are looked up using &[gethostbyname()]&
18547 (or &[getipnodebyname()]& when available)
18548 and are tried in order until one responds to the query. If none respond, what
18549 happens is controlled by &%optional%&.
18552 .option optional iplookup boolean false
18553 If &%optional%& is true, if no response is obtained from any host, the address
18554 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
18555 delivery to the address is deferred.
18558 .option port iplookup integer 0
18559 .cindex "port" "&(iplookup)& router"
18560 This option must be supplied. It specifies the port number for the TCP or UDP
18564 .option protocol iplookup string udp
18565 This option can be set to &"udp"& or &"tcp"& to specify which of the two
18566 protocols is to be used.
18569 .option query iplookup string&!! "see below"
18570 This defines the content of the query that is sent to the remote hosts. The
18573 $local_part@$domain $local_part@$domain
18575 The repetition serves as a way of checking that a response is to the correct
18576 query in the default case (see &%response_pattern%& below).
18579 .option reroute iplookup string&!! unset
18580 If this option is not set, the rerouted address is precisely the byte string
18581 returned by the remote host, up to the first white space, if any. If set, the
18582 string is expanded to form the rerouted address. It can include parts matched
18583 in the response by &%response_pattern%& by means of numeric variables such as
18584 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
18585 whether or not a pattern is in use. In all cases, the rerouted address must end
18586 up in the form &'local_part@domain'&.
18589 .option response_pattern iplookup string unset
18590 This option can be set to a regular expression that is applied to the string
18591 returned from the remote host. If the pattern does not match the response, the
18592 router declines. If &%response_pattern%& is not set, no checking of the
18593 response is done, unless the query was defaulted, in which case there is a
18594 check that the text returned after the first white space is the original
18595 address. This checks that the answer that has been received is in response to
18596 the correct question. For example, if the response is just a new domain, the
18597 following could be used:
18599 response_pattern = ^([^@]+)$
18600 reroute = $local_part@$1
18603 .option timeout iplookup time 5s
18604 This specifies the amount of time to wait for a response from the remote
18605 machine. The same timeout is used for the &[connect()]& function for a TCP
18606 call. It does not apply to UDP.
18611 . ////////////////////////////////////////////////////////////////////////////
18612 . ////////////////////////////////////////////////////////////////////////////
18614 .chapter "The manualroute router" "CHID7"
18615 .scindex IIDmanrou1 "&(manualroute)& router"
18616 .scindex IIDmanrou2 "routers" "&(manualroute)&"
18617 .cindex "domain" "manually routing"
18618 The &(manualroute)& router is so-called because it provides a way of manually
18619 routing an address according to its domain. It is mainly used when you want to
18620 route addresses to remote hosts according to your own rules, bypassing the
18621 normal DNS routing that looks up MX records. However, &(manualroute)& can also
18622 route to local transports, a facility that may be useful if you want to save
18623 messages for dial-in hosts in local files.
18625 The &(manualroute)& router compares a list of domain patterns with the domain
18626 it is trying to route. If there is no match, the router declines. Each pattern
18627 has associated with it a list of hosts and some other optional data, which may
18628 include a transport. The combination of a pattern and its data is called a
18629 &"routing rule"&. For patterns that do not have an associated transport, the
18630 generic &%transport%& option must specify a transport, unless the router is
18631 being used purely for verification (see &%verify_only%&).
18634 In the case of verification, matching the domain pattern is sufficient for the
18635 router to accept the address. When actually routing an address for delivery,
18636 an address that matches a domain pattern is queued for the associated
18637 transport. If the transport is not a local one, a host list must be associated
18638 with the pattern; IP addresses are looked up for the hosts, and these are
18639 passed to the transport along with the mail address. For local transports, a
18640 host list is optional. If it is present, it is passed in &$host$& as a single
18643 The list of routing rules can be provided as an inline string in
18644 &%route_list%&, or the data can be obtained by looking up the domain in a file
18645 or database by setting &%route_data%&. Only one of these settings may appear in
18646 any one instance of &(manualroute)&. The format of routing rules is described
18647 below, following the list of private options.
18650 .section "Private options for manualroute" "SECTprioptman"
18652 .cindex "options" "&(manualroute)& router"
18653 The private options for the &(manualroute)& router are as follows:
18655 .option host_all_ignored manualroute string defer
18656 See &%host_find_failed%&.
18658 .option host_find_failed manualroute string freeze
18659 This option controls what happens when &(manualroute)& tries to find an IP
18660 address for a host, and the host does not exist. The option can be set to one
18661 of the following values:
18670 The default (&"freeze"&) assumes that this state is a serious configuration
18671 error. The difference between &"pass"& and &"decline"& is that the former
18672 forces the address to be passed to the next router (or the router defined by
18675 overriding &%no_more%&, whereas the latter passes the address to the next
18676 router only if &%more%& is true.
18678 The value &"ignore"& causes Exim to completely ignore a host whose IP address
18679 cannot be found. If all the hosts in the list are ignored, the behaviour is
18680 controlled by the &%host_all_ignored%& option. This takes the same values
18681 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
18683 The &%host_find_failed%& option applies only to a definite &"does not exist"&
18684 state; if a host lookup gets a temporary error, delivery is deferred unless the
18685 generic &%pass_on_timeout%& option is set.
18688 .option hosts_randomize manualroute boolean false
18689 .cindex "randomized host list"
18690 .cindex "host" "list of; randomized"
18691 If this option is set, the order of the items in a host list in a routing rule
18692 is randomized each time the list is used, unless an option in the routing rule
18693 overrides (see below). Randomizing the order of a host list can be used to do
18694 crude load sharing. However, if more than one mail address is routed by the
18695 same router to the same host list, the host lists are considered to be the same
18696 (even though they may be randomized into different orders) for the purpose of
18697 deciding whether to batch the deliveries into a single SMTP transaction.
18699 When &%hosts_randomize%& is true, a host list may be split
18700 into groups whose order is separately randomized. This makes it possible to
18701 set up MX-like behaviour. The boundaries between groups are indicated by an
18702 item that is just &`+`& in the host list. For example:
18704 route_list = * host1:host2:host3:+:host4:host5
18706 The order of the first three hosts and the order of the last two hosts is
18707 randomized for each use, but the first three always end up before the last two.
18708 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
18709 randomized host list is passed to an &(smtp)& transport that also has
18710 &%hosts_randomize set%&, the list is not re-randomized.
18713 .option route_data manualroute string&!! unset
18714 If this option is set, it must expand to yield the data part of a routing rule.
18715 Typically, the expansion string includes a lookup based on the domain. For
18718 route_data = ${lookup{$domain}dbm{/etc/routes}}
18720 If the expansion is forced to fail, or the result is an empty string, the
18721 router declines. Other kinds of expansion failure cause delivery to be
18725 .option route_list manualroute "string list" unset
18726 This string is a list of routing rules, in the form defined below. Note that,
18727 unlike most string lists, the items are separated by semicolons. This is so
18728 that they may contain colon-separated host lists.
18731 .option same_domain_copy_routing manualroute boolean false
18732 .cindex "address" "copying routing"
18733 Addresses with the same domain are normally routed by the &(manualroute)&
18734 router to the same list of hosts. However, this cannot be presumed, because the
18735 router options and preconditions may refer to the local part of the address. By
18736 default, therefore, Exim routes each address in a message independently. DNS
18737 servers run caches, so repeated DNS lookups are not normally expensive, and in
18738 any case, personal messages rarely have more than a few recipients.
18740 If you are running mailing lists with large numbers of subscribers at the same
18741 domain, and you are using a &(manualroute)& router which is independent of the
18742 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
18743 lookups for identical domains in one message. In this case, when
18744 &(manualroute)& routes an address to a remote transport, any other unrouted
18745 addresses in the message that have the same domain are automatically given the
18746 same routing without processing them independently. However, this is only done
18747 if &%headers_add%& and &%headers_remove%& are unset.
18752 .section "Routing rules in route_list" "SECID120"
18753 The value of &%route_list%& is a string consisting of a sequence of routing
18754 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
18755 entered as two semicolons. Alternatively, the list separator can be changed as
18756 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
18757 Empty rules are ignored. The format of each rule is
18759 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
18761 The following example contains two rules, each with a simple domain pattern and
18765 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
18766 thes.ref.example mail-3.ref.example:mail-4.ref.example
18768 The three parts of a rule are separated by white space. The pattern and the
18769 list of hosts can be enclosed in quotes if necessary, and if they are, the
18770 usual quoting rules apply. Each rule in a &%route_list%& must start with a
18771 single domain pattern, which is the only mandatory item in the rule. The
18772 pattern is in the same format as one item in a domain list (see section
18773 &<<SECTdomainlist>>&),
18774 except that it may not be the name of an interpolated file.
18775 That is, it may be wildcarded, or a regular expression, or a file or database
18776 lookup (with semicolons doubled, because of the use of semicolon as a separator
18777 in a &%route_list%&).
18779 The rules in &%route_list%& are searched in order until one of the patterns
18780 matches the domain that is being routed. The list of hosts and then options are
18781 then used as described below. If there is no match, the router declines. When
18782 &%route_list%& is set, &%route_data%& must not be set.
18786 .section "Routing rules in route_data" "SECID121"
18787 The use of &%route_list%& is convenient when there are only a small number of
18788 routing rules. For larger numbers, it is easier to use a file or database to
18789 hold the routing information, and use the &%route_data%& option instead.
18790 The value of &%route_data%& is a list of hosts, followed by (optional) options.
18791 Most commonly, &%route_data%& is set as a string that contains an
18792 expansion lookup. For example, suppose we place two routing rules in a file
18795 dict.ref.example: mail-1.ref.example:mail-2.ref.example
18796 thes.ref.example: mail-3.ref.example:mail-4.ref.example
18798 This data can be accessed by setting
18800 route_data = ${lookup{$domain}lsearch{/the/file/name}}
18802 Failure of the lookup results in an empty string, causing the router to
18803 decline. However, you do not have to use a lookup in &%route_data%&. The only
18804 requirement is that the result of expanding the string is a list of hosts,
18805 possibly followed by options, separated by white space. The list of hosts must
18806 be enclosed in quotes if it contains white space.
18811 .section "Format of the list of hosts" "SECID122"
18812 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
18813 always separately expanded before use. If the expansion fails, the router
18814 declines. The result of the expansion must be a colon-separated list of names
18815 and/or IP addresses, optionally also including ports. The format of each item
18816 in the list is described in the next section. The list separator can be changed
18817 as described in section &<<SECTlistconstruct>>&.
18819 If the list of hosts was obtained from a &%route_list%& item, the following
18820 variables are set during its expansion:
18823 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
18824 If the domain was matched against a regular expression, the numeric variables
18825 &$1$&, &$2$&, etc. may be set. For example:
18827 route_list = ^domain(\d+) host-$1.text.example
18830 &$0$& is always set to the entire domain.
18832 &$1$& is also set when partial matching is done in a file lookup.
18835 .vindex "&$value$&"
18836 If the pattern that matched the domain was a lookup item, the data that was
18837 looked up is available in the expansion variable &$value$&. For example:
18839 route_list = lsearch;;/some/file.routes $value
18843 Note the doubling of the semicolon in the pattern that is necessary because
18844 semicolon is the default route list separator.
18848 .section "Format of one host item" "SECTformatonehostitem"
18849 Each item in the list of hosts is either a host name or an IP address,
18850 optionally with an attached port number. When no port is given, an IP address
18851 is not enclosed in brackets. When a port is specified, it overrides the port
18852 specification on the transport. The port is separated from the name or address
18853 by a colon. This leads to some complications:
18856 Because colon is the default separator for the list of hosts, either
18857 the colon that specifies a port must be doubled, or the list separator must
18858 be changed. The following two examples have the same effect:
18860 route_list = * "host1.tld::1225 : host2.tld::1226"
18861 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
18864 When IPv6 addresses are involved, it gets worse, because they contain
18865 colons of their own. To make this case easier, it is permitted to
18866 enclose an IP address (either v4 or v6) in square brackets if a port
18867 number follows. For example:
18869 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
18873 .section "How the list of hosts is used" "SECThostshowused"
18874 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
18875 the hosts is tried, in the order specified, when carrying out the SMTP
18876 delivery. However, the order can be changed by setting the &%hosts_randomize%&
18877 option, either on the router (see section &<<SECTprioptman>>& above), or on the
18880 Hosts may be listed by name or by IP address. An unadorned name in the list of
18881 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
18882 interpreted as an indirection to a sublist of hosts obtained by looking up MX
18883 records in the DNS. For example:
18885 route_list = * x.y.z:p.q.r/MX:e.f.g
18887 If this feature is used with a port specifier, the port must come last. For
18890 route_list = * dom1.tld/mx::1225
18892 If the &%hosts_randomize%& option is set, the order of the items in the list is
18893 randomized before any lookups are done. Exim then scans the list; for any name
18894 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
18895 be an interface on the local host and the item is not the first in the list,
18896 Exim discards it and any subsequent items. If it is the first item, what
18897 happens is controlled by the
18898 .oindex "&%self%&" "in &(manualroute)& router"
18899 &%self%& option of the router.
18901 A name on the list that is followed by &`/MX`& is replaced with the list of
18902 hosts obtained by looking up MX records for the name. This is always a DNS
18903 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
18904 below) are not relevant here. The order of these hosts is determined by the
18905 preference values in the MX records, according to the usual rules. Because
18906 randomizing happens before the MX lookup, it does not affect the order that is
18907 defined by MX preferences.
18909 If the local host is present in the sublist obtained from MX records, but is
18910 not the most preferred host in that list, it and any equally or less
18911 preferred hosts are removed before the sublist is inserted into the main list.
18913 If the local host is the most preferred host in the MX list, what happens
18914 depends on where in the original list of hosts the &`/MX`& item appears. If it
18915 is not the first item (that is, there are previous hosts in the main list),
18916 Exim discards this name and any subsequent items in the main list.
18918 If the MX item is first in the list of hosts, and the local host is the
18919 most preferred host, what happens is controlled by the &%self%& option of the
18922 DNS failures when lookup up the MX records are treated in the same way as DNS
18923 failures when looking up IP addresses: &%pass_on_timeout%& and
18924 &%host_find_failed%& are used when relevant.
18926 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
18927 whether obtained from an MX lookup or not.
18931 .section "How the options are used" "SECThowoptused"
18932 The options are a sequence of words; in practice no more than three are ever
18933 present. One of the words can be the name of a transport; this overrides the
18934 &%transport%& option on the router for this particular routing rule only. The
18935 other words (if present) control randomization of the list of hosts on a
18936 per-rule basis, and how the IP addresses of the hosts are to be found when
18937 routing to a remote transport. These options are as follows:
18940 &%randomize%&: randomize the order of the hosts in this list, overriding the
18941 setting of &%hosts_randomize%& for this routing rule only.
18943 &%no_randomize%&: do not randomize the order of the hosts in this list,
18944 overriding the setting of &%hosts_randomize%& for this routing rule only.
18946 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
18947 find IP addresses. This function may ultimately cause a DNS lookup, but it may
18948 also look in &_/etc/hosts_& or other sources of information.
18950 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
18951 no address records are found. If there is a temporary DNS error (such as a
18952 timeout), delivery is deferred.
18957 route_list = domain1 host1:host2:host3 randomize bydns;\
18958 domain2 host4:host5
18960 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
18961 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
18962 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
18963 or &[gethostbyname()]&, and the result of the lookup is the result of that
18966 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
18967 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
18968 instead of TRY_AGAIN. That is why the default action is to try a DNS
18969 lookup first. Only if that gives a definite &"no such host"& is the local
18974 If no IP address for a host can be found, what happens is controlled by the
18975 &%host_find_failed%& option.
18978 When an address is routed to a local transport, IP addresses are not looked up.
18979 The host list is passed to the transport in the &$host$& variable.
18983 .section "Manualroute examples" "SECID123"
18984 In some of the examples that follow, the presence of the &%remote_smtp%&
18985 transport, as defined in the default configuration file, is assumed:
18988 .cindex "smart host" "example router"
18989 The &(manualroute)& router can be used to forward all external mail to a
18990 &'smart host'&. If you have set up, in the main part of the configuration, a
18991 named domain list that contains your local domains, for example:
18993 domainlist local_domains = my.domain.example
18995 You can arrange for all other domains to be routed to a smart host by making
18996 your first router something like this:
18999 driver = manualroute
19000 domains = !+local_domains
19001 transport = remote_smtp
19002 route_list = * smarthost.ref.example
19004 This causes all non-local addresses to be sent to the single host
19005 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
19006 they are tried in order
19007 (but you can use &%hosts_randomize%& to vary the order each time).
19008 Another way of configuring the same thing is this:
19011 driver = manualroute
19012 transport = remote_smtp
19013 route_list = !+local_domains smarthost.ref.example
19015 There is no difference in behaviour between these two routers as they stand.
19016 However, they behave differently if &%no_more%& is added to them. In the first
19017 example, the router is skipped if the domain does not match the &%domains%&
19018 precondition; the following router is always tried. If the router runs, it
19019 always matches the domain and so can never decline. Therefore, &%no_more%&
19020 would have no effect. In the second case, the router is never skipped; it
19021 always runs. However, if it doesn't match the domain, it declines. In this case
19022 &%no_more%& would prevent subsequent routers from running.
19025 .cindex "mail hub example"
19026 A &'mail hub'& is a host which receives mail for a number of domains via MX
19027 records in the DNS and delivers it via its own private routing mechanism. Often
19028 the final destinations are behind a firewall, with the mail hub being the one
19029 machine that can connect to machines both inside and outside the firewall. The
19030 &(manualroute)& router is usually used on a mail hub to route incoming messages
19031 to the correct hosts. For a small number of domains, the routing can be inline,
19032 using the &%route_list%& option, but for a larger number a file or database
19033 lookup is easier to manage.
19035 If the domain names are in fact the names of the machines to which the mail is
19036 to be sent by the mail hub, the configuration can be quite simple. For
19040 driver = manualroute
19041 transport = remote_smtp
19042 route_list = *.rhodes.tvs.example $domain
19044 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
19045 whose names are the same as the mail domains. A similar approach can be taken
19046 if the host name can be obtained from the domain name by a string manipulation
19047 that the expansion facilities can handle. Otherwise, a lookup based on the
19048 domain can be used to find the host:
19051 driver = manualroute
19052 transport = remote_smtp
19053 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
19055 The result of the lookup must be the name or IP address of the host (or
19056 hosts) to which the address is to be routed. If the lookup fails, the route
19057 data is empty, causing the router to decline. The address then passes to the
19061 .cindex "batched SMTP output example"
19062 .cindex "SMTP" "batched outgoing; example"
19063 You can use &(manualroute)& to deliver messages to pipes or files in batched
19064 SMTP format for onward transportation by some other means. This is one way of
19065 storing mail for a dial-up host when it is not connected. The route list entry
19066 can be as simple as a single domain name in a configuration like this:
19069 driver = manualroute
19070 transport = batchsmtp_appendfile
19071 route_list = saved.domain.example
19073 though often a pattern is used to pick up more than one domain. If there are
19074 several domains or groups of domains with different transport requirements,
19075 different transports can be listed in the routing information:
19078 driver = manualroute
19080 *.saved.domain1.example $domain batch_appendfile; \
19081 *.saved.domain2.example \
19082 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
19085 .vindex "&$domain$&"
19087 The first of these just passes the domain in the &$host$& variable, which
19088 doesn't achieve much (since it is also in &$domain$&), but the second does a
19089 file lookup to find a value to pass, causing the router to decline to handle
19090 the address if the lookup fails.
19093 .cindex "UUCP" "example of router for"
19094 Routing mail directly to UUCP software is a specific case of the use of
19095 &(manualroute)& in a gateway to another mail environment. This is an example of
19096 one way it can be done:
19102 command = /usr/local/bin/uux -r - \
19103 ${substr_-5:$host}!rmail ${local_part}
19104 return_fail_output = true
19109 driver = manualroute
19111 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
19113 The file &_/usr/local/exim/uucphosts_& contains entries like
19115 darksite.ethereal.example: darksite.UUCP
19117 It can be set up more simply without adding and removing &".UUCP"& but this way
19118 makes clear the distinction between the domain name
19119 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
19121 .ecindex IIDmanrou1
19122 .ecindex IIDmanrou2
19131 . ////////////////////////////////////////////////////////////////////////////
19132 . ////////////////////////////////////////////////////////////////////////////
19134 .chapter "The queryprogram router" "CHAPdriverlast"
19135 .scindex IIDquerou1 "&(queryprogram)& router"
19136 .scindex IIDquerou2 "routers" "&(queryprogram)&"
19137 .cindex "routing" "by external program"
19138 The &(queryprogram)& router routes an address by running an external command
19139 and acting on its output. This is an expensive way to route, and is intended
19140 mainly for use in lightly-loaded systems, or for performing experiments.
19141 However, if it is possible to use the precondition options (&%domains%&,
19142 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
19143 be used in special cases, even on a busy host. There are the following private
19145 .cindex "options" "&(queryprogram)& router"
19147 .option command queryprogram string&!! unset
19148 This option must be set. It specifies the command that is to be run. The
19149 command is split up into a command name and arguments, and then each is
19150 expanded separately (exactly as for a &(pipe)& transport, described in chapter
19151 &<<CHAPpipetransport>>&).
19154 .option command_group queryprogram string unset
19155 .cindex "gid (group id)" "in &(queryprogram)& router"
19156 This option specifies a gid to be set when running the command while routing an
19157 address for deliver. It must be set if &%command_user%& specifies a numerical
19158 uid. If it begins with a digit, it is interpreted as the numerical value of the
19159 gid. Otherwise it is looked up using &[getgrnam()]&.
19162 .option command_user queryprogram string unset
19163 .cindex "uid (user id)" "for &(queryprogram)&"
19164 This option must be set. It specifies the uid which is set when running the
19165 command while routing an address for delivery. If the value begins with a digit,
19166 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
19167 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
19168 not set, a value for the gid also.
19170 &*Warning:*& Changing uid and gid is possible only when Exim is running as
19171 root, which it does during a normal delivery in a conventional configuration.
19172 However, when an address is being verified during message reception, Exim is
19173 usually running as the Exim user, not as root. If the &(queryprogram)& router
19174 is called from a non-root process, Exim cannot change uid or gid before running
19175 the command. In this circumstance the command runs under the current uid and
19179 .option current_directory queryprogram string /
19180 This option specifies an absolute path which is made the current directory
19181 before running the command.
19184 .option timeout queryprogram time 1h
19185 If the command does not complete within the timeout period, its process group
19186 is killed and the message is frozen. A value of zero time specifies no
19190 The standard output of the command is connected to a pipe, which is read when
19191 the command terminates. It should consist of a single line of output,
19192 containing up to five fields, separated by white space. The maximum length of
19193 the line is 1023 characters. Longer lines are silently truncated. The first
19194 field is one of the following words (case-insensitive):
19197 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
19200 &'Decline'&: the router declines; pass the address to the next router, unless
19201 &%no_more%& is set.
19203 &'Fail'&: routing failed; do not pass the address to any more routers. Any
19204 subsequent text on the line is an error message. If the router is run as part
19205 of address verification during an incoming SMTP message, the message is
19206 included in the SMTP response.
19208 &'Defer'&: routing could not be completed at this time; try again later. Any
19209 subsequent text on the line is an error message which is logged. It is not
19210 included in any SMTP response.
19212 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
19214 &'Pass'&: pass the address to the next router (or the router specified by
19215 &%pass_router%&), overriding &%no_more%&.
19217 &'Redirect'&: the message is redirected. The remainder of the line is a list of
19218 new addresses, which are routed independently, starting with the first router,
19219 or the router specified by &%redirect_router%&, if set.
19222 When the first word is &'accept'&, the remainder of the line consists of a
19223 number of keyed data values, as follows (split into two lines here, to fit on
19226 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
19227 LOOKUP=byname|bydns DATA=<text>
19229 The data items can be given in any order, and all are optional. If no transport
19230 is included, the transport specified by the generic &%transport%& option is
19231 used. The list of hosts and the lookup type are needed only if the transport is
19232 an &(smtp)& transport that does not itself supply a list of hosts.
19234 The format of the list of hosts is the same as for the &(manualroute)& router.
19235 As well as host names and IP addresses with optional port numbers, as described
19236 in section &<<SECTformatonehostitem>>&, it may contain names followed by
19237 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
19238 (see section &<<SECThostshowused>>&).
19240 If the lookup type is not specified, Exim behaves as follows when trying to
19241 find an IP address for each host: First, a DNS lookup is done. If this yields
19242 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
19243 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
19244 result of the lookup is the result of that call.
19246 .vindex "&$address_data$&"
19247 If the DATA field is set, its value is placed in the &$address_data$&
19248 variable. For example, this return line
19250 accept hosts=x1.y.example:x2.y.example data="rule1"
19252 routes the address to the default transport, passing a list of two hosts. When
19253 the transport runs, the string &"rule1"& is in &$address_data$&.
19254 .ecindex IIDquerou1
19255 .ecindex IIDquerou2
19260 . ////////////////////////////////////////////////////////////////////////////
19261 . ////////////////////////////////////////////////////////////////////////////
19263 .chapter "The redirect router" "CHAPredirect"
19264 .scindex IIDredrou1 "&(redirect)& router"
19265 .scindex IIDredrou2 "routers" "&(redirect)&"
19266 .cindex "alias file" "in a &(redirect)& router"
19267 .cindex "address redirection" "&(redirect)& router"
19268 The &(redirect)& router handles several kinds of address redirection. Its most
19269 common uses are for resolving local part aliases from a central alias file
19270 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
19271 files, but it has many other potential uses. The incoming address can be
19272 redirected in several different ways:
19275 It can be replaced by one or more new addresses which are themselves routed
19278 It can be routed to be delivered to a given file or directory.
19280 It can be routed to be delivered to a specified pipe command.
19282 It can cause an automatic reply to be generated.
19284 It can be forced to fail, optionally with a custom error message.
19286 It can be temporarily deferred, optionally with a custom message.
19288 It can be discarded.
19291 The generic &%transport%& option must not be set for &(redirect)& routers.
19292 However, there are some private options which define transports for delivery to
19293 files and pipes, and for generating autoreplies. See the &%file_transport%&,
19294 &%pipe_transport%& and &%reply_transport%& descriptions below.
19296 If success DSNs have been requested
19297 .cindex "DSN" "success"
19298 .cindex "Delivery Status Notification" "success"
19299 redirection triggers one and the DSN options are not passed any further.
19303 .section "Redirection data" "SECID124"
19304 The router operates by interpreting a text string which it obtains either by
19305 expanding the contents of the &%data%& option, or by reading the entire
19306 contents of a file whose name is given in the &%file%& option. These two
19307 options are mutually exclusive. The first is commonly used for handling system
19308 aliases, in a configuration like this:
19312 data = ${lookup{$local_part}lsearch{/etc/aliases}}
19314 If the lookup fails, the expanded string in this example is empty. When the
19315 expansion of &%data%& results in an empty string, the router declines. A forced
19316 expansion failure also causes the router to decline; other expansion failures
19317 cause delivery to be deferred.
19319 A configuration using &%file%& is commonly used for handling users'
19320 &_.forward_& files, like this:
19325 file = $home/.forward
19328 If the file does not exist, or causes no action to be taken (for example, it is
19329 empty or consists only of comments), the router declines. &*Warning*&: This
19330 is not the case when the file contains syntactically valid items that happen to
19331 yield empty addresses, for example, items containing only RFC 2822 address
19336 .section "Forward files and address verification" "SECID125"
19337 .cindex "address redirection" "while verifying"
19338 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
19339 &_.forward_& files, as in the example above. There are two reasons for this:
19342 When Exim is receiving an incoming SMTP message from a remote host, it is
19343 running under the Exim uid, not as root. Exim is unable to change uid to read
19344 the file as the user, and it may not be able to read it as the Exim user. So in
19345 practice the router may not be able to operate.
19347 However, even when the router can operate, the existence of a &_.forward_& file
19348 is unimportant when verifying an address. What should be checked is whether the
19349 local part is a valid user name or not. Cutting out the redirection processing
19350 saves some resources.
19358 .section "Interpreting redirection data" "SECID126"
19359 .cindex "Sieve filter" "specifying in redirection data"
19360 .cindex "filter" "specifying in redirection data"
19361 The contents of the data string, whether obtained from &%data%& or &%file%&,
19362 can be interpreted in two different ways:
19365 If the &%allow_filter%& option is set true, and the data begins with the text
19366 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
19367 &'filtering'& instructions in the form of an Exim or Sieve filter file,
19368 respectively. Details of the syntax and semantics of filter files are described
19369 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
19370 document is intended for use by end users.
19372 Otherwise, the data must be a comma-separated list of redirection items, as
19373 described in the next section.
19376 When a message is redirected to a file (a &"mail folder"&), the file name given
19377 in a non-filter redirection list must always be an absolute path. A filter may
19378 generate a relative path &-- how this is handled depends on the transport's
19379 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
19380 for the &(appendfile)& transport.
19384 .section "Items in a non-filter redirection list" "SECTitenonfilred"
19385 .cindex "address redirection" "non-filter list items"
19386 When the redirection data is not an Exim or Sieve filter, for example, if it
19387 comes from a conventional alias or forward file, it consists of a list of
19388 addresses, file names, pipe commands, or certain special items (see section
19389 &<<SECTspecitredli>>& below). The special items can be individually enabled or
19390 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
19391 depending on their default values. The items in the list are separated by
19392 commas or newlines.
19393 If a comma is required in an item, the entire item must be enclosed in double
19396 Lines starting with a # character are comments, and are ignored, and # may
19397 also appear following a comma, in which case everything between the # and the
19398 next newline character is ignored.
19400 If an item is entirely enclosed in double quotes, these are removed. Otherwise
19401 double quotes are retained because some forms of mail address require their use
19402 (but never to enclose the entire address). In the following description,
19403 &"item"& refers to what remains after any surrounding double quotes have been
19406 .vindex "&$local_part$&"
19407 &*Warning*&: If you use an Exim expansion to construct a redirection address,
19408 and the expansion contains a reference to &$local_part$&, you should make use
19409 of the &%quote_local_part%& expansion operator, in case the local part contains
19410 special characters. For example, to redirect all mail for the domain
19411 &'obsolete.example'&, retaining the existing local part, you could use this
19414 data = ${quote_local_part:$local_part}@newdomain.example
19418 .section "Redirecting to a local mailbox" "SECTredlocmai"
19419 .cindex "routing" "loops in"
19420 .cindex "loop" "while routing, avoidance of"
19421 .cindex "address redirection" "to local mailbox"
19422 A redirection item may safely be the same as the address currently under
19423 consideration. This does not cause a routing loop, because a router is
19424 automatically skipped if any ancestor of the address that is being processed
19425 is the same as the current address and was processed by the current router.
19426 Such an address is therefore passed to the following routers, so it is handled
19427 as if there were no redirection. When making this loop-avoidance test, the
19428 complete local part, including any prefix or suffix, is used.
19430 .cindex "address redirection" "local part without domain"
19431 Specifying the same local part without a domain is a common usage in personal
19432 filter files when the user wants to have messages delivered to the local
19433 mailbox and also forwarded elsewhere. For example, the user whose login is
19434 &'cleo'& might have a &_.forward_& file containing this:
19436 cleo, cleopatra@egypt.example
19438 .cindex "backslash in alias file"
19439 .cindex "alias file" "backslash in"
19440 For compatibility with other MTAs, such unqualified local parts may be
19441 preceded by &"\"&, but this is not a requirement for loop prevention. However,
19442 it does make a difference if more than one domain is being handled
19445 If an item begins with &"\"& and the rest of the item parses as a valid RFC
19446 2822 address that does not include a domain, the item is qualified using the
19447 domain of the incoming address. In the absence of a leading &"\"&, unqualified
19448 addresses are qualified using the value in &%qualify_recipient%&, but you can
19449 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
19451 Care must be taken if there are alias names for local users.
19452 Consider an MTA handling a single local domain where the system alias file
19457 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
19458 messages in the local mailbox, and also forward copies elsewhere. He creates
19461 Sam.Reman, spqr@reme.elsewhere.example
19463 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
19464 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
19465 second time round, because it has previously routed it,
19466 and the following routers presumably cannot handle the alias. The forward file
19467 should really contain
19469 spqr, spqr@reme.elsewhere.example
19471 but because this is such a common error, the &%check_ancestor%& option (see
19472 below) exists to provide a way to get round it. This is normally set on a
19473 &(redirect)& router that is handling users' &_.forward_& files.
19477 .section "Special items in redirection lists" "SECTspecitredli"
19478 In addition to addresses, the following types of item may appear in redirection
19479 lists (that is, in non-filter redirection data):
19482 .cindex "pipe" "in redirection list"
19483 .cindex "address redirection" "to pipe"
19484 An item is treated as a pipe command if it begins with &"|"& and does not parse
19485 as a valid RFC 2822 address that includes a domain. A transport for running the
19486 command must be specified by the &%pipe_transport%& option.
19487 Normally, either the router or the transport specifies a user and a group under
19488 which to run the delivery. The default is to use the Exim user and group.
19490 Single or double quotes can be used for enclosing the individual arguments of
19491 the pipe command; no interpretation of escapes is done for single quotes. If
19492 the command contains a comma character, it is necessary to put the whole item
19493 in double quotes, for example:
19495 "|/some/command ready,steady,go"
19497 since items in redirection lists are terminated by commas. Do not, however,
19498 quote just the command. An item such as
19500 |"/some/command ready,steady,go"
19502 is interpreted as a pipe with a rather strange command name, and no arguments.
19504 Note that the above example assumes that the text comes from a lookup source
19505 of some sort, so that the quotes are part of the data. If composing a
19506 redirect router with a &%data%& option directly specifying this command, the
19507 quotes will be used by the configuration parser to define the extent of one
19508 string, but will not be passed down into the redirect router itself. There
19509 are two main approaches to get around this: escape quotes to be part of the
19510 data itself, or avoid using this mechanism and instead create a custom
19511 transport with the &%command%& option set and reference that transport from
19512 an &%accept%& router.
19515 .cindex "file" "in redirection list"
19516 .cindex "address redirection" "to file"
19517 An item is interpreted as a path name if it begins with &"/"& and does not
19518 parse as a valid RFC 2822 address that includes a domain. For example,
19520 /home/world/minbari
19522 is treated as a file name, but
19524 /s=molari/o=babylon/@x400gate.way
19526 is treated as an address. For a file name, a transport must be specified using
19527 the &%file_transport%& option. However, if the generated path name ends with a
19528 forward slash character, it is interpreted as a directory name rather than a
19529 file name, and &%directory_transport%& is used instead.
19531 Normally, either the router or the transport specifies a user and a group under
19532 which to run the delivery. The default is to use the Exim user and group.
19534 .cindex "&_/dev/null_&"
19535 However, if a redirection item is the path &_/dev/null_&, delivery to it is
19536 bypassed at a high level, and the log entry shows &"**bypassed**"&
19537 instead of a transport name. In this case the user and group are not used.
19540 .cindex "included address list"
19541 .cindex "address redirection" "included external list"
19542 If an item is of the form
19544 :include:<path name>
19546 a list of further items is taken from the given file and included at that
19547 point. &*Note*&: Such a file can not be a filter file; it is just an
19548 out-of-line addition to the list. The items in the included list are separated
19549 by commas or newlines and are not subject to expansion. If this is the first
19550 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
19551 the alias name. This example is incorrect:
19553 list1 :include:/opt/lists/list1
19555 It must be given as
19557 list1: :include:/opt/lists/list1
19560 .cindex "address redirection" "to black hole"
19561 Sometimes you want to throw away mail to a particular local part. Making the
19562 &%data%& option expand to an empty string does not work, because that causes
19563 the router to decline. Instead, the alias item
19564 .cindex "black hole"
19565 .cindex "abandoning mail"
19566 &':blackhole:'& can be used. It does what its name implies. No delivery is
19567 done, and no error message is generated. This has the same effect as specifying
19568 &_/dev/null_& as a destination, but it can be independently disabled.
19570 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
19571 delivery is done for the original local part, even if other redirection items
19572 are present. If you are generating a multi-item list (for example, by reading a
19573 database) and need the ability to provide a no-op item, you must use
19577 .cindex "delivery" "forcing failure"
19578 .cindex "delivery" "forcing deferral"
19579 .cindex "failing delivery" "forcing"
19580 .cindex "deferred delivery, forcing"
19581 .cindex "customizing" "failure message"
19582 An attempt to deliver a particular address can be deferred or forced to fail by
19583 redirection items of the form
19588 respectively. When a redirection list contains such an item, it applies
19589 to the entire redirection; any other items in the list are ignored. Any
19590 text following &':fail:'& or &':defer:'& is placed in the error text
19591 associated with the failure. For example, an alias file might contain:
19593 X.Employee: :fail: Gone away, no forwarding address
19595 In the case of an address that is being verified from an ACL or as the subject
19597 .cindex "VRFY" "error text, display of"
19598 VRFY command, the text is included in the SMTP error response by
19600 .cindex "EXPN" "error text, display of"
19601 The text is not included in the response to an EXPN command. In non-SMTP cases
19602 the text is included in the error message that Exim generates.
19604 .cindex "SMTP" "error codes"
19605 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
19606 &':fail:'&. However, if the message starts with three digits followed by a
19607 space, optionally followed by an extended code of the form &'n.n.n'&, also
19608 followed by a space, and the very first digit is the same as the default error
19609 code, the code from the message is used instead. If the very first digit is
19610 incorrect, a panic error is logged, and the default code is used. You can
19611 suppress the use of the supplied code in a redirect router by setting the
19612 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
19615 .vindex "&$acl_verify_message$&"
19616 In an ACL, an explicitly provided message overrides the default, but the
19617 default message is available in the variable &$acl_verify_message$& and can
19618 therefore be included in a custom message if this is desired.
19620 Normally the error text is the rest of the redirection list &-- a comma does
19621 not terminate it &-- but a newline does act as a terminator. Newlines are not
19622 normally present in alias expansions. In &(lsearch)& lookups they are removed
19623 as part of the continuation process, but they may exist in other kinds of
19624 lookup and in &':include:'& files.
19626 During routing for message delivery (as opposed to verification), a redirection
19627 containing &':fail:'& causes an immediate failure of the incoming address,
19628 whereas &':defer:'& causes the message to remain on the queue so that a
19629 subsequent delivery attempt can happen at a later time. If an address is
19630 deferred for too long, it will ultimately fail, because the normal retry
19634 .cindex "alias file" "exception to default"
19635 Sometimes it is useful to use a single-key search type with a default (see
19636 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
19637 for exceptions to the default. These can be handled by aliasing them to
19638 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
19639 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
19640 results in an empty redirection list has the same effect.
19644 .section "Duplicate addresses" "SECTdupaddr"
19645 .cindex "duplicate addresses"
19646 .cindex "address duplicate, discarding"
19647 .cindex "pipe" "duplicated"
19648 Exim removes duplicate addresses from the list to which it is delivering, so as
19649 to deliver just one copy to each address. This does not apply to deliveries
19650 routed to pipes by different immediate parent addresses, but an indirect
19651 aliasing scheme of the type
19653 pipe: |/some/command $local_part
19657 does not work with a message that is addressed to both local parts, because
19658 when the second is aliased to the intermediate local part &"pipe"& it gets
19659 discarded as being the same as a previously handled address. However, a scheme
19662 localpart1: |/some/command $local_part
19663 localpart2: |/some/command $local_part
19665 does result in two different pipe deliveries, because the immediate parents of
19666 the pipes are distinct.
19670 .section "Repeated redirection expansion" "SECID128"
19671 .cindex "repeated redirection expansion"
19672 .cindex "address redirection" "repeated for each delivery attempt"
19673 When a message cannot be delivered to all of its recipients immediately,
19674 leading to two or more delivery attempts, redirection expansion is carried out
19675 afresh each time for those addresses whose children were not all previously
19676 delivered. If redirection is being used as a mailing list, this can lead to new
19677 members of the list receiving copies of old messages. The &%one_time%& option
19678 can be used to avoid this.
19681 .section "Errors in redirection lists" "SECID129"
19682 .cindex "address redirection" "errors"
19683 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
19684 error is skipped, and an entry is written to the main log. This may be useful
19685 for mailing lists that are automatically managed. Otherwise, if an error is
19686 detected while generating the list of new addresses, the original address is
19687 deferred. See also &%syntax_errors_to%&.
19691 .section "Private options for the redirect router" "SECID130"
19693 .cindex "options" "&(redirect)& router"
19694 The private options for the &(redirect)& router are as follows:
19697 .option allow_defer redirect boolean false
19698 Setting this option allows the use of &':defer:'& in non-filter redirection
19699 data, or the &%defer%& command in an Exim filter file.
19702 .option allow_fail redirect boolean false
19703 .cindex "failing delivery" "from filter"
19704 If this option is true, the &':fail:'& item can be used in a redirection list,
19705 and the &%fail%& command may be used in an Exim filter file.
19708 .option allow_filter redirect boolean false
19709 .cindex "filter" "enabling use of"
19710 .cindex "Sieve filter" "enabling use of"
19711 Setting this option allows Exim to interpret redirection data that starts with
19712 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
19713 are some features of Exim filter files that some administrators may wish to
19714 lock out; see the &%forbid_filter_%&&'xxx'& options below.
19716 It is also possible to lock out Exim filters or Sieve filters while allowing
19717 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
19720 The filter is run using the uid and gid set by the generic &%user%& and
19721 &%group%& options. These take their defaults from the password data if
19722 &%check_local_user%& is set, so in the normal case of users' personal filter
19723 files, the filter is run as the relevant user. When &%allow_filter%& is set
19724 true, Exim insists that either &%check_local_user%& or &%user%& is set.
19728 .option allow_freeze redirect boolean false
19729 .cindex "freezing messages" "allowing in filter"
19730 Setting this option allows the use of the &%freeze%& command in an Exim filter.
19731 This command is more normally encountered in system filters, and is disabled by
19732 default for redirection filters because it isn't something you usually want to
19733 let ordinary users do.
19737 .option check_ancestor redirect boolean false
19738 This option is concerned with handling generated addresses that are the same
19739 as some address in the list of redirection ancestors of the current address.
19740 Although it is turned off by default in the code, it is set in the default
19741 configuration file for handling users' &_.forward_& files. It is recommended
19742 for this use of the &(redirect)& router.
19744 When &%check_ancestor%& is set, if a generated address (including the domain)
19745 is the same as any ancestor of the current address, it is replaced by a copy of
19746 the current address. This helps in the case where local part A is aliased to B,
19747 and B has a &_.forward_& file pointing back to A. For example, within a single
19748 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
19749 &_&~jb/.forward_& contains:
19751 \Joe.Bloggs, <other item(s)>
19753 Without the &%check_ancestor%& setting, either local part (&"jb"& or
19754 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
19755 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
19756 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
19757 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
19758 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
19759 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
19760 original address. See also the &%repeat_use%& option below.
19763 .option check_group redirect boolean "see below"
19764 When the &%file%& option is used, the group owner of the file is checked only
19765 when this option is set. The permitted groups are those listed in the
19766 &%owngroups%& option, together with the user's default group if
19767 &%check_local_user%& is set. If the file has the wrong group, routing is
19768 deferred. The default setting for this option is true if &%check_local_user%&
19769 is set and the &%modemask%& option permits the group write bit, or if the
19770 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
19774 .option check_owner redirect boolean "see below"
19775 When the &%file%& option is used, the owner of the file is checked only when
19776 this option is set. If &%check_local_user%& is set, the local user is
19777 permitted; otherwise the owner must be one of those listed in the &%owners%&
19778 option. The default value for this option is true if &%check_local_user%& or
19779 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
19782 .option data redirect string&!! unset
19783 This option is mutually exclusive with &%file%&. One or other of them must be
19784 set, but not both. The contents of &%data%& are expanded, and then used as the
19785 list of forwarding items, or as a set of filtering instructions. If the
19786 expansion is forced to fail, or the result is an empty string or a string that
19787 has no effect (consists entirely of comments), the router declines.
19789 When filtering instructions are used, the string must begin with &"#Exim
19790 filter"&, and all comments in the string, including this initial one, must be
19791 terminated with newline characters. For example:
19793 data = #Exim filter\n\
19794 if $h_to: contains Exim then save $home/mail/exim endif
19796 If you are reading the data from a database where newlines cannot be included,
19797 you can use the &${sg}$& expansion item to turn the escape string of your
19798 choice into a newline.
19801 .option directory_transport redirect string&!! unset
19802 A &(redirect)& router sets up a direct delivery to a directory when a path name
19803 ending with a slash is specified as a new &"address"&. The transport used is
19804 specified by this option, which, after expansion, must be the name of a
19805 configured transport. This should normally be an &(appendfile)& transport.
19808 .option file redirect string&!! unset
19809 This option specifies the name of a file that contains the redirection data. It
19810 is mutually exclusive with the &%data%& option. The string is expanded before
19811 use; if the expansion is forced to fail, the router declines. Other expansion
19812 failures cause delivery to be deferred. The result of a successful expansion
19813 must be an absolute path. The entire file is read and used as the redirection
19814 data. If the data is an empty string or a string that has no effect (consists
19815 entirely of comments), the router declines.
19817 .cindex "NFS" "checking for file existence"
19818 If the attempt to open the file fails with a &"does not exist"& error, Exim
19819 runs a check on the containing directory,
19820 unless &%ignore_enotdir%& is true (see below).
19821 If the directory does not appear to exist, delivery is deferred. This can
19822 happen when users' &_.forward_& files are in NFS-mounted directories, and there
19823 is a mount problem. If the containing directory does exist, but the file does
19824 not, the router declines.
19827 .option file_transport redirect string&!! unset
19828 .vindex "&$address_file$&"
19829 A &(redirect)& router sets up a direct delivery to a file when a path name not
19830 ending in a slash is specified as a new &"address"&. The transport used is
19831 specified by this option, which, after expansion, must be the name of a
19832 configured transport. This should normally be an &(appendfile)& transport. When
19833 it is running, the file name is in &$address_file$&.
19836 .option filter_prepend_home redirect boolean true
19837 When this option is true, if a &(save)& command in an Exim filter specifies a
19838 relative path, and &$home$& is defined, it is automatically prepended to the
19839 relative path. If this option is set false, this action does not happen. The
19840 relative path is then passed to the transport unmodified.
19843 .option forbid_blackhole redirect boolean false
19844 If this option is true, the &':blackhole:'& item may not appear in a
19848 .option forbid_exim_filter redirect boolean false
19849 If this option is set true, only Sieve filters are permitted when
19850 &%allow_filter%& is true.
19855 .option forbid_file redirect boolean false
19856 .cindex "delivery" "to file; forbidding"
19857 .cindex "Sieve filter" "forbidding delivery to a file"
19858 .cindex "Sieve filter" "&""keep""& facility; disabling"
19859 If this option is true, this router may not generate a new address that
19860 specifies delivery to a local file or directory, either from a filter or from a
19861 conventional forward file. This option is forced to be true if &%one_time%& is
19862 set. It applies to Sieve filters as well as to Exim filters, but if true, it
19863 locks out the Sieve's &"keep"& facility.
19866 .option forbid_filter_dlfunc redirect boolean false
19867 .cindex "filter" "locking out certain features"
19868 If this option is true, string expansions in Exim filters are not allowed to
19869 make use of the &%dlfunc%& expansion facility to run dynamically loaded
19872 .option forbid_filter_existstest redirect boolean false
19873 .cindex "expansion" "statting a file"
19874 If this option is true, string expansions in Exim filters are not allowed to
19875 make use of the &%exists%& condition or the &%stat%& expansion item.
19877 .option forbid_filter_logwrite redirect boolean false
19878 If this option is true, use of the logging facility in Exim filters is not
19879 permitted. Logging is in any case available only if the filter is being run
19880 under some unprivileged uid (which is normally the case for ordinary users'
19881 &_.forward_& files).
19884 .option forbid_filter_lookup redirect boolean false
19885 If this option is true, string expansions in Exim filter files are not allowed
19886 to make use of &%lookup%& items.
19889 .option forbid_filter_perl redirect boolean false
19890 This option has an effect only if Exim is built with embedded Perl support. If
19891 it is true, string expansions in Exim filter files are not allowed to make use
19892 of the embedded Perl support.
19895 .option forbid_filter_readfile redirect boolean false
19896 If this option is true, string expansions in Exim filter files are not allowed
19897 to make use of &%readfile%& items.
19900 .option forbid_filter_readsocket redirect boolean false
19901 If this option is true, string expansions in Exim filter files are not allowed
19902 to make use of &%readsocket%& items.
19905 .option forbid_filter_reply redirect boolean false
19906 If this option is true, this router may not generate an automatic reply
19907 message. Automatic replies can be generated only from Exim or Sieve filter
19908 files, not from traditional forward files. This option is forced to be true if
19909 &%one_time%& is set.
19912 .option forbid_filter_run redirect boolean false
19913 If this option is true, string expansions in Exim filter files are not allowed
19914 to make use of &%run%& items.
19917 .option forbid_include redirect boolean false
19918 If this option is true, items of the form
19920 :include:<path name>
19922 are not permitted in non-filter redirection lists.
19925 .option forbid_pipe redirect boolean false
19926 .cindex "delivery" "to pipe; forbidding"
19927 If this option is true, this router may not generate a new address which
19928 specifies delivery to a pipe, either from an Exim filter or from a conventional
19929 forward file. This option is forced to be true if &%one_time%& is set.
19932 .option forbid_sieve_filter redirect boolean false
19933 If this option is set true, only Exim filters are permitted when
19934 &%allow_filter%& is true.
19937 .cindex "SMTP" "error codes"
19938 .option forbid_smtp_code redirect boolean false
19939 If this option is set true, any SMTP error codes that are present at the start
19940 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
19941 the default codes (451 and 550, respectively) are always used.
19946 .option hide_child_in_errmsg redirect boolean false
19947 .cindex "bounce message" "redirection details; suppressing"
19948 If this option is true, it prevents Exim from quoting a child address if it
19949 generates a bounce or delay message for it. Instead it says &"an address
19950 generated from <&'the top level address'&>"&. Of course, this applies only to
19951 bounces generated locally. If a message is forwarded to another host, &'its'&
19952 bounce may well quote the generated address.
19955 .option ignore_eacces redirect boolean false
19957 If this option is set and an attempt to open a redirection file yields the
19958 EACCES error (permission denied), the &(redirect)& router behaves as if the
19959 file did not exist.
19962 .option ignore_enotdir redirect boolean false
19964 If this option is set and an attempt to open a redirection file yields the
19965 ENOTDIR error (something on the path is not a directory), the &(redirect)&
19966 router behaves as if the file did not exist.
19968 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
19969 router that has the &%file%& option set discovers that the file does not exist
19970 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
19971 against unmounted NFS directories. If the parent can not be statted, delivery
19972 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
19973 is set, because that option tells Exim to ignore &"something on the path is not
19974 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
19975 that some operating systems give ENOENT where others give ENOTDIR.
19979 .option include_directory redirect string unset
19980 If this option is set, the path names of any &':include:'& items in a
19981 redirection list must start with this directory.
19984 .option modemask redirect "octal integer" 022
19985 This specifies mode bits which must not be set for a file specified by the
19986 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
19989 .option one_time redirect boolean false
19990 .cindex "one-time aliasing/forwarding expansion"
19991 .cindex "alias file" "one-time expansion"
19992 .cindex "forward file" "one-time expansion"
19993 .cindex "mailing lists" "one-time expansion"
19994 .cindex "address redirection" "one-time expansion"
19995 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
19996 files each time it tries to deliver a message causes a problem when one or more
19997 of the generated addresses fails be delivered at the first attempt. The problem
19998 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
19999 but of what happens when the redirection list changes during the time that the
20000 message is on Exim's queue. This is particularly true in the case of mailing
20001 lists, where new subscribers might receive copies of messages that were posted
20002 before they subscribed.
20004 If &%one_time%& is set and any addresses generated by the router fail to
20005 deliver at the first attempt, the failing addresses are added to the message as
20006 &"top level"& addresses, and the parent address that generated them is marked
20007 &"delivered"&. Thus, redirection does not happen again at the next delivery
20010 &*Warning 1*&: Any header line addition or removal that is specified by this
20011 router would be lost if delivery did not succeed at the first attempt. For this
20012 reason, the &%headers_add%& and &%headers_remove%& generic options are not
20013 permitted when &%one_time%& is set.
20015 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
20016 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
20017 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
20019 &*Warning 3*&: The &%unseen%& generic router option may not be set with
20022 The original top-level address is remembered with each of the generated
20023 addresses, and is output in any log messages. However, any intermediate parent
20024 addresses are not recorded. This makes a difference to the log only if
20025 &%all_parents%& log selector is set. It is expected that &%one_time%& will
20026 typically be used for mailing lists, where there is normally just one level of
20030 .option owners redirect "string list" unset
20031 .cindex "ownership" "alias file"
20032 .cindex "ownership" "forward file"
20033 .cindex "alias file" "ownership"
20034 .cindex "forward file" "ownership"
20035 This specifies a list of permitted owners for the file specified by &%file%&.
20036 This list is in addition to the local user when &%check_local_user%& is set.
20037 See &%check_owner%& above.
20040 .option owngroups redirect "string list" unset
20041 This specifies a list of permitted groups for the file specified by &%file%&.
20042 The list is in addition to the local user's primary group when
20043 &%check_local_user%& is set. See &%check_group%& above.
20046 .option pipe_transport redirect string&!! unset
20047 .vindex "&$address_pipe$&"
20048 A &(redirect)& router sets up a direct delivery to a pipe when a string
20049 starting with a vertical bar character is specified as a new &"address"&. The
20050 transport used is specified by this option, which, after expansion, must be the
20051 name of a configured transport. This should normally be a &(pipe)& transport.
20052 When the transport is run, the pipe command is in &$address_pipe$&.
20055 .option qualify_domain redirect string&!! unset
20056 .vindex "&$qualify_recipient$&"
20057 If this option is set, and an unqualified address (one without a domain) is
20058 generated, and that address would normally be qualified by the global setting
20059 in &%qualify_recipient%&, it is instead qualified with the domain specified by
20060 expanding this string. If the expansion fails, the router declines. If you want
20061 to revert to the default, you can have the expansion generate
20062 &$qualify_recipient$&.
20064 This option applies to all unqualified addresses generated by Exim filters,
20065 but for traditional &_.forward_& files, it applies only to addresses that are
20066 not preceded by a backslash. Sieve filters cannot generate unqualified
20069 .option qualify_preserve_domain redirect boolean false
20070 .cindex "domain" "in redirection; preserving"
20071 .cindex "preserving domain in redirection"
20072 .cindex "address redirection" "domain; preserving"
20073 If this option is set, the router's local &%qualify_domain%& option must not be
20074 set (a configuration error occurs if it is). If an unqualified address (one
20075 without a domain) is generated, it is qualified with the domain of the parent
20076 address (the immediately preceding ancestor) instead of the global
20077 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
20078 this applies whether or not the address is preceded by a backslash.
20081 .option repeat_use redirect boolean true
20082 If this option is set false, the router is skipped for a child address that has
20083 any ancestor that was routed by this router. This test happens before any of
20084 the other preconditions are tested. Exim's default anti-looping rules skip
20085 only when the ancestor is the same as the current address. See also
20086 &%check_ancestor%& above and the generic &%redirect_router%& option.
20089 .option reply_transport redirect string&!! unset
20090 A &(redirect)& router sets up an automatic reply when a &%mail%& or
20091 &%vacation%& command is used in a filter file. The transport used is specified
20092 by this option, which, after expansion, must be the name of a configured
20093 transport. This should normally be an &(autoreply)& transport. Other transports
20094 are unlikely to do anything sensible or useful.
20097 .option rewrite redirect boolean true
20098 .cindex "address redirection" "disabling rewriting"
20099 If this option is set false, addresses generated by the router are not
20100 subject to address rewriting. Otherwise, they are treated like new addresses
20101 and are rewritten according to the global rewriting rules.
20104 .option sieve_subaddress redirect string&!! unset
20105 The value of this option is passed to a Sieve filter to specify the
20106 :subaddress part of an address.
20108 .option sieve_useraddress redirect string&!! unset
20109 The value of this option is passed to a Sieve filter to specify the :user part
20110 of an address. However, if it is unset, the entire original local part
20111 (including any prefix or suffix) is used for :user.
20114 .option sieve_vacation_directory redirect string&!! unset
20115 .cindex "Sieve filter" "vacation directory"
20116 To enable the &"vacation"& extension for Sieve filters, you must set
20117 &%sieve_vacation_directory%& to the directory where vacation databases are held
20118 (do not put anything else in that directory), and ensure that the
20119 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
20120 needs their own directory; Exim will create it if necessary.
20124 .option skip_syntax_errors redirect boolean false
20125 .cindex "forward file" "broken"
20126 .cindex "address redirection" "broken files"
20127 .cindex "alias file" "broken"
20128 .cindex "broken alias or forward files"
20129 .cindex "ignoring faulty addresses"
20130 .cindex "skipping faulty addresses"
20131 .cindex "error" "skipping bad syntax"
20132 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
20133 non-filter redirection data are skipped, and each failing address is logged. If
20134 &%syntax_errors_to%& is set, a message is sent to the address it defines,
20135 giving details of the failures. If &%syntax_errors_text%& is set, its contents
20136 are expanded and placed at the head of the error message generated by
20137 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
20138 be the same address as the generic &%errors_to%& option. The
20139 &%skip_syntax_errors%& option is often used when handling mailing lists.
20141 If all the addresses in a redirection list are skipped because of syntax
20142 errors, the router declines to handle the original address, and it is passed to
20143 the following routers.
20145 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
20146 error in the filter causes filtering to be abandoned without any action being
20147 taken. The incident is logged, and the router declines to handle the address,
20148 so it is passed to the following routers.
20150 .cindex "Sieve filter" "syntax errors in"
20151 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
20152 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
20153 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
20155 &%skip_syntax_errors%& can be used to specify that errors in users' forward
20156 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
20157 option, used with an address that does not get redirected, can be used to
20158 notify users of these errors, by means of a router like this:
20164 file = $home/.forward
20165 file_transport = address_file
20166 pipe_transport = address_pipe
20167 reply_transport = address_reply
20170 syntax_errors_to = real-$local_part@$domain
20171 syntax_errors_text = \
20172 This is an automatically generated message. An error has\n\
20173 been found in your .forward file. Details of the error are\n\
20174 reported below. While this error persists, you will receive\n\
20175 a copy of this message for every message that is addressed\n\
20176 to you. If your .forward file is a filter file, or if it is\n\
20177 a non-filter file containing no valid forwarding addresses,\n\
20178 a copy of each incoming message will be put in your normal\n\
20179 mailbox. If a non-filter file contains at least one valid\n\
20180 forwarding address, forwarding to the valid addresses will\n\
20181 happen, and those will be the only deliveries that occur.
20183 You also need a router to ensure that local addresses that are prefixed by
20184 &`real-`& are recognized, but not forwarded or filtered. For example, you could
20185 put this immediately before the &(userforward)& router:
20190 local_part_prefix = real-
20191 transport = local_delivery
20193 For security, it would probably be a good idea to restrict the use of this
20194 router to locally-generated messages, using a condition such as this:
20196 condition = ${if match {$sender_host_address}\
20197 {\N^(|127\.0\.0\.1)$\N}}
20201 .option syntax_errors_text redirect string&!! unset
20202 See &%skip_syntax_errors%& above.
20205 .option syntax_errors_to redirect string unset
20206 See &%skip_syntax_errors%& above.
20207 .ecindex IIDredrou1
20208 .ecindex IIDredrou2
20215 . ////////////////////////////////////////////////////////////////////////////
20216 . ////////////////////////////////////////////////////////////////////////////
20218 .chapter "Environment for running local transports" "CHAPenvironment" &&&
20219 "Environment for local transports"
20220 .scindex IIDenvlotra1 "local transports" "environment for"
20221 .scindex IIDenvlotra2 "environment for local transports"
20222 .scindex IIDenvlotra3 "transport" "local; environment for"
20223 Local transports handle deliveries to files and pipes. (The &(autoreply)&
20224 transport can be thought of as similar to a pipe.) Exim always runs transports
20225 in subprocesses, under specified uids and gids. Typical deliveries to local
20226 mailboxes run under the uid and gid of the local user.
20228 Exim also sets a specific current directory while running the transport; for
20229 some transports a home directory setting is also relevant. The &(pipe)&
20230 transport is the only one that sets up environment variables; see section
20231 &<<SECTpipeenv>>& for details.
20233 The values used for the uid, gid, and the directories may come from several
20234 different places. In many cases, the router that handles the address associates
20235 settings with that address as a result of its &%check_local_user%&, &%group%&,
20236 or &%user%& options. However, values may also be given in the transport's own
20237 configuration, and these override anything that comes from the router.
20241 .section "Concurrent deliveries" "SECID131"
20242 .cindex "concurrent deliveries"
20243 .cindex "simultaneous deliveries"
20244 If two different messages for the same local recipient arrive more or less
20245 simultaneously, the two delivery processes are likely to run concurrently. When
20246 the &(appendfile)& transport is used to write to a file, Exim applies locking
20247 rules to stop concurrent processes from writing to the same file at the same
20250 However, when you use a &(pipe)& transport, it is up to you to arrange any
20251 locking that is needed. Here is a silly example:
20255 command = /bin/sh -c 'cat >>/some/file'
20257 This is supposed to write the message at the end of the file. However, if two
20258 messages arrive at the same time, the file will be scrambled. You can use the
20259 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
20260 file using the same algorithm that Exim itself uses.
20265 .section "Uids and gids" "SECTenvuidgid"
20266 .cindex "local transports" "uid and gid"
20267 .cindex "transport" "local; uid and gid"
20268 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
20269 overrides any group that the router set in the address, even if &%user%& is not
20270 set for the transport. This makes it possible, for example, to run local mail
20271 delivery under the uid of the recipient (set by the router), but in a special
20272 group (set by the transport). For example:
20275 # User/group are set by check_local_user in this router
20279 transport = group_delivery
20282 # This transport overrides the group
20284 driver = appendfile
20285 file = /var/spool/mail/$local_part
20288 If &%user%& is set for a transport, its value overrides what is set in the
20289 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
20290 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
20293 .oindex "&%initgroups%&"
20294 When the uid is taken from the transport's configuration, the &[initgroups()]&
20295 function is called for the groups associated with that uid if the
20296 &%initgroups%& option is set for the transport. When the uid is not specified
20297 by the transport, but is associated with the address by a router, the option
20298 for calling &[initgroups()]& is taken from the router configuration.
20300 .cindex "&(pipe)& transport" "uid for"
20301 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
20302 is set and &%user%& is not set, the uid of the process that called Exim to
20303 receive the message is used, and if &%group%& is not set, the corresponding
20304 original gid is also used.
20306 This is the detailed preference order for obtaining a gid; the first of the
20307 following that is set is used:
20310 A &%group%& setting of the transport;
20312 A &%group%& setting of the router;
20314 A gid associated with a user setting of the router, either as a result of
20315 &%check_local_user%& or an explicit non-numeric &%user%& setting;
20317 The group associated with a non-numeric &%user%& setting of the transport;
20319 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
20320 the uid is the creator's uid;
20322 The Exim gid if the Exim uid is being used as a default.
20325 If, for example, the user is specified numerically on the router and there are
20326 no group settings, no gid is available. In this situation, an error occurs.
20327 This is different for the uid, for which there always is an ultimate default.
20328 The first of the following that is set is used:
20331 A &%user%& setting of the transport;
20333 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
20335 A &%user%& setting of the router;
20337 A &%check_local_user%& setting of the router;
20342 Of course, an error will still occur if the uid that is chosen is on the
20343 &%never_users%& list.
20349 .section "Current and home directories" "SECID132"
20350 .cindex "current directory for local transport"
20351 .cindex "home directory" "for local transport"
20352 .cindex "transport" "local; home directory for"
20353 .cindex "transport" "local; current directory for"
20354 Routers may set current and home directories for local transports by means of
20355 the &%transport_current_directory%& and &%transport_home_directory%& options.
20356 However, if the transport's &%current_directory%& or &%home_directory%& options
20357 are set, they override the router's values. In detail, the home directory
20358 for a local transport is taken from the first of these values that is set:
20361 The &%home_directory%& option on the transport;
20363 The &%transport_home_directory%& option on the router;
20365 The password data if &%check_local_user%& is set on the router;
20367 The &%router_home_directory%& option on the router.
20370 The current directory is taken from the first of these values that is set:
20373 The &%current_directory%& option on the transport;
20375 The &%transport_current_directory%& option on the router.
20379 If neither the router nor the transport sets a current directory, Exim uses the
20380 value of the home directory, if it is set. Otherwise it sets the current
20381 directory to &_/_& before running a local transport.
20385 .section "Expansion variables derived from the address" "SECID133"
20386 .vindex "&$domain$&"
20387 .vindex "&$local_part$&"
20388 .vindex "&$original_domain$&"
20389 Normally a local delivery is handling a single address, and in that case the
20390 variables such as &$domain$& and &$local_part$& are set during local
20391 deliveries. However, in some circumstances more than one address may be handled
20392 at once (for example, while writing batch SMTP for onward transmission by some
20393 other means). In this case, the variables associated with the local part are
20394 never set, &$domain$& is set only if all the addresses have the same domain,
20395 and &$original_domain$& is never set.
20396 .ecindex IIDenvlotra1
20397 .ecindex IIDenvlotra2
20398 .ecindex IIDenvlotra3
20406 . ////////////////////////////////////////////////////////////////////////////
20407 . ////////////////////////////////////////////////////////////////////////////
20409 .chapter "Generic options for transports" "CHAPtransportgeneric"
20410 .scindex IIDgenoptra1 "generic options" "transport"
20411 .scindex IIDgenoptra2 "options" "generic; for transports"
20412 .scindex IIDgenoptra3 "transport" "generic options for"
20413 The following generic options apply to all transports:
20416 .option body_only transports boolean false
20417 .cindex "transport" "body only"
20418 .cindex "message" "transporting body only"
20419 .cindex "body of message" "transporting"
20420 If this option is set, the message's headers are not transported. It is
20421 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
20422 or &(pipe)& transports, the settings of &%message_prefix%& and
20423 &%message_suffix%& should be checked, because this option does not
20424 automatically suppress them.
20427 .option current_directory transports string&!! unset
20428 .cindex "transport" "current directory for"
20429 This specifies the current directory that is to be set while running the
20430 transport, overriding any value that may have been set by the router.
20431 If the expansion fails for any reason, including forced failure, an error is
20432 logged, and delivery is deferred.
20435 .option disable_logging transports boolean false
20436 If this option is set true, nothing is logged for any
20437 deliveries by the transport or for any
20438 transport errors. You should not set this option unless you really, really know
20439 what you are doing.
20442 .option debug_print transports string&!! unset
20443 .cindex "testing" "variables in drivers"
20444 If this option is set and debugging is enabled (see the &%-d%& command line
20445 option), the string is expanded and included in the debugging output when the
20447 If expansion of the string fails, the error message is written to the debugging
20448 output, and Exim carries on processing.
20449 This facility is provided to help with checking out the values of variables and
20450 so on when debugging driver configurations. For example, if a &%headers_add%&
20451 option is not working properly, &%debug_print%& could be used to output the
20452 variables it references. A newline is added to the text if it does not end with
20454 The variables &$transport_name$& and &$router_name$& contain the name of the
20455 transport and the router that called it.
20457 .option delivery_date_add transports boolean false
20458 .cindex "&'Delivery-date:'& header line"
20459 If this option is true, a &'Delivery-date:'& header is added to the message.
20460 This gives the actual time the delivery was made. As this is not a standard
20461 header, Exim has a configuration option (&%delivery_date_remove%&) which
20462 requests its removal from incoming messages, so that delivered messages can
20463 safely be resent to other recipients.
20466 .option driver transports string unset
20467 This specifies which of the available transport drivers is to be used.
20468 There is no default, and this option must be set for every transport.
20471 .option envelope_to_add transports boolean false
20472 .cindex "&'Envelope-to:'& header line"
20473 If this option is true, an &'Envelope-to:'& header is added to the message.
20474 This gives the original address(es) in the incoming envelope that caused this
20475 delivery to happen. More than one address may be present if the transport is
20476 configured to handle several addresses at once, or if more than one original
20477 address was redirected to the same final address. As this is not a standard
20478 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
20479 its removal from incoming messages, so that delivered messages can safely be
20480 resent to other recipients.
20483 .option group transports string&!! "Exim group"
20484 .cindex "transport" "group; specifying"
20485 This option specifies a gid for running the transport process, overriding any
20486 value that the router supplies, and also overriding any value associated with
20487 &%user%& (see below).
20490 .option headers_add transports list&!! unset
20491 .cindex "header lines" "adding in transport"
20492 .cindex "transport" "header lines; adding"
20493 This option specifies a list of text headers,
20494 newline-separated (by default, changeable in the usual way),
20495 which are (separately) expanded and added to the header
20496 portion of a message as it is transported, as described in section
20497 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
20498 routers. If the result of the expansion is an empty string, or if the expansion
20499 is forced to fail, no action is taken. Other expansion failures are treated as
20500 errors and cause the delivery to be deferred.
20502 Unlike most options, &%headers_add%& can be specified multiple times
20503 for a transport; all listed headers are added.
20506 .option headers_only transports boolean false
20507 .cindex "transport" "header lines only"
20508 .cindex "message" "transporting headers only"
20509 .cindex "header lines" "transporting"
20510 If this option is set, the message's body is not transported. It is mutually
20511 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
20512 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
20513 checked, since this option does not automatically suppress them.
20516 .option headers_remove transports list&!! unset
20517 .cindex "header lines" "removing"
20518 .cindex "transport" "header lines; removing"
20519 This option specifies a list of header names,
20520 colon-separated (by default, changeable in the usual way);
20521 these headers are omitted from the message as it is transported, as described
20522 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
20524 Each list item is separately expanded.
20525 If the result of the expansion is an empty string, or if the expansion
20526 is forced to fail, no action is taken. Other expansion failures are treated as
20527 errors and cause the delivery to be deferred.
20529 Unlike most options, &%headers_remove%& can be specified multiple times
20530 for a router; all listed headers are removed.
20532 &*Warning*&: Because of the separate expansion of the list items,
20533 items that contain a list separator must have it doubled.
20534 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
20538 .option headers_rewrite transports string unset
20539 .cindex "transport" "header lines; rewriting"
20540 .cindex "rewriting" "at transport time"
20541 This option allows addresses in header lines to be rewritten at transport time,
20542 that is, as the message is being copied to its destination. The contents of the
20543 option are a colon-separated list of rewriting rules. Each rule is in exactly
20544 the same form as one of the general rewriting rules that are applied when a
20545 message is received. These are described in chapter &<<CHAPrewrite>>&. For
20548 headers_rewrite = a@b c@d f : \
20551 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
20552 &'w@z'& in all address-bearing header lines. The rules are applied to the
20553 header lines just before they are written out at transport time, so they affect
20554 only those copies of the message that pass through the transport. However, only
20555 the message's original header lines, and any that were added by a system
20556 filter, are rewritten. If a router or transport adds header lines, they are not
20557 affected by this option. These rewriting rules are &'not'& applied to the
20558 envelope. You can change the return path using &%return_path%&, but you cannot
20559 change envelope recipients at this time.
20562 .option home_directory transports string&!! unset
20563 .cindex "transport" "home directory for"
20565 This option specifies a home directory setting for a local transport,
20566 overriding any value that may be set by the router. The home directory is
20567 placed in &$home$& while expanding the transport's private options. It is also
20568 used as the current directory if no current directory is set by the
20569 &%current_directory%& option on the transport or the
20570 &%transport_current_directory%& option on the router. If the expansion fails
20571 for any reason, including forced failure, an error is logged, and delivery is
20575 .option initgroups transports boolean false
20576 .cindex "additional groups"
20577 .cindex "groups" "additional"
20578 .cindex "transport" "group; additional"
20579 If this option is true and the uid for the delivery process is provided by the
20580 transport, the &[initgroups()]& function is called when running the transport
20581 to ensure that any additional groups associated with the uid are set up.
20585 .option max_parallel transports integer&!! unset
20586 .cindex limit "transport parallelism"
20587 .cindex transport "parallel processes"
20588 .cindex transport "concurrency limit"
20589 .cindex "delivery" "parallelism for transport"
20590 If this option is set and expands to an integer greater than zero
20591 it limits the number of concurrent runs of the transport.
20592 The control does not apply to shadow transports.
20594 .cindex "hints database" "transport concurrency control"
20595 Exim implements this control by means of a hints database in which a record is
20596 incremented whenever a transport process is beaing created. The record
20597 is decremented and possibly removed when the process terminates.
20598 Obviously there is scope for
20599 records to get left lying around if there is a system or program crash. To
20600 guard against this, Exim ignores any records that are more than six hours old.
20602 If you use this option, you should also arrange to delete the
20603 relevant hints database whenever your system reboots. The names of the files
20604 start with &_misc_& and they are kept in the &_spool/db_& directory. There
20605 may be one or two files, depending on the type of DBM in use. The same files
20606 are used for ETRN and smtp transport serialization.
20610 .option message_size_limit transports string&!! 0
20611 .cindex "limit" "message size per transport"
20612 .cindex "size" "of message, limit"
20613 .cindex "transport" "message size; limiting"
20614 This option controls the size of messages passed through the transport. It is
20615 expanded before use; the result of the expansion must be a sequence of decimal
20616 digits, optionally followed by K or M. If the expansion fails for any reason,
20617 including forced failure, or if the result is not of the required form,
20618 delivery is deferred. If the value is greater than zero and the size of a
20619 message exceeds this limit, the address is failed. If there is any chance that
20620 the resulting bounce message could be routed to the same transport, you should
20621 ensure that &%return_size_limit%& is less than the transport's
20622 &%message_size_limit%&, as otherwise the bounce message will fail to get
20627 .option rcpt_include_affixes transports boolean false
20628 .cindex "prefix" "for local part, including in envelope"
20629 .cindex "suffix for local part" "including in envelope"
20630 .cindex "local part" "prefix"
20631 .cindex "local part" "suffix"
20632 When this option is false (the default), and an address that has had any
20633 affixes (prefixes or suffixes) removed from the local part is delivered by any
20634 form of SMTP or LMTP, the affixes are not included. For example, if a router
20637 local_part_prefix = *-
20639 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
20642 RCPT TO:<xyz@some.domain>
20644 This is also the case when an ACL-time callout is being used to verify a
20645 recipient address. However, if &%rcpt_include_affixes%& is set true, the
20646 whole local part is included in the RCPT command. This option applies to BSMTP
20647 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
20648 &(lmtp)& and &(smtp)& transports.
20651 .option retry_use_local_part transports boolean "see below"
20652 .cindex "hints database" "retry keys"
20653 When a delivery suffers a temporary failure, a retry record is created
20654 in Exim's hints database. For remote deliveries, the key for the retry record
20655 is based on the name and/or IP address of the failing remote host. For local
20656 deliveries, the key is normally the entire address, including both the local
20657 part and the domain. This is suitable for most common cases of local delivery
20658 temporary failure &-- for example, exceeding a mailbox quota should delay only
20659 deliveries to that mailbox, not to the whole domain.
20661 However, in some special cases you may want to treat a temporary local delivery
20662 as a failure associated with the domain, and not with a particular local part.
20663 (For example, if you are storing all mail for some domain in files.) You can do
20664 this by setting &%retry_use_local_part%& false.
20666 For all the local transports, its default value is true. For remote transports,
20667 the default value is false for tidiness, but changing the value has no effect
20668 on a remote transport in the current implementation.
20671 .option return_path transports string&!! unset
20672 .cindex "envelope sender"
20673 .cindex "transport" "return path; changing"
20674 .cindex "return path" "changing in transport"
20675 If this option is set, the string is expanded at transport time and replaces
20676 the existing return path (envelope sender) value in the copy of the message
20677 that is being delivered. An empty return path is permitted. This feature is
20678 designed for remote deliveries, where the value of this option is used in the
20679 SMTP MAIL command. If you set &%return_path%& for a local transport, the
20680 only effect is to change the address that is placed in the &'Return-path:'&
20681 header line, if one is added to the message (see the next option).
20683 &*Note:*& A changed return path is not logged unless you add
20684 &%return_path_on_delivery%& to the log selector.
20686 .vindex "&$return_path$&"
20687 The expansion can refer to the existing value via &$return_path$&. This is
20688 either the message's envelope sender, or an address set by the
20689 &%errors_to%& option on a router. If the expansion is forced to fail, no
20690 replacement occurs; if it fails for another reason, delivery is deferred. This
20691 option can be used to support VERP (Variable Envelope Return Paths) &-- see
20692 section &<<SECTverp>>&.
20694 &*Note*&: If a delivery error is detected locally, including the case when a
20695 remote server rejects a message at SMTP time, the bounce message is not sent to
20696 the value of this option. It is sent to the previously set errors address.
20697 This defaults to the incoming sender address, but can be changed by setting
20698 &%errors_to%& in a router.
20702 .option return_path_add transports boolean false
20703 .cindex "&'Return-path:'& header line"
20704 If this option is true, a &'Return-path:'& header is added to the message.
20705 Although the return path is normally available in the prefix line of BSD
20706 mailboxes, this is commonly not displayed by MUAs, and so the user does not
20707 have easy access to it.
20709 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
20710 the delivery SMTP server makes the final delivery"&. This implies that this
20711 header should not be present in incoming messages. Exim has a configuration
20712 option, &%return_path_remove%&, which requests removal of this header from
20713 incoming messages, so that delivered messages can safely be resent to other
20717 .option shadow_condition transports string&!! unset
20718 See &%shadow_transport%& below.
20721 .option shadow_transport transports string unset
20722 .cindex "shadow transport"
20723 .cindex "transport" "shadow"
20724 A local transport may set the &%shadow_transport%& option to the name of
20725 another local transport. Shadow remote transports are not supported.
20727 Whenever a delivery to the main transport succeeds, and either
20728 &%shadow_condition%& is unset, or its expansion does not result in the empty
20729 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
20730 passed to the shadow transport, with the same delivery address or addresses. If
20731 expansion fails, no action is taken except that non-forced expansion failures
20732 cause a log line to be written.
20734 The result of the shadow transport is discarded and does not affect the
20735 subsequent processing of the message. Only a single level of shadowing is
20736 provided; the &%shadow_transport%& option is ignored on any transport when it
20737 is running as a shadow. Options concerned with output from pipes are also
20738 ignored. The log line for the successful delivery has an item added on the end,
20741 ST=<shadow transport name>
20743 If the shadow transport did not succeed, the error message is put in
20744 parentheses afterwards. Shadow transports can be used for a number of different
20745 purposes, including keeping more detailed log information than Exim normally
20746 provides, and implementing automatic acknowledgment policies based on message
20747 headers that some sites insist on.
20750 .option transport_filter transports string&!! unset
20751 .cindex "transport" "filter"
20752 .cindex "filter" "transport filter"
20753 This option sets up a filtering (in the Unix shell sense) process for messages
20754 at transport time. It should not be confused with mail filtering as set up by
20755 individual users or via a system filter.
20757 If unset, or expanding to an empty string, no filtering is done.
20760 When the message is about to be written out, the command specified by
20761 &%transport_filter%& is started up in a separate, parallel process, and
20762 the entire message, including the header lines, is passed to it on its standard
20763 input (this in fact is done from a third process, to avoid deadlock). The
20764 command must be specified as an absolute path.
20766 The lines of the message that are written to the transport filter are
20767 terminated by newline (&"\n"&). The message is passed to the filter before any
20768 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
20769 lines beginning with a dot, and also before any processing implied by the
20770 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
20771 &(pipe)& transports.
20773 The standard error for the filter process is set to the same destination as its
20774 standard output; this is read and written to the message's ultimate
20775 destination. The process that writes the message to the filter, the
20776 filter itself, and the original process that reads the result and delivers it
20777 are all run in parallel, like a shell pipeline.
20779 The filter can perform any transformations it likes, but of course should take
20780 care not to break RFC 2822 syntax. Exim does not check the result, except to
20781 test for a final newline when SMTP is in use. All messages transmitted over
20782 SMTP must end with a newline, so Exim supplies one if it is missing.
20784 .cindex "content scanning" "per user"
20785 A transport filter can be used to provide content-scanning on a per-user basis
20786 at delivery time if the only required effect of the scan is to modify the
20787 message. For example, a content scan could insert a new header line containing
20788 a spam score. This could be interpreted by a filter in the user's MUA. It is
20789 not possible to discard a message at this stage.
20791 .cindex "SMTP" "SIZE"
20792 A problem might arise if the filter increases the size of a message that is
20793 being sent down an SMTP connection. If the receiving SMTP server has indicated
20794 support for the SIZE parameter, Exim will have sent the size of the message
20795 at the start of the SMTP session. If what is actually sent is substantially
20796 more, the server might reject the message. This can be worked round by setting
20797 the &%size_addition%& option on the &(smtp)& transport, either to allow for
20798 additions to the message, or to disable the use of SIZE altogether.
20800 .vindex "&$pipe_addresses$&"
20801 The value of the &%transport_filter%& option is the command string for starting
20802 the filter, which is run directly from Exim, not under a shell. The string is
20803 parsed by Exim in the same way as a command string for the &(pipe)& transport:
20804 Exim breaks it up into arguments and then expands each argument separately (see
20805 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
20806 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
20807 of arguments, one for each address that applies to this delivery. (This isn't
20808 an ideal name for this feature here, but as it was already implemented for the
20809 &(pipe)& transport, it seemed sensible not to change it.)
20812 .vindex "&$host_address$&"
20813 The expansion variables &$host$& and &$host_address$& are available when the
20814 transport is a remote one. They contain the name and IP address of the host to
20815 which the message is being sent. For example:
20817 transport_filter = /some/directory/transport-filter.pl \
20818 $host $host_address $sender_address $pipe_addresses
20821 Two problems arise if you want to use more complicated expansion items to
20822 generate transport filter commands, both of which due to the fact that the
20823 command is split up &'before'& expansion.
20825 If an expansion item contains white space, you must quote it, so that it is all
20826 part of the same command item. If the entire option setting is one such
20827 expansion item, you have to take care what kind of quoting you use. For
20830 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
20832 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
20833 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
20834 stripped by Exim when it read the option's value. When the value is used, if
20835 the single quotes were missing, the line would be split into two items,
20836 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
20837 Exim tried to expand the first one.
20839 Except for the special case of &$pipe_addresses$& that is mentioned above, an
20840 expansion cannot generate multiple arguments, or a command name followed by
20841 arguments. Consider this example:
20843 transport_filter = ${lookup{$host}lsearch{/a/file}\
20844 {$value}{/bin/cat}}
20846 The result of the lookup is interpreted as the name of the command, even
20847 if it contains white space. The simplest way round this is to use a shell:
20849 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
20850 {$value}{/bin/cat}}
20854 The filter process is run under the same uid and gid as the normal delivery.
20855 For remote deliveries this is the Exim uid/gid by default. The command should
20856 normally yield a zero return code. Transport filters are not supposed to fail.
20857 A non-zero code is taken to mean that the transport filter encountered some
20858 serious problem. Delivery of the message is deferred; the message remains on
20859 the queue and is tried again later. It is not possible to cause a message to be
20860 bounced from a transport filter.
20862 If a transport filter is set on an autoreply transport, the original message is
20863 passed through the filter as it is being copied into the newly generated
20864 message, which happens if the &%return_message%& option is set.
20867 .option transport_filter_timeout transports time 5m
20868 .cindex "transport" "filter, timeout"
20869 When Exim is reading the output of a transport filter, it applies a timeout
20870 that can be set by this option. Exceeding the timeout is normally treated as a
20871 temporary delivery failure. However, if a transport filter is used with a
20872 &(pipe)& transport, a timeout in the transport filter is treated in the same
20873 way as a timeout in the pipe command itself. By default, a timeout is a hard
20874 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
20875 becomes a temporary error.
20878 .option user transports string&!! "Exim user"
20879 .cindex "uid (user id)" "local delivery"
20880 .cindex "transport" "user, specifying"
20881 This option specifies the user under whose uid the delivery process is to be
20882 run, overriding any uid that may have been set by the router. If the user is
20883 given as a name, the uid is looked up from the password data, and the
20884 associated group is taken as the value of the gid to be used if the &%group%&
20887 For deliveries that use local transports, a user and group are normally
20888 specified explicitly or implicitly (for example, as a result of
20889 &%check_local_user%&) by the router or transport.
20891 .cindex "hints database" "access by remote transport"
20892 For remote transports, you should leave this option unset unless you really are
20893 sure you know what you are doing. When a remote transport is running, it needs
20894 to be able to access Exim's hints databases, because each host may have its own
20896 .ecindex IIDgenoptra1
20897 .ecindex IIDgenoptra2
20898 .ecindex IIDgenoptra3
20905 . ////////////////////////////////////////////////////////////////////////////
20906 . ////////////////////////////////////////////////////////////////////////////
20908 .chapter "Address batching in local transports" "CHAPbatching" &&&
20910 .cindex "transport" "local; address batching in"
20911 The only remote transport (&(smtp)&) is normally configured to handle more than
20912 one address at a time, so that when several addresses are routed to the same
20913 remote host, just one copy of the message is sent. Local transports, however,
20914 normally handle one address at a time. That is, a separate instance of the
20915 transport is run for each address that is routed to the transport. A separate
20916 copy of the message is delivered each time.
20918 .cindex "batched local delivery"
20919 .oindex "&%batch_max%&"
20920 .oindex "&%batch_id%&"
20921 In special cases, it may be desirable to handle several addresses at once in a
20922 local transport, for example:
20925 In an &(appendfile)& transport, when storing messages in files for later
20926 delivery by some other means, a single copy of the message with multiple
20927 recipients saves space.
20929 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
20930 a single copy saves time, and is the normal way LMTP is expected to work.
20932 In a &(pipe)& transport, when passing the message
20933 to a scanner program or
20934 to some other delivery mechanism such as UUCP, multiple recipients may be
20938 These three local transports all have the same options for controlling multiple
20939 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
20940 repeating the information for each transport, these options are described here.
20942 The &%batch_max%& option specifies the maximum number of addresses that can be
20943 delivered together in a single run of the transport. Its default value is one
20944 (no batching). When more than one address is routed to a transport that has a
20945 &%batch_max%& value greater than one, the addresses are delivered in a batch
20946 (that is, in a single run of the transport with multiple recipients), subject
20947 to certain conditions:
20950 .vindex "&$local_part$&"
20951 If any of the transport's options contain a reference to &$local_part$&, no
20952 batching is possible.
20954 .vindex "&$domain$&"
20955 If any of the transport's options contain a reference to &$domain$&, only
20956 addresses with the same domain are batched.
20958 .cindex "customizing" "batching condition"
20959 If &%batch_id%& is set, it is expanded for each address, and only those
20960 addresses with the same expanded value are batched. This allows you to specify
20961 customized batching conditions. Failure of the expansion for any reason,
20962 including forced failure, disables batching, but it does not stop the delivery
20965 Batched addresses must also have the same errors address (where to send
20966 delivery errors), the same header additions and removals, the same user and
20967 group for the transport, and if a host list is present, the first host must
20971 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
20972 both when the file or pipe command is specified in the transport, and when it
20973 is specified by a &(redirect)& router, but all the batched addresses must of
20974 course be routed to the same file or pipe command. These two transports have an
20975 option called &%use_bsmtp%&, which causes them to deliver the message in
20976 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
20977 &%check_string%& and &%escape_string%& options are forced to the values
20980 escape_string = ".."
20982 when batched SMTP is in use. A full description of the batch SMTP mechanism is
20983 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
20984 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
20986 .cindex "&'Envelope-to:'& header line"
20987 If the generic &%envelope_to_add%& option is set for a batching transport, the
20988 &'Envelope-to:'& header that is added to the message contains all the addresses
20989 that are being processed together. If you are using a batching &(appendfile)&
20990 transport without &%use_bsmtp%&, the only way to preserve the recipient
20991 addresses is to set the &%envelope_to_add%& option.
