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 "4.83"
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"
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"&. It is not known
1989 if anyone is actually using A6 records. Exim has support for A6 records, but
1990 this is included only if you set &`SUPPORT_A6=YES`& in &_Local/Makefile_&. The
1991 support has not been tested for some time.
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 &*Warning*&: The &%-j%& (parallel) flag must not be used with &'make'&; the
2036 building process fails if it is set.
2038 If this is the first time &'make'& has been run, it calls a script that builds
2039 a make file inside the build directory, using the configuration files from the
2040 &_Local_& directory. The new make file is then passed to another instance of
2041 &'make'&. This does the real work, building a number of utility scripts, and
2042 then compiling and linking the binaries for the Exim monitor (if configured), a
2043 number of utility programs, and finally Exim itself. The command &`make
2044 makefile`& can be used to force a rebuild of the make file in the build
2045 directory, should this ever be necessary.
2047 If you have problems building Exim, check for any comments there may be in the
2048 &_README_& file concerning your operating system, and also take a look at the
2049 FAQ, where some common problems are covered.
2053 .section 'Output from &"make"&' "SECID283"
2054 The output produced by the &'make'& process for compile lines is often very
2055 unreadable, because these lines can be very long. For this reason, the normal
2056 output is suppressed by default, and instead output similar to that which
2057 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2058 each module that is being compiled or linked. However, it is still possible to
2059 get the full output, by calling &'make'& like this:
2063 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2064 command reflection in &'make'&. When you ask for the full output, it is
2065 given in addition to the short output.
2069 .section "Overriding build-time options for Exim" "SECToverride"
2070 .cindex "build-time options, overriding"
2071 The main make file that is created at the beginning of the building process
2072 consists of the concatenation of a number of files which set configuration
2073 values, followed by a fixed set of &'make'& instructions. If a value is set
2074 more than once, the last setting overrides any previous ones. This provides a
2075 convenient way of overriding defaults. The files that are concatenated are, in
2078 &_OS/Makefile-Default_&
2079 &_OS/Makefile-_&<&'ostype'&>
2081 &_Local/Makefile-_&<&'ostype'&>
2082 &_Local/Makefile-_&<&'archtype'&>
2083 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2084 &_OS/Makefile-Base_&
2086 .cindex "&_Local/Makefile_&"
2087 .cindex "building Exim" "operating system type"
2088 .cindex "building Exim" "architecture type"
2089 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2090 architecture type. &_Local/Makefile_& is required to exist, and the building
2091 process fails if it is absent. The other three &_Local_& files are optional,
2092 and are often not needed.
2094 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2095 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2096 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2097 values are used, thereby providing a means of forcing particular settings.
2098 Otherwise, the scripts try to get values from the &%uname%& command. If this
2099 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2100 of &'ad hoc'& transformations are then applied, to produce the standard names
2101 that Exim expects. You can run these scripts directly from the shell in order
2102 to find out what values are being used on your system.
2105 &_OS/Makefile-Default_& contains comments about the variables that are set
2106 therein. Some (but not all) are mentioned below. If there is something that
2107 needs changing, review the contents of this file and the contents of the make
2108 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2112 .cindex "building Exim" "overriding default settings"
2113 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2114 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2115 need to change the original files. Instead, you should make the changes by
2116 putting the new values in an appropriate &_Local_& file. For example,
2117 .cindex "Tru64-Unix build-time settings"
2118 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2119 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2120 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2121 called with the option &%-std1%&, to make it recognize some of the features of
2122 Standard C that Exim uses. (Most other compilers recognize Standard C by
2123 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2124 containing the lines
2129 If you are compiling for just one operating system, it may be easier to put
2130 these lines directly into &_Local/Makefile_&.
2132 Keeping all your local configuration settings separate from the distributed
2133 files makes it easy to transfer them to new versions of Exim simply by copying
2134 the contents of the &_Local_& directory.
2137 .cindex "NIS lookup type" "including support for"
2138 .cindex "NIS+ lookup type" "including support for"
2139 .cindex "LDAP" "including support for"
2140 .cindex "lookup" "inclusion in binary"
2141 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2142 lookup, but not all systems have these components installed, so the default is
2143 not to include the relevant code in the binary. All the different kinds of file
2144 and database lookup that Exim supports are implemented as separate code modules
2145 which are included only if the relevant compile-time options are set. In the
2146 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2152 and similar settings apply to the other lookup types. They are all listed in
2153 &_src/EDITME_&. In many cases the relevant include files and interface
2154 libraries need to be installed before compiling Exim.
2155 .cindex "cdb" "including support for"
2156 However, there are some optional lookup types (such as cdb) for which
2157 the code is entirely contained within Exim, and no external include
2158 files or libraries are required. When a lookup type is not included in the
2159 binary, attempts to configure Exim to use it cause run time configuration
2162 .cindex "pkg-config" "lookups"
2163 .cindex "pkg-config" "authenticators"
2164 Many systems now use a tool called &'pkg-config'& to encapsulate information
2165 about how to compile against a library; Exim has some initial support for
2166 being able to use pkg-config for lookups and authenticators. For any given
2167 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2168 variable with the &`_PC`& suffix in the name and assign as the value the
2169 name of the package to be queried. The results of querying via the
2170 &'pkg-config'& command will be added to the appropriate Makefile variables
2171 with &`+=`& directives, so your version of &'make'& will need to support that
2172 syntax. For instance:
2175 LOOKUP_SQLITE_PC=sqlite3
2177 AUTH_GSASL_PC=libgsasl
2178 AUTH_HEIMDAL_GSSAPI=yes
2179 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2182 .cindex "Perl" "including support for"
2183 Exim can be linked with an embedded Perl interpreter, allowing Perl
2184 subroutines to be called during string expansion. To enable this facility,
2188 must be defined in &_Local/Makefile_&. Details of this facility are given in
2189 chapter &<<CHAPperl>>&.
2191 .cindex "X11 libraries, location of"
2192 The location of the X11 libraries is something that varies a lot between
2193 operating systems, and there may be different versions of X11 to cope
2194 with. Exim itself makes no use of X11, but if you are compiling the Exim
2195 monitor, the X11 libraries must be available.
2196 The following three variables are set in &_OS/Makefile-Default_&:
2199 XINCLUDE=-I$(X11)/include
2200 XLFLAGS=-L$(X11)/lib
2202 These are overridden in some of the operating-system configuration files. For
2203 example, in &_OS/Makefile-SunOS5_& there is
2206 XINCLUDE=-I$(X11)/include
2207 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2209 If you need to override the default setting for your operating system, place a
2210 definition of all three of these variables into your
2211 &_Local/Makefile-<ostype>_& file.
2214 If you need to add any extra libraries to the link steps, these can be put in a
2215 variable called EXTRALIBS, which appears in all the link commands, but by
2216 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2217 command for linking the main Exim binary, and not for any associated utilities.
2219 .cindex "DBM libraries" "configuration for building"
2220 There is also DBMLIB, which appears in the link commands for binaries that
2221 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2222 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2223 binary, and which can be used, for example, to include additional X11
2226 .cindex "configuration file" "editing"
2227 The make file copes with rebuilding Exim correctly if any of the configuration
2228 files are edited. However, if an optional configuration file is deleted, it is
2229 necessary to touch the associated non-optional file (that is,
2230 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2233 .section "OS-specific header files" "SECID30"
2235 .cindex "building Exim" "OS-specific C header files"
2236 The &_OS_& directory contains a number of files with names of the form
2237 &_os.h-<ostype>_&. These are system-specific C header files that should not
2238 normally need to be changed. There is a list of macro settings that are
2239 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2240 are porting Exim to a new operating system.
2244 .section "Overriding build-time options for the monitor" "SECID31"
2245 .cindex "building Eximon"
2246 A similar process is used for overriding things when building the Exim monitor,
2247 where the files that are involved are
2249 &_OS/eximon.conf-Default_&
2250 &_OS/eximon.conf-_&<&'ostype'&>
2251 &_Local/eximon.conf_&
2252 &_Local/eximon.conf-_&<&'ostype'&>
2253 &_Local/eximon.conf-_&<&'archtype'&>
2254 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2256 .cindex "&_Local/eximon.conf_&"
2257 As with Exim itself, the final three files need not exist, and in this case the
2258 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2259 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2260 variables of the same name, preceded by EXIMON_. For example, setting
2261 EXIMON_LOG_DEPTH in the environment overrides the value of
2262 LOG_DEPTH at run time.
2266 .section "Installing Exim binaries and scripts" "SECID32"
2267 .cindex "installing Exim"
2268 .cindex "BIN_DIRECTORY"
2269 The command &`make install`& runs the &(exim_install)& script with no
2270 arguments. The script copies binaries and utility scripts into the directory
2271 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2272 .cindex "setuid" "installing Exim with"
2273 The install script copies files only if they are newer than the files they are
2274 going to replace. The Exim binary is required to be owned by root and have the
2275 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2276 install`& as root so that it can set up the Exim binary in this way. However, in
2277 some special situations (for example, if a host is doing no local deliveries)
2278 it may be possible to run Exim without making the binary setuid root (see
2279 chapter &<<CHAPsecurity>>& for details).
2281 .cindex "CONFIGURE_FILE"
2282 Exim's run time configuration file is named by the CONFIGURE_FILE setting
2283 in &_Local/Makefile_&. If this names a single file, and the file does not
2284 exist, the default configuration file &_src/configure.default_& is copied there
2285 by the installation script. If a run time configuration file already exists, it
2286 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2287 alternative files, no default is installed.
2289 .cindex "system aliases file"
2290 .cindex "&_/etc/aliases_&"
2291 One change is made to the default configuration file when it is installed: the
2292 default configuration contains a router that references a system aliases file.
2293 The path to this file is set to the value specified by
2294 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2295 If the system aliases file does not exist, the installation script creates it,
2296 and outputs a comment to the user.
2298 The created file contains no aliases, but it does contain comments about the
2299 aliases a site should normally have. Mail aliases have traditionally been
2300 kept in &_/etc/aliases_&. However, some operating systems are now using
2301 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2302 Exim's configuration if necessary.
2304 The default configuration uses the local host's name as the only local domain,
2305 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2306 running as the local user. System aliases and &_.forward_& files in users' home
2307 directories are supported, but no NIS or NIS+ support is configured. Domains
2308 other than the name of the local host are routed using the DNS, with delivery
2311 It is possible to install Exim for special purposes (such as building a binary
2312 distribution) in a private part of the file system. You can do this by a
2315 make DESTDIR=/some/directory/ install
2317 This has the effect of pre-pending the specified directory to all the file
2318 paths, except the name of the system aliases file that appears in the default
2319 configuration. (If a default alias file is created, its name &'is'& modified.)
2320 For backwards compatibility, ROOT is used if DESTDIR is not set,
2321 but this usage is deprecated.
2323 .cindex "installing Exim" "what is not installed"
2324 Running &'make install'& does not copy the Exim 4 conversion script
2325 &'convert4r4'&. You will probably run this only once if you are
2326 upgrading from Exim 3. None of the documentation files in the &_doc_&
2327 directory are copied, except for the info files when you have set
2328 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2330 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2331 to their names. The Exim binary itself, however, is handled differently. It is
2332 installed under a name that includes the version number and the compile number,
2333 for example &_exim-&version()-1_&. The script then arranges for a symbolic link
2334 called &_exim_& to point to the binary. If you are updating a previous version
2335 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2336 from the directory (as seen by other processes).
2338 .cindex "installing Exim" "testing the script"
2339 If you want to see what the &'make install'& will do before running it for
2340 real, you can pass the &%-n%& option to the installation script by this
2343 make INSTALL_ARG=-n install
2345 The contents of the variable INSTALL_ARG are passed to the installation
2346 script. You do not need to be root to run this test. Alternatively, you can run
2347 the installation script directly, but this must be from within the build
2348 directory. For example, from the top-level Exim directory you could use this
2351 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2353 .cindex "installing Exim" "install script options"
2354 There are two other options that can be supplied to the installation script.
2357 &%-no_chown%& bypasses the call to change the owner of the installed binary
2358 to root, and the call to make it a setuid binary.
2360 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2364 INSTALL_ARG can be used to pass these options to the script. For example:
2366 make INSTALL_ARG=-no_symlink install
2368 The installation script can also be given arguments specifying which files are
2369 to be copied. For example, to install just the Exim binary, and nothing else,
2370 without creating the symbolic link, you could use:
2372 make INSTALL_ARG='-no_symlink exim' install
2377 .section "Installing info documentation" "SECTinsinfdoc"
2378 .cindex "installing Exim" "&'info'& documentation"
2379 Not all systems use the GNU &'info'& system for documentation, and for this
2380 reason, the Texinfo source of Exim's documentation is not included in the main
2381 distribution. Instead it is available separately from the ftp site (see section
2384 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2385 source of the documentation is found in the source tree, running &`make
2386 install`& automatically builds the info files and installs them.
2390 .section "Setting up the spool directory" "SECID33"
2391 .cindex "spool directory" "creating"
2392 When it starts up, Exim tries to create its spool directory if it does not
2393 exist. The Exim uid and gid are used for the owner and group of the spool
2394 directory. Sub-directories are automatically created in the spool directory as
2400 .section "Testing" "SECID34"
2401 .cindex "testing" "installation"
2402 Having installed Exim, you can check that the run time configuration file is
2403 syntactically valid by running the following command, which assumes that the
2404 Exim binary directory is within your PATH environment variable:
2408 If there are any errors in the configuration file, Exim outputs error messages.
2409 Otherwise it outputs the version number and build date,
2410 the DBM library that is being used, and information about which drivers and
2411 other optional code modules are included in the binary.
2412 Some simple routing tests can be done by using the address testing option. For
2415 &`exim -bt`& <&'local username'&>
2417 should verify that it recognizes a local mailbox, and
2419 &`exim -bt`& <&'remote address'&>
2421 a remote one. Then try getting it to deliver mail, both locally and remotely.
2422 This can be done by passing messages directly to Exim, without going through a
2423 user agent. For example:
2425 exim -v postmaster@your.domain.example
2426 From: user@your.domain.example
2427 To: postmaster@your.domain.example
2428 Subject: Testing Exim
2430 This is a test message.
2433 The &%-v%& option causes Exim to output some verification of what it is doing.
2434 In this case you should see copies of three log lines, one for the message's
2435 arrival, one for its delivery, and one containing &"Completed"&.
2437 .cindex "delivery" "problems with"
2438 If you encounter problems, look at Exim's log files (&'mainlog'& and
2439 &'paniclog'&) to see if there is any relevant information there. Another source
2440 of information is running Exim with debugging turned on, by specifying the
2441 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2442 with debugging turned on by a command of the form
2444 &`exim -d -M`& <&'exim-message-id'&>
2446 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2447 produces rather a lot of output, but you can cut this down to specific areas.
2448 For example, if you use &%-d-all+route%& only the debugging information
2449 relevant to routing is included. (See the &%-d%& option in chapter
2450 &<<CHAPcommandline>>& for more details.)
2452 .cindex '&"sticky"& bit'
2453 .cindex "lock files"
2454 One specific problem that has shown up on some sites is the inability to do
2455 local deliveries into a shared mailbox directory, because it does not have the
2456 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2457 writing to a mailbox file, and if it cannot create the lock file, the delivery
2458 is deferred. You can get round this either by setting the &"sticky bit"& on the
2459 directory, or by setting a specific group for local deliveries and allowing
2460 that group to create files in the directory (see the comments above the
2461 &(local_delivery)& transport in the default configuration file). Another
2462 approach is to configure Exim not to use lock files, but just to rely on
2463 &[fcntl()]& locking instead. However, you should do this only if all user
2464 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2465 see chapter &<<CHAPappendfile>>&.
2467 One thing that cannot be tested on a system that is already running an MTA is
2468 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2469 &%-oX%& option can be used to run an Exim daemon that listens on some other
2470 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2471 &'exim_checkaccess'& utility can be used to check out policy controls on
2474 Testing a new version on a system that is already running Exim can most easily
2475 be done by building a binary with a different CONFIGURE_FILE setting. From
2476 within the run time configuration, all other file and directory names
2477 that Exim uses can be altered, in order to keep it entirely clear of the
2481 .section "Replacing another MTA with Exim" "SECID35"
2482 .cindex "replacing another MTA"
2483 Building and installing Exim for the first time does not of itself put it in
2484 general use. The name by which the system's MTA is called by mail user agents
2485 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2486 operating system), and it is necessary to make this name point to the &'exim'&
2487 binary in order to get the user agents to pass messages to Exim. This is
2488 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2489 or &_/usr/lib/sendmail_&
2490 .cindex "symbolic link" "to &'exim'& binary"
2491 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2492 privilege and executable status from the old MTA. It is then necessary to stop
2493 and restart the mailer daemon, if one is running.
2495 .cindex "FreeBSD, MTA indirection"
2496 .cindex "&_/etc/mail/mailer.conf_&"
2497 Some operating systems have introduced alternative ways of switching MTAs. For
2498 example, if you are running FreeBSD, you need to edit the file
2499 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2500 described. A typical example of the contents of this file for running Exim is
2503 sendmail /usr/exim/bin/exim
2504 send-mail /usr/exim/bin/exim
2505 mailq /usr/exim/bin/exim -bp
2506 newaliases /usr/bin/true
2508 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2509 your Exim installation is &"live"&. Check it by sending a message from your
2510 favourite user agent.
2512 You should consider what to tell your users about the change of MTA. Exim may
2513 have different capabilities to what was previously running, and there are
2514 various operational differences such as the text of messages produced by
2515 command line options and in bounce messages. If you allow your users to make
2516 use of Exim's filtering capabilities, you should make the document entitled
2517 &'Exim's interface to mail filtering'& available to them.