20993 .cindex "&(pipe)& transport" "with multiple addresses"
20994 .vindex "&$pipe_addresses$&"
20995 If you are using a &(pipe)& transport without BSMTP, and setting the
20996 transport's &%command%& option, you can include &$pipe_addresses$& as part of
20997 the command. This is not a true variable; it is a bit of magic that causes each
20998 of the recipient addresses to be inserted into the command as a separate
20999 argument. This provides a way of accessing all the addresses that are being
21000 delivered in the batch. &*Note:*& This is not possible for pipe commands that
21001 are specified by a &(redirect)& router.
21006 . ////////////////////////////////////////////////////////////////////////////
21007 . ////////////////////////////////////////////////////////////////////////////
21009 .chapter "The appendfile transport" "CHAPappendfile"
21010 .scindex IIDapptra1 "&(appendfile)& transport"
21011 .scindex IIDapptra2 "transports" "&(appendfile)&"
21012 .cindex "directory creation"
21013 .cindex "creating directories"
21014 The &(appendfile)& transport delivers a message by appending it to an existing
21015 file, or by creating an entirely new file in a specified directory. Single
21016 files to which messages are appended can be in the traditional Unix mailbox
21017 format, or optionally in the MBX format supported by the Pine MUA and
21018 University of Washington IMAP daemon, &'inter alia'&. When each message is
21019 being delivered as a separate file, &"maildir"& format can optionally be used
21020 to give added protection against failures that happen part-way through the
21021 delivery. A third form of separate-file delivery known as &"mailstore"& is also
21022 supported. For all file formats, Exim attempts to create as many levels of
21023 directory as necessary, provided that &%create_directory%& is set.
21025 The code for the optional formats is not included in the Exim binary by
21026 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
21027 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
21030 .cindex "quota" "system"
21031 Exim recognizes system quota errors, and generates an appropriate message. Exim
21032 also supports its own quota control within the transport, for use when the
21033 system facility is unavailable or cannot be used for some reason.
21035 If there is an error while appending to a file (for example, quota exceeded or
21036 partition filled), Exim attempts to reset the file's length and last
21037 modification time back to what they were before. If there is an error while
21038 creating an entirely new file, the new file is removed.
21040 Before appending to a file, a number of security checks are made, and the
21041 file is locked. A detailed description is given below, after the list of
21044 The &(appendfile)& transport is most commonly used for local deliveries to
21045 users' mailboxes. However, it can also be used as a pseudo-remote transport for
21046 putting messages into files for remote delivery by some means other than Exim.
21047 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
21052 .section "The file and directory options" "SECTfildiropt"
21053 The &%file%& option specifies a single file, to which the message is appended;
21054 the &%directory%& option specifies a directory, in which a new file containing
21055 the message is created. Only one of these two options can be set, and for
21056 normal deliveries to mailboxes, one of them &'must'& be set.
21058 .vindex "&$address_file$&"
21059 .vindex "&$local_part$&"
21060 However, &(appendfile)& is also used for delivering messages to files or
21061 directories whose names (or parts of names) are obtained from alias,
21062 forwarding, or filtering operations (for example, a &%save%& command in a
21063 user's Exim filter). When such a transport is running, &$local_part$& contains
21064 the local part that was aliased or forwarded, and &$address_file$& contains the
21065 name (or partial name) of the file or directory generated by the redirection
21066 operation. There are two cases:
21069 If neither &%file%& nor &%directory%& is set, the redirection operation
21070 must specify an absolute path (one that begins with &`/`&). This is the most
21071 common case when users with local accounts use filtering to sort mail into
21072 different folders. See for example, the &(address_file)& transport in the
21073 default configuration. If the path ends with a slash, it is assumed to be the
21074 name of a directory. A delivery to a directory can also be forced by setting
21075 &%maildir_format%& or &%mailstore_format%&.
21077 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
21078 used to determine the file or directory name for the delivery. Normally, the
21079 contents of &$address_file$& are used in some way in the string expansion.
21083 .cindex "Sieve filter" "configuring &(appendfile)&"
21084 .cindex "Sieve filter" "relative mailbox path handling"
21085 As an example of the second case, consider an environment where users do not
21086 have home directories. They may be permitted to use Exim filter commands of the
21091 or Sieve filter commands of the form:
21093 require "fileinto";
21094 fileinto "folder23";
21096 In this situation, the expansion of &%file%& or &%directory%& in the transport
21097 must transform the relative path into an appropriate absolute file name. In the
21098 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
21099 is used as a result of a &"keep"& action in the filter. This example shows one
21100 way of handling this requirement:
21102 file = ${if eq{$address_file}{inbox} \
21103 {/var/mail/$local_part} \
21104 {${if eq{${substr_0_1:$address_file}}{/} \
21106 {$home/mail/$address_file} \
21110 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
21111 location, absolute paths are used without change, and other folders are in the
21112 &_mail_& directory within the home directory.
21114 &*Note 1*&: While processing an Exim filter, a relative path such as
21115 &_folder23_& is turned into an absolute path if a home directory is known to
21116 the router. In particular, this is the case if &%check_local_user%& is set. If
21117 you want to prevent this happening at routing time, you can set
21118 &%router_home_directory%& empty. This forces the router to pass the relative
21119 path to the transport.
21121 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
21122 the &%file%& or &%directory%& option is still used if it is set.
21127 .section "Private options for appendfile" "SECID134"
21128 .cindex "options" "&(appendfile)& transport"
21132 .option allow_fifo appendfile boolean false
21133 .cindex "fifo (named pipe)"
21134 .cindex "named pipe (fifo)"
21135 .cindex "pipe" "named (fifo)"
21136 Setting this option permits delivery to named pipes (FIFOs) as well as to
21137 regular files. If no process is reading the named pipe at delivery time, the
21138 delivery is deferred.
21141 .option allow_symlink appendfile boolean false
21142 .cindex "symbolic link" "to mailbox"
21143 .cindex "mailbox" "symbolic link"
21144 By default, &(appendfile)& will not deliver if the path name for the file is
21145 that of a symbolic link. Setting this option relaxes that constraint, but there
21146 are security issues involved in the use of symbolic links. Be sure you know
21147 what you are doing if you set this. Details of exactly what this option affects
21148 are included in the discussion which follows this list of options.
21151 .option batch_id appendfile string&!! unset
21152 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21153 However, batching is automatically disabled for &(appendfile)& deliveries that
21154 happen as a result of forwarding or aliasing or other redirection directly to a
21158 .option batch_max appendfile integer 1
21159 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21162 .option check_group appendfile boolean false
21163 When this option is set, the group owner of the file defined by the &%file%&
21164 option is checked to see that it is the same as the group under which the
21165 delivery process is running. The default setting is false because the default
21166 file mode is 0600, which means that the group is irrelevant.
21169 .option check_owner appendfile boolean true
21170 When this option is set, the owner of the file defined by the &%file%& option
21171 is checked to ensure that it is the same as the user under which the delivery
21172 process is running.
21175 .option check_string appendfile string "see below"
21176 .cindex "&""From""& line"
21177 As &(appendfile)& writes the message, the start of each line is tested for
21178 matching &%check_string%&, and if it does, the initial matching characters are
21179 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
21180 a literal string, not a regular expression, and the case of any letters it
21181 contains is significant.
21183 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
21184 are forced to &"."& and &".."& respectively, and any settings in the
21185 configuration are ignored. Otherwise, they default to &"From&~"& and
21186 &">From&~"& when the &%file%& option is set, and unset when any of the
21187 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
21189 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
21190 suitable for traditional &"BSD"& mailboxes, where a line beginning with
21191 &"From&~"& indicates the start of a new message. All four options need changing
21192 if another format is used. For example, to deliver to mailboxes in MMDF format:
21193 .cindex "MMDF format mailbox"
21194 .cindex "mailbox" "MMDF format"
21196 check_string = "\1\1\1\1\n"
21197 escape_string = "\1\1\1\1 \n"
21198 message_prefix = "\1\1\1\1\n"
21199 message_suffix = "\1\1\1\1\n"
21201 .option create_directory appendfile boolean true
21202 .cindex "directory creation"
21203 When this option is true, Exim attempts to create any missing superior
21204 directories for the file that it is about to write. A created directory's mode
21205 is given by the &%directory_mode%& option.
21207 The group ownership of a newly created directory is highly dependent on the
21208 operating system (and possibly the file system) that is being used. For
21209 example, in Solaris, if the parent directory has the setgid bit set, its group
21210 is propagated to the child; if not, the currently set group is used. However,
21211 in FreeBSD, the parent's group is always used.
21215 .option create_file appendfile string anywhere
21216 This option constrains the location of files and directories that are created
21217 by this transport. It applies to files defined by the &%file%& option and
21218 directories defined by the &%directory%& option. In the case of maildir
21219 delivery, it applies to the top level directory, not the maildir directories
21222 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
21223 &"belowhome"&. In the second and third cases, a home directory must have been
21224 set for the transport. This option is not useful when an explicit file name is
21225 given for normal mailbox deliveries. It is intended for the case when file
21226 names are generated from users' &_.forward_& files. These are usually handled
21227 by an &(appendfile)& transport called &%address_file%&. See also
21228 &%file_must_exist%&.
21231 .option directory appendfile string&!! unset
21232 This option is mutually exclusive with the &%file%& option, but one of &%file%&
21233 or &%directory%& must be set, unless the delivery is the direct result of a
21234 redirection (see section &<<SECTfildiropt>>&).
21236 When &%directory%& is set, the string is expanded, and the message is delivered
21237 into a new file or files in or below the given directory, instead of being
21238 appended to a single mailbox file. A number of different formats are provided
21239 (see &%maildir_format%& and &%mailstore_format%&), and see section
21240 &<<SECTopdir>>& for further details of this form of delivery.
21243 .option directory_file appendfile string&!! "see below"
21245 .vindex "&$inode$&"
21246 When &%directory%& is set, but neither &%maildir_format%& nor
21247 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
21248 whose name is obtained by expanding this string. The default value is:
21250 q${base62:$tod_epoch}-$inode
21252 This generates a unique name from the current time, in base 62 form, and the
21253 inode of the file. The variable &$inode$& is available only when expanding this
21257 .option directory_mode appendfile "octal integer" 0700
21258 If &(appendfile)& creates any directories as a result of the
21259 &%create_directory%& option, their mode is specified by this option.
21262 .option escape_string appendfile string "see description"
21263 See &%check_string%& above.
21266 .option file appendfile string&!! unset
21267 This option is mutually exclusive with the &%directory%& option, but one of
21268 &%file%& or &%directory%& must be set, unless the delivery is the direct result
21269 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
21270 specifies a single file, to which the message is appended. One or more of
21271 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
21274 .cindex "NFS" "lock file"
21275 .cindex "locking files"
21276 .cindex "lock files"
21277 If you are using more than one host to deliver over NFS into the same
21278 mailboxes, you should always use lock files.
21280 The string value is expanded for each delivery, and must yield an absolute
21281 path. The most common settings of this option are variations on one of these
21284 file = /var/spool/mail/$local_part
21285 file = /home/$local_part/inbox
21288 .cindex "&""sticky""& bit"
21289 In the first example, all deliveries are done into the same directory. If Exim
21290 is configured to use lock files (see &%use_lockfile%& below) it must be able to
21291 create a file in the directory, so the &"sticky"& bit must be turned on for
21292 deliveries to be possible, or alternatively the &%group%& option can be used to
21293 run the delivery under a group id which has write access to the directory.
21297 .option file_format appendfile string unset
21298 .cindex "file" "mailbox; checking existing format"
21299 This option requests the transport to check the format of an existing file
21300 before adding to it. The check consists of matching a specific string at the
21301 start of the file. The value of the option consists of an even number of
21302 colon-separated strings. The first of each pair is the test string, and the
21303 second is the name of a transport. If the transport associated with a matched
21304 string is not the current transport, control is passed over to the other
21305 transport. For example, suppose the standard &(local_delivery)& transport has
21308 file_format = "From : local_delivery :\
21309 \1\1\1\1\n : local_mmdf_delivery"
21311 Mailboxes that begin with &"From"& are still handled by this transport, but if
21312 a mailbox begins with four binary ones followed by a newline, control is passed
21313 to a transport called &%local_mmdf_delivery%&, which presumably is configured
21314 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
21315 is assumed to match the current transport. If the start of a mailbox doesn't
21316 match any string, or if the transport named for a given string is not defined,
21317 delivery is deferred.
21320 .option file_must_exist appendfile boolean false
21321 If this option is true, the file specified by the &%file%& option must exist.
21322 A temporary error occurs if it does not, causing delivery to be deferred.
21323 If this option is false, the file is created if it does not exist.
21326 .option lock_fcntl_timeout appendfile time 0s
21327 .cindex "timeout" "mailbox locking"
21328 .cindex "mailbox" "locking, blocking and non-blocking"
21329 .cindex "locking files"
21330 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
21331 when locking an open mailbox file. If the call fails, the delivery process
21332 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
21333 Non-blocking calls are used so that the file is not kept open during the wait
21334 for the lock; the reason for this is to make it as safe as possible for
21335 deliveries over NFS in the case when processes might be accessing an NFS
21336 mailbox without using a lock file. This should not be done, but
21337 misunderstandings and hence misconfigurations are not unknown.
21339 On a busy system, however, the performance of a non-blocking lock approach is
21340 not as good as using a blocking lock with a timeout. In this case, the waiting
21341 is done inside the system call, and Exim's delivery process acquires the lock
21342 and can proceed as soon as the previous lock holder releases it.
21344 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
21345 timeout, are used. There may still be some retrying: the maximum number of
21348 (lock_retries * lock_interval) / lock_fcntl_timeout
21350 rounded up to the next whole number. In other words, the total time during
21351 which &(appendfile)& is trying to get a lock is roughly the same, unless
21352 &%lock_fcntl_timeout%& is set very large.
21354 You should consider setting this option if you are getting a lot of delayed
21355 local deliveries because of errors of the form
21357 failed to lock mailbox /some/file (fcntl)
21360 .option lock_flock_timeout appendfile time 0s
21361 This timeout applies to file locking when using &[flock()]& (see
21362 &%use_flock%&); the timeout operates in a similar manner to
21363 &%lock_fcntl_timeout%&.
21366 .option lock_interval appendfile time 3s
21367 This specifies the time to wait between attempts to lock the file. See below
21368 for details of locking.
21371 .option lock_retries appendfile integer 10
21372 This specifies the maximum number of attempts to lock the file. A value of zero
21373 is treated as 1. See below for details of locking.
21376 .option lockfile_mode appendfile "octal integer" 0600
21377 This specifies the mode of the created lock file, when a lock file is being
21378 used (see &%use_lockfile%& and &%use_mbx_lock%&).
21381 .option lockfile_timeout appendfile time 30m
21382 .cindex "timeout" "mailbox locking"
21383 When a lock file is being used (see &%use_lockfile%&), if a lock file already
21384 exists and is older than this value, it is assumed to have been left behind by
21385 accident, and Exim attempts to remove it.
21388 .option mailbox_filecount appendfile string&!! unset
21389 .cindex "mailbox" "specifying size of"
21390 .cindex "size" "of mailbox"
21391 If this option is set, it is expanded, and the result is taken as the current
21392 number of files in the mailbox. It must be a decimal number, optionally
21393 followed by K or M. This provides a way of obtaining this information from an
21394 external source that maintains the data.
21397 .option mailbox_size appendfile string&!! unset
21398 .cindex "mailbox" "specifying size of"
21399 .cindex "size" "of mailbox"
21400 If this option is set, it is expanded, and the result is taken as the current
21401 size the mailbox. It must be a decimal number, optionally followed by K or M.
21402 This provides a way of obtaining this information from an external source that
21403 maintains the data. This is likely to be helpful for maildir deliveries where
21404 it is computationally expensive to compute the size of a mailbox.
21408 .option maildir_format appendfile boolean false
21409 .cindex "maildir format" "specifying"
21410 If this option is set with the &%directory%& option, the delivery is into a new
21411 file, in the &"maildir"& format that is used by other mail software. When the
21412 transport is activated directly from a &(redirect)& router (for example, the
21413 &(address_file)& transport in the default configuration), setting
21414 &%maildir_format%& causes the path received from the router to be treated as a
21415 directory, whether or not it ends with &`/`&. This option is available only if
21416 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
21417 &<<SECTmaildirdelivery>>& below for further details.
21420 .option maildir_quota_directory_regex appendfile string "See below"
21421 .cindex "maildir format" "quota; directories included in"
21422 .cindex "quota" "maildir; directories included in"
21423 This option is relevant only when &%maildir_use_size_file%& is set. It defines
21424 a regular expression for specifying directories, relative to the quota
21425 directory (see &%quota_directory%&), that should be included in the quota
21426 calculation. The default value is:
21428 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
21430 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
21431 (directories whose names begin with a dot). If you want to exclude the
21433 folder from the count (as some sites do), you need to change this setting to
21435 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
21437 This uses a negative lookahead in the regular expression to exclude the
21438 directory whose name is &_.Trash_&. When a directory is excluded from quota
21439 calculations, quota processing is bypassed for any messages that are delivered
21440 directly into that directory.
21443 .option maildir_retries appendfile integer 10
21444 This option specifies the number of times to retry when writing a file in
21445 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
21448 .option maildir_tag appendfile string&!! unset
21449 This option applies only to deliveries in maildir format, and is described in
21450 section &<<SECTmaildirdelivery>>& below.
21453 .option maildir_use_size_file appendfile&!! boolean false
21454 .cindex "maildir format" "&_maildirsize_& file"
21455 The result of string expansion for this option must be a valid boolean value.
21456 If it is true, it enables support for &_maildirsize_& files. Exim
21457 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
21458 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
21459 value is zero. See &%maildir_quota_directory_regex%& above and section
21460 &<<SECTmaildirdelivery>>& below for further details.
21462 .option maildirfolder_create_regex appendfile string unset
21463 .cindex "maildir format" "&_maildirfolder_& file"
21464 .cindex "&_maildirfolder_&, creating"
21465 The value of this option is a regular expression. If it is unset, it has no
21466 effect. Otherwise, before a maildir delivery takes place, the pattern is
21467 matched against the name of the maildir directory, that is, the directory
21468 containing the &_new_& and &_tmp_& subdirectories that will be used for the
21469 delivery. If there is a match, Exim checks for the existence of a file called
21470 &_maildirfolder_& in the directory, and creates it if it does not exist.
21471 See section &<<SECTmaildirdelivery>>& for more details.
21474 .option mailstore_format appendfile boolean false
21475 .cindex "mailstore format" "specifying"
21476 If this option is set with the &%directory%& option, the delivery is into two
21477 new files in &"mailstore"& format. The option is available only if
21478 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
21479 below for further details.
21482 .option mailstore_prefix appendfile string&!! unset
21483 This option applies only to deliveries in mailstore format, and is described in
21484 section &<<SECTopdir>>& below.
21487 .option mailstore_suffix appendfile string&!! unset
21488 This option applies only to deliveries in mailstore format, and is described in
21489 section &<<SECTopdir>>& below.
21492 .option mbx_format appendfile boolean false
21493 .cindex "locking files"
21494 .cindex "file" "locking"
21495 .cindex "file" "MBX format"
21496 .cindex "MBX format, specifying"
21497 This option is available only if Exim has been compiled with SUPPORT_MBX
21498 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
21499 the message is appended to the mailbox file in MBX format instead of
21500 traditional Unix format. This format is supported by Pine4 and its associated
21501 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
21503 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
21504 automatically changed by the use of &%mbx_format%&. They should normally be set
21505 empty when using MBX format, so this option almost always appears in this
21512 If none of the locking options are mentioned in the configuration,
21513 &%use_mbx_lock%& is assumed and the other locking options default to false. It
21514 is possible to specify the other kinds of locking with &%mbx_format%&, but
21515 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
21516 interworks with &'c-client'&, providing for shared access to the mailbox. It
21517 should not be used if any program that does not use this form of locking is
21518 going to access the mailbox, nor should it be used if the mailbox file is NFS
21519 mounted, because it works only when the mailbox is accessed from a single host.
21521 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
21522 the standard version of &'c-client'&, because as long as it has a mailbox open
21523 (this means for the whole of a Pine or IMAP session), Exim will not be able to
21524 append messages to it.
21527 .option message_prefix appendfile string&!! "see below"
21528 .cindex "&""From""& line"
21529 The string specified here is expanded and output at the start of every message.
21530 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
21531 in which case it is:
21533 message_prefix = "From ${if def:return_path{$return_path}\
21534 {MAILER-DAEMON}} $tod_bsdinbox\n"
21536 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21537 &`\n`& to &`\r\n`& in &%message_prefix%&.
21539 .option message_suffix appendfile string&!! "see below"
21540 The string specified here is expanded and output at the end of every message.
21541 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
21542 in which case it is a single newline character. The suffix can be suppressed by
21547 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21548 &`\n`& to &`\r\n`& in &%message_suffix%&.
21550 .option mode appendfile "octal integer" 0600
21551 If the output file is created, it is given this mode. If it already exists and
21552 has wider permissions, they are reduced to this mode. If it has narrower
21553 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
21554 if the delivery is the result of a &%save%& command in a filter file specifying
21555 a particular mode, the mode of the output file is always forced to take that
21556 value, and this option is ignored.
21559 .option mode_fail_narrower appendfile boolean true
21560 This option applies in the case when an existing mailbox file has a narrower
21561 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
21562 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
21563 continues with the delivery attempt, using the existing mode of the file.
21566 .option notify_comsat appendfile boolean false
21567 If this option is true, the &'comsat'& daemon is notified after every
21568 successful delivery to a user mailbox. This is the daemon that notifies logged
21569 on users about incoming mail.
21572 .option quota appendfile string&!! unset
21573 .cindex "quota" "imposed by Exim"
21574 This option imposes a limit on the size of the file to which Exim is appending,
21575 or to the total space used in the directory tree when the &%directory%& option
21576 is set. In the latter case, computation of the space used is expensive, because
21577 all the files in the directory (and any sub-directories) have to be
21578 individually inspected and their sizes summed. (See &%quota_size_regex%& and
21579 &%maildir_use_size_file%& for ways to avoid this in environments where users
21580 have no shell access to their mailboxes).
21582 As there is no interlock against two simultaneous deliveries into a
21583 multi-file mailbox, it is possible for the quota to be overrun in this case.
21584 For single-file mailboxes, of course, an interlock is a necessity.
21586 A file's size is taken as its &'used'& value. Because of blocking effects, this
21587 may be a lot less than the actual amount of disk space allocated to the file.
21588 If the sizes of a number of files are being added up, the rounding effect can
21589 become quite noticeable, especially on systems that have large block sizes.
21590 Nevertheless, it seems best to stick to the &'used'& figure, because this is
21591 the obvious value which users understand most easily.
21593 The value of the option is expanded, and must then be a numerical value
21594 (decimal point allowed), optionally followed by one of the letters K, M, or G,
21595 for kilobytes, megabytes, or gigabytes. If Exim is running on a system with
21596 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
21599 &*Note*&: A value of zero is interpreted as &"no quota"&.
21601 The expansion happens while Exim is running as root, before it changes uid for
21602 the delivery. This means that files that are inaccessible to the end user can
21603 be used to hold quota values that are looked up in the expansion. When delivery
21604 fails because this quota is exceeded, the handling of the error is as for
21605 system quota failures.
21607 By default, Exim's quota checking mimics system quotas, and restricts the
21608 mailbox to the specified maximum size, though the value is not accurate to the
21609 last byte, owing to separator lines and additional headers that may get added
21610 during message delivery. When a mailbox is nearly full, large messages may get
21611 refused even though small ones are accepted, because the size of the current
21612 message is added to the quota when the check is made. This behaviour can be
21613 changed by setting &%quota_is_inclusive%& false. When this is done, the check
21614 for exceeding the quota does not include the current message. Thus, deliveries
21615 continue until the quota has been exceeded; thereafter, no further messages are
21616 delivered. See also &%quota_warn_threshold%&.
21619 .option quota_directory appendfile string&!! unset
21620 This option defines the directory to check for quota purposes when delivering
21621 into individual files. The default is the delivery directory, or, if a file
21622 called &_maildirfolder_& exists in a maildir directory, the parent of the
21623 delivery directory.
21626 .option quota_filecount appendfile string&!! 0
21627 This option applies when the &%directory%& option is set. It limits the total
21628 number of files in the directory (compare the inode limit in system quotas). It
21629 can only be used if &%quota%& is also set. The value is expanded; an expansion
21630 failure causes delivery to be deferred. A value of zero is interpreted as
21634 .option quota_is_inclusive appendfile boolean true
21635 See &%quota%& above.
21638 .option quota_size_regex appendfile string unset
21639 This option applies when one of the delivery modes that writes a separate file
21640 for each message is being used. When Exim wants to find the size of one of
21641 these files in order to test the quota, it first checks &%quota_size_regex%&.
21642 If this is set to a regular expression that matches the file name, and it
21643 captures one string, that string is interpreted as a representation of the
21644 file's size. The value of &%quota_size_regex%& is not expanded.
21646 This feature is useful only when users have no shell access to their mailboxes
21647 &-- otherwise they could defeat the quota simply by renaming the files. This
21648 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
21649 the file length to the file name. For example:
21651 maildir_tag = ,S=$message_size
21652 quota_size_regex = ,S=(\d+)
21654 An alternative to &$message_size$& is &$message_linecount$&, which contains the
21655 number of lines in the message.
21657 The regular expression should not assume that the length is at the end of the
21658 file name (even though &%maildir_tag%& puts it there) because maildir MUAs
21659 sometimes add other information onto the ends of message file names.
21661 Section &<<SECID136>>& contains further information.
21664 .option quota_warn_message appendfile string&!! "see below"
21665 See below for the use of this option. If it is not set when
21666 &%quota_warn_threshold%& is set, it defaults to
21668 quota_warn_message = "\
21669 To: $local_part@$domain\n\
21670 Subject: Your mailbox\n\n\
21671 This message is automatically created \
21672 by mail delivery software.\n\n\
21673 The size of your mailbox has exceeded \
21674 a warning threshold that is\n\
21675 set by the system administrator.\n"
21679 .option quota_warn_threshold appendfile string&!! 0
21680 .cindex "quota" "warning threshold"
21681 .cindex "mailbox" "size warning"
21682 .cindex "size" "of mailbox"
21683 This option is expanded in the same way as &%quota%& (see above). If the
21684 resulting value is greater than zero, and delivery of the message causes the
21685 size of the file or total space in the directory tree to cross the given
21686 threshold, a warning message is sent. If &%quota%& is also set, the threshold
21687 may be specified as a percentage of it by following the value with a percent
21691 quota_warn_threshold = 75%
21693 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
21694 percent sign is ignored.
21696 The warning message itself is specified by the &%quota_warn_message%& option,
21697 and it must start with a &'To:'& header line containing the recipient(s) of the
21698 warning message. These do not necessarily have to include the recipient(s) of
21699 the original message. A &'Subject:'& line should also normally be supplied. You
21700 can include any other header lines that you want. If you do not include a
21701 &'From:'& line, the default is:
21703 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
21705 .oindex &%errors_reply_to%&
21706 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
21709 The &%quota%& option does not have to be set in order to use this option; they
21710 are independent of one another except when the threshold is specified as a
21714 .option use_bsmtp appendfile boolean false
21715 .cindex "envelope sender"
21716 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
21717 format, with the envelope sender and recipient(s) included as SMTP commands. If
21718 you want to include a leading HELO command with such messages, you can do
21719 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
21720 for details of batch SMTP.
21723 .option use_crlf appendfile boolean false
21724 .cindex "carriage return"
21726 This option causes lines to be terminated with the two-character CRLF sequence
21727 (carriage return, linefeed) instead of just a linefeed character. In the case
21728 of batched SMTP, the byte sequence written to the file is then an exact image
21729 of what would be sent down a real SMTP connection.
21731 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
21732 (which are used to supply the traditional &"From&~"& and blank line separators
21733 in Berkeley-style mailboxes) are written verbatim, so must contain their own
21734 carriage return characters if these are needed. In cases where these options
21735 have non-empty defaults, the values end with a single linefeed, so they must be
21736 changed to end with &`\r\n`& if &%use_crlf%& is set.
21739 .option use_fcntl_lock appendfile boolean "see below"
21740 This option controls the use of the &[fcntl()]& function to lock a file for
21741 exclusive use when a message is being appended. It is set by default unless
21742 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
21743 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
21744 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
21747 .option use_flock_lock appendfile boolean false
21748 This option is provided to support the use of &[flock()]& for file locking, for
21749 the few situations where it is needed. Most modern operating systems support
21750 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
21751 each other. Exim uses &[fcntl()]& locking by default.
21753 This option is required only if you are using an operating system where
21754 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
21755 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
21756 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
21758 .cindex "Solaris" "&[flock()]& support"
21759 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
21760 have it (and some, I think, provide a not quite right version built on top of
21761 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
21762 the ability to use it, and any attempt to do so will cause a configuration
21765 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
21766 is just being mapped onto &[fcntl()]& by the OS).
21769 .option use_lockfile appendfile boolean "see below"
21770 If this option is turned off, Exim does not attempt to create a lock file when
21771 appending to a mailbox file. In this situation, the only locking is by
21772 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
21773 sure that every MUA that is ever going to look at your users' mailboxes uses
21774 &[fcntl()]& rather than a lock file, and even then only when you are not
21775 delivering over NFS from more than one host.
21777 .cindex "NFS" "lock file"
21778 In order to append to an NFS file safely from more than one host, it is
21779 necessary to take out a lock &'before'& opening the file, and the lock file
21780 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
21783 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
21784 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
21785 except when &%mbx_format%& is set.
21788 .option use_mbx_lock appendfile boolean "see below"
21789 This option is available only if Exim has been compiled with SUPPORT_MBX
21790 set in &_Local/Makefile_&. Setting the option specifies that special MBX
21791 locking rules be used. It is set by default if &%mbx_format%& is set and none
21792 of the locking options are mentioned in the configuration. The locking rules
21793 are the same as are used by the &'c-client'& library that underlies Pine and
21794 the IMAP4 and POP daemons that come with it (see the discussion below). The
21795 rules allow for shared access to the mailbox. However, this kind of locking
21796 does not work when the mailbox is NFS mounted.
21798 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
21799 &%use_flock_lock%& to control what kind of locking is used in implementing the
21800 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
21801 without &%use_fcntl_lock%& or &%use_flock_lock%&.
21806 .section "Operational details for appending" "SECTopappend"
21807 .cindex "appending to a file"
21808 .cindex "file" "appending"
21809 Before appending to a file, the following preparations are made:
21812 If the name of the file is &_/dev/null_&, no action is taken, and a success
21816 .cindex "directory creation"
21817 If any directories on the file's path are missing, Exim creates them if the
21818 &%create_directory%& option is set. A created directory's mode is given by the
21819 &%directory_mode%& option.
21822 If &%file_format%& is set, the format of an existing file is checked. If this
21823 indicates that a different transport should be used, control is passed to that
21827 .cindex "file" "locking"
21828 .cindex "locking files"
21829 .cindex "NFS" "lock file"
21830 If &%use_lockfile%& is set, a lock file is built in a way that will work
21831 reliably over NFS, as follows:
21834 Create a &"hitching post"& file whose name is that of the lock file with the
21835 current time, primary host name, and process id added, by opening for writing
21836 as a new file. If this fails with an access error, delivery is deferred.
21838 Close the hitching post file, and hard link it to the lock file name.
21840 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
21841 Unlink the hitching post name.
21843 Otherwise, use &[stat()]& to get information about the hitching post file, and
21844 then unlink hitching post name. If the number of links is exactly two, creation
21845 of the lock file succeeded but something (for example, an NFS server crash and
21846 restart) caused this fact not to be communicated to the &[link()]& call.
21848 If creation of the lock file failed, wait for &%lock_interval%& and try again,
21849 up to &%lock_retries%& times. However, since any program that writes to a
21850 mailbox should complete its task very quickly, it is reasonable to time out old
21851 lock files that are normally the result of user agent and system crashes. If an
21852 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
21853 it before trying again.
21857 A call is made to &[lstat()]& to discover whether the main file exists, and if
21858 so, what its characteristics are. If &[lstat()]& fails for any reason other
21859 than non-existence, delivery is deferred.
21862 .cindex "symbolic link" "to mailbox"
21863 .cindex "mailbox" "symbolic link"
21864 If the file does exist and is a symbolic link, delivery is deferred, unless the
21865 &%allow_symlink%& option is set, in which case the ownership of the link is
21866 checked, and then &[stat()]& is called to find out about the real file, which
21867 is then subjected to the checks below. The check on the top-level link
21868 ownership prevents one user creating a link for another's mailbox in a sticky
21869 directory, though allowing symbolic links in this case is definitely not a good
21870 idea. If there is a chain of symbolic links, the intermediate ones are not
21874 If the file already exists but is not a regular file, or if the file's owner
21875 and group (if the group is being checked &-- see &%check_group%& above) are
21876 different from the user and group under which the delivery is running,
21877 delivery is deferred.
21880 If the file's permissions are more generous than specified, they are reduced.
21881 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
21882 is set false, in which case the delivery is tried using the existing
21886 The file's inode number is saved, and the file is then opened for appending.
21887 If this fails because the file has vanished, &(appendfile)& behaves as if it
21888 hadn't existed (see below). For any other failures, delivery is deferred.
21891 If the file is opened successfully, check that the inode number hasn't
21892 changed, that it is still a regular file, and that the owner and permissions
21893 have not changed. If anything is wrong, defer delivery and freeze the message.
21896 If the file did not exist originally, defer delivery if the &%file_must_exist%&
21897 option is set. Otherwise, check that the file is being created in a permitted
21898 directory if the &%create_file%& option is set (deferring on failure), and then
21899 open for writing as a new file, with the O_EXCL and O_CREAT options,
21900 except when dealing with a symbolic link (the &%allow_symlink%& option must be
21901 set). In this case, which can happen if the link points to a non-existent file,
21902 the file is opened for writing using O_CREAT but not O_EXCL, because
21903 that prevents link following.
21906 .cindex "loop" "while file testing"
21907 If opening fails because the file exists, obey the tests given above for
21908 existing files. However, to avoid looping in a situation where the file is
21909 being continuously created and destroyed, the exists/not-exists loop is broken
21910 after 10 repetitions, and the message is then frozen.
21913 If opening fails with any other error, defer delivery.
21916 .cindex "file" "locking"
21917 .cindex "locking files"
21918 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
21919 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
21920 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
21921 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
21922 file, and an exclusive lock on the file whose name is
21924 /tmp/.<device-number>.<inode-number>
21926 using the device and inode numbers of the open mailbox file, in accordance with
21927 the MBX locking rules. This file is created with a mode that is specified by
21928 the &%lockfile_mode%& option.
21930 If Exim fails to lock the file, there are two possible courses of action,
21931 depending on the value of the locking timeout. This is obtained from
21932 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
21934 If the timeout value is zero, the file is closed, Exim waits for
21935 &%lock_interval%&, and then goes back and re-opens the file as above and tries
21936 to lock it again. This happens up to &%lock_retries%& times, after which the
21937 delivery is deferred.
21939 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
21940 &[flock()]& are used (with the given timeout), so there has already been some
21941 waiting involved by the time locking fails. Nevertheless, Exim does not give up
21942 immediately. It retries up to
21944 (lock_retries * lock_interval) / <timeout>
21946 times (rounded up).
21949 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
21950 and/or &[flock()]& locks) and then deletes the lock file if one was created.
21953 .section "Operational details for delivery to a new file" "SECTopdir"
21954 .cindex "delivery" "to single file"
21955 .cindex "&""From""& line"
21956 When the &%directory%& option is set instead of &%file%&, each message is
21957 delivered into a newly-created file or set of files. When &(appendfile)& is
21958 activated directly from a &(redirect)& router, neither &%file%& nor
21959 &%directory%& is normally set, because the path for delivery is supplied by the
21960 router. (See for example, the &(address_file)& transport in the default
21961 configuration.) In this case, delivery is to a new file if either the path name
21962 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
21964 No locking is required while writing the message to a new file, so the various
21965 locking options of the transport are ignored. The &"From"& line that by default
21966 separates messages in a single file is not normally needed, nor is the escaping
21967 of message lines that start with &"From"&, and there is no need to ensure a
21968 newline at the end of each message. Consequently, the default values for
21969 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
21970 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
21972 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
21973 the files in the delivery directory by default. However, you can specify a
21974 different directory by setting &%quota_directory%&. Also, for maildir
21975 deliveries (see below) the &_maildirfolder_& convention is honoured.
21978 .cindex "maildir format"
21979 .cindex "mailstore format"
21980 There are three different ways in which delivery to individual files can be
21981 done, controlled by the settings of the &%maildir_format%& and
21982 &%mailstore_format%& options. Note that code to support maildir or mailstore
21983 formats is not included in the binary unless SUPPORT_MAILDIR or
21984 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
21986 .cindex "directory creation"
21987 In all three cases an attempt is made to create the directory and any necessary
21988 sub-directories if they do not exist, provided that the &%create_directory%&
21989 option is set (the default). The location of a created directory can be
21990 constrained by setting &%create_file%&. A created directory's mode is given by
21991 the &%directory_mode%& option. If creation fails, or if the
21992 &%create_directory%& option is not set when creation is required, delivery is
21997 .section "Maildir delivery" "SECTmaildirdelivery"
21998 .cindex "maildir format" "description of"
21999 If the &%maildir_format%& option is true, Exim delivers each message by writing
22000 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
22001 directory that is defined by the &%directory%& option (the &"delivery
22002 directory"&). If the delivery is successful, the file is renamed into the
22003 &_new_& subdirectory.
22005 In the file name, <&'stime'&> is the current time of day in seconds, and
22006 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
22007 Exim checks that the time-of-day clock has moved on by at least one microsecond
22008 before terminating the delivery process. This guarantees uniqueness for the
22009 file name. However, as a precaution, Exim calls &[stat()]& for the file before
22010 opening it. If any response other than ENOENT (does not exist) is given,
22011 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
22013 Before Exim carries out a maildir delivery, it ensures that subdirectories
22014 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
22015 do not exist, Exim tries to create them and any superior directories in their
22016 path, subject to the &%create_directory%& and &%create_file%& options. If the
22017 &%maildirfolder_create_regex%& option is set, and the regular expression it
22018 contains matches the delivery directory, Exim also ensures that a file called
22019 &_maildirfolder_& exists in the delivery directory. If a missing directory or
22020 &_maildirfolder_& file cannot be created, delivery is deferred.
22022 These features make it possible to use Exim to create all the necessary files
22023 and directories in a maildir mailbox, including subdirectories for maildir++
22024 folders. Consider this example:
22026 maildir_format = true
22027 directory = /var/mail/$local_part\
22028 ${if eq{$local_part_suffix}{}{}\
22029 {/.${substr_1:$local_part_suffix}}}
22030 maildirfolder_create_regex = /\.[^/]+$
22032 If &$local_part_suffix$& is empty (there was no suffix for the local part),
22033 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
22034 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
22035 not match this name, so Exim will not look for or create the file
22036 &_/var/mail/pimbo/maildirfolder_&, though it will create
22037 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
22039 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
22040 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
22041 does match &%maildirfolder_create_regex%&. In this case, Exim will create
22042 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
22043 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
22045 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
22046 not inadvertently match the toplevel maildir directory, because a
22047 &_maildirfolder_& file at top level would completely break quota calculations.
22049 .cindex "quota" "in maildir delivery"
22050 .cindex "maildir++"
22051 If Exim is required to check a &%quota%& setting before a maildir delivery, and
22052 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
22053 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
22054 Exim assumes the directory is a maildir++ folder directory, which is one level
22055 down from the user's top level mailbox directory. This causes it to start at
22056 the parent directory instead of the current directory when calculating the
22057 amount of space used.
22059 One problem with delivering into a multi-file mailbox is that it is
22060 computationally expensive to compute the size of the mailbox for quota
22061 checking. Various approaches have been taken to reduce the amount of work
22062 needed. The next two sections describe two of them. A third alternative is to
22063 use some external process for maintaining the size data, and use the expansion
22064 of the &%mailbox_size%& option as a way of importing it into Exim.
22069 .section "Using tags to record message sizes" "SECID135"
22070 If &%maildir_tag%& is set, the string is expanded for each delivery.
22071 When the maildir file is renamed into the &_new_& sub-directory, the
22072 tag is added to its name. However, if adding the tag takes the length of the
22073 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
22074 the tag is dropped and the maildir file is created with no tag.
22077 .vindex "&$message_size$&"
22078 Tags can be used to encode the size of files in their names; see
22079 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
22080 happens after the message has been written. The value of the &$message_size$&
22081 variable is set to the number of bytes actually written. If the expansion is
22082 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
22083 be deferred. The expanded tag may contain any printing characters except &"/"&.
22084 Non-printing characters in the string are ignored; if the resulting string is
22085 empty, it is ignored. If it starts with an alphanumeric character, a leading
22086 colon is inserted; this default has not proven to be the path that popular
22087 maildir implementations have chosen (but changing it in Exim would break
22088 backwards compatibility).
22090 For one common implementation, you might set:
22092 maildir_tag = ,S=${message_size}
22094 but you should check the documentation of the other software to be sure.
22096 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
22097 as this allows Exim to extract the size from your tag, instead of having to
22098 &[stat()]& each message file.
22101 .section "Using a maildirsize file" "SECID136"
22102 .cindex "quota" "in maildir delivery"
22103 .cindex "maildir format" "&_maildirsize_& file"
22104 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
22105 storing quota and message size information in a file called &_maildirsize_&
22106 within the toplevel maildir directory. If this file does not exist, Exim
22107 creates it, setting the quota from the &%quota%& option of the transport. If
22108 the maildir directory itself does not exist, it is created before any attempt
22109 to write a &_maildirsize_& file.
22111 The &_maildirsize_& file is used to hold information about the sizes of
22112 messages in the maildir, thus speeding up quota calculations. The quota value
22113 in the file is just a cache; if the quota is changed in the transport, the new
22114 value overrides the cached value when the next message is delivered. The cache
22115 is maintained for the benefit of other programs that access the maildir and
22116 need to know the quota.
22118 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
22119 file is maintained (with a zero quota setting), but no quota is imposed.
22121 A regular expression is available for controlling which directories in the
22122 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
22123 See the description of the &%maildir_quota_directory_regex%& option above for
22127 .section "Mailstore delivery" "SECID137"
22128 .cindex "mailstore format" "description of"
22129 If the &%mailstore_format%& option is true, each message is written as two
22130 files in the given directory. A unique base name is constructed from the
22131 message id and the current delivery process, and the files that are written use
22132 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
22133 contains the message's envelope, and the &_.msg_& file contains the message
22134 itself. The base name is placed in the variable &$mailstore_basename$&.
22136 During delivery, the envelope is first written to a file with the suffix
22137 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
22138 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
22139 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
22140 file before accessing either of them. An alternative approach is to wait for
22141 the absence of a &_.tmp_& file.
22143 The envelope file starts with any text defined by the &%mailstore_prefix%&
22144 option, expanded and terminated by a newline if there isn't one. Then follows
22145 the sender address on one line, then all the recipient addresses, one per line.
22146 There can be more than one recipient only if the &%batch_max%& option is set
22147 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
22148 appended to the file, followed by a newline if it does not end with one.
22150 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
22151 failure, it is ignored. Other expansion errors are treated as serious
22152 configuration errors, and delivery is deferred. The variable
22153 &$mailstore_basename$& is available for use during these expansions.
22156 .section "Non-special new file delivery" "SECID138"
22157 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
22158 file is created directly in the named directory. For example, when delivering
22159 messages into files in batched SMTP format for later delivery to some host (see
22160 section &<<SECTbatchSMTP>>&), a setting such as
22162 directory = /var/bsmtp/$host
22164 might be used. A message is written to a file with a temporary name, which is
22165 then renamed when the delivery is complete. The final name is obtained by
22166 expanding the contents of the &%directory_file%& option.
22167 .ecindex IIDapptra1
22168 .ecindex IIDapptra2
22175 . ////////////////////////////////////////////////////////////////////////////
22176 . ////////////////////////////////////////////////////////////////////////////
22178 .chapter "The autoreply transport" "CHID8"
22179 .scindex IIDauttra1 "transports" "&(autoreply)&"
22180 .scindex IIDauttra2 "&(autoreply)& transport"
22181 The &(autoreply)& transport is not a true transport in that it does not cause
22182 the message to be transmitted. Instead, it generates a new mail message as an
22183 automatic reply to the incoming message. &'References:'& and
22184 &'Auto-Submitted:'& header lines are included. These are constructed according
22185 to the rules in RFCs 2822 and 3834, respectively.
22187 If the router that passes the message to this transport does not have the
22188 &%unseen%& option set, the original message (for the current recipient) is not
22189 delivered anywhere. However, when the &%unseen%& option is set on the router
22190 that passes the message to this transport, routing of the address continues, so
22191 another router can set up a normal message delivery.
22194 The &(autoreply)& transport is usually run as the result of mail filtering, a
22195 &"vacation"& message being the standard example. However, it can also be run
22196 directly from a router like any other transport. To reduce the possibility of
22197 message cascades, messages created by the &(autoreply)& transport always have
22198 empty envelope sender addresses, like bounce messages.
22200 The parameters of the message to be sent can be specified in the configuration
22201 by options described below. However, these are used only when the address
22202 passed to the transport does not contain its own reply information. When the
22203 transport is run as a consequence of a
22205 or &%vacation%& command in a filter file, the parameters of the message are
22206 supplied by the filter, and passed with the address. The transport's options
22207 that define the message are then ignored (so they are not usually set in this
22208 case). The message is specified entirely by the filter or by the transport; it
22209 is never built from a mixture of options. However, the &%file_optional%&,
22210 &%mode%&, and &%return_message%& options apply in all cases.
22212 &(Autoreply)& is implemented as a local transport. When used as a result of a
22213 command in a user's filter file, &(autoreply)& normally runs under the uid and
22214 gid of the user, and with appropriate current and home directories (see chapter
22215 &<<CHAPenvironment>>&).
22217 There is a subtle difference between routing a message to a &(pipe)& transport
22218 that generates some text to be returned to the sender, and routing it to an
22219 &(autoreply)& transport. This difference is noticeable only if more than one
22220 address from the same message is so handled. In the case of a pipe, the
22221 separate outputs from the different addresses are gathered up and returned to
22222 the sender in a single message, whereas if &(autoreply)& is used, a separate
22223 message is generated for each address that is passed to it.
22225 Non-printing characters are not permitted in the header lines generated for the
22226 message that &(autoreply)& creates, with the exception of newlines that are
22227 immediately followed by white space. If any non-printing characters are found,
22228 the transport defers.
22229 Whether characters with the top bit set count as printing characters or not is
22230 controlled by the &%print_topbitchars%& global option.
22232 If any of the generic options for manipulating headers (for example,
22233 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
22234 of the original message that is included in the generated message when
22235 &%return_message%& is set. They do not apply to the generated message itself.
22237 .vindex "&$sender_address$&"
22238 If the &(autoreply)& transport receives return code 2 from Exim when it submits
22239 the message, indicating that there were no recipients, it does not treat this
22240 as an error. This means that autoreplies sent to &$sender_address$& when this
22241 is empty (because the incoming message is a bounce message) do not cause
22242 problems. They are just discarded.
22246 .section "Private options for autoreply" "SECID139"
22247 .cindex "options" "&(autoreply)& transport"
22249 .option bcc autoreply string&!! unset
22250 This specifies the addresses that are to receive &"blind carbon copies"& of the
22251 message when the message is specified by the transport.
22254 .option cc autoreply string&!! unset
22255 This specifies recipients of the message and the contents of the &'Cc:'& header
22256 when the message is specified by the transport.
22259 .option file autoreply string&!! unset
22260 The contents of the file are sent as the body of the message when the message
22261 is specified by the transport. If both &%file%& and &%text%& are set, the text
22262 string comes first.
22265 .option file_expand autoreply boolean false
22266 If this is set, the contents of the file named by the &%file%& option are
22267 subjected to string expansion as they are added to the message.
22270 .option file_optional autoreply boolean false
22271 If this option is true, no error is generated if the file named by the &%file%&
22272 option or passed with the address does not exist or cannot be read.
22275 .option from autoreply string&!! unset
22276 This specifies the contents of the &'From:'& header when the message is
22277 specified by the transport.
22280 .option headers autoreply string&!! unset
22281 This specifies additional RFC 2822 headers that are to be added to the message
22282 when the message is specified by the transport. Several can be given by using
22283 &"\n"& to separate them. There is no check on the format.
22286 .option log autoreply string&!! unset
22287 This option names a file in which a record of every message sent is logged when
22288 the message is specified by the transport.
22291 .option mode autoreply "octal integer" 0600
22292 If either the log file or the &"once"& file has to be created, this mode is
22296 .option never_mail autoreply "address list&!!" unset
22297 If any run of the transport creates a message with a recipient that matches any
22298 item in the list, that recipient is quietly discarded. If all recipients are
22299 discarded, no message is created. This applies both when the recipients are
22300 generated by a filter and when they are specified in the transport.
22304 .option once autoreply string&!! unset
22305 This option names a file or DBM database in which a record of each &'To:'&
22306 recipient is kept when the message is specified by the transport. &*Note*&:
22307 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
22309 If &%once%& is unset, or is set to an empty string, the message is always sent.
22310 By default, if &%once%& is set to a non-empty file name, the message
22311 is not sent if a potential recipient is already listed in the database.
22312 However, if the &%once_repeat%& option specifies a time greater than zero, the
22313 message is sent if that much time has elapsed since a message was last sent to
22314 this recipient. A setting of zero time for &%once_repeat%& (the default)
22315 prevents a message from being sent a second time &-- in this case, zero means
22318 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
22319 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
22320 greater than zero, it changes the way Exim implements the &%once%& option.
22321 Instead of using a DBM file to record every recipient it sends to, it uses a
22322 regular file, whose size will never get larger than the given value.
22324 In the file, Exim keeps a linear list of recipient addresses and the times at
22325 which they were sent messages. If the file is full when a new address needs to
22326 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
22327 means that a given recipient may receive multiple messages, but at
22328 unpredictable intervals that depend on the rate of turnover of addresses in the
22329 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
22332 .option once_file_size autoreply integer 0
22333 See &%once%& above.
22336 .option once_repeat autoreply time&!! 0s
22337 See &%once%& above.
22338 After expansion, the value of this option must be a valid time value.
22341 .option reply_to autoreply string&!! unset
22342 This specifies the contents of the &'Reply-To:'& header when the message is
22343 specified by the transport.
22346 .option return_message autoreply boolean false
22347 If this is set, a copy of the original message is returned with the new
22348 message, subject to the maximum size set in the &%return_size_limit%& global
22349 configuration option.
22352 .option subject autoreply string&!! unset
22353 This specifies the contents of the &'Subject:'& header when the message is
22354 specified by the transport. It is tempting to quote the original subject in
22355 automatic responses. For example:
22357 subject = Re: $h_subject:
22359 There is a danger in doing this, however. It may allow a third party to
22360 subscribe your users to an opt-in mailing list, provided that the list accepts
22361 bounce messages as subscription confirmations. Well-managed lists require a
22362 non-bounce message to confirm a subscription, so the danger is relatively
22367 .option text autoreply string&!! unset
22368 This specifies a single string to be used as the body of the message when the
22369 message is specified by the transport. If both &%text%& and &%file%& are set,
22370 the text comes first.
22373 .option to autoreply string&!! unset
22374 This specifies recipients of the message and the contents of the &'To:'& header
22375 when the message is specified by the transport.
22376 .ecindex IIDauttra1
22377 .ecindex IIDauttra2
22382 . ////////////////////////////////////////////////////////////////////////////
22383 . ////////////////////////////////////////////////////////////////////////////
22385 .chapter "The lmtp transport" "CHAPLMTP"
22386 .cindex "transports" "&(lmtp)&"
22387 .cindex "&(lmtp)& transport"
22388 .cindex "LMTP" "over a pipe"
22389 .cindex "LMTP" "over a socket"
22390 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
22392 or by interacting with a Unix domain socket.
22393 This transport is something of a cross between the &(pipe)& and &(smtp)&
22394 transports. Exim also has support for using LMTP over TCP/IP; this is
22395 implemented as an option for the &(smtp)& transport. Because LMTP is expected
22396 to be of minority interest, the default build-time configure in &_src/EDITME_&
22397 has it commented out. You need to ensure that
22401 .cindex "options" "&(lmtp)& transport"
22402 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
22403 included in the Exim binary. The private options of the &(lmtp)& transport are
22406 .option batch_id lmtp string&!! unset
22407 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22410 .option batch_max lmtp integer 1
22411 This limits the number of addresses that can be handled in a single delivery.
22412 Most LMTP servers can handle several addresses at once, so it is normally a
22413 good idea to increase this value. See the description of local delivery
22414 batching in chapter &<<CHAPbatching>>&.
22417 .option command lmtp string&!! unset
22418 This option must be set if &%socket%& is not set. The string is a command which
22419 is run in a separate process. It is split up into a command name and list of
22420 arguments, each of which is separately expanded (so expansion cannot change the
22421 number of arguments). The command is run directly, not via a shell. The message
22422 is passed to the new process using the standard input and output to operate the
22425 .option ignore_quota lmtp boolean false
22426 .cindex "LMTP" "ignoring quota errors"
22427 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
22428 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
22429 in its response to the LHLO command.
22431 .option socket lmtp string&!! unset
22432 This option must be set if &%command%& is not set. The result of expansion must
22433 be the name of a Unix domain socket. The transport connects to the socket and
22434 delivers the message to it using the LMTP protocol.
22437 .option timeout lmtp time 5m
22438 The transport is aborted if the created process or Unix domain socket does not
22439 respond to LMTP commands or message input within this timeout. Delivery
22440 is deferred, and will be tried again later. Here is an example of a typical
22445 command = /some/local/lmtp/delivery/program
22449 This delivers up to 20 addresses at a time, in a mixture of domains if
22450 necessary, running as the user &'exim'&.
22454 . ////////////////////////////////////////////////////////////////////////////
22455 . ////////////////////////////////////////////////////////////////////////////
22457 .chapter "The pipe transport" "CHAPpipetransport"
22458 .scindex IIDpiptra1 "transports" "&(pipe)&"
22459 .scindex IIDpiptra2 "&(pipe)& transport"
22460 The &(pipe)& transport is used to deliver messages via a pipe to a command
22461 running in another process. One example is the use of &(pipe)& as a
22462 pseudo-remote transport for passing messages to some other delivery mechanism
22463 (such as UUCP). Another is the use by individual users to automatically process
22464 their incoming messages. The &(pipe)& transport can be used in one of the
22468 .vindex "&$local_part$&"
22469 A router routes one address to a transport in the normal way, and the
22470 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
22471 contains the local part of the address (as usual), and the command that is run
22472 is specified by the &%command%& option on the transport.
22474 .vindex "&$pipe_addresses$&"
22475 If the &%batch_max%& option is set greater than 1 (the default is 1), the
22476 transport can handle more than one address in a single run. In this case, when
22477 more than one address is routed to the transport, &$local_part$& is not set
22478 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
22479 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
22480 that are routed to the transport.
22482 .vindex "&$address_pipe$&"
22483 A router redirects an address directly to a pipe command (for example, from an
22484 alias or forward file). In this case, &$address_pipe$& contains the text of the
22485 pipe command, and the &%command%& option on the transport is ignored unless
22486 &%force_command%& is set. If only one address is being transported
22487 (&%batch_max%& is not greater than one, or only one address was redirected to
22488 this pipe command), &$local_part$& contains the local part that was redirected.
22492 The &(pipe)& transport is a non-interactive delivery method. Exim can also
22493 deliver messages over pipes using the LMTP interactive protocol. This is
22494 implemented by the &(lmtp)& transport.
22496 In the case when &(pipe)& is run as a consequence of an entry in a local user's
22497 &_.forward_& file, the command runs under the uid and gid of that user. In
22498 other cases, the uid and gid have to be specified explicitly, either on the
22499 transport or on the router that handles the address. Current and &"home"&
22500 directories are also controllable. See chapter &<<CHAPenvironment>>& for
22501 details of the local delivery environment and chapter &<<CHAPbatching>>&
22502 for a discussion of local delivery batching.
22505 .section "Concurrent delivery" "SECID140"
22506 If two messages arrive at almost the same time, and both are routed to a pipe
22507 delivery, the two pipe transports may be run concurrently. You must ensure that
22508 any pipe commands you set up are robust against this happening. If the commands
22509 write to a file, the &%exim_lock%& utility might be of use.
22511 Alternatively the &%max_parallel%& option could be used with a value
22512 of "1" to enforce serialization.
22518 .section "Returned status and data" "SECID141"
22519 .cindex "&(pipe)& transport" "returned data"
22520 If the command exits with a non-zero return code, the delivery is deemed to
22521 have failed, unless either the &%ignore_status%& option is set (in which case
22522 the return code is treated as zero), or the return code is one of those listed
22523 in the &%temp_errors%& option, which are interpreted as meaning &"try again
22524 later"&. In this case, delivery is deferred. Details of a permanent failure are
22525 logged, but are not included in the bounce message, which merely contains
22526 &"local delivery failed"&.
22528 If the command exits on a signal and the &%freeze_signal%& option is set then
22529 the message will be frozen in the queue. If that option is not set, a bounce
22530 will be sent as normal.
22532 If the return code is greater than 128 and the command being run is a shell
22533 script, it normally means that the script was terminated by a signal whose
22534 value is the return code minus 128. The &%freeze_signal%& option does not
22535 apply in this case.
22537 If Exim is unable to run the command (that is, if &[execve()]& fails), the
22538 return code is set to 127. This is the value that a shell returns if it is
22539 asked to run a non-existent command. The wording for the log line suggests that
22540 a non-existent command may be the problem.
22542 The &%return_output%& option can affect the result of a pipe delivery. If it is
22543 set and the command produces any output on its standard output or standard
22544 error streams, the command is considered to have failed, even if it gave a zero
22545 return code or if &%ignore_status%& is set. The output from the command is
22546 included as part of the bounce message. The &%return_fail_output%& option is
22547 similar, except that output is returned only when the command exits with a
22548 failure return code, that is, a value other than zero or a code that matches
22553 .section "How the command is run" "SECThowcommandrun"
22554 .cindex "&(pipe)& transport" "path for command"
22555 The command line is (by default) broken down into a command name and arguments
22556 by the &(pipe)& transport itself. The &%allow_commands%& and
22557 &%restrict_to_path%& options can be used to restrict the commands that may be
22560 .cindex "quoting" "in pipe command"
22561 Unquoted arguments are delimited by white space. If an argument appears in
22562 double quotes, backslash is interpreted as an escape character in the usual
22563 way. If an argument appears in single quotes, no escaping is done.
22565 String expansion is applied to the command line except when it comes from a
22566 traditional &_.forward_& file (commands from a filter file are expanded). The
22567 expansion is applied to each argument in turn rather than to the whole line.
22568 For this reason, any string expansion item that contains white space must be
22569 quoted so as to be contained within a single argument. A setting such as
22571 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
22573 will not work, because the expansion item gets split between several
22574 arguments. You have to write
22576 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
22578 to ensure that it is all in one argument. The expansion is done in this way,
22579 argument by argument, so that the number of arguments cannot be changed as a
22580 result of expansion, and quotes or backslashes in inserted variables do not
22581 interact with external quoting. However, this leads to problems if you want to
22582 generate multiple arguments (or the command name plus arguments) from a single
22583 expansion. In this situation, the simplest solution is to use a shell. For
22586 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
22589 .cindex "transport" "filter"
22590 .cindex "filter" "transport filter"
22591 .vindex "&$pipe_addresses$&"
22592 Special handling takes place when an argument consists of precisely the text
22593 &`$pipe_addresses`&. This is not a general expansion variable; the only
22594 place this string is recognized is when it appears as an argument for a pipe or
22595 transport filter command. It causes each address that is being handled to be
22596 inserted in the argument list at that point &'as a separate argument'&. This
22597 avoids any problems with spaces or shell metacharacters, and is of use when a
22598 &(pipe)& transport is handling groups of addresses in a batch.
22600 If &%force_command%& is enabled on the transport, Special handling takes place
22601 for an argument that consists of precisely the text &`$address_pipe`&. It
22602 is handled similarly to &$pipe_addresses$& above. It is expanded and each
22603 argument is inserted in the argument list at that point
22604 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
22605 the only item in the argument; in fact, if it were then &%force_command%&
22606 should behave as a no-op. Rather, it should be used to adjust the command
22607 run while preserving the argument vector separation.
22609 After splitting up into arguments and expansion, the resulting command is run
22610 in a subprocess directly from the transport, &'not'& under a shell. The
22611 message that is being delivered is supplied on the standard input, and the
22612 standard output and standard error are both connected to a single pipe that is
22613 read by Exim. The &%max_output%& option controls how much output the command
22614 may produce, and the &%return_output%& and &%return_fail_output%& options
22615 control what is done with it.
22617 Not running the command under a shell (by default) lessens the security risks
22618 in cases when a command from a user's filter file is built out of data that was
22619 taken from an incoming message. If a shell is required, it can of course be
22620 explicitly specified as the command to be run. However, there are circumstances
22621 where existing commands (for example, in &_.forward_& files) expect to be run
22622 under a shell and cannot easily be modified. To allow for these cases, there is
22623 an option called &%use_shell%&, which changes the way the &(pipe)& transport
22624 works. Instead of breaking up the command line as just described, it expands it
22625 as a single string and passes the result to &_/bin/sh_&. The
22626 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
22627 with &%use_shell%&, and the whole mechanism is inherently less secure.
22631 .section "Environment variables" "SECTpipeenv"
22632 .cindex "&(pipe)& transport" "environment for command"
22633 .cindex "environment for pipe transport"
22634 The environment variables listed below are set up when the command is invoked.
22635 This list is a compromise for maximum compatibility with other MTAs. Note that
22636 the &%environment%& option can be used to add additional variables to this
22639 &`DOMAIN `& the domain of the address
22640 &`HOME `& the home directory, if set
22641 &`HOST `& the host name when called from a router (see below)
22642 &`LOCAL_PART `& see below
22643 &`LOCAL_PART_PREFIX `& see below
22644 &`LOCAL_PART_SUFFIX `& see below
22645 &`LOGNAME `& see below
22646 &`MESSAGE_ID `& Exim's local ID for the message
22647 &`PATH `& as specified by the &%path%& option below
22648 &`QUALIFY_DOMAIN `& the sender qualification domain
22649 &`RECIPIENT `& the complete recipient address
22650 &`SENDER `& the sender of the message (empty if a bounce)
22651 &`SHELL `& &`/bin/sh`&
22652 &`TZ `& the value of the &%timezone%& option, if set
22653 &`USER `& see below
22655 When a &(pipe)& transport is called directly from (for example) an &(accept)&
22656 router, LOCAL_PART is set to the local part of the address. When it is
22657 called as a result of a forward or alias expansion, LOCAL_PART is set to
22658 the local part of the address that was expanded. In both cases, any affixes are
22659 removed from the local part, and made available in LOCAL_PART_PREFIX and
22660 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
22661 same value as LOCAL_PART for compatibility with other MTAs.
22664 HOST is set only when a &(pipe)& transport is called from a router that
22665 associates hosts with an address, typically when using &(pipe)& as a
22666 pseudo-remote transport. HOST is set to the first host name specified by
22670 If the transport's generic &%home_directory%& option is set, its value is used
22671 for the HOME environment variable. Otherwise, a home directory may be set
22672 by the router's &%transport_home_directory%& option, which defaults to the
22673 user's home directory if &%check_local_user%& is set.
22676 .section "Private options for pipe" "SECID142"
22677 .cindex "options" "&(pipe)& transport"
22681 .option allow_commands pipe "string list&!!" unset
22682 .cindex "&(pipe)& transport" "permitted commands"
22683 The string is expanded, and is then interpreted as a colon-separated list of
22684 permitted commands. If &%restrict_to_path%& is not set, the only commands
22685 permitted are those in the &%allow_commands%& list. They need not be absolute
22686 paths; the &%path%& option is still used for relative paths. If
22687 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
22688 in the &%allow_commands%& list, or a name without any slashes that is found on
22689 the path. In other words, if neither &%allow_commands%& nor
22690 &%restrict_to_path%& is set, there is no restriction on the command, but
22691 otherwise only commands that are permitted by one or the other are allowed. For
22694 allow_commands = /usr/bin/vacation
22696 and &%restrict_to_path%& is not set, the only permitted command is
22697 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
22698 &%use_shell%& is set.
22701 .option batch_id pipe string&!! unset
22702 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22705 .option batch_max pipe integer 1
22706 This limits the number of addresses that can be handled in a single delivery.
22707 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22710 .option check_string pipe string unset
22711 As &(pipe)& writes the message, the start of each line is tested for matching
22712 &%check_string%&, and if it does, the initial matching characters are replaced
22713 by the contents of &%escape_string%&, provided both are set. The value of
22714 &%check_string%& is a literal string, not a regular expression, and the case of
22715 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
22716 of &%check_string%& and &%escape_string%& are forced to values that implement
22717 the SMTP escaping protocol. Any settings made in the configuration file are
22721 .option command pipe string&!! unset
22722 This option need not be set when &(pipe)& is being used to deliver to pipes
22723 obtained directly from address redirections. In other cases, the option must be
22724 set, to provide a command to be run. It need not yield an absolute path (see
22725 the &%path%& option below). The command is split up into separate arguments by
22726 Exim, and each argument is separately expanded, as described in section
22727 &<<SECThowcommandrun>>& above.
22730 .option environment pipe string&!! unset
22731 .cindex "&(pipe)& transport" "environment for command"
22732 .cindex "environment for &(pipe)& transport"
22733 This option is used to add additional variables to the environment in which the
22734 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
22735 a string which is expanded, and then interpreted as a colon-separated list of
22736 environment settings of the form <&'name'&>=<&'value'&>.
22739 .option escape_string pipe string unset
22740 See &%check_string%& above.
22743 .option freeze_exec_fail pipe boolean false
22744 .cindex "exec failure"
22745 .cindex "failure of exec"
22746 .cindex "&(pipe)& transport" "failure of exec"
22747 Failure to exec the command in a pipe transport is by default treated like
22748 any other failure while running the command. However, if &%freeze_exec_fail%&
22749 is set, failure to exec is treated specially, and causes the message to be
22750 frozen, whatever the setting of &%ignore_status%&.
22753 .option freeze_signal pipe boolean false
22754 .cindex "signal exit"
22755 .cindex "&(pipe)& transport", "signal exit"
22756 Normally if the process run by a command in a pipe transport exits on a signal,
22757 a bounce message is sent. If &%freeze_signal%& is set, the message will be
22758 frozen in Exim's queue instead.
22761 .option force_command pipe boolean false
22762 .cindex "force command"
22763 .cindex "&(pipe)& transport", "force command"
22764 Normally when a router redirects an address directly to a pipe command
22765 the &%command%& option on the transport is ignored. If &%force_command%&
22766 is set, the &%command%& option will used. This is especially
22767 useful for forcing a wrapper or additional argument to be added to the
22768 command. For example:
22770 command = /usr/bin/remote_exec myhost -- $address_pipe
22774 Note that &$address_pipe$& is handled specially in &%command%& when
22775 &%force_command%& is set, expanding out to the original argument vector as
22776 separate items, similarly to a Unix shell &`"$@"`& construct.
22779 .option ignore_status pipe boolean false
22780 If this option is true, the status returned by the subprocess that is set up to
22781 run the command is ignored, and Exim behaves as if zero had been returned.
22782 Otherwise, a non-zero status or termination by signal causes an error return
22783 from the transport unless the status value is one of those listed in
22784 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
22786 &*Note*&: This option does not apply to timeouts, which do not return a status.
22787 See the &%timeout_defer%& option for how timeouts are handled.
22790 .option log_defer_output pipe boolean false
22791 .cindex "&(pipe)& transport" "logging output"
22792 If this option is set, and the status returned by the command is
22793 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
22794 and any output was produced on stdout or stderr, the first line of it is
22795 written to the main log.
22798 .option log_fail_output pipe boolean false
22799 If this option is set, and the command returns any output on stdout or
22800 stderr, and also ends with a return code that is neither zero nor one of
22801 the return codes listed in &%temp_errors%& (that is, the delivery
22802 failed), the first line of output is written to the main log. This
22803 option and &%log_output%& are mutually exclusive. Only one of them may
22807 .option log_output pipe boolean false
22808 If this option is set and the command returns any output on stdout or
22809 stderr, the first line of output is written to the main log, whatever
22810 the return code. This option and &%log_fail_output%& are mutually
22811 exclusive. Only one of them may be set.
22814 .option max_output pipe integer 20K
22815 This specifies the maximum amount of output that the command may produce on its
22816 standard output and standard error file combined. If the limit is exceeded, the
22817 process running the command is killed. This is intended as a safety measure to
22818 catch runaway processes. The limit is applied independently of the settings of
22819 the options that control what is done with such output (for example,
22820 &%return_output%&). Because of buffering effects, the amount of output may
22821 exceed the limit by a small amount before Exim notices.
22824 .option message_prefix pipe string&!! "see below"
22825 The string specified here is expanded and output at the start of every message.
22826 The default is unset if &%use_bsmtp%& is set. Otherwise it is
22829 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
22833 .cindex "&%tmail%&"
22834 .cindex "&""From""& line"
22835 This is required by the commonly used &_/usr/bin/vacation_& program.
22836 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
22837 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
22842 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
22843 &`\n`& to &`\r\n`& in &%message_prefix%&.
22846 .option message_suffix pipe string&!! "see below"
22847 The string specified here is expanded and output at the end of every message.
22848 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
22849 The suffix can be suppressed by setting
22853 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
22854 &`\n`& to &`\r\n`& in &%message_suffix%&.
22857 .option path pipe string "see below"
22858 This option specifies the string that is set up in the PATH environment
22859 variable of the subprocess. The default is:
22863 If the &%command%& option does not yield an absolute path name, the command is
22864 sought in the PATH directories, in the usual way. &*Warning*&: This does not
22865 apply to a command specified as a transport filter.
22868 .option permit_coredump pipe boolean false
22869 Normally Exim inhibits core-dumps during delivery. If you have a need to get
22870 a core-dump of a pipe command, enable this command. This enables core-dumps
22871 during delivery and affects both the Exim binary and the pipe command run.
22872 It is recommended that this option remain off unless and until you have a need
22873 for it and that this only be enabled when needed, as the risk of excessive
22874 resource consumption can be quite high. Note also that Exim is typically
22875 installed as a setuid binary and most operating systems will inhibit coredumps
22876 of these by default, so further OS-specific action may be required.
22879 .option pipe_as_creator pipe boolean false
22880 .cindex "uid (user id)" "local delivery"
22881 If the generic &%user%& option is not set and this option is true, the delivery
22882 process is run under the uid that was in force when Exim was originally called
22883 to accept the message. If the group id is not otherwise set (via the generic
22884 &%group%& option), the gid that was in force when Exim was originally called to
22885 accept the message is used.
22888 .option restrict_to_path pipe boolean false
22889 When this option is set, any command name not listed in &%allow_commands%& must
22890 contain no slashes. The command is searched for only in the directories listed
22891 in the &%path%& option. This option is intended for use in the case when a pipe
22892 command has been generated from a user's &_.forward_& file. This is usually
22893 handled by a &(pipe)& transport called &%address_pipe%&.
22896 .option return_fail_output pipe boolean false
22897 If this option is true, and the command produced any output and ended with a
22898 return code other than zero or one of the codes listed in &%temp_errors%& (that
22899 is, the delivery failed), the output is returned in the bounce message.
22900 However, if the message has a null sender (that is, it is itself a bounce
22901 message), output from the command is discarded. This option and
22902 &%return_output%& are mutually exclusive. Only one of them may be set.
22906 .option return_output pipe boolean false
22907 If this option is true, and the command produced any output, the delivery is
22908 deemed to have failed whatever the return code from the command, and the output
22909 is returned in the bounce message. Otherwise, the output is just discarded.
22910 However, if the message has a null sender (that is, it is a bounce message),
22911 output from the command is always discarded, whatever the setting of this
22912 option. This option and &%return_fail_output%& are mutually exclusive. Only one
22913 of them may be set.
22917 .option temp_errors pipe "string list" "see below"
22918 .cindex "&(pipe)& transport" "temporary failure"
22919 This option contains either a colon-separated list of numbers, or a single
22920 asterisk. If &%ignore_status%& is false
22921 and &%return_output%& is not set,
22922 and the command exits with a non-zero return code, the failure is treated as
22923 temporary and the delivery is deferred if the return code matches one of the
22924 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
22925 codes are treated as permanent errors. The default setting contains the codes
22926 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
22927 compiled on a system that does not define these macros, it assumes values of 75
22928 and 73, respectively.
22931 .option timeout pipe time 1h
22932 If the command fails to complete within this time, it is killed. This normally
22933 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
22934 specifies no timeout. In order to ensure that any subprocesses created by the
22935 command are also killed, Exim makes the initial process a process group leader,
22936 and kills the whole process group on a timeout. However, this can be defeated
22937 if one of the processes starts a new process group.
22939 .option timeout_defer pipe boolean false
22940 A timeout in a &(pipe)& transport, either in the command that the transport
22941 runs, or in a transport filter that is associated with it, is by default
22942 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
22943 is set true, both kinds of timeout become temporary errors, causing the
22944 delivery to be deferred.
22946 .option umask pipe "octal integer" 022
22947 This specifies the umask setting for the subprocess that runs the command.
22950 .option use_bsmtp pipe boolean false
22951 .cindex "envelope sender"
22952 If this option is set true, the &(pipe)& transport writes messages in &"batch
22953 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
22954 commands. If you want to include a leading HELO command with such messages,
22955 you can do so by setting the &%message_prefix%& option. See section
22956 &<<SECTbatchSMTP>>& for details of batch SMTP.
22958 .option use_classresources pipe boolean false
22959 .cindex "class resources (BSD)"
22960 This option is available only when Exim is running on FreeBSD, NetBSD, or
22961 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
22962 resource limits when a &(pipe)& transport is run to perform a delivery. The
22963 limits for the uid under which the pipe is to run are obtained from the login
22967 .option use_crlf pipe boolean false
22968 .cindex "carriage return"
22970 This option causes lines to be terminated with the two-character CRLF sequence
22971 (carriage return, linefeed) instead of just a linefeed character. In the case
22972 of batched SMTP, the byte sequence written to the pipe is then an exact image
22973 of what would be sent down a real SMTP connection.
22975 The contents of the &%message_prefix%& and &%message_suffix%& options are
22976 written verbatim, so must contain their own carriage return characters if these
22977 are needed. When &%use_bsmtp%& is not set, the default values for both
22978 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
22979 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
22982 .option use_shell pipe boolean false
22983 .vindex "&$pipe_addresses$&"
22984 If this option is set, it causes the command to be passed to &_/bin/sh_&
22985 instead of being run directly from the transport, as described in section
22986 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
22987 where the command is expected to be run under a shell and cannot easily be
22988 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
22989 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
22990 command is expanded as a single string, and handed to &_/bin/sh_& as data for
22995 .section "Using an external local delivery agent" "SECID143"
22996 .cindex "local delivery" "using an external agent"
22997 .cindex "&'procmail'&"
22998 .cindex "external local delivery"
22999 .cindex "delivery" "&'procmail'&"
23000 .cindex "delivery" "by external agent"
23001 The &(pipe)& transport can be used to pass all messages that require local
23002 delivery to a separate local delivery agent such as &%procmail%&. When doing
23003 this, care must be taken to ensure that the pipe is run under an appropriate
23004 uid and gid. In some configurations one wants this to be a uid that is trusted
23005 by the delivery agent to supply the correct sender of the message. It may be
23006 necessary to recompile or reconfigure the delivery agent so that it trusts an
23007 appropriate user. The following is an example transport and router
23008 configuration for &%procmail%&:
23013 command = /usr/local/bin/procmail -d $local_part
23017 check_string = "From "
23018 escape_string = ">From "
23027 transport = procmail_pipe
23029 In this example, the pipe is run as the local user, but with the group set to
23030 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
23031 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
23032 user to supply a correct sender address. If you do not specify either a
23033 &%group%& or a &%user%& option, the pipe command is run as the local user. The
23034 home directory is the user's home directory by default.
23036 &*Note*&: The command that the pipe transport runs does &'not'& begin with
23040 as shown in some &%procmail%& documentation, because Exim does not by default
23041 use a shell to run pipe commands.
23044 The next example shows a transport and a router for a system where local
23045 deliveries are handled by the Cyrus IMAP server.
23048 local_delivery_cyrus:
23050 command = /usr/cyrus/bin/deliver \
23051 -m ${substr_1:$local_part_suffix} -- $local_part
23063 local_part_suffix = .*
23064 transport = local_delivery_cyrus
23066 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
23067 &%return_output%& to cause any text written by Cyrus to be returned to the
23069 .ecindex IIDpiptra1
23070 .ecindex IIDpiptra2
23073 . ////////////////////////////////////////////////////////////////////////////
23074 . ////////////////////////////////////////////////////////////////////////////
23076 .chapter "The smtp transport" "CHAPsmtptrans"
23077 .scindex IIDsmttra1 "transports" "&(smtp)&"
23078 .scindex IIDsmttra2 "&(smtp)& transport"
23079 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
23080 or LMTP protocol. The list of hosts to try can either be taken from the address
23081 that is being processed (having been set up by the router), or specified
23082 explicitly for the transport. Timeout and retry processing (see chapter
23083 &<<CHAPretry>>&) is applied to each IP address independently.
23086 .section "Multiple messages on a single connection" "SECID144"
23087 The sending of multiple messages over a single TCP/IP connection can arise in
23091 If a message contains more than &%max_rcpt%& (see below) addresses that are
23092 routed to the same host, more than one copy of the message has to be sent to
23093 that host. In this situation, multiple copies may be sent in a single run of
23094 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
23095 does when it has too many addresses to send in one message also depends on the
23096 value of the global &%remote_max_parallel%& option. Details are given in
23097 section &<<SECToutSMTPTCP>>&.)
23099 .cindex "hints database" "remembering routing"
23100 When a message has been successfully delivered over a TCP/IP connection, Exim
23101 looks in its hints database to see if there are any other messages awaiting a
23102 connection to the same host. If there are, a new delivery process is started
23103 for one of them, and the current TCP/IP connection is passed on to it. The new
23104 process may in turn send multiple copies and possibly create yet another
23109 For each copy sent over the same TCP/IP connection, a sequence counter is
23110 incremented, and if it ever gets to the value of &%connection_max_messages%&,
23111 no further messages are sent over that connection.
23115 .section "Use of the $host and $host_address variables" "SECID145"
23117 .vindex "&$host_address$&"
23118 At the start of a run of the &(smtp)& transport, the values of &$host$& and
23119 &$host_address$& are the name and IP address of the first host on the host list
23120 passed by the router. However, when the transport is about to connect to a
23121 specific host, and while it is connected to that host, &$host$& and
23122 &$host_address$& are set to the values for that host. These are the values
23123 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
23124 &%serialize_hosts%&, and the various TLS options are expanded.
23127 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
23128 .vindex &$tls_bits$&
23129 .vindex &$tls_cipher$&
23130 .vindex &$tls_peerdn$&
23131 .vindex &$tls_sni$&
23132 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
23133 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
23134 are the values that were set when the message was received.
23135 These are the values that are used for options that are expanded before any
23136 SMTP connections are made. Just before each connection is made, these four
23137 variables are emptied. If TLS is subsequently started, they are set to the
23138 appropriate values for the outgoing connection, and these are the values that
23139 are in force when any authenticators are run and when the
23140 &%authenticated_sender%& option is expanded.
23142 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
23143 and will be removed in a future release.
23146 .section "Private options for smtp" "SECID146"
23147 .cindex "options" "&(smtp)& transport"
23148 The private options of the &(smtp)& transport are as follows:
23151 .option address_retry_include_sender smtp boolean true
23152 .cindex "4&'xx'& responses" "retrying after"
23153 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
23154 is the combination of sender and recipient that is delayed in subsequent queue
23155 runs until the retry time is reached. You can delay the recipient without
23156 reference to the sender (which is what earlier versions of Exim did), by
23157 setting &%address_retry_include_sender%& false. However, this can lead to
23158 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
23160 .option allow_localhost smtp boolean false
23161 .cindex "local host" "sending to"
23162 .cindex "fallback" "hosts specified on transport"
23163 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
23164 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
23165 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
23166 the delivery anyway. This should be used only in special cases when the
23167 configuration ensures that no looping will result (for example, a differently
23168 configured Exim is listening on the port to which the message is sent).
23171 .option authenticated_sender smtp string&!! unset
23173 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
23174 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
23175 overriding any existing authenticated sender value. If the string expansion is
23176 forced to fail, the option is ignored. Other expansion failures cause delivery
23177 to be deferred. If the result of expansion is an empty string, that is also
23180 The expansion happens after the outgoing connection has been made and TLS
23181 started, if required. This means that the &$host$&, &$host_address$&,
23182 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
23183 particular connection.
23185 If the SMTP session is not authenticated, the expansion of
23186 &%authenticated_sender%& still happens (and can cause the delivery to be
23187 deferred if it fails), but no AUTH= item is added to MAIL commands
23188 unless &%authenticated_sender_force%& is true.
23190 This option allows you to use the &(smtp)& transport in LMTP mode to
23191 deliver mail to Cyrus IMAP and provide the proper local part as the
23192 &"authenticated sender"&, via a setting such as:
23194 authenticated_sender = $local_part
23196 This removes the need for IMAP subfolders to be assigned special ACLs to
23197 allow direct delivery to those subfolders.
23199 Because of expected uses such as that just described for Cyrus (when no
23200 domain is involved), there is no checking on the syntax of the provided
23204 .option authenticated_sender_force smtp boolean false
23205 If this option is set true, the &%authenticated_sender%& option's value
23206 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
23207 authenticated as a client.
23210 .option command_timeout smtp time 5m
23211 This sets a timeout for receiving a response to an SMTP command that has been
23212 sent out. It is also used when waiting for the initial banner line from the
23213 remote host. Its value must not be zero.
23216 .option connect_timeout smtp time 5m
23217 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
23218 to a remote host. A setting of zero allows the system timeout (typically
23219 several minutes) to act. To have any effect, the value of this option must be
23220 less than the system timeout. However, it has been observed that on some
23221 systems there is no system timeout, which is why the default value for this
23222 option is 5 minutes, a value recommended by RFC 1123.
23225 .option connection_max_messages smtp integer 500
23226 .cindex "SMTP" "passed connection"
23227 .cindex "SMTP" "multiple deliveries"
23228 .cindex "multiple SMTP deliveries"
23229 This controls the maximum number of separate message deliveries that are sent
23230 over a single TCP/IP connection. If the value is zero, there is no limit.
23231 For testing purposes, this value can be overridden by the &%-oB%& command line
23235 .option data_timeout smtp time 5m
23236 This sets a timeout for the transmission of each block in the data portion of
23237 the message. As a result, the overall timeout for a message depends on the size
23238 of the message. Its value must not be zero. See also &%final_timeout%&.
23241 .option delay_after_cutoff smtp boolean true
23242 This option controls what happens when all remote IP addresses for a given
23243 domain have been inaccessible for so long that they have passed their retry
23246 In the default state, if the next retry time has not been reached for any of
23247 them, the address is bounced without trying any deliveries. In other words,
23248 Exim delays retrying an IP address after the final cutoff time until a new
23249 retry time is reached, and can therefore bounce an address without ever trying
23250 a delivery, when machines have been down for a long time. Some people are
23251 unhappy at this prospect, so...
23253 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
23254 addresses are past their final cutoff time, Exim tries to deliver to those
23255 IP addresses that have not been tried since the message arrived. If there are
23256 none, of if they all fail, the address is bounced. In other words, it does not
23257 delay when a new message arrives, but immediately tries those expired IP
23258 addresses that haven't been tried since the message arrived. If there is a
23259 continuous stream of messages for the dead hosts, unsetting
23260 &%delay_after_cutoff%& means that there will be many more attempts to deliver
23264 .option dns_qualify_single smtp boolean true
23265 If the &%hosts%& or &%fallback_hosts%& option is being used,
23266 and the &%gethostbyname%& option is false,
23267 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
23268 in chapter &<<CHAPdnslookup>>& for more details.
23271 .option dns_search_parents smtp boolean false
23272 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
23273 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
23274 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
23278 .option dnssec_request_domains smtp "domain list&!!" unset
23279 .cindex "MX record" "security"
23280 .cindex "DNSSEC" "MX lookup"
23281 .cindex "security" "MX lookup"
23282 .cindex "DNS" "DNSSEC"
23283 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
23284 the dnssec request bit set.
23285 This applies to all of the SRV, MX, AAAA, A lookup sequence.
23289 .option dnssec_require_domains smtp "domain list&!!" unset
23290 .cindex "MX record" "security"
23291 .cindex "DNSSEC" "MX lookup"
23292 .cindex "security" "MX lookup"
23293 .cindex "DNS" "DNSSEC"
23294 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
23295 the dnssec request bit set. Any returns not having the Authenticated Data bit
23296 (AD bit) set will be ignored and logged as a host-lookup failure.
23297 This applies to all of the SRV, MX, AAAA, A lookup sequence.
23301 .option dscp smtp string&!! unset
23302 .cindex "DCSP" "outbound"
23303 This option causes the DSCP value associated with a socket to be set to one
23304 of a number of fixed strings or to numeric value.
23305 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
23306 Common values include &`throughput`&, &`mincost`&, and on newer systems
23307 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
23309 The outbound packets from Exim will be marked with this value in the header
23310 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
23311 that these values will have any effect, not be stripped by networking
23312 equipment, or do much of anything without cooperation with your Network
23313 Engineer and those of all network operators between the source and destination.
23316 .option fallback_hosts smtp "string list" unset
23317 .cindex "fallback" "hosts specified on transport"
23318 String expansion is not applied to this option. The argument must be a
23319 colon-separated list of host names or IP addresses, optionally also including
23320 port numbers, though the separator can be changed, as described in section
23321 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
23322 item in a &%route_list%& setting for the &(manualroute)& router, as described
23323 in section &<<SECTformatonehostitem>>&.
23325 Fallback hosts can also be specified on routers, which associate them with the
23326 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
23327 &%fallback_hosts%& specified on the transport is used only if the address does
23328 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
23329 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
23330 However, &%hosts_randomize%& does apply to fallback host lists.
23332 If Exim is unable to deliver to any of the hosts for a particular address, and
23333 the errors are not permanent rejections, the address is put on a separate
23334 transport queue with its host list replaced by the fallback hosts, unless the
23335 address was routed via MX records and the current host was in the original MX
23336 list. In that situation, the fallback host list is not used.
23338 Once normal deliveries are complete, the fallback queue is delivered by
23339 re-running the same transports with the new host lists. If several failing
23340 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
23341 copy of the message is sent.
23343 The resolution of the host names on the fallback list is controlled by the
23344 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
23345 both to cases when the host list comes with the address and when it is taken
23346 from &%hosts%&. This option provides a &"use a smart host only if delivery
23350 .option final_timeout smtp time 10m
23351 This is the timeout that applies while waiting for the response to the final
23352 line containing just &"."& that terminates a message. Its value must not be
23355 .option gethostbyname smtp boolean false
23356 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
23357 being used, names are looked up using &[gethostbyname()]&
23358 (or &[getipnodebyname()]& when available)
23359 instead of using the DNS. Of course, that function may in fact use the DNS, but
23360 it may also consult other sources of information such as &_/etc/hosts_&.
23362 .option gnutls_compat_mode smtp boolean unset
23363 This option controls whether GnuTLS is used in compatibility mode in an Exim
23364 server. This reduces security slightly, but improves interworking with older
23365 implementations of TLS.
23367 .option helo_data smtp string&!! "see below"
23368 .cindex "HELO" "argument, setting"
23369 .cindex "EHLO" "argument, setting"
23370 .cindex "LHLO argument setting"
23371 The value of this option is expanded after a connection to a another host has
23372 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
23373 command that starts the outgoing SMTP or LMTP session. The default value of the
23378 During the expansion, the variables &$host$& and &$host_address$& are set to
23379 the identity of the remote host, and the variables &$sending_ip_address$& and
23380 &$sending_port$& are set to the local IP address and port number that are being
23381 used. These variables can be used to generate different values for different
23382 servers or different local IP addresses. For example, if you want the string
23383 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
23384 interface address, you could use this:
23386 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
23387 {$primary_hostname}}
23389 The use of &%helo_data%& applies both to sending messages and when doing
23392 .option hosts smtp "string list&!!" unset
23393 Hosts are associated with an address by a router such as &(dnslookup)&, which
23394 finds the hosts by looking up the address domain in the DNS, or by
23395 &(manualroute)&, which has lists of hosts in its configuration. However,
23396 email addresses can be passed to the &(smtp)& transport by any router, and not
23397 all of them can provide an associated list of hosts.