2521 .section "Upgrading Exim" "SECID36"
2522 .cindex "upgrading Exim"
2523 If you are already running Exim on your host, building and installing a new
2524 version automatically makes it available to MUAs, or any other programs that
2525 call the MTA directly. However, if you are running an Exim daemon, you do need
2526 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2527 new binary. You do not need to stop processing mail in order to install a new
2528 version of Exim. The install script does not modify an existing runtime
2534 .section "Stopping the Exim daemon on Solaris" "SECID37"
2535 .cindex "Solaris" "stopping Exim on"
2536 The standard command for stopping the mailer daemon on Solaris is
2538 /etc/init.d/sendmail stop
2540 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2541 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2542 for the text &"sendmail"&; this is not present because the actual program name
2543 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2544 solution is to replace the line that finds the process id with something like
2546 pid=`cat /var/spool/exim/exim-daemon.pid`
2548 to obtain the daemon's pid directly from the file that Exim saves it in.
2550 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2551 still be received from local processes, and if automatic delivery is configured
2552 (the normal case), deliveries will still occur.
2557 . ////////////////////////////////////////////////////////////////////////////
2558 . ////////////////////////////////////////////////////////////////////////////
2560 .chapter "The Exim command line" "CHAPcommandline"
2561 .scindex IIDclo1 "command line" "options"
2562 .scindex IIDclo2 "options" "command line"
2563 Exim's command line takes the standard Unix form of a sequence of options,
2564 each starting with a hyphen character, followed by a number of arguments. The
2565 options are compatible with the main options of Sendmail, and there are also
2566 some additional options, some of which are compatible with Smail 3. Certain
2567 combinations of options do not make sense, and provoke an error if used.
2568 The form of the arguments depends on which options are set.
2571 .section "Setting options by program name" "SECID38"
2573 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2574 were present before any other options.
2575 The &%-bp%& option requests a listing of the contents of the mail queue on the
2577 This feature is for compatibility with some systems that contain a command of
2578 that name in one of the standard libraries, symbolically linked to
2579 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2582 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2583 were present before any other options, for compatibility with Smail. The
2584 &%-bS%& option is used for reading in a number of messages in batched SMTP
2588 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2589 &%-oee%& options were present before any other options, for compatibility with
2590 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2593 .cindex "queue runner"
2594 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2595 were present before any other options, for compatibility with Smail. The &%-q%&
2596 option causes a single queue runner process to be started.
2598 .cindex "&'newaliases'&"
2599 .cindex "alias file" "building"
2600 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2601 If Exim is called under the name &'newaliases'& it behaves as if the option
2602 &%-bi%& were present before any other options, for compatibility with Sendmail.
2603 This option is used for rebuilding Sendmail's alias file. Exim does not have
2604 the concept of a single alias file, but can be configured to run a given
2605 command if called with the &%-bi%& option.
2608 .section "Trusted and admin users" "SECTtrustedadmin"
2609 Some Exim options are available only to &'trusted users'& and others are
2610 available only to &'admin users'&. In the description below, the phrases &"Exim
2611 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2612 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2613 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2616 .cindex "trusted users" "definition of"
2617 .cindex "user" "trusted definition of"
2618 The trusted users are root, the Exim user, any user listed in the
2619 &%trusted_users%& configuration option, and any user whose current group or any
2620 supplementary group is one of those listed in the &%trusted_groups%&
2621 configuration option. Note that the Exim group is not automatically trusted.
2623 .cindex '&"From"& line'
2624 .cindex "envelope sender"
2625 Trusted users are always permitted to use the &%-f%& option or a leading
2626 &"From&~"& line to specify the envelope sender of a message that is passed to
2627 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2628 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2629 users to set envelope senders.
2631 .cindex "&'From:'& header line"
2632 .cindex "&'Sender:'& header line"
2633 For a trusted user, there is never any check on the contents of the &'From:'&
2634 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2635 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2637 Trusted users may also specify a host name, host address, interface address,
2638 protocol name, ident value, and authentication data when submitting a message
2639 locally. Thus, they are able to insert messages into Exim's queue locally that
2640 have the characteristics of messages received from a remote host. Untrusted
2641 users may in some circumstances use &%-f%&, but can never set the other values
2642 that are available to trusted users.
2644 .cindex "user" "admin definition of"
2645 .cindex "admin user" "definition of"
2646 The admin users are root, the Exim user, and any user that is a member of the
2647 Exim group or of any group listed in the &%admin_groups%& configuration option.
2648 The current group does not have to be one of these groups.
2650 Admin users are permitted to list the queue, and to carry out certain
2651 operations on messages, for example, to force delivery failures. It is also
2652 necessary to be an admin user in order to see the full information provided by
2653 the Exim monitor, and full debugging output.
2655 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2656 Exim to attempt delivery of messages on its queue is restricted to admin users.
2657 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2658 option false (that is, specifying &%no_prod_requires_admin%&).
2660 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2661 is restricted to admin users unless &%queue_list_requires_admin%& is set
2666 &*Warning*&: If you configure your system so that admin users are able to
2667 edit Exim's configuration file, you are giving those users an easy way of
2668 getting root. There is further discussion of this issue at the start of chapter
2674 .section "Command line options" "SECID39"
2675 Exim's command line options are described in alphabetical order below. If none
2676 of the options that specifies a specific action (such as starting the daemon or
2677 a queue runner, or testing an address, or receiving a message in a specific
2678 format, or listing the queue) are present, and there is at least one argument
2679 on the command line, &%-bm%& (accept a local message on the standard input,
2680 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2681 outputs a brief message about itself and exits.
2683 . ////////////////////////////////////////////////////////////////////////////
2684 . Insert a stylized XML comment here, to identify the start of the command line
2685 . options. This is for the benefit of the Perl script that automatically
2686 . creates a man page for the options.
2687 . ////////////////////////////////////////////////////////////////////////////
2690 <!-- === Start of command line options === -->
2697 .cindex "options" "command line; terminating"
2698 This is a pseudo-option whose only purpose is to terminate the options and
2699 therefore to cause subsequent command line items to be treated as arguments
2700 rather than options, even if they begin with hyphens.
2703 .oindex "&%--help%&"
2704 This option causes Exim to output a few sentences stating what it is.
2705 The same output is generated if the Exim binary is called with no options and
2708 .vitem &%--version%&
2709 .oindex "&%--version%&"
2710 This option is an alias for &%-bV%& and causes version information to be
2717 These options are used by Sendmail for selecting configuration files and are
2720 .vitem &%-B%&<&'type'&>
2722 .cindex "8-bit characters"
2723 .cindex "Sendmail compatibility" "8-bit characters"
2724 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2725 clean; it ignores this option.
2730 .cindex "SMTP" "listener"
2731 .cindex "queue runner"
2732 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2733 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2734 that the daemon should also initiate periodic queue runs.
2736 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2737 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2738 disconnect from the controlling terminal. When running this way, it can be
2739 stopped by pressing ctrl-C.
2741 By default, Exim listens for incoming connections to the standard SMTP port on
2742 all the host's running interfaces. However, it is possible to listen on other
2743 ports, on multiple ports, and only on specific interfaces. Chapter
2744 &<<CHAPinterfaces>>& contains a description of the options that control this.
2746 When a listening daemon
2747 .cindex "daemon" "process id (pid)"
2748 .cindex "pid (process id)" "of daemon"
2749 is started without the use of &%-oX%& (that is, without overriding the normal
2750 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2751 in Exim's spool directory. This location can be overridden by setting
2752 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2755 When &%-oX%& is used on the command line to start a listening daemon, the
2756 process id is not written to the normal pid file path. However, &%-oP%& can be
2757 used to specify a path on the command line if a pid file is required.
2761 .cindex "daemon" "restarting"
2762 can be used to cause the daemon to re-execute itself. This should be done
2763 whenever Exim's configuration file, or any file that is incorporated into it by
2764 means of the &%.include%& facility, is changed, and also whenever a new version
2765 of Exim is installed. It is not necessary to do this when other files that are
2766 referenced from the configuration (for example, alias files) are changed,
2767 because these are reread each time they are used.
2771 This option has the same effect as &%-bd%& except that it never disconnects
2772 from the controlling terminal, even when no debugging is specified.
2776 .cindex "testing" "string expansion"
2777 .cindex "expansion" "testing"
2778 Run Exim in expansion testing mode. Exim discards its root privilege, to
2779 prevent ordinary users from using this mode to read otherwise inaccessible
2780 files. If no arguments are given, Exim runs interactively, prompting for lines
2781 of data. Otherwise, it processes each argument in turn.
2783 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2784 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2785 used without command line arguments. If successful, it uses the &[readline()]&
2786 function, which provides extensive line-editing facilities, for reading the
2787 test data. A line history is supported.
2789 Long expansion expressions can be split over several lines by using backslash
2790 continuations. As in Exim's run time configuration, white space at the start of
2791 continuation lines is ignored. Each argument or data line is passed through the
2792 string expansion mechanism, and the result is output. Variable values from the
2793 configuration file (for example, &$qualify_domain$&) are available, but no
2794 message-specific values (such as &$sender_domain$&) are set, because no message
2795 is being processed (but see &%-bem%& and &%-Mset%&).
2797 &*Note*&: If you use this mechanism to test lookups, and you change the data
2798 files or databases you are using, you must exit and restart Exim before trying
2799 the same lookup again. Otherwise, because each Exim process caches the results
2800 of lookups, you will just get the same result as before.
2802 .vitem &%-bem%&&~<&'filename'&>
2804 .cindex "testing" "string expansion"
2805 .cindex "expansion" "testing"
2806 This option operates like &%-be%& except that it must be followed by the name
2807 of a file. For example:
2809 exim -bem /tmp/testmessage
2811 The file is read as a message (as if receiving a locally-submitted non-SMTP
2812 message) before any of the test expansions are done. Thus, message-specific
2813 variables such as &$message_size$& and &$header_from:$& are available. However,
2814 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2815 recipients are read from the headers in the normal way, and are shown in the
2816 &$recipients$& variable. Note that recipients cannot be given on the command
2817 line, because further arguments are taken as strings to expand (just like
2820 .vitem &%-bF%&&~<&'filename'&>
2822 .cindex "system filter" "testing"
2823 .cindex "testing" "system filter"
2824 This option is the same as &%-bf%& except that it assumes that the filter being
2825 tested is a system filter. The additional commands that are available only in
2826 system filters are recognized.
2828 .vitem &%-bf%&&~<&'filename'&>
2830 .cindex "filter" "testing"
2831 .cindex "testing" "filter file"
2832 .cindex "forward file" "testing"
2833 .cindex "testing" "forward file"
2834 .cindex "Sieve filter" "testing"
2835 This option runs Exim in user filter testing mode; the file is the filter file
2836 to be tested, and a test message must be supplied on the standard input. If
2837 there are no message-dependent tests in the filter, an empty file can be
2840 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2841 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2842 filter and a user filter in the same run. For example:
2844 exim -bF /system/filter -bf /user/filter </test/message
2846 This is helpful when the system filter adds header lines or sets filter
2847 variables that are used by the user filter.
2849 If the test filter file does not begin with one of the special lines
2854 it is taken to be a normal &_.forward_& file, and is tested for validity under
2855 that interpretation. See sections &<<SECTitenonfilred>>& to
2856 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2859 The result of an Exim command that uses &%-bf%&, provided no errors are
2860 detected, is a list of the actions that Exim would try to take if presented
2861 with the message for real. More details of filter testing are given in the
2862 separate document entitled &'Exim's interfaces to mail filtering'&.
2864 When testing a filter file,
2865 .cindex "&""From""& line"
2866 .cindex "envelope sender"
2867 .oindex "&%-f%&" "for filter testing"
2868 the envelope sender can be set by the &%-f%& option,
2869 or by a &"From&~"& line at the start of the test message. Various parameters
2870 that would normally be taken from the envelope recipient address of the message
2871 can be set by means of additional command line options (see the next four
2874 .vitem &%-bfd%&&~<&'domain'&>
2876 .vindex "&$qualify_domain$&"
2877 This sets the domain of the recipient address when a filter file is being
2878 tested by means of the &%-bf%& option. The default is the value of
2881 .vitem &%-bfl%&&~<&'local&~part'&>
2883 This sets the local part of the recipient address when a filter file is being
2884 tested by means of the &%-bf%& option. The default is the username of the
2885 process that calls Exim. A local part should be specified with any prefix or
2886 suffix stripped, because that is how it appears to the filter when a message is
2887 actually being delivered.
2889 .vitem &%-bfp%&&~<&'prefix'&>
2891 This sets the prefix of the local part of the recipient address when a filter
2892 file is being tested by means of the &%-bf%& option. The default is an empty
2895 .vitem &%-bfs%&&~<&'suffix'&>
2897 This sets the suffix of the local part of the recipient address when a filter
2898 file is being tested by means of the &%-bf%& option. The default is an empty
2901 .vitem &%-bh%&&~<&'IP&~address'&>
2903 .cindex "testing" "incoming SMTP"
2904 .cindex "SMTP" "testing incoming"
2905 .cindex "testing" "relay control"
2906 .cindex "relaying" "testing configuration"
2907 .cindex "policy control" "testing"
2908 .cindex "debugging" "&%-bh%& option"
2909 This option runs a fake SMTP session as if from the given IP address, using the
2910 standard input and output. The IP address may include a port number at the end,
2911 after a full stop. For example:
2913 exim -bh 10.9.8.7.1234
2914 exim -bh fe80::a00:20ff:fe86:a061.5678
2916 When an IPv6 address is given, it is converted into canonical form. In the case
2917 of the second example above, the value of &$sender_host_address$& after
2918 conversion to the canonical form is
2919 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2921 Comments as to what is going on are written to the standard error file. These
2922 include lines beginning with &"LOG"& for anything that would have been logged.
2923 This facility is provided for testing configuration options for incoming
2924 messages, to make sure they implement the required policy. For example, you can
2925 test your relay controls using &%-bh%&.
2929 You can test features of the configuration that rely on ident (RFC 1413)
2930 information by using the &%-oMt%& option. However, Exim cannot actually perform
2931 an ident callout when testing using &%-bh%& because there is no incoming SMTP
2934 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2935 are also skipped when testing using &%-bh%&. If you want these callouts to
2936 occur, use &%-bhc%& instead.
2938 Messages supplied during the testing session are discarded, and nothing is
2939 written to any of the real log files. There may be pauses when DNS (and other)
2940 lookups are taking place, and of course these may time out. The &%-oMi%& option
2941 can be used to specify a specific IP interface and port if this is important,
2942 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
2943 session were authenticated.
2945 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2946 output just states whether a given recipient address from a given host is
2947 acceptable or not. See section &<<SECTcheckaccess>>&.
2949 Features such as authentication and encryption, where the client input is not
2950 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
2951 specialized SMTP test program such as
2952 &url(http://jetmore.org/john/code/#swaks,swaks).
2954 .vitem &%-bhc%&&~<&'IP&~address'&>
2956 This option operates in the same way as &%-bh%&, except that address
2957 verification callouts are performed if required. This includes consulting and
2958 updating the callout cache database.
2962 .cindex "alias file" "building"
2963 .cindex "building alias file"
2964 .cindex "Sendmail compatibility" "&%-bi%& option"
2965 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
2966 Exim does not have the concept of a single alias file, and so it cannot mimic
2967 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
2968 tend to appear in various scripts such as NIS make files, so the option must be
2971 If &%-bi%& is encountered, the command specified by the &%bi_command%&
2972 configuration option is run, under the uid and gid of the caller of Exim. If
2973 the &%-oA%& option is used, its value is passed to the command as an argument.
2974 The command set by &%bi_command%& may not contain arguments. The command can
2975 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
2976 if this is required. If the &%bi_command%& option is not set, calling Exim with
2979 . // Keep :help first, then the rest in alphabetical order
2981 .oindex "&%-bI:help%&"
2982 .cindex "querying exim information"
2983 We shall provide various options starting &`-bI:`& for querying Exim for
2984 information. The output of many of these will be intended for machine
2985 consumption. This one is not. The &%-bI:help%& option asks Exim for a
2986 synopsis of supported options beginning &`-bI:`&. Use of any of these
2987 options shall cause Exim to exit after producing the requested output.
2990 .oindex "&%-bI:dscp%&"
2991 .cindex "DSCP" "values"
2992 This option causes Exim to emit an alphabetically sorted list of all
2993 recognised DSCP names.
2995 .vitem &%-bI:sieve%&
2996 .oindex "&%-bI:sieve%&"
2997 .cindex "Sieve filter" "capabilities"
2998 This option causes Exim to emit an alphabetically sorted list of all supported
2999 Sieve protocol extensions on stdout, one per line. This is anticipated to be
3000 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
3001 &`SIEVE`& capability response line. As the precise list may depend upon
3002 compile-time build options, which this option will adapt to, this is the only
3003 way to guarantee a correct response.
3007 .cindex "local message reception"
3008 This option runs an Exim receiving process that accepts an incoming,
3009 locally-generated message on the standard input. The recipients are given as the
3010 command arguments (except when &%-t%& is also present &-- see below). Each
3011 argument can be a comma-separated list of RFC 2822 addresses. This is the
3012 default option for selecting the overall action of an Exim call; it is assumed
3013 if no other conflicting option is present.
3015 If any addresses in the message are unqualified (have no domain), they are
3016 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3017 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3018 suppressing this for special cases.
3020 Policy checks on the contents of local messages can be enforced by means of
3021 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3023 .cindex "return code" "for &%-bm%&"
3024 The return code is zero if the message is successfully accepted. Otherwise, the
3025 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3028 .cindex "message" "format"
3029 .cindex "format" "message"
3030 .cindex "&""From""& line"
3031 .cindex "UUCP" "&""From""& line"
3032 .cindex "Sendmail compatibility" "&""From""& line"
3033 of the message must be as defined in RFC 2822, except that, for
3034 compatibility with Sendmail and Smail, a line in one of the forms
3036 From sender Fri Jan 5 12:55 GMT 1997
3037 From sender Fri, 5 Jan 97 12:55:01
3039 (with the weekday optional, and possibly with additional text after the date)
3040 is permitted to appear at the start of the message. There appears to be no
3041 authoritative specification of the format of this line. Exim recognizes it by
3042 matching against the regular expression defined by the &%uucp_from_pattern%&
3043 option, which can be changed if necessary.
3045 .oindex "&%-f%&" "overriding &""From""& line"
3046 The specified sender is treated as if it were given as the argument to the
3047 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3048 preference to the address taken from the message. The caller of Exim must be a
3049 trusted user for the sender of a message to be set in this way.
3051 .vitem &%-bmalware%&&~<&'filename'&>
3052 .oindex "&%-bmalware%&"
3053 .cindex "testing", "malware"
3054 .cindex "malware scan test"
3055 This debugging option causes Exim to scan the given file,
3056 using the malware scanning framework. The option of &%av_scanner%& influences
3057 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3058 the expansion should have defaults which apply to this invocation. ACLs are
3059 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3060 will never be populated and &%-bmalware%& will fail.
3062 Exim will have changed working directory before resolving the filename, so
3063 using fully qualified pathnames is advisable. Exim will be running as the Exim
3064 user when it tries to open the file, rather than as the invoking user.
3065 This option requires admin privileges.
3067 The &%-bmalware%& option will not be extended to be more generally useful,
3068 there are better tools for file-scanning. This option exists to help
3069 administrators verify their Exim and AV scanner configuration.
3073 .cindex "address qualification, suppressing"
3074 By default, Exim automatically qualifies unqualified addresses (those
3075 without domains) that appear in messages that are submitted locally (that
3076 is, not over TCP/IP). This qualification applies both to addresses in
3077 envelopes, and addresses in header lines. Sender addresses are qualified using
3078 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3079 defaults to the value of &%qualify_domain%&).
3081 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3082 being used to re-submit messages that originally came from remote hosts after
3083 content scanning, you probably do not want to qualify unqualified addresses in
3084 header lines. (Such lines will be present only if you have not enabled a header
3085 syntax check in the appropriate ACL.)
3087 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3088 messages that originate on the local host. When this is used, unqualified
3089 addresses in the envelope provoke errors (causing message rejection) and
3090 unqualified addresses in header lines are left alone.
3095 .cindex "configuration options" "extracting"
3096 .cindex "options" "configuration &-- extracting"
3097 If this option is given with no arguments, it causes the values of all Exim's
3098 main configuration options to be written to the standard output. The values
3099 of one or more specific options can be requested by giving their names as
3100 arguments, for example:
3102 exim -bP qualify_domain hold_domains
3104 .cindex "hiding configuration option values"
3105 .cindex "configuration options" "hiding value of"
3106 .cindex "options" "hiding value of"
3107 However, any option setting that is preceded by the word &"hide"& in the
3108 configuration file is not shown in full, except to an admin user. For other
3109 users, the output is as in this example:
3111 mysql_servers = <value not displayable>
3113 If &%configure_file%& is given as an argument, the name of the run time
3114 configuration file is output.
3115 If a list of configuration files was supplied, the value that is output here
3116 is the name of the file that was actually used.
3118 .cindex "options" "hiding name of"
3119 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3120 name will not be output.
3122 .cindex "daemon" "process id (pid)"
3123 .cindex "pid (process id)" "of daemon"
3124 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3125 directories where log files and daemon pid files are written are output,
3126 respectively. If these values are unset, log files are written in a
3127 sub-directory of the spool directory called &%log%&, and the pid file is
3128 written directly into the spool directory.
3130 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3132 exim -bP +local_domains
3134 it searches for a matching named list of any type (domain, host, address, or
3135 local part) and outputs what it finds.
3137 .cindex "options" "router &-- extracting"
3138 .cindex "options" "transport &-- extracting"
3139 .cindex "options" "authenticator &-- extracting"
3140 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3141 followed by the name of an appropriate driver instance, the option settings for
3142 that driver are output. For example:
3144 exim -bP transport local_delivery
3146 The generic driver options are output first, followed by the driver's private
3147 options. A list of the names of drivers of a particular type can be obtained by
3148 using one of the words &%router_list%&, &%transport_list%&, or
3149 &%authenticator_list%&, and a complete list of all drivers with their option
3150 settings can be obtained by using &%routers%&, &%transports%&, or
3153 .cindex "options" "macro &-- extracting"
3154 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3155 are available, similarly to the drivers. Because macros are sometimes used
3156 for storing passwords, this option is restricted.
3157 The output format is one item per line.
3161 .cindex "queue" "listing messages on"
3162 .cindex "listing" "messages on the queue"
3163 This option requests a listing of the contents of the mail queue on the
3164 standard output. If the &%-bp%& option is followed by a list of message ids,
3165 just those messages are listed. By default, this option can be used only by an
3166 admin user. However, the &%queue_list_requires_admin%& option can be set false
3167 to allow any user to see the queue.
3169 Each message on the queue is displayed as in the following example:
3171 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3172 red.king@looking-glass.fict.example
3175 .cindex "message" "size in queue listing"
3176 .cindex "size" "of message"
3177 The first line contains the length of time the message has been on the queue
3178 (in this case 25 minutes), the size of the message (2.9K), the unique local
3179 identifier for the message, and the message sender, as contained in the
3180 envelope. For bounce messages, the sender address is empty, and appears as
3181 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3182 the default sender address, the user's login name is shown in parentheses
3183 before the sender address.
3185 .cindex "frozen messages" "in queue listing"
3186 If the message is frozen (attempts to deliver it are suspended) then the text
3187 &"*** frozen ***"& is displayed at the end of this line.
3189 The recipients of the message (taken from the envelope, not the headers) are
3190 displayed on subsequent lines. Those addresses to which the message has already
3191 been delivered are marked with the letter D. If an original address gets
3192 expanded into several addresses via an alias or forward file, the original is
3193 displayed with a D only when deliveries for all of its child addresses are
3199 This option operates like &%-bp%&, but in addition it shows delivered addresses
3200 that were generated from the original top level address(es) in each message by
3201 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3207 .cindex "queue" "count of messages on"
3208 This option counts the number of messages on the queue, and writes the total
3209 to the standard output. It is restricted to admin users, unless
3210 &%queue_list_requires_admin%& is set false.
3215 This option operates like &%-bp%&, but the output is not sorted into
3216 chronological order of message arrival. This can speed it up when there are
3217 lots of messages on the queue, and is particularly useful if the output is
3218 going to be post-processed in a way that doesn't need the sorting.
3222 This option is a combination of &%-bpr%& and &%-bpa%&.
3226 This option is a combination of &%-bpr%& and &%-bpu%&.
3231 This option operates like &%-bp%& but shows only undelivered top-level
3232 addresses for each message displayed. Addresses generated by aliasing or
3233 forwarding are not shown, unless the message was deferred after processing by a
3234 router with the &%one_time%& option set.
3239 .cindex "testing" "retry configuration"
3240 .cindex "retry" "configuration testing"
3241 This option is for testing retry rules, and it must be followed by up to three
3242 arguments. It causes Exim to look for a retry rule that matches the values
3243 and to write it to the standard output. For example:
3245 exim -brt bach.comp.mus.example
3246 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3248 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3249 argument, which is required, can be a complete address in the form
3250 &'local_part@domain'&, or it can be just a domain name. If the second argument
3251 contains a dot, it is interpreted as an optional second domain name; if no
3252 retry rule is found for the first argument, the second is tried. This ties in
3253 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3254 rule is found that matches the host, one that matches the mail domain is
3255 sought. Finally, an argument that is the name of a specific delivery error, as
3256 used in setting up retry rules, can be given. For example:
3258 exim -brt haydn.comp.mus.example quota_3d
3259 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3264 .cindex "testing" "rewriting"
3265 .cindex "rewriting" "testing"
3266 This option is for testing address rewriting rules, and it must be followed by
3267 a single argument, consisting of either a local part without a domain, or a
3268 complete address with a fully qualified domain. Exim outputs how this address
3269 would be rewritten for each possible place it might appear. See chapter
3270 &<<CHAPrewrite>>& for further details.
3274 .cindex "SMTP" "batched incoming"
3275 .cindex "batched SMTP input"
3276 This option is used for batched SMTP input, which is an alternative interface
3277 for non-interactive local message submission. A number of messages can be
3278 submitted in a single run. However, despite its name, this is not really SMTP
3279 input. Exim reads each message's envelope from SMTP commands on the standard
3280 input, but generates no responses. If the caller is trusted, or
3281 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3282 believed; otherwise the sender is always the caller of Exim.
3284 The message itself is read from the standard input, in SMTP format (leading
3285 dots doubled), terminated by a line containing just a single dot. An error is
3286 provoked if the terminating dot is missing. A further message may then follow.
3288 As for other local message submissions, the contents of incoming batch SMTP
3289 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3290 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3291 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3293 Some other SMTP commands are recognized in the input. HELO and EHLO act
3294 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3295 QUIT quits, ignoring the rest of the standard input.
3297 .cindex "return code" "for &%-bS%&"
3298 If any error is encountered, reports are written to the standard output and
3299 error streams, and Exim gives up immediately. The return code is 0 if no error
3300 was detected; it is 1 if one or more messages were accepted before the error
3301 was detected; otherwise it is 2.
3303 More details of input using batched SMTP are given in section
3304 &<<SECTincomingbatchedSMTP>>&.
3308 .cindex "SMTP" "local input"
3309 .cindex "local SMTP input"
3310 This option causes Exim to accept one or more messages by reading SMTP commands
3311 on the standard input, and producing SMTP replies on the standard output. SMTP
3312 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3313 Some user agents use this interface as a way of passing locally-generated
3314 messages to the MTA.
3317 .cindex "sender" "source of"
3318 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3319 set, the senders of messages are taken from the SMTP MAIL commands.
3320 Otherwise the content of these commands is ignored and the sender is set up as
3321 the calling user. Unqualified addresses are automatically qualified using
3322 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3323 &%-bnq%& option is used.
3327 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3328 using a listening daemon. Exim can distinguish the two cases by checking
3329 whether the standard input is a TCP/IP socket. When Exim is called from
3330 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3331 above concerning senders and qualification do not apply. In this situation,
3332 Exim behaves in exactly the same way as it does when receiving a message via
3333 the listening daemon.
3337 .cindex "testing" "addresses"
3338 .cindex "address" "testing"
3339 This option runs Exim in address testing mode, in which each argument is taken
3340 as a recipient address to be tested for deliverability. The results are
3341 written to the standard output. If a test fails, and the caller is not an admin
3342 user, no details of the failure are output, because these might contain
3343 sensitive information such as usernames and passwords for database lookups.
3345 If no arguments are given, Exim runs in an interactive manner, prompting with a
3346 right angle bracket for addresses to be tested.
3348 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3349 &[readline()]& function, because it is running as &'root'& and there are
3352 Each address is handled as if it were the recipient address of a message
3353 (compare the &%-bv%& option). It is passed to the routers and the result is
3354 written to the standard output. However, any router that has
3355 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3356 genuine routing tests if your first router passes everything to a scanner
3359 .cindex "return code" "for &%-bt%&"
3360 The return code is 2 if any address failed outright; it is 1 if no address
3361 failed outright but at least one could not be resolved for some reason. Return
3362 code 0 is given only when all addresses succeed.
3364 .cindex "duplicate addresses"
3365 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3366 addresses after routing is complete, so that only one delivery takes place.
3367 This does not happen when testing with &%-bt%&; the full results of routing are
3370 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3371 routers in the configuration makes any tests on the sender address of a
3373 .oindex "&%-f%&" "for address testing"
3374 you can use the &%-f%& option to set an appropriate sender when running
3375 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3376 default qualifying domain. However, if you have set up (for example) routers
3377 whose behaviour depends on the contents of an incoming message, you cannot test
3378 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3383 .cindex "version number of Exim"
3384 This option causes Exim to write the current version number, compilation
3385 number, and compilation date of the &'exim'& binary to the standard output.
3386 It also lists the DBM library that is being used, the optional modules (such as
3387 specific lookup types), the drivers that are included in the binary, and the
3388 name of the run time configuration file that is in use.
3390 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3391 configuration file. However, this is a static check only. It cannot check
3392 values that are to be expanded. For example, although a misspelt ACL verb is
3393 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3394 alone to discover (for example) all the typos in the configuration; some
3395 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3396 dynamic testing facilities.
3400 .cindex "verifying address" "using &%-bv%&"
3401 .cindex "address" "verification"
3402 This option runs Exim in address verification mode, in which each argument is
3403 taken as a recipient address to be verified by the routers. (This does
3404 not involve any verification callouts). During normal operation, verification
3405 happens mostly as a consequence processing a &%verify%& condition in an ACL
3406 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3407 including callouts, see the &%-bh%& and &%-bhc%& options.
3409 If verification fails, and the caller is not an admin user, no details of the
3410 failure are output, because these might contain sensitive information such as
3411 usernames and passwords for database lookups.
3413 If no arguments are given, Exim runs in an interactive manner, prompting with a
3414 right angle bracket for addresses to be verified.
3416 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3417 &[readline()]& function, because it is running as &'exim'& and there are
3420 Verification differs from address testing (the &%-bt%& option) in that routers
3421 that have &%no_verify%& set are skipped, and if the address is accepted by a
3422 router that has &%fail_verify%& set, verification fails. The address is
3423 verified as a recipient if &%-bv%& is used; to test verification for a sender
3424 address, &%-bvs%& should be used.
3426 If the &%-v%& option is not set, the output consists of a single line for each
3427 address, stating whether it was verified or not, and giving a reason in the
3428 latter case. Without &%-v%&, generating more than one address by redirection
3429 causes verification to end successfully, without considering the generated
3430 addresses. However, if just one address is generated, processing continues,
3431 and the generated address must verify successfully for the overall verification
3434 When &%-v%& is set, more details are given of how the address has been handled,
3435 and in the case of address redirection, all the generated addresses are also
3436 considered. Verification may succeed for some and fail for others.
3439 .cindex "return code" "for &%-bv%&"
3440 return code is 2 if any address failed outright; it is 1 if no address
3441 failed outright but at least one could not be resolved for some reason. Return
3442 code 0 is given only when all addresses succeed.
3444 If any of the routers in the configuration makes any tests on the sender
3445 address of a message, you should use the &%-f%& option to set an appropriate
3446 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3447 calling user at the default qualifying domain.
3451 This option acts like &%-bv%&, but verifies the address as a sender rather
3452 than a recipient address. This affects any rewriting and qualification that
3459 .cindex "inetd" "wait mode"
3460 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3461 similarly to the &%-bd%& option. All port specifications on the command-line
3462 and in the configuration file are ignored. Queue-running may not be specified.
3464 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3465 listening for connections. This permits the system to start up and have
3466 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3467 each port only when the first connection is received.
3469 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3470 which the daemon will exit, which should cause inetd to listen once more.
3472 .vitem &%-C%&&~<&'filelist'&>
3474 .cindex "configuration file" "alternate"
3475 .cindex "CONFIGURE_FILE"
3476 .cindex "alternate configuration file"
3477 This option causes Exim to find the run time configuration file from the given
3478 list instead of from the list specified by the CONFIGURE_FILE
3479 compile-time setting. Usually, the list will consist of just a single file
3480 name, but it can be a colon-separated list of names. In this case, the first
3481 file that exists is used. Failure to open an existing file stops Exim from
3482 proceeding any further along the list, and an error is generated.
3484 When this option is used by a caller other than root, and the list is different
3485 from the compiled-in list, Exim gives up its root privilege immediately, and
3486 runs with the real and effective uid and gid set to those of the caller.
3487 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3488 file contains a list of full pathnames, one per line, for configuration files
3489 which are trusted. Root privilege is retained for any configuration file so
3490 listed, as long as the caller is the Exim user (or the user specified in the
3491 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3492 not writeable by inappropriate users or groups.
3494 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3495 configuration using &%-C%& right through message reception and delivery,
3496 even if the caller is root. The reception works, but by that time, Exim is
3497 running as the Exim user, so when it re-executes to regain privilege for the
3498 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3499 test reception and delivery using two separate commands (one to put a message
3500 on the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3502 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3503 prefix string with which any file named in a &%-C%& command line option
3504 must start. In addition, the file name must not contain the sequence &`/../`&.
3505 However, if the value of the &%-C%& option is identical to the value of
3506 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3507 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3508 unset, any file name can be used with &%-C%&.
3510 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3511 to a directory to which only root has access. This prevents someone who has
3512 broken into the Exim account from running a privileged Exim with an arbitrary
3515 The &%-C%& facility is useful for ensuring that configuration files are
3516 syntactically correct, but cannot be used for test deliveries, unless the
3517 caller is privileged, or unless it is an exotic configuration that does not
3518 require privilege. No check is made on the owner or group of the files
3519 specified by this option.
3522 .vitem &%-D%&<&'macro'&>=<&'value'&>
3524 .cindex "macro" "setting on command line"
3525 This option can be used to override macro definitions in the configuration file
3526 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3527 unprivileged caller, it causes Exim to give up its root privilege.
3528 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3529 completely disabled, and its use causes an immediate error exit.