23399 The &%hosts%& option specifies a list of hosts to be used if the address being
23400 processed does not have any hosts associated with it. The hosts specified by
23401 &%hosts%& are also used, whether or not the address has its own hosts, if
23402 &%hosts_override%& is set.
23404 The string is first expanded, before being interpreted as a colon-separated
23405 list of host names or IP addresses, possibly including port numbers. The
23406 separator may be changed to something other than colon, as described in section
23407 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
23408 item in a &%route_list%& setting for the &(manualroute)& router, as described
23409 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
23410 of the &(manualroute)& router is not available here.
23412 If the expansion fails, delivery is deferred. Unless the failure was caused by
23413 the inability to complete a lookup, the error is logged to the panic log as
23414 well as the main log. Host names are looked up either by searching directly for
23415 address records in the DNS or by calling &[gethostbyname()]& (or
23416 &[getipnodebyname()]& when available), depending on the setting of the
23417 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
23418 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
23421 During delivery, the hosts are tried in order, subject to their retry status,
23422 unless &%hosts_randomize%& is set.
23425 .option hosts_avoid_esmtp smtp "host list&!!" unset
23426 .cindex "ESMTP, avoiding use of"
23427 .cindex "HELO" "forcing use of"
23428 .cindex "EHLO" "avoiding use of"
23429 .cindex "PIPELINING" "avoiding the use of"
23430 This option is for use with broken hosts that announce ESMTP facilities (for
23431 example, PIPELINING) and then fail to implement them properly. When a host
23432 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
23433 start of the SMTP session. This means that it cannot use any of the ESMTP
23434 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
23437 .option hosts_avoid_pipelining smtp "host list&!!" unset
23438 .cindex "PIPELINING" "avoiding the use of"
23439 Exim will not use the SMTP PIPELINING extension when delivering to any host
23440 that matches this list, even if the server host advertises PIPELINING support.
23443 .option hosts_avoid_tls smtp "host list&!!" unset
23444 .cindex "TLS" "avoiding for certain hosts"
23445 Exim will not try to start a TLS session when delivering to any host that
23446 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
23448 .option hosts_verify_avoid_tls smtp "host list&!!" unset
23449 .cindex "TLS" "avoiding for certain hosts"
23450 Exim will not try to start a TLS session for a verify callout,
23451 or when delivering in cutthrough mode,
23452 to any host that matches this list.
23455 .option hosts_max_try smtp integer 5
23456 .cindex "host" "maximum number to try"
23457 .cindex "limit" "number of hosts tried"
23458 .cindex "limit" "number of MX tried"
23459 .cindex "MX record" "maximum tried"
23460 This option limits the number of IP addresses that are tried for any one
23461 delivery in cases where there are temporary delivery errors. Section
23462 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
23465 .option hosts_max_try_hardlimit smtp integer 50
23466 This is an additional check on the maximum number of IP addresses that Exim
23467 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
23472 .option hosts_nopass_tls smtp "host list&!!" unset
23473 .cindex "TLS" "passing connection"
23474 .cindex "multiple SMTP deliveries"
23475 .cindex "TLS" "multiple message deliveries"
23476 For any host that matches this list, a connection on which a TLS session has
23477 been started will not be passed to a new delivery process for sending another
23478 message on the same connection. See section &<<SECTmulmessam>>& for an
23479 explanation of when this might be needed.
23482 .option hosts_override smtp boolean false
23483 If this option is set and the &%hosts%& option is also set, any hosts that are
23484 attached to the address are ignored, and instead the hosts specified by the
23485 &%hosts%& option are always used. This option does not apply to
23486 &%fallback_hosts%&.
23489 .option hosts_randomize smtp boolean false
23490 .cindex "randomized host list"
23491 .cindex "host" "list of; randomized"
23492 .cindex "fallback" "randomized hosts"
23493 If this option is set, and either the list of hosts is taken from the
23494 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
23495 were not obtained from MX records (this includes fallback hosts from the
23496 router), and were not randomized by the router, the order of trying the hosts
23497 is randomized each time the transport runs. Randomizing the order of a host
23498 list can be used to do crude load sharing.
23500 When &%hosts_randomize%& is true, a host list may be split into groups whose
23501 order is separately randomized. This makes it possible to set up MX-like
23502 behaviour. The boundaries between groups are indicated by an item that is just
23503 &`+`& in the host list. For example:
23505 hosts = host1:host2:host3:+:host4:host5
23507 The order of the first three hosts and the order of the last two hosts is
23508 randomized for each use, but the first three always end up before the last two.
23509 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
23511 .option hosts_require_auth smtp "host list&!!" unset
23512 .cindex "authentication" "required by client"
23513 This option provides a list of servers for which authentication must succeed
23514 before Exim will try to transfer a message. If authentication fails for
23515 servers which are not in this list, Exim tries to send unauthenticated. If
23516 authentication fails for one of these servers, delivery is deferred. This
23517 temporary error is detectable in the retry rules, so it can be turned into a
23518 hard failure if required. See also &%hosts_try_auth%&, and chapter
23519 &<<CHAPSMTPAUTH>>& for details of authentication.
23522 .option hosts_request_ocsp smtp "host list&!!" *
23523 .cindex "TLS" "requiring for certain servers"
23524 Exim will request a Certificate Status on a
23525 TLS session for any host that matches this list.
23526 &%tls_verify_certificates%& should also be set for the transport.
23528 .option hosts_require_ocsp smtp "host list&!!" unset
23529 .cindex "TLS" "requiring for certain servers"
23530 Exim will request, and check for a valid Certificate Status being given, on a
23531 TLS session for any host that matches this list.
23532 &%tls_verify_certificates%& should also be set for the transport.
23534 .option hosts_require_tls smtp "host list&!!" unset
23535 .cindex "TLS" "requiring for certain servers"
23536 Exim will insist on using a TLS session when delivering to any host that
23537 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
23538 &*Note*&: This option affects outgoing mail only. To insist on TLS for
23539 incoming messages, use an appropriate ACL.
23541 .option hosts_try_auth smtp "host list&!!" unset
23542 .cindex "authentication" "optional in client"
23543 This option provides a list of servers to which, provided they announce
23544 authentication support, Exim will attempt to authenticate as a client when it
23545 connects. If authentication fails, Exim will try to transfer the message
23546 unauthenticated. See also &%hosts_require_auth%&, and chapter
23547 &<<CHAPSMTPAUTH>>& for details of authentication.
23549 .option hosts_try_prdr smtp "host list&!!" *
23550 .cindex "PRDR" "enabling, optional in client"
23551 This option provides a list of servers to which, provided they announce
23552 PRDR support, Exim will attempt to negotiate PRDR
23553 for multi-recipient messages.
23554 The option can usually be left as default.
23556 .option interface smtp "string list&!!" unset
23557 .cindex "bind IP address"
23558 .cindex "IP address" "binding"
23560 .vindex "&$host_address$&"
23561 This option specifies which interface to bind to when making an outgoing SMTP
23562 call. The value is an IP address, not an interface name such as
23563 &`eth0`&. Do not confuse this with the interface address that was used when a
23564 message was received, which is in &$received_ip_address$&, formerly known as
23565 &$interface_address$&. The name was changed to minimize confusion with the
23566 outgoing interface address. There is no variable that contains an outgoing
23567 interface address because, unless it is set by this option, its value is
23570 During the expansion of the &%interface%& option the variables &$host$& and
23571 &$host_address$& refer to the host to which a connection is about to be made
23572 during the expansion of the string. Forced expansion failure, or an empty
23573 string result causes the option to be ignored. Otherwise, after expansion, the
23574 string must be a list of IP addresses, colon-separated by default, but the
23575 separator can be changed in the usual way. For example:
23577 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
23579 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
23580 connection. If none of them are the correct type, the option is ignored. If
23581 &%interface%& is not set, or is ignored, the system's IP functions choose which
23582 interface to use if the host has more than one.
23585 .option keepalive smtp boolean true
23586 .cindex "keepalive" "on outgoing connection"
23587 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
23588 connections. When set, it causes the kernel to probe idle connections
23589 periodically, by sending packets with &"old"& sequence numbers. The other end
23590 of the connection should send a acknowledgment if the connection is still okay
23591 or a reset if the connection has been aborted. The reason for doing this is
23592 that it has the beneficial effect of freeing up certain types of connection
23593 that can get stuck when the remote host is disconnected without tidying up the
23594 TCP/IP call properly. The keepalive mechanism takes several hours to detect
23598 .option lmtp_ignore_quota smtp boolean false
23599 .cindex "LMTP" "ignoring quota errors"
23600 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
23601 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
23602 has advertised support for IGNOREQUOTA in its response to the LHLO command.
23604 .option max_rcpt smtp integer 100
23605 .cindex "RCPT" "maximum number of outgoing"
23606 This option limits the number of RCPT commands that are sent in a single
23607 SMTP message transaction. Each set of addresses is treated independently, and
23608 so can cause parallel connections to the same host if &%remote_max_parallel%&
23612 .option multi_domain smtp boolean&!! true
23613 .vindex "&$domain$&"
23614 When this option is set, the &(smtp)& transport can handle a number of
23615 addresses containing a mixture of different domains provided they all resolve
23616 to the same list of hosts. Turning the option off restricts the transport to
23617 handling only one domain at a time. This is useful if you want to use
23618 &$domain$& in an expansion for the transport, because it is set only when there
23619 is a single domain involved in a remote delivery.
23621 It is expanded per-address and can depend on any of
23622 &$address_data$&, &$domain_data$&, &$local_part_data$&,
23623 &$host$&, &$host_address$& and &$host_port$&.
23625 .option port smtp string&!! "see below"
23626 .cindex "port" "sending TCP/IP"
23627 .cindex "TCP/IP" "setting outgoing port"
23628 This option specifies the TCP/IP port on the server to which Exim connects.
23629 &*Note:*& Do not confuse this with the port that was used when a message was
23630 received, which is in &$received_port$&, formerly known as &$interface_port$&.
23631 The name was changed to minimize confusion with the outgoing port. There is no
23632 variable that contains an outgoing port.
23634 If the value of this option begins with a digit it is taken as a port number;
23635 otherwise it is looked up using &[getservbyname()]&. The default value is
23636 normally &"smtp"&, but if &%protocol%& is set to &"lmtp"&, the default is
23637 &"lmtp"&. If the expansion fails, or if a port number cannot be found, delivery
23642 .option protocol smtp string smtp
23643 .cindex "LMTP" "over TCP/IP"
23644 .cindex "ssmtp protocol" "outbound"
23645 .cindex "TLS" "SSL-on-connect outbound"
23647 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
23648 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
23649 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
23650 deliveries into closed message stores. Exim also has support for running LMTP
23651 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
23653 If this option is set to &"smtps"&, the default value for the &%port%& option
23654 changes to &"smtps"&, and the transport initiates TLS immediately after
23655 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
23656 The Internet standards bodies strongly discourage use of this mode.
23659 .option retry_include_ip_address smtp boolean&!! true
23660 Exim normally includes both the host name and the IP address in the key it
23661 constructs for indexing retry data after a temporary delivery failure. This
23662 means that when one of several IP addresses for a host is failing, it gets
23663 tried periodically (controlled by the retry rules), but use of the other IP
23664 addresses is not affected.
23666 However, in some dialup environments hosts are assigned a different IP address
23667 each time they connect. In this situation the use of the IP address as part of
23668 the retry key leads to undesirable behaviour. Setting this option false causes
23669 Exim to use only the host name.
23670 Since it is expanded it can be made to depend on the host or domain.
23673 .option serialize_hosts smtp "host list&!!" unset
23674 .cindex "serializing connections"
23675 .cindex "host" "serializing connections"
23676 Because Exim operates in a distributed manner, if several messages for the same
23677 host arrive at around the same time, more than one simultaneous connection to
23678 the remote host can occur. This is not usually a problem except when there is a
23679 slow link between the hosts. In that situation it may be helpful to restrict
23680 Exim to one connection at a time. This can be done by setting
23681 &%serialize_hosts%& to match the relevant hosts.
23683 .cindex "hints database" "serializing deliveries to a host"
23684 Exim implements serialization by means of a hints database in which a record is
23685 written whenever a process connects to one of the restricted hosts. The record
23686 is deleted when the connection is completed. Obviously there is scope for
23687 records to get left lying around if there is a system or program crash. To
23688 guard against this, Exim ignores any records that are more than six hours old.
23690 If you set up this kind of serialization, you should also arrange to delete the
23691 relevant hints database whenever your system reboots. The names of the files
23692 start with &_misc_& and they are kept in the &_spool/db_& directory. There
23693 may be one or two files, depending on the type of DBM in use. The same files
23694 are used for ETRN serialization.
23697 See also the &%max_parallel%& generic transport option.
23701 .option size_addition smtp integer 1024
23702 .cindex "SMTP" "SIZE"
23703 .cindex "message" "size issue for transport filter"
23704 .cindex "size" "of message"
23705 .cindex "transport" "filter"
23706 .cindex "filter" "transport filter"
23707 If a remote SMTP server indicates that it supports the SIZE option of the
23708 MAIL command, Exim uses this to pass over the message size at the start of
23709 an SMTP transaction. It adds the value of &%size_addition%& to the value it
23710 sends, to allow for headers and other text that may be added during delivery by
23711 configuration options or in a transport filter. It may be necessary to increase
23712 this if a lot of text is added to messages.
23714 Alternatively, if the value of &%size_addition%& is set negative, it disables
23715 the use of the SIZE option altogether.
23718 .option tls_certificate smtp string&!! unset
23719 .cindex "TLS" "client certificate, location of"
23720 .cindex "certificate" "client, location of"
23722 .vindex "&$host_address$&"
23723 The value of this option must be the absolute path to a file which contains the
23724 client's certificate, for possible use when sending a message over an encrypted
23725 connection. The values of &$host$& and &$host_address$& are set to the name and
23726 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
23729 &*Note*&: This option must be set if you want Exim to be able to use a TLS
23730 certificate when sending messages as a client. The global option of the same
23731 name specifies the certificate for Exim as a server; it is not automatically
23732 assumed that the same certificate should be used when Exim is operating as a
23736 .option tls_crl smtp string&!! unset
23737 .cindex "TLS" "client certificate revocation list"
23738 .cindex "certificate" "revocation list for client"
23739 This option specifies a certificate revocation list. The expanded value must
23740 be the name of a file that contains a CRL in PEM format.
23743 .option tls_dh_min_bits smtp integer 1024
23744 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
23745 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
23746 key agreement is negotiated, the server will provide a large prime number
23747 for use. This option establishes the minimum acceptable size of that number.
23748 If the parameter offered by the server is too small, then the TLS handshake
23751 Only supported when using GnuTLS.
23754 .option tls_privatekey smtp string&!! unset
23755 .cindex "TLS" "client private key, location of"
23757 .vindex "&$host_address$&"
23758 The value of this option must be the absolute path to a file which contains the
23759 client's private key. This is used when sending a message over an encrypted
23760 connection using a client certificate. The values of &$host$& and
23761 &$host_address$& are set to the name and address of the server during the
23762 expansion. If this option is unset, or the expansion is forced to fail, or the
23763 result is an empty string, the private key is assumed to be in the same file as
23764 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
23767 .option tls_require_ciphers smtp string&!! unset
23768 .cindex "TLS" "requiring specific ciphers"
23769 .cindex "cipher" "requiring specific"
23771 .vindex "&$host_address$&"
23772 The value of this option must be a list of permitted cipher suites, for use
23773 when setting up an outgoing encrypted connection. (There is a global option of
23774 the same name for controlling incoming connections.) The values of &$host$& and
23775 &$host_address$& are set to the name and address of the server during the
23776 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
23777 is used in different ways by OpenSSL and GnuTLS (see sections
23778 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
23779 ciphers is a preference order.
23783 .option tls_sni smtp string&!! unset
23784 .cindex "TLS" "Server Name Indication"
23785 .vindex "&$tls_sni$&"
23786 If this option is set then it sets the $tls_out_sni variable and causes any
23787 TLS session to pass this value as the Server Name Indication extension to
23788 the remote side, which can be used by the remote side to select an appropriate
23789 certificate and private key for the session.
23791 See &<<SECTtlssni>>& for more information.
23793 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
23799 .option tls_tempfail_tryclear smtp boolean true
23800 .cindex "4&'xx'& responses" "to STARTTLS"
23801 When the server host is not in &%hosts_require_tls%&, and there is a problem in
23802 setting up a TLS session, this option determines whether or not Exim should try
23803 to deliver the message unencrypted. If it is set false, delivery to the
23804 current host is deferred; if there are other hosts, they are tried. If this
23805 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
23806 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
23807 TLS negotiation fails, Exim closes the current connection (because it is in an
23808 unknown state), opens a new one to the same host, and then tries the delivery
23812 .option tls_try_verify_hosts smtp "host list&!!" *
23813 .cindex "TLS" "server certificate verification"
23814 .cindex "certificate" "verification of server"
23815 This option gives a list of hosts for which, on encrypted connections,
23816 certificate verification will be tried but need not succeed.
23817 The &%tls_verify_certificates%& option must also be set.
23818 Note that unless the host is in this list
23819 TLS connections will be denied to hosts using self-signed certificates
23820 when &%tls_verify_certificates%& is matched.
23821 The &$tls_out_certificate_verified$& variable is set when
23822 certificate verification succeeds.
23825 .option tls_verify_cert_hostnames smtp "host list&!!" *
23826 .cindex "TLS" "server certificate hostname verification"
23827 .cindex "certificate" "verification of server"
23828 This option give a list of hosts for which,
23829 while verifying the server certificate,
23830 checks will be included on the host name
23831 (note that this will generally be the result of a DNS MX lookup)
23832 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
23833 limited to being the initial component of a 3-or-more component FQDN.
23835 There is no equivalent checking on client certificates.
23838 .option tls_verify_certificates smtp string&!! system
23839 .cindex "TLS" "server certificate verification"
23840 .cindex "certificate" "verification of server"
23842 .vindex "&$host_address$&"
23843 The value of this option must be either the
23845 or the absolute path to
23846 a file or directory containing permitted certificates for servers,
23847 for use when setting up an encrypted connection.
23849 The "system" value for the option will use a location compiled into the SSL library.
23850 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
23851 is taken as empty and an explicit location
23854 The use of a directory for the option value is not available for GnuTLS versions
23855 preceding 3.3.6 and a single file must be used.
23857 With OpenSSL the certificates specified
23859 either by file or directory
23860 are added to those given by the system default location.
23862 The values of &$host$& and
23863 &$host_address$& are set to the name and address of the server during the
23864 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
23866 For back-compatibility,
23867 if neither tls_verify_hosts nor tls_try_verify_hosts are set
23868 (a single-colon empty list counts as being set)
23869 and certificate verification fails the TLS connection is closed.
23872 .option tls_verify_hosts smtp "host list&!!" unset
23873 .cindex "TLS" "server certificate verification"
23874 .cindex "certificate" "verification of server"
23875 This option gives a list of hosts for which. on encrypted connections,
23876 certificate verification must succeed.
23877 The &%tls_verify_certificates%& option must also be set.
23878 If both this option and &%tls_try_verify_hosts%& are unset
23879 operation is as if this option selected all hosts.
23884 .section "How the limits for the number of hosts to try are used" &&&
23886 .cindex "host" "maximum number to try"
23887 .cindex "limit" "hosts; maximum number tried"
23888 There are two options that are concerned with the number of hosts that are
23889 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
23890 &%hosts_max_try_hardlimit%&.
23893 The &%hosts_max_try%& option limits the number of hosts that are tried
23894 for a single delivery. However, despite the term &"host"& in its name, the
23895 option actually applies to each IP address independently. In other words, a
23896 multihomed host is treated as several independent hosts, just as it is for
23899 Many of the larger ISPs have multiple MX records which often point to
23900 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
23901 created as a result of routing one of these domains.
23903 Trying every single IP address on such a long list does not seem sensible; if
23904 several at the top of the list fail, it is reasonable to assume there is some
23905 problem that is likely to affect all of them. Roughly speaking, the value of
23906 &%hosts_max_try%& is the maximum number that are tried before deferring the
23907 delivery. However, the logic cannot be quite that simple.
23909 Firstly, IP addresses that are skipped because their retry times have not
23910 arrived do not count, and in addition, addresses that are past their retry
23911 limits are also not counted, even when they are tried. This means that when
23912 some IP addresses are past their retry limits, more than the value of
23913 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
23914 that all IP addresses are considered before timing out an email address (but
23915 see below for an exception).
23917 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
23918 list to see if there is a subsequent host with a different (higher valued) MX.
23919 If there is, that host is considered next, and the current IP address is used
23920 but not counted. This behaviour helps in the case of a domain with a retry rule
23921 that hardly ever delays any hosts, as is now explained:
23923 Consider the case of a long list of hosts with one MX value, and a few with a
23924 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
23925 hosts at the top of the list are tried at first. With the default retry rule,
23926 which specifies increasing retry times, the higher MX hosts are eventually
23927 tried when those at the top of the list are skipped because they have not
23928 reached their retry times.
23930 However, it is common practice to put a fixed short retry time on domains for
23931 large ISPs, on the grounds that their servers are rarely down for very long.
23932 Unfortunately, these are exactly the domains that tend to resolve to long lists
23933 of hosts. The short retry time means that the lowest MX hosts are tried every
23934 time. The attempts may be in a different order because of random sorting, but
23935 without the special MX check, the higher MX hosts would never be tried until
23936 all the lower MX hosts had timed out (which might be several days), because
23937 there are always some lower MX hosts that have reached their retry times. With
23938 the special check, Exim considers at least one IP address from each MX value at
23939 every delivery attempt, even if the &%hosts_max_try%& limit has already been
23942 The above logic means that &%hosts_max_try%& is not a hard limit, and in
23943 particular, Exim normally eventually tries all the IP addresses before timing
23944 out an email address. When &%hosts_max_try%& was implemented, this seemed a
23945 reasonable thing to do. Recently, however, some lunatic DNS configurations have
23946 been set up with hundreds of IP addresses for some domains. It can
23947 take a very long time indeed for an address to time out in these cases.
23949 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
23950 Exim never tries more than this number of IP addresses; if it hits this limit
23951 and they are all timed out, the email address is bounced, even though not all
23952 possible IP addresses have been tried.
23953 .ecindex IIDsmttra1
23954 .ecindex IIDsmttra2
23960 . ////////////////////////////////////////////////////////////////////////////
23961 . ////////////////////////////////////////////////////////////////////////////
23963 .chapter "Address rewriting" "CHAPrewrite"
23964 .scindex IIDaddrew "rewriting" "addresses"
23965 There are some circumstances in which Exim automatically rewrites domains in
23966 addresses. The two most common are when an address is given without a domain
23967 (referred to as an &"unqualified address"&) or when an address contains an
23968 abbreviated domain that is expanded by DNS lookup.
23970 Unqualified envelope addresses are accepted only for locally submitted
23971 messages, or for messages that are received from hosts matching
23972 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
23973 appropriate. Unqualified addresses in header lines are qualified if they are in
23974 locally submitted messages, or messages from hosts that are permitted to send
23975 unqualified envelope addresses. Otherwise, unqualified addresses in header
23976 lines are neither qualified nor rewritten.
23978 One situation in which Exim does &'not'& automatically rewrite a domain is
23979 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
23980 such a domain should be rewritten using the &"canonical"& name, and some MTAs
23981 do this. The new RFCs do not contain this suggestion.
23984 .section "Explicitly configured address rewriting" "SECID147"
23985 This chapter describes the rewriting rules that can be used in the
23986 main rewrite section of the configuration file, and also in the generic
23987 &%headers_rewrite%& option that can be set on any transport.
23989 Some people believe that configured address rewriting is a Mortal Sin.
23990 Others believe that life is not possible without it. Exim provides the
23991 facility; you do not have to use it.
23993 The main rewriting rules that appear in the &"rewrite"& section of the
23994 configuration file are applied to addresses in incoming messages, both envelope
23995 addresses and addresses in header lines. Each rule specifies the types of
23996 address to which it applies.
23998 Whether or not addresses in header lines are rewritten depends on the origin of
23999 the headers and the type of rewriting. Global rewriting, that is, rewriting
24000 rules from the rewrite section of the configuration file, is applied only to
24001 those headers that were received with the message. Header lines that are added
24002 by ACLs or by a system filter or by individual routers or transports (which
24003 are specific to individual recipient addresses) are not rewritten by the global
24006 Rewriting at transport time, by means of the &%headers_rewrite%& option,
24007 applies all headers except those added by routers and transports. That is, as
24008 well as the headers that were received with the message, it also applies to
24009 headers that were added by an ACL or a system filter.
24012 In general, rewriting addresses from your own system or domain has some
24013 legitimacy. Rewriting other addresses should be done only with great care and
24014 in special circumstances. The author of Exim believes that rewriting should be
24015 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
24016 Although it can sometimes be used as a routing tool, this is very strongly
24019 There are two commonly encountered circumstances where rewriting is used, as
24020 illustrated by these examples:
24023 The company whose domain is &'hitch.fict.example'& has a number of hosts that
24024 exchange mail with each other behind a firewall, but there is only a single
24025 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
24026 &'hitch.fict.example'& when sending mail off-site.
24028 A host rewrites the local parts of its own users so that, for example,
24029 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
24034 .section "When does rewriting happen?" "SECID148"
24035 .cindex "rewriting" "timing of"
24036 .cindex "&ACL;" "rewriting addresses in"
24037 Configured address rewriting can take place at several different stages of a
24038 message's processing.
24040 .vindex "&$sender_address$&"
24041 At the start of an ACL for MAIL, the sender address may have been rewritten
24042 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
24043 ordinary rewrite rules have yet been applied. If, however, the sender address
24044 is verified in the ACL, it is rewritten before verification, and remains
24045 rewritten thereafter. The subsequent value of &$sender_address$& is the
24046 rewritten address. This also applies if sender verification happens in a
24047 RCPT ACL. Otherwise, when the sender address is not verified, it is
24048 rewritten as soon as a message's header lines have been received.
24050 .vindex "&$domain$&"
24051 .vindex "&$local_part$&"
24052 Similarly, at the start of an ACL for RCPT, the current recipient's address
24053 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
24054 rewrite rules have yet been applied to it. However, the behaviour is different
24055 from the sender address when a recipient is verified. The address is rewritten
24056 for the verification, but the rewriting is not remembered at this stage. The
24057 value of &$local_part$& and &$domain$& after verification are always the same
24058 as they were before (that is, they contain the unrewritten &-- except for
24059 SMTP-time rewriting &-- address).
24061 As soon as a message's header lines have been received, all the envelope
24062 recipient addresses are permanently rewritten, and rewriting is also applied to
24063 the addresses in the header lines (if configured). This happens before adding
24064 any header lines that were specified in MAIL or RCPT ACLs, and
24065 .cindex "&[local_scan()]& function" "address rewriting; timing of"
24066 before the DATA ACL and &[local_scan()]& functions are run.
24068 When an address is being routed, either for delivery or for verification,
24069 rewriting is applied immediately to child addresses that are generated by
24070 redirection, unless &%no_rewrite%& is set on the router.
24072 .cindex "envelope sender" "rewriting at transport time"
24073 .cindex "rewriting" "at transport time"
24074 .cindex "header lines" "rewriting at transport time"
24075 At transport time, additional rewriting of addresses in header lines can be
24076 specified by setting the generic &%headers_rewrite%& option on a transport.
24077 This option contains rules that are identical in form to those in the rewrite
24078 section of the configuration file. They are applied to the original message
24079 header lines and any that were added by ACLs or a system filter. They are not
24080 applied to header lines that are added by routers or the transport.
24082 The outgoing envelope sender can be rewritten by means of the &%return_path%&
24083 transport option. However, it is not possible to rewrite envelope recipients at
24089 .section "Testing the rewriting rules that apply on input" "SECID149"
24090 .cindex "rewriting" "testing"
24091 .cindex "testing" "rewriting"
24092 Exim's input rewriting configuration appears in a part of the run time
24093 configuration file headed by &"begin rewrite"&. It can be tested by the
24094 &%-brw%& command line option. This takes an address (which can be a full RFC
24095 2822 address) as its argument. The output is a list of how the address would be
24096 transformed by the rewriting rules for each of the different places it might
24097 appear in an incoming message, that is, for each different header and for the
24098 envelope sender and recipient fields. For example,
24100 exim -brw ph10@exim.workshop.example
24102 might produce the output
24104 sender: Philip.Hazel@exim.workshop.example
24105 from: Philip.Hazel@exim.workshop.example
24106 to: ph10@exim.workshop.example
24107 cc: ph10@exim.workshop.example
24108 bcc: ph10@exim.workshop.example
24109 reply-to: Philip.Hazel@exim.workshop.example
24110 env-from: Philip.Hazel@exim.workshop.example
24111 env-to: ph10@exim.workshop.example
24113 which shows that rewriting has been set up for that address when used in any of
24114 the source fields, but not when it appears as a recipient address. At the
24115 present time, there is no equivalent way of testing rewriting rules that are
24116 set for a particular transport.
24119 .section "Rewriting rules" "SECID150"
24120 .cindex "rewriting" "rules"
24121 The rewrite section of the configuration file consists of lines of rewriting
24124 <&'source pattern'&> <&'replacement'&> <&'flags'&>
24126 Rewriting rules that are specified for the &%headers_rewrite%& generic
24127 transport option are given as a colon-separated list. Each item in the list
24128 takes the same form as a line in the main rewriting configuration (except that
24129 any colons must be doubled, of course).
24131 The formats of source patterns and replacement strings are described below.
24132 Each is terminated by white space, unless enclosed in double quotes, in which
24133 case normal quoting conventions apply inside the quotes. The flags are single
24134 characters which may appear in any order. Spaces and tabs between them are
24137 For each address that could potentially be rewritten, the rules are scanned in
24138 order, and replacements for the address from earlier rules can themselves be
24139 replaced by later rules (but see the &"q"& and &"R"& flags).
24141 The order in which addresses are rewritten is undefined, may change between
24142 releases, and must not be relied on, with one exception: when a message is
24143 received, the envelope sender is always rewritten first, before any header
24144 lines are rewritten. For example, the replacement string for a rewrite of an
24145 address in &'To:'& must not assume that the message's address in &'From:'& has
24146 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
24147 that the envelope sender has already been rewritten.
24149 .vindex "&$domain$&"
24150 .vindex "&$local_part$&"
24151 The variables &$local_part$& and &$domain$& can be used in the replacement
24152 string to refer to the address that is being rewritten. Note that lookup-driven
24153 rewriting can be done by a rule of the form
24157 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
24158 refer to the address that is being rewritten.
24161 .section "Rewriting patterns" "SECID151"
24162 .cindex "rewriting" "patterns"
24163 .cindex "address list" "in a rewriting pattern"
24164 The source pattern in a rewriting rule is any item which may appear in an
24165 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
24166 single-item address list, which means that it is expanded before being tested
24167 against the address. As always, if you use a regular expression as a pattern,
24168 you must take care to escape dollar and backslash characters, or use the &`\N`&
24169 facility to suppress string expansion within the regular expression.
24171 Domains in patterns should be given in lower case. Local parts in patterns are
24172 case-sensitive. If you want to do case-insensitive matching of local parts, you
24173 can use a regular expression that starts with &`^(?i)`&.
24175 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
24176 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
24177 depending on the type of match which occurred. These can be used in the
24178 replacement string to insert portions of the incoming address. &$0$& always
24179 refers to the complete incoming address. When a regular expression is used, the
24180 numerical variables are set from its capturing subexpressions. For other types
24181 of pattern they are set as follows:
24184 If a local part or domain starts with an asterisk, the numerical variables
24185 refer to the character strings matched by asterisks, with &$1$& associated with
24186 the first asterisk, and &$2$& with the second, if present. For example, if the
24189 *queen@*.fict.example
24191 is matched against the address &'hearts-queen@wonderland.fict.example'& then
24193 $0 = hearts-queen@wonderland.fict.example
24197 Note that if the local part does not start with an asterisk, but the domain
24198 does, it is &$1$& that contains the wild part of the domain.
24201 If the domain part of the pattern is a partial lookup, the wild and fixed parts
24202 of the domain are placed in the next available numerical variables. Suppose,
24203 for example, that the address &'foo@bar.baz.example'& is processed by a
24204 rewriting rule of the form
24206 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
24208 and the key in the file that matches the domain is &`*.baz.example`&. Then
24214 If the address &'foo@baz.example'& is looked up, this matches the same
24215 wildcard file entry, and in this case &$2$& is set to the empty string, but
24216 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
24217 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
24218 whole domain. For non-partial domain lookups, no numerical variables are set.
24222 .section "Rewriting replacements" "SECID152"
24223 .cindex "rewriting" "replacements"
24224 If the replacement string for a rule is a single asterisk, addresses that
24225 match the pattern and the flags are &'not'& rewritten, and no subsequent
24226 rewriting rules are scanned. For example,
24228 hatta@lookingglass.fict.example * f
24230 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
24233 .vindex "&$domain$&"
24234 .vindex "&$local_part$&"
24235 If the replacement string is not a single asterisk, it is expanded, and must
24236 yield a fully qualified address. Within the expansion, the variables
24237 &$local_part$& and &$domain$& refer to the address that is being rewritten.
24238 Any letters they contain retain their original case &-- they are not lower
24239 cased. The numerical variables are set up according to the type of pattern that
24240 matched the address, as described above. If the expansion is forced to fail by
24241 the presence of &"fail"& in a conditional or lookup item, rewriting by the
24242 current rule is abandoned, but subsequent rules may take effect. Any other
24243 expansion failure causes the entire rewriting operation to be abandoned, and an
24244 entry written to the panic log.
24248 .section "Rewriting flags" "SECID153"
24249 There are three different kinds of flag that may appear on rewriting rules:
24252 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
24255 A flag that specifies rewriting at SMTP time: S.
24257 Flags that control the rewriting process: Q, q, R, w.
24260 For rules that are part of the &%headers_rewrite%& generic transport option,
24261 E, F, T, and S are not permitted.
24265 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
24267 .cindex "rewriting" "flags"
24268 If none of the following flag letters, nor the &"S"& flag (see section
24269 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
24270 and to both the sender and recipient fields of the envelope, whereas a
24271 transport-time rewriting rule just applies to all headers. Otherwise, the
24272 rewriting rule is skipped unless the relevant addresses are being processed.
24274 &`E`& rewrite all envelope fields
24275 &`F`& rewrite the envelope From field
24276 &`T`& rewrite the envelope To field
24277 &`b`& rewrite the &'Bcc:'& header
24278 &`c`& rewrite the &'Cc:'& header
24279 &`f`& rewrite the &'From:'& header
24280 &`h`& rewrite all headers
24281 &`r`& rewrite the &'Reply-To:'& header
24282 &`s`& rewrite the &'Sender:'& header
24283 &`t`& rewrite the &'To:'& header
24285 "All headers" means all of the headers listed above that can be selected
24286 individually, plus their &'Resent-'& versions. It does not include
24287 other headers such as &'Subject:'& etc.
24289 You should be particularly careful about rewriting &'Sender:'& headers, and
24290 restrict this to special known cases in your own domains.
24293 .section "The SMTP-time rewriting flag" "SECTrewriteS"
24294 .cindex "SMTP" "rewriting malformed addresses"
24295 .cindex "RCPT" "rewriting argument of"
24296 .cindex "MAIL" "rewriting argument of"
24297 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
24298 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
24299 before any other processing; even before syntax checking. The pattern is
24300 required to be a regular expression, and it is matched against the whole of the
24301 data for the command, including any surrounding angle brackets.
24303 .vindex "&$domain$&"
24304 .vindex "&$local_part$&"
24305 This form of rewrite rule allows for the handling of addresses that are not
24306 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
24307 input). Because the input is not required to be a syntactically valid address,
24308 the variables &$local_part$& and &$domain$& are not available during the
24309 expansion of the replacement string. The result of rewriting replaces the
24310 original address in the MAIL or RCPT command.
24313 .section "Flags controlling the rewriting process" "SECID155"
24314 There are four flags which control the way the rewriting process works. These
24315 take effect only when a rule is invoked, that is, when the address is of the
24316 correct type (matches the flags) and matches the pattern:
24319 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
24320 unqualified local part. It is qualified with &%qualify_recipient%&. In the
24321 absence of &"Q"& the rewritten address must always include a domain.
24323 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
24324 even if no rewriting actually takes place because of a &"fail"& in the
24325 expansion. The &"q"& flag is not effective if the address is of the wrong type
24326 (does not match the flags) or does not match the pattern.
24328 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
24329 address, up to ten times. It can be combined with the &"q"& flag, to stop
24330 rewriting once it fails to match (after at least one successful rewrite).
24332 .cindex "rewriting" "whole addresses"
24333 When an address in a header is rewritten, the rewriting normally applies only
24334 to the working part of the address, with any comments and RFC 2822 &"phrase"&
24335 left unchanged. For example, rewriting might change
24337 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
24341 From: Ford Prefect <prefectf@hitch.fict.example>
24344 Sometimes there is a need to replace the whole address item, and this can be
24345 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
24346 causes an address in a header line to be rewritten, the entire address is
24347 replaced, not just the working part. The replacement must be a complete RFC
24348 2822 address, including the angle brackets if necessary. If text outside angle
24349 brackets contains a character whose value is greater than 126 or less than 32
24350 (except for tab), the text is encoded according to RFC 2047. The character set
24351 is taken from &%headers_charset%&, which defaults to ISO-8859-1.
24353 When the &"w"& flag is set on a rule that causes an envelope address to be
24354 rewritten, all but the working part of the replacement address is discarded.
24358 .section "Rewriting examples" "SECID156"
24359 Here is an example of the two common rewriting paradigms:
24361 *@*.hitch.fict.example $1@hitch.fict.example
24362 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
24363 {$value}fail}@hitch.fict.example bctfrF
24365 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
24366 the string expansion to fail if the lookup does not succeed. In this context it
24367 has the effect of leaving the original address unchanged, but Exim goes on to
24368 consider subsequent rewriting rules, if any, because the &"q"& flag is not
24369 present in that rule. An alternative to &"fail"& would be to supply &$1$&
24370 explicitly, which would cause the rewritten address to be the same as before,
24371 at the cost of a small bit of processing. Not supplying either of these is an
24372 error, since the rewritten address would then contain no local part.
24374 The first example above replaces the domain with a superior, more general
24375 domain. This may not be desirable for certain local parts. If the rule
24377 root@*.hitch.fict.example *
24379 were inserted before the first rule, rewriting would be suppressed for the
24380 local part &'root'& at any domain ending in &'hitch.fict.example'&.
24382 Rewriting can be made conditional on a number of tests, by making use of
24383 &${if$& in the expansion item. For example, to apply a rewriting rule only to
24384 messages that originate outside the local host:
24386 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
24387 {$1@hitch.fict.example}fail}"
24389 The replacement string is quoted in this example because it contains white
24392 .cindex "rewriting" "bang paths"
24393 .cindex "bang paths" "rewriting"
24394 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
24395 an address it treats it as an unqualified local part which it qualifies with
24396 the local qualification domain (if the source of the message is local or if the
24397 remote host is permitted to send unqualified addresses). Rewriting can
24398 sometimes be used to handle simple bang paths with a fixed number of
24399 components. For example, the rule
24401 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
24403 rewrites a two-component bang path &'host.name!user'& as the domain address
24404 &'user@host.name'&. However, there is a security implication in using this as
24405 a global rewriting rule for envelope addresses. It can provide a backdoor
24406 method for using your system as a relay, because the incoming addresses appear
24407 to be local. If the bang path addresses are received via SMTP, it is safer to
24408 use the &"S"& flag to rewrite them as they are received, so that relay checking
24409 can be done on the rewritten addresses.
24416 . ////////////////////////////////////////////////////////////////////////////
24417 . ////////////////////////////////////////////////////////////////////////////
24419 .chapter "Retry configuration" "CHAPretry"
24420 .scindex IIDretconf1 "retry" "configuration, description of"
24421 .scindex IIDregconf2 "configuration file" "retry section"
24422 The &"retry"& section of the runtime configuration file contains a list of
24423 retry rules that control how often Exim tries to deliver messages that cannot
24424 be delivered at the first attempt. If there are no retry rules (the section is
24425 empty or not present), there are no retries. In this situation, temporary
24426 errors are treated as permanent. The default configuration contains a single,
24427 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
24428 line option can be used to test which retry rule will be used for a given
24429 address, domain and error.
24431 The most common cause of retries is temporary failure to deliver to a remote
24432 host because the host is down, or inaccessible because of a network problem.
24433 Exim's retry processing in this case is applied on a per-host (strictly, per IP
24434 address) basis, not on a per-message basis. Thus, if one message has recently
24435 been delayed, delivery of a new message to the same host is not immediately
24436 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
24437 log selector is set, the message
24438 .cindex "retry" "time not reached"
24439 &"retry time not reached"& is written to the main log whenever a delivery is
24440 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
24441 the handling of errors during remote deliveries.
24443 Retry processing applies to routing as well as to delivering, except as covered
24444 in the next paragraph. The retry rules do not distinguish between these
24445 actions. It is not possible, for example, to specify different behaviour for
24446 failures to route the domain &'snark.fict.example'& and failures to deliver to
24447 the host &'snark.fict.example'&. I didn't think anyone would ever need this
24448 added complication, so did not implement it. However, although they share the
24449 same retry rule, the actual retry times for routing and transporting a given
24450 domain are maintained independently.
24452 When a delivery is not part of a queue run (typically an immediate delivery on
24453 receipt of a message), the routers are always run, and local deliveries are
24454 always attempted, even if retry times are set for them. This makes for better
24455 behaviour if one particular message is causing problems (for example, causing
24456 quota overflow, or provoking an error in a filter file). If such a delivery
24457 suffers a temporary failure, the retry data is updated as normal, and
24458 subsequent delivery attempts from queue runs occur only when the retry time for
24459 the local address is reached.
24461 .section "Changing retry rules" "SECID157"
24462 If you change the retry rules in your configuration, you should consider
24463 whether or not to delete the retry data that is stored in Exim's spool area in
24464 files with names like &_db/retry_&. Deleting any of Exim's hints files is
24465 always safe; that is why they are called &"hints"&.
24467 The hints retry data contains suggested retry times based on the previous
24468 rules. In the case of a long-running problem with a remote host, it might
24469 record the fact that the host has timed out. If your new rules increase the
24470 timeout time for such a host, you should definitely remove the old retry data
24471 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
24472 messages that it should now be retaining.
24476 .section "Format of retry rules" "SECID158"
24477 .cindex "retry" "rules"
24478 Each retry rule occupies one line and consists of three or four parts,
24479 separated by white space: a pattern, an error name, an optional list of sender
24480 addresses, and a list of retry parameters. The pattern and sender lists must be
24481 enclosed in double quotes if they contain white space. The rules are searched
24482 in order until one is found where the pattern, error name, and sender list (if
24483 present) match the failing host or address, the error that occurred, and the
24484 message's sender, respectively.
24487 The pattern is any single item that may appear in an address list (see section
24488 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
24489 which means that it is expanded before being tested against the address that
24490 has been delayed. A negated address list item is permitted. Address
24491 list processing treats a plain domain name as if it were preceded by &"*@"&,
24492 which makes it possible for many retry rules to start with just a domain. For
24495 lookingglass.fict.example * F,24h,30m;
24497 provides a rule for any address in the &'lookingglass.fict.example'& domain,
24500 alice@lookingglass.fict.example * F,24h,30m;
24502 applies only to temporary failures involving the local part &%alice%&.
24503 In practice, almost all rules start with a domain name pattern without a local
24506 .cindex "regular expressions" "in retry rules"
24507 &*Warning*&: If you use a regular expression in a retry rule pattern, it
24508 must match a complete address, not just a domain, because that is how regular
24509 expressions work in address lists.
24511 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
24512 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
24516 .section "Choosing which retry rule to use for address errors" "SECID159"
24517 When Exim is looking for a retry rule after a routing attempt has failed (for
24518 example, after a DNS timeout), each line in the retry configuration is tested
24519 against the complete address only if &%retry_use_local_part%& is set for the
24520 router. Otherwise, only the domain is used, except when matching against a
24521 regular expression, when the local part of the address is replaced with &"*"&.
24522 A domain on its own can match a domain pattern, or a pattern that starts with
24523 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
24524 &%check_local_user%& is true, and false for other routers.
24526 Similarly, when Exim is looking for a retry rule after a local delivery has
24527 failed (for example, after a mailbox full error), each line in the retry
24528 configuration is tested against the complete address only if
24529 &%retry_use_local_part%& is set for the transport (it defaults true for all
24532 .cindex "4&'xx'& responses" "retry rules for"
24533 However, when Exim is looking for a retry rule after a remote delivery attempt
24534 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
24535 whole address is always used as the key when searching the retry rules. The
24536 rule that is found is used to create a retry time for the combination of the
24537 failing address and the message's sender. It is the combination of sender and
24538 recipient that is delayed in subsequent queue runs until its retry time is
24539 reached. You can delay the recipient without regard to the sender by setting
24540 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
24541 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
24546 .section "Choosing which retry rule to use for host and message errors" &&&
24548 For a temporary error that is not related to an individual address (for
24549 example, a connection timeout), each line in the retry configuration is checked
24550 twice. First, the name of the remote host is used as a domain name (preceded by
24551 &"*@"& when matching a regular expression). If this does not match the line,
24552 the domain from the email address is tried in a similar fashion. For example,
24553 suppose the MX records for &'a.b.c.example'& are
24555 a.b.c.example MX 5 x.y.z.example
24559 and the retry rules are
24561 p.q.r.example * F,24h,30m;
24562 a.b.c.example * F,4d,45m;
24564 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
24565 first rule matches neither the host nor the domain, so Exim looks at the second
24566 rule. This does not match the host, but it does match the domain, so it is used
24567 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
24568 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
24569 first retry rule is used, because it matches the host.
24571 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
24572 first rule to determine retry times, but for all the other hosts for the domain
24573 &'a.b.c.example'&, the second rule is used. The second rule is also used if
24574 routing to &'a.b.c.example'& suffers a temporary failure.
24576 &*Note*&: The host name is used when matching the patterns, not its IP address.
24577 However, if a message is routed directly to an IP address without the use of a
24578 host name, for example, if a &(manualroute)& router contains a setting such as:
24580 route_list = *.a.example 192.168.34.23
24582 then the &"host name"& that is used when searching for a retry rule is the
24583 textual form of the IP address.
24585 .section "Retry rules for specific errors" "SECID161"
24586 .cindex "retry" "specific errors; specifying"
24587 The second field in a retry rule is the name of a particular error, or an
24588 asterisk, which matches any error. The errors that can be tested for are:
24591 .vitem &%auth_failed%&
24592 Authentication failed when trying to send to a host in the
24593 &%hosts_require_auth%& list in an &(smtp)& transport.
24595 .vitem &%data_4xx%&
24596 A 4&'xx'& error was received for an outgoing DATA command, either immediately
24597 after the command, or after sending the message's data.
24599 .vitem &%mail_4xx%&
24600 A 4&'xx'& error was received for an outgoing MAIL command.
24602 .vitem &%rcpt_4xx%&
24603 A 4&'xx'& error was received for an outgoing RCPT command.
24606 For the three 4&'xx'& errors, either the first or both of the x's can be given
24607 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
24608 recognize 452 errors given to RCPT commands for addresses in a certain domain,
24609 and have retries every ten minutes with a one-hour timeout, you could set up a
24610 retry rule of this form:
24612 the.domain.name rcpt_452 F,1h,10m
24614 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
24615 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
24618 .vitem &%lost_connection%&
24619 A server unexpectedly closed the SMTP connection. There may, of course,
24620 legitimate reasons for this (host died, network died), but if it repeats a lot
24621 for the same host, it indicates something odd.
24624 A DNS lookup for a host failed.
24625 Note that a &%dnslookup%& router will need to have matched
24626 its &%fail_defer_domains%& option for this retry type to be usable.
24627 Also note that a &%manualroute%& router will probably need
24628 its &%host_find_failed%& option set to &%defer%&.
24630 .vitem &%refused_MX%&
24631 A connection to a host obtained from an MX record was refused.
24633 .vitem &%refused_A%&
24634 A connection to a host not obtained from an MX record was refused.
24637 A connection was refused.
24639 .vitem &%timeout_connect_MX%&
24640 A connection attempt to a host obtained from an MX record timed out.
24642 .vitem &%timeout_connect_A%&
24643 A connection attempt to a host not obtained from an MX record timed out.
24645 .vitem &%timeout_connect%&
24646 A connection attempt timed out.
24648 .vitem &%timeout_MX%&
24649 There was a timeout while connecting or during an SMTP session with a host
24650 obtained from an MX record.
24652 .vitem &%timeout_A%&
24653 There was a timeout while connecting or during an SMTP session with a host not
24654 obtained from an MX record.
24657 There was a timeout while connecting or during an SMTP session.
24659 .vitem &%tls_required%&
24660 The server was required to use TLS (it matched &%hosts_require_tls%& in the
24661 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
24662 to STARTTLS, or there was a problem setting up the TLS connection.
24665 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
24668 .vitem &%quota_%&<&'time'&>
24669 .cindex "quota" "error testing in retry rule"
24670 .cindex "retry" "quota error testing"
24671 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
24672 transport, and the mailbox has not been accessed for <&'time'&>. For example,
24673 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
24677 .cindex "mailbox" "time of last read"
24678 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
24679 timeouts when the mailbox is full and is not being read by its owner. Ideally,
24680 it should be based on the last time that the user accessed the mailbox.
24681 However, it is not always possible to determine this. Exim uses the following
24685 If the mailbox is a single file, the time of last access (the &"atime"&) is
24686 used. As no new messages are being delivered (because the mailbox is over
24687 quota), Exim does not access the file, so this is the time of last user access.
24689 .cindex "maildir format" "time of last read"
24690 For a maildir delivery, the time of last modification of the &_new_&
24691 subdirectory is used. As the mailbox is over quota, no new files are created in
24692 the &_new_& subdirectory, because no new messages are being delivered. Any
24693 change to the &_new_& subdirectory is therefore assumed to be the result of an
24694 MUA moving a new message to the &_cur_& directory when it is first read. The
24695 time that is used is therefore the last time that the user read a new message.
24697 For other kinds of multi-file mailbox, the time of last access cannot be
24698 obtained, so a retry rule that uses this type of error field is never matched.
24701 The quota errors apply both to system-enforced quotas and to Exim's own quota
24702 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
24703 when a local delivery is deferred because a partition is full (the ENOSPC
24708 .section "Retry rules for specified senders" "SECID162"
24709 .cindex "retry" "rules; sender-specific"
24710 You can specify retry rules that apply only when the failing message has a
24711 specific sender. In particular, this can be used to define retry rules that
24712 apply only to bounce messages. The third item in a retry rule can be of this
24715 &`senders=`&<&'address list'&>
24717 The retry timings themselves are then the fourth item. For example:
24719 * rcpt_4xx senders=: F,1h,30m
24721 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
24722 host. If the address list contains white space, it must be enclosed in quotes.
24725 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
24727 &*Warning*&: This facility can be unhelpful if it is used for host errors
24728 (which do not depend on the recipient). The reason is that the sender is used
24729 only to match the retry rule. Once the rule has been found for a host error,
24730 its contents are used to set a retry time for the host, and this will apply to
24731 all messages, not just those with specific senders.
24733 When testing retry rules using &%-brt%&, you can supply a sender using the
24734 &%-f%& command line option, like this:
24736 exim -f "" -brt user@dom.ain
24738 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
24739 list is never matched.
24745 .section "Retry parameters" "SECID163"
24746 .cindex "retry" "parameters in rules"
24747 The third (or fourth, if a senders list is present) field in a retry rule is a
24748 sequence of retry parameter sets, separated by semicolons. Each set consists of
24750 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
24752 The letter identifies the algorithm for computing a new retry time; the cutoff
24753 time is the time beyond which this algorithm no longer applies, and the
24754 arguments vary the algorithm's action. The cutoff time is measured from the
24755 time that the first failure for the domain (combined with the local part if
24756 relevant) was detected, not from the time the message was received.
24758 .cindex "retry" "algorithms"
24759 .cindex "retry" "fixed intervals"
24760 .cindex "retry" "increasing intervals"
24761 .cindex "retry" "random intervals"
24762 The available algorithms are:
24765 &'F'&: retry at fixed intervals. There is a single time parameter specifying
24768 &'G'&: retry at geometrically increasing intervals. The first argument
24769 specifies a starting value for the interval, and the second a multiplier, which
24770 is used to increase the size of the interval at each retry.
24772 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
24773 retry, the previous interval is multiplied by the factor in order to get a
24774 maximum for the next interval. The minimum interval is the first argument of
24775 the parameter, and an actual interval is chosen randomly between them. Such a
24776 rule has been found to be helpful in cluster configurations when all the
24777 members of the cluster restart at once, and may therefore synchronize their
24778 queue processing times.
24781 When computing the next retry time, the algorithm definitions are scanned in
24782 order until one whose cutoff time has not yet passed is reached. This is then
24783 used to compute a new retry time that is later than the current time. In the
24784 case of fixed interval retries, this simply means adding the interval to the
24785 current time. For geometrically increasing intervals, retry intervals are
24786 computed from the rule's parameters until one that is greater than the previous
24787 interval is found. The main configuration variable
24788 .cindex "limit" "retry interval"
24789 .cindex "retry" "interval, maximum"
24790 .oindex "&%retry_interval_max%&"
24791 &%retry_interval_max%& limits the maximum interval between retries. It
24792 cannot be set greater than &`24h`&, which is its default value.
24794 A single remote domain may have a number of hosts associated with it, and each
24795 host may have more than one IP address. Retry algorithms are selected on the
24796 basis of the domain name, but are applied to each IP address independently. If,
24797 for example, a host has two IP addresses and one is unusable, Exim will
24798 generate retry times for it and will not try to use it until its next retry
24799 time comes. Thus the good IP address is likely to be tried first most of the
24802 .cindex "hints database" "use for retrying"
24803 Retry times are hints rather than promises. Exim does not make any attempt to
24804 run deliveries exactly at the computed times. Instead, a queue runner process
24805 starts delivery processes for delayed messages periodically, and these attempt
24806 new deliveries only for those addresses that have passed their next retry time.
24807 If a new message arrives for a deferred address, an immediate delivery attempt
24808 occurs only if the address has passed its retry time. In the absence of new
24809 messages, the minimum time between retries is the interval between queue runner
24810 processes. There is not much point in setting retry times of five minutes if
24811 your queue runners happen only once an hour, unless there are a significant
24812 number of incoming messages (which might be the case on a system that is
24813 sending everything to a smart host, for example).
24815 The data in the retry hints database can be inspected by using the
24816 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
24817 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
24818 &'exinext'& utility script can be used to find out what the next retry times
24819 are for the hosts associated with a particular mail domain, and also for local
24820 deliveries that have been deferred.
24823 .section "Retry rule examples" "SECID164"
24824 Here are some example retry rules:
24826 alice@wonderland.fict.example quota_5d F,7d,3h
24827 wonderland.fict.example quota_5d
24828 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
24829 lookingglass.fict.example * F,24h,30m;
24830 * refused_A F,2h,20m;
24831 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
24833 The first rule sets up special handling for mail to
24834 &'alice@wonderland.fict.example'& when there is an over-quota error and the
24835 mailbox has not been read for at least 5 days. Retries continue every three
24836 hours for 7 days. The second rule handles over-quota errors for all other local
24837 parts at &'wonderland.fict.example'&; the absence of a local part has the same
24838 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
24839 fail are bounced immediately if the mailbox has not been read for at least 5
24842 The third rule handles all other errors at &'wonderland.fict.example'&; retries
24843 happen every 15 minutes for an hour, then with geometrically increasing
24844 intervals until two days have passed since a delivery first failed. After the
24845 first hour there is a delay of one hour, then two hours, then four hours, and
24846 so on (this is a rather extreme example).
24848 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
24849 They happen every 30 minutes for 24 hours only. The remaining two rules handle
24850 all other domains, with special action for connection refusal from hosts that
24851 were not obtained from an MX record.
24853 The final rule in a retry configuration should always have asterisks in the
24854 first two fields so as to provide a general catch-all for any addresses that do
24855 not have their own special handling. This example tries every 15 minutes for 2
24856 hours, then with intervals starting at one hour and increasing by a factor of
24857 1.5 up to 16 hours, then every 8 hours up to 5 days.
24861 .section "Timeout of retry data" "SECID165"
24862 .cindex "timeout" "of retry data"
24863 .oindex "&%retry_data_expire%&"
24864 .cindex "hints database" "data expiry"
24865 .cindex "retry" "timeout of data"
24866 Exim timestamps the data that it writes to its retry hints database. When it
24867 consults the data during a delivery it ignores any that is older than the value
24868 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
24869 been tried for 7 days, Exim will try to deliver to it immediately a message
24870 arrives, and if that fails, it will calculate a retry time as if it were
24871 failing for the first time.
24873 This improves the behaviour for messages routed to rarely-used hosts such as MX
24874 backups. If such a host was down at one time, and happens to be down again when
24875 Exim tries a month later, using the old retry data would imply that it had been
24876 down all the time, which is not a justified assumption.
24878 If a host really is permanently dead, this behaviour causes a burst of retries
24879 every now and again, but only if messages routed to it are rare. If there is a
24880 message at least once every 7 days the retry data never expires.
24885 .section "Long-term failures" "SECID166"
24886 .cindex "delivery failure, long-term"
24887 .cindex "retry" "after long-term failure"
24888 Special processing happens when an email address has been failing for so long
24889 that the cutoff time for the last algorithm is reached. For example, using the
24890 default retry rule:
24892 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
24894 the cutoff time is four days. Reaching the retry cutoff is independent of how
24895 long any specific message has been failing; it is the length of continuous
24896 failure for the recipient address that counts.
24898 When the cutoff time is reached for a local delivery, or for all the IP
24899 addresses associated with a remote delivery, a subsequent delivery failure
24900 causes Exim to give up on the address, and a bounce message is generated.
24901 In order to cater for new messages that use the failing address, a next retry
24902 time is still computed from the final algorithm, and is used as follows:
24904 For local deliveries, one delivery attempt is always made for any subsequent
24905 messages. If this delivery fails, the address fails immediately. The
24906 post-cutoff retry time is not used.
24908 If the delivery is remote, there are two possibilities, controlled by the
24909 .oindex "&%delay_after_cutoff%&"
24910 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
24911 default. Until the post-cutoff retry time for one of the IP addresses is
24912 reached, the failing email address is bounced immediately, without a delivery
24913 attempt taking place. After that time, one new delivery attempt is made to
24914 those IP addresses that are past their retry times, and if that still fails,
24915 the address is bounced and new retry times are computed.
24917 In other words, when all the hosts for a given email address have been failing
24918 for a long time, Exim bounces rather then defers until one of the hosts' retry
24919 times is reached. Then it tries once, and bounces if that attempt fails. This
24920 behaviour ensures that few resources are wasted in repeatedly trying to deliver
24921 to a broken destination, but if the host does recover, Exim will eventually
24924 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
24925 addresses are past their final cutoff time, Exim tries to deliver to those IP
24926 addresses that have not been tried since the message arrived. If there are
24927 no suitable IP addresses, or if they all fail, the address is bounced. In other
24928 words, it does not delay when a new message arrives, but tries the expired
24929 addresses immediately, unless they have been tried since the message arrived.
24930 If there is a continuous stream of messages for the failing domains, setting
24931 &%delay_after_cutoff%& false means that there will be many more attempts to
24932 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
24935 .section "Deliveries that work intermittently" "SECID167"
24936 .cindex "retry" "intermittently working deliveries"
24937 Some additional logic is needed to cope with cases where a host is
24938 intermittently available, or when a message has some attribute that prevents
24939 its delivery when others to the same address get through. In this situation,
24940 because some messages are successfully delivered, the &"retry clock"& for the
24941 host or address keeps getting reset by the successful deliveries, and so
24942 failing messages remain on the queue for ever because the cutoff time is never
24945 Two exceptional actions are applied to prevent this happening. The first
24946 applies to errors that are related to a message rather than a remote host.
24947 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
24948 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
24949 commands, and quota failures. For this type of error, if a message's arrival
24950 time is earlier than the &"first failed"& time for the error, the earlier time
24951 is used when scanning the retry rules to decide when to try next and when to
24952 time out the address.
24954 The exceptional second action applies in all cases. If a message has been on
24955 the queue for longer than the cutoff time of any applicable retry rule for a
24956 given address, a delivery is attempted for that address, even if it is not yet
24957 time, and if this delivery fails, the address is timed out. A new retry time is
24958 not computed in this case, so that other messages for the same address are
24959 considered immediately.
24960 .ecindex IIDretconf1
24961 .ecindex IIDregconf2
24968 . ////////////////////////////////////////////////////////////////////////////
24969 . ////////////////////////////////////////////////////////////////////////////
24971 .chapter "SMTP authentication" "CHAPSMTPAUTH"
24972 .scindex IIDauthconf1 "SMTP" "authentication configuration"
24973 .scindex IIDauthconf2 "authentication"
24974 The &"authenticators"& section of Exim's run time configuration is concerned
24975 with SMTP authentication. This facility is an extension to the SMTP protocol,
24976 described in RFC 2554, which allows a client SMTP host to authenticate itself
24977 to a server. This is a common way for a server to recognize clients that are
24978 permitted to use it as a relay. SMTP authentication is not of relevance to the
24979 transfer of mail between servers that have no managerial connection with each
24982 .cindex "AUTH" "description of"
24983 Very briefly, the way SMTP authentication works is as follows:
24986 The server advertises a number of authentication &'mechanisms'& in response to
24987 the client's EHLO command.
24989 The client issues an AUTH command, naming a specific mechanism. The command
24990 may, optionally, contain some authentication data.
24992 The server may issue one or more &'challenges'&, to which the client must send
24993 appropriate responses. In simple authentication mechanisms, the challenges are
24994 just prompts for user names and passwords. The server does not have to issue
24995 any challenges &-- in some mechanisms the relevant data may all be transmitted
24996 with the AUTH command.
24998 The server either accepts or denies authentication.
25000 If authentication succeeds, the client may optionally make use of the AUTH
25001 option on the MAIL command to pass an authenticated sender in subsequent
25002 mail transactions. Authentication lasts for the remainder of the SMTP
25005 If authentication fails, the client may give up, or it may try a different
25006 authentication mechanism, or it may try transferring mail over the
25007 unauthenticated connection.
25010 If you are setting up a client, and want to know which authentication
25011 mechanisms the server supports, you can use Telnet to connect to port 25 (the
25012 SMTP port) on the server, and issue an EHLO command. The response to this
25013 includes the list of supported mechanisms. For example:
25015 &`$ `&&*&`telnet server.example 25`&*&
25016 &`Trying 192.168.34.25...`&
25017 &`Connected to server.example.`&
25018 &`Escape character is '^]'.`&
25019 &`220 server.example ESMTP Exim 4.20 ...`&
25020 &*&`ehlo client.example`&*&
25021 &`250-server.example Hello client.example [10.8.4.5]`&
25022 &`250-SIZE 52428800`&
25027 The second-last line of this example output shows that the server supports
25028 authentication using the PLAIN mechanism. In Exim, the different authentication
25029 mechanisms are configured by specifying &'authenticator'& drivers. Like the
25030 routers and transports, which authenticators are included in the binary is
25031 controlled by build-time definitions. The following are currently available,
25032 included by setting
25035 AUTH_CYRUS_SASL=yes
25038 AUTH_HEIMDAL_GSSAPI=yes
25043 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
25044 authentication mechanism (RFC 2195), and the second provides an interface to
25045 the Cyrus SASL authentication library.
25046 The third is an interface to Dovecot's authentication system, delegating the
25047 work via a socket interface.
25048 The fourth provides an interface to the GNU SASL authentication library, which
25049 provides mechanisms but typically not data sources.
25050 The fifth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
25051 supporting setting a server keytab.
25052 The sixth can be configured to support
25053 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
25054 not formally documented, but used by several MUAs. The seventh authenticator
25055 supports Microsoft's &'Secure Password Authentication'& mechanism.
25056 The eighth is an Exim authenticator but not an SMTP one;
25057 instead it can use information from a TLS negotiation.
25059 The authenticators are configured using the same syntax as other drivers (see
25060 section &<<SECTfordricon>>&). If no authenticators are required, no
25061 authentication section need be present in the configuration file. Each
25062 authenticator can in principle have both server and client functions. When Exim
25063 is receiving SMTP mail, it is acting as a server; when it is sending out
25064 messages over SMTP, it is acting as a client. Authenticator configuration
25065 options are provided for use in both these circumstances.
25067 To make it clear which options apply to which situation, the prefixes
25068 &%server_%& and &%client_%& are used on option names that are specific to
25069 either the server or the client function, respectively. Server and client
25070 functions are disabled if none of their options are set. If an authenticator is
25071 to be used for both server and client functions, a single definition, using
25072 both sets of options, is required. For example:
25076 public_name = CRAM-MD5
25077 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
25079 client_secret = secret2
25081 The &%server_%& option is used when Exim is acting as a server, and the
25082 &%client_%& options when it is acting as a client.
25084 Descriptions of the individual authenticators are given in subsequent chapters.
25085 The remainder of this chapter covers the generic options for the
25086 authenticators, followed by general discussion of the way authentication works
25089 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
25090 per-mechanism basis. Please read carefully to determine which variables hold
25091 account labels such as usercodes and which hold passwords or other
25092 authenticating data.
25094 Note that some mechanisms support two different identifiers for accounts: the
25095 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
25096 and &'authz'& are commonly encountered. The American spelling is standard here.
25097 Conceptually, authentication data such as passwords are tied to the identifier
25098 used to authenticate; servers may have rules to permit one user to act as a
25099 second user, so that after login the session is treated as though that second
25100 user had logged in. That second user is the &'authorization id'&. A robust
25101 configuration might confirm that the &'authz'& field is empty or matches the
25102 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
25103 as verified data, the &'authz'& as an unverified request which the server might
25106 A &'realm'& is a text string, typically a domain name, presented by a server
25107 to a client to help it select an account and credentials to use. In some
25108 mechanisms, the client and server provably agree on the realm, but clients
25109 typically can not treat the realm as secure data to be blindly trusted.
25113 .section "Generic options for authenticators" "SECID168"
25114 .cindex "authentication" "generic options"
25115 .cindex "options" "generic; for authenticators"
25117 .option client_condition authenticators string&!! unset
25118 When Exim is authenticating as a client, it skips any authenticator whose
25119 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
25120 used, for example, to skip plain text authenticators when the connection is not
25121 encrypted by a setting such as:
25123 client_condition = ${if !eq{$tls_out_cipher}{}}
25127 .option client_set_id authenticators string&!! unset
25128 When client authentication succeeds, this condition is expanded; the
25129 result is used in the log lines for outbound messages.
25130 Typically it will be the user name used for authentication.
25133 .option driver authenticators string unset
25134 This option must always be set. It specifies which of the available
25135 authenticators is to be used.
25138 .option public_name authenticators string unset
25139 This option specifies the name of the authentication mechanism that the driver
25140 implements, and by which it is known to the outside world. These names should
25141 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
25142 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
25143 defaults to the driver's instance name.
25146 .option server_advertise_condition authenticators string&!! unset
25147 When a server is about to advertise an authentication mechanism, the condition
25148 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
25149 mechanism is not advertised.
25150 If the expansion fails, the mechanism is not advertised. If the failure was not
25151 forced, and was not caused by a lookup defer, the incident is logged.
25152 See section &<<SECTauthexiser>>& below for further discussion.
25155 .option server_condition authenticators string&!! unset
25156 This option must be set for a &%plaintext%& server authenticator, where it
25157 is used directly to control authentication. See section &<<SECTplainserver>>&
25160 For the &(gsasl)& authenticator, this option is required for various
25161 mechanisms; see chapter &<<CHAPgsasl>>& for details.
25163 For the other authenticators, &%server_condition%& can be used as an additional
25164 authentication or authorization mechanism that is applied after the other
25165 authenticator conditions succeed. If it is set, it is expanded when the
25166 authenticator would otherwise return a success code. If the expansion is forced
25167 to fail, authentication fails. Any other expansion failure causes a temporary
25168 error code to be returned. If the result of a successful expansion is an empty
25169 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
25170 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
25171 other result, a temporary error code is returned, with the expanded string as
25175 .option server_debug_print authenticators string&!! unset
25176 If this option is set and authentication debugging is enabled (see the &%-d%&
25177 command line option), the string is expanded and included in the debugging
25178 output when the authenticator is run as a server. This can help with checking
25179 out the values of variables.
25180 If expansion of the string fails, the error message is written to the debugging
25181 output, and Exim carries on processing.
25184 .option server_set_id authenticators string&!! unset
25185 .vindex "&$authenticated_id$&"
25186 When an Exim server successfully authenticates a client, this string is
25187 expanded using data from the authentication, and preserved for any incoming
25188 messages in the variable &$authenticated_id$&. It is also included in the log
25189 lines for incoming messages. For example, a user/password authenticator
25190 configuration might preserve the user name that was used to authenticate, and
25191 refer to it subsequently during delivery of the message.
25192 If expansion fails, the option is ignored.
25195 .option server_mail_auth_condition authenticators string&!! unset
25196 This option allows a server to discard authenticated sender addresses supplied
25197 as part of MAIL commands in SMTP connections that are authenticated by the
25198 driver on which &%server_mail_auth_condition%& is set. The option is not used
25199 as part of the authentication process; instead its (unexpanded) value is
25200 remembered for later use.
25201 How it is used is described in the following section.
25207 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
25208 .cindex "authentication" "sender; authenticated"
25209 .cindex "AUTH" "on MAIL command"
25210 When a client supplied an AUTH= item on a MAIL command, Exim applies
25211 the following checks before accepting it as the authenticated sender of the
25215 If the connection is not using extended SMTP (that is, HELO was used rather
25216 than EHLO), the use of AUTH= is a syntax error.
25218 If the value of the AUTH= parameter is &"<>"&, it is ignored.
25220 .vindex "&$authenticated_sender$&"
25221 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
25222 running, the value of &$authenticated_sender$& is set to the value obtained
25223 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
25224 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
25225 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
25226 given for the MAIL command.
25228 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
25229 is accepted and placed in &$authenticated_sender$& only if the client has
25232 If the AUTH= value was accepted by either of the two previous rules, and
25233 the client has authenticated, and the authenticator has a setting for the
25234 &%server_mail_auth_condition%&, the condition is checked at this point. The
25235 valued that was saved from the authenticator is expanded. If the expansion
25236 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
25237 &$authenticated_sender$& is deleted. If the expansion yields any other value,
25238 the value of &$authenticated_sender$& is retained and passed on with the
25243 When &$authenticated_sender$& is set for a message, it is passed on to other
25244 hosts to which Exim authenticates as a client. Do not confuse this value with
25245 &$authenticated_id$&, which is a string obtained from the authentication
25246 process, and which is not usually a complete email address.
25248 .vindex "&$sender_address$&"
25249 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
25250 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
25251 therefore make use of &$authenticated_sender$&. The converse is not true: the
25252 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
25257 .section "Authentication on an Exim server" "SECTauthexiser"
25258 .cindex "authentication" "on an Exim server"
25259 When Exim receives an EHLO command, it advertises the public names of those
25260 authenticators that are configured as servers, subject to the following
25264 The client host must match &%auth_advertise_hosts%& (default *).
25266 It the &%server_advertise_condition%& option is set, its expansion must not
25267 yield the empty string, &"0"&, &"no"&, or &"false"&.
25270 The order in which the authenticators are defined controls the order in which
25271 the mechanisms are advertised.
25273 Some mail clients (for example, some versions of Netscape) require the user to
25274 provide a name and password for authentication whenever AUTH is advertised,
25275 even though authentication may not in fact be needed (for example, Exim may be
25276 set up to allow unconditional relaying from the client by an IP address check).
25277 You can make such clients more friendly by not advertising AUTH to them.
25278 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
25279 that runs for RCPT) to relay without authentication, you should set
25281 auth_advertise_hosts = ! 10.9.8.0/24
25283 so that no authentication mechanisms are advertised to them.
25285 The &%server_advertise_condition%& controls the advertisement of individual
25286 authentication mechanisms. For example, it can be used to restrict the
25287 advertisement of a particular mechanism to encrypted connections, by a setting
25290 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
25292 .vindex "&$tls_in_cipher$&"
25293 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
25294 yields &"yes"&, which allows the advertisement to happen.
25296 When an Exim server receives an AUTH command from a client, it rejects it
25297 immediately if AUTH was not advertised in response to an earlier EHLO
25298 command. This is the case if
25301 The client host does not match &%auth_advertise_hosts%&; or
25303 No authenticators are configured with server options; or
25305 Expansion of &%server_advertise_condition%& blocked the advertising of all the
25306 server authenticators.
25310 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
25311 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
25312 AUTH is accepted from any client host.
25314 If AUTH is not rejected by the ACL, Exim searches its configuration for a
25315 server authentication mechanism that was advertised in response to EHLO and
25316 that matches the one named in the AUTH command. If it finds one, it runs
25317 the appropriate authentication protocol, and authentication either succeeds or
25318 fails. If there is no matching advertised mechanism, the AUTH command is
25319 rejected with a 504 error.
25321 .vindex "&$received_protocol$&"
25322 .vindex "&$sender_host_authenticated$&"
25323 When a message is received from an authenticated host, the value of
25324 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
25325 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
25326 public name) of the authenticator driver that successfully authenticated the
25327 client from which the message was received. This variable is empty if there was
25328 no successful authentication.
25333 .section "Testing server authentication" "SECID169"
25334 .cindex "authentication" "testing a server"
25335 .cindex "AUTH" "testing a server"
25336 .cindex "base64 encoding" "creating authentication test data"
25337 Exim's &%-bh%& option can be useful for testing server authentication
25338 configurations. The data for the AUTH command has to be sent using base64
25339 encoding. A quick way to produce such data for testing is the following Perl
25343 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
25345 .cindex "binary zero" "in authentication data"
25346 This interprets its argument as a Perl string, and then encodes it. The
25347 interpretation as a Perl string allows binary zeros, which are required for
25348 some kinds of authentication, to be included in the data. For example, a
25349 command line to run this script on such data might be
25351 encode '\0user\0password'
25353 Note the use of single quotes to prevent the shell interpreting the
25354 backslashes, so that they can be interpreted by Perl to specify characters
25355 whose code value is zero.
25357 &*Warning 1*&: If either of the user or password strings starts with an octal
25358 digit, you must use three zeros instead of one after the leading backslash. If
25359 you do not, the octal digit that starts your string will be incorrectly
25360 interpreted as part of the code for the first character.
25362 &*Warning 2*&: If there are characters in the strings that Perl interprets
25363 specially, you must use a Perl escape to prevent them being misinterpreted. For
25364 example, a command such as
25366 encode '\0user@domain.com\0pas$$word'
25368 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
25370 If you have the &%mimencode%& command installed, another way to do produce
25371 base64-encoded strings is to run the command
25373 echo -e -n `\0user\0password' | mimencode
25375 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
25376 in the argument, and the &%-n%& option specifies no newline at the end of its
25377 output. However, not all versions of &%echo%& recognize these options, so you
25378 should check your version before relying on this suggestion.
25382 .section "Authentication by an Exim client" "SECID170"
25383 .cindex "authentication" "on an Exim client"
25384 The &(smtp)& transport has two options called &%hosts_require_auth%& and
25385 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
25386 announces support for authentication, and the host matches an entry in either
25387 of these options, Exim (as a client) tries to authenticate as follows:
25390 For each authenticator that is configured as a client, in the order in which
25391 they are defined in the configuration, it searches the authentication
25392 mechanisms announced by the server for one whose name matches the public name
25393 of the authenticator.
25396 .vindex "&$host_address$&"
25397 When it finds one that matches, it runs the authenticator's client code. The
25398 variables &$host$& and &$host_address$& are available for any string expansions
25399 that the client might do. They are set to the server's name and IP address. If
25400 any expansion is forced to fail, the authentication attempt is abandoned, and
25401 Exim moves on to the next authenticator. Otherwise an expansion failure causes
25402 delivery to be deferred.
25404 If the result of the authentication attempt is a temporary error or a timeout,
25405 Exim abandons trying to send the message to the host for the moment. It will
25406 try again later. If there are any backup hosts available, they are tried in the
25409 If the response to authentication is a permanent error (5&'xx'& code), Exim
25410 carries on searching the list of authenticators and tries another one if
25411 possible. If all authentication attempts give permanent errors, or if there are
25412 no attempts because no mechanisms match (or option expansions force failure),
25413 what happens depends on whether the host matches &%hosts_require_auth%& or
25414 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
25415 delivery is deferred. The error can be detected in the retry rules, and thereby
25416 turned into a permanent error if you wish. In the second case, Exim tries to
25417 deliver the message unauthenticated.
25420 .cindex "AUTH" "on MAIL command"
25421 When Exim has authenticated itself to a remote server, it adds the AUTH
25422 parameter to the MAIL commands it sends, if it has an authenticated sender for
25423 the message. If the message came from a remote host, the authenticated sender
25424 is the one that was receiving on an incoming MAIL command, provided that the
25425 incoming connection was authenticated and the &%server_mail_auth%& condition
25426 allowed the authenticated sender to be retained. If a local process calls Exim
25427 to send a message, the sender address that is built from the login name and
25428 &%qualify_domain%& is treated as authenticated. However, if the
25429 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
25430 the authenticated sender that was received with the message.
25431 .ecindex IIDauthconf1
25432 .ecindex IIDauthconf2
25439 . ////////////////////////////////////////////////////////////////////////////
25440 . ////////////////////////////////////////////////////////////////////////////
25442 .chapter "The plaintext authenticator" "CHAPplaintext"
25443 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
25444 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
25445 The &(plaintext)& authenticator can be configured to support the PLAIN and
25446 LOGIN authentication mechanisms, both of which transfer authentication data as
25447 plain (unencrypted) text (though base64 encoded). The use of plain text is a
25448 security risk; you are strongly advised to insist on the use of SMTP encryption
25449 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
25450 use unencrypted plain text, you should not use the same passwords for SMTP
25451 connections as you do for login accounts.
25453 .section "Plaintext options" "SECID171"
25454 .cindex "options" "&(plaintext)& authenticator (server)"
25455 When configured as a server, &(plaintext)& uses the following options:
25457 .option server_condition authenticators string&!! unset
25458 This is actually a global authentication option, but it must be set in order to
25459 configure the &(plaintext)& driver as a server. Its use is described below.
25461 .option server_prompts plaintext string&!! unset
25462 The contents of this option, after expansion, must be a colon-separated list of
25463 prompt strings. If expansion fails, a temporary authentication rejection is
25466 .section "Using plaintext in a server" "SECTplainserver"
25467 .cindex "AUTH" "in &(plaintext)& authenticator"
25468 .cindex "binary zero" "in &(plaintext)& authenticator"
25469 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
25470 "in &(plaintext)& authenticator"
25471 .vindex "&$auth1$&, &$auth2$&, etc"
25472 .cindex "base64 encoding" "in &(plaintext)& authenticator"
25474 When running as a server, &(plaintext)& performs the authentication test by
25475 expanding a string. The data sent by the client with the AUTH command, or in
25476 response to subsequent prompts, is base64 encoded, and so may contain any byte
25477 values when decoded. If any data is supplied with the command, it is treated as
25478 a list of strings, separated by NULs (binary zeros), the first three of which
25479 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
25480 (neither LOGIN nor PLAIN uses more than three strings).
25482 For compatibility with previous releases of Exim, the values are also placed in
25483 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
25484 variables for this purpose is now deprecated, as it can lead to confusion in
25485 string expansions that also use them for other things.
25487 If there are more strings in &%server_prompts%& than the number of strings
25488 supplied with the AUTH command, the remaining prompts are used to obtain more
25489 data. Each response from the client may be a list of NUL-separated strings.
25491 .vindex "&$authenticated_id$&"
25492 Once a sufficient number of data strings have been received,
25493 &%server_condition%& is expanded. If the expansion is forced to fail,
25494 authentication fails. Any other expansion failure causes a temporary error code
25495 to be returned. If the result of a successful expansion is an empty string,
25496 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
25497 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
25498 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
25499 For any other result, a temporary error code is returned, with the expanded
25500 string as the error text
25502 &*Warning*&: If you use a lookup in the expansion to find the user's
25503 password, be sure to make the authentication fail if the user is unknown.
25504 There are good and bad examples at the end of the next section.
25508 .section "The PLAIN authentication mechanism" "SECID172"
25509 .cindex "PLAIN authentication mechanism"
25510 .cindex "authentication" "PLAIN mechanism"
25511 .cindex "binary zero" "in &(plaintext)& authenticator"
25512 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
25513 sent as one item of data (that is, one combined string containing two NUL
25514 separators). The data is sent either as part of the AUTH command, or
25515 subsequently in response to an empty prompt from the server.
25517 The second and third strings are a user name and a corresponding password.
25518 Using a single fixed user name and password as an example, this could be
25519 configured as follows:
25523 public_name = PLAIN
25525 server_condition = \
25526 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
25527 server_set_id = $auth2
25529 Note that the default result strings from &%if%& (&"true"& or an empty string)
25530 are exactly what we want here, so they need not be specified. Obviously, if the
25531 password contains expansion-significant characters such as dollar, backslash,
25532 or closing brace, they have to be escaped.
25534 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
25535 the end of a string list are ignored). If all the data comes as part of the
25536 AUTH command, as is commonly the case, the prompt is not used. This
25537 authenticator is advertised in the response to EHLO as
25541 and a client host can authenticate itself by sending the command
25543 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
25545 As this contains three strings (more than the number of prompts), no further
25546 data is required from the client. Alternatively, the client may just send
25550 to initiate authentication, in which case the server replies with an empty
25551 prompt. The client must respond with the combined data string.
25553 The data string is base64 encoded, as required by the RFC. This example,
25554 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
25555 represents a zero byte. This is split up into three strings, the first of which
25556 is empty. The &%server_condition%& option in the authenticator checks that the
25557 second two are &`username`& and &`mysecret`& respectively.
25559 Having just one fixed user name and password, as in this example, is not very
25560 realistic, though for a small organization with only a handful of
25561 authenticating clients it could make sense.
25563 A more sophisticated instance of this authenticator could use the user name in
25564 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
25565 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
25566 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
25567 This is an incorrect example:
25569 server_condition = \
25570 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
25572 The expansion uses the user name (&$auth2$&) as the key to look up a password,
25573 which it then compares to the supplied password (&$auth3$&). Why is this example
25574 incorrect? It works fine for existing users, but consider what happens if a
25575 non-existent user name is given. The lookup fails, but as no success/failure
25576 strings are given for the lookup, it yields an empty string. Thus, to defeat
25577 the authentication, all a client has to do is to supply a non-existent user
25578 name and an empty password. The correct way of writing this test is:
25580 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
25581 {${if eq{$value}{$auth3}}} {false}}
25583 In this case, if the lookup succeeds, the result is checked; if the lookup
25584 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
25585 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
25586 always fails if its second argument is empty. However, the second way of
25587 writing the test makes the logic clearer.
25590 .section "The LOGIN authentication mechanism" "SECID173"
25591 .cindex "LOGIN authentication mechanism"
25592 .cindex "authentication" "LOGIN mechanism"
25593 The LOGIN authentication mechanism is not documented in any RFC, but is in use
25594 in a number of programs. No data is sent with the AUTH command. Instead, a
25595 user name and password are supplied separately, in response to prompts. The
25596 plaintext authenticator can be configured to support this as in this example:
25600 public_name = LOGIN
25601 server_prompts = User Name : Password
25602 server_condition = \
25603 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
25604 server_set_id = $auth1
25606 Because of the way plaintext operates, this authenticator accepts data supplied
25607 with the AUTH command (in contravention of the specification of LOGIN), but
25608 if the client does not supply it (as is the case for LOGIN clients), the prompt
25609 strings are used to obtain two data items.
25611 Some clients are very particular about the precise text of the prompts. For
25612 example, Outlook Express is reported to recognize only &"Username:"& and
25613 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
25614 strings. It uses the &%ldapauth%& expansion condition to check the user
25615 name and password by binding to an LDAP server:
25619 public_name = LOGIN
25620 server_prompts = Username:: : Password::
25621 server_condition = ${if and{{ \
25624 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
25625 pass=${quote:$auth2} \
25626 ldap://ldap.example.org/} }} }
25627 server_set_id = uid=$auth1,ou=people,o=example.org
25629 We have to check that the username is not empty before using it, because LDAP
25630 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
25631 operator to correctly quote the DN for authentication. However, the basic
25632 &%quote%& operator, rather than any of the LDAP quoting operators, is the
25633 correct one to use for the password, because quoting is needed only to make
25634 the password conform to the Exim syntax. At the LDAP level, the password is an
25635 uninterpreted string.
25638 .section "Support for different kinds of authentication" "SECID174"
25639 A number of string expansion features are provided for the purpose of
25640 interfacing to different ways of user authentication. These include checking
25641 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
25642 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
25648 .section "Using plaintext in a client" "SECID175"
25649 .cindex "options" "&(plaintext)& authenticator (client)"
25650 The &(plaintext)& authenticator has two client options:
25652 .option client_ignore_invalid_base64 plaintext boolean false
25653 If the client receives a server prompt that is not a valid base64 string,
25654 authentication is abandoned by default. However, if this option is set true,
25655 the error in the challenge is ignored and the client sends the response as
25658 .option client_send plaintext string&!! unset
25659 The string is a colon-separated list of authentication data strings. Each
25660 string is independently expanded before being sent to the server. The first
25661 string is sent with the AUTH command; any more strings are sent in response
25662 to prompts from the server. Before each string is expanded, the value of the
25663 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
25664 with &$auth1$& for the first prompt. Up to three prompts are stored in this
25665 way. Thus, the prompt that is received in response to sending the first string
25666 (with the AUTH command) can be used in the expansion of the second string, and
25667 so on. If an invalid base64 string is received when
25668 &%client_ignore_invalid_base64%& is set, an empty string is put in the
25669 &$auth$&<&'n'&> variable.
25671 &*Note*&: You cannot use expansion to create multiple strings, because
25672 splitting takes priority and happens first.
25674 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
25675 the data, further processing is applied to each string before it is sent. If
25676 there are any single circumflex characters in the string, they are converted to
25677 NULs. Should an actual circumflex be required as data, it must be doubled in
25680 This is an example of a client configuration that implements the PLAIN
25681 authentication mechanism with a fixed user name and password:
25685 public_name = PLAIN
25686 client_send = ^username^mysecret
25688 The lack of colons means that the entire text is sent with the AUTH
25689 command, with the circumflex characters converted to NULs. A similar example
25690 that uses the LOGIN mechanism is:
25694 public_name = LOGIN
25695 client_send = : username : mysecret
25697 The initial colon means that the first string is empty, so no data is sent with
25698 the AUTH command itself. The remaining strings are sent in response to
25700 .ecindex IIDplaiauth1
25701 .ecindex IIDplaiauth2
25706 . ////////////////////////////////////////////////////////////////////////////
25707 . ////////////////////////////////////////////////////////////////////////////
25709 .chapter "The cram_md5 authenticator" "CHID9"
25710 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
25711 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
25712 .cindex "CRAM-MD5 authentication mechanism"
25713 .cindex "authentication" "CRAM-MD5 mechanism"
25714 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
25715 sends a challenge string to the client, and the response consists of a user
25716 name and the CRAM-MD5 digest of the challenge string combined with a secret
25717 string (password) which is known to both server and client. Thus, the secret
25718 is not sent over the network as plain text, which makes this authenticator more
25719 secure than &(plaintext)&. However, the downside is that the secret has to be
25720 available in plain text at either end.
25723 .section "Using cram_md5 as a server" "SECID176"
25724 .cindex "options" "&(cram_md5)& authenticator (server)"
25725 This authenticator has one server option, which must be set to configure the
25726 authenticator as a server:
25728 .option server_secret cram_md5 string&!! unset
25729 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
25730 When the server receives the client's response, the user name is placed in
25731 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
25732 obtain the password for that user. The server then computes the CRAM-MD5 digest
25733 that the client should have sent, and checks that it received the correct
25734 string. If the expansion of &%server_secret%& is forced to fail, authentication
25735 fails. If the expansion fails for some other reason, a temporary error code is
25736 returned to the client.
25738 For compatibility with previous releases of Exim, the user name is also placed
25739 in &$1$&. However, the use of this variables for this purpose is now
25740 deprecated, as it can lead to confusion in string expansions that also use
25741 numeric variables for other things.
25743 For example, the following authenticator checks that the user name given by the
25744 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
25745 user name, authentication fails.
25749 public_name = CRAM-MD5
25750 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
25751 server_set_id = $auth1
25753 .vindex "&$authenticated_id$&"
25754 If authentication succeeds, the setting of &%server_set_id%& preserves the user
25755 name in &$authenticated_id$&. A more typical configuration might look up the
25756 secret string in a file, using the user name as the key. For example:
25760 public_name = CRAM-MD5
25761 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
25763 server_set_id = $auth1
25765 Note that this expansion explicitly forces failure if the lookup fails
25766 because &$auth1$& contains an unknown user name.
25768 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
25769 using the relevant libraries, you need to know the realm to specify in the
25770 lookup and then ask for the &"userPassword"& attribute for that user in that
25775 public_name = CRAM-MD5
25776 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
25777 dbmjz{/etc/sasldb2}{$value}fail}
25778 server_set_id = $auth1
25781 .section "Using cram_md5 as a client" "SECID177"
25782 .cindex "options" "&(cram_md5)& authenticator (client)"
25783 When used as a client, the &(cram_md5)& authenticator has two options:
25787 .option client_name cram_md5 string&!! "the primary host name"
25788 This string is expanded, and the result used as the user name data when
25789 computing the response to the server's challenge.
25792 .option client_secret cram_md5 string&!! unset
25793 This option must be set for the authenticator to work as a client. Its value is
25794 expanded and the result used as the secret string when computing the response.
25798 .vindex "&$host_address$&"
25799 Different user names and secrets can be used for different servers by referring
25800 to &$host$& or &$host_address$& in the options. Forced failure of either
25801 expansion string is treated as an indication that this authenticator is not
25802 prepared to handle this case. Exim moves on to the next configured client
25803 authenticator. Any other expansion failure causes Exim to give up trying to
25804 send the message to the current server.
25806 A simple example configuration of a &(cram_md5)& authenticator, using fixed
25811 public_name = CRAM-MD5
25813 client_secret = secret
25815 .ecindex IIDcramauth1
25816 .ecindex IIDcramauth2
25820 . ////////////////////////////////////////////////////////////////////////////
25821 . ////////////////////////////////////////////////////////////////////////////
25823 .chapter "The cyrus_sasl authenticator" "CHID10"
25824 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
25825 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
25826 .cindex "Cyrus" "SASL library"
25828 The code for this authenticator was provided by Matthew Byng-Maddick of A L
25829 Digital Ltd (&url(http://www.aldigital.co.uk)).
25831 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
25832 library implementation of the RFC 2222 (&"Simple Authentication and Security
25833 Layer"&). This library supports a number of authentication mechanisms,
25834 including PLAIN and LOGIN, but also several others that Exim does not support
25835 directly. In particular, there is support for Kerberos authentication.
25837 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
25838 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
25839 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
25840 name of the driver to determine which mechanism to support.
25842 Where access to some kind of secret file is required, for example in GSSAPI
25843 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
25844 user, and that the Cyrus SASL library has no way of escalating privileges
25845 by default. You may also find you need to set environment variables,
25846 depending on the driver you are using.
25848 The application name provided by Exim is &"exim"&, so various SASL options may
25849 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
25850 Kerberos, note that because of limitations in the GSSAPI interface,
25851 changing the server keytab might need to be communicated down to the Kerberos
25852 layer independently. The mechanism for doing so is dependent upon the Kerberos
25855 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
25856 may be set to point to an alternative keytab file. Exim will pass this
25857 variable through from its own inherited environment when started as root or the
25858 Exim user. The keytab file needs to be readable by the Exim user.
25859 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
25860 environment variable. In practice, for those releases, the Cyrus authenticator
25861 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
25862 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
25865 .section "Using cyrus_sasl as a server" "SECID178"
25866 The &(cyrus_sasl)& authenticator has four private options. It puts the username
25867 (on a successful authentication) into &$auth1$&. For compatibility with
25868 previous releases of Exim, the username is also placed in &$1$&. However, the
25869 use of this variable for this purpose is now deprecated, as it can lead to
25870 confusion in string expansions that also use numeric variables for other
25874 .option server_hostname cyrus_sasl string&!! "see below"
25875 This option selects the hostname that is used when communicating with the
25876 library. The default value is &`$primary_hostname`&. It is up to the underlying
25877 SASL plug-in what it does with this data.
25880 .option server_mech cyrus_sasl string "see below"
25881 This option selects the authentication mechanism this driver should use. The
25882 default is the value of the generic &%public_name%& option. This option allows
25883 you to use a different underlying mechanism from the advertised name. For
25887 driver = cyrus_sasl
25888 public_name = X-ANYTHING
25889 server_mech = CRAM-MD5
25890 server_set_id = $auth1
25893 .option server_realm cyrus_sasl string&!! unset
25894 This specifies the SASL realm that the server claims to be in.
25897 .option server_service cyrus_sasl string &`smtp`&
25898 This is the SASL service that the server claims to implement.
25901 For straightforward cases, you do not need to set any of the authenticator's
25902 private options. All you need to do is to specify an appropriate mechanism as
25903 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
25904 PLAIN, you could have two authenticators as follows:
25907 driver = cyrus_sasl
25908 public_name = CRAM-MD5
25909 server_set_id = $auth1
25912 driver = cyrus_sasl
25913 public_name = PLAIN
25914 server_set_id = $auth2
25916 Cyrus SASL does implement the LOGIN authentication method, even though it is
25917 not a standard method. It is disabled by default in the source distribution,
25918 but it is present in many binary distributions.
25919 .ecindex IIDcyrauth1
25920 .ecindex IIDcyrauth2
25925 . ////////////////////////////////////////////////////////////////////////////
25926 . ////////////////////////////////////////////////////////////////////////////
25927 .chapter "The dovecot authenticator" "CHAPdovecot"
25928 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
25929 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
25930 This authenticator is an interface to the authentication facility of the
25931 Dovecot POP/IMAP server, which can support a number of authentication methods.
25932 Note that Dovecot must be configured to use auth-client not auth-userdb.
25933 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
25934 to use the same mechanisms for SMTP authentication. This is a server
25935 authenticator only. There is only one option:
25937 .option server_socket dovecot string unset
25939 This option must specify the socket that is the interface to Dovecot
25940 authentication. The &%public_name%& option must specify an authentication
25941 mechanism that Dovecot is configured to support. You can have several
25942 authenticators for different mechanisms. For example:
25946 public_name = PLAIN
25947 server_socket = /var/run/dovecot/auth-client
25948 server_set_id = $auth1
25953 server_socket = /var/run/dovecot/auth-client
25954 server_set_id = $auth1
25956 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
25957 &$received_ip_address$& (that is, the connection is local), the &"secured"&
25958 option is passed in the Dovecot authentication command. If, for a TLS
25959 connection, a client certificate has been verified, the &"valid-client-cert"&
25960 option is passed. When authentication succeeds, the identity of the user
25961 who authenticated is placed in &$auth1$&.
25962 .ecindex IIDdcotauth1
25963 .ecindex IIDdcotauth2
25966 . ////////////////////////////////////////////////////////////////////////////
25967 . ////////////////////////////////////////////////////////////////////////////
25968 .chapter "The gsasl authenticator" "CHAPgsasl"
25969 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
25970 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
25971 .cindex "authentication" "GNU SASL"
25972 .cindex "authentication" "SASL"
25973 .cindex "authentication" "EXTERNAL"
25974 .cindex "authentication" "ANONYMOUS"
25975 .cindex "authentication" "PLAIN"
25976 .cindex "authentication" "LOGIN"
25977 .cindex "authentication" "DIGEST-MD5"
25978 .cindex "authentication" "CRAM-MD5"
25979 .cindex "authentication" "SCRAM-SHA-1"
25980 The &(gsasl)& authenticator provides server integration for the GNU SASL
25981 library and the mechanisms it provides. This is new as of the 4.80 release
25982 and there are a few areas where the library does not let Exim smoothly
25983 scale to handle future authentication mechanisms, so no guarantee can be
25984 made that any particular new authentication mechanism will be supported
25985 without code changes in Exim.
25988 .option server_channelbinding gsasl boolean false
25989 Some authentication mechanisms are able to use external context at both ends
25990 of the session to bind the authentication to that context, and fail the
25991 authentication process if that context differs. Specifically, some TLS
25992 ciphersuites can provide identifying information about the cryptographic
25995 This means that certificate identity and verification becomes a non-issue,
25996 as a man-in-the-middle attack will cause the correct client and server to
25997 see different identifiers and authentication will fail.
25999 This is currently only supported when using the GnuTLS library. This is
26000 only usable by mechanisms which support "channel binding"; at time of
26001 writing, that's the SCRAM family.
26003 This defaults off to ensure smooth upgrade across Exim releases, in case
26004 this option causes some clients to start failing. Some future release
26005 of Exim may switch the default to be true.
26008 .option server_hostname gsasl string&!! "see below"
26009 This option selects the hostname that is used when communicating with the
26010 library. The default value is &`$primary_hostname`&.
26011 Some mechanisms will use this data.
26014 .option server_mech gsasl string "see below"
26015 This option selects the authentication mechanism this driver should use. The
26016 default is the value of the generic &%public_name%& option. This option allows
26017 you to use a different underlying mechanism from the advertised name. For
26022 public_name = X-ANYTHING
26023 server_mech = CRAM-MD5
26024 server_set_id = $auth1
26028 .option server_password gsasl string&!! unset
26029 Various mechanisms need access to the cleartext password on the server, so
26030 that proof-of-possession can be demonstrated on the wire, without sending
26031 the password itself.
26033 The data available for lookup varies per mechanism.
26034 In all cases, &$auth1$& is set to the &'authentication id'&.
26035 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
26036 if available, else the empty string.
26037 The &$auth3$& variable will always be the &'realm'& if available,
26038 else the empty string.
26040 A forced failure will cause authentication to defer.
26042 If using this option, it may make sense to set the &%server_condition%&
26043 option to be simply "true".
26046 .option server_realm gsasl string&!! unset
26047 This specifies the SASL realm that the server claims to be in.
26048 Some mechanisms will use this data.
26051 .option server_scram_iter gsasl string&!! unset
26052 This option provides data for the SCRAM family of mechanisms.
26053 &$auth1$& is not available at evaluation time.
26054 (This may change, as we receive feedback on use)
26057 .option server_scram_salt gsasl string&!! unset
26058 This option provides data for the SCRAM family of mechanisms.
26059 &$auth1$& is not available at evaluation time.
26060 (This may change, as we receive feedback on use)
26063 .option server_service gsasl string &`smtp`&
26064 This is the SASL service that the server claims to implement.
26065 Some mechanisms will use this data.
26068 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
26069 .vindex "&$auth1$&, &$auth2$&, etc"
26070 These may be set when evaluating specific options, as detailed above.
26071 They will also be set when evaluating &%server_condition%&.
26073 Unless otherwise stated below, the &(gsasl)& integration will use the following
26074 meanings for these variables:
26077 .vindex "&$auth1$&"
26078 &$auth1$&: the &'authentication id'&
26080 .vindex "&$auth2$&"
26081 &$auth2$&: the &'authorization id'&
26083 .vindex "&$auth3$&"
26084 &$auth3$&: the &'realm'&
26087 On a per-mechanism basis:
26090 .cindex "authentication" "EXTERNAL"
26091 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
26092 the &%server_condition%& option must be present.
26094 .cindex "authentication" "ANONYMOUS"
26095 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
26096 the &%server_condition%& option must be present.
26098 .cindex "authentication" "GSSAPI"
26099 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
26100 &$auth2$& will be set to the &'authorization id'&,
26101 the &%server_condition%& option must be present.
26104 An &'anonymous token'& is something passed along as an unauthenticated
26105 identifier; this is analogous to FTP anonymous authentication passing an
26106 email address, or software-identifier@, as the "password".
26109 An example showing the password having the realm specified in the callback
26110 and demonstrating a Cyrus SASL to GSASL migration approach is:
26112 gsasl_cyrusless_crammd5:
26114 public_name = CRAM-MD5
26115 server_realm = imap.example.org
26116 server_password = ${lookup{$auth1:$auth3:userPassword}\
26117 dbmjz{/etc/sasldb2}{$value}fail}
26118 server_set_id = ${quote:$auth1}
26119 server_condition = yes
26123 . ////////////////////////////////////////////////////////////////////////////
26124 . ////////////////////////////////////////////////////////////////////////////
26126 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
26127 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
26128 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
26129 .cindex "authentication" "GSSAPI"
26130 .cindex "authentication" "Kerberos"
26131 The &(heimdal_gssapi)& authenticator provides server integration for the
26132 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
26135 .option server_hostname heimdal_gssapi string&!! "see below"
26136 This option selects the hostname that is used, with &%server_service%&,
26137 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
26138 identifier. The default value is &`$primary_hostname`&.
26140 .option server_keytab heimdal_gssapi string&!! unset
26141 If set, then Heimdal will not use the system default keytab (typically
26142 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
26143 The value should be a pathname, with no &"file:"& prefix.
26145 .option server_service heimdal_gssapi string&!! "smtp"
26146 This option specifies the service identifier used, in conjunction with
26147 &%server_hostname%&, for building the identifier for finding credentials
26151 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
26152 Beware that these variables will typically include a realm, thus will appear
26153 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
26154 not verified, so a malicious client can set it to anything.
26156 The &$auth1$& field should be safely trustable as a value from the Key
26157 Distribution Center. Note that these are not quite email addresses.
26158 Each identifier is for a role, and so the left-hand-side may include a
26159 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
26161 .vindex "&$auth1$&, &$auth2$&, etc"
26163 .vindex "&$auth1$&"
26164 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
26166 .vindex "&$auth2$&"
26167 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
26168 authentication. If that was empty, this will also be set to the
26173 . ////////////////////////////////////////////////////////////////////////////
26174 . ////////////////////////////////////////////////////////////////////////////
26176 .chapter "The spa authenticator" "CHAPspa"
26177 .scindex IIDspaauth1 "&(spa)& authenticator"
26178 .scindex IIDspaauth2 "authenticators" "&(spa)&"
26179 .cindex "authentication" "Microsoft Secure Password"
26180 .cindex "authentication" "NTLM"
26181 .cindex "Microsoft Secure Password Authentication"
26182 .cindex "NTLM authentication"
26183 The &(spa)& authenticator provides client support for Microsoft's &'Secure
26184 Password Authentication'& mechanism,
26185 which is also sometimes known as NTLM (NT LanMan). The code for client side of
26186 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
26187 taken from the Samba project (&url(http://www.samba.org)). The code for the
26188 server side was subsequently contributed by Tom Kistner. The mechanism works as
26192 After the AUTH command has been accepted, the client sends an SPA
26193 authentication request based on the user name and optional domain.
26195 The server sends back a challenge.
26197 The client builds a challenge response which makes use of the user's password
26198 and sends it to the server, which then accepts or rejects it.
26201 Encryption is used to protect the password in transit.
26205 .section "Using spa as a server" "SECID179"
26206 .cindex "options" "&(spa)& authenticator (server)"
26207 The &(spa)& authenticator has just one server option:
26209 .option server_password spa string&!! unset
26210 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
26211 This option is expanded, and the result must be the cleartext password for the
26212 authenticating user, whose name is at this point in &$auth1$&. For
26213 compatibility with previous releases of Exim, the user name is also placed in
26214 &$1$&. However, the use of this variable for this purpose is now deprecated, as
26215 it can lead to confusion in string expansions that also use numeric variables
26216 for other things. For example:
26221 server_password = \
26222 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
26224 If the expansion is forced to fail, authentication fails. Any other expansion
26225 failure causes a temporary error code to be returned.
26231 .section "Using spa as a client" "SECID180"
26232 .cindex "options" "&(spa)& authenticator (client)"
26233 The &(spa)& authenticator has the following client options:
26237 .option client_domain spa string&!! unset
26238 This option specifies an optional domain for the authentication.
26241 .option client_password spa string&!! unset
26242 This option specifies the user's password, and must be set.
26245 .option client_username spa string&!! unset
26246 This option specifies the user name, and must be set. Here is an example of a
26247 configuration of this authenticator for use with the mail servers at
26253 client_username = msn/msn_username
26254 client_password = msn_plaintext_password
26255 client_domain = DOMAIN_OR_UNSET
26257 .ecindex IIDspaauth1
26258 .ecindex IIDspaauth2
26264 . ////////////////////////////////////////////////////////////////////////////
26265 . ////////////////////////////////////////////////////////////////////////////
26267 .chapter "The tls authenticator" "CHAPtlsauth"
26268 .scindex IIDtlsauth1 "&(tls)& authenticator"
26269 .scindex IIDtlsauth2 "authenticators" "&(tls)&"
26270 .cindex "authentication" "Client Certificate"
26271 .cindex "authentication" "X509"
26272 .cindex "Certificate-based authentication"
26273 The &(tls)& authenticator provides server support for
26274 authentication based on client certificates.
26276 It is not an SMTP authentication mechanism and is not
26277 advertised by the server as part of the SMTP EHLO response.
26278 It is an Exim authenticator in the sense that it affects
26279 the protocol element of the log line, can be tested for
26280 by the &%authenticated%& ACL condition, and can set
26281 the &$authenticated_id$& variable.
26283 The client must present a verifiable certificate,
26284 for which it must have been requested via the
26285 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
26286 (see &<<CHAPTLS>>&).
26288 If an authenticator of this type is configured it is
26289 run before any SMTP-level communication is done,
26290 and can authenticate the connection.
26291 If it does, SMTP authentication is not offered.
26293 A maximum of one authenticator of this type may be present.
26296 .cindex "options" "&(tls)& authenticator (server)"
26297 The &(tls)& authenticator has three server options:
26299 .option server_param1 tls string&!! unset
26300 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
26301 This option is expanded after the TLS negotiation and
26302 the result is placed in &$auth1$&.
26303 If the expansion is forced to fail, authentication fails. Any other expansion
26304 failure causes a temporary error code to be returned.
26306 .option server_param2 tls string&!! unset
26307 .option server_param3 tls string&!! unset
26308 As above, for &$auth2$& and &$auth3$&.
26310 &%server_param1%& may also be spelled &%server_param%&.
26317 server_param1 = ${certextract {subj_altname,mail,>:} \
26318 {$tls_in_peercert}}
26319 server_condition = ${if forany {$auth1} \
26321 {${lookup ldap{ldap:///\
26322 mailname=${quote_ldap_dn:${lc:$item}},\
26323 ou=users,LDAP_DC?mailid} {$value}{0} \
26325 server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
26327 .ecindex IIDtlsauth1
26328 .ecindex IIDtlsauth2
26331 Note that because authentication is traditionally an SMTP operation,
26332 the &%authenticated%& ACL condition cannot be used in
26333 a connect- or helo-ACL.
26337 . ////////////////////////////////////////////////////////////////////////////
26338 . ////////////////////////////////////////////////////////////////////////////
26340 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
26341 "Encrypted SMTP connections"
26342 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
26343 .scindex IIDencsmtp2 "SMTP" "encryption"
26344 .cindex "TLS" "on SMTP connection"
26347 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
26348 Sockets Layer), is implemented by making use of the OpenSSL library or the
26349 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
26350 cryptographic code in the Exim distribution itself for implementing TLS. In
26351 order to use this feature you must install OpenSSL or GnuTLS, and then build a
26352 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
26353 You also need to understand the basic concepts of encryption at a managerial
26354 level, and in particular, the way that public keys, private keys, and
26355 certificates are used.
26357 RFC 3207 defines how SMTP connections can make use of encryption. Once a
26358 connection is established, the client issues a STARTTLS command. If the
26359 server accepts this, the client and the server negotiate an encryption
26360 mechanism. If the negotiation succeeds, the data that subsequently passes
26361 between them is encrypted.
26363 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
26364 and if so, what cipher suite is in use, whether the client supplied a
26365 certificate, and whether or not that certificate was verified. This makes it
26366 possible for an Exim server to deny or accept certain commands based on the
26369 &*Warning*&: Certain types of firewall and certain anti-virus products can
26370 disrupt TLS connections. You need to turn off SMTP scanning for these products
26371 in order to get TLS to work.
26375 .section "Support for the legacy &""ssmtp""& (aka &""smtps""&) protocol" &&&
26377 .cindex "ssmtp protocol"
26378 .cindex "smtps protocol"
26379 .cindex "SMTP" "ssmtp protocol"
26380 .cindex "SMTP" "smtps protocol"
26381 Early implementations of encrypted SMTP used a different TCP port from normal
26382 SMTP, and expected an encryption negotiation to start immediately, instead of
26383 waiting for a STARTTLS command from the client using the standard SMTP
26384 port. The protocol was called &"ssmtp"& or &"smtps"&, and port 465 was
26385 allocated for this purpose.
26387 This approach was abandoned when encrypted SMTP was standardized, but there are
26388 still some legacy clients that use it. Exim supports these clients by means of
26389 the &%tls_on_connect_ports%& global option. Its value must be a list of port
26390 numbers; the most common use is expected to be:
26392 tls_on_connect_ports = 465
26394 The port numbers specified by this option apply to all SMTP connections, both
26395 via the daemon and via &'inetd'&. You still need to specify all the ports that
26396 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
26397 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
26398 an extra port &-- rather, it specifies different behaviour on a port that is
26401 There is also a &%-tls-on-connect%& command line option. This overrides
26402 &%tls_on_connect_ports%&; it forces the legacy behaviour for all ports.
26409 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
26410 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
26411 The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
26412 followed later, when the first versions of GnuTLS were released. To build Exim
26413 to use GnuTLS, you need to set
26417 in Local/Makefile, in addition to
26421 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
26422 include files and libraries for GnuTLS can be found.
26424 There are some differences in usage when using GnuTLS instead of OpenSSL:
26427 The &%tls_verify_certificates%& option
26428 cannot be the path of a directory
26429 for GnuTLS versions before 3.3.6
26430 (for later versions, or OpenSSL, it can be either).
26432 The default value for &%tls_dhparam%& differs for historical reasons.
26434 .vindex "&$tls_in_peerdn$&"
26435 .vindex "&$tls_out_peerdn$&"
26436 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
26437 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
26438 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
26440 OpenSSL identifies cipher suites using hyphens as separators, for example:
26441 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
26442 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
26443 in a cipher list. To make life simpler, Exim changes underscores to hyphens
26444 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
26445 to handle its own older variants) when processing lists of cipher suites in the
26446 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
26449 The &%tls_require_ciphers%& options operate differently, as described in the
26450 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
26452 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
26453 When using OpenSSL, this option is ignored.
26454 (If an API is found to let OpenSSL be configured in this way,
26455 let the Exim Maintainers know and we'll likely use it).
26457 Some other recently added features may only be available in one or the other.
26458 This should be documented with the feature. If the documentation does not
26459 explicitly state that the feature is infeasible in the other TLS
26460 implementation, then patches are welcome.
26464 .section "GnuTLS parameter computation" "SECTgnutlsparam"
26465 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
26466 an explicit path; if the latter, then the text about generation still applies,
26467 but not the chosen filename.
26468 By default, as of Exim 4.80 a hard-coded D-H prime is used.
26469 See the documentation of &%tls_dhparam%& for more information.
26471 GnuTLS uses D-H parameters that may take a substantial amount of time
26472 to compute. It is unreasonable to re-compute them for every TLS session.
26473 Therefore, Exim keeps this data in a file in its spool directory, called
26474 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
26476 The file is owned by the Exim user and is readable only by
26477 its owner. Every Exim process that start up GnuTLS reads the D-H
26478 parameters from this file. If the file does not exist, the first Exim process
26479 that needs it computes the data and writes it to a temporary file which is
26480 renamed once it is complete. It does not matter if several Exim processes do
26481 this simultaneously (apart from wasting a few resources). Once a file is in
26482 place, new Exim processes immediately start using it.
26484 For maximum security, the parameters that are stored in this file should be
26485 recalculated periodically, the frequency depending on your paranoia level.
26486 If you are avoiding using the fixed D-H primes published in RFCs, then you
26487 are concerned about some advanced attacks and will wish to do this; if you do
26488 not regenerate then you might as well stick to the standard primes.
26490 Arranging this is easy in principle; just delete the file when you want new
26491 values to be computed. However, there may be a problem. The calculation of new
26492 parameters needs random numbers, and these are obtained from &_/dev/random_&.
26493 If the system is not very active, &_/dev/random_& may delay returning data
26494 until enough randomness (entropy) is available. This may cause Exim to hang for
26495 a substantial amount of time, causing timeouts on incoming connections.
26497 The solution is to generate the parameters externally to Exim. They are stored
26498 in &_gnutls-params-N_& in PEM format, which means that they can be
26499 generated externally using the &(certtool)& command that is part of GnuTLS.
26501 To replace the parameters with new ones, instead of deleting the file
26502 and letting Exim re-create it, you can generate new parameters using
26503 &(certtool)& and, when this has been done, replace Exim's cache file by
26504 renaming. The relevant commands are something like this:
26507 [ look for file; assume gnutls-params-2236 is the most recent ]
26510 # chown exim:exim new-params
26511 # chmod 0600 new-params
26512 # certtool --generate-dh-params --bits 2236 >>new-params
26513 # openssl dhparam -noout -text -in new-params | head
26514 [ check the first line, make sure it's not more than 2236;
26515 if it is, then go back to the start ("rm") and repeat
26516 until the size generated is at most the size requested ]
26517 # chmod 0400 new-params
26518 # mv new-params gnutls-params-2236
26520 If Exim never has to generate the parameters itself, the possibility of
26521 stalling is removed.
26523 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
26524 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
26525 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
26526 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
26527 and Exim does so. This attempt to remove Exim from TLS policy decisions
26528 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
26529 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
26530 which applies to all D-H usage, client or server. If the value returned by
26531 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
26532 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
26533 limit, which is still much higher than Exim historically used.
26535 The filename and bits used will change as the GnuTLS maintainers change the
26536 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
26537 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
26538 2432 bits, while NSS is limited to 2236 bits.
26540 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
26541 increase the chance of the generated prime actually being within acceptable
26542 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
26543 procedure above. There is no sane procedure available to Exim to double-check
26544 the size of the generated prime, so it might still be too large.
26547 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
26548 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
26549 .oindex "&%tls_require_ciphers%&" "OpenSSL"
26550 There is a function in the OpenSSL library that can be passed a list of cipher
26551 suites before the cipher negotiation takes place. This specifies which ciphers
26552 are acceptable. The list is colon separated and may contain names like
26553 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
26554 directly to this function call.
26555 Many systems will install the OpenSSL manual-pages, so you may have
26556 &'ciphers(1)'& available to you.
26557 The following quotation from the OpenSSL
26558 documentation specifies what forms of item are allowed in the cipher string:
26561 It can consist of a single cipher suite such as RC4-SHA.
26563 It can represent a list of cipher suites containing a certain algorithm,
26564 or cipher suites of a certain type. For example SHA1 represents all
26565 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
26568 Lists of cipher suites can be combined in a single cipher string using
26569 the + character. This is used as a logical and operation. For example
26570 SHA1+DES represents all cipher suites containing the SHA1 and the DES
26574 Each cipher string can be optionally preceded by one of the characters &`!`&,
26577 If &`!`& is used, the ciphers are permanently deleted from the list. The
26578 ciphers deleted can never reappear in the list even if they are explicitly
26581 If &`-`& is used, the ciphers are deleted from the list, but some or all
26582 of the ciphers can be added again by later options.
26584 If &`+`& is used, the ciphers are moved to the end of the list. This
26585 option does not add any new ciphers; it just moves matching existing ones.
26588 If none of these characters is present, the string is interpreted as
26589 a list of ciphers to be appended to the current preference list. If the list
26590 includes any ciphers already present they will be ignored: that is, they will
26591 not be moved to the end of the list.
26594 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
26597 # note single-quotes to get ! past any shell history expansion
26598 $ openssl ciphers 'HIGH:!MD5:!SHA1'
26601 This example will let the library defaults be permitted on the MX port, where
26602 there's probably no identity verification anyway, but ups the ante on the
26603 submission ports where the administrator might have some influence on the
26604 choice of clients used:
26606 # OpenSSL variant; see man ciphers(1)
26607 tls_require_ciphers = ${if =={$received_port}{25}\
26614 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
26616 .cindex "GnuTLS" "specifying parameters for"
26617 .cindex "TLS" "specifying ciphers (GnuTLS)"
26618 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
26619 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
26620 .cindex "TLS" "specifying protocols (GnuTLS)"
26621 .cindex "TLS" "specifying priority string (GnuTLS)"
26622 .oindex "&%tls_require_ciphers%&" "GnuTLS"
26623 The GnuTLS library allows the caller to provide a "priority string", documented
26624 as part of the &[gnutls_priority_init]& function. This is very similar to the
26625 ciphersuite specification in OpenSSL.
26627 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
26628 and controls both protocols and ciphers.
26630 The &%tls_require_ciphers%& option is available both as an global option,
26631 controlling how Exim behaves as a server, and also as an option of the
26632 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
26633 the value is string expanded. The resulting string is not an Exim list and
26634 the string is given to the GnuTLS library, so that Exim does not need to be
26635 aware of future feature enhancements of GnuTLS.
26637 Documentation of the strings accepted may be found in the GnuTLS manual, under
26638 "Priority strings". This is online as
26639 &url(http://www.gnutls.org/manual/html_node/Priority-Strings.html),
26640 but beware that this relates to GnuTLS 3, which may be newer than the version
26641 installed on your system. If you are using GnuTLS 3,
26642 &url(http://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string, then the example code)
26643 on that site can be used to test a given string.
26647 # Disable older versions of protocols
26648 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
26651 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
26652 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
26653 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
26655 This example will let the library defaults be permitted on the MX port, where
26656 there's probably no identity verification anyway, and lowers security further
26657 by increasing compatibility; but this ups the ante on the submission ports
26658 where the administrator might have some influence on the choice of clients
26662 tls_require_ciphers = ${if =={$received_port}{25}\
26668 .section "Configuring an Exim server to use TLS" "SECID182"
26669 .cindex "TLS" "configuring an Exim server"
26670 When Exim has been built with TLS support, it advertises the availability of
26671 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
26672 but not to any others. The default value of this option is unset, which means
26673 that STARTTLS is not advertised at all. This default is chosen because you
26674 need to set some other options in order to make TLS available, and also it is
26675 sensible for systems that want to use TLS only as a client.
26677 If a client issues a STARTTLS command and there is some configuration
26678 problem in the server, the command is rejected with a 454 error. If the client
26679 persists in trying to issue SMTP commands, all except QUIT are rejected
26682 554 Security failure
26684 If a STARTTLS command is issued within an existing TLS session, it is
26685 rejected with a 554 error code.
26687 To enable TLS operations on a server, you must set &%tls_advertise_hosts%& to
26688 match some hosts. You can, of course, set it to * to match all hosts.
26689 However, this is not all you need to do. TLS sessions to a server won't work
26690 without some further configuration at the server end.
26692 It is rumoured that all existing clients that support TLS/SSL use RSA
26693 encryption. To make this work you need to set, in the server,
26695 tls_certificate = /some/file/name
26696 tls_privatekey = /some/file/name
26698 These options are, in fact, expanded strings, so you can make them depend on
26699 the identity of the client that is connected if you wish. The first file
26700 contains the server's X509 certificate, and the second contains the private key
26701 that goes with it. These files need to be
26702 PEM format and readable by the Exim user, and must
26703 always be given as full path names.
26704 The key must not be password-protected.
26705 They can be the same file if both the
26706 certificate and the key are contained within it. If &%tls_privatekey%& is not
26707 set, or if its expansion is forced to fail or results in an empty string, this
26708 is assumed to be the case. The certificate file may also contain intermediate
26709 certificates that need to be sent to the client to enable it to authenticate
26710 the server's certificate.
26712 If you do not understand about certificates and keys, please try to find a
26713 source of this background information, which is not Exim-specific. (There are a
26714 few comments below in section &<<SECTcerandall>>&.)
26716 &*Note*&: These options do not apply when Exim is operating as a client &--
26717 they apply only in the case of a server. If you need to use a certificate in an
26718 Exim client, you must set the options of the same names in an &(smtp)&
26721 With just these options, an Exim server will be able to use TLS. It does not
26722 require the client to have a certificate (but see below for how to insist on
26723 this). There is one other option that may be needed in other situations. If
26725 tls_dhparam = /some/file/name
26727 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
26728 with the parameters contained in the file.
26729 Set this to &`none`& to disable use of DH entirely, by making no prime
26734 This may also be set to a string identifying a standard prime to be used for
26735 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
26736 used is &`ike23`&. There are a few standard primes available, see the
26737 documentation for &%tls_dhparam%& for the complete list.
26743 for a way of generating file data.
26745 The strings supplied for these three options are expanded every time a client
26746 host connects. It is therefore possible to use different certificates and keys
26747 for different hosts, if you so wish, by making use of the client's IP address
26748 in &$sender_host_address$& to control the expansion. If a string expansion is
26749 forced to fail, Exim behaves as if the option is not set.
26751 .cindex "cipher" "logging"
26752 .cindex "log" "TLS cipher"
26753 .vindex "&$tls_in_cipher$&"
26754 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
26755 an incoming TLS connection. It is included in the &'Received:'& header of an
26756 incoming message (by default &-- you can, of course, change this), and it is
26757 also included in the log line that records a message's arrival, keyed by
26758 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
26759 condition can be used to test for specific cipher suites in ACLs.
26761 Once TLS has been established, the ACLs that run for subsequent SMTP commands
26762 can check the name of the cipher suite and vary their actions accordingly. The
26763 cipher suite names vary, depending on which TLS library is being used. For
26764 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
26765 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
26766 documentation for more details.
26768 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
26769 (again depending on the &%tls_cipher%& log selector).
26772 .section "Requesting and verifying client certificates" "SECID183"
26773 .cindex "certificate" "verification of client"
26774 .cindex "TLS" "client certificate verification"
26775 If you want an Exim server to request a certificate when negotiating a TLS
26776 session with a client, you must set either &%tls_verify_hosts%& or
26777 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
26778 apply to all TLS connections. For any host that matches one of these options,
26779 Exim requests a certificate as part of the setup of the TLS session. The
26780 contents of the certificate are verified by comparing it with a list of
26781 expected certificates.
26782 These may be the system default set (depending on library version),
26783 an explicit file or,
26784 depending on library version, a directory, identified by
26785 &%tls_verify_certificates%&.
26787 A file can contain multiple certificates, concatenated end to end. If a
26790 each certificate must be in a separate file, with a name (or a symbolic link)
26791 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
26792 certificate. You can compute the relevant hash by running the command
26794 openssl x509 -hash -noout -in /cert/file
26796 where &_/cert/file_& contains a single certificate.
26798 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
26799 what happens if the client does not supply a certificate, or if the certificate
26800 does not match any of the certificates in the collection named by
26801 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
26802 attempt to set up a TLS session is aborted, and the incoming connection is
26803 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
26804 session continues. ACLs that run for subsequent SMTP commands can detect the
26805 fact that no certificate was verified, and vary their actions accordingly. For
26806 example, you can insist on a certificate before accepting a message for
26807 relaying, but not when the message is destined for local delivery.
26809 .vindex "&$tls_in_peerdn$&"
26810 When a client supplies a certificate (whether it verifies or not), the value of
26811 the Distinguished Name of the certificate is made available in the variable
26812 &$tls_in_peerdn$& during subsequent processing of the message.
26814 .cindex "log" "distinguished name"
26815 Because it is often a long text string, it is not included in the log line or
26816 &'Received:'& header by default. You can arrange for it to be logged, keyed by
26817 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
26818 &%received_header_text%& to change the &'Received:'& header. When no
26819 certificate is supplied, &$tls_in_peerdn$& is empty.
26822 .section "Revoked certificates" "SECID184"
26823 .cindex "TLS" "revoked certificates"
26824 .cindex "revocation list"
26825 .cindex "certificate" "revocation list"
26826 .cindex "OCSP" "stapling"
26827 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
26828 certificates are revoked. If you have such a list, you can pass it to an Exim
26829 server using the global option called &%tls_crl%& and to an Exim client using
26830 an identically named option for the &(smtp)& transport. In each case, the value
26831 of the option is expanded and must then be the name of a file that contains a
26833 The downside is that clients have to periodically re-download a potentially huge
26834 file from every certificate authority they know of.
26836 The way with most moving parts at query time is Online Certificate
26837 Status Protocol (OCSP), where the client verifies the certificate
26838 against an OCSP server run by the CA. This lets the CA track all
26839 usage of the certs. It requires running software with access to the
26840 private key of the CA, to sign the responses to the OCSP queries. OCSP
26841 is based on HTTP and can be proxied accordingly.
26843 The only widespread OCSP server implementation (known to this writer)
26844 comes as part of OpenSSL and aborts on an invalid request, such as
26845 connecting to the port and then disconnecting. This requires
26846 re-entering the passphrase each time some random client does this.
26848 The third way is OCSP Stapling; in this, the server using a certificate
26849 issued by the CA periodically requests an OCSP proof of validity from
26850 the OCSP server, then serves it up inline as part of the TLS
26851 negotiation. This approach adds no extra round trips, does not let the
26852 CA track users, scales well with number of certs issued by the CA and is
26853 resilient to temporary OCSP server failures, as long as the server
26854 starts retrying to fetch an OCSP proof some time before its current
26855 proof expires. The downside is that it requires server support.
26857 Unless Exim is built with the support disabled,
26859 or with GnuTLS earlier than version 3.3.16 / 3.4.8
26861 support for OCSP stapling is included.
26863 There is a global option called &%tls_ocsp_file%&.
26864 The file specified therein is expected to be in DER format, and contain
26865 an OCSP proof. Exim will serve it as part of the TLS handshake. This
26866 option will be re-expanded for SNI, if the &%tls_certificate%& option
26867 contains &`tls_in_sni`&, as per other TLS options.
26869 Exim does not at this time implement any support for fetching a new OCSP
26870 proof. The burden is on the administrator to handle this, outside of
26871 Exim. The file specified should be replaced atomically, so that the
26872 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
26873 on each connection, so a new file will be handled transparently on the
26876 When built with OpenSSL Exim will check for a valid next update timestamp
26877 in the OCSP proof; if not present, or if the proof has expired, it will be
26880 For the client to be able to verify the stapled OCSP the server must
26881 also supply, in its stapled information, any intermediate
26882 certificates for the chain leading to the OCSP proof from the signer
26883 of the server certificate. There may be zero or one such. These
26884 intermediate certificates should be added to the server OCSP stapling
26885 file named by &%tls_ocsp_file%&.
26887 Note that the proof only covers the terminal server certificate,
26888 not any of the chain from CA to it.
26890 There is no current way to staple a proof for a client certificate.
26893 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
26894 OCSP server is supplied. The server URL may be included in the
26895 server certificate, if the CA is helpful.
26897 One failure mode seen was the OCSP Signer cert expiring before the end
26898 of validity of the OCSP proof. The checking done by Exim/OpenSSL
26899 noted this as invalid overall, but the re-fetch script did not.
26905 .section "Configuring an Exim client to use TLS" "SECID185"
26906 .cindex "cipher" "logging"
26907 .cindex "log" "TLS cipher"
26908 .cindex "log" "distinguished name"
26909 .cindex "TLS" "configuring an Exim client"
26910 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
26911 deliveries as well as to incoming, the latter one causing logging of the
26912 server certificate's DN. The remaining client configuration for TLS is all
26913 within the &(smtp)& transport.
26915 It is not necessary to set any options to have TLS work in the &(smtp)&
26916 transport. If Exim is built with TLS support, and TLS is advertised by a
26917 server, the &(smtp)& transport always tries to start a TLS session. However,
26918 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
26919 transport) to a list of server hosts for which TLS should not be used.
26921 If you do not want Exim to attempt to send messages unencrypted when an attempt
26922 to set up an encrypted connection fails in any way, you can set
26923 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
26924 those hosts, delivery is always deferred if an encrypted connection cannot be
26925 set up. If there are any other hosts for the address, they are tried in the
26928 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
26929 the message unencrypted. It always does this if the response to STARTTLS is
26930 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
26931 session after a success response code, what happens is controlled by the
26932 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
26933 delivery to this host is deferred, and other hosts (if available) are tried. If
26934 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
26935 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
26936 negotiation fails, Exim closes the current connection (because it is in an
26937 unknown state), opens a new one to the same host, and then tries the delivery
26940 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
26941 transport provide the client with a certificate, which is passed to the server
26942 if it requests it. If the server is Exim, it will request a certificate only if
26943 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
26945 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
26946 specifies a collection of expected server certificates.
26947 These may be the system default set (depending on library version),
26949 depending on library version, a directory,
26950 must name a file or,
26951 for OpenSSL only (not GnuTLS), a directory.
26952 The client verifies the server's certificate
26953 against this collection, taking into account any revoked certificates that are
26954 in the list defined by &%tls_crl%&.
26955 Failure to verify fails the TLS connection unless either of the
26956 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
26958 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
26959 certificate verification to the listed servers. Verification either must
26960 or need not succeed respectively.
26962 The &(smtp)& transport has two OCSP-related options:
26963 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
26964 is requested and required for the connection to proceed. The default
26966 &%hosts_request_ocsp%&; a host-list for which (additionally)
26967 a Certificate Status is requested (but not necessarily verified). The default
26968 value is "*" meaning that requests are made unless configured
26971 The host(s) should also be in &%hosts_require_tls%&, and
26972 &%tls_verify_certificates%& configured for the transport,
26973 for OCSP to be relevant.
26976 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
26977 list of permitted cipher suites. If either of these checks fails, delivery to
26978 the current host is abandoned, and the &(smtp)& transport tries to deliver to
26979 alternative hosts, if any.
26982 These options must be set in the &(smtp)& transport for Exim to use TLS when it
26983 is operating as a client. Exim does not assume that a server certificate (set
26984 by the global options of the same name) should also be used when operating as a
26988 .vindex "&$host_address$&"
26989 All the TLS options in the &(smtp)& transport are expanded before use, with
26990 &$host$& and &$host_address$& containing the name and address of the server to
26991 which the client is connected. Forced failure of an expansion causes Exim to
26992 behave as if the relevant option were unset.
26994 .vindex &$tls_out_bits$&
26995 .vindex &$tls_out_cipher$&
26996 .vindex &$tls_out_peerdn$&
26997 .vindex &$tls_out_sni$&
26998 Before an SMTP connection is established, the
26999 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
27000 variables are emptied. (Until the first connection, they contain the values
27001 that were set when the message was received.) If STARTTLS is subsequently
27002 successfully obeyed, these variables are set to the relevant values for the
27003 outgoing connection.
27007 .section "Use of TLS Server Name Indication" "SECTtlssni"
27008 .cindex "TLS" "Server Name Indication"
27009 .vindex "&$tls_in_sni$&"
27010 .oindex "&%tls_in_sni%&"
27011 With TLS1.0 or above, there is an extension mechanism by which extra
27012 information can be included at various points in the protocol. One of these
27013 extensions, documented in RFC 6066 (and before that RFC 4366) is
27014 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
27015 client in the initial handshake, so that the server can examine the servername
27016 within and possibly choose to use different certificates and keys (and more)
27019 This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
27020 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
27023 With SMTP to MX, there are the same problems here as in choosing the identity
27024 against which to validate a certificate: you can't rely on insecure DNS to
27025 provide the identity which you then cryptographically verify. So this will
27026 be of limited use in that environment.
27028 With SMTP to Submission, there is a well-defined hostname which clients are
27029 connecting to and can validate certificates against. Thus clients &*can*&
27030 choose to include this information in the TLS negotiation. If this becomes
27031 wide-spread, then hosters can choose to present different certificates to
27032 different clients. Or even negotiate different cipher suites.
27034 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
27035 if not empty, will be sent on a TLS session as part of the handshake. There's
27036 nothing more to it. Choosing a sensible value not derived insecurely is the
27037 only point of caution. The &$tls_out_sni$& variable will be set to this string
27038 for the lifetime of the client connection (including during authentication).
27040 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
27041 received from a client.
27042 It can be logged with the &%log_selector%& item &`+tls_sni`&.
27044 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
27045 option (prior to expansion) then the following options will be re-expanded
27046 during TLS session handshake, to permit alternative values to be chosen:
27049 .vindex "&%tls_certificate%&"
27050 &%tls_certificate%&
27052 .vindex "&%tls_crl%&"
27055 .vindex "&%tls_privatekey%&"
27058 .vindex "&%tls_verify_certificates%&"
27059 &%tls_verify_certificates%&
27061 .vindex "&%tls_ocsp_file%&"
27065 Great care should be taken to deal with matters of case, various injection
27066 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
27067 can always be referenced; it is important to remember that &$tls_sni$& is
27068 arbitrary unverified data provided prior to authentication.
27070 The Exim developers are proceeding cautiously and so far no other TLS options
27073 When Exim is built against OpenSSL, OpenSSL must have been built with support
27074 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
27075 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
27076 see &`-servername`& in the output, then OpenSSL has support.
27078 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
27079 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
27080 built, then you have SNI support).
27084 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
27086 .cindex "multiple SMTP deliveries with TLS"
27087 .cindex "TLS" "multiple message deliveries"
27088 Exim sends multiple messages down the same TCP/IP connection by starting up
27089 an entirely new delivery process for each message, passing the socket from
27090 one process to the next. This implementation does not fit well with the use
27091 of TLS, because there is quite a lot of state information associated with a TLS
27092 connection, not just a socket identification. Passing all the state information
27093 to a new process is not feasible. Consequently, Exim shuts down an existing TLS
27094 session before passing the socket to a new process. The new process may then
27095 try to start a new TLS session, and if successful, may try to re-authenticate
27096 if AUTH is in use, before sending the next message.
27098 The RFC is not clear as to whether or not an SMTP session continues in clear
27099 after TLS has been shut down, or whether TLS may be restarted again later, as
27100 just described. However, if the server is Exim, this shutdown and
27101 reinitialization works. It is not known which (if any) other servers operate
27102 successfully if the client closes a TLS session and continues with unencrypted
27103 SMTP, but there are certainly some that do not work. For such servers, Exim
27104 should not pass the socket to another process, because the failure of the
27105 subsequent attempt to use it would cause Exim to record a temporary host error,
27106 and delay other deliveries to that host.
27108 To test for this case, Exim sends an EHLO command to the server after
27109 closing down the TLS session. If this fails in any way, the connection is
27110 closed instead of being passed to a new delivery process, but no retry
27111 information is recorded.
27113 There is also a manual override; you can set &%hosts_nopass_tls%& on the
27114 &(smtp)& transport to match those hosts for which Exim should not pass
27115 connections to new processes if TLS has been used.
27120 .section "Certificates and all that" "SECTcerandall"
27121 .cindex "certificate" "references to discussion"
27122 In order to understand fully how TLS works, you need to know about
27123 certificates, certificate signing, and certificate authorities. This is not the
27124 place to give a tutorial, especially as I do not know very much about it
27125 myself. Some helpful introduction can be found in the FAQ for the SSL addition
27126 to Apache, currently at
27128 &url(http://www.modssl.org/docs/2.7/ssl_faq.html#ToC24)
27130 Other parts of the &'modssl'& documentation are also helpful, and have
27131 links to further files.
27132 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
27133 0-201-61598-3), contains both introductory and more in-depth descriptions.
27134 Some sample programs taken from the book are available from
27136 &url(http://www.rtfm.com/openssl-examples/)
27140 .section "Certificate chains" "SECID186"
27141 The file named by &%tls_certificate%& may contain more than one
27142 certificate. This is useful in the case where the certificate that is being
27143 sent is validated by an intermediate certificate which the other end does
27144 not have. Multiple certificates must be in the correct order in the file.
27145 First the host's certificate itself, then the first intermediate
27146 certificate to validate the issuer of the host certificate, then the next
27147 intermediate certificate to validate the issuer of the first intermediate
27148 certificate, and so on, until finally (optionally) the root certificate.
27149 The root certificate must already be trusted by the recipient for
27150 validation to succeed, of course, but if it's not preinstalled, sending the
27151 root certificate along with the rest makes it available for the user to
27152 install if the receiving end is a client MUA that can interact with a user.
27154 Note that certificates using MD5 are unlikely to work on today's Internet;
27155 even if your libraries allow loading them for use in Exim when acting as a
27156 server, increasingly clients will not accept such certificates. The error
27157 diagnostics in such a case can be frustratingly vague.
27161 .section "Self-signed certificates" "SECID187"
27162 .cindex "certificate" "self-signed"
27163 You can create a self-signed certificate using the &'req'& command provided
27164 with OpenSSL, like this:
27165 . ==== Do not shorten the duration here without reading and considering
27166 . ==== the text below. Please leave it at 9999 days.
27168 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
27171 &_file1_& and &_file2_& can be the same file; the key and the certificate are
27172 delimited and so can be identified independently. The &%-days%& option
27173 specifies a period for which the certificate is valid. The &%-nodes%& option is
27174 important: if you do not set it, the key is encrypted with a passphrase
27175 that you are prompted for, and any use that is made of the key causes more
27176 prompting for the passphrase. This is not helpful if you are going to use
27177 this certificate and key in an MTA, where prompting is not possible.
27179 . ==== I expect to still be working 26 years from now. The less technical
27180 . ==== debt I create, in terms of storing up trouble for my later years, the
27181 . ==== happier I will be then. We really have reached the point where we
27182 . ==== should start, at the very least, provoking thought and making folks
27183 . ==== pause before proceeding, instead of leaving all the fixes until two
27184 . ==== years before 2^31 seconds after the 1970 Unix epoch.
27186 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
27187 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
27188 the above command might produce a date in the past. Think carefully about
27189 the lifetime of the systems you're deploying, and either reduce the duration
27190 of the certificate or reconsider your platform deployment. (At time of
27191 writing, reducing the duration is the most likely choice, but the inexorable
27192 progression of time takes us steadily towards an era where this will not
27193 be a sensible resolution).
27195 A self-signed certificate made in this way is sufficient for testing, and
27196 may be adequate for all your requirements if you are mainly interested in
27197 encrypting transfers, and not in secure identification.
27199 However, many clients require that the certificate presented by the server be a
27200 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
27201 certificate. In this situation, the self-signed certificate described above
27202 must be installed on the client host as a trusted root &'certification
27203 authority'& (CA), and the certificate used by Exim must be a user certificate
27204 signed with that self-signed certificate.
27206 For information on creating self-signed CA certificates and using them to sign
27207 user certificates, see the &'General implementation overview'& chapter of the
27208 Open-source PKI book, available online at
27209 &url(http://ospkibook.sourceforge.net/).
27210 .ecindex IIDencsmtp1
27211 .ecindex IIDencsmtp2
27215 . ////////////////////////////////////////////////////////////////////////////
27216 . ////////////////////////////////////////////////////////////////////////////
27218 .chapter "Access control lists" "CHAPACL"
27219 .scindex IIDacl "&ACL;" "description"
27220 .cindex "control of incoming mail"
27221 .cindex "message" "controlling incoming"
27222 .cindex "policy control" "access control lists"
27223 Access Control Lists (ACLs) are defined in a separate section of the run time
27224 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
27225 name, terminated by a colon. Here is a complete ACL section that contains just
27226 one very small ACL:
27230 accept hosts = one.host.only
27232 You can have as many lists as you like in the ACL section, and the order in
27233 which they appear does not matter. The lists are self-terminating.
27235 The majority of ACLs are used to control Exim's behaviour when it receives
27236 certain SMTP commands. This applies both to incoming TCP/IP connections, and
27237 when a local process submits a message using SMTP by specifying the &%-bs%&
27238 option. The most common use is for controlling which recipients are accepted
27239 in incoming messages. In addition, you can define an ACL that is used to check
27240 local non-SMTP messages. The default configuration file contains an example of
27241 a realistic ACL for checking RCPT commands. This is discussed in chapter
27242 &<<CHAPdefconfil>>&.
27245 .section "Testing ACLs" "SECID188"
27246 The &%-bh%& command line option provides a way of testing your ACL
27247 configuration locally by running a fake SMTP session with which you interact.
27248 The host &'relay-test.mail-abuse.org'& provides a service for checking your
27249 relaying configuration (see section &<<SECTcheralcon>>& for more details).
27253 .section "Specifying when ACLs are used" "SECID189"
27254 .cindex "&ACL;" "options for specifying"
27255 In order to cause an ACL to be used, you have to name it in one of the relevant
27256 options in the main part of the configuration. These options are:
27257 .cindex "AUTH" "ACL for"
27258 .cindex "DATA" "ACLs for"
27259 .cindex "ETRN" "ACL for"
27260 .cindex "EXPN" "ACL for"
27261 .cindex "HELO" "ACL for"
27262 .cindex "EHLO" "ACL for"
27263 .cindex "DKIM" "ACL for"
27264 .cindex "MAIL" "ACL for"
27265 .cindex "QUIT, ACL for"
27266 .cindex "RCPT" "ACL for"
27267 .cindex "STARTTLS, ACL for"
27268 .cindex "VRFY" "ACL for"
27269 .cindex "SMTP" "connection, ACL for"
27270 .cindex "non-SMTP messages" "ACLs for"
27271 .cindex "MIME content scanning" "ACL for"
27272 .cindex "PRDR" "ACL for"
27275 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
27276 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
27277 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
27278 .irow &%acl_smtp_auth%& "ACL for AUTH"
27279 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
27280 .irow &%acl_smtp_data%& "ACL after DATA is complete"
27281 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
27282 .irow &%acl_smtp_dkim%& "ACL for each DKIM signer"
27283 .irow &%acl_smtp_etrn%& "ACL for ETRN"
27284 .irow &%acl_smtp_expn%& "ACL for EXPN"
27285 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
27286 .irow &%acl_smtp_mail%& "ACL for MAIL"
27287 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
27288 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
27289 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
27290 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
27291 .irow &%acl_smtp_quit%& "ACL for QUIT"
27292 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
27293 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
27294 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
27297 For example, if you set
27299 acl_smtp_rcpt = small_acl
27301 the little ACL defined above is used whenever Exim receives a RCPT command
27302 in an SMTP dialogue. The majority of policy tests on incoming messages can be
27303 done when RCPT commands arrive. A rejection of RCPT should cause the
27304 sending MTA to give up on the recipient address contained in the RCPT
27305 command, whereas rejection at other times may cause the client MTA to keep on
27306 trying to deliver the message. It is therefore recommended that you do as much
27307 testing as possible at RCPT time.
27310 .section "The non-SMTP ACLs" "SECID190"
27311 .cindex "non-SMTP messages" "ACLs for"
27312 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
27313 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
27314 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
27315 the state of the SMTP connection such as encryption and authentication) are not
27316 relevant and are forbidden in these ACLs. However, the sender and recipients
27317 are known, so the &%senders%& and &%sender_domains%& conditions and the
27318 &$sender_address$& and &$recipients$& variables can be used. Variables such as
27319 &$authenticated_sender$& are also available. You can specify added header lines
27320 in any of these ACLs.
27322 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
27323 non-SMTP message, before any of the message has been read. (This is the
27324 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
27325 batched SMTP input, it runs after the DATA command has been reached. The
27326 result of this ACL is ignored; it cannot be used to reject a message. If you
27327 really need to, you could set a value in an ACL variable here and reject based
27328 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
27329 controls, and in particular, it can be used to set
27331 control = suppress_local_fixups
27333 This cannot be used in the other non-SMTP ACLs because by the time they are
27334 run, it is too late.
27336 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
27337 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
27339 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
27340 kind of rejection is treated as permanent, because there is no way of sending a
27341 temporary error for these kinds of message.
27344 .section "The SMTP connect ACL" "SECID191"
27345 .cindex "SMTP" "connection, ACL for"
27346 .oindex &%smtp_banner%&
27347 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
27348 session, after the test specified by &%host_reject_connection%& (which is now
27349 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
27350 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
27351 the message override the banner message that is otherwise specified by the
27352 &%smtp_banner%& option.
27355 .section "The EHLO/HELO ACL" "SECID192"
27356 .cindex "EHLO" "ACL for"
27357 .cindex "HELO" "ACL for"
27358 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
27359 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
27360 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
27361 Note that a client may issue more than one EHLO or HELO command in an SMTP
27362 session, and indeed is required to issue a new EHLO or HELO after successfully
27363 setting up encryption following a STARTTLS command.
27365 If the command is accepted by an &%accept%& verb that has a &%message%&
27366 modifier, the message may not contain more than one line (it will be truncated
27367 at the first newline and a panic logged if it does). Such a message cannot
27368 affect the EHLO options that are listed on the second and subsequent lines of
27372 .section "The DATA ACLs" "SECID193"
27373 .cindex "DATA" "ACLs for"
27374 Two ACLs are associated with the DATA command, because it is two-stage
27375 command, with two responses being sent to the client.
27376 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
27377 is obeyed. This gives you control after all the RCPT commands, but before
27378 the message itself is received. It offers the opportunity to give a negative
27379 response to the DATA command before the data is transmitted. Header lines
27380 added by MAIL or RCPT ACLs are not visible at this time, but any that
27381 are defined here are visible when the &%acl_smtp_data%& ACL is run.
27383 You cannot test the contents of the message, for example, to verify addresses
27384 in the headers, at RCPT time or when the DATA command is received. Such
27385 tests have to appear in the ACL that is run after the message itself has been
27386 received, before the final response to the DATA command is sent. This is
27387 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
27388 associated with the DATA command.
27390 For both of these ACLs, it is not possible to reject individual recipients. An
27391 error response rejects the entire message. Unfortunately, it is known that some
27392 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
27393 before or after the data) correctly &-- they keep the message on their queues
27394 and try again later, but that is their problem, though it does waste some of
27397 The &%acl_smtp_data%& ACL is run after
27398 the &%acl_smtp_data_prdr%&,
27399 the &%acl_smtp_dkim%&
27400 and the &%acl_smtp_mime%& ACLs.
27402 .section "The SMTP DKIM ACL" "SECTDKIMACL"
27403 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
27404 enabled (which is the default).
27406 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
27407 received, and is executed for each DKIM signature found in a message. If not
27408 otherwise specified, the default action is to accept.
27410 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
27412 For details on the operation of DKIM, see chapter &<<CHAPdkim>>&.
27415 .section "The SMTP MIME ACL" "SECID194"
27416 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
27417 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
27419 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
27422 .section "The SMTP PRDR ACL" "SECTPRDRACL"
27423 .cindex "PRDR" "ACL for"
27424 .oindex "&%prdr_enable%&"
27425 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
27426 with PRDR support enabled (which is the default).
27427 It becomes active only when the PRDR feature is negotiated between
27428 client and server for a message, and more than one recipient
27431 The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
27432 has been received, and is executed once for each recipient of the message
27433 with &$local_part$& and &$domain$& valid.
27434 The test may accept, defer or deny for individual recipients.
27435 The &%acl_smtp_data%& will still be called after this ACL and
27436 can reject the message overall, even if this ACL has accepted it
27437 for some or all recipients.
27439 PRDR may be used to support per-user content filtering. Without it
27440 one must defer any recipient after the first that has a different
27441 content-filter configuration. With PRDR, the RCPT-time check
27443 .cindex "PRDR" "variable for"
27444 for this can be disabled when the variable &$prdr_requested$&
27447 Any required difference in behaviour of the main DATA-time
27448 ACL should however depend on the PRDR-time ACL having run, as Exim
27449 will avoid doing so in some situations (e.g. single-recipient mails).
27451 See also the &%prdr_enable%& global option
27452 and the &%hosts_try_prdr%& smtp transport option.
27454 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
27455 If the ACL is not defined, processing completes as if
27456 the feature was not requested by the client.
27458 .section "The QUIT ACL" "SECTQUITACL"
27459 .cindex "QUIT, ACL for"
27460 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
27461 does not affect the response code to QUIT, which is always 221. Thus, the ACL
27462 does not in fact control any access.
27463 For this reason, it may only accept
27464 or warn as its final result.
27466 This ACL can be used for tasks such as custom logging at the end of an SMTP
27467 session. For example, you can use ACL variables in other ACLs to count
27468 messages, recipients, etc., and log the totals at QUIT time using one or
27469 more &%logwrite%& modifiers on a &%warn%& verb.
27471 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
27472 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
27474 You do not need to have a final &%accept%&, but if you do, you can use a
27475 &%message%& modifier to specify custom text that is sent as part of the 221
27478 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
27479 failure (for example, failure to open a log file, or when Exim is bombing out
27480 because it has detected an unrecoverable error), all SMTP commands from the
27481 client are given temporary error responses until QUIT is received or the
27482 connection is closed. In these special cases, the QUIT ACL does not run.
27485 .section "The not-QUIT ACL" "SECTNOTQUITACL"
27486 .vindex &$acl_smtp_notquit$&
27487 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
27488 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
27489 trouble, such as being unable to write to its log files, this ACL is not run,
27490 because it might try to do things (such as write to log files) that make the
27491 situation even worse.
27493 Like the QUIT ACL, this ACL is provided to make it possible to do customized
27494 logging or to gather statistics, and its outcome is ignored. The &%delay%&
27495 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
27498 .vindex &$smtp_notquit_reason$&
27499 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
27500 to a string that indicates the reason for the termination of the SMTP
27501 connection. The possible values are:
27503 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
27504 .irow &`bad-commands`& "Too many unknown or non-mail commands"
27505 .irow &`command-timeout`& "Timeout while reading SMTP commands"
27506 .irow &`connection-lost`& "The SMTP connection has been lost"
27507 .irow &`data-timeout`& "Timeout while reading message data"
27508 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
27509 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
27510 .irow &`signal-exit`& "SIGTERM or SIGINT"
27511 .irow &`synchronization-error`& "SMTP synchronization error"
27512 .irow &`tls-failed`& "TLS failed to start"
27514 In most cases when an SMTP connection is closed without having received QUIT,
27515 Exim sends an SMTP response message before actually closing the connection.
27516 With the exception of the &`acl-drop`& case, the default message can be
27517 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
27518 &%drop%& verb in another ACL, it is the message from the other ACL that is
27522 .section "Finding an ACL to use" "SECID195"
27523 .cindex "&ACL;" "finding which to use"
27524 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
27525 you can use different ACLs in different circumstances. For example,
27527 acl_smtp_rcpt = ${if ={25}{$interface_port} \
27528 {acl_check_rcpt} {acl_check_rcpt_submit} }
27530 In the default configuration file there are some example settings for
27531 providing an RFC 4409 message submission service on port 587 and a
27532 non-standard &"smtps"& service on port 465. You can use a string
27533 expansion like this to choose an ACL for MUAs on these ports which is
27534 more appropriate for this purpose than the default ACL on port 25.
27536 The expanded string does not have to be the name of an ACL in the
27537 configuration file; there are other possibilities. Having expanded the
27538 string, Exim searches for an ACL as follows:
27541 If the string begins with a slash, Exim uses it as a file name, and reads its
27542 contents as an ACL. The lines are processed in the same way as lines in the
27543 Exim configuration file. In particular, continuation lines are supported, blank
27544 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
27545 If the file does not exist or cannot be read, an error occurs (typically
27546 causing a temporary failure of whatever caused the ACL to be run). For example:
27548 acl_smtp_data = /etc/acls/\
27549 ${lookup{$sender_host_address}lsearch\
27550 {/etc/acllist}{$value}{default}}
27552 This looks up an ACL file to use on the basis of the host's IP address, falling
27553 back to a default if the lookup fails. If an ACL is successfully read from a
27554 file, it is retained in memory for the duration of the Exim process, so that it
27555 can be re-used without having to re-read the file.
27557 If the string does not start with a slash, and does not contain any spaces,
27558 Exim searches the ACL section of the configuration for an ACL whose name
27559 matches the string.
27561 If no named ACL is found, or if the string contains spaces, Exim parses
27562 the string as an inline ACL. This can save typing in cases where you just
27563 want to have something like
27565 acl_smtp_vrfy = accept
27567 in order to allow free use of the VRFY command. Such a string may contain
27568 newlines; it is processed in the same way as an ACL that is read from a file.
27574 .section "ACL return codes" "SECID196"
27575 .cindex "&ACL;" "return codes"
27576 Except for the QUIT ACL, which does not affect the SMTP return code (see
27577 section &<<SECTQUITACL>>& above), the result of running an ACL is either
27578 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
27579 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
27580 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
27581 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
27582 This also causes a 4&'xx'& return code.
27584 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
27585 &"deny"&, because there is no mechanism for passing temporary errors to the
27586 submitters of non-SMTP messages.
27589 ACLs that are relevant to message reception may also return &"discard"&. This
27590 has the effect of &"accept"&, but causes either the entire message or an
27591 individual recipient address to be discarded. In other words, it is a
27592 blackholing facility. Use it with care.
27594 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
27595 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
27596 RCPT ACL is to discard just the one recipient address. If there are no
27597 recipients left when the message's data is received, the DATA ACL is not
27598 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
27599 remaining recipients. The &"discard"& return is not permitted for the
27600 &%acl_smtp_predata%& ACL.
27603 .cindex "&[local_scan()]& function" "when all recipients discarded"
27604 The &[local_scan()]& function is always run, even if there are no remaining
27605 recipients; it may create new recipients.
27609 .section "Unset ACL options" "SECID197"
27610 .cindex "&ACL;" "unset options"
27611 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
27612 all the same. &*Note*&: These defaults apply only when the relevant ACL is
27613 not defined at all. For any defined ACL, the default action when control
27614 reaches the end of the ACL statements is &"deny"&.
27616 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
27617 these two are ACLs that are used only for their side effects. They cannot be
27618 used to accept or reject anything.
27620 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
27621 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
27622 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
27623 when the ACL is not defined is &"accept"&.
27625 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
27626 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
27627 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
27628 messages over an SMTP connection. For an example, see the ACL in the default
27629 configuration file.
27634 .section "Data for message ACLs" "SECID198"
27635 .cindex "&ACL;" "data for message ACL"
27637 .vindex &$local_part$&
27638 .vindex &$sender_address$&
27639 .vindex &$sender_host_address$&
27640 .vindex &$smtp_command$&
27641 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
27642 that contain information about the host and the message's sender (for example,
27643 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
27644 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
27645 &$local_part$& are set from the argument address. The entire SMTP command
27646 is available in &$smtp_command$&.
27648 When an ACL for the AUTH parameter of MAIL is running, the variables that
27649 contain information about the host are set, but &$sender_address$& is not yet
27650 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
27653 .vindex "&$message_size$&"
27654 The &$message_size$& variable is set to the value of the SIZE parameter on
27655 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
27656 that parameter is not given. The value is updated to the true message size by
27657 the time the final DATA ACL is run (after the message data has been
27660 .vindex "&$rcpt_count$&"
27661 .vindex "&$recipients_count$&"
27662 The &$rcpt_count$& variable increases by one for each RCPT command received.
27663 The &$recipients_count$& variable increases by one each time a RCPT command is
27664 accepted, so while an ACL for RCPT is being processed, it contains the number
27665 of previously accepted recipients. At DATA time (for both the DATA ACLs),
27666 &$rcpt_count$& contains the total number of RCPT commands, and
27667 &$recipients_count$& contains the total number of accepted recipients.
27673 .section "Data for non-message ACLs" "SECTdatfornon"
27674 .cindex "&ACL;" "data for non-message ACL"
27675 .vindex &$smtp_command_argument$&
27676 .vindex &$smtp_command$&
27677 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
27678 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
27679 and the entire SMTP command is available in &$smtp_command$&.
27680 These variables can be tested using a &%condition%& condition. For example,
27681 here is an ACL for use with AUTH, which insists that either the session is
27682 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
27683 does not permit authentication methods that use cleartext passwords on
27684 unencrypted connections.
27687 accept encrypted = *
27688 accept condition = ${if eq{${uc:$smtp_command_argument}}\
27690 deny message = TLS encryption or CRAM-MD5 required
27692 (Another way of applying this restriction is to arrange for the authenticators
27693 that use cleartext passwords not to be advertised when the connection is not
27694 encrypted. You can use the generic &%server_advertise_condition%& authenticator
27695 option to do this.)
27699 .section "Format of an ACL" "SECID199"
27700 .cindex "&ACL;" "format of"
27701 .cindex "&ACL;" "verbs, definition of"
27702 An individual ACL consists of a number of statements. Each statement starts
27703 with a verb, optionally followed by a number of conditions and &"modifiers"&.
27704 Modifiers can change the way the verb operates, define error and log messages,
27705 set variables, insert delays, and vary the processing of accepted messages.
27707 If all the conditions are met, the verb is obeyed. The same condition may be
27708 used (with different arguments) more than once in the same statement. This
27709 provides a means of specifying an &"and"& conjunction between conditions. For
27712 deny dnslists = list1.example
27713 dnslists = list2.example
27715 If there are no conditions, the verb is always obeyed. Exim stops evaluating
27716 the conditions and modifiers when it reaches a condition that fails. What
27717 happens then depends on the verb (and in one case, on a special modifier). Not
27718 all the conditions make sense at every testing point. For example, you cannot
27719 test a sender address in the ACL that is run for a VRFY command.
27722 .section "ACL verbs" "SECID200"
27723 The ACL verbs are as follows:
27726 .cindex "&%accept%& ACL verb"
27727 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
27728 of the conditions are not met, what happens depends on whether &%endpass%&
27729 appears among the conditions (for syntax see below). If the failing condition
27730 is before &%endpass%&, control is passed to the next ACL statement; if it is
27731 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
27732 check a RCPT command:
27734 accept domains = +local_domains
27738 If the recipient domain does not match the &%domains%& condition, control
27739 passes to the next statement. If it does match, the recipient is verified, and
27740 the command is accepted if verification succeeds. However, if verification
27741 fails, the ACL yields &"deny"&, because the failing condition is after
27744 The &%endpass%& feature has turned out to be confusing to many people, so its
27745 use is not recommended nowadays. It is always possible to rewrite an ACL so
27746 that &%endpass%& is not needed, and it is no longer used in the default
27749 .cindex "&%message%& ACL modifier" "with &%accept%&"
27750 If a &%message%& modifier appears on an &%accept%& statement, its action
27751 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
27752 (when an &%accept%& verb either accepts or passes control to the next
27753 statement), &%message%& can be used to vary the message that is sent when an
27754 SMTP command is accepted. For example, in a RCPT ACL you could have:
27756 &`accept `&<&'some conditions'&>
27757 &` message = OK, I will allow you through today`&
27759 You can specify an SMTP response code, optionally followed by an &"extended
27760 response code"& at the start of the message, but the first digit must be the
27761 same as would be sent by default, which is 2 for an &%accept%& verb.
27763 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
27764 an error message that is used when access is denied. This behaviour is retained
27765 for backward compatibility, but current &"best practice"& is to avoid the use
27770 .cindex "&%defer%& ACL verb"
27771 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
27772 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
27773 &%defer%& is the same as &%deny%&, because there is no way of sending a
27774 temporary error. For a RCPT command, &%defer%& is much the same as using a
27775 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
27776 be used in any ACL, and even for a recipient it might be a simpler approach.
27780 .cindex "&%deny%& ACL verb"
27781 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
27782 the conditions are not met, control is passed to the next ACL statement. For
27785 deny dnslists = blackholes.mail-abuse.org
27787 rejects commands from hosts that are on a DNS black list.
27791 .cindex "&%discard%& ACL verb"
27792 &%discard%&: This verb behaves like &%accept%&, except that it returns
27793 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
27794 that are concerned with receiving messages. When all the conditions are true,
27795 the sending entity receives a &"success"& response. However, &%discard%& causes
27796 recipients to be discarded. If it is used in an ACL for RCPT, just the one
27797 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
27798 message's recipients are discarded. Recipients that are discarded before DATA
27799 do not appear in the log line when the &%received_recipients%& log selector is set.
27801 If the &%log_message%& modifier is set when &%discard%& operates,
27802 its contents are added to the line that is automatically written to the log.
27803 The &%message%& modifier operates exactly as it does for &%accept%&.
27807 .cindex "&%drop%& ACL verb"
27808 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
27809 forcibly closed after the 5&'xx'& error message has been sent. For example:
27811 drop message = I don't take more than 20 RCPTs
27812 condition = ${if > {$rcpt_count}{20}}
27814 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
27815 The connection is always dropped after sending a 550 response.
27818 .cindex "&%require%& ACL verb"
27819 &%require%&: If all the conditions are met, control is passed to the next ACL
27820 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
27821 example, when checking a RCPT command,
27823 require message = Sender did not verify
27826 passes control to subsequent statements only if the message's sender can be
27827 verified. Otherwise, it rejects the command. Note the positioning of the
27828 &%message%& modifier, before the &%verify%& condition. The reason for this is
27829 discussed in section &<<SECTcondmodproc>>&.
27832 .cindex "&%warn%& ACL verb"
27833 &%warn%&: If all the conditions are true, a line specified by the
27834 &%log_message%& modifier is written to Exim's main log. Control always passes
27835 to the next ACL statement. If any condition is false, the log line is not
27836 written. If an identical log line is requested several times in the same
27837 message, only one copy is actually written to the log. If you want to force
27838 duplicates to be written, use the &%logwrite%& modifier instead.
27840 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
27841 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
27842 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
27843 first failing condition. There is more about adding header lines in section
27844 &<<SECTaddheadacl>>&.
27846 If any condition on a &%warn%& statement cannot be completed (that is, there is
27847 some sort of defer), the log line specified by &%log_message%& is not written.
27848 This does not include the case of a forced failure from a lookup, which
27849 is considered to be a successful completion. After a defer, no further
27850 conditions or modifiers in the &%warn%& statement are processed. The incident
27851 is logged, and the ACL continues to be processed, from the next statement
27855 .vindex "&$acl_verify_message$&"
27856 When one of the &%warn%& conditions is an address verification that fails, the
27857 text of the verification failure message is in &$acl_verify_message$&. If you
27858 want this logged, you must set it up explicitly. For example:
27860 warn !verify = sender
27861 log_message = sender verify failed: $acl_verify_message
27865 At the end of each ACL there is an implicit unconditional &%deny%&.
27867 As you can see from the examples above, the conditions and modifiers are
27868 written one to a line, with the first one on the same line as the verb, and
27869 subsequent ones on following lines. If you have a very long condition, you can
27870 continue it onto several physical lines by the usual backslash continuation
27871 mechanism. It is conventional to align the conditions vertically.
27875 .section "ACL variables" "SECTaclvariables"
27876 .cindex "&ACL;" "variables"
27877 There are some special variables that can be set during ACL processing. They
27878 can be used to pass information between different ACLs, different invocations
27879 of the same ACL in the same SMTP connection, and between ACLs and the routers,
27880 transports, and filters that are used to deliver a message. The names of these
27881 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
27882 an underscore, but the remainder of the name can be any sequence of
27883 alphanumeric characters and underscores that you choose. There is no limit on
27884 the number of ACL variables. The two sets act as follows:
27886 The values of those variables whose names begin with &$acl_c$& persist
27887 throughout an SMTP connection. They are never reset. Thus, a value that is set
27888 while receiving one message is still available when receiving the next message
27889 on the same SMTP connection.
27891 The values of those variables whose names begin with &$acl_m$& persist only
27892 while a message is being received. They are reset afterwards. They are also
27893 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
27896 When a message is accepted, the current values of all the ACL variables are
27897 preserved with the message and are subsequently made available at delivery
27898 time. The ACL variables are set by a modifier called &%set%&. For example:
27900 accept hosts = whatever
27901 set acl_m4 = some value
27902 accept authenticated = *
27903 set acl_c_auth = yes
27905 &*Note*&: A leading dollar sign is not used when naming a variable that is to
27906 be set. If you want to set a variable without taking any action, you can use a
27907 &%warn%& verb without any other modifiers or conditions.
27909 .oindex &%strict_acl_vars%&
27910 What happens if a syntactically valid but undefined ACL variable is
27911 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
27912 false (the default), an empty string is substituted; if it is true, an
27913 error is generated.
27915 Versions of Exim before 4.64 have a limited set of numbered variables, but
27916 their names are compatible, so there is no problem with upgrading.
27919 .section "Condition and modifier processing" "SECTcondmodproc"
27920 .cindex "&ACL;" "conditions; processing"
27921 .cindex "&ACL;" "modifiers; processing"
27922 An exclamation mark preceding a condition negates its result. For example:
27924 deny domains = *.dom.example
27925 !verify = recipient
27927 causes the ACL to return &"deny"& if the recipient domain ends in
27928 &'dom.example'& and the recipient address cannot be verified. Sometimes
27929 negation can be used on the right-hand side of a condition. For example, these
27930 two statements are equivalent:
27932 deny hosts = !192.168.3.4
27933 deny !hosts = 192.168.3.4
27935 However, for many conditions (&%verify%& being a good example), only left-hand
27936 side negation of the whole condition is possible.
27938 The arguments of conditions and modifiers are expanded. A forced failure
27939 of an expansion causes a condition to be ignored, that is, it behaves as if the
27940 condition is true. Consider these two statements:
27942 accept senders = ${lookup{$host_name}lsearch\
27943 {/some/file}{$value}fail}
27944 accept senders = ${lookup{$host_name}lsearch\
27945 {/some/file}{$value}{}}
27947 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
27948 the returned list is searched, but if the lookup fails the behaviour is
27949 different in the two cases. The &%fail%& in the first statement causes the
27950 condition to be ignored, leaving no further conditions. The &%accept%& verb
27951 therefore succeeds. The second statement, however, generates an empty list when
27952 the lookup fails. No sender can match an empty list, so the condition fails,
27953 and therefore the &%accept%& also fails.
27955 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
27956 specify actions that are taken as the conditions for a statement are checked;
27957 others specify text for messages that are used when access is denied or a
27958 warning is generated. The &%control%& modifier affects the way an incoming
27959 message is handled.
27961 The positioning of the modifiers in an ACL statement is important, because the
27962 processing of a verb ceases as soon as its outcome is known. Only those
27963 modifiers that have already been encountered will take effect. For example,
27964 consider this use of the &%message%& modifier:
27966 require message = Can't verify sender
27968 message = Can't verify recipient
27970 message = This message cannot be used
27972 If sender verification fails, Exim knows that the result of the statement is
27973 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
27974 so its text is used as the error message. If sender verification succeeds, but
27975 recipient verification fails, the second message is used. If recipient
27976 verification succeeds, the third message becomes &"current"&, but is never used
27977 because there are no more conditions to cause failure.
27979 For the &%deny%& verb, on the other hand, it is always the last &%message%&
27980 modifier that is used, because all the conditions must be true for rejection to
27981 happen. Specifying more than one &%message%& modifier does not make sense, and
27982 the message can even be specified after all the conditions. For example:
27985 !senders = *@my.domain.example
27986 message = Invalid sender from client host
27988 The &"deny"& result does not happen until the end of the statement is reached,
27989 by which time Exim has set up the message.
27993 .section "ACL modifiers" "SECTACLmodi"
27994 .cindex "&ACL;" "modifiers; list of"
27995 The ACL modifiers are as follows:
27998 .vitem &*add_header*&&~=&~<&'text'&>
27999 This modifier specifies one or more header lines that are to be added to an
28000 incoming message, assuming, of course, that the message is ultimately
28001 accepted. For details, see section &<<SECTaddheadacl>>&.
28003 .vitem &*continue*&&~=&~<&'text'&>
28004 .cindex "&%continue%& ACL modifier"
28005 .cindex "database" "updating in ACL"
28006 This modifier does nothing of itself, and processing of the ACL always
28007 continues with the next condition or modifier. The value of &%continue%& is in
28008 the side effects of expanding its argument. Typically this could be used to
28009 update a database. It is really just a syntactic tidiness, to avoid having to
28010 write rather ugly lines like this:
28012 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
28014 Instead, all you need is
28016 &`continue = `&<&'some expansion'&>
28019 .vitem &*control*&&~=&~<&'text'&>
28020 .cindex "&%control%& ACL modifier"
28021 This modifier affects the subsequent processing of the SMTP connection or of an
28022 incoming message that is accepted. The effect of the first type of control
28023 lasts for the duration of the connection, whereas the effect of the second type
28024 lasts only until the current message has been received. The message-specific
28025 controls always apply to the whole message, not to individual recipients,
28026 even if the &%control%& modifier appears in a RCPT ACL.
28028 As there are now quite a few controls that can be applied, they are described
28029 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
28030 in several different ways. For example:
28032 . ==== As this is a nested list, any displays it contains must be indented
28033 . ==== as otherwise they are too far to the left. That comment applies only
28034 . ==== when xmlto and fop are used; formatting with sdop gets it right either
28038 It can be at the end of an &%accept%& statement:
28040 accept ...some conditions
28041 control = queue_only
28043 In this case, the control is applied when this statement yields &"accept"&, in
28044 other words, when the conditions are all true.
28047 It can be in the middle of an &%accept%& statement:
28049 accept ...some conditions...
28050 control = queue_only
28051 ...some more conditions...
28053 If the first set of conditions are true, the control is applied, even if the
28054 statement does not accept because one of the second set of conditions is false.
28055 In this case, some subsequent statement must yield &"accept"& for the control
28059 It can be used with &%warn%& to apply the control, leaving the
28060 decision about accepting or denying to a subsequent verb. For
28063 warn ...some conditions...
28067 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
28068 &%logwrite%&, so it does not add anything to the message and does not write a
28072 If you want to apply a control unconditionally, you can use it with a
28073 &%require%& verb. For example:
28075 require control = no_multiline_responses
28079 .vitem &*delay*&&~=&~<&'time'&>
28080 .cindex "&%delay%& ACL modifier"
28082 This modifier may appear in any ACL except notquit. It causes Exim to wait for
28083 the time interval before proceeding. However, when testing Exim using the
28084 &%-bh%& option, the delay is not actually imposed (an appropriate message is
28085 output instead). The time is given in the usual Exim notation, and the delay
28086 happens as soon as the modifier is processed. In an SMTP session, pending
28087 output is flushed before the delay is imposed.
28089 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
28092 deny ...some conditions...
28095 The delay happens if all the conditions are true, before the statement returns
28096 &"deny"&. Compare this with:
28099 ...some conditions...
28101 which waits for 30s before processing the conditions. The &%delay%& modifier
28102 can also be used with &%warn%& and together with &%control%&:
28104 warn ...some conditions...
28110 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
28111 responses to several commands are no longer buffered and sent in one packet (as
28112 they would normally be) because all output is flushed before imposing the
28113 delay. This optimization is disabled so that a number of small delays do not
28114 appear to the client as one large aggregated delay that might provoke an
28115 unwanted timeout. You can, however, disable output flushing for &%delay%& by
28116 using a &%control%& modifier to set &%no_delay_flush%&.
28120 .cindex "&%endpass%& ACL modifier"
28121 This modifier, which has no argument, is recognized only in &%accept%& and
28122 &%discard%& statements. It marks the boundary between the conditions whose
28123 failure causes control to pass to the next statement, and the conditions whose
28124 failure causes the ACL to return &"deny"&. This concept has proved to be
28125 confusing to some people, so the use of &%endpass%& is no longer recommended as
28126 &"best practice"&. See the description of &%accept%& above for more details.
28129 .vitem &*log_message*&&~=&~<&'text'&>
28130 .cindex "&%log_message%& ACL modifier"
28131 This modifier sets up a message that is used as part of the log message if the
28132 ACL denies access or a &%warn%& statement's conditions are true. For example:
28134 require log_message = wrong cipher suite $tls_in_cipher
28135 encrypted = DES-CBC3-SHA
28137 &%log_message%& is also used when recipients are discarded by &%discard%&. For
28140 &`discard `&<&'some conditions'&>
28141 &` log_message = Discarded $local_part@$domain because...`&
28143 When access is denied, &%log_message%& adds to any underlying error message
28144 that may exist because of a condition failure. For example, while verifying a
28145 recipient address, a &':fail:'& redirection might have already set up a
28148 The message may be defined before the conditions to which it applies, because
28149 the string expansion does not happen until Exim decides that access is to be
28150 denied. This means that any variables that are set by the condition are
28151 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
28152 variables are set after a DNS black list lookup succeeds. If the expansion of
28153 &%log_message%& fails, or if the result is an empty string, the modifier is
28156 .vindex "&$acl_verify_message$&"
28157 If you want to use a &%warn%& statement to log the result of an address
28158 verification, you can use &$acl_verify_message$& to include the verification
28161 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
28162 the start of the logged message. If the same warning log message is requested
28163 more than once while receiving a single email message, only one copy is
28164 actually logged. If you want to log multiple copies, use &%logwrite%& instead
28165 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
28166 is logged for a successful &%warn%& statement.
28168 If &%log_message%& is not present and there is no underlying error message (for
28169 example, from the failure of address verification), but &%message%& is present,
28170 the &%message%& text is used for logging rejections. However, if any text for
28171 logging contains newlines, only the first line is logged. In the absence of
28172 both &%log_message%& and &%message%&, a default built-in message is used for
28173 logging rejections.
28176 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
28177 .cindex "&%log_reject_target%& ACL modifier"
28178 .cindex "logging in ACL" "specifying which log"
28179 This modifier makes it possible to specify which logs are used for messages
28180 about ACL rejections. Its argument is a colon-separated list of words that can
28181 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
28182 may be empty, in which case a rejection is not logged at all. For example, this
28183 ACL fragment writes no logging information when access is denied:
28185 &`deny `&<&'some conditions'&>
28186 &` log_reject_target =`&
28188 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
28189 permanent and temporary rejections. Its effect lasts for the rest of the
28193 .vitem &*logwrite*&&~=&~<&'text'&>
28194 .cindex "&%logwrite%& ACL modifier"
28195 .cindex "logging in ACL" "immediate"
28196 This modifier writes a message to a log file as soon as it is encountered when
28197 processing an ACL. (Compare &%log_message%&, which, except in the case of
28198 &%warn%& and &%discard%&, is used only if the ACL statement denies
28199 access.) The &%logwrite%& modifier can be used to log special incidents in
28202 &`accept `&<&'some special conditions'&>
28203 &` control = freeze`&
28204 &` logwrite = froze message because ...`&
28206 By default, the message is written to the main log. However, it may begin
28207 with a colon, followed by a comma-separated list of log names, and then
28208 another colon, to specify exactly which logs are to be written. For
28211 logwrite = :main,reject: text for main and reject logs
28212 logwrite = :panic: text for panic log only
28216 .vitem &*message*&&~=&~<&'text'&>
28217 .cindex "&%message%& ACL modifier"
28218 This modifier sets up a text string that is expanded and used as a response
28219 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
28220 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
28221 there is some complication if &%endpass%& is involved; see the description of
28222 &%accept%& for details.)
28224 The expansion of the message happens at the time Exim decides that the ACL is
28225 to end, not at the time it processes &%message%&. If the expansion fails, or
28226 generates an empty string, the modifier is ignored. Here is an example where
28227 &%message%& must be specified first, because the ACL ends with a rejection if
28228 the &%hosts%& condition fails:
28230 require message = Host not recognized
28233 (Once a condition has failed, no further conditions or modifiers are
28236 .cindex "SMTP" "error codes"
28237 .oindex "&%smtp_banner%&
28238 For ACLs that are triggered by SMTP commands, the message is returned as part
28239 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
28240 is meaningful only for SMTP, as no message is returned when a non-SMTP message
28241 is accepted. In the case of the connect ACL, accepting with a message modifier
28242 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
28243 accept message may not contain more than one line (otherwise it will be
28244 truncated at the first newline and a panic logged), and it cannot affect the
28247 When SMTP is involved, the message may begin with an overriding response code,
28248 consisting of three digits optionally followed by an &"extended response code"&
28249 of the form &'n.n.n'&, each code being followed by a space. For example:
28251 deny message = 599 1.2.3 Host not welcome
28252 hosts = 192.168.34.0/24
28254 The first digit of the supplied response code must be the same as would be sent
28255 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
28256 access, but for the predata ACL, note that the default success code is 354, not
28259 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
28260 the message modifier cannot override the 221 response code.