3531 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3532 colon-separated list of macros which are considered safe and, if &%-D%& only
3533 supplies macros from this list, and the values are acceptable, then Exim will
3534 not give up root privilege if the caller is root, the Exim run-time user, or
3535 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3536 to be removed in the future. Acceptable values for the macros satisfy the
3537 regexp: &`^[A-Za-z0-9_/.-]*$`&
3539 The entire option (including equals sign if present) must all be within one
3540 command line item. &%-D%& can be used to set the value of a macro to the empty
3541 string, in which case the equals sign is optional. These two commands are
3547 To include spaces in a macro definition item, quotes must be used. If you use
3548 quotes, spaces are permitted around the macro name and the equals sign. For
3551 exim '-D ABC = something' ...
3553 &%-D%& may be repeated up to 10 times on a command line.
3556 .vitem &%-d%&<&'debug&~options'&>
3558 .cindex "debugging" "list of selectors"
3559 .cindex "debugging" "&%-d%& option"
3560 This option causes debugging information to be written to the standard
3561 error stream. It is restricted to admin users because debugging output may show
3562 database queries that contain password information. Also, the details of users'
3563 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3564 writes an error message to the standard error stream and exits with a non-zero
3567 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3568 standard debugging data is output. This can be reduced, or increased to include
3569 some more rarely needed information, by directly following &%-d%& with a string
3570 made up of names preceded by plus or minus characters. These add or remove sets
3571 of debugging data, respectively. For example, &%-d+filter%& adds filter
3572 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3573 no spaces are allowed in the debug setting. The available debugging categories
3576 &`acl `& ACL interpretation
3577 &`auth `& authenticators
3578 &`deliver `& general delivery logic
3579 &`dns `& DNS lookups (see also resolver)
3580 &`dnsbl `& DNS black list (aka RBL) code
3581 &`exec `& arguments for &[execv()]& calls
3582 &`expand `& detailed debugging for string expansions
3583 &`filter `& filter handling
3584 &`hints_lookup `& hints data lookups
3585 &`host_lookup `& all types of name-to-IP address handling
3586 &`ident `& ident lookup
3587 &`interface `& lists of local interfaces
3588 &`lists `& matching things in lists
3589 &`load `& system load checks
3590 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3591 &<<CHAPlocalscan>>&)
3592 &`lookup `& general lookup code and all lookups
3593 &`memory `& memory handling
3594 &`pid `& add pid to debug output lines
3595 &`process_info `& setting info for the process log
3596 &`queue_run `& queue runs
3597 &`receive `& general message reception logic
3598 &`resolver `& turn on the DNS resolver's debugging output
3599 &`retry `& retry handling
3600 &`rewrite `& address rewriting
3601 &`route `& address routing
3602 &`timestamp `& add timestamp to debug output lines
3604 &`transport `& transports
3605 &`uid `& changes of uid/gid and looking up uid/gid
3606 &`verify `& address verification logic
3607 &`all `& almost all of the above (see below), and also &%-v%&
3609 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3610 for &`-all`&. The reason for this is that &`+all`& is something that people
3611 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3612 is included, an awful lot of output that is very rarely of interest is
3613 generated, so it now has to be explicitly requested. However, &`-all`& does
3614 turn everything off.
3616 .cindex "resolver, debugging output"
3617 .cindex "DNS resolver, debugging output"
3618 The &`resolver`& option produces output only if the DNS resolver was compiled
3619 with DEBUG enabled. This is not the case in some operating systems. Also,
3620 unfortunately, debugging output from the DNS resolver is written to stdout
3623 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3624 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3625 However, the &`pid`& selector is forced when debugging is turned on for a
3626 daemon, which then passes it on to any re-executed Exims. Exim also
3627 automatically adds the pid to debug lines when several remote deliveries are
3630 The &`timestamp`& selector causes the current time to be inserted at the start
3631 of all debug output lines. This can be useful when trying to track down delays
3634 If the &%debug_print%& option is set in any driver, it produces output whenever
3635 any debugging is selected, or if &%-v%& is used.
3637 .vitem &%-dd%&<&'debug&~options'&>
3639 This option behaves exactly like &%-d%& except when used on a command that
3640 starts a daemon process. In that case, debugging is turned off for the
3641 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3642 behaviour of the daemon without creating as much output as full debugging does.
3645 .oindex "&%-dropcr%&"
3646 This is an obsolete option that is now a no-op. It used to affect the way Exim
3647 handled CR and LF characters in incoming messages. What happens now is
3648 described in section &<<SECTlineendings>>&.
3652 .cindex "bounce message" "generating"
3653 This option specifies that an incoming message is a locally-generated delivery
3654 failure report. It is used internally by Exim when handling delivery failures
3655 and is not intended for external use. Its only effect is to stop Exim
3656 generating certain messages to the postmaster, as otherwise message cascades
3657 could occur in some situations. As part of the same option, a message id may
3658 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3659 new message contains the id, following &"R="&, as a cross-reference.
3662 .oindex "&%-e%&&'x'&"
3663 There are a number of Sendmail options starting with &%-oe%& which seem to be
3664 called by various programs without the leading &%o%& in the option. For
3665 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3666 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3668 .vitem &%-F%&&~<&'string'&>
3670 .cindex "sender" "name"
3671 .cindex "name" "of sender"
3672 This option sets the sender's full name for use when a locally-generated
3673 message is being accepted. In the absence of this option, the user's &'gecos'&
3674 entry from the password data is used. As users are generally permitted to alter
3675 their &'gecos'& entries, no security considerations are involved. White space
3676 between &%-F%& and the <&'string'&> is optional.
3678 .vitem &%-f%&&~<&'address'&>
3680 .cindex "sender" "address"
3681 .cindex "address" "sender"
3682 .cindex "trusted users"
3683 .cindex "envelope sender"
3684 .cindex "user" "trusted"
3685 This option sets the address of the envelope sender of a locally-generated
3686 message (also known as the return path). The option can normally be used only
3687 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3690 Processes running as root or the Exim user are always trusted. Other
3691 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3692 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3693 of a local message is set to the caller's login name at the default qualify
3696 There is one exception to the restriction on the use of &%-f%&: an empty sender
3697 can be specified by any user, trusted or not, to create a message that can
3698 never provoke a bounce. An empty sender can be specified either as an empty
3699 string, or as a pair of angle brackets with nothing between them, as in these
3700 examples of shell commands:
3702 exim -f '<>' user@domain
3703 exim -f "" user@domain
3705 In addition, the use of &%-f%& is not restricted when testing a filter file
3706 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3709 Allowing untrusted users to change the sender address does not of itself make
3710 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3711 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3712 though this can be overridden by setting &%no_local_from_check%&.
3715 .cindex "&""From""& line"
3716 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3717 given as two arguments or one combined argument). The sender of a
3718 locally-generated message can also be set (when permitted) by an initial
3719 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3720 if &%-f%& is also present, it overrides &"From&~"&.
3724 .cindex "submission fixups, suppressing (command-line)"
3725 This option is equivalent to an ACL applying:
3727 control = suppress_local_fixups
3729 for every message received. Note that Sendmail will complain about such
3730 bad formatting, where Exim silently just does not fix it up. This may change
3733 As this affects audit information, the caller must be a trusted user to use
3736 .vitem &%-h%&&~<&'number'&>
3738 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3739 This option is accepted for compatibility with Sendmail, but has no effect. (In
3740 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3745 .cindex "Solaris" "&'mail'& command"
3746 .cindex "dot" "in incoming non-SMTP message"
3747 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3748 line by itself should not terminate an incoming, non-SMTP message. I can find
3749 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3750 command in Solaris 2.4 uses it. See also &%-ti%&.
3752 .vitem &%-L%&&~<&'tag'&>
3754 .cindex "syslog" "process name; set with flag"
3755 This option is equivalent to setting &%syslog_processname%& in the config
3756 file and setting &%log_file_path%& to &`syslog`&.
3757 Its use is restricted to administrators. The configuration file has to be
3758 read and parsed, to determine access rights, before this is set and takes
3759 effect, so early configuration file errors will not honour this flag.
3761 The tag should not be longer than 32 characters.
3763 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3765 .cindex "forcing delivery"
3766 .cindex "delivery" "forcing attempt"
3767 .cindex "frozen messages" "forcing delivery"
3768 This option requests Exim to run a delivery attempt on each message in turn. If
3769 any of the messages are frozen, they are automatically thawed before the
3770 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3771 and &%hold_domains%& are ignored.
3774 .cindex "hints database" "overriding retry hints"
3775 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3776 the normal retry time has not yet been reached. This option requires the caller
3777 to be an admin user. However, there is an option called &%prod_requires_admin%&
3778 which can be set false to relax this restriction (and also the same requirement
3779 for the &%-q%&, &%-R%&, and &%-S%& options).
3781 The deliveries happen synchronously, that is, the original Exim process does
3782 not terminate until all the delivery attempts have finished. No output is
3783 produced unless there is a serious error. If you want to see what is happening,
3784 use the &%-v%& option as well, or inspect Exim's main log.
3786 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3788 .cindex "message" "adding recipients"
3789 .cindex "recipient" "adding"
3790 This option requests Exim to add the addresses to the list of recipients of the
3791 message (&"ar"& for &"add recipients"&). The first argument must be a message
3792 id, and the remaining ones must be email addresses. However, if the message is
3793 active (in the middle of a delivery attempt), it is not altered. This option
3794 can be used only by an admin user.
3796 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3797 &~<&'message&~id'&>"
3799 .cindex "SMTP" "passed connection"
3800 .cindex "SMTP" "multiple deliveries"
3801 .cindex "multiple SMTP deliveries"
3802 This option is not intended for use by external callers. It is used internally
3803 by Exim to invoke another instance of itself to deliver a waiting message using
3804 an existing SMTP connection, which is passed as the standard input. Details are
3805 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3806 must be root or the Exim user in order to use it.
3810 This option is not intended for use by external callers. It is used internally
3811 by Exim in conjunction with the &%-MC%& option. It signifies that the
3812 connection to the remote host has been authenticated.
3816 This option is not intended for use by external callers. It is used internally
3817 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3818 which Exim is connected supports pipelining.
3820 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3822 This option is not intended for use by external callers. It is used internally
3823 by Exim in conjunction with the &%-MC%& option when the original delivery was
3824 started by a queue runner. It passes on the process id of the queue runner,
3825 together with the file descriptor number of an open pipe. Closure of the pipe
3826 signals the final completion of the sequence of processes that are passing
3827 messages through the same SMTP connection.
3831 This option is not intended for use by external callers. It is used internally
3832 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3833 SMTP SIZE option should be used on messages delivered down the existing
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 host to which Exim is connected supports TLS encryption.
3842 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3844 .cindex "hints database" "not overridden by &%-Mc%&"
3845 .cindex "delivery" "manually started &-- not forced"
3846 This option requests Exim to run a delivery attempt on each message in turn,
3847 but unlike the &%-M%& option, it does check for retry hints, and respects any
3848 that are found. This option is not very useful to external callers. It is
3849 provided mainly for internal use by Exim when it needs to re-invoke itself in
3850 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3851 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3852 respects retry times and other options such as &%hold_domains%& that are
3853 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3854 If you want to run a specific delivery as if in a queue run, you should use
3855 &%-q%& with a message id argument. A distinction between queue run deliveries
3856 and other deliveries is made in one or two places.
3858 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3860 .cindex "message" "changing sender"
3861 .cindex "sender" "changing"
3862 This option requests Exim to change the sender address in the message to the
3863 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3864 &"edit sender"&). There must be exactly two arguments. The first argument must
3865 be a message id, and the second one an email address. However, if the message
3866 is active (in the middle of a delivery attempt), its status is not altered.
3867 This option can be used only by an admin user.
3869 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3871 .cindex "freezing messages"
3872 .cindex "message" "manually freezing"
3873 This option requests Exim to mark each listed message as &"frozen"&. This
3874 prevents any delivery attempts taking place until the message is &"thawed"&,
3875 either manually or as a result of the &%auto_thaw%& configuration option.
3876 However, if any of the messages are active (in the middle of a delivery
3877 attempt), their status is not altered. This option can be used only by an admin
3880 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3882 .cindex "giving up on messages"
3883 .cindex "message" "abandoning delivery attempts"
3884 .cindex "delivery" "abandoning further attempts"
3885 This option requests Exim to give up trying to deliver the listed messages,
3886 including any that are frozen. However, if any of the messages are active,
3887 their status is not altered. For non-bounce messages, a delivery error message
3888 is sent to the sender, containing the text &"cancelled by administrator"&.
3889 Bounce messages are just discarded. This option can be used only by an admin
3892 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3894 .cindex "delivery" "cancelling all"
3895 This option requests Exim to mark all the recipient addresses in the messages
3896 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
3897 message is active (in the middle of a delivery attempt), its status is not
3898 altered. This option can be used only by an admin user.
3900 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3902 .cindex "delivery" "cancelling by address"
3903 .cindex "recipient" "removing"
3904 .cindex "removing recipients"
3905 This option requests Exim to mark the given addresses as already delivered
3906 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
3907 the remaining ones must be email addresses. These are matched to recipient
3908 addresses in the message in a case-sensitive manner. If the message is active
3909 (in the middle of a delivery attempt), its status is not altered. This option
3910 can be used only by an admin user.
3912 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3914 .cindex "removing messages"
3915 .cindex "abandoning mail"
3916 .cindex "message" "manually discarding"
3917 This option requests Exim to remove the given messages from the queue. No
3918 bounce messages are sent; each message is simply forgotten. However, if any of
3919 the messages are active, their status is not altered. This option can be used
3920 only by an admin user or by the user who originally caused the message to be
3921 placed on the queue.
3923 .vitem &%-Mset%&&~<&'message&~id'&>
3925 .cindex "testing" "string expansion"
3926 .cindex "expansion" "testing"
3927 This option is useful only in conjunction with &%-be%& (that is, when testing
3928 string expansions). Exim loads the given message from its spool before doing
3929 the test expansions, thus setting message-specific variables such as
3930 &$message_size$& and the header variables. The &$recipients$& variable is made
3931 available. This feature is provided to make it easier to test expansions that
3932 make use of these variables. However, this option can be used only by an admin
3933 user. See also &%-bem%&.
3935 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3937 .cindex "thawing messages"
3938 .cindex "unfreezing messages"
3939 .cindex "frozen messages" "thawing"
3940 .cindex "message" "thawing frozen"
3941 This option requests Exim to &"thaw"& any of the listed messages that are
3942 &"frozen"&, so that delivery attempts can resume. However, if any of the
3943 messages are active, their status is not altered. This option can be used only
3946 .vitem &%-Mvb%&&~<&'message&~id'&>
3948 .cindex "listing" "message body"
3949 .cindex "message" "listing body of"
3950 This option causes the contents of the message body (-D) spool file to be
3951 written to the standard output. This option can be used only by an admin user.
3953 .vitem &%-Mvc%&&~<&'message&~id'&>
3955 .cindex "message" "listing in RFC 2822 format"
3956 .cindex "listing" "message in RFC 2822 format"
3957 This option causes a copy of the complete message (header lines plus body) to
3958 be written to the standard output in RFC 2822 format. This option can be used
3959 only by an admin user.
3961 .vitem &%-Mvh%&&~<&'message&~id'&>
3963 .cindex "listing" "message headers"
3964 .cindex "header lines" "listing"
3965 .cindex "message" "listing header lines"
3966 This option causes the contents of the message headers (-H) spool file to be
3967 written to the standard output. This option can be used only by an admin user.
3969 .vitem &%-Mvl%&&~<&'message&~id'&>
3971 .cindex "listing" "message log"
3972 .cindex "message" "listing message log"
3973 This option causes the contents of the message log spool file to be written to
3974 the standard output. This option can be used only by an admin user.
3978 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
3979 treats it that way too.
3983 .cindex "debugging" "&%-N%& option"
3984 .cindex "debugging" "suppressing delivery"
3985 This is a debugging option that inhibits delivery of a message at the transport
3986 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
3987 it just doesn't actually transport the message, but instead behaves as if it
3988 had successfully done so. However, it does not make any updates to the retry
3989 database, and the log entries for deliveries are flagged with &"*>"& rather
3992 Because &%-N%& discards any message to which it applies, only root or the Exim
3993 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
3994 words, an ordinary user can use it only when supplying an incoming message to
3995 which it will apply. Although transportation never fails when &%-N%& is set, an
3996 address may be deferred because of a configuration problem on a transport, or a
3997 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
3998 the message, and applies to any subsequent delivery attempts that may happen
4003 This option is interpreted by Sendmail to mean &"no aliasing"&.
4004 For normal modes of operation, it is ignored by Exim.
4005 When combined with &%-bP%& it suppresses the name of an option from being output.
4007 .vitem &%-O%&&~<&'data'&>
4009 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4012 .vitem &%-oA%&&~<&'file&~name'&>
4014 .cindex "Sendmail compatibility" "&%-oA%& option"
4015 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4016 alternative alias file name. Exim handles &%-bi%& differently; see the
4019 .vitem &%-oB%&&~<&'n'&>
4021 .cindex "SMTP" "passed connection"
4022 .cindex "SMTP" "multiple deliveries"
4023 .cindex "multiple SMTP deliveries"
4024 This is a debugging option which limits the maximum number of messages that can
4025 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4026 transport. If <&'n'&> is omitted, the limit is set to 1.
4030 .cindex "background delivery"
4031 .cindex "delivery" "in the background"
4032 This option applies to all modes in which Exim accepts incoming messages,
4033 including the listening daemon. It requests &"background"& delivery of such
4034 messages, which means that the accepting process automatically starts a
4035 delivery process for each message received, but does not wait for the delivery
4036 processes to finish.
4038 When all the messages have been received, the reception process exits,
4039 leaving the delivery processes to finish in their own time. The standard output
4040 and error streams are closed at the start of each delivery process.