28262 The text in a &%message%& modifier is literal; any quotes are taken as
28263 literals, but because the string is expanded, backslash escapes are processed
28264 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
28267 .vindex "&$acl_verify_message$&"
28268 For ACLs that are called by an &%acl =%& ACL condition, the message is
28269 stored in &$acl_verify_message$&, from which the calling ACL may use it.
28271 If &%message%& is used on a statement that verifies an address, the message
28272 specified overrides any message that is generated by the verification process.
28273 However, the original message is available in the variable
28274 &$acl_verify_message$&, so you can incorporate it into your message if you
28275 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
28276 routers to be passed back as part of the SMTP response, you should either not
28277 use a &%message%& modifier, or make use of &$acl_verify_message$&.
28279 For compatibility with previous releases of Exim, a &%message%& modifier that
28280 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
28281 modifier, but this usage is now deprecated. However, &%message%& acts only when
28282 all the conditions are true, wherever it appears in an ACL command, whereas
28283 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
28284 &%warn%& in an ACL that is not concerned with receiving a message, it has no
28288 .vitem &*remove_header*&&~=&~<&'text'&>
28289 This modifier specifies one or more header names in a colon-separated list
28290 that are to be removed from an incoming message, assuming, of course, that
28291 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
28294 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
28295 .cindex "&%set%& ACL modifier"
28296 This modifier puts a value into one of the ACL variables (see section
28297 &<<SECTaclvariables>>&).
28300 .vitem &*udpsend*&&~=&~<&'parameters'&>
28301 This modifier sends a UDP packet, for purposes such as statistics
28302 collection or behaviour monitoring. The parameters are expanded, and
28303 the result of the expansion must be a colon-separated list consisting
28304 of a destination server, port number, and the packet contents. The
28305 server can be specified as a host name or IPv4 or IPv6 address. The
28306 separator can be changed with the usual angle bracket syntax. For
28307 example, you might want to collect information on which hosts connect
28310 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
28311 $tod_zulu $sender_host_address
28318 .section "Use of the control modifier" "SECTcontrols"
28319 .cindex "&%control%& ACL modifier"
28320 The &%control%& modifier supports the following settings:
28323 .vitem &*control&~=&~allow_auth_unadvertised*&
28324 This modifier allows a client host to use the SMTP AUTH command even when it
28325 has not been advertised in response to EHLO. Furthermore, because there are
28326 apparently some really broken clients that do this, Exim will accept AUTH after
28327 HELO (rather than EHLO) when this control is set. It should be used only if you
28328 really need it, and you should limit its use to those broken clients that do
28329 not work without it. For example:
28331 warn hosts = 192.168.34.25
28332 control = allow_auth_unadvertised
28334 Normally, when an Exim server receives an AUTH command, it checks the name of
28335 the authentication mechanism that is given in the command to ensure that it
28336 matches an advertised mechanism. When this control is set, the check that a
28337 mechanism has been advertised is bypassed. Any configured mechanism can be used
28338 by the client. This control is permitted only in the connection and HELO ACLs.
28341 .vitem &*control&~=&~caseful_local_part*& &&&
28342 &*control&~=&~caselower_local_part*&
28343 .cindex "&ACL;" "case of local part in"
28344 .cindex "case of local parts"
28345 .vindex "&$local_part$&"
28346 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
28347 (that is, during RCPT processing). By default, the contents of &$local_part$&
28348 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
28349 any uppercase letters in the original local part are restored in &$local_part$&
28350 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
28353 These controls affect only the current recipient. Moreover, they apply only to
28354 local part handling that takes place directly in the ACL (for example, as a key
28355 in lookups). If a test to verify the recipient is obeyed, the case-related
28356 handling of the local part during the verification is controlled by the router
28357 configuration (see the &%caseful_local_part%& generic router option).
28359 This facility could be used, for example, to add a spam score to local parts
28360 containing upper case letters. For example, using &$acl_m4$& to accumulate the
28363 warn control = caseful_local_part
28364 set acl_m4 = ${eval:\
28366 ${if match{$local_part}{[A-Z]}{1}{0}}\
28368 control = caselower_local_part
28370 Notice that we put back the lower cased version afterwards, assuming that
28371 is what is wanted for subsequent tests.
28374 .vitem &*control&~=&~cutthrough_delivery*&
28375 .cindex "&ACL;" "cutthrough routing"
28376 .cindex "cutthrough" "requesting"
28377 This option requests delivery be attempted while the item is being received.
28379 The option is usable in the RCPT ACL.
28380 If enabled for a message received via smtp and routed to an smtp transport,
28381 and only one transport, interface, destination host and port combination
28382 is used for all recipients of the message,
28383 then the delivery connection is made while the receiving connection is open
28384 and data is copied from one to the other.
28386 An attempt to set this option for any recipient but the first
28387 for a mail will be quietly ignored.
28388 If a recipient-verify callout connection is subsequently
28389 requested in the same ACL it is held open and used for
28390 any subsequent recipients and the data,
28391 otherwise one is made after the initial RCPT ACL completes.
28393 Note that routers are used in verify mode,
28394 and cannot depend on content of received headers.
28395 Note also that headers cannot be
28396 modified by any of the post-data ACLs (DATA, MIME and DKIM).
28397 Headers may be modified by routers (subject to the above) and transports.
28399 Cutthrough delivery is not supported via transport-filters or when DKIM signing
28400 of outgoing messages is done, because it sends data to the ultimate destination
28401 before the entire message has been received from the source.
28402 It is not supported for messages received with the SMTP PRDR option in use.
28404 Should the ultimate destination system positively accept or reject the mail,
28405 a corresponding indication is given to the source system and nothing is queued.
28406 If there is a temporary error the item is queued for later delivery in the
28407 usual fashion. If the item is successfully delivered in cutthrough mode
28408 the delivery log lines are tagged with ">>" rather than "=>" and appear
28409 before the acceptance "<=" line.
28411 Delivery in this mode avoids the generation of a bounce mail to a
28413 sender when the destination system is doing content-scan based rejection.
28416 .vitem &*control&~=&~debug/*&<&'options'&>
28417 .cindex "&ACL;" "enabling debug logging"
28418 .cindex "debugging" "enabling from an ACL"
28419 This control turns on debug logging, almost as though Exim had been invoked
28420 with &`-d`&, with the output going to a new logfile, by default called
28421 &'debuglog'&. The filename can be adjusted with the &'tag'& option, which
28422 may access any variables already defined. The logging may be adjusted with
28423 the &'opts'& option, which takes the same values as the &`-d`& command-line
28424 option. Some examples (which depend on variables that don't exist in all
28428 control = debug/tag=.$sender_host_address
28429 control = debug/opts=+expand+acl
28430 control = debug/tag=.$message_exim_id/opts=+expand
28434 .vitem &*control&~=&~dkim_disable_verify*&
28435 .cindex "disable DKIM verify"
28436 .cindex "DKIM" "disable verify"
28437 This control turns off DKIM verification processing entirely. For details on
28438 the operation and configuration of DKIM, see chapter &<<CHAPdkim>>&.
28441 .vitem &*control&~=&~dscp/*&<&'value'&>
28442 .cindex "&ACL;" "setting DSCP value"
28443 .cindex "DSCP" "inbound"
28444 This option causes the DSCP value associated with the socket for the inbound
28445 connection to be adjusted to a given value, given as one of a number of fixed
28446 strings or to numeric value.
28447 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
28448 Common values include &`throughput`&, &`mincost`&, and on newer systems
28449 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
28451 The outbound packets from Exim will be marked with this value in the header
28452 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
28453 that these values will have any effect, not be stripped by networking
28454 equipment, or do much of anything without cooperation with your Network
28455 Engineer and those of all network operators between the source and destination.
28458 .vitem &*control&~=&~enforce_sync*& &&&
28459 &*control&~=&~no_enforce_sync*&
28460 .cindex "SMTP" "synchronization checking"
28461 .cindex "synchronization checking in SMTP"
28462 These controls make it possible to be selective about when SMTP synchronization
28463 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
28464 state of the switch (it is true by default). See the description of this option
28465 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
28467 The effect of these two controls lasts for the remainder of the SMTP
28468 connection. They can appear in any ACL except the one for the non-SMTP
28469 messages. The most straightforward place to put them is in the ACL defined by
28470 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
28471 before the first synchronization check. The expected use is to turn off the
28472 synchronization checks for badly-behaved hosts that you nevertheless need to
28476 .vitem &*control&~=&~fakedefer/*&<&'message'&>
28477 .cindex "fake defer"
28478 .cindex "defer, fake"
28479 This control works in exactly the same way as &%fakereject%& (described below)
28480 except that it causes an SMTP 450 response after the message data instead of a
28481 550 response. You must take care when using &%fakedefer%& because it causes the
28482 messages to be duplicated when the sender retries. Therefore, you should not
28483 use &%fakedefer%& if the message is to be delivered normally.
28485 .vitem &*control&~=&~fakereject/*&<&'message'&>
28486 .cindex "fake rejection"
28487 .cindex "rejection, fake"
28488 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
28489 words, only when an SMTP message is being received. If Exim accepts the
28490 message, instead the final 250 response, a 550 rejection message is sent.
28491 However, Exim proceeds to deliver the message as normal. The control applies
28492 only to the current message, not to any subsequent ones that may be received in
28493 the same SMTP connection.
28495 The text for the 550 response is taken from the &%control%& modifier. If no
28496 message is supplied, the following is used:
28498 550-Your message has been rejected but is being
28499 550-kept for evaluation.
28500 550-If it was a legitimate message, it may still be
28501 550 delivered to the target recipient(s).
28503 This facility should be used with extreme caution.
28505 .vitem &*control&~=&~freeze*&
28506 .cindex "frozen messages" "forcing in ACL"
28507 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
28508 other words, only when a message is being received. If the message is accepted,
28509 it is placed on Exim's queue and frozen. The control applies only to the
28510 current message, not to any subsequent ones that may be received in the same
28513 This modifier can optionally be followed by &`/no_tell`&. If the global option
28514 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
28515 is told about the freezing), provided all the &*control=freeze*& modifiers that
28516 are obeyed for the current message have the &`/no_tell`& option.
28518 .vitem &*control&~=&~no_delay_flush*&
28519 .cindex "SMTP" "output flushing, disabling for delay"
28520 Exim normally flushes SMTP output before implementing a delay in an ACL, to
28521 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
28522 use. This control, as long as it is encountered before the &%delay%& modifier,
28523 disables such output flushing.
28525 .vitem &*control&~=&~no_callout_flush*&
28526 .cindex "SMTP" "output flushing, disabling for callout"
28527 Exim normally flushes SMTP output before performing a callout in an ACL, to
28528 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
28529 use. This control, as long as it is encountered before the &%verify%& condition
28530 that causes the callout, disables such output flushing.
28532 .vitem &*control&~=&~no_mbox_unspool*&
28533 This control is available when Exim is compiled with the content scanning
28534 extension. Content scanning may require a copy of the current message, or parts
28535 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
28536 or spam scanner. Normally, such copies are deleted when they are no longer
28537 needed. If this control is set, the copies are not deleted. The control applies
28538 only to the current message, not to any subsequent ones that may be received in
28539 the same SMTP connection. It is provided for debugging purposes and is unlikely
28540 to be useful in production.
28542 .vitem &*control&~=&~no_multiline_responses*&
28543 .cindex "multiline responses, suppressing"
28544 This control is permitted for any ACL except the one for non-SMTP messages.
28545 It seems that there are broken clients in use that cannot handle multiline
28546 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
28548 If this control is set, multiline SMTP responses from ACL rejections are
28549 suppressed. One way of doing this would have been to put out these responses as
28550 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
28551 (&"use multiline responses for more"& it says &-- ha!), and some of the
28552 responses might get close to that. So this facility, which is after all only a
28553 sop to broken clients, is implemented by doing two very easy things:
28556 Extra information that is normally output as part of a rejection caused by
28557 sender verification failure is omitted. Only the final line (typically &"sender
28558 verification failed"&) is sent.
28560 If a &%message%& modifier supplies a multiline response, only the first
28564 The setting of the switch can, of course, be made conditional on the
28565 calling host. Its effect lasts until the end of the SMTP connection.
28567 .vitem &*control&~=&~no_pipelining*&
28568 .cindex "PIPELINING" "suppressing advertising"
28569 This control turns off the advertising of the PIPELINING extension to SMTP in
28570 the current session. To be useful, it must be obeyed before Exim sends its
28571 response to an EHLO command. Therefore, it should normally appear in an ACL
28572 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
28573 &%pipelining_advertise_hosts%&.
28575 .vitem &*control&~=&~queue_only*&
28576 .oindex "&%queue_only%&"
28577 .cindex "queueing incoming messages"
28578 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
28579 other words, only when a message is being received. If the message is accepted,
28580 it is placed on Exim's queue and left there for delivery by a subsequent queue
28581 runner. No immediate delivery process is started. In other words, it has the
28582 effect as the &%queue_only%& global option. However, the control applies only
28583 to the current message, not to any subsequent ones that may be received in the
28584 same SMTP connection.
28586 .vitem &*control&~=&~submission/*&<&'options'&>
28587 .cindex "message" "submission"
28588 .cindex "submission mode"
28589 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
28590 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
28591 the current message is a submission from a local MUA. In this case, Exim
28592 operates in &"submission mode"&, and applies certain fixups to the message if
28593 necessary. For example, it adds a &'Date:'& header line if one is not present.
28594 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
28595 late (the message has already been created).
28597 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
28598 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
28599 submission mode; the available options for this control are described there.
28600 The control applies only to the current message, not to any subsequent ones
28601 that may be received in the same SMTP connection.
28603 .vitem &*control&~=&~suppress_local_fixups*&
28604 .cindex "submission fixups, suppressing"
28605 This control applies to locally submitted (non TCP/IP) messages, and is the
28606 complement of &`control = submission`&. It disables the fixups that are
28607 normally applied to locally-submitted messages. Specifically:
28610 Any &'Sender:'& header line is left alone (in this respect, it is a
28611 dynamic version of &%local_sender_retain%&).
28613 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
28615 There is no check that &'From:'& corresponds to the actual sender.
28618 This control may be useful when a remotely-originated message is accepted,
28619 passed to some scanning program, and then re-submitted for delivery. It can be
28620 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
28621 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
28624 &*Note:*& This control applies only to the current message, not to any others
28625 that are being submitted at the same time using &%-bs%& or &%-bS%&.
28629 .section "Summary of message fixup control" "SECTsummesfix"
28630 All four possibilities for message fixups can be specified:
28633 Locally submitted, fixups applied: the default.
28635 Locally submitted, no fixups applied: use
28636 &`control = suppress_local_fixups`&.
28638 Remotely submitted, no fixups applied: the default.
28640 Remotely submitted, fixups applied: use &`control = submission`&.
28645 .section "Adding header lines in ACLs" "SECTaddheadacl"
28646 .cindex "header lines" "adding in an ACL"
28647 .cindex "header lines" "position of added lines"
28648 .cindex "&%add_header%& ACL modifier"
28649 The &%add_header%& modifier can be used to add one or more extra header lines
28650 to an incoming message, as in this example:
28652 warn dnslists = sbl.spamhaus.org : \
28653 dialup.mail-abuse.org
28654 add_header = X-blacklisted-at: $dnslist_domain
28656 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
28657 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
28658 receiving a message). The message must ultimately be accepted for
28659 &%add_header%& to have any significant effect. You can use &%add_header%& with
28660 any ACL verb, including &%deny%& (though this is potentially useful only in a
28663 Headers will not be added to the message if the modifier is used in
28664 DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing.
28666 Leading and trailing newlines are removed from
28667 the data for the &%add_header%& modifier; if it then
28668 contains one or more newlines that
28669 are not followed by a space or a tab, it is assumed to contain multiple header
28670 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
28671 front of any line that is not a valid header line.
28673 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
28674 They are added to the message before processing the DATA and MIME ACLs.
28675 However, if an identical header line is requested more than once, only one copy
28676 is actually added to the message. Further header lines may be accumulated
28677 during the DATA and MIME ACLs, after which they are added to the message, again
28678 with duplicates suppressed. Thus, it is possible to add two identical header
28679 lines to an SMTP message, but only if one is added before DATA and one after.
28680 In the case of non-SMTP messages, new headers are accumulated during the
28681 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
28682 message is rejected after DATA or by the non-SMTP ACL, all added header lines
28683 are included in the entry that is written to the reject log.
28685 .cindex "header lines" "added; visibility of"
28686 Header lines are not visible in string expansions
28688 until they are added to the
28689 message. It follows that header lines defined in the MAIL, RCPT, and predata
28690 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
28691 header lines that are added by the DATA or MIME ACLs are not visible in those
28692 ACLs. Because of this restriction, you cannot use header lines as a way of
28693 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
28694 this, you can use ACL variables, as described in section
28695 &<<SECTaclvariables>>&.
28697 The list of headers yet to be added is given by the &%$headers_added%& variable.
28699 The &%add_header%& modifier acts immediately as it is encountered during the
28700 processing of an ACL. Notice the difference between these two cases:
28702 &`accept add_header = ADDED: some text`&
28703 &` `&<&'some condition'&>
28705 &`accept `&<&'some condition'&>
28706 &` add_header = ADDED: some text`&
28708 In the first case, the header line is always added, whether or not the
28709 condition is true. In the second case, the header line is added only if the
28710 condition is true. Multiple occurrences of &%add_header%& may occur in the same
28711 ACL statement. All those that are encountered before a condition fails are
28714 .cindex "&%warn%& ACL verb"
28715 For compatibility with previous versions of Exim, a &%message%& modifier for a
28716 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
28717 effect only if all the conditions are true, even if it appears before some of
28718 them. Furthermore, only the last occurrence of &%message%& is honoured. This
28719 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
28720 are present on a &%warn%& verb, both are processed according to their
28723 By default, new header lines are added to a message at the end of the existing
28724 header lines. However, you can specify that any particular header line should
28725 be added right at the start (before all the &'Received:'& lines), immediately
28726 after the first block of &'Received:'& lines, or immediately before any line
28727 that is not a &'Received:'& or &'Resent-something:'& header.
28729 This is done by specifying &":at_start:"&, &":after_received:"&, or
28730 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
28731 header line, respectively. (Header text cannot start with a colon, as there has
28732 to be a header name first.) For example:
28734 warn add_header = \
28735 :after_received:X-My-Header: something or other...
28737 If more than one header line is supplied in a single &%add_header%& modifier,
28738 each one is treated independently and can therefore be placed differently. If
28739 you add more than one line at the start, or after the Received: block, they end
28740 up in reverse order.
28742 &*Warning*&: This facility currently applies only to header lines that are
28743 added in an ACL. It does NOT work for header lines that are added in a
28744 system filter or in a router or transport.
28748 .section "Removing header lines in ACLs" "SECTremoveheadacl"
28749 .cindex "header lines" "removing in an ACL"
28750 .cindex "header lines" "position of removed lines"
28751 .cindex "&%remove_header%& ACL modifier"
28752 The &%remove_header%& modifier can be used to remove one or more header lines
28753 from an incoming message, as in this example:
28755 warn message = Remove internal headers
28756 remove_header = x-route-mail1 : x-route-mail2
28758 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
28759 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
28760 receiving a message). The message must ultimately be accepted for
28761 &%remove_header%& to have any significant effect. You can use &%remove_header%&
28762 with any ACL verb, including &%deny%&, though this is really not useful for
28763 any verb that doesn't result in a delivered message.
28765 Headers will not be removed to the message if the modifier is used in
28766 DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing.
28768 More than one header can be removed at the same time by using a colon separated
28769 list of header names. The header matching is case insensitive. Wildcards are
28770 not permitted, nor is list expansion performed, so you cannot use hostlists to
28771 create a list of headers, however both connection and message variable expansion
28772 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
28774 warn hosts = +internal_hosts
28775 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
28776 warn message = Remove internal headers
28777 remove_header = $acl_c_ihdrs
28779 Removed header lines are accumulated during the MAIL, RCPT, and predata ACLs.
28780 They are removed from the message before processing the DATA and MIME ACLs.
28781 There is no harm in attempting to remove the same header twice nor is removing
28782 a non-existent header. Further header lines to be removed may be accumulated
28783 during the DATA and MIME ACLs, after which they are removed from the message,
28784 if present. In the case of non-SMTP messages, headers to be removed are
28785 accumulated during the non-SMTP ACLs, and are removed from the message after
28786 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
28787 ACL, there really is no effect because there is no logging of what headers
28788 would have been removed.
28790 .cindex "header lines" "removed; visibility of"
28791 Header lines are not visible in string expansions until the DATA phase when it
28792 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
28793 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
28794 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
28795 this restriction, you cannot use header lines as a way of controlling data
28796 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
28797 you should instead use ACL variables, as described in section
28798 &<<SECTaclvariables>>&.
28800 The &%remove_header%& modifier acts immediately as it is encountered during the
28801 processing of an ACL. Notice the difference between these two cases:
28803 &`accept remove_header = X-Internal`&
28804 &` `&<&'some condition'&>
28806 &`accept `&<&'some condition'&>
28807 &` remove_header = X-Internal`&
28809 In the first case, the header line is always removed, whether or not the
28810 condition is true. In the second case, the header line is removed only if the
28811 condition is true. Multiple occurrences of &%remove_header%& may occur in the
28812 same ACL statement. All those that are encountered before a condition fails
28815 &*Warning*&: This facility currently applies only to header lines that are
28816 present during ACL processing. It does NOT remove header lines that are added
28817 in a system filter or in a router or transport.
28822 .section "ACL conditions" "SECTaclconditions"
28823 .cindex "&ACL;" "conditions; list of"
28824 Some of the conditions listed in this section are available only when Exim is
28825 compiled with the content-scanning extension. They are included here briefly
28826 for completeness. More detailed descriptions can be found in the discussion on
28827 content scanning in chapter &<<CHAPexiscan>>&.
28829 Not all conditions are relevant in all circumstances. For example, testing
28830 senders and recipients does not make sense in an ACL that is being run as the
28831 result of the arrival of an ETRN command, and checks on message headers can be
28832 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
28833 can use the same condition (with different parameters) more than once in the
28834 same ACL statement. This provides a way of specifying an &"and"& conjunction.
28835 The conditions are as follows:
28839 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
28840 .cindex "&ACL;" "nested"
28841 .cindex "&ACL;" "indirect"
28842 .cindex "&ACL;" "arguments"
28843 .cindex "&%acl%& ACL condition"
28844 The possible values of the argument are the same as for the
28845 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
28846 &"accept"& the condition is true; if it returns &"deny"& the condition is
28847 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
28848 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
28849 condition false. This means that further processing of the &%warn%& verb
28850 ceases, but processing of the ACL continues.
28852 If the argument is a named ACL, up to nine space-separated optional values
28853 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
28854 and $acl_narg is set to the count of values.
28855 Previous values of these variables are restored after the call returns.
28856 The name and values are expanded separately.
28857 Note that spaces in complex expansions which are used as arguments
28858 will act as argument separators.
28860 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
28861 the connection is dropped. If it returns &"discard"&, the verb must be
28862 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
28863 conditions are tested.
28865 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
28866 loops. This condition allows you to use different ACLs in different
28867 circumstances. For example, different ACLs can be used to handle RCPT commands
28868 for different local users or different local domains.
28870 .vitem &*authenticated&~=&~*&<&'string&~list'&>
28871 .cindex "&%authenticated%& ACL condition"
28872 .cindex "authentication" "ACL checking"
28873 .cindex "&ACL;" "testing for authentication"
28874 If the SMTP connection is not authenticated, the condition is false. Otherwise,
28875 the name of the authenticator is tested against the list. To test for
28876 authentication by any authenticator, you can set
28881 .vitem &*condition&~=&~*&<&'string'&>
28882 .cindex "&%condition%& ACL condition"
28883 .cindex "customizing" "ACL condition"
28884 .cindex "&ACL;" "customized test"
28885 .cindex "&ACL;" "testing, customized"
28886 This feature allows you to make up custom conditions. If the result of
28887 expanding the string is an empty string, the number zero, or one of the strings
28888 &"no"& or &"false"&, the condition is false. If the result is any non-zero
28889 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
28890 any other value, some error is assumed to have occurred, and the ACL returns
28891 &"defer"&. However, if the expansion is forced to fail, the condition is
28892 ignored. The effect is to treat it as true, whether it is positive or
28895 .vitem &*decode&~=&~*&<&'location'&>
28896 .cindex "&%decode%& ACL condition"
28897 This condition is available only when Exim is compiled with the
28898 content-scanning extension, and it is allowed only in the ACL defined by
28899 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
28900 If all goes well, the condition is true. It is false only if there are
28901 problems such as a syntax error or a memory shortage. For more details, see
28902 chapter &<<CHAPexiscan>>&.
28904 .vitem &*demime&~=&~*&<&'extension&~list'&>
28905 .cindex "&%demime%& ACL condition"
28906 This condition is available only when Exim is compiled with the
28907 content-scanning extension. Its use is described in section
28908 &<<SECTdemimecond>>&.
28910 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
28911 .cindex "&%dnslists%& ACL condition"
28912 .cindex "DNS list" "in ACL"
28913 .cindex "black list (DNS)"
28914 .cindex "&ACL;" "testing a DNS list"
28915 This condition checks for entries in DNS black lists. These are also known as
28916 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
28917 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
28918 different variants of this condition to describe briefly here. See sections
28919 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
28921 .vitem &*domains&~=&~*&<&'domain&~list'&>
28922 .cindex "&%domains%& ACL condition"
28923 .cindex "domain" "ACL checking"
28924 .cindex "&ACL;" "testing a recipient domain"
28925 .vindex "&$domain_data$&"
28926 This condition is relevant only after a RCPT command. It checks that the domain
28927 of the recipient address is in the domain list. If percent-hack processing is
28928 enabled, it is done before this test is done. If the check succeeds with a
28929 lookup, the result of the lookup is placed in &$domain_data$& until the next
28932 &*Note carefully*& (because many people seem to fall foul of this): you cannot
28933 use &%domains%& in a DATA ACL.
28936 .vitem &*encrypted&~=&~*&<&'string&~list'&>
28937 .cindex "&%encrypted%& ACL condition"
28938 .cindex "encryption" "checking in an ACL"
28939 .cindex "&ACL;" "testing for encryption"
28940 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
28941 name of the cipher suite in use is tested against the list. To test for
28942 encryption without testing for any specific cipher suite(s), set
28948 .vitem &*hosts&~=&~*&<&'host&~list'&>
28949 .cindex "&%hosts%& ACL condition"
28950 .cindex "host" "ACL checking"
28951 .cindex "&ACL;" "testing the client host"
28952 This condition tests that the calling host matches the host list. If you have
28953 name lookups or wildcarded host names and IP addresses in the same host list,
28954 you should normally put the IP addresses first. For example, you could have:
28956 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
28958 The lookup in this example uses the host name for its key. This is implied by
28959 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
28960 and it wouldn't matter which way round you had these two items.)
28962 The reason for the problem with host names lies in the left-to-right way that
28963 Exim processes lists. It can test IP addresses without doing any DNS lookups,
28964 but when it reaches an item that requires a host name, it fails if it cannot
28965 find a host name to compare with the pattern. If the above list is given in the
28966 opposite order, the &%accept%& statement fails for a host whose name cannot be
28967 found, even if its IP address is 10.9.8.7.
28969 If you really do want to do the name check first, and still recognize the IP
28970 address even if the name lookup fails, you can rewrite the ACL like this:
28972 accept hosts = dbm;/etc/friendly/hosts
28973 accept hosts = 10.9.8.7
28975 The default action on failing to find the host name is to assume that the host
28976 is not in the list, so the first &%accept%& statement fails. The second
28977 statement can then check the IP address.
28979 .vindex "&$host_data$&"
28980 If a &%hosts%& condition is satisfied by means of a lookup, the result
28981 of the lookup is made available in the &$host_data$& variable. This
28982 allows you, for example, to set up a statement like this:
28984 deny hosts = net-lsearch;/some/file
28985 message = $host_data
28987 which gives a custom error message for each denied host.
28989 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
28990 .cindex "&%local_parts%& ACL condition"
28991 .cindex "local part" "ACL checking"
28992 .cindex "&ACL;" "testing a local part"
28993 .vindex "&$local_part_data$&"
28994 This condition is relevant only after a RCPT command. It checks that the local
28995 part of the recipient address is in the list. If percent-hack processing is
28996 enabled, it is done before this test. If the check succeeds with a lookup, the
28997 result of the lookup is placed in &$local_part_data$&, which remains set until
28998 the next &%local_parts%& test.
29000 .vitem &*malware&~=&~*&<&'option'&>
29001 .cindex "&%malware%& ACL condition"
29002 .cindex "&ACL;" "virus scanning"
29003 .cindex "&ACL;" "scanning for viruses"
29004 This condition is available only when Exim is compiled with the
29005 content-scanning extension. It causes the incoming message to be scanned for
29006 viruses. For details, see chapter &<<CHAPexiscan>>&.
29008 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
29009 .cindex "&%mime_regex%& ACL condition"
29010 .cindex "&ACL;" "testing by regex matching"
29011 This condition is available only when Exim is compiled with the
29012 content-scanning extension, and it is allowed only in the ACL defined by
29013 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
29014 with any of the regular expressions. For details, see chapter
29017 .vitem &*ratelimit&~=&~*&<&'parameters'&>
29018 .cindex "rate limiting"
29019 This condition can be used to limit the rate at which a user or host submits
29020 messages. Details are given in section &<<SECTratelimiting>>&.
29022 .vitem &*recipients&~=&~*&<&'address&~list'&>
29023 .cindex "&%recipients%& ACL condition"
29024 .cindex "recipient" "ACL checking"
29025 .cindex "&ACL;" "testing a recipient"
29026 This condition is relevant only after a RCPT command. It checks the entire
29027 recipient address against a list of recipients.
29029 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
29030 .cindex "&%regex%& ACL condition"
29031 .cindex "&ACL;" "testing by regex matching"
29032 This condition is available only when Exim is compiled with the
29033 content-scanning extension, and is available only in the DATA, MIME, and
29034 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
29035 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
29037 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
29038 .cindex "&%sender_domains%& ACL condition"
29039 .cindex "sender" "ACL checking"
29040 .cindex "&ACL;" "testing a sender domain"
29041 .vindex "&$domain$&"
29042 .vindex "&$sender_address_domain$&"
29043 This condition tests the domain of the sender of the message against the given
29044 domain list. &*Note*&: The domain of the sender address is in
29045 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
29046 of this condition. This is an exception to the general rule for testing domain
29047 lists. It is done this way so that, if this condition is used in an ACL for a
29048 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
29049 influence the sender checking.
29051 &*Warning*&: It is a bad idea to use this condition on its own as a control on
29052 relaying, because sender addresses are easily, and commonly, forged.
29054 .vitem &*senders&~=&~*&<&'address&~list'&>
29055 .cindex "&%senders%& ACL condition"
29056 .cindex "sender" "ACL checking"
29057 .cindex "&ACL;" "testing a sender"
29058 This condition tests the sender of the message against the given list. To test
29059 for a bounce message, which has an empty sender, set
29063 &*Warning*&: It is a bad idea to use this condition on its own as a control on
29064 relaying, because sender addresses are easily, and commonly, forged.
29066 .vitem &*spam&~=&~*&<&'username'&>
29067 .cindex "&%spam%& ACL condition"
29068 .cindex "&ACL;" "scanning for spam"
29069 This condition is available only when Exim is compiled with the
29070 content-scanning extension. It causes the incoming message to be scanned by
29071 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
29073 .vitem &*verify&~=&~certificate*&
29074 .cindex "&%verify%& ACL condition"
29075 .cindex "TLS" "client certificate verification"
29076 .cindex "certificate" "verification of client"
29077 .cindex "&ACL;" "certificate verification"
29078 .cindex "&ACL;" "testing a TLS certificate"
29079 This condition is true in an SMTP session if the session is encrypted, and a
29080 certificate was received from the client, and the certificate was verified. The
29081 server requests a certificate only if the client matches &%tls_verify_hosts%&
29082 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
29084 .vitem &*verify&~=&~csa*&
29085 .cindex "CSA verification"
29086 This condition checks whether the sending host (the client) is authorized to
29087 send email. Details of how this works are given in section
29088 &<<SECTverifyCSA>>&.
29090 .vitem &*verify&~=&~header_names_ascii*&
29091 .cindex "&%verify%& ACL condition"
29092 .cindex "&ACL;" "verifying header names only ASCII"
29093 .cindex "header lines" "verifying header names only ASCII"
29094 .cindex "verifying" "header names only ASCII"
29095 This condition is relevant only in an ACL that is run after a message has been
29096 received, that is, in an ACL specified by &%acl_smtp_data%& or
29097 &%acl_not_smtp%&. It checks all header names (not the content) to make sure
29098 there are no non-ASCII characters, also excluding control characters. The
29099 allowable characters are decimal ASCII values 33 through 126.
29101 Exim itself will handle headers with non-ASCII characters, but it can cause
29102 problems for downstream applications, so this option will allow their
29103 detection and rejection in the DATA ACL's.
29105 .vitem &*verify&~=&~header_sender/*&<&'options'&>
29106 .cindex "&%verify%& ACL condition"
29107 .cindex "&ACL;" "verifying sender in the header"
29108 .cindex "header lines" "verifying the sender in"
29109 .cindex "sender" "verifying in header"
29110 .cindex "verifying" "sender in header"
29111 This condition is relevant only in an ACL that is run after a message has been
29112 received, that is, in an ACL specified by &%acl_smtp_data%& or
29113 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
29114 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
29115 is loosely thought of as a &"sender"& address (hence the name of the test).
29116 However, an address that appears in one of these headers need not be an address
29117 that accepts bounce messages; only sender addresses in envelopes are required
29118 to accept bounces. Therefore, if you use the callout option on this check, you
29119 might want to arrange for a non-empty address in the MAIL command.
29121 Details of address verification and the options are given later, starting at
29122 section &<<SECTaddressverification>>& (callouts are described in section
29123 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
29124 condition to restrict it to bounce messages only:
29127 message = A valid sender header is required for bounces
29128 !verify = header_sender
29131 .vitem &*verify&~=&~header_syntax*&
29132 .cindex "&%verify%& ACL condition"
29133 .cindex "&ACL;" "verifying header syntax"
29134 .cindex "header lines" "verifying syntax"
29135 .cindex "verifying" "header syntax"
29136 This condition is relevant only in an ACL that is run after a message has been
29137 received, that is, in an ACL specified by &%acl_smtp_data%& or
29138 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
29139 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
29140 and &'Bcc:'&), returning true if there are no problems.
29141 Unqualified addresses (local parts without domains) are
29142 permitted only in locally generated messages and from hosts that match
29143 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
29146 Note that this condition is a syntax check only. However, a common spamming
29147 ploy used to be to send syntactically invalid headers such as
29151 and this condition can be used to reject such messages, though they are not as
29152 common as they used to be.
29154 .vitem &*verify&~=&~helo*&
29155 .cindex "&%verify%& ACL condition"
29156 .cindex "&ACL;" "verifying HELO/EHLO"
29157 .cindex "HELO" "verifying"
29158 .cindex "EHLO" "verifying"
29159 .cindex "verifying" "EHLO"
29160 .cindex "verifying" "HELO"
29161 This condition is true if a HELO or EHLO command has been received from the
29162 client host, and its contents have been verified. If there has been no previous
29163 attempt to verify the HELO/EHLO contents, it is carried out when this
29164 condition is encountered. See the description of the &%helo_verify_hosts%& and
29165 &%helo_try_verify_hosts%& options for details of how to request verification
29166 independently of this condition.
29168 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
29169 option), this condition is always true.
29172 .vitem &*verify&~=&~not_blind*&
29173 .cindex "verifying" "not blind"
29174 .cindex "bcc recipients, verifying none"
29175 This condition checks that there are no blind (bcc) recipients in the message.
29176 Every envelope recipient must appear either in a &'To:'& header line or in a
29177 &'Cc:'& header line for this condition to be true. Local parts are checked
29178 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
29179 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
29180 used only in a DATA or non-SMTP ACL.
29182 There are, of course, many legitimate messages that make use of blind (bcc)
29183 recipients. This check should not be used on its own for blocking messages.
29186 .vitem &*verify&~=&~recipient/*&<&'options'&>
29187 .cindex "&%verify%& ACL condition"
29188 .cindex "&ACL;" "verifying recipient"
29189 .cindex "recipient" "verifying"
29190 .cindex "verifying" "recipient"
29191 .vindex "&$address_data$&"
29192 This condition is relevant only after a RCPT command. It verifies the current
29193 recipient. Details of address verification are given later, starting at section
29194 &<<SECTaddressverification>>&. After a recipient has been verified, the value
29195 of &$address_data$& is the last value that was set while routing the address.
29196 This applies even if the verification fails. When an address that is being
29197 verified is redirected to a single address, verification continues with the new
29198 address, and in that case, the subsequent value of &$address_data$& is the
29199 value for the child address.
29201 .vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
29202 .cindex "&%verify%& ACL condition"
29203 .cindex "&ACL;" "verifying host reverse lookup"
29204 .cindex "host" "verifying reverse lookup"
29205 This condition ensures that a verified host name has been looked up from the IP
29206 address of the client host. (This may have happened already if the host name
29207 was needed for checking a host list, or if the host matched &%host_lookup%&.)
29208 Verification ensures that the host name obtained from a reverse DNS lookup, or
29209 one of its aliases, does, when it is itself looked up in the DNS, yield the
29210 original IP address.
29212 There is one possible option, &`defer_ok`&. If this is present and a
29213 DNS operation returns a temporary error, the verify condition succeeds.
29215 If this condition is used for a locally generated message (that is, when there
29216 is no client host involved), it always succeeds.
29218 .vitem &*verify&~=&~sender/*&<&'options'&>
29219 .cindex "&%verify%& ACL condition"
29220 .cindex "&ACL;" "verifying sender"
29221 .cindex "sender" "verifying"
29222 .cindex "verifying" "sender"
29223 This condition is relevant only after a MAIL or RCPT command, or after a
29224 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
29225 the message's sender is empty (that is, this is a bounce message), the
29226 condition is true. Otherwise, the sender address is verified.
29228 .vindex "&$address_data$&"
29229 .vindex "&$sender_address_data$&"
29230 If there is data in the &$address_data$& variable at the end of routing, its
29231 value is placed in &$sender_address_data$& at the end of verification. This
29232 value can be used in subsequent conditions and modifiers in the same ACL
29233 statement. It does not persist after the end of the current statement. If you
29234 want to preserve the value for longer, you can save it in an ACL variable.
29236 Details of verification are given later, starting at section
29237 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
29238 to avoid doing it more than once per message.
29240 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
29241 .cindex "&%verify%& ACL condition"
29242 This is a variation of the previous option, in which a modified address is
29243 verified as a sender.
29248 .section "Using DNS lists" "SECTmorednslists"
29249 .cindex "DNS list" "in ACL"
29250 .cindex "black list (DNS)"
29251 .cindex "&ACL;" "testing a DNS list"
29252 In its simplest form, the &%dnslists%& condition tests whether the calling host
29253 is on at least one of a number of DNS lists by looking up the inverted IP
29254 address in one or more DNS domains. (Note that DNS list domains are not mail
29255 domains, so the &`+`& syntax for named lists doesn't work - it is used for
29256 special options instead.) For example, if the calling host's IP
29257 address is 192.168.62.43, and the ACL statement is
29259 deny dnslists = blackholes.mail-abuse.org : \
29260 dialups.mail-abuse.org
29262 the following records are looked up:
29264 43.62.168.192.blackholes.mail-abuse.org
29265 43.62.168.192.dialups.mail-abuse.org
29267 As soon as Exim finds an existing DNS record, processing of the list stops.
29268 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
29269 to test that a host is on more than one list (an &"and"& conjunction), you can
29270 use two separate conditions:
29272 deny dnslists = blackholes.mail-abuse.org
29273 dnslists = dialups.mail-abuse.org
29275 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
29276 behaves as if the host does not match the list item, that is, as if the DNS
29277 record does not exist. If there are further items in the DNS list, they are
29280 This is usually the required action when &%dnslists%& is used with &%deny%&
29281 (which is the most common usage), because it prevents a DNS failure from
29282 blocking mail. However, you can change this behaviour by putting one of the
29283 following special items in the list:
29285 &`+include_unknown `& behave as if the item is on the list
29286 &`+exclude_unknown `& behave as if the item is not on the list (default)
29287 &`+defer_unknown `& give a temporary error
29289 .cindex "&`+include_unknown`&"
29290 .cindex "&`+exclude_unknown`&"
29291 .cindex "&`+defer_unknown`&"
29292 Each of these applies to any subsequent items on the list. For example:
29294 deny dnslists = +defer_unknown : foo.bar.example
29296 Testing the list of domains stops as soon as a match is found. If you want to
29297 warn for one list and block for another, you can use two different statements:
29299 deny dnslists = blackholes.mail-abuse.org
29300 warn message = X-Warn: sending host is on dialups list
29301 dnslists = dialups.mail-abuse.org
29303 .cindex cacheing "of dns lookup"
29305 DNS list lookups are cached by Exim for the duration of the SMTP session
29307 (but limited by the DNS return TTL value),
29309 so a lookup based on the IP address is done at most once for any incoming
29310 connection (assuming long-enough TTL).
29311 Exim does not share information between multiple incoming
29312 connections (but your local name server cache should be active).
29316 .section "Specifying the IP address for a DNS list lookup" "SECID201"
29317 .cindex "DNS list" "keyed by explicit IP address"
29318 By default, the IP address that is used in a DNS list lookup is the IP address
29319 of the calling host. However, you can specify another IP address by listing it
29320 after the domain name, introduced by a slash. For example:
29322 deny dnslists = black.list.tld/192.168.1.2
29324 This feature is not very helpful with explicit IP addresses; it is intended for
29325 use with IP addresses that are looked up, for example, the IP addresses of the
29326 MX hosts or nameservers of an email sender address. For an example, see section
29327 &<<SECTmulkeyfor>>& below.
29332 .section "DNS lists keyed on domain names" "SECID202"
29333 .cindex "DNS list" "keyed by domain name"
29334 There are some lists that are keyed on domain names rather than inverted IP
29335 addresses (see for example the &'domain based zones'& link at
29336 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
29337 with these lists. You can change the name that is looked up in a DNS list by
29338 listing it after the domain name, introduced by a slash. For example,
29340 deny message = Sender's domain is listed at $dnslist_domain
29341 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
29343 This particular example is useful only in ACLs that are obeyed after the
29344 RCPT or DATA commands, when a sender address is available. If (for
29345 example) the message's sender is &'user@tld.example'& the name that is looked
29346 up by this example is
29348 tld.example.dsn.rfc-ignorant.org
29350 A single &%dnslists%& condition can contain entries for both names and IP
29351 addresses. For example:
29353 deny dnslists = sbl.spamhaus.org : \
29354 dsn.rfc-ignorant.org/$sender_address_domain
29356 The first item checks the sending host's IP address; the second checks a domain
29357 name. The whole condition is true if either of the DNS lookups succeeds.
29362 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
29363 .cindex "DNS list" "multiple keys for"
29364 The syntax described above for looking up explicitly-defined values (either
29365 names or IP addresses) in a DNS blacklist is a simplification. After the domain
29366 name for the DNS list, what follows the slash can in fact be a list of items.
29367 As with all lists in Exim, the default separator is a colon. However, because
29368 this is a sublist within the list of DNS blacklist domains, it is necessary
29369 either to double the separators like this:
29371 dnslists = black.list.tld/name.1::name.2
29373 or to change the separator character, like this:
29375 dnslists = black.list.tld/<;name.1;name.2
29377 If an item in the list is an IP address, it is inverted before the DNS
29378 blacklist domain is appended. If it is not an IP address, no inversion
29379 occurs. Consider this condition:
29381 dnslists = black.list.tld/<;192.168.1.2;a.domain
29383 The DNS lookups that occur are:
29385 2.1.168.192.black.list.tld
29386 a.domain.black.list.tld
29388 Once a DNS record has been found (that matches a specific IP return
29389 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
29390 are done. If there is a temporary DNS error, the rest of the sublist of domains
29391 or IP addresses is tried. A temporary error for the whole dnslists item occurs
29392 only if no other DNS lookup in this sublist succeeds. In other words, a
29393 successful lookup for any of the items in the sublist overrides a temporary
29394 error for a previous item.
29396 The ability to supply a list of items after the slash is in some sense just a
29397 syntactic convenience. These two examples have the same effect:
29399 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
29400 dnslists = black.list.tld/a.domain::b.domain
29402 However, when the data for the list is obtained from a lookup, the second form
29403 is usually much more convenient. Consider this example:
29405 deny message = The mail servers for the domain \
29406 $sender_address_domain \
29407 are listed at $dnslist_domain ($dnslist_value); \
29409 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
29410 ${lookup dnsdb {>|mxh=\
29411 $sender_address_domain} }} }
29413 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
29414 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
29415 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
29416 of expanding the condition might be something like this:
29418 dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|...
29420 Thus, this example checks whether or not the IP addresses of the sender
29421 domain's mail servers are on the Spamhaus black list.
29423 The key that was used for a successful DNS list lookup is put into the variable
29424 &$dnslist_matched$& (see section &<<SECID204>>&).
29429 .section "Data returned by DNS lists" "SECID203"
29430 .cindex "DNS list" "data returned from"
29431 DNS lists are constructed using address records in the DNS. The original RBL
29432 just used the address 127.0.0.1 on the right hand side of each record, but the
29433 RBL+ list and some other lists use a number of values with different meanings.
29434 The values used on the RBL+ list are:
29438 127.1.0.3 DUL and RBL
29440 127.1.0.5 RSS and RBL
29441 127.1.0.6 RSS and DUL
29442 127.1.0.7 RSS and DUL and RBL
29444 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
29445 different values. Some DNS lists may return more than one address record;
29446 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
29449 .section "Variables set from DNS lists" "SECID204"
29450 .cindex "expansion" "variables, set from DNS list"
29451 .cindex "DNS list" "variables set from"
29452 .vindex "&$dnslist_domain$&"
29453 .vindex "&$dnslist_matched$&"
29454 .vindex "&$dnslist_text$&"
29455 .vindex "&$dnslist_value$&"
29456 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
29457 the name of the overall domain that matched (for example,
29458 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
29459 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
29460 the DNS record. When the key is an IP address, it is not reversed in
29461 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
29462 cases, for example:
29464 deny dnslists = spamhaus.example
29466 the key is also available in another variable (in this case,
29467 &$sender_host_address$&). In more complicated cases, however, this is not true.
29468 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
29469 might generate a dnslists lookup like this:
29471 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
29473 If this condition succeeds, the value in &$dnslist_matched$& might be
29474 &`192.168.6.7`& (for example).
29476 If more than one address record is returned by the DNS lookup, all the IP
29477 addresses are included in &$dnslist_value$&, separated by commas and spaces.
29478 The variable &$dnslist_text$& contains the contents of any associated TXT
29479 record. For lists such as RBL+ the TXT record for a merged entry is often not
29480 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
29483 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
29484 &-- although these appear before the condition in the ACL, they are not
29485 expanded until after it has failed. For example:
29487 deny hosts = !+local_networks
29488 message = $sender_host_address is listed \
29490 dnslists = rbl-plus.mail-abuse.example
29495 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
29496 .cindex "DNS list" "matching specific returned data"
29497 You can add an equals sign and an IP address after a &%dnslists%& domain name
29498 in order to restrict its action to DNS records with a matching right hand side.
29501 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
29503 rejects only those hosts that yield 127.0.0.2. Without this additional data,
29504 any address record is considered to be a match. For the moment, we assume
29505 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
29506 describes how multiple records are handled.
29508 More than one IP address may be given for checking, using a comma as a
29509 separator. These are alternatives &-- if any one of them matches, the
29510 &%dnslists%& condition is true. For example:
29512 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
29514 If you want to specify a constraining address list and also specify names or IP
29515 addresses to be looked up, the constraining address list must be specified
29516 first. For example:
29518 deny dnslists = dsn.rfc-ignorant.org\
29519 =127.0.0.2/$sender_address_domain
29522 If the character &`&&`& is used instead of &`=`&, the comparison for each
29523 listed IP address is done by a bitwise &"and"& instead of by an equality test.
29524 In other words, the listed addresses are used as bit masks. The comparison is
29525 true if all the bits in the mask are present in the address that is being
29526 tested. For example:
29528 dnslists = a.b.c&0.0.0.3
29530 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
29531 want to test whether one bit or another bit is present (as opposed to both
29532 being present), you must use multiple values. For example:
29534 dnslists = a.b.c&0.0.0.1,0.0.0.2
29536 matches if the final component of the address is an odd number or two times
29541 .section "Negated DNS matching conditions" "SECID205"
29542 You can supply a negative list of IP addresses as part of a &%dnslists%&
29545 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
29547 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
29548 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
29550 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
29552 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
29553 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
29554 words, the result of the test is inverted if an exclamation mark appears before
29555 the &`=`& (or the &`&&`&) sign.
29557 &*Note*&: This kind of negation is not the same as negation in a domain,
29558 host, or address list (which is why the syntax is different).
29560 If you are using just one list, the negation syntax does not gain you much. The
29561 previous example is precisely equivalent to
29563 deny dnslists = a.b.c
29564 !dnslists = a.b.c=127.0.0.2,127.0.0.3
29566 However, if you are using multiple lists, the negation syntax is clearer.
29567 Consider this example:
29569 deny dnslists = sbl.spamhaus.org : \
29571 dnsbl.njabl.org!=127.0.0.3 : \
29574 Using only positive lists, this would have to be:
29576 deny dnslists = sbl.spamhaus.org : \
29578 deny dnslists = dnsbl.njabl.org
29579 !dnslists = dnsbl.njabl.org=127.0.0.3
29580 deny dnslists = relays.ordb.org
29582 which is less clear, and harder to maintain.
29587 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
29588 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
29589 thereby providing more than one IP address. When an item in a &%dnslists%& list
29590 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
29591 the match to specific results from the DNS lookup, there are two ways in which
29592 the checking can be handled. For example, consider the condition:
29594 dnslists = a.b.c=127.0.0.1
29596 What happens if the DNS lookup for the incoming IP address yields both
29597 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
29598 condition true because at least one given value was found, or is it false
29599 because at least one of the found values was not listed? And how does this
29600 affect negated conditions? Both possibilities are provided for with the help of
29601 additional separators &`==`& and &`=&&`&.
29604 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
29605 IP addresses matches one of the listed addresses. For the example above, the
29606 condition is true because 127.0.0.1 matches.
29608 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
29609 looked up IP addresses matches one of the listed addresses. If the condition is
29612 dnslists = a.b.c==127.0.0.1
29614 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
29615 false because 127.0.0.2 is not listed. You would need to have:
29617 dnslists = a.b.c==127.0.0.1,127.0.0.2
29619 for the condition to be true.
29622 When &`!`& is used to negate IP address matching, it inverts the result, giving
29623 the precise opposite of the behaviour above. Thus:
29625 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
29626 addresses matches one of the listed addresses. Consider:
29628 dnslists = a.b.c!&0.0.0.1
29630 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
29631 false because 127.0.0.1 matches.
29633 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
29634 looked up IP address that does not match. Consider:
29636 dnslists = a.b.c!=&0.0.0.1
29638 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
29639 true, because 127.0.0.2 does not match. You would need to have:
29641 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
29643 for the condition to be false.
29645 When the DNS lookup yields only a single IP address, there is no difference
29646 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
29651 .section "Detailed information from merged DNS lists" "SECTmordetinf"
29652 .cindex "DNS list" "information from merged"
29653 When the facility for restricting the matching IP values in a DNS list is used,
29654 the text from the TXT record that is set in &$dnslist_text$& may not reflect
29655 the true reason for rejection. This happens when lists are merged and the IP
29656 address in the A record is used to distinguish them; unfortunately there is
29657 only one TXT record. One way round this is not to use merged lists, but that
29658 can be inefficient because it requires multiple DNS lookups where one would do
29659 in the vast majority of cases when the host of interest is not on any of the
29662 A less inefficient way of solving this problem is available. If
29663 two domain names, comma-separated, are given, the second is used first to
29664 do an initial check, making use of any IP value restrictions that are set.
29665 If there is a match, the first domain is used, without any IP value
29666 restrictions, to get the TXT record. As a byproduct of this, there is also
29667 a check that the IP being tested is indeed on the first list. The first
29668 domain is the one that is put in &$dnslist_domain$&. For example:
29671 rejected because $sender_host_address is blacklisted \
29672 at $dnslist_domain\n$dnslist_text
29674 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
29675 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
29677 For the first blacklist item, this starts by doing a lookup in
29678 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
29679 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
29680 value, and as long as something is found, it looks for the corresponding TXT
29681 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
29682 The second blacklist item is processed similarly.
29684 If you are interested in more than one merged list, the same list must be
29685 given several times, but because the results of the DNS lookups are cached,
29686 the DNS calls themselves are not repeated. For example:
29688 reject dnslists = \
29689 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
29690 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
29691 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
29692 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
29694 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
29695 values matches (or if no record is found), this is the only lookup that is
29696 done. Only if there is a match is one of the more specific lists consulted.
29700 .section "DNS lists and IPv6" "SECTmorednslistslast"
29701 .cindex "IPv6" "DNS black lists"
29702 .cindex "DNS list" "IPv6 usage"
29703 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
29704 nibble by nibble. For example, if the calling host's IP address is
29705 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
29707 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
29708 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
29710 (split over two lines here to fit on the page). Unfortunately, some of the DNS
29711 lists contain wildcard records, intended for IPv4, that interact badly with
29712 IPv6. For example, the DNS entry
29714 *.3.some.list.example. A 127.0.0.1
29716 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
29717 Unfortunately, it also matches the entire 3::/4 IPv6 network.
29719 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
29720 &%condition%& condition, as in this example:
29722 deny condition = ${if isip4{$sender_host_address}}
29723 dnslists = some.list.example
29726 If an explicit key is being used for a DNS lookup and it may be an IPv6
29727 address you should specify alternate list separators for both the outer
29728 (DNS list name) list and inner (lookup keys) list:
29730 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
29733 .section "Rate limiting incoming messages" "SECTratelimiting"
29734 .cindex "rate limiting" "client sending"
29735 .cindex "limiting client sending rates"
29736 .oindex "&%smtp_ratelimit_*%&"
29737 The &%ratelimit%& ACL condition can be used to measure and control the rate at
29738 which clients can send email. This is more powerful than the
29739 &%smtp_ratelimit_*%& options, because those options control the rate of
29740 commands in a single SMTP session only, whereas the &%ratelimit%& condition
29741 works across all connections (concurrent and sequential) from the same client
29742 host. The syntax of the &%ratelimit%& condition is:
29744 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
29746 If the average client sending rate is less than &'m'& messages per time
29747 period &'p'& then the condition is false; otherwise it is true.
29749 As a side-effect, the &%ratelimit%& condition sets the expansion variable
29750 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
29751 configured value of &'m'&, and &$sender_rate_period$& to the configured value
29754 The parameter &'p'& is the smoothing time constant, in the form of an Exim
29755 time interval, for example, &`8h`& for eight hours. A larger time constant
29756 means that it takes Exim longer to forget a client's past behaviour. The
29757 parameter &'m'& is the maximum number of messages that a client is permitted to
29758 send in each time interval. It also specifies the number of messages permitted
29759 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
29760 constant, you can allow a client to send more messages in a burst without
29761 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
29762 both small, messages must be sent at an even rate.
29764 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
29765 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
29766 when deploying the &%ratelimit%& ACL condition. The script prints usage
29767 instructions when it is run with no arguments.
29769 The key is used to look up the data for calculating the client's average
29770 sending rate. This data is stored in Exim's spool directory, alongside the
29771 retry and other hints databases. The default key is &$sender_host_address$&,
29772 which means Exim computes the sending rate of each client host IP address.
29773 By changing the key you can change how Exim identifies clients for the purpose
29774 of ratelimiting. For example, to limit the sending rate of each authenticated
29775 user, independent of the computer they are sending from, set the key to
29776 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
29777 example, &$authenticated_id$& is only meaningful if the client has
29778 authenticated (which you can check with the &%authenticated%& ACL condition).
29780 The lookup key does not have to identify clients: If you want to limit the
29781 rate at which a recipient receives messages, you can use the key
29782 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
29785 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
29786 specifies what Exim measures the rate of, for example messages or recipients
29787 or bytes. You can adjust the measurement using the &%unique=%& and/or
29788 &%count=%& options. You can also control when Exim updates the recorded rate
29789 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
29790 separated by a slash, like the other parameters. They may appear in any order.
29792 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
29793 any options that alter the meaning of the stored data. The limit &'m'& is not
29794 stored, so you can alter the configured maximum rate and Exim will still
29795 remember clients' past behaviour. If you change the &%per_*%& mode or add or
29796 remove the &%unique=%& option, the lookup key changes so Exim will forget past
29797 behaviour. The lookup key is not affected by changes to the update mode and
29798 the &%count=%& option.
29801 .section "Ratelimit options for what is being measured" "ratoptmea"
29802 .cindex "rate limiting" "per_* options"
29803 The &%per_conn%& option limits the client's connection rate. It is not
29804 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
29805 &%acl_not_smtp_start%& ACLs.
29807 The &%per_mail%& option limits the client's rate of sending messages. This is
29808 the default if none of the &%per_*%& options is specified. It can be used in
29809 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
29810 &%acl_smtp_data%&, or &%acl_not_smtp%&.
29812 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
29813 the same ACLs as the &%per_mail%& option, though it is best to use this option
29814 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
29815 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
29816 in its MAIL command, which may be inaccurate or completely missing. You can
29817 follow the limit &'m'& in the configuration with K, M, or G to specify limits
29818 in kilobytes, megabytes, or gigabytes, respectively.
29820 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
29821 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
29822 &%acl_smtp_mime%&, &%acl_smtp_data%&, or &%acl_smtp_rcpt%& ACLs. In
29823 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
29824 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
29825 in either case the rate limiting engine will see a message with many
29826 recipients as a large high-speed burst.
29828 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
29829 number of different recipients that the client has sent messages to in the
29830 last time period. That is, if the client repeatedly sends messages to the same
29831 recipient, its measured rate is not increased. This option can only be used in
29834 The &%per_cmd%& option causes Exim to recompute the rate every time the
29835 condition is processed. This can be used to limit the rate of any SMTP
29836 command. If it is used in multiple ACLs it can limit the aggregate rate of
29837 multiple different commands.
29839 The &%count=%& option can be used to alter how much Exim adds to the client's
29840 measured rate. For example, the &%per_byte%& option is equivalent to
29841 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
29842 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
29843 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
29845 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
29848 .section "Ratelimit update modes" "ratoptupd"
29849 .cindex "rate limiting" "reading data without updating"
29850 You can specify one of three options with the &%ratelimit%& condition to
29851 control when its database is updated. This section describes the &%readonly%&
29852 mode, and the next section describes the &%strict%& and &%leaky%& modes.
29854 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
29855 previously-computed rate to check against the limit.
29857 For example, you can test the client's sending rate and deny it access (when
29858 it is too fast) in the connect ACL. If the client passes this check then it
29859 can go on to send a message, in which case its recorded rate will be updated
29860 in the MAIL ACL. Subsequent connections from the same client will check this
29864 deny ratelimit = 100 / 5m / readonly
29865 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
29866 (max $sender_rate_limit)
29869 warn ratelimit = 100 / 5m / strict
29870 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
29871 (max $sender_rate_limit)
29874 If Exim encounters multiple &%ratelimit%& conditions with the same key when
29875 processing a message then it may increase the client's measured rate more than
29876 it should. For example, this will happen if you check the &%per_rcpt%& option
29877 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
29878 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
29879 multiple update problems by using the &%readonly%& option on later ratelimit
29882 The &%per_*%& options described above do not make sense in some ACLs. If you
29883 use a &%per_*%& option in an ACL where it is not normally permitted then the
29884 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
29885 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
29886 next section) so you must specify the &%readonly%& option explicitly.
29889 .section "Ratelimit options for handling fast clients" "ratoptfast"
29890 .cindex "rate limiting" "strict and leaky modes"
29891 If a client's average rate is greater than the maximum, the rate limiting
29892 engine can react in two possible ways, depending on the presence of the
29893 &%strict%& or &%leaky%& update modes. This is independent of the other
29894 counter-measures (such as rejecting the message) that may be specified by the
29897 The &%leaky%& (default) option means that the client's recorded rate is not
29898 updated if it is above the limit. The effect of this is that Exim measures the
29899 client's average rate of successfully sent email, which cannot be greater than
29900 the maximum allowed. If the client is over the limit it may suffer some
29901 counter-measures (as specified in the ACL), but it will still be able to send
29902 email at the configured maximum rate, whatever the rate of its attempts. This
29903 is generally the better choice if you have clients that retry automatically.
29904 For example, it does not prevent a sender with an over-aggressive retry rate
29905 from getting any email through.
29907 The &%strict%& option means that the client's recorded rate is always
29908 updated. The effect of this is that Exim measures the client's average rate
29909 of attempts to send email, which can be much higher than the maximum it is
29910 actually allowed. If the client is over the limit it may be subjected to
29911 counter-measures by the ACL. It must slow down and allow sufficient time to
29912 pass that its computed rate falls below the maximum before it can send email
29913 again. The time (the number of smoothing periods) it must wait and not
29914 attempt to send mail can be calculated with this formula:
29916 ln(peakrate/maxrate)
29920 .section "Limiting the rate of different events" "ratoptuniq"
29921 .cindex "rate limiting" "counting unique events"
29922 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
29923 rate of different events. For example, the &%per_addr%& option uses this
29924 mechanism to count the number of different recipients that the client has
29925 sent messages to in the last time period; it is equivalent to
29926 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
29927 measure the rate that a client uses different sender addresses with the
29928 options &`per_mail/unique=$sender_address`&.
29930 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
29931 has seen for that key. The whole set is thrown away when it is older than the
29932 rate smoothing period &'p'&, so each different event is counted at most once
29933 per period. In the &%leaky%& update mode, an event that causes the client to
29934 go over the limit is not added to the set, in the same way that the client's
29935 recorded rate is not updated in the same situation.
29937 When you combine the &%unique=%& and &%readonly%& options, the specific
29938 &%unique=%& value is ignored, and Exim just retrieves the client's stored
29941 The &%unique=%& mechanism needs more space in the ratelimit database than the
29942 other &%ratelimit%& options in order to store the event set. The number of
29943 unique values is potentially as large as the rate limit, so the extra space
29944 required increases with larger limits.
29946 The uniqueification is not perfect: there is a small probability that Exim
29947 will think a new event has happened before. If the sender's rate is less than
29948 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
29949 the measured rate can go above the limit, in which case Exim may under-count
29950 events by a significant margin. Fortunately, if the rate is high enough (2.7
29951 times the limit) that the false positive rate goes above 9%, then Exim will
29952 throw away the over-full event set before the measured rate falls below the
29953 limit. Therefore the only harm should be that exceptionally high sending rates
29954 are logged incorrectly; any countermeasures you configure will be as effective
29958 .section "Using rate limiting" "useratlim"
29959 Exim's other ACL facilities are used to define what counter-measures are taken
29960 when the rate limit is exceeded. This might be anything from logging a warning
29961 (for example, while measuring existing sending rates in order to define
29962 policy), through time delays to slow down fast senders, up to rejecting the
29963 message. For example:
29965 # Log all senders' rates
29966 warn ratelimit = 0 / 1h / strict
29967 log_message = Sender rate $sender_rate / $sender_rate_period
29969 # Slow down fast senders; note the need to truncate $sender_rate
29970 # at the decimal point.
29971 warn ratelimit = 100 / 1h / per_rcpt / strict
29972 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
29973 $sender_rate_limit }s
29975 # Keep authenticated users under control
29976 deny authenticated = *
29977 ratelimit = 100 / 1d / strict / $authenticated_id
29979 # System-wide rate limit
29980 defer message = Sorry, too busy. Try again later.
29981 ratelimit = 10 / 1s / $primary_hostname
29983 # Restrict incoming rate from each host, with a default
29984 # set using a macro and special cases looked up in a table.
29985 defer message = Sender rate exceeds $sender_rate_limit \
29986 messages per $sender_rate_period
29987 ratelimit = ${lookup {$sender_host_address} \
29988 cdb {DB/ratelimits.cdb} \
29989 {$value} {RATELIMIT} }
29991 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
29992 especially with the &%per_rcpt%& option, you may suffer from a performance
29993 bottleneck caused by locking on the ratelimit hints database. Apart from
29994 making your ACLs less complicated, you can reduce the problem by using a
29995 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
29996 this means that Exim will lose its hints data after a reboot (including retry
29997 hints, the callout cache, and ratelimit data).
30001 .section "Address verification" "SECTaddressverification"
30002 .cindex "verifying address" "options for"
30003 .cindex "policy control" "address verification"
30004 Several of the &%verify%& conditions described in section
30005 &<<SECTaclconditions>>& cause addresses to be verified. Section
30006 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
30007 The verification conditions can be followed by options that modify the
30008 verification process. The options are separated from the keyword and from each
30009 other by slashes, and some of them contain parameters. For example:
30011 verify = sender/callout
30012 verify = recipient/defer_ok/callout=10s,defer_ok
30014 The first stage of address verification, which always happens, is to run the
30015 address through the routers, in &"verify mode"&. Routers can detect the
30016 difference between verification and routing for delivery, and their actions can
30017 be varied by a number of generic options such as &%verify%& and &%verify_only%&
30018 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
30019 The available options are as follows:
30022 If the &%callout%& option is specified, successful routing to one or more
30023 remote hosts is followed by a &"callout"& to those hosts as an additional
30024 check. Callouts and their sub-options are discussed in the next section.
30026 If there is a defer error while doing verification routing, the ACL
30027 normally returns &"defer"&. However, if you include &%defer_ok%& in the
30028 options, the condition is forced to be true instead. Note that this is a main
30029 verification option as well as a suboption for callouts.
30031 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
30032 discusses the reporting of sender address verification failures.
30034 The &%success_on_redirect%& option causes verification always to succeed
30035 immediately after a successful redirection. By default, if a redirection
30036 generates just one address, that address is also verified. See further
30037 discussion in section &<<SECTredirwhilveri>>&.
30040 .cindex "verifying address" "differentiating failures"
30041 .vindex "&$recipient_verify_failure$&"
30042 .vindex "&$sender_verify_failure$&"
30043 .vindex "&$acl_verify_message$&"
30044 After an address verification failure, &$acl_verify_message$& contains the
30045 error message that is associated with the failure. It can be preserved by
30048 warn !verify = sender
30049 set acl_m0 = $acl_verify_message
30051 If you are writing your own custom rejection message or log message when
30052 denying access, you can use this variable to include information about the
30053 verification failure.
30055 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
30056 appropriate) contains one of the following words:
30059 &%qualify%&: The address was unqualified (no domain), and the message
30060 was neither local nor came from an exempted host.
30062 &%route%&: Routing failed.
30064 &%mail%&: Routing succeeded, and a callout was attempted; rejection
30065 occurred at or before the MAIL command (that is, on initial
30066 connection, HELO, or MAIL).
30068 &%recipient%&: The RCPT command in a callout was rejected.
30070 &%postmaster%&: The postmaster check in a callout was rejected.
30073 The main use of these variables is expected to be to distinguish between
30074 rejections of MAIL and rejections of RCPT in callouts.
30079 .section "Callout verification" "SECTcallver"
30080 .cindex "verifying address" "by callout"
30081 .cindex "callout" "verification"
30082 .cindex "SMTP" "callout verification"
30083 For non-local addresses, routing verifies the domain, but is unable to do any
30084 checking of the local part. There are situations where some means of verifying
30085 the local part is desirable. One way this can be done is to make an SMTP
30086 &'callback'& to a delivery host for the sender address or a &'callforward'& to
30087 a subsequent host for a recipient address, to see if the host accepts the
30088 address. We use the term &'callout'& to cover both cases. Note that for a
30089 sender address, the callback is not to the client host that is trying to
30090 deliver the message, but to one of the hosts that accepts incoming mail for the
30093 Exim does not do callouts by default. If you want them to happen, you must
30094 request them by setting appropriate options on the &%verify%& condition, as
30095 described below. This facility should be used with care, because it can add a
30096 lot of resource usage to the cost of verifying an address. However, Exim does
30097 cache the results of callouts, which helps to reduce the cost. Details of
30098 caching are in section &<<SECTcallvercache>>&.
30100 Recipient callouts are usually used only between hosts that are controlled by
30101 the same administration. For example, a corporate gateway host could use
30102 callouts to check for valid recipients on an internal mailserver. A successful
30103 callout does not guarantee that a real delivery to the address would succeed;
30104 on the other hand, a failing callout does guarantee that a delivery would fail.
30106 If the &%callout%& option is present on a condition that verifies an address, a
30107 second stage of verification occurs if the address is successfully routed to
30108 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
30109 &(manualroute)& router, where the router specifies the hosts. However, if a
30110 router that does not set up hosts routes to an &(smtp)& transport with a
30111 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
30112 &%hosts_override%& set, its hosts are always used, whether or not the router
30113 supplies a host list.
30114 Callouts are only supported on &(smtp)& transports.
30116 The port that is used is taken from the transport, if it is specified and is a
30117 remote transport. (For routers that do verification only, no transport need be
30118 specified.) Otherwise, the default SMTP port is used. If a remote transport
30119 specifies an outgoing interface, this is used; otherwise the interface is not
30120 specified. Likewise, the text that is used for the HELO command is taken from
30121 the transport's &%helo_data%& option; if there is no transport, the value of
30122 &$smtp_active_hostname$& is used.
30124 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
30125 test whether a bounce message could be delivered to the sender address. The
30126 following SMTP commands are sent:
30128 &`HELO `&<&'local host name'&>
30130 &`RCPT TO:`&<&'the address to be tested'&>
30133 LHLO is used instead of HELO if the transport's &%protocol%& option is
30136 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
30139 A recipient callout check is similar. By default, it also uses an empty address
30140 for the sender. This default is chosen because most hosts do not make use of
30141 the sender address when verifying a recipient. Using the same address means
30142 that a single cache entry can be used for each recipient. Some sites, however,
30143 do make use of the sender address when verifying. These are catered for by the
30144 &%use_sender%& and &%use_postmaster%& options, described in the next section.
30146 If the response to the RCPT command is a 2&'xx'& code, the verification
30147 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
30148 Exim tries the next host, if any. If there is a problem with all the remote
30149 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
30150 &%callout%& option is given, in which case the condition is forced to succeed.
30152 .cindex "SMTP" "output flushing, disabling for callout"
30153 A callout may take a little time. For this reason, Exim normally flushes SMTP
30154 output before performing a callout in an ACL, to avoid unexpected timeouts in
30155 clients when the SMTP PIPELINING extension is in use. The flushing can be
30156 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
30161 .section "Additional parameters for callouts" "CALLaddparcall"
30162 .cindex "callout" "additional parameters for"
30163 The &%callout%& option can be followed by an equals sign and a number of
30164 optional parameters, separated by commas. For example:
30166 verify = recipient/callout=10s,defer_ok
30168 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
30169 separate verify options, is retained for backwards compatibility, but is now
30170 deprecated. The additional parameters for &%callout%& are as follows:
30174 .vitem <&'a&~time&~interval'&>
30175 .cindex "callout" "timeout, specifying"
30176 This specifies the timeout that applies for the callout attempt to each host.
30179 verify = sender/callout=5s
30181 The default is 30 seconds. The timeout is used for each response from the
30182 remote host. It is also used for the initial connection, unless overridden by
30183 the &%connect%& parameter.
30186 .vitem &*connect&~=&~*&<&'time&~interval'&>
30187 .cindex "callout" "connection timeout, specifying"
30188 This parameter makes it possible to set a different (usually smaller) timeout
30189 for making the SMTP connection. For example:
30191 verify = sender/callout=5s,connect=1s
30193 If not specified, this timeout defaults to the general timeout value.
30195 .vitem &*defer_ok*&
30196 .cindex "callout" "defer, action on"
30197 When this parameter is present, failure to contact any host, or any other kind
30198 of temporary error, is treated as success by the ACL. However, the cache is not
30199 updated in this circumstance.
30201 .vitem &*fullpostmaster*&
30202 .cindex "callout" "full postmaster check"
30203 This operates like the &%postmaster%& option (see below), but if the check for
30204 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
30205 accordance with the specification in RFC 2821. The RFC states that the
30206 unqualified address &'postmaster'& should be accepted.
30209 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
30210 .cindex "callout" "sender when verifying header"
30211 When verifying addresses in header lines using the &%header_sender%&
30212 verification option, Exim behaves by default as if the addresses are envelope
30213 sender addresses from a message. Callout verification therefore tests to see
30214 whether a bounce message could be delivered, by using an empty address in the
30215 MAIL command. However, it is arguable that these addresses might never be used
30216 as envelope senders, and could therefore justifiably reject bounce messages
30217 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
30218 address to use in the MAIL command. For example:
30220 require verify = header_sender/callout=mailfrom=abcd@x.y.z
30222 This parameter is available only for the &%header_sender%& verification option.
30225 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
30226 .cindex "callout" "overall timeout, specifying"
30227 This parameter sets an overall timeout for performing a callout verification.
30230 verify = sender/callout=5s,maxwait=30s
30232 This timeout defaults to four times the callout timeout for individual SMTP
30233 commands. The overall timeout applies when there is more than one host that can
30234 be tried. The timeout is checked before trying the next host. This prevents
30235 very long delays if there are a large number of hosts and all are timing out
30236 (for example, when network connections are timing out).
30239 .vitem &*no_cache*&
30240 .cindex "callout" "cache, suppressing"
30241 .cindex "caching callout, suppressing"
30242 When this parameter is given, the callout cache is neither read nor updated.
30244 .vitem &*postmaster*&
30245 .cindex "callout" "postmaster; checking"
30246 When this parameter is set, a successful callout check is followed by a similar
30247 check for the local part &'postmaster'& at the same domain. If this address is
30248 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
30249 the postmaster check is recorded in a cache record; if it is a failure, this is
30250 used to fail subsequent callouts for the domain without a connection being
30251 made, until the cache record expires.
30253 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
30254 The postmaster check uses an empty sender in the MAIL command by default.
30255 You can use this parameter to do a postmaster check using a different address.
30258 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
30260 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
30261 one overrides. The &%postmaster%& parameter is equivalent to this example:
30263 require verify = sender/callout=postmaster_mailfrom=
30265 &*Warning*&: The caching arrangements for postmaster checking do not take
30266 account of the sender address. It is assumed that either the empty address or
30267 a fixed non-empty address will be used. All that Exim remembers is that the
30268 postmaster check for the domain succeeded or failed.
30272 .cindex "callout" "&""random""& check"
30273 When this parameter is set, before doing the normal callout check, Exim does a
30274 check for a &"random"& local part at the same domain. The local part is not
30275 really random &-- it is defined by the expansion of the option
30276 &%callout_random_local_part%&, which defaults to
30278 $primary_hostname-$tod_epoch-testing
30280 The idea here is to try to determine whether the remote host accepts all local
30281 parts without checking. If it does, there is no point in doing callouts for
30282 specific local parts. If the &"random"& check succeeds, the result is saved in
30283 a cache record, and used to force the current and subsequent callout checks to
30284 succeed without a connection being made, until the cache record expires.
30286 .vitem &*use_postmaster*&
30287 .cindex "callout" "sender for recipient check"
30288 This parameter applies to recipient callouts only. For example:
30290 deny !verify = recipient/callout=use_postmaster
30292 .vindex "&$qualify_domain$&"
30293 It causes a non-empty postmaster address to be used in the MAIL command when
30294 performing the callout for the recipient, and also for a &"random"& check if
30295 that is configured. The local part of the address is &`postmaster`& and the
30296 domain is the contents of &$qualify_domain$&.
30298 .vitem &*use_sender*&
30299 This option applies to recipient callouts only. For example:
30301 require verify = recipient/callout=use_sender
30303 It causes the message's actual sender address to be used in the MAIL
30304 command when performing the callout, instead of an empty address. There is no
30305 need to use this option unless you know that the called hosts make use of the
30306 sender when checking recipients. If used indiscriminately, it reduces the
30307 usefulness of callout caching.
30310 If you use any of the parameters that set a non-empty sender for the MAIL
30311 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
30312 &%use_sender%&), you should think about possible loops. Recipient checking is
30313 usually done between two hosts that are under the same management, and the host
30314 that receives the callouts is not normally configured to do callouts itself.
30315 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
30316 these circumstances.
30318 However, if you use a non-empty sender address for a callout to an arbitrary
30319 host, there is the likelihood that the remote host will itself initiate a
30320 callout check back to your host. As it is checking what appears to be a message
30321 sender, it is likely to use an empty address in MAIL, thus avoiding a
30322 callout loop. However, to be on the safe side it would be best to set up your
30323 own ACLs so that they do not do sender verification checks when the recipient
30324 is the address you use for header sender or postmaster callout checking.
30326 Another issue to think about when using non-empty senders for callouts is
30327 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
30328 by the sender/recipient combination; thus, for any given recipient, many more
30329 actual callouts are performed than when an empty sender or postmaster is used.
30334 .section "Callout caching" "SECTcallvercache"
30335 .cindex "hints database" "callout cache"
30336 .cindex "callout" "cache, description of"
30337 .cindex "caching" "callout"
30338 Exim caches the results of callouts in order to reduce the amount of resources
30339 used, unless you specify the &%no_cache%& parameter with the &%callout%&
30340 option. A hints database called &"callout"& is used for the cache. Two
30341 different record types are used: one records the result of a callout check for
30342 a specific address, and the other records information that applies to the
30343 entire domain (for example, that it accepts the local part &'postmaster'&).
30345 When an original callout fails, a detailed SMTP error message is given about
30346 the failure. However, for subsequent failures use the cache data, this message
30349 The expiry times for negative and positive address cache records are
30350 independent, and can be set by the global options &%callout_negative_expire%&
30351 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
30353 If a host gives a negative response to an SMTP connection, or rejects any
30354 commands up to and including
30358 (but not including the MAIL command with a non-empty address),
30359 any callout attempt is bound to fail. Exim remembers such failures in a
30360 domain cache record, which it uses to fail callouts for the domain without
30361 making new connections, until the domain record times out. There are two
30362 separate expiry times for domain cache records:
30363 &%callout_domain_negative_expire%& (default 3h) and
30364 &%callout_domain_positive_expire%& (default 7d).
30366 Domain records expire when the negative expiry time is reached if callouts
30367 cannot be made for the domain, or if the postmaster check failed.
30368 Otherwise, they expire when the positive expiry time is reached. This
30369 ensures that, for example, a host that stops accepting &"random"& local parts
30370 will eventually be noticed.
30372 The callout caching mechanism is based on the domain of the address that is
30373 being tested. If the domain routes to several hosts, it is assumed that their
30374 behaviour will be the same.
30378 .section "Sender address verification reporting" "SECTsenaddver"
30379 .cindex "verifying" "suppressing error details"
30380 See section &<<SECTaddressverification>>& for a general discussion of
30381 verification. When sender verification fails in an ACL, the details of the
30382 failure are given as additional output lines before the 550 response to the
30383 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
30386 MAIL FROM:<xyz@abc.example>
30388 RCPT TO:<pqr@def.example>
30389 550-Verification failed for <xyz@abc.example>
30390 550-Called: 192.168.34.43
30391 550-Sent: RCPT TO:<xyz@abc.example>
30392 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
30393 550 Sender verification failed
30395 If more than one RCPT command fails in the same way, the details are given
30396 only for the first of them. However, some administrators do not want to send
30397 out this much information. You can suppress the details by adding
30398 &`/no_details`& to the ACL statement that requests sender verification. For
30401 verify = sender/no_details
30404 .section "Redirection while verifying" "SECTredirwhilveri"
30405 .cindex "verifying" "redirection while"
30406 .cindex "address redirection" "while verifying"
30407 A dilemma arises when a local address is redirected by aliasing or forwarding
30408 during verification: should the generated addresses themselves be verified,
30409 or should the successful expansion of the original address be enough to verify
30410 it? By default, Exim takes the following pragmatic approach:
30413 When an incoming address is redirected to just one child address, verification
30414 continues with the child address, and if that fails to verify, the original
30415 verification also fails.
30417 When an incoming address is redirected to more than one child address,
30418 verification does not continue. A success result is returned.
30421 This seems the most reasonable behaviour for the common use of aliasing as a
30422 way of redirecting different local parts to the same mailbox. It means, for
30423 example, that a pair of alias entries of the form
30426 aw123: :fail: Gone away, no forwarding address
30428 work as expected, with both local parts causing verification failure. When a
30429 redirection generates more than one address, the behaviour is more like a
30430 mailing list, where the existence of the alias itself is sufficient for
30431 verification to succeed.
30433 It is possible, however, to change the default behaviour so that all successful
30434 redirections count as successful verifications, however many new addresses are
30435 generated. This is specified by the &%success_on_redirect%& verification
30436 option. For example:
30438 require verify = recipient/success_on_redirect/callout=10s
30440 In this example, verification succeeds if a router generates a new address, and
30441 the callout does not occur, because no address was routed to a remote host.
30443 When verification is being tested via the &%-bv%& option, the treatment of
30444 redirections is as just described, unless the &%-v%& or any debugging option is
30445 also specified. In that case, full verification is done for every generated
30446 address and a report is output for each of them.
30450 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
30451 .cindex "CSA" "verifying"
30452 Client SMTP Authorization is a system that allows a site to advertise
30453 which machines are and are not permitted to send email. This is done by placing
30454 special SRV records in the DNS; these are looked up using the client's HELO
30455 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
30456 Authorization checks in Exim are performed by the ACL condition:
30460 This fails if the client is not authorized. If there is a DNS problem, or if no
30461 valid CSA SRV record is found, or if the client is authorized, the condition
30462 succeeds. These three cases can be distinguished using the expansion variable
30463 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
30464 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
30465 be likely to cause problems for legitimate email.
30467 The error messages produced by the CSA code include slightly more
30468 detail. If &$csa_status$& is &"defer"&, this may be because of problems
30469 looking up the CSA SRV record, or problems looking up the CSA target
30470 address record. There are four reasons for &$csa_status$& being &"fail"&:
30473 The client's host name is explicitly not authorized.
30475 The client's IP address does not match any of the CSA target IP addresses.
30477 The client's host name is authorized but it has no valid target IP addresses
30478 (for example, the target's addresses are IPv6 and the client is using IPv4).
30480 The client's host name has no CSA SRV record but a parent domain has asserted
30481 that all subdomains must be explicitly authorized.
30484 The &%csa%& verification condition can take an argument which is the domain to
30485 use for the DNS query. The default is:
30487 verify = csa/$sender_helo_name
30489 This implementation includes an extension to CSA. If the query domain
30490 is an address literal such as [192.0.2.95], or if it is a bare IP
30491 address, Exim searches for CSA SRV records in the reverse DNS as if
30492 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
30495 verify = csa/$sender_host_address
30497 In fact, this is the check that Exim performs if the client does not say HELO.
30498 This extension can be turned off by setting the main configuration option
30499 &%dns_csa_use_reverse%& to be false.
30501 If a CSA SRV record is not found for the domain itself, a search
30502 is performed through its parent domains for a record which might be
30503 making assertions about subdomains. The maximum depth of this search is limited
30504 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
30505 default. Exim does not look for CSA SRV records in a top level domain, so the
30506 default settings handle HELO domains as long as seven
30507 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
30508 of legitimate HELO domains.
30510 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
30511 direct SRV lookups, this is not sufficient because of the extra parent domain
30512 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
30513 addresses into lookups in the reverse DNS space. The result of a successful
30516 ${lookup dnsdb {csa=$sender_helo_name}}
30518 has two space-separated fields: an authorization code and a target host name.
30519 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
30520 authorization required but absent, or &"?"& for unknown.
30525 .section "Bounce address tag validation" "SECTverifyPRVS"
30526 .cindex "BATV, verifying"
30527 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
30528 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
30529 Genuine incoming bounce messages should therefore always be addressed to
30530 recipients that have a valid tag. This scheme is a way of detecting unwanted
30531 bounce messages caused by sender address forgeries (often called &"collateral
30532 spam"&), because the recipients of such messages do not include valid tags.
30534 There are two expansion items to help with the implementation of the BATV
30535 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
30536 the original envelope sender address by using a simple key to add a hash of the
30537 address and some time-based randomizing information. The &%prvs%& expansion
30538 item creates a signed address, and the &%prvscheck%& expansion item checks one.
30539 The syntax of these expansion items is described in section
30540 &<<SECTexpansionitems>>&.
30542 As an example, suppose the secret per-address keys are stored in an MySQL
30543 database. A query to look up the key for an address could be defined as a macro
30546 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
30547 WHERE sender='${quote_mysql:$prvscheck_address}'\
30550 Suppose also that the senders who make use of BATV are defined by an address
30551 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
30554 # Bounces: drop unsigned addresses for BATV senders
30555 deny message = This address does not send an unsigned reverse path
30557 recipients = +batv_senders
30559 # Bounces: In case of prvs-signed address, check signature.
30560 deny message = Invalid reverse path signature.
30562 condition = ${prvscheck {$local_part@$domain}\
30563 {PRVSCHECK_SQL}{1}}
30564 !condition = $prvscheck_result
30566 The first statement rejects recipients for bounce messages that are addressed
30567 to plain BATV sender addresses, because it is known that BATV senders do not
30568 send out messages with plain sender addresses. The second statement rejects
30569 recipients that are prvs-signed, but with invalid signatures (either because
30570 the key is wrong, or the signature has timed out).
30572 A non-prvs-signed address is not rejected by the second statement, because the
30573 &%prvscheck%& expansion yields an empty string if its first argument is not a
30574 prvs-signed address, thus causing the &%condition%& condition to be false. If
30575 the first argument is a syntactically valid prvs-signed address, the yield is
30576 the third string (in this case &"1"&), whether or not the cryptographic and
30577 timeout checks succeed. The &$prvscheck_result$& variable contains the result
30578 of the checks (empty for failure, &"1"& for success).
30580 There is one more issue you must consider when implementing prvs-signing:
30581 you have to ensure that the routers accept prvs-signed addresses and
30582 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
30583 router to remove the signature with a configuration along these lines:
30587 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
30589 This works because, if the third argument of &%prvscheck%& is empty, the result
30590 of the expansion of a prvs-signed address is the decoded value of the original
30591 address. This router should probably be the first of your routers that handles
30594 To create BATV-signed addresses in the first place, a transport of this form
30597 external_smtp_batv:
30599 return_path = ${prvs {$return_path} \
30600 {${lookup mysql{SELECT \
30601 secret FROM batv_prvs WHERE \
30602 sender='${quote_mysql:$sender_address}'} \
30605 If no key can be found for the existing return path, no signing takes place.
30609 .section "Using an ACL to control relaying" "SECTrelaycontrol"
30610 .cindex "&ACL;" "relay control"
30611 .cindex "relaying" "control by ACL"
30612 .cindex "policy control" "relay control"
30613 An MTA is said to &'relay'& a message if it receives it from some host and
30614 delivers it directly to another host as a result of a remote address contained
30615 within it. Redirecting a local address via an alias or forward file and then
30616 passing the message on to another host is not relaying,
30617 .cindex "&""percent hack""&"
30618 but a redirection as a result of the &"percent hack"& is.
30620 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
30621 A host which is acting as a gateway or an MX backup is concerned with incoming
30622 relaying from arbitrary hosts to a specific set of domains. On the other hand,
30623 a host which is acting as a smart host for a number of clients is concerned
30624 with outgoing relaying from those clients to the Internet at large. Often the
30625 same host is fulfilling both functions,
30627 . as illustrated in the diagram below,
30629 but in principle these two kinds of relaying are entirely independent. What is
30630 not wanted is the transmission of mail from arbitrary remote hosts through your
30631 system to arbitrary domains.
30634 You can implement relay control by means of suitable statements in the ACL that
30635 runs for each RCPT command. For convenience, it is often easiest to use
30636 Exim's named list facility to define the domains and hosts involved. For
30637 example, suppose you want to do the following:
30640 Deliver a number of domains to mailboxes on the local host (or process them
30641 locally in some other way). Let's say these are &'my.dom1.example'& and
30642 &'my.dom2.example'&.
30644 Relay mail for a number of other domains for which you are the secondary MX.
30645 These might be &'friend1.example'& and &'friend2.example'&.
30647 Relay mail from the hosts on your local LAN, to whatever domains are involved.
30648 Suppose your LAN is 192.168.45.0/24.
30652 In the main part of the configuration, you put the following definitions:
30654 domainlist local_domains = my.dom1.example : my.dom2.example
30655 domainlist relay_to_domains = friend1.example : friend2.example
30656 hostlist relay_from_hosts = 192.168.45.0/24
30658 Now you can use these definitions in the ACL that is run for every RCPT
30662 accept domains = +local_domains : +relay_to_domains
30663 accept hosts = +relay_from_hosts
30665 The first statement accepts any RCPT command that contains an address in
30666 the local or relay domains. For any other domain, control passes to the second
30667 statement, which accepts the command only if it comes from one of the relay
30668 hosts. In practice, you will probably want to make your ACL more sophisticated
30669 than this, for example, by including sender and recipient verification. The
30670 default configuration includes a more comprehensive example, which is described
30671 in chapter &<<CHAPdefconfil>>&.
30675 .section "Checking a relay configuration" "SECTcheralcon"
30676 .cindex "relaying" "checking control of"
30677 You can check the relay characteristics of your configuration in the same way
30678 that you can test any ACL behaviour for an incoming SMTP connection, by using
30679 the &%-bh%& option to run a fake SMTP session with which you interact.
30681 For specifically testing for unwanted relaying, the host
30682 &'relay-test.mail-abuse.org'& provides a useful service. If you telnet to this
30683 host from the host on which Exim is running, using the normal telnet port, you
30684 will see a normal telnet connection message and then quite a long delay. Be
30685 patient. The remote host is making an SMTP connection back to your host, and
30686 trying a number of common probes to test for open relay vulnerability. The
30687 results of the tests will eventually appear on your terminal.
30692 . ////////////////////////////////////////////////////////////////////////////
30693 . ////////////////////////////////////////////////////////////////////////////
30695 .chapter "Content scanning at ACL time" "CHAPexiscan"
30696 .scindex IIDcosca "content scanning" "at ACL time"
30697 The extension of Exim to include content scanning at ACL time, formerly known
30698 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
30699 was integrated into the main source for Exim release 4.50, and Tom continues to
30700 maintain it. Most of the wording of this chapter is taken from Tom's
30703 It is also possible to scan the content of messages at other times. The
30704 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
30705 scanning after all the ACLs have run. A transport filter can be used to scan
30706 messages at delivery time (see the &%transport_filter%& option, described in
30707 chapter &<<CHAPtransportgeneric>>&).
30709 If you want to include the ACL-time content-scanning features when you compile
30710 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
30711 &_Local/Makefile_&. When you do that, the Exim binary is built with:
30714 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
30715 for all MIME parts for SMTP and non-SMTP messages, respectively.
30717 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
30718 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
30719 run at the end of message reception (the &%acl_smtp_data%& ACL).
30721 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
30722 of messages, or parts of messages, for debugging purposes.
30724 Additional expansion variables that are set in the new ACL and by the new
30727 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
30730 There is another content-scanning configuration option for &_Local/Makefile_&,
30731 called WITH_OLD_DEMIME. If this is set, the old, deprecated &%demime%& ACL
30732 condition is compiled, in addition to all the other content-scanning features.
30734 Content-scanning is continually evolving, and new features are still being
30735 added. While such features are still unstable and liable to incompatible
30736 changes, they are made available in Exim by setting options whose names begin
30737 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
30738 this manual. You can find out about them by reading the file called
30739 &_doc/experimental.txt_&.
30741 All the content-scanning facilities work on a MBOX copy of the message that is
30742 temporarily created in a file called:
30744 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
30746 The &_.eml_& extension is a friendly hint to virus scanners that they can
30747 expect an MBOX-like structure inside that file. The file is created when the
30748 first content scanning facility is called. Subsequent calls to content
30749 scanning conditions open the same file again. The directory is recursively
30750 removed when the &%acl_smtp_data%& ACL has finished running, unless
30752 control = no_mbox_unspool
30754 has been encountered. When the MIME ACL decodes files, they are put into the
30755 same directory by default.
30759 .section "Scanning for viruses" "SECTscanvirus"
30760 .cindex "virus scanning"
30761 .cindex "content scanning" "for viruses"
30762 .cindex "content scanning" "the &%malware%& condition"
30763 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
30764 It supports a &"generic"& interface to scanners called via the shell, and
30765 specialized interfaces for &"daemon"& type virus scanners, which are resident
30766 in memory and thus are much faster.
30768 A timeout of 2 minutes is applied to a scanner call (by default);
30769 if it expires then a defer action is taken.
30771 .oindex "&%av_scanner%&"
30772 You can set the &%av_scanner%& option in the main part of the configuration
30773 to specify which scanner to use, together with any additional options that
30774 are needed. The basic syntax is as follows:
30776 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
30778 If you do not set &%av_scanner%&, it defaults to
30780 av_scanner = sophie:/var/run/sophie
30782 If the value of &%av_scanner%& starts with a dollar character, it is expanded
30784 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
30785 The following scanner types are supported in this release:
30789 .cindex "virus scanners" "avast"
30790 This is the scanner daemon of Avast. It has been tested with Avast Core
30791 Security (currently at version 1.1.7).
30792 You can get a trial version at &url(http://www.avast.com) or for Linux
30793 at &url(http://www.avast.com/linux-server-antivirus).
30794 This scanner type takes one option,
30795 which can be either a full path to a UNIX socket,
30796 or host and port specifiers separated by white space.
30797 The host may be a name or an IP address; the port is either a
30798 single number or a pair of numbers with a dash between.
30799 Any further options are given, on separate lines,
30800 to the daemon as options before the main scan command.
30803 av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
30804 av_scanner = avast:192.168.2.22 5036
30806 If you omit the argument, the default path
30807 &_/var/run/avast/scan.sock_&
30809 If you use a remote host,
30810 you need to make Exim's spool directory available to it,
30811 as the scanner is passed a file path, not file contents.
30812 For information about available commands and their options you may use
30814 $ socat UNIX:/var/run/avast/scan.sock STDIO:
30821 .vitem &%aveserver%&
30822 .cindex "virus scanners" "Kaspersky"
30823 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
30824 at &url(http://www.kaspersky.com). This scanner type takes one option,
30825 which is the path to the daemon's UNIX socket. The default is shown in this
30828 av_scanner = aveserver:/var/run/aveserver
30833 .cindex "virus scanners" "clamd"
30834 This daemon-type scanner is GPL and free. You can get it at
30835 &url(http://www.clamav.net/). Some older versions of clamd do not seem to
30836 unpack MIME containers, so it used to be recommended to unpack MIME attachments
30837 in the MIME ACL. This is no longer believed to be necessary.
30839 The options are a list of server specifiers, which may be
30840 a UNIX socket specification,
30841 a TCP socket specification,
30842 or a (global) option.
30844 A socket specification consists of a space-separated list.
30845 For a Unix socket the first element is a full path for the socket,
30846 for a TCP socket the first element is the IP address
30847 and the second a port number,
30848 Any further elements are per-server (non-global) options.
30849 These per-server options are supported:
30851 retry=<timespec> Retry on connect fail
30854 The &`retry`& option specifies a time after which a single retry for
30855 a failed connect is made. The default is to not retry.
30857 If a Unix socket file is specified, only one server is supported.
30861 av_scanner = clamd:/opt/clamd/socket
30862 av_scanner = clamd:192.0.2.3 1234
30863 av_scanner = clamd:192.0.2.3 1234:local
30864 av_scanner = clamd:192.0.2.3 1234 retry=10s
30865 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
30867 If the value of av_scanner points to a UNIX socket file or contains the
30869 option, then the ClamAV interface will pass a filename containing the data
30870 to be scanned, which will should normally result in less I/O happening and be
30871 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
30872 Exim does not assume that there is a common filesystem with the remote host.
30873 There is an option WITH_OLD_CLAMAV_STREAM in &_src/EDITME_& available, should
30874 you be running a version of ClamAV prior to 0.95.
30876 The final example shows that multiple TCP targets can be specified. Exim will
30877 randomly use one for each incoming email (i.e. it load balances them). Note
30878 that only TCP targets may be used if specifying a list of scanners; a UNIX
30879 socket cannot be mixed in with TCP targets. If one of the servers becomes
30880 unavailable, Exim will try the remaining one(s) until it finds one that works.
30881 When a clamd server becomes unreachable, Exim will log a message. Exim does
30882 not keep track of scanner state between multiple messages, and the scanner
30883 selection is random, so the message will get logged in the mainlog for each
30884 email that the down scanner gets chosen first (message wrapped to be readable):
30886 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
30887 clamd: connection to localhost, port 3310 failed
30888 (Connection refused)
30891 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
30892 contributing the code for this scanner.
30895 .cindex "virus scanners" "command line interface"
30896 This is the keyword for the generic command line scanner interface. It can be
30897 used to attach virus scanners that are invoked from the shell. This scanner
30898 type takes 3 mandatory options:
30901 The full path and name of the scanner binary, with all command line options,
30902 and a placeholder (&`%s`&) for the directory to scan.
30905 A regular expression to match against the STDOUT and STDERR output of the
30906 virus scanner. If the expression matches, a virus was found. You must make
30907 absolutely sure that this expression matches on &"virus found"&. This is called
30908 the &"trigger"& expression.
30911 Another regular expression, containing exactly one pair of parentheses, to
30912 match the name of the virus found in the scanners output. This is called the
30913 &"name"& expression.
30916 For example, Sophos Sweep reports a virus on a line like this:
30918 Virus 'W32/Magistr-B' found in file ./those.bat
30920 For the trigger expression, we can match the phrase &"found in file"&. For the
30921 name expression, we want to extract the W32/Magistr-B string, so we can match
30922 for the single quotes left and right of it. Altogether, this makes the
30923 configuration setting:
30925 av_scanner = cmdline:\
30926 /path/to/sweep -ss -all -rec -archive %s:\
30927 found in file:'(.+)'
30930 .cindex "virus scanners" "DrWeb"
30931 The DrWeb daemon scanner (&url(http://www.sald.com/)) interface
30933 either a full path to a UNIX socket,
30934 or host and port specifiers separated by white space.
30935 The host may be a name or an IP address; the port is either a
30936 single number or a pair of numbers with a dash between.
30939 av_scanner = drweb:/var/run/drwebd.sock
30940 av_scanner = drweb:192.168.2.20 31337
30942 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
30943 is used. Thanks to Alex Miller for contributing the code for this scanner.
30946 .cindex "virus scanners" "f-protd"
30947 The f-protd scanner is accessed via HTTP over TCP.
30948 One argument is taken, being a space-separated hostname and port number
30952 av_scanner = f-protd:localhost 10200-10204
30954 If you omit the argument, the default values show above are used.
30957 .cindex "virus scanners" "F-Secure"
30958 The F-Secure daemon scanner (&url(http://www.f-secure.com)) takes one
30959 argument which is the path to a UNIX socket. For example:
30961 av_scanner = fsecure:/path/to/.fsav
30963 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
30964 Thelmen for contributing the code for this scanner.
30966 .vitem &%kavdaemon%&
30967 .cindex "virus scanners" "Kaspersky"
30968 This is the scanner daemon of Kaspersky Version 4. This version of the
30969 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
30970 scanner type takes one option, which is the path to the daemon's UNIX socket.
30973 av_scanner = kavdaemon:/opt/AVP/AvpCtl
30975 The default path is &_/var/run/AvpCtl_&.
30978 .cindex "virus scanners" "mksd"
30979 This is a daemon type scanner that is aimed mainly at Polish users, though some
30980 parts of documentation are now available in English. You can get it at
30981 &url(http://linux.mks.com.pl/). The only option for this scanner type is
30982 the maximum number of processes used simultaneously to scan the attachments,
30983 provided that the demime facility is employed and also provided that mksd has
30984 been run with at least the same number of child processes. For example:
30986 av_scanner = mksd:2
30988 You can safely omit this option (the default value is 1).
30991 .cindex "virus scanners" "simple socket-connected"
30992 This is a general-purpose way of talking to simple scanner daemons
30993 running on the local machine.
30994 There are four options:
30995 an address (which may be an IP address and port, or the path of a Unix socket),
30996 a commandline to send (may include a single %s which will be replaced with
30997 the path to the mail file to be scanned),
30998 an RE to trigger on from the returned data,
30999 an RE to extract malware_name from the returned data.
31002 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)\$
31004 Default for the socket specifier is &_/tmp/malware.sock_&.
31005 Default for the commandline is &_%s\n_&.
31006 Both regular-expressions are required.
31009 .cindex "virus scanners" "Sophos and Sophie"
31010 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
31011 You can get Sophie at &url(http://www.clanfield.info/sophie/). The only option
31012 for this scanner type is the path to the UNIX socket that Sophie uses for
31013 client communication. For example:
31015 av_scanner = sophie:/tmp/sophie
31017 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
31021 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
31022 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
31025 The &%av_scanner%& option is expanded each time &%malware%& is called. This
31026 makes it possible to use different scanners. See further below for an example.
31027 The &%malware%& condition caches its results, so when you use it multiple times
31028 for the same message, the actual scanning process is only carried out once.
31029 However, using expandable items in &%av_scanner%& disables this caching, in
31030 which case each use of the &%malware%& condition causes a new scan of the
31033 The &%malware%& condition takes a right-hand argument that is expanded before
31034 use and taken as a list, slash-separated by default.
31035 The first element can then be one of
31038 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
31039 The condition succeeds if a virus was found, and fail otherwise. This is the
31042 &"false"& or &"0"& or an empty string, in which case no scanning is done and
31043 the condition fails immediately.
31045 A regular expression, in which case the message is scanned for viruses. The
31046 condition succeeds if a virus is found and its name matches the regular
31047 expression. This allows you to take special actions on certain types of virus.
31048 Note that &"/"& characters in the RE must be doubled due to the list-processing,
31049 unless the separator is changed (in the usual way).
31052 You can append a &`defer_ok`& element to the &%malware%& argument list to accept
31053 messages even if there is a problem with the virus scanner.
31054 Otherwise, such a problem causes the ACL to defer.
31056 You can append a &`tmo=<val>`& element to the &%malware%& argument list to
31057 specify a non-default timeout. The default is two minutes.
31060 malware = * / defer_ok / tmo=10s
31062 A timeout causes the ACL to defer.
31064 .vindex "&$callout_address$&"
31065 When a connection is made to the scanner the expansion variable &$callout_address$&
31066 is set to record the actual address used.
31068 .vindex "&$malware_name$&"
31069 When a virus is found, the condition sets up an expansion variable called
31070 &$malware_name$& that contains the name of the virus. You can use it in a
31071 &%message%& modifier that specifies the error returned to the sender, and/or in
31074 If your virus scanner cannot unpack MIME and TNEF containers itself, you should
31075 use the &%demime%& condition (see section &<<SECTdemimecond>>&) before the
31076 &%malware%& condition.
31078 Beware the interaction of Exim's &%message_size_limit%& with any size limits
31079 imposed by your anti-virus scanner.
31081 Here is a very simple scanning example:
31083 deny message = This message contains malware ($malware_name)
31087 The next example accepts messages when there is a problem with the scanner:
31089 deny message = This message contains malware ($malware_name)
31091 malware = */defer_ok
31093 The next example shows how to use an ACL variable to scan with both sophie and
31094 aveserver. It assumes you have set:
31096 av_scanner = $acl_m0
31098 in the main Exim configuration.
31100 deny message = This message contains malware ($malware_name)
31101 set acl_m0 = sophie
31104 deny message = This message contains malware ($malware_name)
31105 set acl_m0 = aveserver
31110 .section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass"
31111 .cindex "content scanning" "for spam"
31112 .cindex "spam scanning"
31113 .cindex "SpamAssassin"
31115 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
31116 score and a report for the message.
31117 Support is also provided for Rspamd.
31119 For more information about installation and configuration of SpamAssassin or
31120 Rspamd refer to their respective websites at
31121 &url(http://spamassassin.apache.org) and &url(http://www.rspamd.com)
31123 SpamAssassin can be installed with CPAN by running:
31125 perl -MCPAN -e 'install Mail::SpamAssassin'
31127 SpamAssassin has its own set of configuration files. Please review its
31128 documentation to see how you can tweak it. The default installation should work
31131 .oindex "&%spamd_address%&"
31132 By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
31133 intend to use an instance running on the local host you do not need to set
31134 &%spamd_address%&. If you intend to use another host or port for SpamAssassin,
31135 you must set the &%spamd_address%& option in the global part of the Exim
31136 configuration as follows (example):
31138 spamd_address = 192.168.99.45 387
31141 To use Rspamd (which by default listens on all local addresses
31143 you should add &%variant=rspamd%& after the address/port pair, for example:
31145 spamd_address = 127.0.0.1 11333 variant=rspamd
31148 As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
31149 sockets. If you want to us these, supply &%spamd_address%& with an absolute
31150 file name instead of an address/port pair:
31152 spamd_address = /var/run/spamd_socket
31154 You can have multiple &%spamd%& servers to improve scalability. These can
31155 reside on other hardware reachable over the network. To specify multiple
31156 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
31157 option, separated with colons (the separator can be changed in the usual way):
31159 spamd_address = 192.168.2.10 783 : \
31160 192.168.2.11 783 : \
31163 Up to 32 &%spamd%& servers are supported.
31164 When a server fails to respond to the connection attempt, all other
31165 servers are tried until one succeeds. If no server responds, the &%spam%&
31168 Unix and TCP socket specifications may be mixed in any order.
31169 Each element of the list is a list itself, space-separated by default
31170 and changeable in the usual way.
31172 For TCP socket specifications a host name or IP (v4 or v6, but
31173 subject to list-separator quoting rules) address can be used,
31174 and the port can be one or a dash-separated pair.
31175 In the latter case, the range is tried in strict order.
31177 Elements after the first for Unix sockets, or second for TCP socket,
31179 The supported options are:
31181 pri=<priority> Selection priority
31182 weight=<value> Selection bias
31183 time=<start>-<end> Use only between these times of day
31184 retry=<timespec> Retry on connect fail
31185 tmo=<timespec> Connection time limit
31186 variant=rspamd Use Rspamd rather than SpamAssassin protocol
31189 The &`pri`& option specifies a priority for the server within the list,
31190 higher values being tried first.
31191 The default priority is 1.
31193 The &`weight`& option specifies a selection bias.
31194 Within a priority set
31195 servers are queried in a random fashion, weighted by this value.
31196 The default value for selection bias is 1.
31198 Time specifications for the &`time`& option are <hour>.<minute>.<second>
31199 in the local time zone; each element being one or more digits.
31200 Either the seconds or both minutes and seconds, plus the leading &`.`&
31201 characters, may be omitted and will be taken as zero.
31203 Timeout specifications for the &`retry`& and &`tmo`& options
31204 are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
31206 The &`tmo`& option specifies an overall timeout for communication.
31207 The default value is two minutes.
31209 The &`retry`& option specifies a time after which a single retry for
31210 a failed connect is made.
31211 The default is to not retry.
31213 The &%spamd_address%& variable is expanded before use if it starts with
31214 a dollar sign. In this case, the expansion may return a string that is
31215 used as the list so that multiple spamd servers can be the result of an
31218 .vindex "&$callout_address$&"
31219 When a connection is made to the server the expansion variable &$callout_address$&
31220 is set to record the actual address used.
31222 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
31223 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
31225 deny message = This message was classified as SPAM
31228 The right-hand side of the &%spam%& condition specifies a name. This is
31229 relevant if you have set up multiple SpamAssassin profiles. If you do not want
31230 to scan using a specific profile, but rather use the SpamAssassin system-wide
31231 default profile, you can scan for an unknown name, or simply use &"nobody"&.
31232 Rspamd does not use this setting. However, you must put something on the
31235 The name allows you to use per-domain or per-user antispam profiles in
31236 principle, but this is not straightforward in practice, because a message may
31237 have multiple recipients, not necessarily all in the same domain. Because the
31238 &%spam%& condition has to be called from a DATA-time ACL in order to be able to
31239 read the contents of the message, the variables &$local_part$& and &$domain$&
31241 Careful enforcement of single-recipient messages
31242 (e.g. by responding with defer in the recipient ACL for all recipients
31244 or the use of PRDR,
31245 .cindex "PRDR" "use for per-user SpamAssassin profiles"
31246 are needed to use this feature.
31248 The right-hand side of the &%spam%& condition is expanded before being used, so
31249 you can put lookups or conditions there. When the right-hand side evaluates to
31250 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
31253 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
31254 large ones may cause significant performance degradation. As most spam messages
31255 are quite small, it is recommended that you do not scan the big ones. For
31258 deny message = This message was classified as SPAM
31259 condition = ${if < {$message_size}{10K}}
31263 The &%spam%& condition returns true if the threshold specified in the user's
31264 SpamAssassin profile has been matched or exceeded. If you want to use the
31265 &%spam%& condition for its side effects (see the variables below), you can make
31266 it always return &"true"& by appending &`:true`& to the username.
31268 .cindex "spam scanning" "returned variables"
31269 When the &%spam%& condition is run, it sets up a number of expansion
31271 Except for &$spam_report$&,
31272 these variables are saved with the received message so are
31273 available for use at delivery time.
31276 .vitem &$spam_score$&
31277 The spam score of the message, for example &"3.4"& or &"30.5"&. This is useful
31278 for inclusion in log or reject messages.
31280 .vitem &$spam_score_int$&
31281 The spam score of the message, multiplied by ten, as an integer value. For
31282 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
31283 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
31284 The integer value is useful for numeric comparisons in conditions.
31286 .vitem &$spam_bar$&
31287 A string consisting of a number of &"+"& or &"-"& characters, representing the
31288 integer part of the spam score value. A spam score of 4.4 would have a
31289 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
31290 headers, since MUAs can match on such strings. The maximum length of the
31291 spam bar is 50 characters.
31293 .vitem &$spam_report$&
31294 A multiline text table, containing the full SpamAssassin report for the
31295 message. Useful for inclusion in headers or reject messages.
31296 This variable is only usable in a DATA-time ACL.
31298 .vitem &$spam_action$&
31299 For SpamAssassin either 'reject' or 'no action' depending on the
31300 spam score versus threshold.
31301 For Rspamd, the recommended action.
31305 The &%spam%& condition caches its results unless expansion in
31306 spamd_address was used. If you call it again with the same user name, it
31307 does not scan again, but rather returns the same values as before.
31309 The &%spam%& condition returns DEFER if there is any error while running
31310 the message through SpamAssassin or if the expansion of spamd_address
31311 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
31312 statement block), append &`/defer_ok`& to the right-hand side of the
31313 spam condition, like this:
31315 deny message = This message was classified as SPAM
31316 spam = joe/defer_ok
31318 This causes messages to be accepted even if there is a problem with &%spamd%&.
31320 Here is a longer, commented example of the use of the &%spam%&
31323 # put headers in all messages (no matter if spam or not)
31324 warn spam = nobody:true
31325 add_header = X-Spam-Score: $spam_score ($spam_bar)
31326 add_header = X-Spam-Report: $spam_report
31328 # add second subject line with *SPAM* marker when message
31329 # is over threshold
31331 add_header = Subject: *SPAM* $h_Subject:
31333 # reject spam at high scores (> 12)
31334 deny message = This message scored $spam_score spam points.
31336 condition = ${if >{$spam_score_int}{120}{1}{0}}
31341 .section "Scanning MIME parts" "SECTscanmimepart"
31342 .cindex "content scanning" "MIME parts"
31343 .cindex "MIME content scanning"
31344 .oindex "&%acl_smtp_mime%&"
31345 .oindex "&%acl_not_smtp_mime%&"
31346 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
31347 each MIME part of an SMTP message, including multipart types, in the sequence
31348 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
31349 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
31350 options may both refer to the same ACL if you want the same processing in both
31353 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
31354 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
31355 the case of a non-SMTP message. However, a MIME ACL is called only if the
31356 message contains a &'Content-Type:'& header line. When a call to a MIME
31357 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
31358 result code is sent to the client. In the case of an SMTP message, the
31359 &%acl_smtp_data%& ACL is not called when this happens.
31361 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
31362 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
31363 condition to match against the raw MIME part. You can also use the
31364 &%mime_regex%& condition to match against the decoded MIME part (see section
31365 &<<SECTscanregex>>&).
31367 At the start of a MIME ACL, a number of variables are set from the header
31368 information for the relevant MIME part. These are described below. The contents
31369 of the MIME part are not by default decoded into a disk file except for MIME
31370 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
31371 part into a disk file, you can use the &%decode%& condition. The general
31374 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
31376 The right hand side is expanded before use. After expansion,
31380 &"0"& or &"false"&, in which case no decoding is done.
31382 The string &"default"&. In that case, the file is put in the temporary
31383 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
31384 a sequential file name consisting of the message id and a sequence number. The
31385 full path and name is available in &$mime_decoded_filename$& after decoding.
31387 A full path name starting with a slash. If the full name is an existing
31388 directory, it is used as a replacement for the default directory. The filename
31389 is then sequentially assigned. If the path does not exist, it is used as
31390 the full path and file name.
31392 If the string does not start with a slash, it is used as the
31393 filename, and the default path is then used.
31395 The &%decode%& condition normally succeeds. It is only false for syntax
31396 errors or unusual circumstances such as memory shortages. You can easily decode
31397 a file with its original, proposed filename using
31399 decode = $mime_filename
31401 However, you should keep in mind that &$mime_filename$& might contain
31402 anything. If you place files outside of the default path, they are not
31403 automatically unlinked.
31405 For RFC822 attachments (these are messages attached to messages, with a
31406 content-type of &"message/rfc822"&), the ACL is called again in the same manner
31407 as for the primary message, only that the &$mime_is_rfc822$& expansion
31408 variable is set (see below). Attached messages are always decoded to disk
31409 before being checked, and the files are unlinked once the check is done.
31411 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
31412 used to match regular expressions against raw and decoded MIME parts,
31413 respectively. They are described in section &<<SECTscanregex>>&.
31415 .cindex "MIME content scanning" "returned variables"
31416 The following list describes all expansion variables that are
31417 available in the MIME ACL:
31420 .vitem &$mime_boundary$&
31421 If the current part is a multipart (see &$mime_is_multipart$&) below, it should
31422 have a boundary string, which is stored in this variable. If the current part
31423 has no boundary parameter in the &'Content-Type:'& header, this variable
31424 contains the empty string.
31426 .vitem &$mime_charset$&
31427 This variable contains the character set identifier, if one was found in the
31428 &'Content-Type:'& header. Examples for charset identifiers are:
31434 Please note that this value is not normalized, so you should do matches
31435 case-insensitively.
31437 .vitem &$mime_content_description$&
31438 This variable contains the normalized content of the &'Content-Description:'&
31439 header. It can contain a human-readable description of the parts content. Some
31440 implementations repeat the filename for attachments here, but they are usually
31441 only used for display purposes.
31443 .vitem &$mime_content_disposition$&
31444 This variable contains the normalized content of the &'Content-Disposition:'&
31445 header. You can expect strings like &"attachment"& or &"inline"& here.
31447 .vitem &$mime_content_id$&
31448 This variable contains the normalized content of the &'Content-ID:'& header.
31449 This is a unique ID that can be used to reference a part from another part.
31451 .vitem &$mime_content_size$&
31452 This variable is set only after the &%decode%& modifier (see above) has been
31453 successfully run. It contains the size of the decoded part in kilobytes. The
31454 size is always rounded up to full kilobytes, so only a completely empty part
31455 has a &$mime_content_size$& of zero.
31457 .vitem &$mime_content_transfer_encoding$&
31458 This variable contains the normalized content of the
31459 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
31460 type. Typical values are &"base64"& and &"quoted-printable"&.
31462 .vitem &$mime_content_type$&
31463 If the MIME part has a &'Content-Type:'& header, this variable contains its
31464 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
31465 are some examples of popular MIME types, as they may appear in this variable:
31469 application/octet-stream
31473 If the MIME part has no &'Content-Type:'& header, this variable contains the
31476 .vitem &$mime_decoded_filename$&
31477 This variable is set only after the &%decode%& modifier (see above) has been
31478 successfully run. It contains the full path and file name of the file
31479 containing the decoded data.
31484 .vitem &$mime_filename$&
31485 This is perhaps the most important of the MIME variables. It contains a
31486 proposed filename for an attachment, if one was found in either the
31487 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
31490 decoded, but no additional sanity checks are done.
31492 found, this variable contains the empty string.
31494 .vitem &$mime_is_coverletter$&
31495 This variable attempts to differentiate the &"cover letter"& of an e-mail from
31496 attached data. It can be used to clamp down on flashy or unnecessarily encoded
31497 content in the cover letter, while not restricting attachments at all.
31499 The variable contains 1 (true) for a MIME part believed to be part of the
31500 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
31504 The outermost MIME part of a message is always a cover letter.
31507 If a multipart/alternative or multipart/related MIME part is a cover letter,
31508 so are all MIME subparts within that multipart.
31511 If any other multipart is a cover letter, the first subpart is a cover letter,
31512 and the rest are attachments.
31515 All parts contained within an attachment multipart are attachments.
31518 As an example, the following will ban &"HTML mail"& (including that sent with
31519 alternative plain text), while allowing HTML files to be attached. HTML
31520 coverletter mail attached to non-HMTL coverletter mail will also be allowed:
31522 deny message = HTML mail is not accepted here
31523 !condition = $mime_is_rfc822
31524 condition = $mime_is_coverletter
31525 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
31527 .vitem &$mime_is_multipart$&
31528 This variable has the value 1 (true) when the current part has the main type
31529 &"multipart"&, for example &"multipart/alternative"& or &"multipart/mixed"&.
31530 Since multipart entities only serve as containers for other parts, you may not
31531 want to carry out specific actions on them.
31533 .vitem &$mime_is_rfc822$&
31534 This variable has the value 1 (true) if the current part is not a part of the
31535 checked message itself, but part of an attached message. Attached message
31536 decoding is fully recursive.
31538 .vitem &$mime_part_count$&
31539 This variable is a counter that is raised for each processed MIME part. It
31540 starts at zero for the very first part (which is usually a multipart). The
31541 counter is per-message, so it is reset when processing RFC822 attachments (see
31542 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
31543 complete, so you can use it in the DATA ACL to determine the number of MIME
31544 parts of a message. For non-MIME messages, this variable contains the value -1.
31549 .section "Scanning with regular expressions" "SECTscanregex"
31550 .cindex "content scanning" "with regular expressions"
31551 .cindex "regular expressions" "content scanning with"
31552 You can specify your own custom regular expression matches on the full body of
31553 the message, or on individual MIME parts.
31555 The &%regex%& condition takes one or more regular expressions as arguments and
31556 matches them against the full message (when called in the DATA ACL) or a raw
31557 MIME part (when called in the MIME ACL). The &%regex%& condition matches
31558 linewise, with a maximum line length of 32K characters. That means you cannot
31559 have multiline matches with the &%regex%& condition.
31561 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
31562 to 32K of decoded content (the whole content at once, not linewise). If the
31563 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
31564 is decoded automatically when &%mime_regex%& is executed (using default path
31565 and filename values). If the decoded data is larger than 32K, only the first
31566 32K characters are checked.
31568 The regular expressions are passed as a colon-separated list. To include a
31569 literal colon, you must double it. Since the whole right-hand side string is
31570 expanded before being used, you must also escape dollar signs and backslashes
31571 with more backslashes, or use the &`\N`& facility to disable expansion.
31572 Here is a simple example that contains two regular expressions:
31574 deny message = contains blacklisted regex ($regex_match_string)
31575 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
31577 The conditions returns true if any one of the regular expressions matches. The
31578 &$regex_match_string$& expansion variable is then set up and contains the
31579 matching regular expression.
31580 The expansion variables &$regex1$& &$regex2$& etc
31581 are set to any substrings captured by the regular expression.
31583 &*Warning*&: With large messages, these conditions can be fairly
31589 .section "The demime condition" "SECTdemimecond"
31590 .cindex "content scanning" "MIME checking"
31591 .cindex "MIME content scanning"
31592 The &%demime%& ACL condition provides MIME unpacking, sanity checking and file
31593 extension blocking. It is usable only in the DATA and non-SMTP ACLs. The
31594 &%demime%& condition uses a simpler interface to MIME decoding than the MIME
31595 ACL functionality, but provides no additional facilities. Please note that this
31596 condition is deprecated and kept only for backward compatibility. You must set
31597 the WITH_OLD_DEMIME option in &_Local/Makefile_& at build time to be able to
31598 use the &%demime%& condition.
31600 The &%demime%& condition unpacks MIME containers in the message. It detects
31601 errors in MIME containers and can match file extensions found in the message
31602 against a list. Using this facility produces files containing the unpacked MIME
31603 parts of the message in the temporary scan directory. If you do antivirus
31604 scanning, it is recommended that you use the &%demime%& condition before the
31605 antivirus (&%malware%&) condition.
31607 On the right-hand side of the &%demime%& condition you can pass a
31608 colon-separated list of file extensions that it should match against. For
31611 deny message = Found blacklisted file attachment
31612 demime = vbs:com:bat:pif:prf:lnk
31614 If one of the file extensions is found, the condition is true, otherwise it is
31615 false. If there is a temporary error while demimeing (for example, &"disk
31616 full"&), the condition defers, and the message is temporarily rejected (unless
31617 the condition is on a &%warn%& verb).
31619 The right-hand side is expanded before being treated as a list, so you can have
31620 conditions and lookups there. If it expands to an empty string, &"false"&, or
31621 zero (&"0"&), no demimeing is done and the condition is false.
31623 The &%demime%& condition set the following variables:
31626 .vitem &$demime_errorlevel$&
31627 .vindex "&$demime_errorlevel$&"
31628 When an error is detected in a MIME container, this variable contains the
31629 severity of the error, as an integer number. The higher the value, the more
31630 severe the error (the current maximum value is 3). If this variable is unset or
31631 zero, no error occurred.
31633 .vitem &$demime_reason$&
31634 .vindex "&$demime_reason$&"
31635 When &$demime_errorlevel$& is greater than zero, this variable contains a
31636 human-readable text string describing the MIME error that occurred.
31640 .vitem &$found_extension$&
31641 .vindex "&$found_extension$&"
31642 When the &%demime%& condition is true, this variable contains the file
31643 extension it found.
31646 Both &$demime_errorlevel$& and &$demime_reason$& are set by the first call of
31647 the &%demime%& condition, and are not changed on subsequent calls.
31649 If you do not want to check for file extensions, but rather use the &%demime%&
31650 condition for unpacking or error checking purposes, pass &"*"& as the
31651 right-hand side value. Here is a more elaborate example of how to use this
31654 # Reject messages with serious MIME container errors
31655 deny message = Found MIME error ($demime_reason).
31657 condition = ${if >{$demime_errorlevel}{2}{1}{0}}
31659 # Reject known virus spreading file extensions.
31660 # Accepting these is pretty much braindead.
31661 deny message = contains $found_extension file (blacklisted).
31662 demime = com:vbs:bat:pif:scr
31664 # Freeze .exe and .doc files. Postmaster can
31665 # examine them and eventually thaw them.
31666 deny log_message = Another $found_extension file.
31675 . ////////////////////////////////////////////////////////////////////////////
31676 . ////////////////////////////////////////////////////////////////////////////
31678 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
31679 "Local scan function"
31680 .scindex IIDlosca "&[local_scan()]& function" "description of"
31681 .cindex "customizing" "input scan using C function"
31682 .cindex "policy control" "by local scan function"
31683 In these days of email worms, viruses, and ever-increasing spam, some sites
31684 want to apply a lot of checking to messages before accepting them.
31686 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
31687 passing messages to external virus and spam scanning software. You can also do
31688 a certain amount in Exim itself through string expansions and the &%condition%&
31689 condition in the ACL that runs after the SMTP DATA command or the ACL for
31690 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
31692 To allow for further customization to a site's own requirements, there is the
31693 possibility of linking Exim with a private message scanning function, written
31694 in C. If you want to run code that is written in something other than C, you
31695 can of course use a little C stub to call it.
31697 The local scan function is run once for every incoming message, at the point
31698 when Exim is just about to accept the message.
31699 It can therefore be used to control non-SMTP messages from local processes as
31700 well as messages arriving via SMTP.
31702 Exim applies a timeout to calls of the local scan function, and there is an
31703 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
31704 Zero means &"no timeout"&.
31705 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
31706 before calling the local scan function, so that the most common types of crash
31707 are caught. If the timeout is exceeded or one of those signals is caught, the
31708 incoming message is rejected with a temporary error if it is an SMTP message.
31709 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
31710 code. The incident is logged on the main and reject logs.
31714 .section "Building Exim to use a local scan function" "SECID207"
31715 .cindex "&[local_scan()]& function" "building Exim to use"
31716 To make use of the local scan function feature, you must tell Exim where your
31717 function is before building Exim, by setting LOCAL_SCAN_SOURCE in your
31718 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
31719 directory, so you might set
31721 LOCAL_SCAN_SOURCE=Local/local_scan.c
31723 for example. The function must be called &[local_scan()]&. It is called by
31724 Exim after it has received a message, when the success return code is about to
31725 be sent. This is after all the ACLs have been run. The return code from your
31726 function controls whether the message is actually accepted or not. There is a
31727 commented template function (that just accepts the message) in the file
31728 _src/local_scan.c_.
31730 If you want to make use of Exim's run time configuration file to set options
31731 for your &[local_scan()]& function, you must also set
31733 LOCAL_SCAN_HAS_OPTIONS=yes
31735 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
31740 .section "API for local_scan()" "SECTapiforloc"
31741 .cindex "&[local_scan()]& function" "API description"
31742 You must include this line near the start of your code:
31744 #include "local_scan.h"
31746 This header file defines a number of variables and other values, and the
31747 prototype for the function itself. Exim is coded to use unsigned char values
31748 almost exclusively, and one of the things this header defines is a shorthand
31749 for &`unsigned char`& called &`uschar`&.
31750 It also contains the following macro definitions, to simplify casting character
31751 strings and pointers to character strings:
31753 #define CS (char *)
31754 #define CCS (const char *)
31755 #define CSS (char **)
31756 #define US (unsigned char *)
31757 #define CUS (const unsigned char *)
31758 #define USS (unsigned char **)
31760 The function prototype for &[local_scan()]& is:
31762 extern int local_scan(int fd, uschar **return_text);
31764 The arguments are as follows:
31767 &%fd%& is a file descriptor for the file that contains the body of the message
31768 (the -D file). The file is open for reading and writing, but updating it is not
31769 recommended. &*Warning*&: You must &'not'& close this file descriptor.
31771 The descriptor is positioned at character 19 of the file, which is the first
31772 character of the body itself, because the first 19 characters are the message
31773 id followed by &`-D`& and a newline. If you rewind the file, you should use the
31774 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
31775 case this changes in some future version.
31777 &%return_text%& is an address which you can use to return a pointer to a text
31778 string at the end of the function. The value it points to on entry is NULL.
31781 The function must return an &%int%& value which is one of the following macros:
31784 .vitem &`LOCAL_SCAN_ACCEPT`&
31785 .vindex "&$local_scan_data$&"
31786 The message is accepted. If you pass back a string of text, it is saved with
31787 the message, and made available in the variable &$local_scan_data$&. No
31788 newlines are permitted (if there are any, they are turned into spaces) and the
31789 maximum length of text is 1000 characters.
31791 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
31792 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
31793 queued without immediate delivery, and is frozen.
31795 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
31796 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
31797 queued without immediate delivery.
31799 .vitem &`LOCAL_SCAN_REJECT`&
31800 The message is rejected; the returned text is used as an error message which is
31801 passed back to the sender and which is also logged. Newlines are permitted &--
31802 they cause a multiline response for SMTP rejections, but are converted to
31803 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
31806 .vitem &`LOCAL_SCAN_TEMPREJECT`&
31807 The message is temporarily rejected; the returned text is used as an error
31808 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
31811 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
31812 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
31813 message is not written to the reject log. It has the effect of unsetting the
31814 &%rejected_header%& log selector for just this rejection. If
31815 &%rejected_header%& is already unset (see the discussion of the
31816 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
31817 same as LOCAL_SCAN_REJECT.
31819 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
31820 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
31821 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
31824 If the message is not being received by interactive SMTP, rejections are
31825 reported by writing to &%stderr%& or by sending an email, as configured by the
31826 &%-oe%& command line options.
31830 .section "Configuration options for local_scan()" "SECTconoptloc"
31831 .cindex "&[local_scan()]& function" "configuration options"
31832 It is possible to have option settings in the main configuration file
31833 that set values in static variables in the &[local_scan()]& module. If you
31834 want to do this, you must have the line
31836 LOCAL_SCAN_HAS_OPTIONS=yes
31838 in your &_Local/Makefile_& when you build Exim. (This line is in
31839 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
31840 file, you must define static variables to hold the option values, and a table
31843 The table must be a vector called &%local_scan_options%&, of type
31844 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
31845 and a pointer to the variable that holds the value. The entries must appear in
31846 alphabetical order. Following &%local_scan_options%& you must also define a
31847 variable called &%local_scan_options_count%& that contains the number of
31848 entries in the table. Here is a short example, showing two kinds of option:
31850 static int my_integer_option = 42;
31851 static uschar *my_string_option = US"a default string";
31853 optionlist local_scan_options[] = {
31854 { "my_integer", opt_int, &my_integer_option },
31855 { "my_string", opt_stringptr, &my_string_option }
31858 int local_scan_options_count =
31859 sizeof(local_scan_options)/sizeof(optionlist);
31861 The values of the variables can now be changed from Exim's runtime
31862 configuration file by including a local scan section as in this example:
31866 my_string = some string of text...
31868 The available types of option data are as follows:
31871 .vitem &*opt_bool*&
31872 This specifies a boolean (true/false) option. The address should point to a
31873 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
31874 that are defined as &"1"& and &"0"&, respectively. If you want to detect
31875 whether such a variable has been set at all, you can initialize it to
31876 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
31879 .vitem &*opt_fixed*&
31880 This specifies a fixed point number, such as is used for load averages.
31881 The address should point to a variable of type &`int`&. The value is stored
31882 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
31885 This specifies an integer; the address should point to a variable of type
31886 &`int`&. The value may be specified in any of the integer formats accepted by
31889 .vitem &*opt_mkint*&
31890 This is the same as &%opt_int%&, except that when such a value is output in a
31891 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
31892 printed with the suffix K or M.
31894 .vitem &*opt_octint*&
31895 This also specifies an integer, but the value is always interpreted as an
31896 octal integer, whether or not it starts with the digit zero, and it is
31897 always output in octal.
31899 .vitem &*opt_stringptr*&
31900 This specifies a string value; the address must be a pointer to a
31901 variable that points to a string (for example, of type &`uschar *`&).
31903 .vitem &*opt_time*&
31904 This specifies a time interval value. The address must point to a variable of
31905 type &`int`&. The value that is placed there is a number of seconds.
31908 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
31909 out the values of all the &[local_scan()]& options.
31913 .section "Available Exim variables" "SECID208"
31914 .cindex "&[local_scan()]& function" "available Exim variables"
31915 The header &_local_scan.h_& gives you access to a number of C variables. These
31916 are the only ones that are guaranteed to be maintained from release to release.
31917 Note, however, that you can obtain the value of any Exim expansion variable,
31918 including &$recipients$&, by calling &'expand_string()'&. The exported
31919 C variables are as follows:
31922 .vitem &*int&~body_linecount*&
31923 This variable contains the number of lines in the message's body.
31925 .vitem &*int&~body_zerocount*&
31926 This variable contains the number of binary zero bytes in the message's body.
31928 .vitem &*unsigned&~int&~debug_selector*&
31929 This variable is set to zero when no debugging is taking place. Otherwise, it
31930 is a bitmap of debugging selectors. Two bits are identified for use in
31931 &[local_scan()]&; they are defined as macros:
31934 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
31935 testing option that is not privileged &-- any caller may set it. All the
31936 other selector bits can be set only by admin users.
31939 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
31940 by the &`+local_scan`& debug selector. It is not included in the default set
31944 Thus, to write to the debugging output only when &`+local_scan`& has been
31945 selected, you should use code like this:
31947 if ((debug_selector & D_local_scan) != 0)
31948 debug_printf("xxx", ...);
31950 .vitem &*uschar&~*expand_string_message*&
31951 After a failing call to &'expand_string()'& (returned value NULL), the
31952 variable &%expand_string_message%& contains the error message, zero-terminated.
31954 .vitem &*header_line&~*header_list*&
31955 A pointer to a chain of header lines. The &%header_line%& structure is
31958 .vitem &*header_line&~*header_last*&
31959 A pointer to the last of the header lines.
31961 .vitem &*uschar&~*headers_charset*&
31962 The value of the &%headers_charset%& configuration option.
31964 .vitem &*BOOL&~host_checking*&
31965 This variable is TRUE during a host checking session that is initiated by the
31966 &%-bh%& command line option.
31968 .vitem &*uschar&~*interface_address*&
31969 The IP address of the interface that received the message, as a string. This
31970 is NULL for locally submitted messages.
31972 .vitem &*int&~interface_port*&
31973 The port on which this message was received. When testing with the &%-bh%&
31974 command line option, the value of this variable is -1 unless a port has been
31975 specified via the &%-oMi%& option.
31977 .vitem &*uschar&~*message_id*&
31978 This variable contains Exim's message id for the incoming message (the value of
31979 &$message_exim_id$&) as a zero-terminated string.
31981 .vitem &*uschar&~*received_protocol*&
31982 The name of the protocol by which the message was received.
31984 .vitem &*int&~recipients_count*&
31985 The number of accepted recipients.
31987 .vitem &*recipient_item&~*recipients_list*&
31988 .cindex "recipient" "adding in local scan"
31989 .cindex "recipient" "removing in local scan"
31990 The list of accepted recipients, held in a vector of length
31991 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
31992 can add additional recipients by calling &'receive_add_recipient()'& (see
31993 below). You can delete recipients by removing them from the vector and
31994 adjusting the value in &%recipients_count%&. In particular, by setting
31995 &%recipients_count%& to zero you remove all recipients. If you then return the
31996 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
31997 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
31998 and then call &'receive_add_recipient()'& as often as needed.
32000 .vitem &*uschar&~*sender_address*&
32001 The envelope sender address. For bounce messages this is the empty string.
32003 .vitem &*uschar&~*sender_host_address*&
32004 The IP address of the sending host, as a string. This is NULL for
32005 locally-submitted messages.
32007 .vitem &*uschar&~*sender_host_authenticated*&
32008 The name of the authentication mechanism that was used, or NULL if the message
32009 was not received over an authenticated SMTP connection.
32011 .vitem &*uschar&~*sender_host_name*&
32012 The name of the sending host, if known.
32014 .vitem &*int&~sender_host_port*&
32015 The port on the sending host.
32017 .vitem &*BOOL&~smtp_input*&
32018 This variable is TRUE for all SMTP input, including BSMTP.
32020 .vitem &*BOOL&~smtp_batched_input*&
32021 This variable is TRUE for BSMTP input.
32023 .vitem &*int&~store_pool*&
32024 The contents of this variable control which pool of memory is used for new
32025 requests. See section &<<SECTmemhanloc>>& for details.
32029 .section "Structure of header lines" "SECID209"
32030 The &%header_line%& structure contains the members listed below.
32031 You can add additional header lines by calling the &'header_add()'& function
32032 (see below). You can cause header lines to be ignored (deleted) by setting
32037 .vitem &*struct&~header_line&~*next*&
32038 A pointer to the next header line, or NULL for the last line.
32040 .vitem &*int&~type*&
32041 A code identifying certain headers that Exim recognizes. The codes are printing
32042 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
32043 Notice in particular that any header line whose type is * is not transmitted
32044 with the message. This flagging is used for header lines that have been
32045 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
32046 lines.) Effectively, * means &"deleted"&.
32048 .vitem &*int&~slen*&
32049 The number of characters in the header line, including the terminating and any
32052 .vitem &*uschar&~*text*&
32053 A pointer to the text of the header. It always ends with a newline, followed by
32054 a zero byte. Internal newlines are preserved.
32059 .section "Structure of recipient items" "SECID210"
32060 The &%recipient_item%& structure contains these members:
32063 .vitem &*uschar&~*address*&
32064 This is a pointer to the recipient address as it was received.
32066 .vitem &*int&~pno*&
32067 This is used in later Exim processing when top level addresses are created by
32068 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
32069 and must always contain -1 at this stage.
32071 .vitem &*uschar&~*errors_to*&
32072 If this value is not NULL, bounce messages caused by failing to deliver to the
32073 recipient are sent to the address it contains. In other words, it overrides the
32074 envelope sender for this one recipient. (Compare the &%errors_to%& generic
32075 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
32076 an unqualified address, Exim qualifies it using the domain from
32077 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
32078 is NULL for all recipients.
32083 .section "Available Exim functions" "SECID211"
32084 .cindex "&[local_scan()]& function" "available Exim functions"
32085 The header &_local_scan.h_& gives you access to a number of Exim functions.
32086 These are the only ones that are guaranteed to be maintained from release to
32090 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
32091 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
32093 This function creates a child process that runs the command specified by
32094 &%argv%&. The environment for the process is specified by &%envp%&, which can
32095 be NULL if no environment variables are to be passed. A new umask is supplied
32096 for the process in &%newumask%&.
32098 Pipes to the standard input and output of the new process are set up
32099 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
32100 standard error is cloned to the standard output. If there are any file
32101 descriptors &"in the way"& in the new process, they are closed. If the final
32102 argument is TRUE, the new process is made into a process group leader.
32104 The function returns the pid of the new process, or -1 if things go wrong.
32106 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
32107 This function waits for a child process to terminate, or for a timeout (in
32108 seconds) to expire. A timeout value of zero means wait as long as it takes. The
32109 return value is as follows:
32114 The process terminated by a normal exit and the value is the process
32120 The process was terminated by a signal and the value is the negation of the
32126 The process timed out.
32130 The was some other error in wait(); &%errno%& is still set.
32133 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
32134 This function provide you with a means of submitting a new message to
32135 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
32136 want, but this packages it all up for you.) The function creates a pipe,
32137 forks a subprocess that is running
32139 exim -t -oem -oi -f <>
32141 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
32142 that is connected to the standard input. The yield of the function is the PID
32143 of the subprocess. You can then write a message to the file descriptor, with
32144 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
32146 When you have finished, call &'child_close()'& to wait for the process to
32147 finish and to collect its ending status. A timeout value of zero is usually
32148 fine in this circumstance. Unless you have made a mistake with the recipient
32149 addresses, you should get a return code of zero.
32152 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
32153 *sender_authentication)*&
32154 This function is a more sophisticated version of &'child_open()'&. The command
32157 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
32159 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
32162 .vitem &*void&~debug_printf(char&~*,&~...)*&
32163 This is Exim's debugging function, with arguments as for &'(printf()'&. The
32164 output is written to the standard error stream. If no debugging is selected,
32165 calls to &'debug_printf()'& have no effect. Normally, you should make calls
32166 conditional on the &`local_scan`& debug selector by coding like this:
32168 if ((debug_selector & D_local_scan) != 0)
32169 debug_printf("xxx", ...);
32172 .vitem &*uschar&~*expand_string(uschar&~*string)*&
32173 This is an interface to Exim's string expansion code. The return value is the
32174 expanded string, or NULL if there was an expansion failure.
32175 The C variable &%expand_string_message%& contains an error message after an
32176 expansion failure. If expansion does not change the string, the return value is
32177 the pointer to the input string. Otherwise, the return value points to a new
32178 block of memory that was obtained by a call to &'store_get()'&. See section
32179 &<<SECTmemhanloc>>& below for a discussion of memory handling.
32181 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
32182 This function allows you to an add additional header line at the end of the
32183 existing ones. The first argument is the type, and should normally be a space
32184 character. The second argument is a format string and any number of
32185 substitution arguments as for &[sprintf()]&. You may include internal newlines
32186 if you want, and you must ensure that the string ends with a newline.
32188 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
32189 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
32190 This function adds a new header line at a specified point in the header
32191 chain. The header itself is specified as for &'header_add()'&.
32193 If &%name%& is NULL, the new header is added at the end of the chain if
32194 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
32195 NULL, the header lines are searched for the first non-deleted header that
32196 matches the name. If one is found, the new header is added before it if
32197 &%after%& is false. If &%after%& is true, the new header is added after the
32198 found header and any adjacent subsequent ones with the same name (even if
32199 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
32200 option controls where the header is added. If it is true, addition is at the
32201 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
32202 headers, or at the top if there are no &'Received:'& headers, you could use
32204 header_add_at_position(TRUE, US"Received", TRUE,
32205 ' ', "X-xxx: ...");
32207 Normally, there is always at least one non-deleted &'Received:'& header, but
32208 there may not be if &%received_header_text%& expands to an empty string.
32211 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
32212 This function removes header lines. If &%occurrence%& is zero or negative, all
32213 occurrences of the header are removed. If occurrence is greater than zero, that
32214 particular instance of the header is removed. If no header(s) can be found that
32215 match the specification, the function does nothing.
32218 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
32219 int&~length,&~BOOL&~notdel)*&"
32220 This function tests whether the given header has the given name. It is not just
32221 a string comparison, because white space is permitted between the name and the
32222 colon. If the &%notdel%& argument is true, a false return is forced for all
32223 &"deleted"& headers; otherwise they are not treated specially. For example:
32225 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
32227 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
32228 .cindex "base64 encoding" "functions for &[local_scan()]& use"
32229 This function base64-encodes a string, which is passed by address and length.
32230 The text may contain bytes of any value, including zero. The result is passed
32231 back in dynamic memory that is obtained by calling &'store_get()'&. It is
32234 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
32235 This function decodes a base64-encoded string. Its arguments are a
32236 zero-terminated base64-encoded string and the address of a variable that is set
32237 to point to the result, which is in dynamic memory. The length of the decoded
32238 string is the yield of the function. If the input is invalid base64 data, the
32239 yield is -1. A zero byte is added to the end of the output string to make it
32240 easy to interpret as a C string (assuming it contains no zeros of its own). The
32241 added zero byte is not included in the returned count.
32243 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
32244 This function checks for a match in a domain list. Domains are always
32245 matched caselessly. The return value is one of the following:
32247 &`OK `& match succeeded
32248 &`FAIL `& match failed
32249 &`DEFER `& match deferred
32251 DEFER is usually caused by some kind of lookup defer, such as the
32252 inability to contact a database.
32254 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
32256 This function checks for a match in a local part list. The third argument
32257 controls case-sensitivity. The return values are as for
32258 &'lss_match_domain()'&.
32260 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
32262 This function checks for a match in an address list. The third argument
32263 controls the case-sensitivity of the local part match. The domain is always
32264 matched caselessly. The return values are as for &'lss_match_domain()'&.
32266 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
32268 This function checks for a match in a host list. The most common usage is
32271 lss_match_host(sender_host_name, sender_host_address, ...)
32273 .vindex "&$sender_host_address$&"
32274 An empty address field matches an empty item in the host list. If the host name
32275 is NULL, the name corresponding to &$sender_host_address$& is automatically
32276 looked up if a host name is required to match an item in the list. The return
32277 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
32278 returns ERROR in the case when it had to look up a host name, but the lookup
32281 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
32283 This function writes to Exim's log files. The first argument should be zero (it
32284 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
32285 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
32286 them. It specifies to which log or logs the message is written. The remaining
32287 arguments are a format and relevant insertion arguments. The string should not
32288 contain any newlines, not even at the end.
32291 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
32292 This function adds an additional recipient to the message. The first argument
32293 is the recipient address. If it is unqualified (has no domain), it is qualified
32294 with the &%qualify_recipient%& domain. The second argument must always be -1.
32296 This function does not allow you to specify a private &%errors_to%& address (as
32297 described with the structure of &%recipient_item%& above), because it pre-dates
32298 the addition of that field to the structure. However, it is easy to add such a
32299 value afterwards. For example:
32301 receive_add_recipient(US"monitor@mydom.example", -1);
32302 recipients_list[recipients_count-1].errors_to =
32303 US"postmaster@mydom.example";
32306 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
32307 This is a convenience function to remove a named recipient from the list of
32308 recipients. It returns true if a recipient was removed, and false if no
32309 matching recipient could be found. The argument must be a complete email
32316 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
32317 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
32318 This function decodes strings that are encoded according to RFC 2047. Typically
32319 these are the contents of header lines. First, each &"encoded word"& is decoded
32320 from the Q or B encoding into a byte-string. Then, if provided with the name of
32321 a charset encoding, and if the &[iconv()]& function is available, an attempt is
32322 made to translate the result to the named character set. If this fails, the
32323 binary string is returned with an error message.
32325 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
32326 maximum MIME word length is enforced. The third argument is the target
32327 encoding, or NULL if no translation is wanted.
32329 .cindex "binary zero" "in RFC 2047 decoding"
32330 .cindex "RFC 2047" "binary zero in"
32331 If a binary zero is encountered in the decoded string, it is replaced by the
32332 contents of the &%zeroval%& argument. For use with Exim headers, the value must
32333 not be 0 because header lines are handled as zero-terminated strings.
32335 The function returns the result of processing the string, zero-terminated; if
32336 &%lenptr%& is not NULL, the length of the result is set in the variable to
32337 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
32339 If an error is encountered, the function returns NULL and uses the &%error%&
32340 argument to return an error message. The variable pointed to by &%error%& is
32341 set to NULL if there is no error; it may be set non-NULL even when the function
32342 returns a non-NULL value if decoding was successful, but there was a problem
32346 .vitem &*int&~smtp_fflush(void)*&
32347 This function is used in conjunction with &'smtp_printf()'&, as described
32350 .vitem &*void&~smtp_printf(char&~*,&~...)*&
32351 The arguments of this function are like &[printf()]&; it writes to the SMTP
32352 output stream. You should use this function only when there is an SMTP output
32353 stream, that is, when the incoming message is being received via interactive
32354 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
32355 is FALSE. If you want to test for an incoming message from another host (as
32356 opposed to a local process that used the &%-bs%& command line option), you can
32357 test the value of &%sender_host_address%&, which is non-NULL when a remote host
32360 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
32361 output function, so it can be used for all forms of SMTP connection.
32363 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
32364 must start with an appropriate response code: 550 if you are going to return
32365 LOCAL_SCAN_REJECT, 451 if you are going to return
32366 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
32367 initial lines of a multi-line response, the code must be followed by a hyphen
32368 to indicate that the line is not the final response line. You must also ensure
32369 that the lines you write terminate with CRLF. For example:
32371 smtp_printf("550-this is some extra info\r\n");
32372 return LOCAL_SCAN_REJECT;
32374 Note that you can also create multi-line responses by including newlines in
32375 the data returned via the &%return_text%& argument. The added value of using
32376 &'smtp_printf()'& is that, for instance, you could introduce delays between
32377 multiple output lines.
32379 The &'smtp_printf()'& function does not return any error indication, because it
32380 does not automatically flush pending output, and therefore does not test
32381 the state of the stream. (In the main code of Exim, flushing and error
32382 detection is done when Exim is ready for the next SMTP input command.) If
32383 you want to flush the output and check for an error (for example, the
32384 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
32385 arguments. It flushes the output stream, and returns a non-zero value if there
32388 .vitem &*void&~*store_get(int)*&
32389 This function accesses Exim's internal store (memory) manager. It gets a new
32390 chunk of memory whose size is given by the argument. Exim bombs out if it ever
32391 runs out of memory. See the next section for a discussion of memory handling.
32393 .vitem &*void&~*store_get_perm(int)*&
32394 This function is like &'store_get()'&, but it always gets memory from the
32395 permanent pool. See the next section for a discussion of memory handling.
32397 .vitem &*uschar&~*string_copy(uschar&~*string)*&
32400 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
32403 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
32404 These three functions create strings using Exim's dynamic memory facilities.
32405 The first makes a copy of an entire string. The second copies up to a maximum
32406 number of characters, indicated by the second argument. The third uses a format
32407 and insertion arguments to create a new string. In each case, the result is a
32408 pointer to a new string in the current memory pool. See the next section for
32414 .section "More about Exim's memory handling" "SECTmemhanloc"
32415 .cindex "&[local_scan()]& function" "memory handling"
32416 No function is provided for freeing memory, because that is never needed.
32417 The dynamic memory that Exim uses when receiving a message is automatically
32418 recycled if another message is received by the same process (this applies only
32419 to incoming SMTP connections &-- other input methods can supply only one
32420 message at a time). After receiving the last message, a reception process
32423 Because it is recycled, the normal dynamic memory cannot be used for holding
32424 data that must be preserved over a number of incoming messages on the same SMTP
32425 connection. However, Exim in fact uses two pools of dynamic memory; the second
32426 one is not recycled, and can be used for this purpose.
32428 If you want to allocate memory that remains available for subsequent messages
32429 in the same SMTP connection, you should set
32431 store_pool = POOL_PERM
32433 before calling the function that does the allocation. There is no need to
32434 restore the value if you do not need to; however, if you do want to revert to
32435 the normal pool, you can either restore the previous value of &%store_pool%& or
32436 set it explicitly to POOL_MAIN.
32438 The pool setting applies to all functions that get dynamic memory, including
32439 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
32440 There is also a convenience function called &'store_get_perm()'& that gets a
32441 block of memory from the permanent pool while preserving the value of
32448 . ////////////////////////////////////////////////////////////////////////////
32449 . ////////////////////////////////////////////////////////////////////////////
32451 .chapter "System-wide message filtering" "CHAPsystemfilter"
32452 .scindex IIDsysfil1 "filter" "system filter"
32453 .scindex IIDsysfil2 "filtering all mail"
32454 .scindex IIDsysfil3 "system filter"
32455 The previous chapters (on ACLs and the local scan function) describe checks
32456 that can be applied to messages before they are accepted by a host. There is
32457 also a mechanism for checking messages once they have been received, but before
32458 they are delivered. This is called the &'system filter'&.
32460 The system filter operates in a similar manner to users' filter files, but it
32461 is run just once per message (however many recipients the message has).
32462 It should not normally be used as a substitute for routing, because &%deliver%&
32463 commands in a system router provide new envelope recipient addresses.
32464 The system filter must be an Exim filter. It cannot be a Sieve filter.
32466 The system filter is run at the start of a delivery attempt, before any routing
32467 is done. If a message fails to be completely delivered at the first attempt,
32468 the system filter is run again at the start of every retry.
32469 If you want your filter to do something only once per message, you can make use
32470 of the &%first_delivery%& condition in an &%if%& command in the filter to
32471 prevent it happening on retries.
32473 .vindex "&$domain$&"
32474 .vindex "&$local_part$&"
32475 &*Warning*&: Because the system filter runs just once, variables that are
32476 specific to individual recipient addresses, such as &$local_part$& and
32477 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
32478 you want to run a centrally-specified filter for each recipient address
32479 independently, you can do so by setting up a suitable &(redirect)& router, as
32480 described in section &<<SECTperaddfil>>& below.
32483 .section "Specifying a system filter" "SECID212"
32484 .cindex "uid (user id)" "system filter"
32485 .cindex "gid (group id)" "system filter"
32486 The name of the file that contains the system filter must be specified by
32487 setting &%system_filter%&. If you want the filter to run under a uid and gid
32488 other than root, you must also set &%system_filter_user%& and
32489 &%system_filter_group%& as appropriate. For example:
32491 system_filter = /etc/mail/exim.filter
32492 system_filter_user = exim
32494 If a system filter generates any deliveries directly to files or pipes (via the
32495 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
32496 specified by setting &%system_filter_file_transport%& and
32497 &%system_filter_pipe_transport%&, respectively. Similarly,
32498 &%system_filter_reply_transport%& must be set to handle any messages generated
32499 by the &%reply%& command.
32502 .section "Testing a system filter" "SECID213"
32503 You can run simple tests of a system filter in the same way as for a user
32504 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
32505 are permitted only in system filters are recognized.
32507 If you want to test the combined effect of a system filter and a user filter,
32508 you can use both &%-bF%& and &%-bf%& on the same command line.
32512 .section "Contents of a system filter" "SECID214"
32513 The language used to specify system filters is the same as for users' filter
32514 files. It is described in the separate end-user document &'Exim's interface to
32515 mail filtering'&. However, there are some additional features that are
32516 available only in system filters; these are described in subsequent sections.
32517 If they are encountered in a user's filter file or when testing with &%-bf%&,
32520 .cindex "frozen messages" "manual thaw; testing in filter"
32521 There are two special conditions which, though available in users' filter
32522 files, are designed for use in system filters. The condition &%first_delivery%&
32523 is true only for the first attempt at delivering a message, and
32524 &%manually_thawed%& is true only if the message has been frozen, and
32525 subsequently thawed by an admin user. An explicit forced delivery counts as a
32526 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
32528 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
32529 specify an &"unseen"& (non-significant) delivery, and that delivery does not
32530 succeed, it will not be tried again.
32531 If you want Exim to retry an unseen delivery until it succeeds, you should
32532 arrange to set it up every time the filter runs.
32534 When a system filter finishes running, the values of the variables &$n0$& &--
32535 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
32536 users' filter files. Thus a system filter can, for example, set up &"scores"&
32537 to which users' filter files can refer.
32541 .section "Additional variable for system filters" "SECID215"
32542 .vindex "&$recipients$&"
32543 The expansion variable &$recipients$&, containing a list of all the recipients
32544 of the message (separated by commas and white space), is available in system
32545 filters. It is not available in users' filters for privacy reasons.
32549 .section "Defer, freeze, and fail commands for system filters" "SECID216"
32550 .cindex "freezing messages"
32551 .cindex "message" "freezing"
32552 .cindex "message" "forced failure"
32553 .cindex "&%fail%&" "in system filter"
32554 .cindex "&%freeze%& in system filter"
32555 .cindex "&%defer%& in system filter"
32556 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
32557 always available in system filters, but are not normally enabled in users'
32558 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
32559 for the &(redirect)& router.) These commands can optionally be followed by the
32560 word &%text%& and a string containing an error message, for example:
32562 fail text "this message looks like spam to me"
32564 The keyword &%text%& is optional if the next character is a double quote.
32566 The &%defer%& command defers delivery of the original recipients of the
32567 message. The &%fail%& command causes all the original recipients to be failed,
32568 and a bounce message to be created. The &%freeze%& command suspends all
32569 delivery attempts for the original recipients. In all cases, any new deliveries
32570 that are specified by the filter are attempted as normal after the filter has
32573 The &%freeze%& command is ignored if the message has been manually unfrozen and
32574 not manually frozen since. This means that automatic freezing by a system
32575 filter can be used as a way of checking out suspicious messages. If a message
32576 is found to be all right, manually unfreezing it allows it to be delivered.
32578 .cindex "log" "&%fail%& command log line"
32579 .cindex "&%fail%&" "log line; reducing"
32580 The text given with a fail command is used as part of the bounce message as
32581 well as being written to the log. If the message is quite long, this can fill
32582 up a lot of log space when such failures are common. To reduce the size of the
32583 log message, Exim interprets the text in a special way if it starts with the
32584 two characters &`<<`& and contains &`>>`& later. The text between these two
32585 strings is written to the log, and the rest of the text is used in the bounce
32586 message. For example:
32588 fail "<<filter test 1>>Your message is rejected \
32589 because it contains attachments that we are \
32590 not prepared to receive."
32593 .cindex "loop" "caused by &%fail%&"
32594 Take great care with the &%fail%& command when basing the decision to fail on
32595 the contents of the message, because the bounce message will of course include
32596 the contents of the original message and will therefore trigger the &%fail%&
32597 command again (causing a mail loop) unless steps are taken to prevent this.
32598 Testing the &%error_message%& condition is one way to prevent this. You could
32601 if $message_body contains "this is spam" and not error_message
32602 then fail text "spam is not wanted here" endif
32604 though of course that might let through unwanted bounce messages. The
32605 alternative is clever checking of the body and/or headers to detect bounces
32606 generated by the filter.
32608 The interpretation of a system filter file ceases after a
32610 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
32611 set up earlier in the filter file are honoured, so you can use a sequence such
32617 to send a specified message when the system filter is freezing (or deferring or
32618 failing) a message. The normal deliveries for the message do not, of course,
32623 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
32624 .cindex "header lines" "adding; in system filter"
32625 .cindex "header lines" "removing; in system filter"
32626 .cindex "filter" "header lines; adding/removing"
32627 Two filter commands that are available only in system filters are:
32629 headers add <string>
32630 headers remove <string>
32632 The argument for the &%headers add%& is a string that is expanded and then
32633 added to the end of the message's headers. It is the responsibility of the
32634 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
32635 space is ignored, and if the string is otherwise empty, or if the expansion is
32636 forced to fail, the command has no effect.
32638 You can use &"\n"& within the string, followed by white space, to specify
32639 continued header lines. More than one header may be added in one command by
32640 including &"\n"& within the string without any following white space. For
32643 headers add "X-header-1: ....\n \
32644 continuation of X-header-1 ...\n\
32647 Note that the header line continuation white space after the first newline must
32648 be placed before the backslash that continues the input string, because white
32649 space after input continuations is ignored.
32651 The argument for &%headers remove%& is a colon-separated list of header names.
32652 This command applies only to those headers that are stored with the message;
32653 those that are added at delivery time (such as &'Envelope-To:'& and
32654 &'Return-Path:'&) cannot be removed by this means. If there is more than one
32655 header with the same name, they are all removed.
32657 The &%headers%& command in a system filter makes an immediate change to the set
32658 of header lines that was received with the message (with possible additions
32659 from ACL processing). Subsequent commands in the system filter operate on the
32660 modified set, which also forms the basis for subsequent message delivery.
32661 Unless further modified during routing or transporting, this set of headers is
32662 used for all recipients of the message.
32664 During routing and transporting, the variables that refer to the contents of
32665 header lines refer only to those lines that are in this set. Thus, header lines
32666 that are added by a system filter are visible to users' filter files and to all
32667 routers and transports. This contrasts with the manipulation of header lines by
32668 routers and transports, which is not immediate, but which instead is saved up
32669 until the message is actually being written (see section
32670 &<<SECTheadersaddrem>>&).
32672 If the message is not delivered at the first attempt, header lines that were
32673 added by the system filter are stored with the message, and so are still
32674 present at the next delivery attempt. Header lines that were removed are still
32675 present, but marked &"deleted"& so that they are not transported with the
32676 message. For this reason, it is usual to make the &%headers%& command
32677 conditional on &%first_delivery%& so that the set of header lines is not
32678 modified more than once.
32680 Because header modification in a system filter acts immediately, you have to
32681 use an indirect approach if you want to modify the contents of a header line.
32684 headers add "Old-Subject: $h_subject:"
32685 headers remove "Subject"
32686 headers add "Subject: new subject (was: $h_old-subject:)"
32687 headers remove "Old-Subject"
32692 .section "Setting an errors address in a system filter" "SECID217"
32693 .cindex "envelope sender"
32694 In a system filter, if a &%deliver%& command is followed by
32696 errors_to <some address>
32698 in order to change the envelope sender (and hence the error reporting) for that
32699 delivery, any address may be specified. (In a user filter, only the current
32700 user's address can be set.) For example, if some mail is being monitored, you
32703 unseen deliver monitor@spying.example errors_to root@local.example
32705 to take a copy which would not be sent back to the normal error reporting
32706 address if its delivery failed.
32710 .section "Per-address filtering" "SECTperaddfil"
32711 .vindex "&$domain$&"
32712 .vindex "&$local_part$&"
32713 In contrast to the system filter, which is run just once per message for each
32714 delivery attempt, it is also possible to set up a system-wide filtering
32715 operation that runs once for each recipient address. In this case, variables
32716 such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
32717 filter file could be made dependent on them. This is an example of a router
32718 which implements such a filter:
32723 domains = +local_domains
32724 file = /central/filters/$local_part
32729 The filter is run in a separate process under its own uid. Therefore, either
32730 &%check_local_user%& must be set (as above), in which case the filter is run as
32731 the local user, or the &%user%& option must be used to specify which user to
32732 use. If both are set, &%user%& overrides.
32734 Care should be taken to ensure that none of the commands in the filter file
32735 specify a significant delivery if the message is to go on to be delivered to
32736 its intended recipient. The router will not then claim to have dealt with the
32737 address, so it will be passed on to subsequent routers to be delivered in the
32739 .ecindex IIDsysfil1
32740 .ecindex IIDsysfil2
32741 .ecindex IIDsysfil3
32748 . ////////////////////////////////////////////////////////////////////////////
32749 . ////////////////////////////////////////////////////////////////////////////
32751 .chapter "Message processing" "CHAPmsgproc"
32752 .scindex IIDmesproc "message" "general processing"
32753 Exim performs various transformations on the sender and recipient addresses of
32754 all messages that it handles, and also on the messages' header lines. Some of
32755 these are optional and configurable, while others always take place. All of
32756 this processing, except rewriting as a result of routing, and the addition or
32757 removal of header lines while delivering, happens when a message is received,
32758 before it is placed on Exim's queue.
32760 Some of the automatic processing takes place by default only for
32761 &"locally-originated"& messages. This adjective is used to describe messages
32762 that are not received over TCP/IP, but instead are passed to an Exim process on
32763 its standard input. This includes the interactive &"local SMTP"& case that is
32764 set up by the &%-bs%& command line option.
32766 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
32767 or ::1) are not considered to be locally-originated. Exim does not treat the
32768 loopback interface specially in any way.
32770 If you want the loopback interface to be treated specially, you must ensure
32771 that there are appropriate entries in your ACLs.
32776 .section "Submission mode for non-local messages" "SECTsubmodnon"
32777 .cindex "message" "submission"
32778 .cindex "submission mode"
32779 Processing that happens automatically for locally-originated messages (unless
32780 &%suppress_local_fixups%& is set) can also be requested for messages that are
32781 received over TCP/IP. The term &"submission mode"& is used to describe this
32782 state. Submission mode is set by the modifier
32784 control = submission
32786 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
32787 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
32788 a local submission, and is normally used when the source of the message is
32789 known to be an MUA running on a client host (as opposed to an MTA). For
32790 example, to set submission mode for messages originating on the IPv4 loopback
32791 interface, you could include the following in the MAIL ACL:
32793 warn hosts = 127.0.0.1
32794 control = submission
32796 .cindex "&%sender_retain%& submission option"
32797 There are some options that can be used when setting submission mode. A slash
32798 is used to separate options. For example:
32800 control = submission/sender_retain
32802 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
32803 true and &%local_from_check%& false for the current incoming message. The first
32804 of these allows an existing &'Sender:'& header in the message to remain, and
32805 the second suppresses the check to ensure that &'From:'& matches the
32806 authenticated sender. With this setting, Exim still fixes up messages by adding
32807 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
32808 attempt to check sender authenticity in header lines.
32810 When &%sender_retain%& is not set, a submission mode setting may specify a
32811 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
32814 control = submission/domain=some.domain
32816 The domain may be empty. How this value is used is described in sections
32817 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
32818 that allows you to specify the user's full name for inclusion in a created
32819 &'Sender:'& or &'From:'& header line. For example:
32821 accept authenticated = *
32822 control = submission/domain=wonderland.example/\
32823 name=${lookup {$authenticated_id} \
32824 lsearch {/etc/exim/namelist}}
32826 Because the name may contain any characters, including slashes, the &%name%&
32827 option must be given last. The remainder of the string is used as the name. For
32828 the example above, if &_/etc/exim/namelist_& contains:
32830 bigegg: Humpty Dumpty
32832 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
32835 Sender: Humpty Dumpty <bigegg@wonderland.example>
32837 .cindex "return path" "in submission mode"
32838 By default, submission mode forces the return path to the same address as is
32839 used to create the &'Sender:'& header. However, if &%sender_retain%& is
32840 specified, the return path is also left unchanged.
32842 &*Note*&: The changes caused by submission mode take effect after the predata
32843 ACL. This means that any sender checks performed before the fix-ups use the
32844 untrusted sender address specified by the user, not the trusted sender address
32845 specified by submission mode. Although this might be slightly unexpected, it
32846 does mean that you can configure ACL checks to spot that a user is trying to
32847 spoof another's address.
32849 .section "Line endings" "SECTlineendings"
32850 .cindex "line endings"
32851 .cindex "carriage return"
32853 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
32854 linefeed) is the line ending for messages transmitted over the Internet using
32855 SMTP over TCP/IP. However, within individual operating systems, different
32856 conventions are used. For example, Unix-like systems use just LF, but others
32857 use CRLF or just CR.
32859 Exim was designed for Unix-like systems, and internally, it stores messages
32860 using the system's convention of a single LF as a line terminator. When
32861 receiving a message, all line endings are translated to this standard format.
32862 Originally, it was thought that programs that passed messages directly to an
32863 MTA within an operating system would use that system's convention. Experience
32864 has shown that this is not the case; for example, there are Unix applications
32865 that use CRLF in this circumstance. For this reason, and for compatibility with
32866 other MTAs, the way Exim handles line endings for all messages is now as
32870 LF not preceded by CR is treated as a line ending.
32872 CR is treated as a line ending; if it is immediately followed by LF, the LF
32875 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
32876 nor a local message in the state where a line containing only a dot is a
32879 If a bare CR is encountered within a header line, an extra space is added after
32880 the line terminator so as not to end the header line. The reasoning behind this
32881 is that bare CRs in header lines are most likely either to be mistakes, or
32882 people trying to play silly games.
32884 If the first header line received in a message ends with CRLF, a subsequent
32885 bare LF in a header line is treated in the same way as a bare CR in a header
32893 .section "Unqualified addresses" "SECID218"
32894 .cindex "unqualified addresses"
32895 .cindex "address" "qualification"
32896 By default, Exim expects every envelope address it receives from an external
32897 host to be fully qualified. Unqualified addresses cause negative responses to
32898 SMTP commands. However, because SMTP is used as a means of transporting
32899 messages from MUAs running on personal workstations, there is sometimes a
32900 requirement to accept unqualified addresses from specific hosts or IP networks.
32902 Exim has two options that separately control which hosts may send unqualified
32903 sender or recipient addresses in SMTP commands, namely
32904 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
32905 cases, if an unqualified address is accepted, it is qualified by adding the
32906 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
32908 .oindex "&%qualify_domain%&"
32909 .oindex "&%qualify_recipient%&"
32910 Unqualified addresses in header lines are automatically qualified for messages
32911 that are locally originated, unless the &%-bnq%& option is given on the command
32912 line. For messages received over SMTP, unqualified addresses in header lines
32913 are qualified only if unqualified addresses are permitted in SMTP commands. In
32914 other words, such qualification is also controlled by
32915 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
32920 .section "The UUCP From line" "SECID219"
32921 .cindex "&""From""& line"
32922 .cindex "UUCP" "&""From""& line"
32923 .cindex "sender" "address"
32924 .oindex "&%uucp_from_pattern%&"
32925 .oindex "&%uucp_from_sender%&"
32926 .cindex "envelope sender"
32927 .cindex "Sendmail compatibility" "&""From""& line"
32928 Messages that have come from UUCP (and some other applications) often begin
32929 with a line containing the envelope sender and a timestamp, following the word
32930 &"From"&. Examples of two common formats are:
32932 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
32933 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
32935 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
32936 Exim recognizes such lines at the start of messages that are submitted to it
32937 via the command line (that is, on the standard input). It does not recognize
32938 such lines in incoming SMTP messages, unless the sending host matches
32939 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
32940 and &%ignore_fromline_local%& is set. The recognition is controlled by a
32941 regular expression that is defined by the &%uucp_from_pattern%& option, whose
32942 default value matches the two common cases shown above and puts the address
32943 that follows &"From"& into &$1$&.
32945 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
32946 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
32947 a trusted user, the message's sender address is constructed by expanding the
32948 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
32949 then parsed as an RFC 2822 address. If there is no domain, the local part is
32950 qualified with &%qualify_domain%& unless it is the empty string. However, if
32951 the command line &%-f%& option is used, it overrides the &"From"& line.
32953 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
32954 sender address is not changed. This is also the case for incoming SMTP messages
32955 that are permitted to contain &"From"& lines.
32957 Only one &"From"& line is recognized. If there is more than one, the second is
32958 treated as a data line that starts the body of the message, as it is not valid
32959 as a header line. This also happens if a &"From"& line is present in an
32960 incoming SMTP message from a source that is not permitted to send them.
32964 .section "Resent- header lines" "SECID220"
32965 .cindex "&%Resent-%& header lines"
32966 RFC 2822 makes provision for sets of header lines starting with the string
32967 &`Resent-`& to be added to a message when it is resent by the original
32968 recipient to somebody else. These headers are &'Resent-Date:'&,
32969 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
32970 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
32973 &'Resent fields are strictly informational. They MUST NOT be used in the normal
32974 processing of replies or other such automatic actions on messages.'&
32977 This leaves things a bit vague as far as other processing actions such as
32978 address rewriting are concerned. Exim treats &%Resent-%& header lines as
32982 A &'Resent-From:'& line that just contains the login id of the submitting user
32983 is automatically rewritten in the same way as &'From:'& (see below).
32985 If there's a rewriting rule for a particular header line, it is also applied to
32986 &%Resent-%& header lines of the same type. For example, a rule that rewrites
32987 &'From:'& also rewrites &'Resent-From:'&.
32989 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
32992 For a locally-submitted message,
32993 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
32994 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
32995 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
32996 included in log lines in this case.
32998 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
32999 &%Resent-%& header lines are present.
33005 .section "The Auto-Submitted: header line" "SECID221"
33006 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
33007 includes the header line:
33009 Auto-Submitted: auto-replied
33012 .section "The Bcc: header line" "SECID222"
33013 .cindex "&'Bcc:'& header line"
33014 If Exim is called with the &%-t%& option, to take recipient addresses from a
33015 message's header, it removes any &'Bcc:'& header line that may exist (after
33016 extracting its addresses). If &%-t%& is not present on the command line, any
33017 existing &'Bcc:'& is not removed.
33020 .section "The Date: header line" "SECID223"
33021 .cindex "&'Date:'& header line"
33022 If a locally-generated or submission-mode message has no &'Date:'& header line,
33023 Exim adds one, using the current date and time, unless the
33024 &%suppress_local_fixups%& control has been specified.
33026 .section "The Delivery-date: header line" "SECID224"
33027 .cindex "&'Delivery-date:'& header line"
33028 .oindex "&%delivery_date_remove%&"
33029 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
33030 set. Exim can be configured to add them to the final delivery of messages. (See
33031 the generic &%delivery_date_add%& transport option.) They should not be present
33032 in messages in transit. If the &%delivery_date_remove%& configuration option is
33033 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
33037 .section "The Envelope-to: header line" "SECID225"
33038 .cindex "&'Envelope-to:'& header line"
33039 .oindex "&%envelope_to_remove%&"
33040 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
33041 Exim can be configured to add them to the final delivery of messages. (See the
33042 generic &%envelope_to_add%& transport option.) They should not be present in
33043 messages in transit. If the &%envelope_to_remove%& configuration option is set
33044 (the default), Exim removes &'Envelope-to:'& header lines from incoming
33048 .section "The From: header line" "SECTthefrohea"
33049 .cindex "&'From:'& header line"
33050 .cindex "Sendmail compatibility" "&""From""& line"
33051 .cindex "message" "submission"
33052 .cindex "submission mode"
33053 If a submission-mode message does not contain a &'From:'& header line, Exim
33054 adds one if either of the following conditions is true:
33057 The envelope sender address is not empty (that is, this is not a bounce
33058 message). The added header line copies the envelope sender address.
33060 .vindex "&$authenticated_id$&"
33061 The SMTP session is authenticated and &$authenticated_id$& is not empty.
33063 .vindex "&$qualify_domain$&"
33064 If no domain is specified by the submission control, the local part is
33065 &$authenticated_id$& and the domain is &$qualify_domain$&.
33067 If a non-empty domain is specified by the submission control, the local
33068 part is &$authenticated_id$&, and the domain is the specified domain.
33070 If an empty domain is specified by the submission control,
33071 &$authenticated_id$& is assumed to be the complete address.
33075 A non-empty envelope sender takes precedence.
33077 If a locally-generated incoming message does not contain a &'From:'& header
33078 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
33079 containing the sender's address. The calling user's login name and full name
33080 are used to construct the address, as described in section &<<SECTconstr>>&.
33081 They are obtained from the password data by calling &[getpwuid()]& (but see the
33082 &%unknown_login%& configuration option). The address is qualified with
33083 &%qualify_domain%&.
33085 For compatibility with Sendmail, if an incoming, non-SMTP message has a
33086 &'From:'& header line containing just the unqualified login name of the calling
33087 user, this is replaced by an address containing the user's login name and full
33088 name as described in section &<<SECTconstr>>&.
33091 .section "The Message-ID: header line" "SECID226"
33092 .cindex "&'Message-ID:'& header line"
33093 .cindex "message" "submission"
33094 .oindex "&%message_id_header_text%&"
33095 If a locally-generated or submission-mode incoming message does not contain a
33096 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
33097 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
33098 to the message. If there are any &'Resent-:'& headers in the message, it
33099 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
33100 message id, preceded by the letter E to ensure it starts with a letter, and
33101 followed by @ and the primary host name. Additional information can be included
33102 in this header line by setting the &%message_id_header_text%& and/or
33103 &%message_id_header_domain%& options.
33106 .section "The Received: header line" "SECID227"
33107 .cindex "&'Received:'& header line"
33108 A &'Received:'& header line is added at the start of every message. The
33109 contents are defined by the &%received_header_text%& configuration option, and
33110 Exim automatically adds a semicolon and a timestamp to the configured string.
33112 The &'Received:'& header is generated as soon as the message's header lines
33113 have been received. At this stage, the timestamp in the &'Received:'& header
33114 line is the time that the message started to be received. This is the value
33115 that is seen by the DATA ACL and by the &[local_scan()]& function.
33117 Once a message is accepted, the timestamp in the &'Received:'& header line is
33118 changed to the time of acceptance, which is (apart from a small delay while the
33119 -H spool file is written) the earliest time at which delivery could start.
33122 .section "The References: header line" "SECID228"
33123 .cindex "&'References:'& header line"
33124 Messages created by the &(autoreply)& transport include a &'References:'&
33125 header line. This is constructed according to the rules that are described in
33126 section 3.64 of RFC 2822 (which states that replies should contain such a
33127 header line), and section 3.14 of RFC 3834 (which states that automatic
33128 responses are not different in this respect). However, because some mail
33129 processing software does not cope well with very long header lines, no more
33130 than 12 message IDs are copied from the &'References:'& header line in the
33131 incoming message. If there are more than 12, the first one and then the final
33132 11 are copied, before adding the message ID of the incoming message.
33136 .section "The Return-path: header line" "SECID229"
33137 .cindex "&'Return-path:'& header line"
33138 .oindex "&%return_path_remove%&"
33139 &'Return-path:'& header lines are defined as something an MTA may insert when
33140 it does the final delivery of messages. (See the generic &%return_path_add%&
33141 transport option.) Therefore, they should not be present in messages in
33142 transit. If the &%return_path_remove%& configuration option is set (the
33143 default), Exim removes &'Return-path:'& header lines from incoming messages.
33147 .section "The Sender: header line" "SECTthesenhea"
33148 .cindex "&'Sender:'& header line"
33149 .cindex "message" "submission"
33150 For a locally-originated message from an untrusted user, Exim may remove an
33151 existing &'Sender:'& header line, and it may add a new one. You can modify
33152 these actions by setting the &%local_sender_retain%& option true, the
33153 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
33156 When a local message is received from an untrusted user and
33157 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
33158 control has not been set, a check is made to see if the address given in the
33159 &'From:'& header line is the correct (local) sender of the message. The address
33160 that is expected has the login name as the local part and the value of
33161 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
33162 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
33163 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
33164 line is added to the message.
33166 If you set &%local_from_check%& false, this checking does not occur. However,
33167 the removal of an existing &'Sender:'& line still happens, unless you also set
33168 &%local_sender_retain%& to be true. It is not possible to set both of these
33169 options true at the same time.
33171 .cindex "submission mode"
33172 By default, no processing of &'Sender:'& header lines is done for messages
33173 received over TCP/IP or for messages submitted by trusted users. However, when
33174 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
33175 not specified on the submission control, the following processing takes place:
33177 .vindex "&$authenticated_id$&"
33178 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
33179 authenticated, and &$authenticated_id$& is not empty, a sender address is
33180 created as follows:
33183 .vindex "&$qualify_domain$&"
33184 If no domain is specified by the submission control, the local part is
33185 &$authenticated_id$& and the domain is &$qualify_domain$&.