4041 This is the default action if none of the &%-od%& options are present.
4043 If one of the queueing options in the configuration file
4044 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4045 overrides it if &%queue_only_override%& is set true, which is the default
4046 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4050 .cindex "foreground delivery"
4051 .cindex "delivery" "in the foreground"
4052 This option requests &"foreground"& (synchronous) delivery when Exim has
4053 accepted a locally-generated message. (For the daemon it is exactly the same as
4054 &%-odb%&.) A delivery process is automatically started to deliver the message,
4055 and Exim waits for it to complete before proceeding.
4057 The original Exim reception process does not finish until the delivery
4058 process for the final message has ended. The standard error stream is left open
4061 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4062 false and one of the queueing options in the configuration file is in effect.
4064 If there is a temporary delivery error during foreground delivery, the
4065 message is left on the queue for later delivery, and the original reception
4066 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4067 restricted configuration that never queues messages.
4072 This option is synonymous with &%-odf%&. It is provided for compatibility with
4077 .cindex "non-immediate delivery"
4078 .cindex "delivery" "suppressing immediate"
4079 .cindex "queueing incoming messages"
4080 This option applies to all modes in which Exim accepts incoming messages,
4081 including the listening daemon. It specifies that the accepting process should
4082 not automatically start a delivery process for each message received. Messages
4083 are placed on the queue, and remain there until a subsequent queue runner
4084 process encounters them. There are several configuration options (such as
4085 &%queue_only%&) that can be used to queue incoming messages under certain
4086 conditions. This option overrides all of them and also &%-odqs%&. It always
4091 .cindex "SMTP" "delaying delivery"
4092 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4093 However, like &%-odb%& and &%-odi%&, this option has no effect if
4094 &%queue_only_override%& is false and one of the queueing options in the
4095 configuration file is in effect.
4097 When &%-odqs%& does operate, a delivery process is started for each incoming
4098 message, in the background by default, but in the foreground if &%-odi%& is
4099 also present. The recipient addresses are routed, and local deliveries are done
4100 in the normal way. However, if any SMTP deliveries are required, they are not
4101 done at this time, so the message remains on the queue until a subsequent queue
4102 runner process encounters it. Because routing was done, Exim knows which
4103 messages are waiting for which hosts, and so a number of messages for the same
4104 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4105 configuration option has the same effect for specific domains. See also the
4110 .cindex "error" "reporting"
4111 If an error is detected while a non-SMTP message is being received (for
4112 example, a malformed address), the error is reported to the sender in a mail
4115 .cindex "return code" "for &%-oee%&"
4117 this error message is successfully sent, the Exim receiving process
4118 exits with a return code of zero. If not, the return code is 2 if the problem
4119 is that the original message has no recipients, or 1 for any other error.
4120 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4124 .cindex "error" "reporting"
4125 .cindex "return code" "for &%-oem%&"
4126 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4127 return code, whether or not the error message was successfully sent.
4128 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4132 .cindex "error" "reporting"
4133 If an error is detected while a non-SMTP message is being received, the
4134 error is reported by writing a message to the standard error file (stderr).
4135 .cindex "return code" "for &%-oep%&"
4136 The return code is 1 for all errors.
4140 .cindex "error" "reporting"
4141 This option is supported for compatibility with Sendmail, but has the same
4146 .cindex "error" "reporting"
4147 This option is supported for compatibility with Sendmail, but has the same
4152 .cindex "dot" "in incoming non-SMTP message"
4153 This option, which has the same effect as &%-i%&, specifies that a dot on a
4154 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4155 single dot does terminate, though Exim does no special processing for other
4156 lines that start with a dot. This option is set by default if Exim is called as
4157 &'rmail'&. See also &%-ti%&.
4160 .oindex "&%-oitrue%&"
4161 This option is treated as synonymous with &%-oi%&.
4163 .vitem &%-oMa%&&~<&'host&~address'&>
4165 .cindex "sender" "host address, specifying for local message"
4166 A number of options starting with &%-oM%& can be used to set values associated
4167 with remote hosts on locally-submitted messages (that is, messages not received
4168 over TCP/IP). These options can be used by any caller in conjunction with the
4169 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4170 other circumstances, they are ignored unless the caller is trusted.
4172 The &%-oMa%& option sets the sender host address. This may include a port
4173 number at the end, after a full stop (period). For example:
4175 exim -bs -oMa 10.9.8.7.1234
4177 An alternative syntax is to enclose the IP address in square brackets,
4178 followed by a colon and the port number:
4180 exim -bs -oMa [10.9.8.7]:1234
4182 The IP address is placed in the &$sender_host_address$& variable, and the
4183 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4184 are present on the command line, the sender host IP address is taken from
4185 whichever one is last.
4187 .vitem &%-oMaa%&&~<&'name'&>
4189 .cindex "authentication" "name, specifying for local message"
4190 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4191 option sets the value of &$sender_host_authenticated$& (the authenticator
4192 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4193 This option can be used with &%-bh%& and &%-bs%& to set up an
4194 authenticated SMTP session without actually using the SMTP AUTH command.
4196 .vitem &%-oMai%&&~<&'string'&>
4198 .cindex "authentication" "id, specifying for local message"
4199 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4200 option sets the value of &$authenticated_id$& (the id that was authenticated).
4201 This overrides the default value (the caller's login id, except with &%-bh%&,
4202 where there is no default) for messages from local sources. See chapter
4203 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4205 .vitem &%-oMas%&&~<&'address'&>
4207 .cindex "authentication" "sender, specifying for local message"
4208 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4209 option sets the authenticated sender value in &$authenticated_sender$&. It
4210 overrides the sender address that is created from the caller's login id for
4211 messages from local sources, except when &%-bh%& is used, when there is no
4212 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4213 specified on a MAIL command overrides this value. See chapter
4214 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4216 .vitem &%-oMi%&&~<&'interface&~address'&>
4218 .cindex "interface" "address, specifying for local message"
4219 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4220 option sets the IP interface address value. A port number may be included,
4221 using the same syntax as for &%-oMa%&. The interface address is placed in
4222 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4224 .vitem &%-oMm%&&~<&'message&~reference'&>
4226 .cindex "message reference" "message reference, specifying for local message"
4227 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4228 option sets the message reference, e.g. message-id, and is logged during
4229 delivery. This is useful when some kind of audit trail is required to tie
4230 messages together. The format of the message reference is checked and will
4231 abort if the format is invalid. The option will only be accepted if exim is
4232 running in trusted mode, not as any regular user.
4234 The best example of a message reference is when Exim sends a bounce message.
4235 The message reference is the message-id of the original message for which Exim
4236 is sending the bounce.
4238 .vitem &%-oMr%&&~<&'protocol&~name'&>
4240 .cindex "protocol, specifying for local message"
4241 .vindex "&$received_protocol$&"
4242 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4243 option sets the received protocol value that is stored in
4244 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4245 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4246 SMTP protocol names (see the description of &$received_protocol$& in section
4247 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4248 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4251 .vitem &%-oMs%&&~<&'host&~name'&>
4253 .cindex "sender" "host name, specifying for local message"
4254 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4255 option sets the sender host name in &$sender_host_name$&. When this option is
4256 present, Exim does not attempt to look up a host name from an IP address; it
4257 uses the name it is given.
4259 .vitem &%-oMt%&&~<&'ident&~string'&>
4261 .cindex "sender" "ident string, specifying for local message"
4262 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4263 option sets the sender ident value in &$sender_ident$&. The default setting for
4264 local callers is the login id of the calling process, except when &%-bh%& is
4265 used, when there is no default.
4269 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4270 In Sendmail, this option means &"me too"&, indicating that the sender of a
4271 message should receive a copy of the message if the sender appears in an alias
4272 expansion. Exim always does this, so the option does nothing.
4276 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4277 This option is ignored. In Sendmail it specifies &"old style headers"&,
4278 whatever that means.
4280 .vitem &%-oP%&&~<&'path'&>
4282 .cindex "pid (process id)" "of daemon"
4283 .cindex "daemon" "process id (pid)"
4284 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4285 value. The option specifies the file to which the process id of the daemon is
4286 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4287 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4288 because in those cases, the normal pid file is not used.
4290 .vitem &%-or%&&~<&'time'&>
4292 .cindex "timeout" "for non-SMTP input"
4293 This option sets a timeout value for incoming non-SMTP messages. If it is not
4294 set, Exim will wait forever for the standard input. The value can also be set
4295 by the &%receive_timeout%& option. The format used for specifying times is
4296 described in section &<<SECTtimeformat>>&.
4298 .vitem &%-os%&&~<&'time'&>
4300 .cindex "timeout" "for SMTP input"
4301 .cindex "SMTP" "input timeout"
4302 This option sets a timeout value for incoming SMTP messages. The timeout
4303 applies to each SMTP command and block of data. The value can also be set by
4304 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4305 for specifying times is described in section &<<SECTtimeformat>>&.
4309 This option has exactly the same effect as &%-v%&.
4311 .vitem &%-oX%&&~<&'number&~or&~string'&>
4313 .cindex "TCP/IP" "setting listening ports"
4314 .cindex "TCP/IP" "setting listening interfaces"
4315 .cindex "port" "receiving TCP/IP"
4316 This option is relevant only when the &%-bd%& (start listening daemon) option
4317 is also given. It controls which ports and interfaces the daemon uses. Details
4318 of the syntax, and how it interacts with configuration file options, are given
4319 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4320 file is written unless &%-oP%& is also present to specify a pid file name.
4324 .cindex "Perl" "starting the interpreter"
4325 This option applies when an embedded Perl interpreter is linked with Exim (see
4326 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4327 option, forcing the starting of the interpreter to be delayed until it is
4332 .cindex "Perl" "starting the interpreter"
4333 This option applies when an embedded Perl interpreter is linked with Exim (see
4334 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4335 option, forcing the starting of the interpreter to occur as soon as Exim is
4338 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4340 For compatibility with Sendmail, this option is equivalent to
4342 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4344 It sets the incoming protocol and host name (for trusted callers). The
4345 host name and its colon can be omitted when only the protocol is to be set.
4346 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4347 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4348 or &`s`& using this option (but that does not seem a real limitation).
4352 .cindex "queue runner" "starting manually"
4353 This option is normally restricted to admin users. However, there is a
4354 configuration option called &%prod_requires_admin%& which can be set false to
4355 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4356 and &%-S%& options).
4358 .cindex "queue runner" "description of operation"
4359 The &%-q%& option starts one queue runner process. This scans the queue of
4360 waiting messages, and runs a delivery process for each one in turn. It waits
4361 for each delivery process to finish before starting the next one. A delivery
4362 process may not actually do any deliveries if the retry times for the addresses
4363 have not been reached. Use &%-qf%& (see below) if you want to override this.
4366 .cindex "SMTP" "passed connection"
4367 .cindex "SMTP" "multiple deliveries"
4368 .cindex "multiple SMTP deliveries"
4369 the delivery process spawns other processes to deliver other messages down
4370 passed SMTP connections, the queue runner waits for these to finish before
4373 When all the queued messages have been considered, the original queue runner
4374 process terminates. In other words, a single pass is made over the waiting
4375 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4376 this to be repeated periodically.
4378 Exim processes the waiting messages in an unpredictable order. It isn't very
4379 random, but it is likely to be different each time, which is all that matters.
4380 If one particular message screws up a remote MTA, other messages to the same
4381 MTA have a chance of getting through if they get tried first.
4383 It is possible to cause the messages to be processed in lexical message id
4384 order, which is essentially the order in which they arrived, by setting the
4385 &%queue_run_in_order%& option, but this is not recommended for normal use.
4387 .vitem &%-q%&<&'qflags'&>
4388 The &%-q%& option may be followed by one or more flag letters that change its
4389 behaviour. They are all optional, but if more than one is present, they must
4390 appear in the correct order. Each flag is described in a separate item below.
4394 .cindex "queue" "double scanning"
4395 .cindex "queue" "routing"
4396 .cindex "routing" "whole queue before delivery"
4397 An option starting with &%-qq%& requests a two-stage queue run. In the first
4398 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4399 every domain. Addresses are routed, local deliveries happen, but no remote
4402 .cindex "hints database" "remembering routing"
4403 The hints database that remembers which messages are waiting for specific hosts
4404 is updated, as if delivery to those hosts had been deferred. After this is
4405 complete, a second, normal queue scan happens, with routing and delivery taking
4406 place as normal. Messages that are routed to the same host should mostly be
4407 delivered down a single SMTP
4408 .cindex "SMTP" "passed connection"
4409 .cindex "SMTP" "multiple deliveries"
4410 .cindex "multiple SMTP deliveries"
4411 connection because of the hints that were set up during the first queue scan.
4412 This option may be useful for hosts that are connected to the Internet
4415 .vitem &%-q[q]i...%&
4417 .cindex "queue" "initial delivery"
4418 If the &'i'& flag is present, the queue runner runs delivery processes only for
4419 those messages that haven't previously been tried. (&'i'& stands for &"initial
4420 delivery"&.) This can be helpful if you are putting messages on the queue using
4421 &%-odq%& and want a queue runner just to process the new messages.
4423 .vitem &%-q[q][i]f...%&
4425 .cindex "queue" "forcing delivery"
4426 .cindex "delivery" "forcing in queue run"
4427 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4428 message, whereas without &'f'& only those non-frozen addresses that have passed
4429 their retry times are tried.
4431 .vitem &%-q[q][i]ff...%&
4433 .cindex "frozen messages" "forcing delivery"
4434 If &'ff'& is present, a delivery attempt is forced for every message, whether
4437 .vitem &%-q[q][i][f[f]]l%&
4439 .cindex "queue" "local deliveries only"
4440 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4441 be done. If a message requires any remote deliveries, it remains on the queue
4444 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4445 .cindex "queue" "delivering specific messages"
4446 When scanning the queue, Exim can be made to skip over messages whose ids are
4447 lexically less than a given value by following the &%-q%& option with a
4448 starting message id. For example:
4450 exim -q 0t5C6f-0000c8-00
4452 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4453 second message id is given, messages whose ids are lexically greater than it
4454 are also skipped. If the same id is given twice, for example,
4456 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4458 just one delivery process is started, for that message. This differs from
4459 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4460 that it counts as a delivery from a queue run. Note that the selection
4461 mechanism does not affect the order in which the messages are scanned. There
4462 are also other ways of selecting specific sets of messages for delivery in a
4463 queue run &-- see &%-R%& and &%-S%&.
4465 .vitem &%-q%&<&'qflags'&><&'time'&>
4466 .cindex "queue runner" "starting periodically"
4467 .cindex "periodic queue running"
4468 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4469 starting a queue runner process at intervals specified by the given time value
4470 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4471 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4472 single daemon process handles both functions. A common way of starting up a
4473 combined daemon at system boot time is to use a command such as
4475 /usr/exim/bin/exim -bd -q30m
4477 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4478 process every 30 minutes.
4480 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4481 pid file is written unless one is explicitly requested by the &%-oP%& option.
4483 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4485 This option is synonymous with &%-R%&. It is provided for Sendmail
4488 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4490 This option is synonymous with &%-S%&.
4492 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4494 .cindex "queue runner" "for specific recipients"
4495 .cindex "delivery" "to given domain"
4496 .cindex "domain" "delivery to"
4497 The <&'rsflags'&> may be empty, in which case the white space before the string
4498 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4499 which are the possible values for <&'rsflags'&>. White space is required if
4500 <&'rsflags'&> is not empty.
4502 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4503 perform a single queue run, except that, when scanning the messages on the
4504 queue, Exim processes only those that have at least one undelivered recipient
4505 address containing the given string, which is checked in a case-independent
4506 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4507 regular expression; otherwise it is a literal string.
4509 If you want to do periodic queue runs for messages with specific recipients,
4510 you can combine &%-R%& with &%-q%& and a time value. For example:
4512 exim -q25m -R @special.domain.example
4514 This example does a queue run for messages with recipients in the given domain
4515 every 25 minutes. Any additional flags that are specified with &%-q%& are
4516 applied to each queue run.
4518 Once a message is selected for delivery by this mechanism, all its addresses
4519 are processed. For the first selected message, Exim overrides any retry
4520 information and forces a delivery attempt for each undelivered address. This
4521 means that if delivery of any address in the first message is successful, any
4522 existing retry information is deleted, and so delivery attempts for that
4523 address in subsequently selected messages (which are processed without forcing)
4524 will run. However, if delivery of any address does not succeed, the retry
4525 information is updated, and in subsequently selected messages, the failing
4526 address will be skipped.
4528 .cindex "frozen messages" "forcing delivery"
4529 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4530 all selected messages, not just the first; frozen messages are included when
4533 The &%-R%& option makes it straightforward to initiate delivery of all messages
4534 to a given domain after a host has been down for some time. When the SMTP
4535 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4536 effect is to run Exim with the &%-R%& option, but it can be configured to run
4537 an arbitrary command instead.
4541 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4543 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4545 .cindex "delivery" "from given sender"
4546 .cindex "queue runner" "for specific senders"
4547 This option acts like &%-R%& except that it checks the string against each
4548 message's sender instead of against the recipients. If &%-R%& is also set, both
4549 conditions must be met for a message to be selected. If either of the options
4550 has &'f'& or &'ff'& in its flags, the associated action is taken.
4552 .vitem &%-Tqt%&&~<&'times'&>
4554 This is an option that is exclusively for use by the Exim testing suite. It is not
4555 recognized when Exim is run normally. It allows for the setting up of explicit
4556 &"queue times"& so that various warning/retry features can be tested.