33187 If a non-empty domain is specified by the submission control, the local part
33188 is &$authenticated_id$&, and the domain is the specified domain.
33190 If an empty domain is specified by the submission control,
33191 &$authenticated_id$& is assumed to be the complete address.
33194 This address is compared with the address in the &'From:'& header line. If they
33195 are different, a &'Sender:'& header line containing the created address is
33196 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
33197 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
33199 .cindex "return path" "created from &'Sender:'&"
33200 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
33201 the message (the envelope sender address) is changed to be the same address,
33202 except in the case of submission mode when &%sender_retain%& is specified.
33206 .section "Adding and removing header lines in routers and transports" &&&
33207 "SECTheadersaddrem"
33208 .cindex "header lines" "adding; in router or transport"
33209 .cindex "header lines" "removing; in router or transport"
33210 When a message is delivered, the addition and removal of header lines can be
33211 specified in a system filter, or on any of the routers and transports that
33212 process the message. Section &<<SECTaddremheasys>>& contains details about
33213 modifying headers in a system filter. Header lines can also be added in an ACL
33214 as a message is received (see section &<<SECTaddheadacl>>&).
33216 In contrast to what happens in a system filter, header modifications that are
33217 specified on routers and transports apply only to the particular recipient
33218 addresses that are being processed by those routers and transports. These
33219 changes do not actually take place until a copy of the message is being
33220 transported. Therefore, they do not affect the basic set of header lines, and
33221 they do not affect the values of the variables that refer to header lines.
33223 &*Note*&: In particular, this means that any expansions in the configuration of
33224 the transport cannot refer to the modified header lines, because such
33225 expansions all occur before the message is actually transported.
33227 For both routers and transports, the argument of a &%headers_add%&
33228 option must be in the form of one or more RFC 2822 header lines, separated by
33229 newlines (coded as &"\n"&). For example:
33231 headers_add = X-added-header: added by $primary_hostname\n\
33232 X-added-second: another added header line
33234 Exim does not check the syntax of these added header lines.
33236 Multiple &%headers_add%& options for a single router or transport can be
33237 specified; the values will append to a single list of header lines.
33238 Each header-line is separately expanded.
33240 The argument of a &%headers_remove%& option must consist of a colon-separated
33241 list of header names. This is confusing, because header names themselves are
33242 often terminated by colons. In this case, the colons are the list separators,
33243 not part of the names. For example:
33245 headers_remove = return-receipt-to:acknowledge-to
33248 Multiple &%headers_remove%& options for a single router or transport can be
33249 specified; the arguments will append to a single header-names list.
33250 Each item is separately expanded.
33251 Note that colons in complex expansions which are used to
33252 form all or part of a &%headers_remove%& list
33253 will act as list separators.
33255 When &%headers_add%& or &%headers_remove%& is specified on a router,
33256 items are expanded at routing time,
33257 and then associated with all addresses that are
33258 accepted by that router, and also with any new addresses that it generates. If
33259 an address passes through several routers as a result of aliasing or
33260 forwarding, the changes are cumulative.
33262 .oindex "&%unseen%&"
33263 However, this does not apply to multiple routers that result from the use of
33264 the &%unseen%& option. Any header modifications that were specified by the
33265 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
33267 Addresses that end up with different &%headers_add%& or &%headers_remove%&
33268 settings cannot be delivered together in a batch, so a transport is always
33269 dealing with a set of addresses that have the same header-processing
33272 The transport starts by writing the original set of header lines that arrived
33273 with the message, possibly modified by the system filter. As it writes out
33274 these lines, it consults the list of header names that were attached to the
33275 recipient address(es) by &%headers_remove%& options in routers, and it also
33276 consults the transport's own &%headers_remove%& option. Header lines whose
33277 names are on either of these lists are not written out. If there are multiple
33278 instances of any listed header, they are all skipped.
33280 After the remaining original header lines have been written, new header
33281 lines that were specified by routers' &%headers_add%& options are written, in
33282 the order in which they were attached to the address. These are followed by any
33283 header lines specified by the transport's &%headers_add%& option.
33285 This way of handling header line modifications in routers and transports has
33286 the following consequences:
33289 The original set of header lines, possibly modified by the system filter,
33290 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
33291 to it, at all times.
33293 Header lines that are added by a router's
33294 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
33295 expansion syntax in subsequent routers or the transport.
33297 Conversely, header lines that are specified for removal by &%headers_remove%&
33298 in a router remain visible to subsequent routers and the transport.
33300 Headers added to an address by &%headers_add%& in a router cannot be removed by
33301 a later router or by a transport.
33303 An added header can refer to the contents of an original header that is to be
33304 removed, even it has the same name as the added header. For example:
33306 headers_remove = subject
33307 headers_add = Subject: new subject (was: $h_subject:)
33311 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
33312 for a &(redirect)& router that has the &%one_time%& option set.
33318 .section "Constructed addresses" "SECTconstr"
33319 .cindex "address" "constructed"
33320 .cindex "constructed address"
33321 When Exim constructs a sender address for a locally-generated message, it uses
33324 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
33328 Zaphod Beeblebrox <zaphod@end.univ.example>
33330 The user name is obtained from the &%-F%& command line option if set, or
33331 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
33332 &"gecos"& field from the password entry. If the &"gecos"& field contains an
33333 ampersand character, this is replaced by the login name with the first letter
33334 upper cased, as is conventional in a number of operating systems. See the
33335 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
33336 The &%unknown_username%& option can be used to specify user names in cases when
33337 there is no password file entry.
33340 In all cases, the user name is made to conform to RFC 2822 by quoting all or
33341 parts of it if necessary. In addition, if it contains any non-printing
33342 characters, it is encoded as described in RFC 2047, which defines a way of
33343 including non-ASCII characters in header lines. The value of the
33344 &%headers_charset%& option specifies the name of the encoding that is used (the
33345 characters are assumed to be in this encoding). The setting of
33346 &%print_topbitchars%& controls whether characters with the top bit set (that
33347 is, with codes greater than 127) count as printing characters or not.
33351 .section "Case of local parts" "SECID230"
33352 .cindex "case of local parts"
33353 .cindex "local part" "case of"
33354 RFC 2822 states that the case of letters in the local parts of addresses cannot
33355 be assumed to be non-significant. Exim preserves the case of local parts of
33356 addresses, but by default it uses a lower-cased form when it is routing,
33357 because on most Unix systems, usernames are in lower case and case-insensitive
33358 routing is required. However, any particular router can be made to use the
33359 original case for local parts by setting the &%caseful_local_part%& generic
33362 .cindex "mixed-case login names"
33363 If you must have mixed-case user names on your system, the best way to proceed,
33364 assuming you want case-independent handling of incoming email, is to set up
33365 your first router to convert incoming local parts in your domains to the
33366 correct case by means of a file lookup. For example:
33370 domains = +local_domains
33371 data = ${lookup{$local_part}cdb\
33372 {/etc/usercased.cdb}{$value}fail}\
33375 For this router, the local part is forced to lower case by the default action
33376 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
33377 up a new local part in the correct case. If you then set &%caseful_local_part%&
33378 on any subsequent routers which process your domains, they will operate on
33379 local parts with the correct case in a case-sensitive manner.
33383 .section "Dots in local parts" "SECID231"
33384 .cindex "dot" "in local part"
33385 .cindex "local part" "dots in"
33386 RFC 2822 forbids empty components in local parts. That is, an unquoted local
33387 part may not begin or end with a dot, nor have two consecutive dots in the
33388 middle. However, it seems that many MTAs do not enforce this, so Exim permits
33389 empty components for compatibility.
33393 .section "Rewriting addresses" "SECID232"
33394 .cindex "rewriting" "addresses"
33395 Rewriting of sender and recipient addresses, and addresses in headers, can
33396 happen automatically, or as the result of configuration options, as described
33397 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
33398 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
33400 Automatic rewriting includes qualification, as mentioned above. The other case
33401 in which it can happen is when an incomplete non-local domain is given. The
33402 routing process may cause this to be expanded into the full domain name. For
33403 example, a header such as
33407 might get rewritten as
33409 To: hare@teaparty.wonderland.fict.example
33411 Rewriting as a result of routing is the one kind of message processing that
33412 does not happen at input time, as it cannot be done until the address has
33415 Strictly, one should not do &'any'& deliveries of a message until all its
33416 addresses have been routed, in case any of the headers get changed as a
33417 result of routing. However, doing this in practice would hold up many
33418 deliveries for unreasonable amounts of time, just because one address could not
33419 immediately be routed. Exim therefore does not delay other deliveries when
33420 routing of one or more addresses is deferred.
33421 .ecindex IIDmesproc
33425 . ////////////////////////////////////////////////////////////////////////////
33426 . ////////////////////////////////////////////////////////////////////////////
33428 .chapter "SMTP processing" "CHAPSMTP"
33429 .scindex IIDsmtpproc1 "SMTP" "processing details"
33430 .scindex IIDsmtpproc2 "LMTP" "processing details"
33431 Exim supports a number of different ways of using the SMTP protocol, and its
33432 LMTP variant, which is an interactive protocol for transferring messages into a
33433 closed mail store application. This chapter contains details of how SMTP is
33434 processed. For incoming mail, the following are available:
33437 SMTP over TCP/IP (Exim daemon or &'inetd'&);
33439 SMTP over the standard input and output (the &%-bs%& option);
33441 Batched SMTP on the standard input (the &%-bS%& option).
33444 For mail delivery, the following are available:
33447 SMTP over TCP/IP (the &(smtp)& transport);
33449 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
33452 LMTP over a pipe to a process running in the local host (the &(lmtp)&
33455 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
33456 the &%use_bsmtp%& option set).
33459 &'Batched SMTP'& is the name for a process in which batches of messages are
33460 stored in or read from files (or pipes), in a format in which SMTP commands are
33461 used to contain the envelope information.
33465 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
33466 .cindex "SMTP" "outgoing over TCP/IP"
33467 .cindex "outgoing SMTP over TCP/IP"
33468 .cindex "LMTP" "over TCP/IP"
33469 .cindex "outgoing LMTP over TCP/IP"
33472 .cindex "SIZE option on MAIL command"
33473 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
33474 The &%protocol%& option selects which protocol is to be used, but the actual
33475 processing is the same in both cases.
33477 If, in response to its EHLO command, Exim is told that the SIZE
33478 parameter is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
33479 command. The value of <&'n'&> is the message size plus the value of the
33480 &%size_addition%& option (default 1024) to allow for additions to the message
33481 such as per-transport header lines, or changes made in a
33482 .cindex "transport" "filter"
33483 .cindex "filter" "transport filter"
33484 transport filter. If &%size_addition%& is set negative, the use of SIZE is
33487 If the remote server advertises support for PIPELINING, Exim uses the
33488 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
33489 required for the transaction.
33491 If the remote server advertises support for the STARTTLS command, and Exim
33492 was built to support TLS encryption, it tries to start a TLS session unless the
33493 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
33494 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
33495 is called for verification.
33497 If the remote server advertises support for the AUTH command, Exim scans
33498 the authenticators configuration for any suitable client settings, as described
33499 in chapter &<<CHAPSMTPAUTH>>&.
33501 .cindex "carriage return"
33503 Responses from the remote host are supposed to be terminated by CR followed by
33504 LF. However, there are known to be hosts that do not send CR characters, so in
33505 order to be able to interwork with such hosts, Exim treats LF on its own as a
33508 If a message contains a number of different addresses, all those with the same
33509 characteristics (for example, the same envelope sender) that resolve to the
33510 same set of hosts, in the same order, are sent in a single SMTP transaction,
33511 even if they are for different domains, unless there are more than the setting
33512 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
33513 they are split into groups containing no more than &%max_rcpt%&s addresses
33514 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
33515 in parallel sessions. The order of hosts with identical MX values is not
33516 significant when checking whether addresses can be batched in this way.
33518 When the &(smtp)& transport suffers a temporary failure that is not
33519 message-related, Exim updates its transport-specific database, which contains
33520 records indexed by host name that remember which messages are waiting for each
33521 particular host. It also updates the retry database with new retry times.
33523 .cindex "hints database" "retry keys"
33524 Exim's retry hints are based on host name plus IP address, so if one address of
33525 a multi-homed host is broken, it will soon be skipped most of the time.
33526 See the next section for more detail about error handling.
33528 .cindex "SMTP" "passed connection"
33529 .cindex "SMTP" "batching over TCP/IP"
33530 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
33531 looks in the hints database for the transport to see if there are any queued
33532 messages waiting for the host to which it is connected. If it finds one, it
33533 creates a new Exim process using the &%-MC%& option (which can only be used by
33534 a process running as root or the Exim user) and passes the TCP/IP socket to it
33535 so that it can deliver another message using the same socket. The new process
33536 does only those deliveries that are routed to the connected host, and may in
33537 turn pass the socket on to a third process, and so on.
33539 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
33540 limit the number of messages sent down a single TCP/IP connection.
33542 .cindex "asterisk" "after IP address"
33543 The second and subsequent messages delivered down an existing connection are
33544 identified in the main log by the addition of an asterisk after the closing
33545 square bracket of the IP address.
33550 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
33551 .cindex "error" "in outgoing SMTP"
33552 .cindex "SMTP" "errors in outgoing"
33553 .cindex "host" "error"
33554 Three different kinds of error are recognized for outgoing SMTP: host errors,
33555 message errors, and recipient errors.
33558 .vitem "&*Host errors*&"
33559 A host error is not associated with a particular message or with a
33560 particular recipient of a message. The host errors are:
33563 Connection refused or timed out,
33565 Any error response code on connection,
33567 Any error response code to EHLO or HELO,
33569 Loss of connection at any time, except after &"."&,
33571 I/O errors at any time,
33573 Timeouts during the session, other than in response to MAIL, RCPT or
33574 the &"."& at the end of the data.
33577 For a host error, a permanent error response on connection, or in response to
33578 EHLO, causes all addresses routed to the host to be failed. Any other host
33579 error causes all addresses to be deferred, and retry data to be created for the
33580 host. It is not tried again, for any message, until its retry time arrives. If
33581 the current set of addresses are not all delivered in this run (to some
33582 alternative host), the message is added to the list of those waiting for this
33583 host, so if it is still undelivered when a subsequent successful delivery is
33584 made to the host, it will be sent down the same SMTP connection.
33586 .vitem "&*Message errors*&"
33587 .cindex "message" "error"
33588 A message error is associated with a particular message when sent to a
33589 particular host, but not with a particular recipient of the message. The
33590 message errors are:
33593 Any error response code to MAIL, DATA, or the &"."& that terminates
33596 Timeout after MAIL,
33598 Timeout or loss of connection after the &"."& that terminates the data. A
33599 timeout after the DATA command itself is treated as a host error, as is loss of
33600 connection at any other time.
33603 For a message error, a permanent error response (5&'xx'&) causes all addresses
33604 to be failed, and a delivery error report to be returned to the sender. A
33605 temporary error response (4&'xx'&), or one of the timeouts, causes all
33606 addresses to be deferred. Retry data is not created for the host, but instead,
33607 a retry record for the combination of host plus message id is created. The
33608 message is not added to the list of those waiting for this host. This ensures
33609 that the failing message will not be sent to this host again until the retry
33610 time arrives. However, other messages that are routed to the host are not
33611 affected, so if it is some property of the message that is causing the error,
33612 it will not stop the delivery of other mail.
33614 If the remote host specified support for the SIZE parameter in its response
33615 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
33616 over-large message will cause a message error because the error arrives as a
33619 .vitem "&*Recipient errors*&"
33620 .cindex "recipient" "error"
33621 A recipient error is associated with a particular recipient of a message. The
33622 recipient errors are:
33625 Any error response to RCPT,
33627 Timeout after RCPT.
33630 For a recipient error, a permanent error response (5&'xx'&) causes the
33631 recipient address to be failed, and a bounce message to be returned to the
33632 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
33633 address to be deferred, and routing retry data to be created for it. This is
33634 used to delay processing of the address in subsequent queue runs, until its
33635 routing retry time arrives. This applies to all messages, but because it
33636 operates only in queue runs, one attempt will be made to deliver a new message
33637 to the failing address before the delay starts to operate. This ensures that,
33638 if the failure is really related to the message rather than the recipient
33639 (&"message too big for this recipient"& is a possible example), other messages
33640 have a chance of getting delivered. If a delivery to the address does succeed,
33641 the retry information gets cleared, so all stuck messages get tried again, and
33642 the retry clock is reset.
33644 The message is not added to the list of those waiting for this host. Use of the
33645 host for other messages is unaffected, and except in the case of a timeout,
33646 other recipients are processed independently, and may be successfully delivered
33647 in the current SMTP session. After a timeout it is of course impossible to
33648 proceed with the session, so all addresses get deferred. However, those other
33649 than the one that failed do not suffer any subsequent retry delays. Therefore,
33650 if one recipient is causing trouble, the others have a chance of getting
33651 through when a subsequent delivery attempt occurs before the failing
33652 recipient's retry time.
33655 In all cases, if there are other hosts (or IP addresses) available for the
33656 current set of addresses (for example, from multiple MX records), they are
33657 tried in this run for any undelivered addresses, subject of course to their
33658 own retry data. In other words, recipient error retry data does not take effect
33659 until the next delivery attempt.
33661 Some hosts have been observed to give temporary error responses to every
33662 MAIL command at certain times (&"insufficient space"& has been seen). It
33663 would be nice if such circumstances could be recognized, and defer data for the
33664 host itself created, but this is not possible within the current Exim design.
33665 What actually happens is that retry data for every (host, message) combination
33668 The reason that timeouts after MAIL and RCPT are treated specially is that
33669 these can sometimes arise as a result of the remote host's verification
33670 procedures. Exim makes this assumption, and treats them as if a temporary error
33671 response had been received. A timeout after &"."& is treated specially because
33672 it is known that some broken implementations fail to recognize the end of the
33673 message if the last character of the last line is a binary zero. Thus, it is
33674 helpful to treat this case as a message error.
33676 Timeouts at other times are treated as host errors, assuming a problem with the
33677 host, or the connection to it. If a timeout after MAIL, RCPT,
33678 or &"."& is really a connection problem, the assumption is that at the next try
33679 the timeout is likely to occur at some other point in the dialogue, causing it
33680 then to be treated as a host error.
33682 There is experimental evidence that some MTAs drop the connection after the
33683 terminating &"."& if they do not like the contents of the message for some
33684 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
33685 should be given. That is why Exim treats this case as a message rather than a
33686 host error, in order not to delay other messages to the same host.
33691 .section "Incoming SMTP messages over TCP/IP" "SECID233"
33692 .cindex "SMTP" "incoming over TCP/IP"
33693 .cindex "incoming SMTP over TCP/IP"
33696 Incoming SMTP messages can be accepted in one of two ways: by running a
33697 listening daemon, or by using &'inetd'&. In the latter case, the entry in
33698 &_/etc/inetd.conf_& should be like this:
33700 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
33702 Exim distinguishes between this case and the case of a locally running user
33703 agent using the &%-bs%& option by checking whether or not the standard input is
33704 a socket. When it is, either the port must be privileged (less than 1024), or
33705 the caller must be root or the Exim user. If any other user passes a socket
33706 with an unprivileged port number, Exim prints a message on the standard error
33707 stream and exits with an error code.
33709 By default, Exim does not make a log entry when a remote host connects or
33710 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
33711 unexpected. It can be made to write such log entries by setting the
33712 &%smtp_connection%& log selector.
33714 .cindex "carriage return"
33716 Commands from the remote host are supposed to be terminated by CR followed by
33717 LF. However, there are known to be hosts that do not send CR characters. In
33718 order to be able to interwork with such hosts, Exim treats LF on its own as a
33720 Furthermore, because common code is used for receiving messages from all
33721 sources, a CR on its own is also interpreted as a line terminator. However, the
33722 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
33724 .cindex "EHLO" "invalid data"
33725 .cindex "HELO" "invalid data"
33726 One area that sometimes gives rise to problems concerns the EHLO or
33727 HELO commands. Some clients send syntactically invalid versions of these
33728 commands, which Exim rejects by default. (This is nothing to do with verifying
33729 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
33730 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
33731 match the broken hosts that send invalid commands.
33733 .cindex "SIZE option on MAIL command"
33734 .cindex "MAIL" "SIZE option"
33735 The amount of disk space available is checked whenever SIZE is received on
33736 a MAIL command, independently of whether &%message_size_limit%& or
33737 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
33738 false. A temporary error is given if there is not enough space. If
33739 &%check_spool_space%& is set, the check is for that amount of space plus the
33740 value given with SIZE, that is, it checks that the addition of the incoming
33741 message will not reduce the space below the threshold.
33743 When a message is successfully received, Exim includes the local message id in
33744 its response to the final &"."& that terminates the data. If the remote host
33745 logs this text it can help with tracing what has happened to a message.
33747 The Exim daemon can limit the number of simultaneous incoming connections it is
33748 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
33749 number of simultaneous incoming connections from a single remote host (see the
33750 &%smtp_accept_max_per_host%& option). Additional connection attempts are
33751 rejected using the SMTP temporary error code 421.
33753 The Exim daemon does not rely on the SIGCHLD signal to detect when a
33754 subprocess has finished, as this can get lost at busy times. Instead, it looks
33755 for completed subprocesses every time it wakes up. Provided there are other
33756 things happening (new incoming calls, starts of queue runs), completed
33757 processes will be noticed and tidied away. On very quiet systems you may
33758 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
33759 it will be noticed when the daemon next wakes up.
33761 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
33762 and can also be set up to reject SMTP calls from non-reserved hosts at times of
33763 high system load &-- for details see the &%smtp_accept_reserve%&,
33764 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
33765 applies in both the daemon and &'inetd'& cases.
33767 Exim normally starts a delivery process for each message received, though this
33768 can be varied by means of the &%-odq%& command line option and the
33769 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
33770 number of simultaneously running delivery processes started in this way from
33771 SMTP input can be limited by the &%smtp_accept_queue%& and
33772 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
33773 subsequently received messages are just put on the input queue without starting
33774 a delivery process.
33776 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
33777 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
33778 started up from the &'inetd'& daemon, because in that case each connection is
33779 handled by an entirely independent Exim process. Control by load average is,
33780 however, available with &'inetd'&.
33782 Exim can be configured to verify addresses in incoming SMTP commands as they
33783 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
33784 to rewrite addresses at this time &-- before any syntax checking is done. See
33785 section &<<SECTrewriteS>>&.
33787 Exim can also be configured to limit the rate at which a client host submits
33788 MAIL and RCPT commands in a single SMTP session. See the
33789 &%smtp_ratelimit_hosts%& option.
33793 .section "Unrecognized SMTP commands" "SECID234"
33794 .cindex "SMTP" "unrecognized commands"
33795 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
33796 commands during a single SMTP connection, it drops the connection after sending
33797 the error response to the last command. The default value for
33798 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
33799 abuse that subvert web servers into making connections to SMTP ports; in these
33800 circumstances, a number of non-SMTP lines are sent first.
33803 .section "Syntax and protocol errors in SMTP commands" "SECID235"
33804 .cindex "SMTP" "syntax errors"
33805 .cindex "SMTP" "protocol errors"
33806 A syntax error is detected if an SMTP command is recognized, but there is
33807 something syntactically wrong with its data, for example, a malformed email
33808 address in a RCPT command. Protocol errors include invalid command
33809 sequencing such as RCPT before MAIL. If Exim receives more than
33810 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
33811 drops the connection after sending the error response to the last command. The
33812 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
33813 broken clients that loop sending bad commands (yes, it has been seen).
33817 .section "Use of non-mail SMTP commands" "SECID236"
33818 .cindex "SMTP" "non-mail commands"
33819 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
33820 DATA. Exim counts such commands, and drops the connection if there are too
33821 many of them in a single SMTP session. This action catches some
33822 denial-of-service attempts and things like repeated failing AUTHs, or a mad
33823 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
33824 defines what &"too many"& means. Its default value is 10.
33826 When a new message is expected, one occurrence of RSET is not counted. This
33827 allows a client to send one RSET between messages (this is not necessary,
33828 but some clients do it). Exim also allows one uncounted occurrence of HELO
33829 or EHLO, and one occurrence of STARTTLS between messages. After
33830 starting up a TLS session, another EHLO is expected, and so it too is not
33833 The first occurrence of AUTH in a connection, or immediately following
33834 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
33835 RCPT, DATA, and QUIT are counted.
33837 You can control which hosts are subject to the limit set by
33838 &%smtp_accept_max_nonmail%& by setting
33839 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
33840 the limit apply to all hosts. This option means that you can exclude any
33841 specific badly-behaved hosts that you have to live with.
33846 .section "The VRFY and EXPN commands" "SECID237"
33847 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
33848 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
33849 appropriate) in order to decide whether the command should be accepted or not.
33850 If no ACL is defined, the command is rejected.
33852 .cindex "VRFY" "processing"
33853 When VRFY is accepted, it runs exactly the same code as when Exim is
33854 called with the &%-bv%& option.
33856 .cindex "EXPN" "processing"
33857 When EXPN is accepted, a single-level expansion of the address is done.
33858 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
33859 than a verification (the &%-bv%& option). If an unqualified local part is given
33860 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
33861 of VRFY and EXPN commands are logged on the main and reject logs, and
33862 VRFY verification failures are logged on the main log for consistency with
33867 .section "The ETRN command" "SECTETRN"
33868 .cindex "ETRN" "processing"
33869 RFC 1985 describes an SMTP command called ETRN that is designed to
33870 overcome the security problems of the TURN command (which has fallen into
33871 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
33872 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
33873 should be accepted or not. If no ACL is defined, the command is rejected.
33875 The ETRN command is concerned with &"releasing"& messages that are awaiting
33876 delivery to certain hosts. As Exim does not organize its message queue by host,
33877 the only form of ETRN that is supported by default is the one where the
33878 text starts with the &"#"& prefix, in which case the remainder of the text is
33879 specific to the SMTP server. A valid ETRN command causes a run of Exim with
33880 the &%-R%& option to happen, with the remainder of the ETRN text as its
33881 argument. For example,
33889 which causes a delivery attempt on all messages with undelivered addresses
33890 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
33891 default), Exim prevents the simultaneous execution of more than one queue run
33892 for the same argument string as a result of an ETRN command. This stops
33893 a misbehaving client from starting more than one queue runner at once.
33895 .cindex "hints database" "ETRN serialization"
33896 Exim implements the serialization by means of a hints database in which a
33897 record is written whenever a process is started by ETRN, and deleted when
33898 the process completes. However, Exim does not keep the SMTP session waiting for
33899 the ETRN process to complete. Once ETRN is accepted, the client is sent
33900 a &"success"& return code. Obviously there is scope for hints records to get
33901 left lying around if there is a system or program crash. To guard against this,
33902 Exim ignores any records that are more than six hours old.
33904 .oindex "&%smtp_etrn_command%&"
33905 For more control over what ETRN does, the &%smtp_etrn_command%& option can
33906 used. This specifies a command that is run whenever ETRN is received,
33907 whatever the form of its argument. For
33910 smtp_etrn_command = /etc/etrn_command $domain \
33911 $sender_host_address
33913 .vindex "&$domain$&"
33914 The string is split up into arguments which are independently expanded. The
33915 expansion variable &$domain$& is set to the argument of the ETRN command,
33916 and no syntax checking is done on the contents of this argument. Exim does not
33917 wait for the command to complete, so its status code is not checked. Exim runs
33918 under its own uid and gid when receiving incoming SMTP, so it is not possible
33919 for it to change them before running the command.
33923 .section "Incoming local SMTP" "SECID238"
33924 .cindex "SMTP" "local incoming"
33925 Some user agents use SMTP to pass messages to their local MTA using the
33926 standard input and output, as opposed to passing the envelope on the command
33927 line and writing the message to the standard input. This is supported by the
33928 &%-bs%& option. This form of SMTP is handled in the same way as incoming
33929 messages over TCP/IP (including the use of ACLs), except that the envelope
33930 sender given in a MAIL command is ignored unless the caller is trusted. In
33931 an ACL you can detect this form of SMTP input by testing for an empty host
33932 identification. It is common to have this as the first line in the ACL that
33933 runs for RCPT commands:
33937 This accepts SMTP messages from local processes without doing any other tests.
33941 .section "Outgoing batched SMTP" "SECTbatchSMTP"
33942 .cindex "SMTP" "batched outgoing"
33943 .cindex "batched SMTP output"
33944 Both the &(appendfile)& and &(pipe)& transports can be used for handling
33945 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
33946 be output in BSMTP format. No SMTP responses are possible for this form of
33947 delivery. All it is doing is using SMTP commands as a way of transmitting the
33948 envelope along with the message.
33950 The message is written to the file or pipe preceded by the SMTP commands
33951 MAIL and RCPT, and followed by a line containing a single dot. Lines in
33952 the message that start with a dot have an extra dot added. The SMTP command
33953 HELO is not normally used. If it is required, the &%message_prefix%& option
33954 can be used to specify it.
33956 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
33957 one recipient address at a time by default. However, you can arrange for them
33958 to handle several addresses at once by setting the &%batch_max%& option. When
33959 this is done for BSMTP, messages may contain multiple RCPT commands. See
33960 chapter &<<CHAPbatching>>& for more details.
33963 When one or more addresses are routed to a BSMTP transport by a router that
33964 sets up a host list, the name of the first host on the list is available to the
33965 transport in the variable &$host$&. Here is an example of such a transport and
33970 driver = manualroute
33971 transport = smtp_appendfile
33972 route_list = domain.example batch.host.example
33976 driver = appendfile
33977 directory = /var/bsmtp/$host
33982 This causes messages addressed to &'domain.example'& to be written in BSMTP
33983 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
33984 message (unless there are more than 1000 recipients).
33988 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
33989 .cindex "SMTP" "batched incoming"
33990 .cindex "batched SMTP input"
33991 The &%-bS%& command line option causes Exim to accept one or more messages by
33992 reading SMTP on the standard input, but to generate no responses. If the caller
33993 is trusted, the senders in the MAIL commands are believed; otherwise the
33994 sender is always the caller of Exim. Unqualified senders and receivers are not
33995 rejected (there seems little point) but instead just get qualified. HELO
33996 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
33997 as NOOP; QUIT quits.
33999 Minimal policy checking is done for BSMTP input. Only the non-SMTP
34000 ACL is run in the same way as for non-SMTP local input.
34002 If an error is detected while reading a message, including a missing &"."& at
34003 the end, Exim gives up immediately. It writes details of the error to the
34004 standard output in a stylized way that the calling program should be able to
34005 make some use of automatically, for example:
34007 554 Unexpected end of file
34008 Transaction started in line 10
34009 Error detected in line 14
34011 It writes a more verbose version, for human consumption, to the standard error
34014 An error was detected while processing a file of BSMTP input.
34015 The error message was:
34017 501 '>' missing at end of address
34019 The SMTP transaction started in line 10.
34020 The error was detected in line 12.
34021 The SMTP command at fault was:
34023 rcpt to:<malformed@in.com.plete
34025 1 previous message was successfully processed.
34026 The rest of the batch was abandoned.
34028 The return code from Exim is zero only if there were no errors. It is 1 if some
34029 messages were accepted before an error was detected, and 2 if no messages were
34031 .ecindex IIDsmtpproc1
34032 .ecindex IIDsmtpproc2
34036 . ////////////////////////////////////////////////////////////////////////////
34037 . ////////////////////////////////////////////////////////////////////////////
34039 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
34040 "Customizing messages"
34041 When a message fails to be delivered, or remains on the queue for more than a
34042 configured amount of time, Exim sends a message to the original sender, or
34043 to an alternative configured address. The text of these messages is built into
34044 the code of Exim, but it is possible to change it, either by adding a single
34045 string, or by replacing each of the paragraphs by text supplied in a file.
34047 The &'From:'& and &'To:'& header lines are automatically generated; you can
34048 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
34049 option. Exim also adds the line
34051 Auto-Submitted: auto-generated
34053 to all warning and bounce messages,
34056 .section "Customizing bounce messages" "SECID239"
34057 .cindex "customizing" "bounce message"
34058 .cindex "bounce message" "customizing"
34059 If &%bounce_message_text%& is set, its contents are included in the default
34060 message immediately after &"This message was created automatically by mail
34061 delivery software."& The string is not expanded. It is not used if
34062 &%bounce_message_file%& is set.
34064 When &%bounce_message_file%& is set, it must point to a template file for
34065 constructing error messages. The file consists of a series of text items,
34066 separated by lines consisting of exactly four asterisks. If the file cannot be
34067 opened, default text is used and a message is written to the main and panic
34068 logs. If any text item in the file is empty, default text is used for that
34071 .vindex "&$bounce_recipient$&"
34072 .vindex "&$bounce_return_size_limit$&"
34073 Each item of text that is read from the file is expanded, and there are two
34074 expansion variables which can be of use here: &$bounce_recipient$& is set to
34075 the recipient of an error message while it is being created, and
34076 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
34077 option, rounded to a whole number.
34079 The items must appear in the file in the following order:
34082 The first item is included in the headers, and should include at least a
34083 &'Subject:'& header. Exim does not check the syntax of these headers.
34085 The second item forms the start of the error message. After it, Exim lists the
34086 failing addresses with their error messages.
34088 The third item is used to introduce any text from pipe transports that is to be
34089 returned to the sender. It is omitted if there is no such text.
34091 The fourth, fifth and sixth items will be ignored and may be empty.
34092 The fields exist for back-compatibility
34095 The default state (&%bounce_message_file%& unset) is equivalent to the
34096 following file, in which the sixth item is empty. The &'Subject:'& and some
34097 other lines have been split in order to fit them on the page:
34099 Subject: Mail delivery failed
34100 ${if eq{$sender_address}{$bounce_recipient}
34101 {: returning message to sender}}
34103 This message was created automatically by mail delivery software.
34105 A message ${if eq{$sender_address}{$bounce_recipient}
34106 {that you sent }{sent by
34110 }}could not be delivered to all of its recipients.
34111 This is a permanent error. The following address(es) failed:
34113 The following text was generated during the delivery attempt(s):
34115 ------ This is a copy of the message, including all the headers.
34118 ------ The body of the message is $message_size characters long;
34120 ------ $bounce_return_size_limit or so are included here.
34123 .section "Customizing warning messages" "SECTcustwarn"
34124 .cindex "customizing" "warning message"
34125 .cindex "warning of delay" "customizing the message"
34126 The option &%warn_message_file%& can be pointed at a template file for use when
34127 warnings about message delays are created. In this case there are only three
34131 The first item is included in the headers, and should include at least a
34132 &'Subject:'& header. Exim does not check the syntax of these headers.
34134 The second item forms the start of the warning message. After it, Exim lists
34135 the delayed addresses.
34137 The third item then ends the message.
34140 The default state is equivalent to the following file, except that some lines
34141 have been split here, in order to fit them on the page:
34143 Subject: Warning: message $message_exim_id delayed
34144 $warn_message_delay
34146 This message was created automatically by mail delivery software.
34148 A message ${if eq{$sender_address}{$warn_message_recipients}
34149 {that you sent }{sent by
34153 }}has not been delivered to all of its recipients after
34154 more than $warn_message_delay on the queue on $primary_hostname.
34156 The message identifier is: $message_exim_id
34157 The subject of the message is: $h_subject
34158 The date of the message is: $h_date
34160 The following address(es) have not yet been delivered:
34162 No action is required on your part. Delivery attempts will
34163 continue for some time, and this warning may be repeated at
34164 intervals if the message remains undelivered. Eventually the
34165 mail delivery software will give up, and when that happens,
34166 the message will be returned to you.
34168 .vindex "&$warn_message_delay$&"
34169 .vindex "&$warn_message_recipients$&"
34170 However, in the default state the subject and date lines are omitted if no
34171 appropriate headers exist. During the expansion of this file,
34172 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
34173 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
34174 of recipients for the warning message. There may be more than one if there are
34175 multiple addresses with different &%errors_to%& settings on the routers that
34181 . ////////////////////////////////////////////////////////////////////////////
34182 . ////////////////////////////////////////////////////////////////////////////
34184 .chapter "Some common configuration settings" "CHAPcomconreq"
34185 This chapter discusses some configuration settings that seem to be fairly
34186 common. More examples and discussion can be found in the Exim book.
34190 .section "Sending mail to a smart host" "SECID240"
34191 .cindex "smart host" "example router"
34192 If you want to send all mail for non-local domains to a &"smart host"&, you
34193 should replace the default &(dnslookup)& router with a router which does the
34194 routing explicitly:
34196 send_to_smart_host:
34197 driver = manualroute
34198 route_list = !+local_domains smart.host.name
34199 transport = remote_smtp
34201 You can use the smart host's IP address instead of the name if you wish.
34202 If you are using Exim only to submit messages to a smart host, and not for
34203 receiving incoming messages, you can arrange for it to do the submission
34204 synchronously by setting the &%mua_wrapper%& option (see chapter
34205 &<<CHAPnonqueueing>>&).
34210 .section "Using Exim to handle mailing lists" "SECTmailinglists"
34211 .cindex "mailing lists"
34212 Exim can be used to run simple mailing lists, but for large and/or complicated
34213 requirements, the use of additional specialized mailing list software such as
34214 Majordomo or Mailman is recommended.
34216 The &(redirect)& router can be used to handle mailing lists where each list
34217 is maintained in a separate file, which can therefore be managed by an
34218 independent manager. The &%domains%& router option can be used to run these
34219 lists in a separate domain from normal mail. For example:
34223 domains = lists.example
34224 file = /usr/lists/$local_part
34227 errors_to = $local_part-request@lists.example
34230 This router is skipped for domains other than &'lists.example'&. For addresses
34231 in that domain, it looks for a file that matches the local part. If there is no
34232 such file, the router declines, but because &%no_more%& is set, no subsequent
34233 routers are tried, and so the whole delivery fails.
34235 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
34236 expanded into a file name or a pipe delivery, which is usually inappropriate in
34239 .oindex "&%errors_to%&"
34240 The &%errors_to%& option specifies that any delivery errors caused by addresses
34241 taken from a mailing list are to be sent to the given address rather than the
34242 original sender of the message. However, before acting on this, Exim verifies
34243 the error address, and ignores it if verification fails.
34245 For example, using the configuration above, mail sent to
34246 &'dicts@lists.example'& is passed on to those addresses contained in
34247 &_/usr/lists/dicts_&, with error reports directed to
34248 &'dicts-request@lists.example'&, provided that this address can be verified.
34249 There could be a file called &_/usr/lists/dicts-request_& containing
34250 the address(es) of this particular list's manager(s), but other approaches,
34251 such as setting up an earlier router (possibly using the &%local_part_prefix%&
34252 or &%local_part_suffix%& options) to handle addresses of the form
34253 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
34257 .section "Syntax errors in mailing lists" "SECID241"
34258 .cindex "mailing lists" "syntax errors in"
34259 If an entry in redirection data contains a syntax error, Exim normally defers
34260 delivery of the original address. That means that a syntax error in a mailing
34261 list holds up all deliveries to the list. This may not be appropriate when a
34262 list is being maintained automatically from data supplied by users, and the
34263 addresses are not rigorously checked.
34265 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
34266 entries that fail to parse, noting the incident in the log. If in addition
34267 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
34268 whenever a broken address is skipped. It is usually appropriate to set
34269 &%syntax_errors_to%& to the same address as &%errors_to%&.
34273 .section "Re-expansion of mailing lists" "SECID242"
34274 .cindex "mailing lists" "re-expansion of"
34275 Exim remembers every individual address to which a message has been delivered,
34276 in order to avoid duplication, but it normally stores only the original
34277 recipient addresses with a message. If all the deliveries to a mailing list
34278 cannot be done at the first attempt, the mailing list is re-expanded when the
34279 delivery is next tried. This means that alterations to the list are taken into
34280 account at each delivery attempt, so addresses that have been added to
34281 the list since the message arrived will therefore receive a copy of the
34282 message, even though it pre-dates their subscription.
34284 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
34285 on the &(redirect)& router. If this is done, any addresses generated by the
34286 router that fail to deliver at the first attempt are added to the message as
34287 &"top level"& addresses, and the parent address that generated them is marked
34288 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
34289 subsequent delivery attempts. The disadvantage of this is that if any of the
34290 failing addresses are incorrect, correcting them in the file has no effect on
34291 pre-existing messages.
34293 The original top-level address is remembered with each of the generated
34294 addresses, and is output in any log messages. However, any intermediate parent
34295 addresses are not recorded. This makes a difference to the log only if the
34296 &%all_parents%& selector is set, but for mailing lists there is normally only
34297 one level of expansion anyway.
34301 .section "Closed mailing lists" "SECID243"
34302 .cindex "mailing lists" "closed"
34303 The examples so far have assumed open mailing lists, to which anybody may
34304 send mail. It is also possible to set up closed lists, where mail is accepted
34305 from specified senders only. This is done by making use of the generic
34306 &%senders%& option to restrict the router that handles the list.
34308 The following example uses the same file as a list of recipients and as a list
34309 of permitted senders. It requires three routers:
34313 domains = lists.example
34314 local_part_suffix = -request
34315 file = /usr/lists/$local_part$local_part_suffix
34320 domains = lists.example
34321 senders = ${if exists {/usr/lists/$local_part}\
34322 {lsearch;/usr/lists/$local_part}{*}}
34323 file = /usr/lists/$local_part
34326 errors_to = $local_part-request@lists.example
34331 domains = lists.example
34333 data = :fail: $local_part@lists.example is a closed mailing list
34335 All three routers have the same &%domains%& setting, so for any other domains,
34336 they are all skipped. The first router runs only if the local part ends in
34337 &%-request%&. It handles messages to the list manager(s) by means of an open
34340 The second router runs only if the &%senders%& precondition is satisfied. It
34341 checks for the existence of a list that corresponds to the local part, and then
34342 checks that the sender is on the list by means of a linear search. It is
34343 necessary to check for the existence of the file before trying to search it,
34344 because otherwise Exim thinks there is a configuration error. If the file does
34345 not exist, the expansion of &%senders%& is *, which matches all senders. This
34346 means that the router runs, but because there is no list, declines, and
34347 &%no_more%& ensures that no further routers are run. The address fails with an
34348 &"unrouteable address"& error.
34350 The third router runs only if the second router is skipped, which happens when
34351 a mailing list exists, but the sender is not on it. This router forcibly fails
34352 the address, giving a suitable error message.
34357 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
34359 .cindex "Variable Envelope Return Paths"
34360 .cindex "envelope sender"
34361 Variable Envelope Return Paths &-- see &url(http://cr.yp.to/proto/verp.txt) &--
34362 are a way of helping mailing list administrators discover which subscription
34363 address is the cause of a particular delivery failure. The idea is to encode
34364 the original recipient address in the outgoing envelope sender address, so that
34365 if the message is forwarded by another host and then subsequently bounces, the
34366 original recipient can be extracted from the recipient address of the bounce.
34368 .oindex &%errors_to%&
34369 .oindex &%return_path%&
34370 Envelope sender addresses can be modified by Exim using two different
34371 facilities: the &%errors_to%& option on a router (as shown in previous mailing
34372 list examples), or the &%return_path%& option on a transport. The second of
34373 these is effective only if the message is successfully delivered to another
34374 host; it is not used for errors detected on the local host (see the description
34375 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
34376 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
34382 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
34383 {$1-request+$local_part=$domain@your.dom.example}fail}
34385 This has the effect of rewriting the return path (envelope sender) on outgoing
34386 SMTP messages, if the local part of the original return path ends in
34387 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
34388 local part and domain of the recipient into the return path. Suppose, for
34389 example, that a message whose return path has been set to
34390 &'somelist-request@your.dom.example'& is sent to
34391 &'subscriber@other.dom.example'&. In the transport, the return path is
34394 somelist-request+subscriber=other.dom.example@your.dom.example
34396 .vindex "&$local_part$&"
34397 For this to work, you must tell Exim to send multiple copies of messages that
34398 have more than one recipient, so that each copy has just one recipient. This is
34399 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
34400 might be sent to several different recipients in the same domain, in which case
34401 &$local_part$& is not available in the transport, because it is not unique.
34403 Unless your host is doing nothing but mailing list deliveries, you should
34404 probably use a separate transport for the VERP deliveries, so as not to use
34405 extra resources in making one-per-recipient copies for other deliveries. This
34406 can easily be done by expanding the &%transport%& option in the router:
34410 domains = ! +local_domains
34412 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
34413 {verp_smtp}{remote_smtp}}
34416 If you want to change the return path using &%errors_to%& in a router instead
34417 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
34418 routers that handle mailing list addresses. This will ensure that all delivery
34419 errors, including those detected on the local host, are sent to the VERP
34422 On a host that does no local deliveries and has no manual routing, only the
34423 &(dnslookup)& router needs to be changed. A special transport is not needed for
34424 SMTP deliveries. Every mailing list recipient has its own return path value,
34425 and so Exim must hand them to the transport one at a time. Here is an example
34426 of a &(dnslookup)& router that implements VERP:
34430 domains = ! +local_domains
34431 transport = remote_smtp
34433 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
34434 {$1-request+$local_part=$domain@your.dom.example}fail}
34437 Before you start sending out messages with VERPed return paths, you must also
34438 configure Exim to accept the bounce messages that come back to those paths.
34439 Typically this is done by setting a &%local_part_suffix%& option for a
34440 router, and using this to route the messages to wherever you want to handle
34443 The overhead incurred in using VERP depends very much on the size of the
34444 message, the number of recipient addresses that resolve to the same remote
34445 host, and the speed of the connection over which the message is being sent. If
34446 a lot of addresses resolve to the same host and the connection is slow, sending
34447 a separate copy of the message for each address may take substantially longer
34448 than sending a single copy with many recipients (for which VERP cannot be
34456 .section "Virtual domains" "SECTvirtualdomains"
34457 .cindex "virtual domains"
34458 .cindex "domain" "virtual"
34459 The phrase &'virtual domain'& is unfortunately used with two rather different
34463 A domain for which there are no real mailboxes; all valid local parts are
34464 aliases for other email addresses. Common examples are organizational
34465 top-level domains and &"vanity"& domains.
34467 One of a number of independent domains that are all handled by the same host,
34468 with mailboxes on that host, but where the mailbox owners do not necessarily
34469 have login accounts on that host.
34472 The first usage is probably more common, and does seem more &"virtual"& than
34473 the second. This kind of domain can be handled in Exim with a straightforward
34474 aliasing router. One approach is to create a separate alias file for each
34475 virtual domain. Exim can test for the existence of the alias file to determine
34476 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
34477 to a router of this form:
34481 domains = dsearch;/etc/mail/virtual
34482 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
34485 The &%domains%& option specifies that the router is to be skipped, unless there
34486 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
34487 domain that is being processed. When the router runs, it looks up the local
34488 part in the file to find a new address (or list of addresses). The &%no_more%&
34489 setting ensures that if the lookup fails (leading to &%data%& being an empty
34490 string), Exim gives up on the address without trying any subsequent routers.
34492 This one router can handle all the virtual domains because the alias file names
34493 follow a fixed pattern. Permissions can be arranged so that appropriate people
34494 can edit the different alias files. A successful aliasing operation results in
34495 a new envelope recipient address, which is then routed from scratch.
34497 The other kind of &"virtual"& domain can also be handled in a straightforward
34498 way. One approach is to create a file for each domain containing a list of
34499 valid local parts, and use it in a router like this:
34503 domains = dsearch;/etc/mail/domains
34504 local_parts = lsearch;/etc/mail/domains/$domain
34505 transport = my_mailboxes
34507 The address is accepted if there is a file for the domain, and the local part
34508 can be found in the file. The &%domains%& option is used to check for the
34509 file's existence because &%domains%& is tested before the &%local_parts%&
34510 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
34511 because that option is tested after &%local_parts%&. The transport is as
34515 driver = appendfile
34516 file = /var/mail/$domain/$local_part
34519 This uses a directory of mailboxes for each domain. The &%user%& setting is
34520 required, to specify which uid is to be used for writing to the mailboxes.
34522 The configuration shown here is just one example of how you might support this
34523 requirement. There are many other ways this kind of configuration can be set
34524 up, for example, by using a database instead of separate files to hold all the
34525 information about the domains.
34529 .section "Multiple user mailboxes" "SECTmulbox"
34530 .cindex "multiple mailboxes"
34531 .cindex "mailbox" "multiple"
34532 .cindex "local part" "prefix"
34533 .cindex "local part" "suffix"
34534 Heavy email users often want to operate with multiple mailboxes, into which
34535 incoming mail is automatically sorted. A popular way of handling this is to
34536 allow users to use multiple sender addresses, so that replies can easily be
34537 identified. Users are permitted to add prefixes or suffixes to their local
34538 parts for this purpose. The wildcard facility of the generic router options
34539 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
34540 example, consider this router:
34545 file = $home/.forward
34546 local_part_suffix = -*
34547 local_part_suffix_optional
34550 .vindex "&$local_part_suffix$&"
34551 It runs a user's &_.forward_& file for all local parts of the form
34552 &'username-*'&. Within the filter file the user can distinguish different
34553 cases by testing the variable &$local_part_suffix$&. For example:
34555 if $local_part_suffix contains -special then
34556 save /home/$local_part/Mail/special
34559 If the filter file does not exist, or does not deal with such addresses, they
34560 fall through to subsequent routers, and, assuming no subsequent use of the
34561 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
34562 control over which suffixes are valid.
34564 Alternatively, a suffix can be used to trigger the use of a different
34565 &_.forward_& file &-- which is the way a similar facility is implemented in
34571 file = $home/.forward$local_part_suffix
34572 local_part_suffix = -*
34573 local_part_suffix_optional
34576 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
34577 example, &_.forward-special_& is used. Once again, if the appropriate file
34578 does not exist, or does not deal with the address, it is passed on to
34579 subsequent routers, which could, if required, look for an unqualified
34580 &_.forward_& file to use as a default.
34584 .section "Simplified vacation processing" "SECID244"
34585 .cindex "vacation processing"
34586 The traditional way of running the &'vacation'& program is for a user to set up
34587 a pipe command in a &_.forward_& file
34588 (see section &<<SECTspecitredli>>& for syntax details).
34589 This is prone to error by inexperienced users. There are two features of Exim
34590 that can be used to make this process simpler for users:
34593 A local part prefix such as &"vacation-"& can be specified on a router which
34594 can cause the message to be delivered directly to the &'vacation'& program, or
34595 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
34596 &_.forward_& file are then much simpler. For example:
34598 spqr, vacation-spqr
34601 The &%require_files%& generic router option can be used to trigger a
34602 vacation delivery by checking for the existence of a certain file in the
34603 user's home directory. The &%unseen%& generic option should also be used, to
34604 ensure that the original delivery also proceeds. In this case, all the user has
34605 to do is to create a file called, say, &_.vacation_&, containing a vacation
34609 Another advantage of both these methods is that they both work even when the
34610 use of arbitrary pipes by users is locked out.
34614 .section "Taking copies of mail" "SECID245"
34615 .cindex "message" "copying every"
34616 Some installations have policies that require archive copies of all messages to
34617 be made. A single copy of each message can easily be taken by an appropriate
34618 command in a system filter, which could, for example, use a different file for
34619 each day's messages.
34621 There is also a shadow transport mechanism that can be used to take copies of
34622 messages that are successfully delivered by local transports, one copy per
34623 delivery. This could be used, &'inter alia'&, to implement automatic
34624 notification of delivery by sites that insist on doing such things.
34628 .section "Intermittently connected hosts" "SECID246"
34629 .cindex "intermittently connected hosts"
34630 It has become quite common (because it is cheaper) for hosts to connect to the
34631 Internet periodically rather than remain connected all the time. The normal
34632 arrangement is that mail for such hosts accumulates on a system that is
34633 permanently connected.
34635 Exim was designed for use on permanently connected hosts, and so it is not
34636 particularly well-suited to use in an intermittently connected environment.
34637 Nevertheless there are some features that can be used.
34640 .section "Exim on the upstream server host" "SECID247"
34641 It is tempting to arrange for incoming mail for the intermittently connected
34642 host to remain on Exim's queue until the client connects. However, this
34643 approach does not scale very well. Two different kinds of waiting message are
34644 being mixed up in the same queue &-- those that cannot be delivered because of
34645 some temporary problem, and those that are waiting for their destination host
34646 to connect. This makes it hard to manage the queue, as well as wasting
34647 resources, because each queue runner scans the entire queue.
34649 A better approach is to separate off those messages that are waiting for an
34650 intermittently connected host. This can be done by delivering these messages
34651 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
34652 format, from where they are transmitted by other software when their
34653 destination connects. This makes it easy to collect all the mail for one host
34654 in a single directory, and to apply local timeout rules on a per-message basis
34657 On a very small scale, leaving the mail on Exim's queue can be made to work. If
34658 you are doing this, you should configure Exim with a long retry period for the
34659 intermittent host. For example:
34661 cheshire.wonderland.fict.example * F,5d,24h
34663 This stops a lot of failed delivery attempts from occurring, but Exim remembers
34664 which messages it has queued up for that host. Once the intermittent host comes
34665 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
34666 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
34667 causes all the queued up messages to be delivered, often down a single SMTP
34668 connection. While the host remains connected, any new messages get delivered
34671 If the connecting hosts do not have fixed IP addresses, that is, if a host is
34672 issued with a different IP address each time it connects, Exim's retry
34673 mechanisms on the holding host get confused, because the IP address is normally
34674 used as part of the key string for holding retry information. This can be
34675 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
34676 Since this has disadvantages for permanently connected hosts, it is best to
34677 arrange a separate transport for the intermittently connected ones.
34681 .section "Exim on the intermittently connected client host" "SECID248"
34682 The value of &%smtp_accept_queue_per_connection%& should probably be
34683 increased, or even set to zero (that is, disabled) on the intermittently
34684 connected host, so that all incoming messages down a single connection get
34685 delivered immediately.
34687 .cindex "SMTP" "passed connection"
34688 .cindex "SMTP" "multiple deliveries"
34689 .cindex "multiple SMTP deliveries"
34690 Mail waiting to be sent from an intermittently connected host will probably
34691 not have been routed, because without a connection DNS lookups are not
34692 possible. This means that if a normal queue run is done at connection time,
34693 each message is likely to be sent in a separate SMTP session. This can be
34694 avoided by starting the queue run with a command line option beginning with
34695 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
34696 first pass, routing is done but no deliveries take place. The second pass is a
34697 normal queue run; since all the messages have been previously routed, those
34698 destined for the same host are likely to get sent as multiple deliveries in a
34699 single SMTP connection.
34703 . ////////////////////////////////////////////////////////////////////////////
34704 . ////////////////////////////////////////////////////////////////////////////
34706 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
34707 "Exim as a non-queueing client"
34708 .cindex "client, non-queueing"
34709 .cindex "smart host" "suppressing queueing"
34710 On a personal computer, it is a common requirement for all
34711 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
34712 configured to operate that way, for all the popular operating systems.
34713 However, there are some MUAs for Unix-like systems that cannot be so
34714 configured: they submit messages using the command line interface of
34715 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
34718 If the personal computer runs continuously, there is no problem, because it can
34719 run a conventional MTA that handles delivery to the smart host, and deal with
34720 any delays via its queueing mechanism. However, if the computer does not run
34721 continuously or runs different operating systems at different times, queueing
34722 email is not desirable.
34724 There is therefore a requirement for something that can provide the
34725 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
34726 any queueing or retrying facilities. Furthermore, the delivery to the smart
34727 host should be synchronous, so that if it fails, the sending MUA is immediately
34728 informed. In other words, we want something that extends an MUA that submits
34729 to a local MTA via the command line so that it behaves like one that submits
34730 to a remote smart host using TCP/SMTP.
34732 There are a number of applications (for example, there is one called &'ssmtp'&)
34733 that do this job. However, people have found them to be lacking in various
34734 ways. For instance, you might want to allow aliasing and forwarding to be done
34735 before sending a message to the smart host.
34737 Exim already had the necessary infrastructure for doing this job. Just a few
34738 tweaks were needed to make it behave as required, though it is somewhat of an
34739 overkill to use a fully-featured MTA for this purpose.
34741 .oindex "&%mua_wrapper%&"
34742 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
34743 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
34744 assumes that it is being used to &"wrap"& a command-line MUA in the manner
34745 just described. As well as setting &%mua_wrapper%&, you also need to provide a
34746 compatible router and transport configuration. Typically there will be just one
34747 router and one transport, sending everything to a smart host.
34749 When run in MUA wrapping mode, the behaviour of Exim changes in the
34753 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
34754 In other words, the only way to submit messages is via the command line.
34756 Each message is synchronously delivered as soon as it is received (&%-odi%& is
34757 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
34758 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
34759 does not finish until the delivery attempt is complete. If the delivery is
34760 successful, a zero return code is given.
34762 Address redirection is permitted, but the final routing for all addresses must
34763 be to the same remote transport, and to the same list of hosts. Furthermore,
34764 the return address (envelope sender) must be the same for all recipients, as
34765 must any added or deleted header lines. In other words, it must be possible to
34766 deliver the message in a single SMTP transaction, however many recipients there
34769 If these conditions are not met, or if routing any address results in a
34770 failure or defer status, or if Exim is unable to deliver all the recipients
34771 successfully to one of the smart hosts, delivery of the entire message fails.
34773 Because no queueing is allowed, all failures are treated as permanent; there
34774 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
34775 smart host. Furthermore, because only a single yes/no response can be given to
34776 the caller, it is not possible to deliver to some recipients and not others. If
34777 there is an error (temporary or permanent) for any recipient, all are failed.
34779 If more than one smart host is listed, Exim will try another host after a
34780 connection failure or a timeout, in the normal way. However, if this kind of
34781 failure happens for all the hosts, the delivery fails.
34783 When delivery fails, an error message is written to the standard error stream
34784 (as well as to Exim's log), and Exim exits to the caller with a return code
34785 value 1. The message is expunged from Exim's spool files. No bounce messages
34786 are ever generated.
34788 No retry data is maintained, and any retry rules are ignored.
34790 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
34791 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
34792 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
34795 The overall effect is that Exim makes a single synchronous attempt to deliver
34796 the message, failing if there is any kind of problem. Because no local
34797 deliveries are done and no daemon can be run, Exim does not need root
34798 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
34799 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
34800 the advantages and disadvantages of running without root privilege.
34805 . ////////////////////////////////////////////////////////////////////////////
34806 . ////////////////////////////////////////////////////////////////////////////
34808 .chapter "Log files" "CHAPlog"
34809 .scindex IIDloggen "log" "general description"
34810 .cindex "log" "types of"
34811 Exim writes three different logs, referred to as the main log, the reject log,
34816 The main log records the arrival of each message and each delivery in a single
34817 line in each case. The format is as compact as possible, in an attempt to keep
34818 down the size of log files. Two-character flag sequences make it easy to pick
34819 out these lines. A number of other events are recorded in the main log. Some of
34820 them are optional, in which case the &%log_selector%& option controls whether
34821 they are included or not. A Perl script called &'eximstats'&, which does simple
34822 analysis of main log files, is provided in the Exim distribution (see section
34823 &<<SECTmailstat>>&).
34825 .cindex "reject log"
34826 The reject log records information from messages that are rejected as a result
34827 of a configuration option (that is, for policy reasons).
34828 The first line of each rejection is a copy of the line that is also written to
34829 the main log. Then, if the message's header has been read at the time the log
34830 is written, its contents are written to this log. Only the original header
34831 lines are available; header lines added by ACLs are not logged. You can use the
34832 reject log to check that your policy controls are working correctly; on a busy
34833 host this may be easier than scanning the main log for rejection messages. You
34834 can suppress the writing of the reject log by setting &%write_rejectlog%&
34837 .cindex "panic log"
34838 .cindex "system log"
34839 When certain serious errors occur, Exim writes entries to its panic log. If the
34840 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
34841 are usually written to the main log as well, but can get lost amid the mass of
34842 other entries. The panic log should be empty under normal circumstances. It is
34843 therefore a good idea to check it (or to have a &'cron'& script check it)
34844 regularly, in order to become aware of any problems. When Exim cannot open its
34845 panic log, it tries as a last resort to write to the system log (syslog). This
34846 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
34847 message itself is written at priority LOG_CRIT.
34850 Every log line starts with a timestamp, in the format shown in the following
34851 example. Note that many of the examples shown in this chapter are line-wrapped.
34852 In the log file, this would be all on one line:
34854 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
34857 By default, the timestamps are in the local timezone. There are two
34858 ways of changing this:
34861 You can set the &%timezone%& option to a different time zone; in particular, if
34866 the timestamps will be in UTC (aka GMT).
34868 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
34871 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
34875 .cindex "log" "process ids in"
34876 .cindex "pid (process id)" "in log lines"
34877 Exim does not include its process id in log lines by default, but you can
34878 request that it does so by specifying the &`pid`& log selector (see section
34879 &<<SECTlogselector>>&). When this is set, the process id is output, in square
34880 brackets, immediately after the time and date.
34885 .section "Where the logs are written" "SECTwhelogwri"
34886 .cindex "log" "destination"
34887 .cindex "log" "to file"
34888 .cindex "log" "to syslog"
34890 The logs may be written to local files, or to syslog, or both. However, it
34891 should be noted that many syslog implementations use UDP as a transport, and
34892 are therefore unreliable in the sense that messages are not guaranteed to
34893 arrive at the loghost, nor is the ordering of messages necessarily maintained.
34894 It has also been reported that on large log files (tens of megabytes) you may
34895 need to tweak syslog to prevent it syncing the file with each write &-- on
34896 Linux this has been seen to make syslog take 90% plus of CPU time.
34898 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
34899 &_Local/Makefile_& or by setting &%log_file_path%& in the run time
34900 configuration. This latter string is expanded, so it can contain, for example,
34901 references to the host name:
34903 log_file_path = /var/log/$primary_hostname/exim_%slog
34905 It is generally advisable, however, to set the string in &_Local/Makefile_&
34906 rather than at run time, because then the setting is available right from the
34907 start of Exim's execution. Otherwise, if there's something it wants to log
34908 before it has read the configuration file (for example, an error in the
34909 configuration file) it will not use the path you want, and may not be able to
34912 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
34913 list, currently limited to at most two items. This is one option where the
34914 facility for changing a list separator may not be used. The list must always be
34915 colon-separated. If an item in the list is &"syslog"& then syslog is used;
34916 otherwise the item must either be an absolute path, containing &`%s`& at the
34917 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
34918 implying the use of a default path.
34920 When Exim encounters an empty item in the list, it searches the list defined by
34921 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
34922 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
34923 mean &"use the path specified at build time"&. It no such item exists, log
34924 files are written in the &_log_& subdirectory of the spool directory. This is
34925 equivalent to the setting:
34927 log_file_path = $spool_directory/log/%slog
34929 If you do not specify anything at build time or run time,
34930 or if you unset the option at run time (i.e. &`log_file_path = `&),
34931 that is where the logs are written.
34933 A log file path may also contain &`%D`& or &`%M`& if datestamped log file names
34934 are in use &-- see section &<<SECTdatlogfil>>& below.
34936 Here are some examples of possible settings:
34938 &`LOG_FILE_PATH=syslog `& syslog only
34939 &`LOG_FILE_PATH=:syslog `& syslog and default path
34940 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
34941 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
34943 If there are more than two paths in the list, the first is used and a panic
34948 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
34949 .cindex "log" "cycling local files"
34950 .cindex "cycling logs"
34951 .cindex "&'exicyclog'&"
34952 .cindex "log" "local files; writing to"
34953 Some operating systems provide centralized and standardized methods for cycling
34954 log files. For those that do not, a utility script called &'exicyclog'& is
34955 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
34956 main and reject logs each time it is called. The maximum number of old logs to
34957 keep can be set. It is suggested this script is run as a daily &'cron'& job.
34959 An Exim delivery process opens the main log when it first needs to write to it,
34960 and it keeps the file open in case subsequent entries are required &-- for
34961 example, if a number of different deliveries are being done for the same
34962 message. However, remote SMTP deliveries can take a long time, and this means
34963 that the file may be kept open long after it is renamed if &'exicyclog'& or
34964 something similar is being used to rename log files on a regular basis. To
34965 ensure that a switch of log files is noticed as soon as possible, Exim calls
34966 &[stat()]& on the main log's name before reusing an open file, and if the file
34967 does not exist, or its inode has changed, the old file is closed and Exim
34968 tries to open the main log from scratch. Thus, an old log file may remain open
34969 for quite some time, but no Exim processes should write to it once it has been
34974 .section "Datestamped log files" "SECTdatlogfil"
34975 .cindex "log" "datestamped files"
34976 Instead of cycling the main and reject log files by renaming them
34977 periodically, some sites like to use files whose names contain a datestamp,
34978 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
34979 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
34980 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
34981 point where the datestamp is required. For example:
34983 log_file_path = /var/spool/exim/log/%slog-%D
34984 log_file_path = /var/log/exim-%s-%D.log
34985 log_file_path = /var/spool/exim/log/%D-%slog
34986 log_file_path = /var/log/exim/%s.%M
34988 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
34989 examples of names generated by the above examples:
34991 /var/spool/exim/log/mainlog-20021225
34992 /var/log/exim-reject-20021225.log
34993 /var/spool/exim/log/20021225-mainlog
34994 /var/log/exim/main.200212
34996 When this form of log file is specified, Exim automatically switches to new
34997 files at midnight. It does not make any attempt to compress old logs; you
34998 will need to write your own script if you require this. You should not
34999 run &'exicyclog'& with this form of logging.
35001 The location of the panic log is also determined by &%log_file_path%&, but it
35002 is not datestamped, because rotation of the panic log does not make sense.
35003 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
35004 the string. In addition, if it immediately follows a slash, a following
35005 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
35006 character is removed. Thus, the four examples above would give these panic
35009 /var/spool/exim/log/paniclog
35010 /var/log/exim-panic.log
35011 /var/spool/exim/log/paniclog
35012 /var/log/exim/panic
35016 .section "Logging to syslog" "SECID249"
35017 .cindex "log" "syslog; writing to"
35018 The use of syslog does not change what Exim logs or the format of its messages,
35019 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
35020 Exim's log lines are omitted when these lines are sent to syslog. Apart from
35021 that, the same strings are written to syslog as to log files. The syslog
35022 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
35023 by default, but you can change these by setting the &%syslog_facility%& and
35024 &%syslog_processname%& options, respectively. If Exim was compiled with
35025 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
35026 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
35027 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
35028 the time and host name to each line.
35029 The three log streams are mapped onto syslog priorities as follows:
35032 &'mainlog'& is mapped to LOG_INFO
35034 &'rejectlog'& is mapped to LOG_NOTICE
35036 &'paniclog'& is mapped to LOG_ALERT
35039 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
35040 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
35041 these are routed by syslog to the same place. You can suppress this duplication
35042 by setting &%syslog_duplication%& false.
35044 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
35045 entries contain multiple lines when headers are included. To cope with both
35046 these cases, entries written to syslog are split into separate &[syslog()]&
35047 calls at each internal newline, and also after a maximum of
35048 870 data characters. (This allows for a total syslog line length of 1024, when
35049 additions such as timestamps are added.) If you are running a syslog
35050 replacement that can handle lines longer than the 1024 characters allowed by
35051 RFC 3164, you should set
35053 SYSLOG_LONG_LINES=yes
35055 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
35056 lines, but it still splits at internal newlines in &'reject'& log entries.
35058 To make it easy to re-assemble split lines later, each component of a split
35059 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
35060 where <&'n'&> is the component number and <&'m'&> is the total number of
35061 components in the entry. The / delimiter is used when the line was split
35062 because it was too long; if it was split because of an internal newline, the \
35063 delimiter is used. For example, supposing the length limit to be 50 instead of
35064 870, the following would be the result of a typical rejection message to
35065 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
35066 name, and pid as added by syslog:
35068 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
35069 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
35070 [3/5] when scanning for sender: missing or malformed lo
35071 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
35074 The same error might cause the following lines to be written to &"rejectlog"&
35077 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
35078 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
35079 [3/18] er when scanning for sender: missing or malformed
35080 [4/18] local part in "<>" (envelope sender is <ph10@cam
35082 [6\18] Recipients: ph10@some.domain.cam.example
35083 [7\18] P Received: from [127.0.0.1] (ident=ph10)
35084 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
35085 [9\18] id 16RdAL-0006pc-00
35086 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
35087 [11\18] 09:43 +0100
35089 [13\18] Subject: this is a test header
35090 [18\18] X-something: this is another header
35091 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
35094 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
35096 Log lines that are neither too long nor contain newlines are written to syslog
35097 without modification.
35099 If only syslog is being used, the Exim monitor is unable to provide a log tail
35100 display, unless syslog is routing &'mainlog'& to a file on the local host and
35101 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
35106 .section "Log line flags" "SECID250"
35107 One line is written to the main log for each message received, and for each
35108 successful, unsuccessful, and delayed delivery. These lines can readily be
35109 picked out by the distinctive two-character flags that immediately follow the
35110 timestamp. The flags are:
35112 &`<=`& message arrival
35113 &`=>`& normal message delivery
35114 &`->`& additional address in same delivery
35115 &`>>`& cutthrough message delivery
35116 &`*>`& delivery suppressed by &%-N%&
35117 &`**`& delivery failed; address bounced
35118 &`==`& delivery deferred; temporary problem
35122 .section "Logging message reception" "SECID251"
35123 .cindex "log" "reception line"
35124 The format of the single-line entry in the main log that is written for every
35125 message received is shown in the basic example below, which is split over
35126 several lines in order to fit it on the page:
35128 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
35129 H=mailer.fict.example [192.168.123.123] U=exim
35130 P=smtp S=5678 id=<incoming message id>
35132 The address immediately following &"<="& is the envelope sender address. A
35133 bounce message is shown with the sender address &"<>"&, and if it is locally
35134 generated, this is followed by an item of the form
35138 which is a reference to the message that caused the bounce to be sent.
35142 For messages from other hosts, the H and U fields identify the remote host and
35143 record the RFC 1413 identity of the user that sent the message, if one was
35144 received. The number given in square brackets is the IP address of the sending
35145 host. If there is a single, unparenthesized host name in the H field, as
35146 above, it has been verified to correspond to the IP address (see the
35147 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
35148 by the remote host in the SMTP HELO or EHLO command, and has not been
35149 verified. If verification yields a different name to that given for HELO or
35150 EHLO, the verified name appears first, followed by the HELO or EHLO
35151 name in parentheses.
35153 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
35154 without brackets, in the HELO or EHLO command, leading to entries in
35155 the log containing text like these examples:
35157 H=(10.21.32.43) [192.168.8.34]
35158 H=([10.21.32.43]) [192.168.8.34]
35160 This can be confusing. Only the final address in square brackets can be relied
35163 For locally generated messages (that is, messages not received over TCP/IP),
35164 the H field is omitted, and the U field contains the login name of the caller
35167 .cindex "authentication" "logging"
35168 .cindex "AUTH" "logging"
35169 For all messages, the P field specifies the protocol used to receive the
35170 message. This is the value that is stored in &$received_protocol$&. In the case
35171 of incoming SMTP messages, the value indicates whether or not any SMTP
35172 extensions (ESMTP), encryption, or authentication were used. If the SMTP
35173 session was encrypted, there is an additional X field that records the cipher
35174 suite that was used.
35176 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
35177 hosts that have authenticated themselves using the SMTP AUTH command. The first
35178 value is used when the SMTP connection was encrypted (&"secure"&). In this case
35179 there is an additional item A= followed by the name of the authenticator that
35180 was used. If an authenticated identification was set up by the authenticator's
35181 &%server_set_id%& option, this is logged too, separated by a colon from the
35182 authenticator name.
35184 .cindex "size" "of message"
35185 The id field records the existing message id, if present. The size of the
35186 received message is given by the S field. When the message is delivered,
35187 headers may be removed or added, so that the size of delivered copies of the
35188 message may not correspond with this value (and indeed may be different to each
35191 The &%log_selector%& option can be used to request the logging of additional
35192 data when a message is received. See section &<<SECTlogselector>>& below.
35196 .section "Logging deliveries" "SECID252"
35197 .cindex "log" "delivery line"
35198 The format of the single-line entry in the main log that is written for every
35199 delivery is shown in one of the examples below, for local and remote
35200 deliveries, respectively. Each example has been split into multiple lines in order
35201 to fit it on the page:
35203 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
35204 <marv@hitch.fict.example> R=localuser T=local_delivery
35205 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
35206 monk@holistic.fict.example R=dnslookup T=remote_smtp
35207 H=holistic.fict.example [192.168.234.234]
35209 For ordinary local deliveries, the original address is given in angle brackets
35210 after the final delivery address, which might be a pipe or a file. If
35211 intermediate address(es) exist between the original and the final address, the
35212 last of these is given in parentheses after the final address. The R and T
35213 fields record the router and transport that were used to process the address.
35215 If SMTP AUTH was used for the delivery there is an additional item A=
35216 followed by the name of the authenticator that was used.
35217 If an authenticated identification was set up by the authenticator's &%client_set_id%&
35218 option, this is logged too, separated by a colon from the authenticator name.
35220 If a shadow transport was run after a successful local delivery, the log line
35221 for the successful delivery has an item added on the end, of the form
35223 &`ST=<`&&'shadow transport name'&&`>`&
35225 If the shadow transport did not succeed, the error message is put in
35226 parentheses afterwards.
35228 .cindex "asterisk" "after IP address"
35229 When more than one address is included in a single delivery (for example, two
35230 SMTP RCPT commands in one transaction) the second and subsequent addresses are
35231 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
35232 down a single SMTP connection, an asterisk follows the IP address in the log
35233 lines for the second and subsequent messages.
35235 .cindex "delivery" "cutthrough; logging"
35236 .cindex "cutthrough" "logging"
35237 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
35238 line precedes the reception line, since cutthrough waits for a possible
35239 rejection from the destination in case it can reject the sourced item.
35241 The generation of a reply message by a filter file gets logged as a
35242 &"delivery"& to the addressee, preceded by &">"&.
35244 The &%log_selector%& option can be used to request the logging of additional
35245 data when a message is delivered. See section &<<SECTlogselector>>& below.
35248 .section "Discarded deliveries" "SECID253"
35249 .cindex "discarded messages"
35250 .cindex "message" "discarded"
35251 .cindex "delivery" "discarded; logging"
35252 When a message is discarded as a result of the command &"seen finish"& being
35253 obeyed in a filter file which generates no deliveries, a log entry of the form
35255 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
35256 <low.club@bridge.example> R=userforward
35258 is written, to record why no deliveries are logged. When a message is discarded
35259 because it is aliased to &":blackhole:"& the log line is like this:
35261 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
35262 <hole@nowhere.example> R=blackhole_router
35266 .section "Deferred deliveries" "SECID254"
35267 When a delivery is deferred, a line of the following form is logged:
35269 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
35270 R=dnslookup T=smtp defer (146): Connection refused
35272 In the case of remote deliveries, the error is the one that was given for the
35273 last IP address that was tried. Details of individual SMTP failures are also
35274 written to the log, so the above line would be preceded by something like
35276 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
35277 mail1.endrest.example [192.168.239.239]: Connection refused
35279 When a deferred address is skipped because its retry time has not been reached,
35280 a message is written to the log, but this can be suppressed by setting an
35281 appropriate value in &%log_selector%&.
35285 .section "Delivery failures" "SECID255"
35286 .cindex "delivery" "failure; logging"
35287 If a delivery fails because an address cannot be routed, a line of the
35288 following form is logged:
35290 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
35291 <jim@trek99.example>: unknown mail domain
35293 If a delivery fails at transport time, the router and transport are shown, and
35294 the response from the remote host is included, as in this example:
35296 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
35297 R=dnslookup T=remote_smtp: SMTP error from remote mailer
35298 after pipelined RCPT TO:<ace400@pb.example>: host
35299 pbmail3.py.example [192.168.63.111]: 553 5.3.0
35300 <ace400@pb.example>...Addressee unknown
35302 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
35303 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
35304 disabling PIPELINING. The log lines for all forms of delivery failure are
35305 flagged with &`**`&.
35309 .section "Fake deliveries" "SECID256"
35310 .cindex "delivery" "fake; logging"
35311 If a delivery does not actually take place because the &%-N%& option has been
35312 used to suppress it, a normal delivery line is written to the log, except that
35313 &"=>"& is replaced by &"*>"&.
35317 .section "Completion" "SECID257"
35320 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
35322 is written to the main log when a message is about to be removed from the spool
35323 at the end of its processing.
35328 .section "Summary of Fields in Log Lines" "SECID258"
35329 .cindex "log" "summary of fields"
35330 A summary of the field identifiers that are used in log lines is shown in
35331 the following table:
35333 &`A `& authenticator name (and optional id and sender)
35334 &`C `& SMTP confirmation on delivery
35335 &` `& command list for &"no mail in SMTP session"&
35336 &`CV `& certificate verification status
35337 &`D `& duration of &"no mail in SMTP session"&
35338 &`DN `& distinguished name from peer certificate
35339 &`DT `& on &`=>`& lines: time taken for a delivery
35340 &`F `& sender address (on delivery lines)
35341 &`H `& host name and IP address
35342 &`I `& local interface used
35343 &`id `& message id for incoming message
35344 &`P `& on &`<=`& lines: protocol used
35345 &` `& on &`=>`& and &`**`& lines: return path
35346 &`QT `& on &`=>`& lines: time spent on queue so far
35347 &` `& on &"Completed"& lines: time spent on queue
35348 &`R `& on &`<=`& lines: reference for local bounce
35349 &` `& on &`=>`& &`**`& and &`==`& lines: router name
35350 &`S `& size of message
35351 &`SNI `& server name indication from TLS client hello
35352 &`ST `& shadow transport name
35353 &`T `& on &`<=`& lines: message subject (topic)
35354 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
35355 &`U `& local user or RFC 1413 identity
35356 &`X `& TLS cipher suite
35360 .section "Other log entries" "SECID259"
35361 Various other types of log entry are written from time to time. Most should be
35362 self-explanatory. Among the more common are:
35365 .cindex "retry" "time not reached"
35366 &'retry time not reached'&&~&~An address previously suffered a temporary error
35367 during routing or local delivery, and the time to retry has not yet arrived.
35368 This message is not written to an individual message log file unless it happens
35369 during the first delivery attempt.
35371 &'retry time not reached for any host'&&~&~An address previously suffered
35372 temporary errors during remote delivery, and the retry time has not yet arrived
35373 for any of the hosts to which it is routed.
35375 .cindex "spool directory" "file locked"
35376 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
35377 some other Exim process is already working on the message. This can be quite
35378 common if queue running processes are started at frequent intervals. The
35379 &'exiwhat'& utility script can be used to find out what Exim processes are
35382 .cindex "error" "ignored"
35383 &'error ignored'&&~&~There are several circumstances that give rise to this
35386 Exim failed to deliver a bounce message whose age was greater than
35387 &%ignore_bounce_errors_after%&. The bounce was discarded.
35389 A filter file set up a delivery using the &"noerror"& option, and the delivery
35390 failed. The delivery was discarded.
35392 A delivery set up by a router configured with
35393 . ==== As this is a nested list, any displays it contains must be indented
35394 . ==== as otherwise they are too far to the left.
35398 failed. The delivery was discarded.
35406 .section "Reducing or increasing what is logged" "SECTlogselector"
35407 .cindex "log" "selectors"
35408 By setting the &%log_selector%& global option, you can disable some of Exim's
35409 default logging, or you can request additional logging. The value of
35410 &%log_selector%& is made up of names preceded by plus or minus characters. For
35413 log_selector = +arguments -retry_defer
35415 The list of optional log items is in the following table, with the default
35416 selection marked by asterisks:
35418 &` 8bitmime `& received 8BITMIME status
35419 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
35420 &` address_rewrite `& address rewriting
35421 &` all_parents `& all parents in => lines
35422 &` arguments `& command line arguments
35423 &`*connection_reject `& connection rejections
35424 &`*delay_delivery `& immediate delivery delayed
35425 &` deliver_time `& time taken to perform delivery
35426 &` delivery_size `& add &`S=`&&'nnn'& to => lines
35427 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
35428 &`*etrn `& ETRN commands
35429 &`*host_lookup_failed `& as it says
35430 &` ident_timeout `& timeout for ident connection
35431 &` incoming_interface `& local interface on <= and => lines
35432 &` incoming_port `& remote port on <= lines
35433 &`*lost_incoming_connection `& as it says (includes timeouts)
35435 &` outgoing_interface `& local interface on => lines
35437 &` outgoing_port `& add remote port to => lines
35438 &`*queue_run `& start and end queue runs
35439 &` queue_time `& time on queue for one recipient
35440 &` queue_time_overall `& time on queue for whole message
35441 &` pid `& Exim process id
35442 &` received_recipients `& recipients on <= lines
35443 &` received_sender `& sender on <= lines
35444 &`*rejected_header `& header contents on reject log
35445 &`*retry_defer `& &"retry time not reached"&
35446 &` return_path_on_delivery `& put return path on => and ** lines
35447 &` sender_on_delivery `& add sender to => lines
35448 &`*sender_verify_fail `& sender verification failures
35449 &`*size_reject `& rejection because too big
35450 &`*skip_delivery `& delivery skipped in a queue run
35451 &`*smtp_confirmation `& SMTP confirmation on => lines
35452 &` smtp_connection `& incoming SMTP connections
35453 &` smtp_incomplete_transaction`& incomplete SMTP transactions
35454 &` smtp_mailauth `& AUTH argument to MAIL commands
35455 &` smtp_no_mail `& session with no MAIL commands
35456 &` smtp_protocol_error `& SMTP protocol errors
35457 &` smtp_syntax_error `& SMTP syntax errors
35458 &` subject `& contents of &'Subject:'& on <= lines
35459 &`*tls_certificate_verified `& certificate verification status
35460 &`*tls_cipher `& TLS cipher suite on <= and => lines
35461 &` tls_peerdn `& TLS peer DN on <= and => lines
35462 &` tls_sni `& TLS SNI on <= lines
35463 &` unknown_in_list `& DNS lookup failed in list match
35465 &` all `& all of the above
35467 See also the &%slow_lookup_log%& main configuration option,
35468 section &<<SECID99>>&
35470 More details on each of these items follows:
35474 .cindex "log" "8BITMIME"
35475 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
35476 which may help in tracking down interoperability issues with ancient MTAs
35477 that are not 8bit clean. This is added to the &"<="& line, tagged with
35478 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
35479 &`7BIT`& and &`8BITMIME`& respectively.
35481 .cindex "&%warn%& ACL verb" "log when skipping"
35482 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
35483 its conditions cannot be evaluated, a log line to this effect is written if
35484 this log selector is set.
35486 .cindex "log" "rewriting"
35487 .cindex "rewriting" "logging"
35488 &%address_rewrite%&: This applies both to global rewrites and per-transport
35489 rewrites, but not to rewrites in filters run as an unprivileged user (because
35490 such users cannot access the log).
35492 .cindex "log" "full parentage"
35493 &%all_parents%&: Normally only the original and final addresses are logged on
35494 delivery lines; with this selector, intermediate parents are given in
35495 parentheses between them.
35497 .cindex "log" "Exim arguments"
35498 .cindex "Exim arguments, logging"
35499 &%arguments%&: This causes Exim to write the arguments with which it was called
35500 to the main log, preceded by the current working directory. This is a debugging
35501 feature, added to make it easier to find out how certain MUAs call
35502 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
35503 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
35504 that are empty or that contain white space are quoted. Non-printing characters
35505 are shown as escape sequences. This facility cannot log unrecognized arguments,
35506 because the arguments are checked before the configuration file is read. The
35507 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
35508 between the caller and Exim.
35510 .cindex "log" "connection rejections"
35511 &%connection_reject%&: A log entry is written whenever an incoming SMTP
35512 connection is rejected, for whatever reason.
35514 .cindex "log" "delayed delivery"
35515 .cindex "delayed delivery, logging"
35516 &%delay_delivery%&: A log entry is written whenever a delivery process is not
35517 started for an incoming message because the load is too high or too many
35518 messages were received on one connection. Logging does not occur if no delivery
35519 process is started because &%queue_only%& is set or &%-odq%& was used.
35521 .cindex "log" "delivery duration"
35522 &%deliver_time%&: For each delivery, the amount of real time it has taken to
35523 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
35525 .cindex "log" "message size on delivery"
35526 .cindex "size" "of message"
35527 &%delivery_size%&: For each delivery, the size of message delivered is added to
35528 the &"=>"& line, tagged with S=.
35530 .cindex "log" "dnslist defer"
35531 .cindex "DNS list" "logging defer"
35532 .cindex "black list (DNS)"
35533 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
35534 DNS black list suffers a temporary error.
35536 .cindex "log" "ETRN commands"
35537 .cindex "ETRN" "logging"
35538 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
35539 is run to determine whether or not it is actually accepted. An invalid ETRN
35540 command, or one received within a message transaction is not logged by this
35541 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
35543 .cindex "log" "host lookup failure"
35544 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
35545 any addresses, or when a lookup of an IP address fails to find a host name, a
35546 log line is written. This logging does not apply to direct DNS lookups when
35547 routing email addresses, but it does apply to &"byname"& lookups.
35549 .cindex "log" "ident timeout"
35550 .cindex "RFC 1413" "logging timeout"
35551 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
35552 client's ident port times out.
35554 .cindex "log" "incoming interface"
35555 .cindex "log" "local interface"
35556 .cindex "log" "local address and port"
35557 .cindex "TCP/IP" "logging local address and port"
35558 .cindex "interface" "logging"
35559 &%incoming_interface%&: The interface on which a message was received is added
35560 to the &"<="& line as an IP address in square brackets, tagged by I= and
35561 followed by a colon and the port number. The local interface and port are also
35562 added to other SMTP log lines, for example &"SMTP connection from"&, to
35563 rejection lines, and (despite the name) to outgoing &"=>"& and &"->"& lines.
35565 The latter can be disabled by turning off the &%outgoing_interface%& option.
35568 .cindex "log" "incoming remote port"
35569 .cindex "port" "logging remote"
35570 .cindex "TCP/IP" "logging incoming remote port"
35571 .vindex "&$sender_fullhost$&"
35572 .vindex "&$sender_rcvhost$&"
35573 &%incoming_port%&: The remote port number from which a message was received is
35574 added to log entries and &'Received:'& header lines, following the IP address
35575 in square brackets, and separated from it by a colon. This is implemented by
35576 changing the value that is put in the &$sender_fullhost$& and
35577 &$sender_rcvhost$& variables. Recording the remote port number has become more
35578 important with the widening use of NAT (see RFC 2505).
35580 .cindex "log" "dropped connection"
35581 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
35582 connection is unexpectedly dropped.
35584 .cindex "log" "outgoing interface"
35585 .cindex "log" "local interface"
35586 .cindex "log" "local address and port"
35587 .cindex "TCP/IP" "logging local address and port"
35588 .cindex "interface" "logging"
35590 &%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
35591 interface on which a message was sent is added to delivery lines as an I= tag
35592 followed by IP address in square brackets. You can disable this by turning
35593 off the &%outgoing_interface%& option.
35596 .cindex "log" "outgoing remote port"
35597 .cindex "port" "logging outgoint remote"
35598 .cindex "TCP/IP" "logging ougtoing remote port"
35599 &%outgoing_port%&: The remote port number is added to delivery log lines (those
35600 containing => tags) following the IP address.
35602 The local port is also added if &%incoming_interface%& and
35603 &%outgoing_interface%& are both enabled.
35605 This option is not included in the default setting, because for most ordinary
35606 configurations, the remote port number is always 25 (the SMTP port), and the
35607 local port is a random ephemeral port.
35609 .cindex "log" "process ids in"
35610 .cindex "pid (process id)" "in log lines"
35611 &%pid%&: The current process id is added to every log line, in square brackets,
35612 immediately after the time and date.
35614 .cindex "log" "queue run"
35615 .cindex "queue runner" "logging"
35616 &%queue_run%&: The start and end of every queue run are logged.
35618 .cindex "log" "queue time"
35619 &%queue_time%&: The amount of time the message has been in the queue on the
35620 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
35621 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
35622 includes reception time as well as the delivery time for the current address.
35623 This means that it may be longer than the difference between the arrival and
35624 delivery log line times, because the arrival log line is not written until the
35625 message has been successfully received.
35627 &%queue_time_overall%&: The amount of time the message has been in the queue on
35628 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
35629 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
35630 message, so it includes reception time as well as the total delivery time.
35632 .cindex "log" "recipients"
35633 &%received_recipients%&: The recipients of a message are listed in the main log
35634 as soon as the message is received. The list appears at the end of the log line
35635 that is written when a message is received, preceded by the word &"for"&. The
35636 addresses are listed after they have been qualified, but before any rewriting
35638 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
35641 .cindex "log" "sender reception"
35642 &%received_sender%&: The unrewritten original sender of a message is added to
35643 the end of the log line that records the message's arrival, after the word
35644 &"from"& (before the recipients if &%received_recipients%& is also set).
35646 .cindex "log" "header lines for rejection"
35647 &%rejected_header%&: If a message's header has been received at the time a
35648 rejection is written to the reject log, the complete header is added to the
35649 log. Header logging can be turned off individually for messages that are
35650 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
35652 .cindex "log" "retry defer"
35653 &%retry_defer%&: A log line is written if a delivery is deferred because a
35654 retry time has not yet been reached. However, this &"retry time not reached"&
35655 message is always omitted from individual message logs after the first delivery
35658 .cindex "log" "return path"
35659 &%return_path_on_delivery%&: The return path that is being transmitted with
35660 the message is included in delivery and bounce lines, using the tag P=.
35661 This is omitted if no delivery actually happens, for example, if routing fails,
35662 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
35664 .cindex "log" "sender on delivery"
35665 &%sender_on_delivery%&: The message's sender address is added to every delivery
35666 and bounce line, tagged by F= (for &"from"&).
35667 This is the original sender that was received with the message; it is not
35668 necessarily the same as the outgoing return path.
35670 .cindex "log" "sender verify failure"
35671 &%sender_verify_fail%&: If this selector is unset, the separate log line that
35672 gives details of a sender verification failure is not written. Log lines for
35673 the rejection of SMTP commands contain just &"sender verify failed"&, so some
35676 .cindex "log" "size rejection"
35677 &%size_reject%&: A log line is written whenever a message is rejected because
35680 .cindex "log" "frozen messages; skipped"
35681 .cindex "frozen messages" "logging skipping"
35682 &%skip_delivery%&: A log line is written whenever a message is skipped during a
35683 queue run because it is frozen or because another process is already delivering
35685 .cindex "&""spool file is locked""&"
35686 The message that is written is &"spool file is locked"&.
35688 .cindex "log" "smtp confirmation"
35689 .cindex "SMTP" "logging confirmation"
35690 .cindex "LMTP" "logging confirmation"
35691 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
35692 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
35693 A number of MTAs (including Exim) return an identifying string in this
35696 .cindex "log" "SMTP connections"
35697 .cindex "SMTP" "logging connections"
35698 &%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
35699 established or closed, unless the connection is from a host that matches
35700 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
35701 only when the closure is unexpected.) This applies to connections from local
35702 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
35703 dropped in the middle of a message, a log line is always written, whether or
35704 not this selector is set, but otherwise nothing is written at the start and end
35705 of connections unless this selector is enabled.
35707 For TCP/IP connections to an Exim daemon, the current number of connections is
35708 included in the log message for each new connection, but note that the count is
35709 reset if the daemon is restarted.
35710 Also, because connections are closed (and the closure is logged) in
35711 subprocesses, the count may not include connections that have been closed but
35712 whose termination the daemon has not yet noticed. Thus, while it is possible to
35713 match up the opening and closing of connections in the log, the value of the
35714 logged counts may not be entirely accurate.
35716 .cindex "log" "SMTP transaction; incomplete"
35717 .cindex "SMTP" "logging incomplete transactions"
35718 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
35719 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
35720 and the message sender plus any accepted recipients are included in the log
35721 line. This can provide evidence of dictionary attacks.
35723 .cindex "log" "non-MAIL SMTP sessions"
35724 .cindex "MAIL" "logging session without"
35725 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
35726 connection terminates without having issued a MAIL command. This includes both
35727 the case when the connection is dropped, and the case when QUIT is used. It
35728 does not include cases where the connection is rejected right at the start (by
35729 an ACL, or because there are too many connections, or whatever). These cases
35730 already have their own log lines.
35732 The log line that is written contains the identity of the client in the usual
35733 way, followed by D= and a time, which records the duration of the connection.
35734 If the connection was authenticated, this fact is logged exactly as it is for
35735 an incoming message, with an A= item. If the connection was encrypted, CV=,
35736 DN=, and X= items may appear as they do for an incoming message, controlled by
35737 the same logging options.
35739 Finally, if any SMTP commands were issued during the connection, a C= item
35740 is added to the line, listing the commands that were used. For example,
35744 shows that the client issued QUIT straight after EHLO. If there were fewer
35745 than 20 commands, they are all listed. If there were more than 20 commands,
35746 the last 20 are listed, preceded by &"..."&. However, with the default
35747 setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
35748 have been aborted before 20 non-mail commands are processed.
35750 &%smtp_mailauth%&: A third subfield with the authenticated sender,
35751 colon-separated, is appended to the A= item for a message arrival or delivery
35752 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
35753 was accepted or used.
35755 .cindex "log" "SMTP protocol error"
35756 .cindex "SMTP" "logging protocol error"
35757 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
35758 encountered. Exim does not have perfect detection of all protocol errors
35759 because of transmission delays and the use of pipelining. If PIPELINING has
35760 been advertised to a client, an Exim server assumes that the client will use
35761 it, and therefore it does not count &"expected"& errors (for example, RCPT
35762 received after rejecting MAIL) as protocol errors.
35764 .cindex "SMTP" "logging syntax errors"
35765 .cindex "SMTP" "syntax errors; logging"
35766 .cindex "SMTP" "unknown command; logging"
35767 .cindex "log" "unknown SMTP command"
35768 .cindex "log" "SMTP syntax error"
35769 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
35770 encountered. An unrecognized command is treated as a syntax error. For an
35771 external connection, the host identity is given; for an internal connection
35772 using &%-bs%& the sender identification (normally the calling user) is given.
35774 .cindex "log" "subject"
35775 .cindex "subject, logging"
35776 &%subject%&: The subject of the message is added to the arrival log line,
35777 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
35778 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
35779 specifies whether characters with values greater than 127 should be logged
35780 unchanged, or whether they should be rendered as escape sequences.
35782 .cindex "log" "certificate verification"
35783 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
35784 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
35785 verified, and &`CV=no`& if not.
35787 .cindex "log" "TLS cipher"
35788 .cindex "TLS" "logging cipher"
35789 &%tls_cipher%&: When a message is sent or received over an encrypted
35790 connection, the cipher suite used is added to the log line, preceded by X=.
35792 .cindex "log" "TLS peer DN"
35793 .cindex "TLS" "logging peer DN"
35794 &%tls_peerdn%&: When a message is sent or received over an encrypted
35795 connection, and a certificate is supplied by the remote host, the peer DN is
35796 added to the log line, preceded by DN=.
35798 .cindex "log" "TLS SNI"
35799 .cindex "TLS" "logging SNI"
35800 &%tls_sni%&: When a message is received over an encrypted connection, and
35801 the remote host provided the Server Name Indication extension, the SNI is
35802 added to the log line, preceded by SNI=.
35804 .cindex "log" "DNS failure in list"
35805 &%unknown_in_list%&: This setting causes a log entry to be written when the
35806 result of a list match is failure because a DNS lookup failed.
35810 .section "Message log" "SECID260"
35811 .cindex "message" "log file for"
35812 .cindex "log" "message log; description of"
35813 .cindex "&_msglog_& directory"
35814 .oindex "&%preserve_message_logs%&"
35815 In addition to the general log files, Exim writes a log file for each message
35816 that it handles. The names of these per-message logs are the message ids, and
35817 they are kept in the &_msglog_& sub-directory of the spool directory. Each
35818 message log contains copies of the log lines that apply to the message. This
35819 makes it easier to inspect the status of an individual message without having
35820 to search the main log. A message log is deleted when processing of the message
35821 is complete, unless &%preserve_message_logs%& is set, but this should be used
35822 only with great care because they can fill up your disk very quickly.
35824 On a heavily loaded system, it may be desirable to disable the use of
35825 per-message logs, in order to reduce disk I/O. This can be done by setting the
35826 &%message_logs%& option false.
35832 . ////////////////////////////////////////////////////////////////////////////
35833 . ////////////////////////////////////////////////////////////////////////////
35835 .chapter "Exim utilities" "CHAPutils"
35836 .scindex IIDutils "utilities"
35837 A number of utility scripts and programs are supplied with Exim and are
35838 described in this chapter. There is also the Exim Monitor, which is covered in
35839 the next chapter. The utilities described here are:
35841 .itable none 0 0 3 7* left 15* left 40* left
35842 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
35843 "list what Exim processes are doing"
35844 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
35845 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
35846 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
35847 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
35849 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
35850 .irow &<<SECTmailstat>>& &'eximstats'& &&&
35851 "extract statistics from the log"
35852 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
35853 "check address acceptance from given IP"
35854 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
35855 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
35856 .irow &<<SECThindatmai>>& &'exim_dumpdb'& "dump a hints database"
35857 .irow &<<SECThindatmai>>& &'exim_tidydb'& "clean up a hints database"
35858 .irow &<<SECThindatmai>>& &'exim_fixdb'& "patch a hints database"
35859 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
35862 Another utility that might be of use to sites with many MTAs is Tom Kistner's
35863 &'exilog'&. It provides log visualizations across multiple Exim servers. See
35864 &url(http://duncanthrax.net/exilog/) for details.
35869 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
35870 .cindex "&'exiwhat'&"
35871 .cindex "process, querying"
35873 On operating systems that can restart a system call after receiving a signal
35874 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
35875 a line describing what it is doing to the file &_exim-process.info_& in the
35876 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
35877 processes it can find, having first emptied the file. It then waits for one
35878 second to allow the Exim processes to react before displaying the results. In
35879 order to run &'exiwhat'& successfully you have to have sufficient privilege to
35880 send the signal to the Exim processes, so it is normally run as root.
35882 &*Warning*&: This is not an efficient process. It is intended for occasional
35883 use by system administrators. It is not sensible, for example, to set up a
35884 script that sends SIGUSR1 signals to Exim processes at short intervals.
35887 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
35888 varies in different operating systems. Not only are different options used,
35889 but the format of the output is different. For this reason, there are some
35890 system configuration options that configure exactly how &'exiwhat'& works. If
35891 it doesn't seem to be working for you, check the following compile-time
35894 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
35895 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
35896 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
35897 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
35899 An example of typical output from &'exiwhat'& is
35901 164 daemon: -q1h, listening on port 25
35902 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
35903 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
35904 [10.19.42.42] (editor@ref.example)
35905 10592 handling incoming call from [192.168.243.242]
35906 10628 accepting a local non-SMTP message
35908 The first number in the output line is the process number. The third line has
35909 been split here, in order to fit it on the page.
35913 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
35914 .cindex "&'exiqgrep'&"
35915 .cindex "queue" "grepping"
35916 This utility is a Perl script contributed by Matt Hubbard. It runs
35920 or (in case &*-a*& switch is specified)
35924 The &*-C*& option is used to specify an alternate &_exim.conf_& which might
35925 contain alternate exim configuration the queue management might be using.
35927 to obtain a queue listing, and then greps the output to select messages
35928 that match given criteria. The following selection options are available:
35931 .vitem &*-f*&&~<&'regex'&>
35932 Match the sender address using a case-insensitive search. The field that is
35933 tested is enclosed in angle brackets, so you can test for bounce messages with
35937 .vitem &*-r*&&~<&'regex'&>
35938 Match a recipient address using a case-insensitive search. The field that is
35939 tested is not enclosed in angle brackets.
35941 .vitem &*-s*&&~<&'regex'&>
35942 Match against the size field.
35944 .vitem &*-y*&&~<&'seconds'&>
35945 Match messages that are younger than the given time.
35947 .vitem &*-o*&&~<&'seconds'&>
35948 Match messages that are older than the given time.
35951 Match only frozen messages.
35954 Match only non-frozen messages.
35957 The following options control the format of the output:
35961 Display only the count of matching messages.
35964 Long format &-- display the full message information as output by Exim. This is
35968 Display message ids only.
35971 Brief format &-- one line per message.
35974 Display messages in reverse order.
35977 Include delivered recipients in queue listing.
35980 There is one more option, &%-h%&, which outputs a list of options.
35984 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
35985 .cindex "&'exiqsumm'&"
35986 .cindex "queue" "summary"
35987 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
35988 -bp`& and produces a summary of the messages on the queue. Thus, you use it by
35989 running a command such as
35991 exim -bp | exiqsumm
35993 The output consists of one line for each domain that has messages waiting for
35994 it, as in the following example:
35996 3 2322 74m 66m msn.com.example
35998 Each line lists the number of pending deliveries for a domain, their total
35999 volume, and the length of time that the oldest and the newest messages have
36000 been waiting. Note that the number of pending deliveries is greater than the
36001 number of messages when messages have more than one recipient.
36003 A summary line is output at the end. By default the output is sorted on the
36004 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
36005 the output to be sorted by oldest message and by count of messages,
36006 respectively. There are also three options that split the messages for each
36007 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
36008 separates frozen messages, and &%-s%& separates messages according to their
36011 The output of &'exim -bp'& contains the original addresses in the message, so
36012 this also applies to the output from &'exiqsumm'&. No domains from addresses
36013 generated by aliasing or forwarding are included (unless the &%one_time%&
36014 option of the &(redirect)& router has been used to convert them into &"top
36015 level"& addresses).
36020 .section "Extracting specific information from the log (exigrep)" &&&
36022 .cindex "&'exigrep'&"
36023 .cindex "log" "extracts; grepping for"
36024 The &'exigrep'& utility is a Perl script that searches one or more main log
36025 files for entries that match a given pattern. When it finds a match, it
36026 extracts all the log entries for the relevant message, not just those that
36027 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
36028 given message, or all mail for a given user, or for a given host, for example.
36029 The input files can be in Exim log format or syslog format.
36030 If a matching log line is not associated with a specific message, it is
36031 included in &'exigrep'&'s output without any additional lines. The usage is:
36033 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
36035 If no log file names are given on the command line, the standard input is read.
36037 The &%-t%& argument specifies a number of seconds. It adds an additional
36038 condition for message selection. Messages that are complete are shown only if
36039 they spent more than <&'n'&> seconds on the queue.
36041 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
36042 makes it case-sensitive. This may give a performance improvement when searching
36043 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
36044 option; with &%-I%& they do not. In both cases it is possible to change the
36045 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
36047 The &%-l%& option means &"literal"&, that is, treat all characters in the
36048 pattern as standing for themselves. Otherwise the pattern must be a Perl
36049 regular expression.
36051 The &%-v%& option inverts the matching condition. That is, a line is selected
36052 if it does &'not'& match the pattern.
36054 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
36055 that are generated as a result/response to a message that &'exigrep'& matched
36059 user_a sends a message to user_b, which generates a bounce back to user_b. If
36060 &'exigrep'& is used to search for &"user_a"&, only the first message will be
36061 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
36062 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
36063 when searching for &"user_a"& will show both messages since the bounce is
36064 &"related"& to or a &"result"& of the first message that was found by the
36067 If the location of a &'zcat'& command is known from the definition of
36068 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
36069 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
36070 If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
36071 autodetection of some well known compression extensions.
36074 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
36075 .cindex "&'exipick'&"
36076 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
36077 lists messages from the queue according to a variety of criteria. For details
36078 of &'exipick'&'s facilities, visit the web page at
36079 &url(http://www.exim.org/eximwiki/ToolExipickManPage) or run &'exipick'& with
36080 the &%--help%& option.
36083 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
36084 .cindex "log" "cycling local files"
36085 .cindex "cycling logs"
36086 .cindex "&'exicyclog'&"
36087 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
36088 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
36089 you are using log files with datestamps in their names (see section
36090 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
36091 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
36092 There are two command line options for &'exicyclog'&:
36094 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
36095 default that is set when Exim is built. The default default is 10.
36097 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
36098 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
36099 overriding the script's default, which is to find the setting from Exim's
36103 Each time &'exicyclog'& is run the file names get &"shuffled down"& by one. If
36104 the main log file name is &_mainlog_& (the default) then when &'exicyclog'& is
36105 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
36106 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
36107 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
36108 logs are handled similarly.
36110 If the limit is greater than 99, the script uses 3-digit numbers such as
36111 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
36112 to one that is greater, or &'vice versa'&, you will have to fix the names of
36113 any existing log files.
36115 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
36116 the end are deleted. All files with numbers greater than 01 are compressed,
36117 using a compression command which is configured by the COMPRESS_COMMAND
36118 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
36119 root &%crontab%& entry of the form
36121 1 0 * * * su exim -c /usr/exim/bin/exicyclog
36123 assuming you have used the name &"exim"& for the Exim user. You can run
36124 &'exicyclog'& as root if you wish, but there is no need.
36128 .section "Mail statistics (eximstats)" "SECTmailstat"
36129 .cindex "statistics"
36130 .cindex "&'eximstats'&"
36131 A Perl script called &'eximstats'& is provided for extracting statistical
36132 information from log files. The output is either plain text, or HTML.
36133 Exim log files are also supported by the &'Lire'& system produced by the
36134 LogReport Foundation &url(http://www.logreport.org).
36136 The &'eximstats'& script has been hacked about quite a bit over time. The
36137 latest version is the result of some extensive revision by Steve Campbell. A
36138 lot of information is given by default, but there are options for suppressing
36139 various parts of it. Following any options, the arguments to the script are a
36140 list of files, which should be main log files. For example:
36142 eximstats -nr /var/spool/exim/log/mainlog.01
36144 By default, &'eximstats'& extracts information about the number and volume of
36145 messages received from or delivered to various hosts. The information is sorted
36146 both by message count and by volume, and the top fifty hosts in each category
36147 are listed on the standard output. Similar information, based on email
36148 addresses or domains instead of hosts can be requested by means of various
36149 options. For messages delivered and received locally, similar statistics are
36150 also produced per user.
36152 The output also includes total counts and statistics about delivery errors, and
36153 histograms showing the number of messages received and deliveries made in each
36154 hour of the day. A delivery with more than one address in its envelope (for
36155 example, an SMTP transaction with more than one RCPT command) is counted
36156 as a single delivery by &'eximstats'&.
36158 Though normally more deliveries than receipts are reported (as messages may
36159 have multiple recipients), it is possible for &'eximstats'& to report more
36160 messages received than delivered, even though the queue is empty at the start
36161 and end of the period in question. If an incoming message contains no valid
36162 recipients, no deliveries are recorded for it. A bounce message is handled as
36163 an entirely separate message.
36165 &'eximstats'& always outputs a grand total summary giving the volume and number
36166 of messages received and deliveries made, and the number of hosts involved in
36167 each case. It also outputs the number of messages that were delayed (that is,
36168 not completely delivered at the first attempt), and the number that had at
36169 least one address that failed.
36171 The remainder of the output is in sections that can be independently disabled
36172 or modified by various options. It consists of a summary of deliveries by
36173 transport, histograms of messages received and delivered per time interval
36174 (default per hour), information about the time messages spent on the queue,
36175 a list of relayed messages, lists of the top fifty sending hosts, local
36176 senders, destination hosts, and destination local users by count and by volume,
36177 and a list of delivery errors that occurred.
36179 The relay information lists messages that were actually relayed, that is, they
36180 came from a remote host and were directly delivered to some other remote host,
36181 without being processed (for example, for aliasing or forwarding) locally.
36183 There are quite a few options for &'eximstats'& to control exactly what it
36184 outputs. These are documented in the Perl script itself, and can be extracted
36185 by running the command &(perldoc)& on the script. For example:
36187 perldoc /usr/exim/bin/eximstats
36190 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
36191 .cindex "&'exim_checkaccess'&"
36192 .cindex "policy control" "checking access"
36193 .cindex "checking access"
36194 The &%-bh%& command line argument allows you to run a fake SMTP session with
36195 debugging output, in order to check what Exim is doing when it is applying
36196 policy controls to incoming SMTP mail. However, not everybody is sufficiently
36197 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
36198 sometimes you just want to answer the question &"Does this address have
36199 access?"& without bothering with any further details.
36201 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
36202 two arguments, an IP address and an email address:
36204 exim_checkaccess 10.9.8.7 A.User@a.domain.example
36206 The utility runs a call to Exim with the &%-bh%& option, to test whether the
36207 given email address would be accepted in a RCPT command in a TCP/IP
36208 connection from the host with the given IP address. The output of the utility
36209 is either the word &"accepted"&, or the SMTP error response, for example:
36212 550 Relay not permitted
36214 When running this test, the utility uses &`<>`& as the envelope sender address
36215 for the MAIL command, but you can change this by providing additional
36216 options. These are passed directly to the Exim command. For example, to specify
36217 that the test is to be run with the sender address &'himself@there.example'&
36220 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
36221 -f himself@there.example
36223 Note that these additional Exim command line items must be given after the two
36224 mandatory arguments.
36226 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
36227 while running its checks. You can run checks that include callouts by using
36228 &%-bhc%&, but this is not yet available in a &"packaged"& form.
36232 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
36233 .cindex "DBM" "building dbm files"
36234 .cindex "building DBM files"
36235 .cindex "&'exim_dbmbuild'&"
36236 .cindex "lower casing"
36237 .cindex "binary zero" "in lookup key"
36238 The &'exim_dbmbuild'& program reads an input file containing keys and data in
36239 the format used by the &(lsearch)& lookup (see section
36240 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
36241 names as keys and the remainder of the information as data. The lower-casing
36242 can be prevented by calling the program with the &%-nolc%& option.
36244 A terminating zero is included as part of the key string. This is expected by
36245 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
36246 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
36247 strings or the data strings. The &(dbmnz)& lookup type can be used with such
36250 The program requires two arguments: the name of the input file (which can be a
36251 single hyphen to indicate the standard input), and the name of the output file.
36252 It creates the output under a temporary name, and then renames it if all went
36256 If the native DB interface is in use (USE_DB is set in a compile-time
36257 configuration file &-- this is common in free versions of Unix) the two file
36258 names must be different, because in this mode the Berkeley DB functions create
36259 a single output file using exactly the name given. For example,
36261 exim_dbmbuild /etc/aliases /etc/aliases.db
36263 reads the system alias file and creates a DBM version of it in
36264 &_/etc/aliases.db_&.
36266 In systems that use the &'ndbm'& routines (mostly proprietary versions of
36267 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
36268 environment, the suffixes are added to the second argument of
36269 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
36270 when the Berkeley functions are used in compatibility mode (though this is not
36271 recommended), because in that case it adds a &_.db_& suffix to the file name.
36273 If a duplicate key is encountered, the program outputs a warning, and when it
36274 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
36275 option is used. By default, only the first of a set of duplicates is used &--
36276 this makes it compatible with &(lsearch)& lookups. There is an option
36277 &%-lastdup%& which causes it to use the data for the last duplicate instead.
36278 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
36279 &%stderr%&. For other errors, where it doesn't actually make a new file, the
36285 .section "Finding individual retry times (exinext)" "SECTfinindret"
36286 .cindex "retry" "times"
36287 .cindex "&'exinext'&"
36288 A utility called &'exinext'& (mostly a Perl script) provides the ability to
36289 fish specific information out of the retry database. Given a mail domain (or a
36290 complete address), it looks up the hosts for that domain, and outputs any retry
36291 information for the hosts or for the domain. At present, the retry information
36292 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
36293 output. For example:
36295 $ exinext piglet@milne.fict.example
36296 kanga.milne.example:192.168.8.1 error 146: Connection refused
36297 first failed: 21-Feb-1996 14:57:34
36298 last tried: 21-Feb-1996 14:57:34
36299 next try at: 21-Feb-1996 15:02:34
36300 roo.milne.example:192.168.8.3 error 146: Connection refused
36301 first failed: 20-Jan-1996 13:12:08
36302 last tried: 21-Feb-1996 11:42:03
36303 next try at: 21-Feb-1996 19:42:03
36304 past final cutoff time
36306 You can also give &'exinext'& a local part, without a domain, and it
36307 will give any retry information for that local part in your default domain.
36308 A message id can be used to obtain retry information pertaining to a specific
36309 message. This exists only when an attempt to deliver a message to a remote host
36310 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
36311 &'exinext'& is not particularly efficient, but then it is not expected to be
36314 The &'exinext'& utility calls Exim to find out information such as the location
36315 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
36316 passed on to the &'exim'& commands. The first specifies an alternate Exim
36317 configuration file, and the second sets macros for use within the configuration
36318 file. These features are mainly to help in testing, but might also be useful in
36319 environments where more than one configuration file is in use.
36323 .section "Hints database maintenance" "SECThindatmai"
36324 .cindex "hints database" "maintenance"
36325 .cindex "maintaining Exim's hints database"
36326 Three utility programs are provided for maintaining the DBM files that Exim
36327 uses to contain its delivery hint information. Each program requires two
36328 arguments. The first specifies the name of Exim's spool directory, and the
36329 second is the name of the database it is to operate on. These are as follows:
36332 &'retry'&: the database of retry information
36334 &'wait-'&<&'transport name'&>: databases of information about messages waiting
36337 &'callout'&: the callout cache
36339 &'ratelimit'&: the data for implementing the ratelimit ACL condition
36341 &'misc'&: other hints data
36344 The &'misc'& database is used for
36347 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
36349 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
36350 &(smtp)& transport)
36352 Limiting the concurrency of specific transports (when &%max_parallel%& is set
36358 .section "exim_dumpdb" "SECID261"
36359 .cindex "&'exim_dumpdb'&"
36360 The entire contents of a database are written to the standard output by the
36361 &'exim_dumpdb'& program, which has no options or arguments other than the
36362 spool and database names. For example, to dump the retry database:
36364 exim_dumpdb /var/spool/exim retry
36366 Two lines of output are produced for each entry:
36368 T:mail.ref.example:192.168.242.242 146 77 Connection refused
36369 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
36371 The first item on the first line is the key of the record. It starts with one
36372 of the letters R, or T, depending on whether it refers to a routing or
36373 transport retry. For a local delivery, the next part is the local address; for
36374 a remote delivery it is the name of the remote host, followed by its failing IP
36375 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
36376 transport). If the remote port is not the standard one (port 25), it is added
36377 to the IP address. Then there follows an error code, an additional error code,
36378 and a textual description of the error.
36380 The three times on the second line are the time of first failure, the time of
36381 the last delivery attempt, and the computed time for the next attempt. The line
36382 ends with an asterisk if the cutoff time for the last retry rule has been
36385 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
36386 consists of a host name followed by a list of ids for messages that are or were
36387 waiting to be delivered to that host. If there are a very large number for any
36388 one host, continuation records, with a sequence number added to the host name,
36389 may be seen. The data in these records is often out of date, because a message
36390 may be routed to several alternative hosts, and Exim makes no effort to keep
36395 .section "exim_tidydb" "SECID262"
36396 .cindex "&'exim_tidydb'&"
36397 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
36398 database. If run with no options, it removes all records that are more than 30
36399 days old. The age is calculated from the date and time that the record was last
36400 updated. Note that, in the case of the retry database, it is &'not'& the time
36401 since the first delivery failure. Information about a host that has been down
36402 for more than 30 days will remain in the database, provided that the record is
36403 updated sufficiently often.
36405 The cutoff date can be altered by means of the &%-t%& option, which must be
36406 followed by a time. For example, to remove all records older than a week from
36407 the retry database:
36409 exim_tidydb -t 7d /var/spool/exim retry
36411 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
36412 message ids. In the former these appear as data in records keyed by host &--
36413 they were messages that were waiting for that host &-- and in the latter they
36414 are the keys for retry information for messages that have suffered certain
36415 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
36416 message ids in database records are those of messages that are still on the
36417 queue. Message ids for messages that no longer exist are removed from
36418 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
36419 For the &'retry'& database, records whose keys are non-existent message ids are
36420 removed. The &'exim_tidydb'& utility outputs comments on the standard output
36421 whenever it removes information from the database.
36423 Certain records are automatically removed by Exim when they are no longer
36424 needed, but others are not. For example, if all the MX hosts for a domain are
36425 down, a retry record is created for each one. If the primary MX host comes back
36426 first, its record is removed when Exim successfully delivers to it, but the
36427 records for the others remain because Exim has not tried to use those hosts.
36429 It is important, therefore, to run &'exim_tidydb'& periodically on all the
36430 hints databases. You should do this at a quiet time of day, because it requires
36431 a database to be locked (and therefore inaccessible to Exim) while it does its
36432 work. Removing records from a DBM file does not normally make the file smaller,
36433 but all the common DBM libraries are able to re-use the space that is released.
36434 After an initial phase of increasing in size, the databases normally reach a
36435 point at which they no longer get any bigger, as long as they are regularly
36438 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
36439 databases is likely to keep on increasing.
36444 .section "exim_fixdb" "SECID263"
36445 .cindex "&'exim_fixdb'&"
36446 The &'exim_fixdb'& program is a utility for interactively modifying databases.
36447 Its main use is for testing Exim, but it might also be occasionally useful for
36448 getting round problems in a live system. It has no options, and its interface
36449 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
36450 key of a database record can then be entered, and the data for that record is
36453 If &"d"& is typed at the next prompt, the entire record is deleted. For all
36454 except the &'retry'& database, that is the only operation that can be carried
36455 out. For the &'retry'& database, each field is output preceded by a number, and
36456 data for individual fields can be changed by typing the field number followed
36457 by new data, for example:
36461 resets the time of the next delivery attempt. Time values are given as a
36462 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
36463 used as optional separators.
36468 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
36469 .cindex "mailbox" "maintenance"
36470 .cindex "&'exim_lock'&"
36471 .cindex "locking mailboxes"
36472 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
36473 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
36474 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
36475 a user agent while investigating a problem. The utility requires the name of
36476 the file as its first argument. If the locking is successful, the second
36477 argument is run as a command (using C's &[system()]& function); if there is no
36478 second argument, the value of the SHELL environment variable is used; if this
36479 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
36480 is unlocked and the utility ends. The following options are available:
36484 Use &[fcntl()]& locking on the open mailbox.
36487 Use &[flock()]& locking on the open mailbox, provided the operating system
36490 .vitem &%-interval%&
36491 This must be followed by a number, which is a number of seconds; it sets the
36492 interval to sleep between retries (default 3).
36494 .vitem &%-lockfile%&
36495 Create a lock file before opening the mailbox.
36498 Lock the mailbox using MBX rules.
36501 Suppress verification output.
36503 .vitem &%-retries%&
36504 This must be followed by a number; it sets the number of times to try to get
36505 the lock (default 10).
36507 .vitem &%-restore_time%&
36508 This option causes &%exim_lock%& to restore the modified and read times to the
36509 locked file before exiting. This allows you to access a locked mailbox (for
36510 example, to take a backup copy) without disturbing the times that the user
36513 .vitem &%-timeout%&
36514 This must be followed by a number, which is a number of seconds; it sets a
36515 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
36516 default), a non-blocking call is used.
36519 Generate verbose output.
36522 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
36523 default is to create a lock file and also to use &[fcntl()]& locking on the
36524 mailbox, which is the same as Exim's default. The use of &%-flock%& or
36525 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
36526 requires that the directory containing the file be writeable. Locking by lock
36527 file does not last for ever; Exim assumes that a lock file is expired if it is
36528 more than 30 minutes old.
36530 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
36531 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
36532 to be taken out on the open mailbox, and an exclusive lock on the file
36533 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
36534 number of the mailbox file. When the locking is released, if an exclusive lock
36535 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
36537 The default output contains verification of the locking that takes place. The
36538 &%-v%& option causes some additional information to be given. The &%-q%& option
36539 suppresses all output except error messages.
36543 exim_lock /var/spool/mail/spqr
36545 runs an interactive shell while the file is locked, whereas
36547 &`exim_lock -q /var/spool/mail/spqr <<End`&
36548 <&'some commands'&>
36551 runs a specific non-interactive sequence of commands while the file is locked,
36552 suppressing all verification output. A single command can be run by a command
36555 exim_lock -q /var/spool/mail/spqr \
36556 "cp /var/spool/mail/spqr /some/where"
36558 Note that if a command is supplied, it must be entirely contained within the
36559 second argument &-- hence the quotes.
36563 . ////////////////////////////////////////////////////////////////////////////
36564 . ////////////////////////////////////////////////////////////////////////////
36566 .chapter "The Exim monitor" "CHAPeximon"
36567 .scindex IIDeximon "Exim monitor" "description"
36568 .cindex "X-windows"
36569 .cindex "&'eximon'&"
36570 .cindex "Local/eximon.conf"
36571 .cindex "&_exim_monitor/EDITME_&"
36572 The Exim monitor is an application which displays in an X window information
36573 about the state of Exim's queue and what Exim is doing. An admin user can
36574 perform certain operations on messages from this GUI interface; however all
36575 such facilities are also available from the command line, and indeed, the
36576 monitor itself makes use of the command line to perform any actions requested.
36580 .section "Running the monitor" "SECID264"
36581 The monitor is started by running the script called &'eximon'&. This is a shell
36582 script that sets up a number of environment variables, and then runs the
36583 binary called &_eximon.bin_&. The default appearance of the monitor window can
36584 be changed by editing the &_Local/eximon.conf_& file created by editing
36585 &_exim_monitor/EDITME_&. Comments in that file describe what the various
36586 parameters are for.
36588 The parameters that get built into the &'eximon'& script can be overridden for
36589 a particular invocation by setting up environment variables of the same names,
36590 preceded by &`EXIMON_`&. For example, a shell command such as
36592 EXIMON_LOG_DEPTH=400 eximon
36594 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
36595 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
36596 overrides the Exim log file configuration. This makes it possible to have
36597 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
36598 syslog messages are routed to a file on the local host.
36600 X resources can be used to change the appearance of the window in the normal
36601 way. For example, a resource setting of the form
36603 Eximon*background: gray94
36605 changes the colour of the background to light grey rather than white. The
36606 stripcharts are drawn with both the data lines and the reference lines in
36607 black. This means that the reference lines are not visible when on top of the
36608 data. However, their colour can be changed by setting a resource called
36609 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
36610 For example, if your X server is running Unix, you could set up lighter
36611 reference lines in the stripcharts by obeying
36614 Eximon*highlight: gray
36617 .cindex "admin user"
36618 In order to see the contents of messages on the queue, and to operate on them,
36619 &'eximon'& must either be run as root or by an admin user.
36621 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
36622 contain X11 resource parameters interpreted by the X11 library. In addition,
36623 if the first parameter starts with the string "gdb" then it is removed and the
36624 binary is invoked under gdb (the parameter is used as the gdb command-name, so
36625 versioned variants of gdb can be invoked).
36627 The monitor's window is divided into three parts. The first contains one or
36628 more stripcharts and two action buttons, the second contains a &"tail"& of the
36629 main log file, and the third is a display of the queue of messages awaiting
36630 delivery, with two more action buttons. The following sections describe these
36631 different parts of the display.
36636 .section "The stripcharts" "SECID265"
36637 .cindex "stripchart"
36638 The first stripchart is always a count of messages on the queue. Its name can
36639 be configured by setting QUEUE_STRIPCHART_NAME in the
36640 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
36641 configuration script by regular expression matches on log file entries, making
36642 it possible to display, for example, counts of messages delivered to certain
36643 hosts or using certain transports. The supplied defaults display counts of
36644 received and delivered messages, and of local and SMTP deliveries. The default
36645 period between stripchart updates is one minute; this can be adjusted by a
36646 parameter in the &_Local/eximon.conf_& file.
36648 The stripchart displays rescale themselves automatically as the value they are
36649 displaying changes. There are always 10 horizontal lines in each chart; the
36650 title string indicates the value of each division when it is greater than one.
36651 For example, &"x2"& means that each division represents a value of 2.
36653 It is also possible to have a stripchart which shows the percentage fullness of
36654 a particular disk partition, which is useful when local deliveries are confined
36655 to a single partition.
36657 .cindex "&%statvfs%& function"
36658 This relies on the availability of the &[statvfs()]& function or equivalent in
36659 the operating system. Most, but not all versions of Unix that support Exim have
36660 this. For this particular stripchart, the top of the chart always represents
36661 100%, and the scale is given as &"x10%"&. This chart is configured by setting
36662 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
36663 &_Local/eximon.conf_& file.
36668 .section "Main action buttons" "SECID266"
36669 .cindex "size" "of monitor window"
36670 .cindex "Exim monitor" "window size"
36671 .cindex "window size"
36672 Below the stripcharts there is an action button for quitting the monitor. Next
36673 to this is another button marked &"Size"&. They are placed here so that
36674 shrinking the window to its default minimum size leaves just the queue count
36675 stripchart and these two buttons visible. Pressing the &"Size"& button causes
36676 the window to expand to its maximum size, unless it is already at the maximum,
36677 in which case it is reduced to its minimum.
36679 When expanding to the maximum, if the window cannot be fully seen where it
36680 currently is, it is moved back to where it was the last time it was at full
36681 size. When it is expanding from its minimum size, the old position is
36682 remembered, and next time it is reduced to the minimum it is moved back there.
36684 The idea is that you can keep a reduced window just showing one or two
36685 stripcharts at a convenient place on your screen, easily expand it to show
36686 the full window when required, and just as easily put it back to what it was.
36687 The idea is copied from what the &'twm'& window manager does for its
36688 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
36689 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
36691 Normally, the monitor starts up with the window at its full size, but it can be
36692 built so that it starts up with the window at its smallest size, by setting
36693 START_SMALL=yes in &_Local/eximon.conf_&.
36697 .section "The log display" "SECID267"
36698 .cindex "log" "tail of; in monitor"
36699 The second section of the window is an area in which a display of the tail of
36700 the main log is maintained.
36701 To save space on the screen, the timestamp on each log line is shortened by
36702 removing the date and, if &%log_timezone%& is set, the timezone.
36703 The log tail is not available when the only destination for logging data is
36704 syslog, unless the syslog lines are routed to a local file whose name is passed
36705 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
36707 The log sub-window has a scroll bar at its lefthand side which can be used to
36708 move back to look at earlier text, and the up and down arrow keys also have a
36709 scrolling effect. The amount of log that is kept depends on the setting of
36710 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
36711 to use. When this is full, the earlier 50% of data is discarded &-- this is
36712 much more efficient than throwing it away line by line. The sub-window also has
36713 a horizontal scroll bar for accessing the ends of long log lines. This is the
36714 only means of horizontal scrolling; the right and left arrow keys are not
36715 available. Text can be cut from this part of the window using the mouse in the
36716 normal way. The size of this subwindow is controlled by parameters in the
36717 configuration file &_Local/eximon.conf_&.
36719 Searches of the text in the log window can be carried out by means of the ^R
36720 and ^S keystrokes, which default to a reverse and a forward search,
36721 respectively. The search covers only the text that is displayed in the window.
36722 It cannot go further back up the log.
36724 The point from which the search starts is indicated by a caret marker. This is
36725 normally at the end of the text in the window, but can be positioned explicitly
36726 by pointing and clicking with the left mouse button, and is moved automatically
36727 by a successful search. If new text arrives in the window when it is scrolled
36728 back, the caret remains where it is, but if the window is not scrolled back,
36729 the caret is moved to the end of the new text.
36731 Pressing ^R or ^S pops up a window into which the search text can be typed.
36732 There are buttons for selecting forward or reverse searching, for carrying out
36733 the search, and for cancelling. If the &"Search"& button is pressed, the search
36734 happens and the window remains so that further searches can be done. If the
36735 &"Return"& key is pressed, a single search is done and the window is closed. If
36736 ^C is typed the search is cancelled.
36738 The searching facility is implemented using the facilities of the Athena text
36739 widget. By default this pops up a window containing both &"search"& and
36740 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
36741 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
36742 However, the linkers in BSDI and HP-UX seem unable to handle an externally
36743 provided version of &%TextPop%& when the remaining parts of the text widget
36744 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
36745 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
36746 on these systems, at the expense of having unwanted items in the search popup
36751 .section "The queue display" "SECID268"
36752 .cindex "queue" "display in monitor"
36753 The bottom section of the monitor window contains a list of all messages that
36754 are on the queue, which includes those currently being received or delivered,
36755 as well as those awaiting delivery. The size of this subwindow is controlled by
36756 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
36757 at which it is updated is controlled by another parameter in the same file &--
36758 the default is 5 minutes, since queue scans can be quite expensive. However,
36759 there is an &"Update"& action button just above the display which can be used
36760 to force an update of the queue display at any time.
36762 When a host is down for some time, a lot of pending mail can build up for it,
36763 and this can make it hard to deal with other messages on the queue. To help
36764 with this situation there is a button next to &"Update"& called &"Hide"&. If
36765 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
36766 type anything in here and press &"Return"&, the text is added to a chain of
36767 such texts, and if every undelivered address in a message matches at least one
36768 of the texts, the message is not displayed.
36770 If there is an address that does not match any of the texts, all the addresses
36771 are displayed as normal. The matching happens on the ends of addresses so, for
36772 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
36773 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
36774 has been set up, a button called &"Unhide"& is displayed. If pressed, it
36775 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
36776 a hide request is automatically cancelled after one hour.
36778 While the dialogue box is displayed, you can't press any buttons or do anything
36779 else to the monitor window. For this reason, if you want to cut text from the
36780 queue display to use in the dialogue box, you have to do the cutting before
36781 pressing the &"Hide"& button.
36783 The queue display contains, for each unhidden queued message, the length of
36784 time it has been on the queue, the size of the message, the message id, the
36785 message sender, and the first undelivered recipient, all on one line. If it is
36786 a bounce message, the sender is shown as &"<>"&. If there is more than one
36787 recipient to which the message has not yet been delivered, subsequent ones are
36788 listed on additional lines, up to a maximum configured number, following which
36789 an ellipsis is displayed. Recipients that have already received the message are
36792 .cindex "frozen messages" "display"
36793 If a message is frozen, an asterisk is displayed at the left-hand side.
36795 The queue display has a vertical scroll bar, and can also be scrolled by means
36796 of the arrow keys. Text can be cut from it using the mouse in the normal way.
36797 The text searching facilities, as described above for the log window, are also
36798 available, but the caret is always moved to the end of the text when the queue
36799 display is updated.
36803 .section "The queue menu" "SECID269"
36804 .cindex "queue" "menu in monitor"
36805 If the &%shift%& key is held down and the left button is clicked when the mouse
36806 pointer is over the text for any message, an action menu pops up, and the first
36807 line of the queue display for the message is highlighted. This does not affect
36810 If you want to use some other event for popping up the menu, you can set the
36811 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
36812 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
36813 value set in this parameter is a standard X event description. For example, to
36814 run eximon using &%ctrl%& rather than &%shift%& you could use
36816 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
36818 The title of the menu is the message id, and it contains entries which act as
36822 &'message log'&: The contents of the message log for the message are displayed
36823 in a new text window.
36825 &'headers'&: Information from the spool file that contains the envelope
36826 information and headers is displayed in a new text window. See chapter
36827 &<<CHAPspool>>& for a description of the format of spool files.
36829 &'body'&: The contents of the spool file containing the body of the message are
36830 displayed in a new text window. There is a default limit of 20,000 bytes to the
36831 amount of data displayed. This can be changed by setting the BODY_MAX
36832 option at compile time, or the EXIMON_BODY_MAX option at run time.
36834 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
36835 delivery of the message. This causes an automatic thaw if the message is
36836 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
36837 a new text window. The delivery is run in a separate process, to avoid holding
36838 up the monitor while the delivery proceeds.
36840 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
36841 that the message be frozen.
36843 .cindex "thawing messages"
36844 .cindex "unfreezing messages"
36845 .cindex "frozen messages" "thawing"
36846 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
36847 that the message be thawed.
36849 .cindex "delivery" "forcing failure"
36850 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
36851 that Exim gives up trying to deliver the message. A bounce message is generated
36852 for any remaining undelivered addresses.
36854 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
36855 that the message be deleted from the system without generating a bounce
36858 &'add recipient'&: A dialog box is displayed into which a recipient address can
36859 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
36860 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
36861 Otherwise it must be entered as a fully qualified address. Pressing RETURN
36862 causes a call to Exim to be made using the &%-Mar%& option to request that an
36863 additional recipient be added to the message, unless the entry box is empty, in
36864 which case no action is taken.
36866 &'mark delivered'&: A dialog box is displayed into which a recipient address
36867 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
36868 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
36869 Otherwise it must be entered as a fully qualified address. Pressing RETURN
36870 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
36871 recipient address as already delivered, unless the entry box is empty, in which
36872 case no action is taken.
36874 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
36875 mark all recipient addresses as already delivered.
36877 &'edit sender'&: A dialog box is displayed initialized with the current
36878 sender's address. Pressing RETURN causes a call to Exim to be made using the
36879 &%-Mes%& option to replace the sender address, unless the entry box is empty,
36880 in which case no action is taken. If you want to set an empty sender (as in
36881 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
36882 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
36883 the address is qualified with that domain.
36886 When a delivery is forced, a window showing the &%-v%& output is displayed. In
36887 other cases when a call to Exim is made, if there is any output from Exim (in
36888 particular, if the command fails) a window containing the command and the
36889 output is displayed. Otherwise, the results of the action are normally apparent
36890 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
36891 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
36892 if no output is generated.
36894 The queue display is automatically updated for actions such as freezing and
36895 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
36896 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
36897 force an update of the display after one of these actions.
36899 In any text window that is displayed as result of a menu action, the normal
36900 cut-and-paste facility is available, and searching can be carried out using ^R
36901 and ^S, as described above for the log tail window.
36908 . ////////////////////////////////////////////////////////////////////////////
36909 . ////////////////////////////////////////////////////////////////////////////
36911 .chapter "Security considerations" "CHAPsecurity"
36912 .scindex IIDsecurcon "security" "discussion of"
36913 This chapter discusses a number of issues concerned with security, some of
36914 which are also covered in other parts of this manual.
36916 For reasons that this author does not understand, some people have promoted
36917 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
36918 existence of this chapter in the documentation. However, the intent of the
36919 chapter is simply to describe the way Exim works in relation to certain
36920 security concerns, not to make any specific claims about the effectiveness of
36921 its security as compared with other MTAs.
36923 What follows is a description of the way Exim is supposed to be. Best efforts
36924 have been made to try to ensure that the code agrees with the theory, but an
36925 absence of bugs can never be guaranteed. Any that are reported will get fixed
36926 as soon as possible.
36929 .section "Building a more &""hardened""& Exim" "SECID286"
36930 .cindex "security" "build-time features"
36931 There are a number of build-time options that can be set in &_Local/Makefile_&
36932 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
36933 Exim administrator who does not have the root password, or by someone who has
36934 penetrated the Exim (but not the root) account. These options are as follows:
36937 ALT_CONFIG_PREFIX can be set to a string that is required to match the
36938 start of any file names used with the &%-C%& option. When it is set, these file
36939 names are also not allowed to contain the sequence &"/../"&. (However, if the
36940 value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
36941 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
36942 default setting for &%ALT_CONFIG_PREFIX%&.
36944 If the permitted configuration files are confined to a directory to
36945 which only root has access, this guards against someone who has broken
36946 into the Exim account from running a privileged Exim with an arbitrary
36947 configuration file, and using it to break into other accounts.
36950 If a non-trusted configuration file (i.e. not the default configuration file
36951 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
36952 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
36953 the next item), then root privilege is retained only if the caller of Exim is
36954 root. This locks out the possibility of testing a configuration using &%-C%&
36955 right through message reception and delivery, even if the caller is root. The
36956 reception works, but by that time, Exim is running as the Exim user, so when
36957 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
36958 privilege to be lost. However, root can test reception and delivery using two
36962 The WHITELIST_D_MACROS build option declares some macros to be safe to override
36963 with &%-D%& if the real uid is one of root, the Exim run-time user or the
36964 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
36965 requiring the run-time value supplied to &%-D%& to match a regex that errs on
36966 the restrictive side. Requiring build-time selection of safe macros is onerous
36967 but this option is intended solely as a transition mechanism to permit
36968 previously-working configurations to continue to work after release 4.73.
36970 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
36973 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
36974 never to be used for any deliveries. This is like the &%never_users%& runtime
36975 option, but it cannot be overridden; the runtime option adds additional users
36976 to the list. The default setting is &"root"&; this prevents a non-root user who
36977 is permitted to modify the runtime file from using Exim as a way to get root.
36982 .section "Root privilege" "SECID270"
36984 .cindex "root privilege"
36985 The Exim binary is normally setuid to root, which means that it gains root
36986 privilege (runs as root) when it starts execution. In some special cases (for
36987 example, when the daemon is not in use and there are no local deliveries), it
36988 may be possible to run Exim setuid to some user other than root. This is
36989 discussed in the next section. However, in most installations, root privilege
36990 is required for two things:
36993 To set up a socket connected to the standard SMTP port (25) when initialising
36994 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
36997 To be able to change uid and gid in order to read users' &_.forward_& files and
36998 perform local deliveries as the receiving user or as specified in the
37002 It is not necessary to be root to do any of the other things Exim does, such as
37003 receiving messages and delivering them externally over SMTP, and it is
37004 obviously more secure if Exim does not run as root except when necessary.
37005 For this reason, a user and group for Exim to use must be defined in
37006 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
37007 group"&. Their values can be changed by the run time configuration, though this
37008 is not recommended. Often a user called &'exim'& is used, but some sites use
37009 &'mail'& or another user name altogether.
37011 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
37012 abdication; the process cannot regain root afterwards. Prior to release 4.00,
37013 &[seteuid()]& was used in some circumstances, but this is no longer the case.
37015 After a new Exim process has interpreted its command line options, it changes
37016 uid and gid in the following cases:
37021 If the &%-C%& option is used to specify an alternate configuration file, or if
37022 the &%-D%& option is used to define macro values for the configuration, and the
37023 calling process is not running as root, the uid and gid are changed to those of
37024 the calling process.
37025 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
37026 option may not be used at all.
37027 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
37028 can be supplied if the calling process is running as root, the Exim run-time
37029 user or CONFIGURE_OWNER, if defined.
37034 If the expansion test option (&%-be%&) or one of the filter testing options
37035 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
37038 If the process is not a daemon process or a queue runner process or a delivery
37039 process or a process for testing address routing (started with &%-bt%&), the
37040 uid and gid are changed to the Exim user and group. This means that Exim always
37041 runs under its own uid and gid when receiving messages. This also applies when
37042 testing address verification
37045 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
37048 For a daemon, queue runner, delivery, or address testing process, the uid
37049 remains as root at this stage, but the gid is changed to the Exim group.
37052 The processes that initially retain root privilege behave as follows:
37055 A daemon process changes the gid to the Exim group and the uid to the Exim
37056 user after setting up one or more listening sockets. The &[initgroups()]&
37057 function is called, so that if the Exim user is in any additional groups, they
37058 will be used during message reception.
37060 A queue runner process retains root privilege throughout its execution. Its
37061 job is to fork a controlled sequence of delivery processes.
37063 A delivery process retains root privilege throughout most of its execution,
37064 but any actual deliveries (that is, the transports themselves) are run in
37065 subprocesses which always change to a non-root uid and gid. For local
37066 deliveries this is typically the uid and gid of the owner of the mailbox; for
37067 remote deliveries, the Exim uid and gid are used. Once all the delivery
37068 subprocesses have been run, a delivery process changes to the Exim uid and gid
37069 while doing post-delivery tidying up such as updating the retry database and
37070 generating bounce and warning messages.
37072 While the recipient addresses in a message are being routed, the delivery
37073 process runs as root. However, if a user's filter file has to be processed,
37074 this is done in a subprocess that runs under the individual user's uid and
37075 gid. A system filter is run as root unless &%system_filter_user%& is set.
37077 A process that is testing addresses (the &%-bt%& option) runs as root so that
37078 the routing is done in the same environment as a message delivery.
37084 .section "Running Exim without privilege" "SECTrunexiwitpri"
37085 .cindex "privilege, running without"
37086 .cindex "unprivileged running"
37087 .cindex "root privilege" "running without"
37088 Some installations like to run Exim in an unprivileged state for more of its
37089 operation, for added security. Support for this mode of operation is provided
37090 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
37091 gid are changed to the Exim user and group at the start of a delivery process
37092 (and also queue runner and address testing processes). This means that address
37093 routing is no longer run as root, and the deliveries themselves cannot change
37097 .cindex "daemon" "restarting"
37098 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
37099 that the daemon can still be started in the usual way, and it can respond
37100 correctly to SIGHUP because the re-invocation regains root privilege.
37102 An alternative approach is to make Exim setuid to the Exim user and also setgid
37103 to the Exim group. If you do this, the daemon must be started from a root
37104 process. (Calling Exim from a root process makes it behave in the way it does
37105 when it is setuid root.) However, the daemon cannot restart itself after a
37106 SIGHUP signal because it cannot regain privilege.
37108 It is still useful to set &%deliver_drop_privilege%& in this case, because it
37109 stops Exim from trying to re-invoke itself to do a delivery after a message has
37110 been received. Such a re-invocation is a waste of resources because it has no
37113 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
37114 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
37115 to the Exim user seems a clean approach, but there is one complication:
37117 In this style of operation, Exim is running with the real uid and gid set to
37118 those of the calling process, and the effective uid/gid set to Exim's values.
37119 Ideally, any association with the calling process' uid/gid should be dropped,
37120 that is, the real uid/gid should be reset to the effective values so as to
37121 discard any privileges that the caller may have. While some operating systems
37122 have a function that permits this action for a non-root effective uid, quite a
37123 number of them do not. Because of this lack of standardization, Exim does not
37124 address this problem at this time.
37126 For this reason, the recommended approach for &"mostly unprivileged"& running
37127 is to keep the Exim binary setuid to root, and to set
37128 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
37129 be used in the most straightforward way.
37131 If you configure Exim not to run delivery processes as root, there are a
37132 number of restrictions on what you can do:
37135 You can deliver only as the Exim user/group. You should explicitly use the
37136 &%user%& and &%group%& options to override routers or local transports that
37137 normally deliver as the recipient. This makes sure that configurations that
37138 work in this mode function the same way in normal mode. Any implicit or
37139 explicit specification of another user causes an error.
37141 Use of &_.forward_& files is severely restricted, such that it is usually
37142 not worthwhile to include them in the configuration.
37144 Users who wish to use &_.forward_& would have to make their home directory and
37145 the file itself accessible to the Exim user. Pipe and append-to-file entries,
37146 and their equivalents in Exim filters, cannot be used. While they could be
37147 enabled in the Exim user's name, that would be insecure and not very useful.
37149 Unless the local user mailboxes are all owned by the Exim user (possible in
37150 some POP3 or IMAP-only environments):
37153 They must be owned by the Exim group and be writeable by that group. This
37154 implies you must set &%mode%& in the appendfile configuration, as well as the
37155 mode of the mailbox files themselves.
37157 You must set &%no_check_owner%&, since most or all of the files will not be
37158 owned by the Exim user.
37160 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
37161 on a newly created mailbox when unprivileged. This also implies that new
37162 mailboxes need to be created manually.
37167 These restrictions severely restrict what can be done in local deliveries.
37168 However, there are no restrictions on remote deliveries. If you are running a
37169 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
37170 gives more security at essentially no cost.
37172 If you are using the &%mua_wrapper%& facility (see chapter
37173 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
37178 .section "Delivering to local files" "SECID271"
37179 Full details of the checks applied by &(appendfile)& before it writes to a file
37180 are given in chapter &<<CHAPappendfile>>&.
37184 .section "Running local commands" "SECTsecconslocalcmds"
37185 .cindex "security" "local commands"
37186 .cindex "security" "command injection attacks"
37187 There are a number of ways in which an administrator can configure Exim to run
37188 commands based upon received, untrustworthy, data. Further, in some
37189 configurations a user who can control a &_.forward_& file can also arrange to
37190 run commands. Configuration to check includes, but is not limited to:
37193 Use of &%use_shell%& in the pipe transport: various forms of shell command
37194 injection may be possible with this option present. It is dangerous and should
37195 be used only with considerable caution. Consider constraints which whitelist
37196 allowed characters in a variable which is to be used in a pipe transport that
37197 has &%use_shell%& enabled.
37199 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
37200 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
37201 &_.forward_& files in a redirect router. If Exim is running on a central mail
37202 hub to which ordinary users do not have shell access, but home directories are
37203 NFS mounted (for instance) then administrators should review the list of these
37204 forbid options available, and should bear in mind that the options that may
37205 need forbidding can change as new features are added between releases.
37207 The &%${run...}%& expansion item does not use a shell by default, but
37208 administrators can configure use of &_/bin/sh_& as part of the command.
37209 Such invocations should be viewed with prejudicial suspicion.
37211 Administrators who use embedded Perl are advised to explore how Perl's
37212 taint checking might apply to their usage.
37214 Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
37215 administrators are well advised to view its use with suspicion, in case (for
37216 instance) it allows a local-part to contain embedded Exim directives.
37218 Use of &%${match_local_part...}%& and friends becomes more dangerous if
37219 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
37220 each can reference arbitrary lists and files, rather than just being a list
37222 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
37223 real-world security vulnerabilities caused by its use with untrustworthy data
37224 injected in, for SQL injection attacks.
37225 Consider the use of the &%inlisti%& expansion condition instead.
37231 .section "Trust in configuration data" "SECTsecconfdata"
37232 .cindex "security" "data sources"
37233 .cindex "security" "regular expressions"
37234 .cindex "regular expressions" "security"
37235 .cindex "PCRE" "security"
37236 If configuration data for Exim can come from untrustworthy sources, there
37237 are some issues to be aware of:
37240 Use of &%${expand...}%& may provide a path for shell injection attacks.
37242 Letting untrusted data provide a regular expression is unwise.
37244 Using &%${match...}%& to apply a fixed regular expression against untrusted
37245 data may result in pathological behaviour within PCRE. Be aware of what
37246 "backtracking" means and consider options for being more strict with a regular
37247 expression. Avenues to explore include limiting what can match (avoiding &`.`&
37248 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
37249 possessive quantifiers or just not using regular expressions against untrusted
37252 It can be important to correctly use &%${quote:...}%&,
37253 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
37254 items to ensure that data is correctly constructed.
37256 Some lookups might return multiple results, even though normal usage is only
37257 expected to yield one result.
37263 .section "IPv4 source routing" "SECID272"
37264 .cindex "source routing" "in IP packets"
37265 .cindex "IP source routing"
37266 Many operating systems suppress IP source-routed packets in the kernel, but
37267 some cannot be made to do this, so Exim does its own check. It logs incoming
37268 IPv4 source-routed TCP calls, and then drops them. Things are all different in
37269 IPv6. No special checking is currently done.
37273 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
37274 Support for these SMTP commands is disabled by default. If required, they can
37275 be enabled by defining suitable ACLs.
37280 .section "Privileged users" "SECID274"
37281 .cindex "trusted users"
37282 .cindex "admin user"
37283 .cindex "privileged user"
37284 .cindex "user" "trusted"
37285 .cindex "user" "admin"
37286 Exim recognizes two sets of users with special privileges. Trusted users are
37287 able to submit new messages to Exim locally, but supply their own sender
37288 addresses and information about a sending host. For other users submitting
37289 local messages, Exim sets up the sender address from the uid, and doesn't
37290 permit a remote host to be specified.
37293 However, an untrusted user is permitted to use the &%-f%& command line option
37294 in the special form &%-f <>%& to indicate that a delivery failure for the
37295 message should not cause an error report. This affects the message's envelope,
37296 but it does not affect the &'Sender:'& header. Untrusted users may also be
37297 permitted to use specific forms of address with the &%-f%& option by setting
37298 the &%untrusted_set_sender%& option.
37300 Trusted users are used to run processes that receive mail messages from some
37301 other mail domain and pass them on to Exim for delivery either locally, or over
37302 the Internet. Exim trusts a caller that is running as root, as the Exim user,
37303 as any user listed in the &%trusted_users%& configuration option, or under any
37304 group listed in the &%trusted_groups%& option.
37306 Admin users are permitted to do things to the messages on Exim's queue. They
37307 can freeze or thaw messages, cause them to be returned to their senders, remove
37308 them entirely, or modify them in various ways. In addition, admin users can run
37309 the Exim monitor and see all the information it is capable of providing, which
37310 includes the contents of files on the spool.
37314 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
37315 delivery of messages on its queue is restricted to admin users. This
37316 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
37317 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
37318 queue is also restricted to admin users. This restriction can be relaxed by
37319 setting &%no_queue_list_requires_admin%&.
37321 Exim recognizes an admin user if the calling process is running as root or as
37322 the Exim user or if any of the groups associated with the calling process is
37323 the Exim group. It is not necessary actually to be running under the Exim
37324 group. However, if admin users who are not root or the Exim user are to access
37325 the contents of files on the spool via the Exim monitor (which runs
37326 unprivileged), Exim must be built to allow group read access to its spool
37331 .section "Spool files" "SECID275"
37332 .cindex "spool directory" "files"
37333 Exim's spool directory and everything it contains is owned by the Exim user and
37334 set to the Exim group. The mode for spool files is defined in the
37335 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
37336 any user who is a member of the Exim group can access these files.
37340 .section "Use of argv[0]" "SECID276"
37341 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
37342 of specific strings, Exim assumes certain options. For example, calling Exim
37343 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
37344 to calling it with the option &%-bS%&. There are no security implications in
37349 .section "Use of %f formatting" "SECID277"
37350 The only use made of &"%f"& by Exim is in formatting load average values. These
37351 are actually stored in integer variables as 1000 times the load average.
37352 Consequently, their range is limited and so therefore is the length of the
37357 .section "Embedded Exim path" "SECID278"
37358 Exim uses its own path name, which is embedded in the code, only when it needs
37359 to re-exec in order to regain root privilege. Therefore, it is not root when it
37360 does so. If some bug allowed the path to get overwritten, it would lead to an
37361 arbitrary program's being run as exim, not as root.
37365 .section "Dynamic module directory" "SECTdynmoddir"
37366 Any dynamically loadable modules must be installed into the directory
37367 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
37371 .section "Use of sprintf()" "SECID279"
37372 .cindex "&[sprintf()]&"
37373 A large number of occurrences of &"sprintf"& in the code are actually calls to
37374 &'string_sprintf()'&, a function that returns the result in malloc'd store.
37375 The intermediate formatting is done into a large fixed buffer by a function
37376 that runs through the format string itself, and checks the length of each
37377 conversion before performing it, thus preventing buffer overruns.
37379 The remaining uses of &[sprintf()]& happen in controlled circumstances where
37380 the output buffer is known to be sufficiently long to contain the converted
37385 .section "Use of debug_printf() and log_write()" "SECID280"
37386 Arbitrary strings are passed to both these functions, but they do their
37387 formatting by calling the function &'string_vformat()'&, which runs through
37388 the format string itself, and checks the length of each conversion.
37392 .section "Use of strcat() and strcpy()" "SECID281"
37393 These are used only in cases where the output buffer is known to be large
37394 enough to hold the result.
37395 .ecindex IIDsecurcon
37400 . ////////////////////////////////////////////////////////////////////////////
37401 . ////////////////////////////////////////////////////////////////////////////
37403 .chapter "Format of spool files" "CHAPspool"
37404 .scindex IIDforspo1 "format" "spool files"
37405 .scindex IIDforspo2 "spool directory" "format of files"
37406 .scindex IIDforspo3 "spool files" "format of"
37407 .cindex "spool files" "editing"
37408 A message on Exim's queue consists of two files, whose names are the message id
37409 followed by -D and -H, respectively. The data portion of the message is kept in
37410 the -D file on its own. The message's envelope, status, and headers are all
37411 kept in the -H file, whose format is described in this chapter. Each of these
37412 two files contains the final component of its own name as its first line. This
37413 is insurance against disk crashes where the directory is lost but the files
37414 themselves are recoverable.
37416 Some people are tempted into editing -D files in order to modify messages. You
37417 need to be extremely careful if you do this; it is not recommended and you are
37418 on your own if you do it. Here are some of the pitfalls:
37421 You must ensure that Exim does not try to deliver the message while you are
37422 fiddling with it. The safest way is to take out a write lock on the -D file,
37423 which is what Exim itself does, using &[fcntl()]&. If you update the file in
37424 place, the lock will be retained. If you write a new file and rename it, the
37425 lock will be lost at the instant of rename.
37427 .vindex "&$body_linecount$&"
37428 If you change the number of lines in the file, the value of
37429 &$body_linecount$&, which is stored in the -H file, will be incorrect. At
37430 present, this value is not used by Exim, but there is no guarantee that this
37431 will always be the case.
37433 If the message is in MIME format, you must take care not to break it.
37435 If the message is cryptographically signed, any change will invalidate the
37438 All in all, modifying -D files is fraught with danger.
37440 Files whose names end with -J may also be seen in the &_input_& directory (or
37441 its subdirectories when &%split_spool_directory%& is set). These are journal
37442 files, used to record addresses to which the message has been delivered during
37443 the course of a delivery attempt. If there are still undelivered recipients at
37444 the end, the -H file is updated, and the -J file is deleted. If, however, there
37445 is some kind of crash (for example, a power outage) before this happens, the -J
37446 file remains in existence. When Exim next processes the message, it notices the
37447 -J file and uses it to update the -H file before starting the next delivery
37450 .section "Format of the -H file" "SECID282"
37451 .cindex "uid (user id)" "in spool file"
37452 .cindex "gid (group id)" "in spool file"
37453 The second line of the -H file contains the login name for the uid of the
37454 process that called Exim to read the message, followed by the numerical uid and
37455 gid. For a locally generated message, this is normally the user who sent the
37456 message. For a message received over TCP/IP via the daemon, it is
37457 normally the Exim user.
37459 The third line of the file contains the address of the message's sender as
37460 transmitted in the envelope, contained in angle brackets. The sender address is
37461 empty for bounce messages. For incoming SMTP mail, the sender address is given
37462 in the MAIL command. For locally generated mail, the sender address is
37463 created by Exim from the login name of the current user and the configured
37464 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
37465 leading &"From&~"& line if the caller is trusted, or if the supplied address is
37466 &"<>"& or an address that matches &%untrusted_set_senders%&.
37468 The fourth line contains two numbers. The first is the time that the message
37469 was received, in the conventional Unix form &-- the number of seconds since the
37470 start of the epoch. The second number is a count of the number of messages
37471 warning of delayed delivery that have been sent to the sender.
37473 There follow a number of lines starting with a hyphen. These can appear in any
37474 order, and are omitted when not relevant:
37477 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
37478 This item is obsolete, and is not generated from Exim release 4.61 onwards;
37479 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
37480 recognized, to provide backward compatibility. In the old format, a line of
37481 this form is present for every ACL variable that is not empty. The number
37482 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
37483 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
37484 the data string for the variable. The string itself starts at the beginning of
37485 the next line, and is followed by a newline character. It may contain internal
37488 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
37489 A line of this form is present for every ACL connection variable that is
37490 defined. Note that there is a space between &%-aclc%& and the rest of the name.
37491 The length is the length of the data string for the variable. The string itself
37492 starts at the beginning of the next line, and is followed by a newline
37493 character. It may contain internal newlines.
37495 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
37496 A line of this form is present for every ACL message variable that is defined.
37497 Note that there is a space between &%-aclm%& and the rest of the name. The
37498 length is the length of the data string for the variable. The string itself
37499 starts at the beginning of the next line, and is followed by a newline
37500 character. It may contain internal newlines.
37502 .vitem "&%-active_hostname%&&~<&'hostname'&>"
37503 This is present if, when the message was received over SMTP, the value of
37504 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
37506 .vitem &%-allow_unqualified_recipient%&
37507 This is present if unqualified recipient addresses are permitted in header
37508 lines (to stop such addresses from being qualified if rewriting occurs at
37509 transport time). Local messages that were input using &%-bnq%& and remote
37510 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
37512 .vitem &%-allow_unqualified_sender%&
37513 This is present if unqualified sender addresses are permitted in header lines
37514 (to stop such addresses from being qualified if rewriting occurs at transport
37515 time). Local messages that were input using &%-bnq%& and remote messages from
37516 hosts that match &%sender_unqualified_hosts%& set this flag.
37518 .vitem "&%-auth_id%&&~<&'text'&>"
37519 The id information for a message received on an authenticated SMTP connection
37520 &-- the value of the &$authenticated_id$& variable.
37522 .vitem "&%-auth_sender%&&~<&'address'&>"
37523 The address of an authenticated sender &-- the value of the
37524 &$authenticated_sender$& variable.
37526 .vitem "&%-body_linecount%&&~<&'number'&>"
37527 This records the number of lines in the body of the message, and is always
37530 .vitem "&%-body_zerocount%&&~<&'number'&>"
37531 This records the number of binary zero bytes in the body of the message, and is
37532 present if the number is greater than zero.
37534 .vitem &%-deliver_firsttime%&
37535 This is written when a new message is first added to the spool. When the spool
37536 file is updated after a deferral, it is omitted.
37538 .vitem "&%-frozen%&&~<&'time'&>"
37539 .cindex "frozen messages" "spool data"
37540 The message is frozen, and the freezing happened at <&'time'&>.
37542 .vitem "&%-helo_name%&&~<&'text'&>"
37543 This records the host name as specified by a remote host in a HELO or EHLO
37546 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
37547 This records the IP address of the host from which the message was received and
37548 the remote port number that was used. It is omitted for locally generated
37551 .vitem "&%-host_auth%&&~<&'text'&>"
37552 If the message was received on an authenticated SMTP connection, this records
37553 the name of the authenticator &-- the value of the
37554 &$sender_host_authenticated$& variable.
37556 .vitem &%-host_lookup_failed%&
37557 This is present if an attempt to look up the sending host's name from its IP
37558 address failed. It corresponds to the &$host_lookup_failed$& variable.
37560 .vitem "&%-host_name%&&~<&'text'&>"
37561 .cindex "reverse DNS lookup"
37562 .cindex "DNS" "reverse lookup"
37563 This records the name of the remote host from which the message was received,
37564 if the host name was looked up from the IP address when the message was being
37565 received. It is not present if no reverse lookup was done.
37567 .vitem "&%-ident%&&~<&'text'&>"
37568 For locally submitted messages, this records the login of the originating user,
37569 unless it was a trusted user and the &%-oMt%& option was used to specify an
37570 ident value. For messages received over TCP/IP, this records the ident string
37571 supplied by the remote host, if any.
37573 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
37574 This records the IP address of the local interface and the port number through
37575 which a message was received from a remote host. It is omitted for locally
37576 generated messages.
37579 The message is from a local sender.
37581 .vitem &%-localerror%&
37582 The message is a locally-generated bounce message.
37584 .vitem "&%-local_scan%&&~<&'string'&>"
37585 This records the data string that was returned by the &[local_scan()]& function
37586 when the message was received &-- the value of the &$local_scan_data$&
37587 variable. It is omitted if no data was returned.
37589 .vitem &%-manual_thaw%&
37590 The message was frozen but has been thawed manually, that is, by an explicit
37591 Exim command rather than via the auto-thaw process.
37594 A testing delivery process was started using the &%-N%& option to suppress any
37595 actual deliveries, but delivery was deferred. At any further delivery attempts,
37598 .vitem &%-received_protocol%&
37599 This records the value of the &$received_protocol$& variable, which contains
37600 the name of the protocol by which the message was received.
37602 .vitem &%-sender_set_untrusted%&
37603 The envelope sender of this message was set by an untrusted local caller (used
37604 to ensure that the caller is displayed in queue listings).
37606 .vitem "&%-spam_score_int%&&~<&'number'&>"
37607 If a message was scanned by SpamAssassin, this is present. It records the value
37608 of &$spam_score_int$&.
37610 .vitem &%-tls_certificate_verified%&
37611 A TLS certificate was received from the client that sent this message, and the
37612 certificate was verified by the server.
37614 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
37615 When the message was received over an encrypted connection, this records the
37616 name of the cipher suite that was used.
37618 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
37619 When the message was received over an encrypted connection, and a certificate
37620 was received from the client, this records the Distinguished Name from that
37624 Following the options there is a list of those addresses to which the message
37625 is not to be delivered. This set of addresses is initialized from the command
37626 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
37627 is set; otherwise it starts out empty. Whenever a successful delivery is made,
37628 the address is added to this set. The addresses are kept internally as a
37629 balanced binary tree, and it is a representation of that tree which is written
37630 to the spool file. If an address is expanded via an alias or forward file, the
37631 original address is added to the tree when deliveries to all its child
37632 addresses are complete.
37634 If the tree is empty, there is a single line in the spool file containing just
37635 the text &"XX"&. Otherwise, each line consists of two letters, which are either
37636 Y or N, followed by an address. The address is the value for the node of the
37637 tree, and the letters indicate whether the node has a left branch and/or a
37638 right branch attached to it, respectively. If branches exist, they immediately
37639 follow. Here is an example of a three-node tree:
37641 YY darcy@austen.fict.example
37642 NN alice@wonderland.fict.example
37643 NN editor@thesaurus.ref.example
37645 After the non-recipients tree, there is a list of the message's recipients.
37646 This is a simple list, preceded by a count. It includes all the original
37647 recipients of the message, including those to whom the message has already been
37648 delivered. In the simplest case, the list contains one address per line. For
37652 editor@thesaurus.ref.example
37653 darcy@austen.fict.example
37655 alice@wonderland.fict.example
37657 However, when a child address has been added to the top-level addresses as a
37658 result of the use of the &%one_time%& option on a &(redirect)& router, each
37659 line is of the following form:
37661 <&'top-level address'&> <&'errors_to address'&> &&&
37662 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
37664 The 01 flag bit indicates the presence of the three other fields that follow
37665 the top-level address. Other bits may be used in future to support additional
37666 fields. The <&'parent number'&> is the offset in the recipients list of the
37667 original parent of the &"one time"& address. The first two fields are the
37668 envelope sender that is associated with this address and its length. If the
37669 length is zero, there is no special envelope sender (there are then two space
37670 characters in the line). A non-empty field can arise from a &(redirect)& router
37671 that has an &%errors_to%& setting.
37674 A blank line separates the envelope and status information from the headers
37675 which follow. A header may occupy several lines of the file, and to save effort
37676 when reading it in, each header is preceded by a number and an identifying
37677 character. The number is the number of characters in the header, including any
37678 embedded newlines and the terminating newline. The character is one of the
37682 .row <&'blank'&> "header in which Exim has no special interest"
37683 .row &`B`& "&'Bcc:'& header"
37684 .row &`C`& "&'Cc:'& header"
37685 .row &`F`& "&'From:'& header"
37686 .row &`I`& "&'Message-id:'& header"
37687 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
37688 .row &`R`& "&'Reply-To:'& header"
37689 .row &`S`& "&'Sender:'& header"
37690 .row &`T`& "&'To:'& header"
37691 .row &`*`& "replaced or deleted header"
37694 Deleted or replaced (rewritten) headers remain in the spool file for debugging
37695 purposes. They are not transmitted when the message is delivered. Here is a
37696 typical set of headers:
37698 111P Received: by hobbit.fict.example with local (Exim 4.00)
37699 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
37700 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
37701 038* X-rewrote-sender: bb@hobbit.fict.example
37702 042* From: Bilbo Baggins <bb@hobbit.fict.example>
37703 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
37704 099* To: alice@wonderland.fict.example, rdo@foundation,
37705 darcy@austen.fict.example, editor@thesaurus.ref.example
37706 104T To: alice@wonderland.fict.example, rdo@foundation.example,
37707 darcy@austen.fict.example, editor@thesaurus.ref.example
37708 038 Date: Fri, 11 May 2001 10:28:59 +0100
37710 The asterisked headers indicate that the envelope sender, &'From:'& header, and
37711 &'To:'& header have been rewritten, the last one because routing expanded the
37712 unqualified domain &'foundation'&.
37713 .ecindex IIDforspo1
37714 .ecindex IIDforspo2
37715 .ecindex IIDforspo3
37717 . ////////////////////////////////////////////////////////////////////////////
37718 . ////////////////////////////////////////////////////////////////////////////
37720 .chapter "Support for DKIM (DomainKeys Identified Mail)" "CHAPdkim" &&&
37724 DKIM is a mechanism by which messages sent by some entity can be provably
37725 linked to a domain which that entity controls. It permits reputation to
37726 be tracked on a per-domain basis, rather than merely upon source IP address.
37727 DKIM is documented in RFC 4871.
37729 Since version 4.70, DKIM support is compiled into Exim by default. It can be
37730 disabled by setting DISABLE_DKIM=yes in Local/Makefile.
37732 Exim's DKIM implementation allows to
37734 Sign outgoing messages: This function is implemented in the SMTP transport.
37735 It can co-exist with all other Exim features
37736 (including transport filters)
37737 except cutthrough delivery.
37739 Verify signatures in incoming messages: This is implemented by an additional
37740 ACL (acl_smtp_dkim), which can be called several times per message, with
37741 different signature contexts.
37744 In typical Exim style, the verification implementation does not include any
37745 default "policy". Instead it enables you to build your own policy using
37746 Exim's standard controls.
37748 Please note that verification of DKIM signatures in incoming mail is turned
37749 on by default for logging purposes. For each signature in incoming email,
37750 exim will log a line displaying the most important signature details, and the
37751 signature status. Here is an example (with line-breaks added for clarity):
37753 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
37754 d=facebookmail.com s=q1-2009b
37755 c=relaxed/relaxed a=rsa-sha1
37756 i=@facebookmail.com t=1252484542 [verification succeeded]
37758 You might want to turn off DKIM verification processing entirely for internal
37759 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
37760 control modifier. This should typically be done in the RCPT ACL, at points
37761 where you accept mail from relay sources (internal hosts or authenticated
37765 .section "Signing outgoing messages" "SECID513"
37766 .cindex "DKIM" "signing"
37768 Signing is implemented by setting private options on the SMTP transport.
37769 These options take (expandable) strings as arguments.
37771 .option dkim_domain smtp string&!! unset
37773 The domain you want to sign with. The result of this expanded
37774 option is put into the &%$dkim_domain%& expansion variable.
37776 .option dkim_selector smtp string&!! unset
37778 This sets the key selector string. You can use the &%$dkim_domain%& expansion
37779 variable to look up a matching selector. The result is put in the expansion
37780 variable &%$dkim_selector%& which should be used in the &%dkim_private_key%&
37781 option along with &%$dkim_domain%&.
37783 .option dkim_private_key smtp string&!! unset
37785 This sets the private key to use. You can use the &%$dkim_domain%& and
37786 &%$dkim_selector%& expansion variables to determine the private key to use.
37787 The result can either
37789 be a valid RSA private key in ASCII armor, including line breaks.
37791 start with a slash, in which case it is treated as a file that contains
37794 be "0", "false" or the empty string, in which case the message will not
37795 be signed. This case will not result in an error, even if &%dkim_strict%&
37799 .option dkim_canon smtp string&!! unset
37801 This option sets the canonicalization method used when signing a message.
37802 The DKIM RFC currently supports two methods: "simple" and "relaxed".
37803 The option defaults to "relaxed" when unset. Note: the current implementation
37804 only supports using the same canonicalization method for both headers and body.
37806 .option dkim_strict smtp string&!! unset
37808 This option defines how Exim behaves when signing a message that
37809 should be signed fails for some reason. When the expansion evaluates to
37810 either "1" or "true", Exim will defer. Otherwise Exim will send the message
37811 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
37814 .option dkim_sign_headers smtp string&!! unset
37816 When set, this option must expand to (or be specified as) a colon-separated
37817 list of header names. Headers with these names will be included in the message
37818 signature. When unspecified, the header names recommended in RFC4871 will be
37822 .section "Verifying DKIM signatures in incoming mail" "SECID514"
37823 .cindex "DKIM" "verification"
37825 Verification of DKIM signatures in incoming email is implemented via the
37826 &%acl_smtp_dkim%& ACL. By default, this ACL is called once for each
37827 syntactically(!) correct signature in the incoming message.
37828 A missing ACL definition defaults to accept.
37829 If any ACL call does not accept, the message is not accepted.
37830 If a cutthrough delivery was in progress for the message it is
37831 summarily dropped (having wasted the transmission effort).
37833 To evaluate the signature in the ACL a large number of expansion variables
37834 containing the signature status and its details are set up during the
37835 runtime of the ACL.
37837 Calling the ACL only for existing signatures is not sufficient to build
37838 more advanced policies. For that reason, the global option
37839 &%dkim_verify_signers%&, and a global expansion variable
37840 &%$dkim_signers%& exist.
37842 The global option &%dkim_verify_signers%& can be set to a colon-separated
37843 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
37844 called. It is expanded when the message has been received. At this point,
37845 the expansion variable &%$dkim_signers%& already contains a colon-separated
37846 list of signer domains and identities for the message. When
37847 &%dkim_verify_signers%& is not specified in the main configuration,
37850 dkim_verify_signers = $dkim_signers
37852 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
37853 DKIM signature in the message. Current DKIM verifiers may want to explicitly
37854 call the ACL for known domains or identities. This would be achieved as follows:
37856 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
37858 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
37859 and "ebay.com", plus all domains and identities that have signatures in the message.
37860 You can also be more creative in constructing your policy. For example:
37862 dkim_verify_signers = $sender_address_domain:$dkim_signers
37865 If a domain or identity is listed several times in the (expanded) value of
37866 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
37869 Inside the &%acl_smtp_dkim%&, the following expansion variables are
37870 available (from most to least important):
37874 .vitem &%$dkim_cur_signer%&
37875 The signer that is being evaluated in this ACL run. This can be a domain or
37876 an identity. This is one of the list items from the expanded main option
37877 &%dkim_verify_signers%& (see above).
37878 .vitem &%$dkim_verify_status%&
37879 A string describing the general status of the signature. One of
37881 &%none%&: There is no signature in the message for the current domain or
37882 identity (as reflected by &%$dkim_cur_signer%&).
37884 &%invalid%&: The signature could not be verified due to a processing error.
37885 More detail is available in &%$dkim_verify_reason%&.
37887 &%fail%&: Verification of the signature failed. More detail is
37888 available in &%$dkim_verify_reason%&.
37890 &%pass%&: The signature passed verification. It is valid.
37892 .vitem &%$dkim_verify_reason%&
37893 A string giving a little bit more detail when &%$dkim_verify_status%& is either
37894 "fail" or "invalid". One of
37896 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
37897 key for the domain could not be retrieved. This may be a temporary problem.
37899 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
37900 record for the domain is syntactically invalid.
37902 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
37903 body hash does not match the one specified in the signature header. This
37904 means that the message body was modified in transit.
37906 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
37907 could not be verified. This may mean that headers were modified,
37908 re-written or otherwise changed in a way which is incompatible with
37909 DKIM verification. It may of course also mean that the signature is forged.
37911 .vitem &%$dkim_domain%&
37912 The signing domain. IMPORTANT: This variable is only populated if there is
37913 an actual signature in the message for the current domain or identity (as
37914 reflected by &%$dkim_cur_signer%&).
37915 .vitem &%$dkim_identity%&
37916 The signing identity, if present. IMPORTANT: This variable is only populated
37917 if there is an actual signature in the message for the current domain or
37918 identity (as reflected by &%$dkim_cur_signer%&).
37919 .vitem &%$dkim_selector%&
37920 The key record selector string.
37921 .vitem &%$dkim_algo%&
37922 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
37923 .vitem &%$dkim_canon_body%&
37924 The body canonicalization method. One of 'relaxed' or 'simple'.
37925 .vitem &%dkim_canon_headers%&
37926 The header canonicalization method. One of 'relaxed' or 'simple'.
37927 .vitem &%$dkim_copiedheaders%&
37928 A transcript of headers and their values which are included in the signature
37929 (copied from the 'z=' tag of the signature).
37930 .vitem &%$dkim_bodylength%&
37931 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
37932 limit was set by the signer, "9999999999999" is returned. This makes sure
37933 that this variable always expands to an integer value.
37934 .vitem &%$dkim_created%&
37935 UNIX timestamp reflecting the date and time when the signature was created.
37936 When this was not specified by the signer, "0" is returned.
37937 .vitem &%$dkim_expires%&
37938 UNIX timestamp reflecting the date and time when the signer wants the
37939 signature to be treated as "expired". When this was not specified by the
37940 signer, "9999999999999" is returned. This makes it possible to do useful
37941 integer size comparisons against this value.
37942 .vitem &%$dkim_headernames%&
37943 A colon-separated list of names of headers included in the signature.
37944 .vitem &%$dkim_key_testing%&
37945 "1" if the key record has the "testing" flag set, "0" if not.
37946 .vitem &%$dkim_key_nosubdomains%&
37947 "1" if the key record forbids subdomaining, "0" otherwise.
37948 .vitem &%$dkim_key_srvtype%&
37949 Service type (tag s=) from the key record. Defaults to "*" if not specified
37951 .vitem &%$dkim_key_granularity%&
37952 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
37954 .vitem &%$dkim_key_notes%&
37955 Notes from the key record (tag n=).
37958 In addition, two ACL conditions are provided:
37961 .vitem &%dkim_signers%&
37962 ACL condition that checks a colon-separated list of domains or identities
37963 for a match against the domain or identity that the ACL is currently verifying
37964 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
37965 verb to a group of domains or identities. For example:
37968 # Warn when Mail purportedly from GMail has no signature at all
37969 warn log_message = GMail sender without DKIM signature
37970 sender_domains = gmail.com
37971 dkim_signers = gmail.com
37975 .vitem &%dkim_status%&
37976 ACL condition that checks a colon-separated list of possible DKIM verification
37977 results against the actual result of verification. This is typically used
37978 to restrict an ACL verb to a list of verification outcomes, for example:
37981 deny message = Mail from Paypal with invalid/missing signature
37982 sender_domains = paypal.com:paypal.de
37983 dkim_signers = paypal.com:paypal.de
37984 dkim_status = none:invalid:fail
37987 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
37988 see the documentation of the &%$dkim_verify_status%& expansion variable above
37989 for more information of what they mean.
37992 . ////////////////////////////////////////////////////////////////////////////
37993 . ////////////////////////////////////////////////////////////////////////////
37995 .chapter "Adding new drivers or lookup types" "CHID13" &&&
37996 "Adding drivers or lookups"
37997 .cindex "adding drivers"
37998 .cindex "new drivers, adding"
37999 .cindex "drivers" "adding new"
38000 The following actions have to be taken in order to add a new router, transport,
38001 authenticator, or lookup type to Exim:
38004 Choose a name for the driver or lookup type that does not conflict with any
38005 existing name; I will use &"newdriver"& in what follows.
38007 Add to &_src/EDITME_& the line:
38009 <&'type'&>&`_NEWDRIVER=yes`&
38011 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
38012 code is not to be included in the binary by default, comment this line out. You
38013 should also add any relevant comments about the driver or lookup type.
38015 Add to &_src/config.h.defaults_& the line:
38017 #define <type>_NEWDRIVER
38020 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
38021 and create a table entry as is done for all the other drivers and lookup types.
38023 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
38024 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
38025 Add your &`NEWDRIVER`& to that list.
38026 As long as the dynamic module would be named &_newdriver.so_&, you can use the
38027 simple form that most lookups have.
38029 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
38030 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
38031 driver or lookup type and add it to the definition of OBJ.
38033 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
38036 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
38037 as for other drivers and lookups.
38040 Then all you need to do is write the code! A good way to start is to make a
38041 proforma by copying an existing module of the same type, globally changing all
38042 occurrences of the name, and cutting out most of the code. Note that any
38043 options you create must be listed in alphabetical order, because the tables are
38044 searched using a binary chop procedure.
38046 There is a &_README_& file in each of the sub-directories of &_src_& describing
38047 the interface that is expected.
38052 . ////////////////////////////////////////////////////////////////////////////
38053 . ////////////////////////////////////////////////////////////////////////////
38055 . /////////////////////////////////////////////////////////////////////////////
38056 . These lines are processing instructions for the Simple DocBook Processor that
38057 . Philip Hazel has developed as a less cumbersome way of making PostScript and
38058 . PDFs than using xmlto and fop. They will be ignored by all other XML
38060 . /////////////////////////////////////////////////////////////////////////////
38065 foot_right_recto="&chaptertitle;"
38066 foot_right_verso="&chaptertitle;"
38070 .makeindex "Options index" "option"
38071 .makeindex "Variables index" "variable"
38072 .makeindex "Concept index" "concept"
38075 . /////////////////////////////////////////////////////////////////////////////
38076 . /////////////////////////////////////////////////////////////////////////////