4560 .cindex "recipient" "extracting from header lines"
4561 .cindex "&'Bcc:'& header line"
4562 .cindex "&'Cc:'& header line"
4563 .cindex "&'To:'& header line"
4564 When Exim is receiving a locally-generated, non-SMTP message on its standard
4565 input, the &%-t%& option causes the recipients of the message to be obtained
4566 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4567 from the command arguments. The addresses are extracted before any rewriting
4568 takes place and the &'Bcc:'& header line, if present, is then removed.
4570 .cindex "Sendmail compatibility" "&%-t%& option"
4571 If the command has any arguments, they specify addresses to which the message
4572 is &'not'& to be delivered. That is, the argument addresses are removed from
4573 the recipients list obtained from the headers. This is compatible with Smail 3
4574 and in accordance with the documented behaviour of several versions of
4575 Sendmail, as described in man pages on a number of operating systems (e.g.
4576 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4577 argument addresses to those obtained from the headers, and the O'Reilly
4578 Sendmail book documents it that way. Exim can be made to add argument addresses
4579 instead of subtracting them by setting the option
4580 &%extract_addresses_remove_arguments%& false.
4582 .cindex "&%Resent-%& header lines" "with &%-t%&"
4583 If there are any &%Resent-%& header lines in the message, Exim extracts
4584 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4585 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4586 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4587 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4589 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4590 message is resent several times). The RFC also specifies that they should be
4591 added at the front of the message, and separated by &'Received:'& lines. It is
4592 not at all clear how &%-t%& should operate in the present of multiple sets,
4593 nor indeed exactly what constitutes a &"set"&.
4594 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4595 are often added at the end of the header, and if a message is resent more than
4596 once, it is common for the original set of &%Resent-%& headers to be renamed as
4597 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4601 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4602 compatibility with Sendmail.
4604 .vitem &%-tls-on-connect%&
4605 .oindex "&%-tls-on-connect%&"
4606 .cindex "TLS" "use without STARTTLS"
4607 .cindex "TLS" "automatic start"
4608 This option is available when Exim is compiled with TLS support. It forces all
4609 incoming SMTP connections to behave as if the incoming port is listed in the
4610 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4611 &<<CHAPTLS>>& for further details.
4616 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4617 Sendmail uses this option for &"initial message submission"&, and its
4618 documentation states that in future releases, it may complain about
4619 syntactically invalid messages rather than fixing them when this flag is not
4620 set. Exim ignores this option.
4624 This option causes Exim to write information to the standard error stream,
4625 describing what it is doing. In particular, it shows the log lines for
4626 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4627 dialogue is shown. Some of the log lines shown may not actually be written to
4628 the log if the setting of &%log_selector%& discards them. Any relevant
4629 selectors are shown with each log line. If none are shown, the logging is
4634 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4635 National Language Support extended characters in the body of the mail item"&).
4636 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4639 .vitem &%-X%&&~<&'logfile'&>
4641 This option is interpreted by Sendmail to cause debug information to be sent
4642 to the named file. It is ignored by Exim.
4649 . ////////////////////////////////////////////////////////////////////////////
4650 . Insert a stylized DocBook comment here, to identify the end of the command
4651 . line options. This is for the benefit of the Perl script that automatically
4652 . creates a man page for the options.
4653 . ////////////////////////////////////////////////////////////////////////////
4656 <!-- === End of command line options === -->
4663 . ////////////////////////////////////////////////////////////////////////////
4664 . ////////////////////////////////////////////////////////////////////////////
4667 .chapter "The Exim run time configuration file" "CHAPconf" &&&
4668 "The runtime configuration file"
4670 .cindex "run time configuration"
4671 .cindex "configuration file" "general description"
4672 .cindex "CONFIGURE_FILE"
4673 .cindex "configuration file" "errors in"
4674 .cindex "error" "in configuration file"
4675 .cindex "return code" "for bad configuration"
4676 Exim uses a single run time configuration file that is read whenever an Exim
4677 binary is executed. Note that in normal operation, this happens frequently,
4678 because Exim is designed to operate in a distributed manner, without central
4681 If a syntax error is detected while reading the configuration file, Exim
4682 writes a message on the standard error, and exits with a non-zero return code.
4683 The message is also written to the panic log. &*Note*&: Only simple syntax
4684 errors can be detected at this time. The values of any expanded options are
4685 not checked until the expansion happens, even when the expansion does not
4686 actually alter the string.
4688 The name of the configuration file is compiled into the binary for security
4689 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4690 most configurations, this specifies a single file. However, it is permitted to
4691 give a colon-separated list of file names, in which case Exim uses the first
4692 existing file in the list.
4695 .cindex "EXIM_GROUP"
4696 .cindex "CONFIGURE_OWNER"
4697 .cindex "CONFIGURE_GROUP"
4698 .cindex "configuration file" "ownership"
4699 .cindex "ownership" "configuration file"
4700 The run time configuration file must be owned by root or by the user that is
4701 specified at compile time by the CONFIGURE_OWNER option (if set). The
4702 configuration file must not be world-writeable, or group-writeable unless its
4703 group is the root group or the one specified at compile time by the
4704 CONFIGURE_GROUP option.
4706 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4707 to root, anybody who is able to edit the run time configuration file has an
4708 easy way to run commands as root. If you specify a user or group in the
4709 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4710 who are members of that group will trivially be able to obtain root privileges.
4712 Up to Exim version 4.72, the run time configuration file was also permitted to
4713 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4714 since it offered a simple privilege escalation for any attacker who managed to
4715 compromise the Exim user account.
4717 A default configuration file, which will work correctly in simple situations,
4718 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4719 defines just one file name, the installation process copies the default
4720 configuration to a new file of that name if it did not previously exist. If
4721 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4722 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4727 .section "Using a different configuration file" "SECID40"
4728 .cindex "configuration file" "alternate"
4729 A one-off alternate configuration can be specified by the &%-C%& command line
4730 option, which may specify a single file or a list of files. However, when
4731 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4732 unless the argument for &%-C%& is identical to the built-in value from
4733 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4734 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4735 is useful mainly for checking the syntax of configuration files before
4736 installing them. No owner or group checks are done on a configuration file
4737 specified by &%-C%&, if root privilege has been dropped.
4739 Even the Exim user is not trusted to specify an arbitrary configuration file
4740 with the &%-C%& option to be used with root privileges, unless that file is
4741 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
4742 testing a configuration using &%-C%& right through message reception and
4743 delivery, even if the caller is root. The reception works, but by that time,
4744 Exim is running as the Exim user, so when it re-execs to regain privilege for
4745 the delivery, the use of &%-C%& causes privilege to be lost. However, root
4746 can test reception and delivery using two separate commands (one to put a
4747 message on the queue, using &%-odq%&, and another to do the delivery, using
4750 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4751 prefix string with which any file named in a &%-C%& command line option must
4752 start. In addition, the file name must not contain the sequence &"&`/../`&"&.
4753 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any file
4754 name can be used with &%-C%&.
4756 One-off changes to a configuration can be specified by the &%-D%& command line
4757 option, which defines and overrides values for macros used inside the
4758 configuration file. However, like &%-C%&, the use of this option by a
4759 non-privileged user causes Exim to discard its root privilege.
4760 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4761 completely disabled, and its use causes an immediate error exit.
4763 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
4764 to declare certain macro names trusted, such that root privilege will not
4765 necessarily be discarded.
4766 WHITELIST_D_MACROS defines a colon-separated list of macros which are
4767 considered safe and, if &%-D%& only supplies macros from this list, and the
4768 values are acceptable, then Exim will not give up root privilege if the caller
4769 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
4770 transition mechanism and is expected to be removed in the future. Acceptable
4771 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
4773 Some sites may wish to use the same Exim binary on different machines that
4774 share a file system, but to use different configuration files on each machine.
4775 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4776 looks for a file whose name is the configuration file name followed by a dot
4777 and the machine's node name, as obtained from the &[uname()]& function. If this
4778 file does not exist, the standard name is tried. This processing occurs for
4779 each file name in the list given by CONFIGURE_FILE or &%-C%&.
4781 In some esoteric situations different versions of Exim may be run under
4782 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4783 help with this. See the comments in &_src/EDITME_& for details.
4787 .section "Configuration file format" "SECTconffilfor"
4788 .cindex "configuration file" "format of"
4789 .cindex "format" "configuration file"
4790 Exim's configuration file is divided into a number of different parts. General
4791 option settings must always appear at the start of the file. The other parts
4792 are all optional, and may appear in any order. Each part other than the first
4793 is introduced by the word &"begin"& followed by the name of the part. The
4797 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
4800 .cindex "AUTH" "configuration"
4801 &'authenticators'&: Configuration settings for the authenticator drivers. These
4802 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4804 &'routers'&: Configuration settings for the router drivers. Routers process
4805 addresses and determine how the message is to be delivered (see chapters
4806 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
4808 &'transports'&: Configuration settings for the transport drivers. Transports
4809 define mechanisms for copying messages to destinations (see chapters
4810 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
4812 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
4813 If there is no retry section, or if it is empty (that is, no retry rules are
4814 defined), Exim will not retry deliveries. In this situation, temporary errors
4815 are treated the same as permanent errors. Retry rules are discussed in chapter
4818 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4819 when new addresses are generated during delivery. Rewriting is discussed in
4820 chapter &<<CHAPrewrite>>&.
4822 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4823 want to use this feature, you must set
4825 LOCAL_SCAN_HAS_OPTIONS=yes
4827 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
4828 facility are given in chapter &<<CHAPlocalscan>>&.
4831 .cindex "configuration file" "leading white space in"
4832 .cindex "configuration file" "trailing white space in"
4833 .cindex "white space" "in configuration file"
4834 Leading and trailing white space in configuration lines is always ignored.
4836 Blank lines in the file, and lines starting with a # character (ignoring
4837 leading white space) are treated as comments and are ignored. &*Note*&: A
4838 # character other than at the beginning of a line is not treated specially,
4839 and does not introduce a comment.
4841 Any non-comment line can be continued by ending it with a backslash. Note that
4842 the general rule for white space means that trailing white space after the
4843 backslash and leading white space at the start of continuation
4844 lines is ignored. Comment lines beginning with # (but not empty lines) may
4845 appear in the middle of a sequence of continuation lines.
4847 A convenient way to create a configuration file is to start from the
4848 default, which is supplied in &_src/configure.default_&, and add, delete, or
4849 change settings as required.
4851 The ACLs, retry rules, and rewriting rules have their own syntax which is
4852 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
4853 respectively. The other parts of the configuration file have some syntactic
4854 items in common, and these are described below, from section &<<SECTcos>>&
4855 onwards. Before that, the inclusion, macro, and conditional facilities are
4860 .section "File inclusions in the configuration file" "SECID41"
4861 .cindex "inclusions in configuration file"
4862 .cindex "configuration file" "including other files"
4863 .cindex "&`.include`& in configuration file"
4864 .cindex "&`.include_if_exists`& in configuration file"
4865 You can include other files inside Exim's run time configuration file by
4868 &`.include`& <&'file name'&>
4869 &`.include_if_exists`& <&'file name'&>
4871 on a line by itself. Double quotes round the file name are optional. If you use
4872 the first form, a configuration error occurs if the file does not exist; the
4873 second form does nothing for non-existent files. In all cases, an absolute file
4876 Includes may be nested to any depth, but remember that Exim reads its
4877 configuration file often, so it is a good idea to keep them to a minimum.
4878 If you change the contents of an included file, you must HUP the daemon,
4879 because an included file is read only when the configuration itself is read.
4881 The processing of inclusions happens early, at a physical line level, so, like
4882 comment lines, an inclusion can be used in the middle of an option setting,
4885 hosts_lookup = a.b.c \
4888 Include processing happens after macro processing (see below). Its effect is to
4889 process the lines of the included file as if they occurred inline where the
4894 .section "Macros in the configuration file" "SECTmacrodefs"
4895 .cindex "macro" "description of"
4896 .cindex "configuration file" "macros"
4897 If a line in the main part of the configuration (that is, before the first
4898 &"begin"& line) begins with an upper case letter, it is taken as a macro
4899 definition, and must be of the form
4901 <&'name'&> = <&'rest of line'&>
4903 The name must consist of letters, digits, and underscores, and need not all be
4904 in upper case, though that is recommended. The rest of the line, including any
4905 continuations, is the replacement text, and has leading and trailing white
4906 space removed. Quotes are not removed. The replacement text can never end with
4907 a backslash character, but this doesn't seem to be a serious limitation.
4909 Macros may also be defined between router, transport, authenticator, or ACL
4910 definitions. They may not, however, be defined within an individual driver or
4911 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
4913 .section "Macro substitution" "SECID42"
4914 Once a macro is defined, all subsequent lines in the file (and any included
4915 files) are scanned for the macro name; if there are several macros, the line is
4916 scanned for each in turn, in the order in which the macros are defined. The
4917 replacement text is not re-scanned for the current macro, though it is scanned
4918 for subsequently defined macros. For this reason, a macro name may not contain
4919 the name of a previously defined macro as a substring. You could, for example,
4922 &`ABCD_XYZ = `&<&'something'&>
4923 &`ABCD = `&<&'something else'&>
4925 but putting the definitions in the opposite order would provoke a configuration
4926 error. Macro expansion is applied to individual physical lines from the file,
4927 before checking for line continuation or file inclusion (see above). If a line
4928 consists solely of a macro name, and the expansion of the macro is empty, the
4929 line is ignored. A macro at the start of a line may turn the line into a
4930 comment line or a &`.include`& line.
4933 .section "Redefining macros" "SECID43"
4934 Once defined, the value of a macro can be redefined later in the configuration
4935 (or in an included file). Redefinition is specified by using &'=='& instead of
4940 MAC == updated value
4942 Redefinition does not alter the order in which the macros are applied to the
4943 subsequent lines of the configuration file. It is still the same order in which
4944 the macros were originally defined. All that changes is the macro's value.
4945 Redefinition makes it possible to accumulate values. For example:
4949 MAC == MAC and something added
4951 This can be helpful in situations where the configuration file is built
4952 from a number of other files.
4954 .section "Overriding macro values" "SECID44"
4955 The values set for macros in the configuration file can be overridden by the
4956 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
4957 used, unless called by root or the Exim user. A definition on the command line
4958 using the &%-D%& option causes all definitions and redefinitions within the
4963 .section "Example of macro usage" "SECID45"
4964 As an example of macro usage, consider a configuration where aliases are looked
4965 up in a MySQL database. It helps to keep the file less cluttered if long
4966 strings such as SQL statements are defined separately as macros, for example:
4968 ALIAS_QUERY = select mailbox from user where \
4969 login='${quote_mysql:$local_part}';
4971 This can then be used in a &(redirect)& router setting like this:
4973 data = ${lookup mysql{ALIAS_QUERY}}
4975 In earlier versions of Exim macros were sometimes used for domain, host, or
4976 address lists. In Exim 4 these are handled better by named lists &-- see
4977 section &<<SECTnamedlists>>&.
4980 .section "Conditional skips in the configuration file" "SECID46"
4981 .cindex "configuration file" "conditional skips"
4982 .cindex "&`.ifdef`&"
4983 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
4984 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
4985 portions of the configuration file. The processing happens whenever the file is
4986 read (that is, when an Exim binary starts to run).
4988 The implementation is very simple. Instances of the first four directives must
4989 be followed by text that includes the names of one or macros. The condition
4990 that is tested is whether or not any macro substitution has taken place in the
4994 message_size_limit = 50M
4996 message_size_limit = 100M
4999 sets a message size limit of 50M if the macro &`AAA`& is defined, and 100M
5000 otherwise. If there is more than one macro named on the line, the condition
5001 is true if any of them are defined. That is, it is an &"or"& condition. To
5002 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5004 Although you can use a macro expansion to generate one of these directives,
5005 it is not very useful, because the condition &"there was a macro substitution
5006 in this line"& will always be true.
5008 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5009 to clarify complicated nestings.
5013 .section "Common option syntax" "SECTcos"
5014 .cindex "common option syntax"
5015 .cindex "syntax of common options"
5016 .cindex "configuration file" "common option syntax"
5017 For the main set of options, driver options, and &[local_scan()]& options,
5018 each setting is on a line by itself, and starts with a name consisting of
5019 lower-case letters and underscores. Many options require a data value, and in
5020 these cases the name must be followed by an equals sign (with optional white
5021 space) and then the value. For example:
5023 qualify_domain = mydomain.example.com
5025 .cindex "hiding configuration option values"
5026 .cindex "configuration options" "hiding value of"
5027 .cindex "options" "hiding value of"
5028 Some option settings may contain sensitive data, for example, passwords for
5029 accessing databases. To stop non-admin users from using the &%-bP%& command
5030 line option to read these values, you can precede the option settings with the
5031 word &"hide"&. For example:
5033 hide mysql_servers = localhost/users/admin/secret-password
5035 For non-admin users, such options are displayed like this:
5037 mysql_servers = <value not displayable>
5039 If &"hide"& is used on a driver option, it hides the value of that option on
5040 all instances of the same driver.
5042 The following sections describe the syntax used for the different data types
5043 that are found in option settings.
5046 .section "Boolean options" "SECID47"
5047 .cindex "format" "boolean"
5048 .cindex "boolean configuration values"
5049 .oindex "&%no_%&&'xxx'&"
5050 .oindex "&%not_%&&'xxx'&"
5051 Options whose type is given as boolean are on/off switches. There are two
5052 different ways of specifying such options: with and without a data value. If
5053 the option name is specified on its own without data, the switch is turned on;
5054 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5055 boolean options may be followed by an equals sign and one of the words
5056 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5057 the following two settings have exactly the same effect:
5062 The following two lines also have the same (opposite) effect:
5067 You can use whichever syntax you prefer.
5072 .section "Integer values" "SECID48"
5073 .cindex "integer configuration values"
5074 .cindex "format" "integer"
5075 If an option's type is given as &"integer"&, the value can be given in decimal,
5076 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5077 number is assumed. Otherwise, it is treated as an octal number unless it starts
5078 with the characters &"0x"&, in which case the remainder is interpreted as a
5081 If an integer value is followed by the letter K, it is multiplied by 1024; if
5082 it is followed by the letter M, it is multiplied by 1024x1024. When the values
5083 of integer option settings are output, values which are an exact multiple of
5084 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5085 and M. The printing style is independent of the actual input format that was
5089 .section "Octal integer values" "SECID49"
5090 .cindex "integer format"
5091 .cindex "format" "octal integer"
5092 If an option's type is given as &"octal integer"&, its value is always
5093 interpreted as an octal number, whether or not it starts with the digit zero.
5094 Such options are always output in octal.
5097 .section "Fixed point numbers" "SECID50"
5098 .cindex "fixed point configuration values"
5099 .cindex "format" "fixed point"
5100 If an option's type is given as &"fixed-point"&, its value must be a decimal
5101 integer, optionally followed by a decimal point and up to three further digits.
5105 .section "Time intervals" "SECTtimeformat"
5106 .cindex "time interval" "specifying in configuration"
5107 .cindex "format" "time interval"
5108 A time interval is specified as a sequence of numbers, each followed by one of
5109 the following letters, with no intervening white space:
5119 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5120 intervals are output in the same format. Exim does not restrict the values; it
5121 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5125 .section "String values" "SECTstrings"
5126 .cindex "string" "format of configuration values"
5127 .cindex "format" "string"
5128 If an option's type is specified as &"string"&, the value can be specified with
5129 or without double-quotes. If it does not start with a double-quote, the value
5130 consists of the remainder of the line plus any continuation lines, starting at
5131 the first character after any leading white space, with trailing white space
5132 removed, and with no interpretation of the characters in the string. Because
5133 Exim removes comment lines (those beginning with #) at an early stage, they can
5134 appear in the middle of a multi-line string. The following two settings are
5135 therefore equivalent:
5137 trusted_users = uucp:mail
5138 trusted_users = uucp:\
5139 # This comment line is ignored
5142 .cindex "string" "quoted"
5143 .cindex "escape characters in quoted strings"
5144 If a string does start with a double-quote, it must end with a closing
5145 double-quote, and any backslash characters other than those used for line
5146 continuation are interpreted as escape characters, as follows:
5149 .irow &`\\`& "single backslash"
5150 .irow &`\n`& "newline"
5151 .irow &`\r`& "carriage return"
5153 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5154 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5158 If a backslash is followed by some other character, including a double-quote
5159 character, that character replaces the pair.
5161 Quoting is necessary only if you want to make use of the backslash escapes to
5162 insert special characters, or if you need to specify a value with leading or
5163 trailing spaces. These cases are rare, so quoting is almost never needed in
5164 current versions of Exim. In versions of Exim before 3.14, quoting was required
5165 in order to continue lines, so you may come across older configuration files
5166 and examples that apparently quote unnecessarily.
5169 .section "Expanded strings" "SECID51"
5170 .cindex "expansion" "definition of"
5171 Some strings in the configuration file are subjected to &'string expansion'&,
5172 by which means various parts of the string may be changed according to the
5173 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5174 is as just described; in particular, the handling of backslashes in quoted
5175 strings is done as part of the input process, before expansion takes place.
5176 However, backslash is also an escape character for the expander, so any
5177 backslashes that are required for that reason must be doubled if they are
5178 within a quoted configuration string.
5181 .section "User and group names" "SECID52"
5182 .cindex "user name" "format of"
5183 .cindex "format" "user name"
5184 .cindex "groups" "name format"
5185 .cindex "format" "group name"
5186 User and group names are specified as strings, using the syntax described
5187 above, but the strings are interpreted specially. A user or group name must
5188 either consist entirely of digits, or be a name that can be looked up using the
5189 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5192 .section "List construction" "SECTlistconstruct"
5193 .cindex "list" "syntax of in configuration"
5194 .cindex "format" "list item in configuration"
5195 .cindex "string" "list, definition of"
5196 The data for some configuration options is a list of items, with colon as the
5197 default separator. Many of these options are shown with type &"string list"& in
5198 the descriptions later in this document. Others are listed as &"domain list"&,
5199 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5200 are all the same; however, those other than &"string list"& are subject to
5201 particular kinds of interpretation, as described in chapter
5202 &<<CHAPdomhosaddlists>>&.
5204 In all these cases, the entire list is treated as a single string as far as the
5205 input syntax is concerned. The &%trusted_users%& setting in section
5206 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5207 in a list, it must be entered as two colons. Leading and trailing white space
5208 on each item in a list is ignored. This makes it possible to include items that
5209 start with a colon, and in particular, certain forms of IPv6 address. For
5212 local_interfaces = 127.0.0.1 : ::::1
5214 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5216 &*Note*&: Although leading and trailing white space is ignored in individual
5217 list items, it is not ignored when parsing the list. The space after the first
5218 colon in the example above is necessary. If it were not there, the list would
5219 be interpreted as the two items 127.0.0.1:: and 1.
5221 .section "Changing list separators" "SECID53"
5222 .cindex "list separator" "changing"
5223 .cindex "IPv6" "addresses in lists"
5224 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5225 introduced to allow the separator character to be changed. If a list begins
5226 with a left angle bracket, followed by any punctuation character, that
5227 character is used instead of colon as the list separator. For example, the list
5228 above can be rewritten to use a semicolon separator like this:
5230 local_interfaces = <; 127.0.0.1 ; ::1
5232 This facility applies to all lists, with the exception of the list in
5233 &%log_file_path%&. It is recommended that the use of non-colon separators be
5234 confined to circumstances where they really are needed.
5236 .cindex "list separator" "newline as"
5237 .cindex "newline" "as list separator"
5238 It is also possible to use newline and other control characters (those with
5239 code values less than 32, plus DEL) as separators in lists. Such separators
5240 must be provided literally at the time the list is processed. For options that
5241 are string-expanded, you can write the separator using a normal escape
5242 sequence. This will be processed by the expander before the string is
5243 interpreted as a list. For example, if a newline-separated list of domains is
5244 generated by a lookup, you can process it directly by a line such as this:
5246 domains = <\n ${lookup mysql{.....}}
5248 This avoids having to change the list separator in such data. You are unlikely
5249 to want to use a control character as a separator in an option that is not
5250 expanded, because the value is literal text. However, it can be done by giving
5251 the value in quotes. For example:
5253 local_interfaces = "<\n 127.0.0.1 \n ::1"
5255 Unlike printing character separators, which can be included in list items by
5256 doubling, it is not possible to include a control character as data when it is
5257 set as the separator. Two such characters in succession are interpreted as
5258 enclosing an empty list item.
5262 .section "Empty items in lists" "SECTempitelis"
5263 .cindex "list" "empty item in"
5264 An empty item at the end of a list is always ignored. In other words, trailing
5265 separator characters are ignored. Thus, the list in
5267 senders = user@domain :
5269 contains only a single item. If you want to include an empty string as one item
5270 in a list, it must not be the last item. For example, this list contains three
5271 items, the second of which is empty:
5273 senders = user1@domain : : user2@domain
5275 &*Note*&: There must be white space between the two colons, as otherwise they
5276 are interpreted as representing a single colon data character (and the list
5277 would then contain just one item). If you want to specify a list that contains
5278 just one, empty item, you can do it as in this example:
5282 In this case, the first item is empty, and the second is discarded because it
5283 is at the end of the list.
5288 .section "Format of driver configurations" "SECTfordricon"
5289 .cindex "drivers" "configuration format"
5290 There are separate parts in the configuration for defining routers, transports,
5291 and authenticators. In each part, you are defining a number of driver
5292 instances, each with its own set of options. Each driver instance is defined by
5293 a sequence of lines like this:
5295 <&'instance name'&>:
5300 In the following example, the instance name is &(localuser)&, and it is
5301 followed by three options settings:
5306 transport = local_delivery
5308 For each driver instance, you specify which Exim code module it uses &-- by the
5309 setting of the &%driver%& option &-- and (optionally) some configuration
5310 settings. For example, in the case of transports, if you want a transport to
5311 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5312 a local file you would use the &(appendfile)& driver. Each of the drivers is
5313 described in detail in its own separate chapter later in this manual.
5315 You can have several routers, transports, or authenticators that are based on
5316 the same underlying driver (each must have a different instance name).
5318 The order in which routers are defined is important, because addresses are
5319 passed to individual routers one by one, in order. The order in which
5320 transports are defined does not matter at all. The order in which
5321 authenticators are defined is used only when Exim, as a client, is searching
5322 them to find one that matches an authentication mechanism offered by the
5325 .cindex "generic options"
5326 .cindex "options" "generic &-- definition of"
5327 Within a driver instance definition, there are two kinds of option: &'generic'&
5328 and &'private'&. The generic options are those that apply to all drivers of the
5329 same type (that is, all routers, all transports or all authenticators). The
5330 &%driver%& option is a generic option that must appear in every definition.
5331 .cindex "private options"
5332 The private options are special for each driver, and none need appear, because
5333 they all have default values.
5335 The options may appear in any order, except that the &%driver%& option must
5336 precede any private options, since these depend on the particular driver. For
5337 this reason, it is recommended that &%driver%& always be the first option.
5339 Driver instance names, which are used for reference in log entries and
5340 elsewhere, can be any sequence of letters, digits, and underscores (starting
5341 with a letter) and must be unique among drivers of the same type. A router and
5342 a transport (for example) can each have the same name, but no two router
5343 instances can have the same name. The name of a driver instance should not be
5344 confused with the name of the underlying driver module. For example, the
5345 configuration lines:
5350 create an instance of the &(smtp)& transport driver whose name is
5351 &(remote_smtp)&. The same driver code can be used more than once, with
5352 different instance names and different option settings each time. A second
5353 instance of the &(smtp)& transport, with different options, might be defined
5359 command_timeout = 10s
5361 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5362 these transport instances from routers, and these names would appear in log
5365 Comment lines may be present in the middle of driver specifications. The full
5366 list of option settings for any particular driver instance, including all the
5367 defaulted values, can be extracted by making use of the &%-bP%& command line
5375 . ////////////////////////////////////////////////////////////////////////////
5376 . ////////////////////////////////////////////////////////////////////////////
5378 .chapter "The default configuration file" "CHAPdefconfil"
5379 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5380 .cindex "default" "configuration file &""walk through""&"
5381 The default configuration file supplied with Exim as &_src/configure.default_&
5382 is sufficient for a host with simple mail requirements. As an introduction to
5383 the way Exim is configured, this chapter &"walks through"& the default
5384 configuration, giving brief explanations of the settings. Detailed descriptions
5385 of the options are given in subsequent chapters. The default configuration file
5386 itself contains extensive comments about ways you might want to modify the
5387 initial settings. However, note that there are many options that are not
5388 mentioned at all in the default configuration.
5392 .section "Main configuration settings" "SECTdefconfmain"
5393 The main (global) configuration option settings must always come first in the
5394 file. The first thing you'll see in the file, after some initial comments, is
5397 # primary_hostname =
5399 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5400 to know the official, fully qualified name of your host, and this is where you
5401 can specify it. However, in most cases you do not need to set this option. When
5402 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5404 The first three non-comment configuration lines are as follows:
5406 domainlist local_domains = @
5407 domainlist relay_to_domains =
5408 hostlist relay_from_hosts = 127.0.0.1
5410 These are not, in fact, option settings. They are definitions of two named
5411 domain lists and one named host list. Exim allows you to give names to lists of
5412 domains, hosts, and email addresses, in order to make it easier to manage the
5413 configuration file (see section &<<SECTnamedlists>>&).
5415 The first line defines a domain list called &'local_domains'&; this is used
5416 later in the configuration to identify domains that are to be delivered
5419 .cindex "@ in a domain list"
5420 There is just one item in this list, the string &"@"&. This is a special form
5421 of entry which means &"the name of the local host"&. Thus, if the local host is
5422 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5423 be delivered locally. Because the local host's name is referenced indirectly,
5424 the same configuration file can be used on different hosts.
5426 The second line defines a domain list called &'relay_to_domains'&, but the
5427 list itself is empty. Later in the configuration we will come to the part that
5428 controls mail relaying through the local host; it allows relaying to any
5429 domains in this list. By default, therefore, no relaying on the basis of a mail
5430 domain is permitted.
5432 The third line defines a host list called &'relay_from_hosts'&. This list is
5433 used later in the configuration to permit relaying from any host or IP address
5434 that matches the list. The default contains just the IP address of the IPv4
5435 loopback interface, which means that processes on the local host are able to
5436 submit mail for relaying by sending it over TCP/IP to that interface. No other
5437 hosts are permitted to submit messages for relaying.
5439 Just to be sure there's no misunderstanding: at this point in the configuration
5440 we aren't actually setting up any controls. We are just defining some domains
5441 and hosts that will be used in the controls that are specified later.
5443 The next two configuration lines are genuine option settings:
5445 acl_smtp_rcpt = acl_check_rcpt
5446 acl_smtp_data = acl_check_data
5448 These options specify &'Access Control Lists'& (ACLs) that are to be used
5449 during an incoming SMTP session for every recipient of a message (every RCPT
5450 command), and after the contents of the message have been received,
5451 respectively. The names of the lists are &'acl_check_rcpt'& and
5452 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5453 section of the configuration. The RCPT ACL controls which recipients are
5454 accepted for an incoming message &-- if a configuration does not provide an ACL
5455 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5456 contents of a message to be checked.
5458 Two commented-out option settings are next:
5460 # av_scanner = clamd:/tmp/clamd
5461 # spamd_address = 127.0.0.1 783
5463 These are example settings that can be used when Exim is compiled with the
5464 content-scanning extension. The first specifies the interface to the virus
5465 scanner, and the second specifies the interface to SpamAssassin. Further
5466 details are given in chapter &<<CHAPexiscan>>&.
5468 Three more commented-out option settings follow:
5470 # tls_advertise_hosts = *
5471 # tls_certificate = /etc/ssl/exim.crt
5472 # tls_privatekey = /etc/ssl/exim.pem
5474 These are example settings that can be used when Exim is compiled with
5475 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5476 first one specifies the list of clients that are allowed to use TLS when
5477 connecting to this server; in this case the wildcard means all clients. The
5478 other options specify where Exim should find its TLS certificate and private
5479 key, which together prove the server's identity to any clients that connect.
5480 More details are given in chapter &<<CHAPTLS>>&.
5482 Another two commented-out option settings follow:
5484 # daemon_smtp_ports = 25 : 465 : 587
5485 # tls_on_connect_ports = 465
5487 .cindex "port" "465 and 587"
5488 .cindex "port" "for message submission"
5489 .cindex "message" "submission, ports for"
5490 .cindex "ssmtp protocol"
5491 .cindex "smtps protocol"
5492 .cindex "SMTP" "ssmtp protocol"
5493 .cindex "SMTP" "smtps protocol"
5494 These options provide better support for roaming users who wish to use this
5495 server for message submission. They are not much use unless you have turned on
5496 TLS (as described in the previous paragraph) and authentication (about which
5497 more in section &<<SECTdefconfauth>>&). The usual SMTP port 25 is often blocked
5498 on end-user networks, so RFC 4409 specifies that message submission should use
5499 port 587 instead. However some software (notably Microsoft Outlook) cannot be
5500 configured to use port 587 correctly, so these settings also enable the
5501 non-standard &"smtps"& (aka &"ssmtp"&) port 465 (see section
5502 &<<SECTsupobssmt>>&).
5504 Two more commented-out options settings follow:
5507 # qualify_recipient =
5509 The first of these specifies a domain that Exim uses when it constructs a
5510 complete email address from a local login name. This is often needed when Exim
5511 receives a message from a local process. If you do not set &%qualify_domain%&,
5512 the value of &%primary_hostname%& is used. If you set both of these options,
5513 you can have different qualification domains for sender and recipient
5514 addresses. If you set only the first one, its value is used in both cases.
5516 .cindex "domain literal" "recognizing format"
5517 The following line must be uncommented if you want Exim to recognize
5518 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5519 (an IP address within square brackets) instead of a named domain.
5521 # allow_domain_literals
5523 The RFCs still require this form, but many people think that in the modern
5524 Internet it makes little sense to permit mail to be sent to specific hosts by
5525 quoting their IP addresses. This ancient format has been used by people who
5526 try to abuse hosts by using them for unwanted relaying. However, some
5527 people believe there are circumstances (for example, messages addressed to
5528 &'postmaster'&) where domain literals are still useful.
5530 The next configuration line is a kind of trigger guard:
5534 It specifies that no delivery must ever be run as the root user. The normal
5535 convention is to set up &'root'& as an alias for the system administrator. This
5536 setting is a guard against slips in the configuration.
5537 The list of users specified by &%never_users%& is not, however, the complete
5538 list; the build-time configuration in &_Local/Makefile_& has an option called
5539 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5540 contents of &%never_users%& are added to this list. By default
5541 FIXED_NEVER_USERS also specifies root.
5543 When a remote host connects to Exim in order to send mail, the only information
5544 Exim has about the host's identity is its IP address. The next configuration
5549 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5550 in order to get a host name. This improves the quality of the logging
5551 information, but if you feel it is too expensive, you can remove it entirely,
5552 or restrict the lookup to hosts on &"nearby"& networks.
5553 Note that it is not always possible to find a host name from an IP address,
5554 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5557 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5558 1413 (hence their names):
5561 rfc1413_query_timeout = 0s
5563 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5564 Few hosts offer RFC1413 service these days; calls have to be
5565 terminated by a timeout and this needlessly delays the startup
5566 of an incoming SMTP connection.
5567 If you have hosts for which you trust RFC1413 and need this
5568 information, you can change this.
5570 This line enables an efficiency SMTP option. It is negociated by clients
5571 and not expected to cause problems but can be disabled if needed.
5576 When Exim receives messages over SMTP connections, it expects all addresses to
5577 be fully qualified with a domain, as required by the SMTP definition. However,
5578 if you are running a server to which simple clients submit messages, you may
5579 find that they send unqualified addresses. The two commented-out options:
5581 # sender_unqualified_hosts =
5582 # recipient_unqualified_hosts =
5584 show how you can specify hosts that are permitted to send unqualified sender
5585 and recipient addresses, respectively.
5587 The &%percent_hack_domains%& option is also commented out:
5589 # percent_hack_domains =
5591 It provides a list of domains for which the &"percent hack"& is to operate.
5592 This is an almost obsolete form of explicit email routing. If you do not know
5593 anything about it, you can safely ignore this topic.
5595 The last two settings in the main part of the default configuration are
5596 concerned with messages that have been &"frozen"& on Exim's queue. When a
5597 message is frozen, Exim no longer continues to try to deliver it. Freezing
5598 occurs when a bounce message encounters a permanent failure because the sender
5599 address of the original message that caused the bounce is invalid, so the
5600 bounce cannot be delivered. This is probably the most common case, but there
5601 are also other conditions that cause freezing, and frozen messages are not
5602 always bounce messages.
5604 ignore_bounce_errors_after = 2d
5605 timeout_frozen_after = 7d
5607 The first of these options specifies that failing bounce messages are to be
5608 discarded after 2 days on the queue. The second specifies that any frozen
5609 message (whether a bounce message or not) is to be timed out (and discarded)
5610 after a week. In this configuration, the first setting ensures that no failing
5611 bounce message ever lasts a week.
5615 .section "ACL configuration" "SECID54"
5616 .cindex "default" "ACLs"
5617 .cindex "&ACL;" "default configuration"
5618 In the default configuration, the ACL section follows the main configuration.
5619 It starts with the line
5623 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5624 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5625 and &%acl_smtp_data%& above.
5627 .cindex "RCPT" "ACL for"
5628 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5629 RCPT command specifies one of the message's recipients. The ACL statements
5630 are considered in order, until the recipient address is either accepted or
5631 rejected. The RCPT command is then accepted or rejected, according to the
5632 result of the ACL processing.
5636 This line, consisting of a name terminated by a colon, marks the start of the
5641 This ACL statement accepts the recipient if the sending host matches the list.
5642 But what does that strange list mean? It doesn't actually contain any host
5643 names or IP addresses. The presence of the colon puts an empty item in the
5644 list; Exim matches this only if the incoming message did not come from a remote
5645 host, because in that case, the remote hostname is empty. The colon is
5646 important. Without it, the list itself is empty, and can never match anything.
5648 What this statement is doing is to accept unconditionally all recipients in
5649 messages that are submitted by SMTP from local processes using the standard
5650 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5653 deny message = Restricted characters in address
5654 domains = +local_domains
5655 local_parts = ^[.] : ^.*[@%!/|]
5657 deny message = Restricted characters in address
5658 domains = !+local_domains
5659 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5661 These statements are concerned with local parts that contain any of the
5662 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5663 Although these characters are entirely legal in local parts (in the case of
5664 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5665 in Internet mail addresses.
5667 The first three have in the past been associated with explicitly routed
5668 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5669 option). Addresses containing these characters are regularly tried by spammers
5670 in an attempt to bypass relaying restrictions, and also by open relay testing
5671 programs. Unless you really need them it is safest to reject these characters
5672 at this early stage. This configuration is heavy-handed in rejecting these
5673 characters for all messages it accepts from remote hosts. This is a deliberate
5674 policy of being as safe as possible.
5676 The first rule above is stricter, and is applied to messages that are addressed
5677 to one of the local domains handled by this host. This is implemented by the
5678 first condition, which restricts it to domains that are listed in the
5679 &'local_domains'& domain list. The &"+"& character is used to indicate a
5680 reference to a named list. In this configuration, there is just one domain in
5681 &'local_domains'&, but in general there may be many.
5683 The second condition on the first statement uses two regular expressions to
5684 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5685 or &"|"&. If you have local accounts that include these characters, you will
5686 have to modify this rule.
5688 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5689 allows them because they have been encountered in practice. (Consider the
5690 common convention of local parts constructed as
5691 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5692 the author of Exim, who has no second initial.) However, a local part starting
5693 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5694 file name (for example, for a mailing list). This is also true for local parts
5695 that contain slashes. A pipe symbol can also be troublesome if the local part
5696 is incorporated unthinkingly into a shell command line.
5698 The second rule above applies to all other domains, and is less strict. This
5699 allows your own users to send outgoing messages to sites that use slashes
5700 and vertical bars in their local parts. It blocks local parts that begin
5701 with a dot, slash, or vertical bar, but allows these characters within the
5702 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5703 and &"!"& is blocked, as before. The motivation here is to prevent your users
5704 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5706 accept local_parts = postmaster
5707 domains = +local_domains
5709 This statement, which has two conditions, accepts an incoming address if the
5710 local part is &'postmaster'& and the domain is one of those listed in the
5711 &'local_domains'& domain list. The &"+"& character is used to indicate a
5712 reference to a named list. In this configuration, there is just one domain in
5713 &'local_domains'&, but in general there may be many.
5715 The presence of this statement means that mail to postmaster is never blocked
5716 by any of the subsequent tests. This can be helpful while sorting out problems
5717 in cases where the subsequent tests are incorrectly denying access.
5719 require verify = sender
5721 This statement requires the sender address to be verified before any subsequent
5722 ACL statement can be used. If verification fails, the incoming recipient
5723 address is refused. Verification consists of trying to route the address, to
5724 see if a bounce message could be delivered to it. In the case of remote
5725 addresses, basic verification checks only the domain, but &'callouts'& can be
5726 used for more verification if required. Section &<<SECTaddressverification>>&
5727 discusses the details of address verification.
5729 accept hosts = +relay_from_hosts
5730 control = submission
5732 This statement accepts the address if the message is coming from one of the
5733 hosts that are defined as being allowed to relay through this host. Recipient
5734 verification is omitted here, because in many cases the clients are dumb MUAs
5735 that do not cope well with SMTP error responses. For the same reason, the
5736 second line specifies &"submission mode"& for messages that are accepted. This
5737 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
5738 messages that are deficient in some way, for example, because they lack a
5739 &'Date:'& header line. If you are actually relaying out from MTAs, you should
5740 probably add recipient verification here, and disable submission mode.
5742 accept authenticated = *
5743 control = submission
5745 This statement accepts the address if the client host has authenticated itself.
5746 Submission mode is again specified, on the grounds that such messages are most
5747 likely to come from MUAs. The default configuration does not define any
5748 authenticators, though it does include some nearly complete commented-out
5749 examples described in &<<SECTdefconfauth>>&. This means that no client can in
5750 fact authenticate until you complete the authenticator definitions.
5752 require message = relay not permitted
5753 domains = +local_domains : +relay_to_domains
5755 This statement rejects the address if its domain is neither a local domain nor
5756 one of the domains for which this host is a relay.
5758 require verify = recipient
5760 This statement requires the recipient address to be verified; if verification
5761 fails, the address is rejected.
5763 # deny message = rejected because $sender_host_address \
5764 # is in a black list at $dnslist_domain\n\
5766 # dnslists = black.list.example
5768 # warn dnslists = black.list.example
5769 # add_header = X-Warning: $sender_host_address is in \
5770 # a black list at $dnslist_domain
5771 # log_message = found in $dnslist_domain
5773 These commented-out lines are examples of how you could configure Exim to check
5774 sending hosts against a DNS black list. The first statement rejects messages
5775 from blacklisted hosts, whereas the second just inserts a warning header
5778 # require verify = csa
5780 This commented-out line is an example of how you could turn on client SMTP
5781 authorization (CSA) checking. Such checks do DNS lookups for special SRV
5786 The final statement in the first ACL unconditionally accepts any recipient
5787 address that has successfully passed all the previous tests.
5791 This line marks the start of the second ACL, and names it. Most of the contents
5792 of this ACL are commented out:
5795 # message = This message contains a virus \
5798 These lines are examples of how to arrange for messages to be scanned for
5799 viruses when Exim has been compiled with the content-scanning extension, and a
5800 suitable virus scanner is installed. If the message is found to contain a
5801 virus, it is rejected with the given custom error message.
5803 # warn spam = nobody
5804 # message = X-Spam_score: $spam_score\n\
5805 # X-Spam_score_int: $spam_score_int\n\
5806 # X-Spam_bar: $spam_bar\n\
5807 # X-Spam_report: $spam_report
5809 These lines are an example of how to arrange for messages to be scanned by
5810 SpamAssassin when Exim has been compiled with the content-scanning extension,
5811 and SpamAssassin has been installed. The SpamAssassin check is run with
5812 &`nobody`& as its user parameter, and the results are added to the message as a
5813 series of extra header line. In this case, the message is not rejected,
5814 whatever the spam score.
5818 This final line in the DATA ACL accepts the message unconditionally.
5821 .section "Router configuration" "SECID55"
5822 .cindex "default" "routers"
5823 .cindex "routers" "default"
5824 The router configuration comes next in the default configuration, introduced
5829 Routers are the modules in Exim that make decisions about where to send
5830 messages. An address is passed to each router in turn, until it is either
5831 accepted, or failed. This means that the order in which you define the routers
5832 matters. Each router is fully described in its own chapter later in this
5833 manual. Here we give only brief overviews.
5836 # driver = ipliteral
5837 # domains = !+local_domains
5838 # transport = remote_smtp
5840 .cindex "domain literal" "default router"
5841 This router is commented out because the majority of sites do not want to
5842 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
5843 you uncomment this router, you also need to uncomment the setting of
5844 &%allow_domain_literals%& in the main part of the configuration.
5848 domains = ! +local_domains
5849 transport = remote_smtp
5850 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
5853 The first uncommented router handles addresses that do not involve any local
5854 domains. This is specified by the line
5856 domains = ! +local_domains
5858 The &%domains%& option lists the domains to which this router applies, but the
5859 exclamation mark is a negation sign, so the router is used only for domains
5860 that are not in the domain list called &'local_domains'& (which was defined at
5861 the start of the configuration). The plus sign before &'local_domains'&
5862 indicates that it is referring to a named list. Addresses in other domains are
5863 passed on to the following routers.
5865 The name of the router driver is &(dnslookup)&,
5866 and is specified by the &%driver%& option. Do not be confused by the fact that
5867 the name of this router instance is the same as the name of the driver. The
5868 instance name is arbitrary, but the name set in the &%driver%& option must be
5869 one of the driver modules that is in the Exim binary.
5871 The &(dnslookup)& router routes addresses by looking up their domains in the
5872 DNS in order to obtain a list of hosts to which the address is routed. If the
5873 router succeeds, the address is queued for the &(remote_smtp)& transport, as
5874 specified by the &%transport%& option. If the router does not find the domain
5875 in the DNS, no further routers are tried because of the &%no_more%& setting, so
5876 the address fails and is bounced.
5878 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
5879 be entirely ignored. This option is present because a number of cases have been
5880 encountered where MX records in the DNS point to host names
5881 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
5882 Completely ignoring these IP addresses causes Exim to fail to route the
5883 email address, so it bounces. Otherwise, Exim would log a routing problem, and
5884 continue to try to deliver the message periodically until the address timed
5891 data = ${lookup{$local_part}lsearch{/etc/aliases}}
5893 file_transport = address_file
5894 pipe_transport = address_pipe
5896 Control reaches this and subsequent routers only for addresses in the local
5897 domains. This router checks to see whether the local part is defined as an
5898 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
5899 data that it looks up from that file. If no data is found for the local part,
5900 the value of the &%data%& option is empty, causing the address to be passed to
5903 &_/etc/aliases_& is a conventional name for the system aliases file that is
5904 often used. That is why it is referenced by from the default configuration
5905 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
5906 &_Local/Makefile_& before building Exim.
5911 # local_part_suffix = +* : -*
5912 # local_part_suffix_optional
5913 file = $home/.forward
5918 file_transport = address_file
5919 pipe_transport = address_pipe
5920 reply_transport = address_reply
5922 This is the most complicated router in the default configuration. It is another
5923 redirection router, but this time it is looking for forwarding data set up by
5924 individual users. The &%check_local_user%& setting specifies a check that the
5925 local part of the address is the login name of a local user. If it is not, the
5926 router is skipped. The two commented options that follow &%check_local_user%&,
5929 # local_part_suffix = +* : -*
5930 # local_part_suffix_optional
5932 .vindex "&$local_part_suffix$&"
5933 show how you can specify the recognition of local part suffixes. If the first
5934 is uncommented, a suffix beginning with either a plus or a minus sign, followed
5935 by any sequence of characters, is removed from the local part and placed in the
5936 variable &$local_part_suffix$&. The second suffix option specifies that the
5937 presence of a suffix in the local part is optional. When a suffix is present,
5938 the check for a local login uses the local part with the suffix removed.
5940 When a local user account is found, the file called &_.forward_& in the user's
5941 home directory is consulted. If it does not exist, or is empty, the router
5942 declines. Otherwise, the contents of &_.forward_& are interpreted as
5943 redirection data (see chapter &<<CHAPredirect>>& for more details).
5945 .cindex "Sieve filter" "enabling in default router"
5946 Traditional &_.forward_& files contain just a list of addresses, pipes, or
5947 files. Exim supports this by default. However, if &%allow_filter%& is set (it
5948 is commented out by default), the contents of the file are interpreted as a set
5949 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
5950 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
5951 separate document entitled &'Exim's interfaces to mail filtering'&.
5953 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
5954 verifying addresses, or when running as a consequence of an SMTP EXPN command.
5955 There are two reasons for doing this:
5958 Whether or not a local user has a &_.forward_& file is not really relevant when
5959 checking an address for validity; it makes sense not to waste resources doing
5962 More importantly, when Exim is verifying addresses or handling an EXPN
5963 command during an SMTP session, it is running as the Exim user, not as root.
5964 The group is the Exim group, and no additional groups are set up.
5965 It may therefore not be possible for Exim to read users' &_.forward_& files at
5969 The setting of &%check_ancestor%& prevents the router from generating a new
5970 address that is the same as any previous address that was redirected. (This
5971 works round a problem concerning a bad interaction between aliasing and
5972 forwarding &-- see section &<<SECTredlocmai>>&).
5974 The final three option settings specify the transports that are to be used when
5975 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
5976 auto-reply, respectively. For example, if a &_.forward_& file contains
5978 a.nother@elsewhere.example, /home/spqr/archive
5980 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
5986 # local_part_suffix = +* : -*
5987 # local_part_suffix_optional
5988 transport = local_delivery
5990 The final router sets up delivery into local mailboxes, provided that the local
5991 part is the name of a local login, by accepting the address and assigning it to
5992 the &(local_delivery)& transport. Otherwise, we have reached the end of the
5993 routers, so the address is bounced. The commented suffix settings fulfil the
5994 same purpose as they do for the &(userforward)& router.
5997 .section "Transport configuration" "SECID56"
5998 .cindex "default" "transports"
5999 .cindex "transports" "default"
6000 Transports define mechanisms for actually delivering messages. They operate
6001 only when referenced from routers, so the order in which they are defined does
6002 not matter. The transports section of the configuration starts with
6006 One remote transport and four local transports are defined.
6012 This transport is used for delivering messages over SMTP connections.
6013 The list of remote hosts comes from the router.
6014 The &%hosts_try_prdr%& option enables an efficiency SMTP option.
6015 It is negotiated between client and server
6016 and not expected to cause problems but can be disabled if needed.
6017 All other options are defaulted.
6021 file = /var/mail/$local_part
6028 This &(appendfile)& transport is used for local delivery to user mailboxes in
6029 traditional BSD mailbox format. By default it runs under the uid and gid of the
6030 local user, which requires the sticky bit to be set on the &_/var/mail_&
6031 directory. Some systems use the alternative approach of running mail deliveries
6032 under a particular group instead of using the sticky bit. The commented options
6033 show how this can be done.
6035 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6036 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6037 similarly-named options above.
6043 This transport is used for handling deliveries to pipes that are generated by
6044 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6045 option specifies that any output generated by the pipe is to be returned to the
6054 This transport is used for handling deliveries to files that are generated by
6055 redirection. The name of the file is not specified in this instance of
6056 &(appendfile)&, because it comes from the &(redirect)& router.
6061 This transport is used for handling automatic replies generated by users'
6066 .section "Default retry rule" "SECID57"
6067 .cindex "retry" "default rule"
6068 .cindex "default" "retry rule"
6069 The retry section of the configuration file contains rules which affect the way
6070 Exim retries deliveries that cannot be completed at the first attempt. It is
6071 introduced by the line
6075 In the default configuration, there is just one rule, which applies to all
6078 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6080 This causes any temporarily failing address to be retried every 15 minutes for
6081 2 hours, then at intervals starting at one hour and increasing by a factor of
6082 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6083 is not delivered after 4 days of temporary failure, it is bounced.
6085 If the retry section is removed from the configuration, or is empty (that is,
6086 if no retry rules are defined), Exim will not retry deliveries. This turns
6087 temporary errors into permanent errors.
6090 .section "Rewriting configuration" "SECID58"
6091 The rewriting section of the configuration, introduced by
6095 contains rules for rewriting addresses in messages as they arrive. There are no
6096 rewriting rules in the default configuration file.
6100 .section "Authenticators configuration" "SECTdefconfauth"
6101 .cindex "AUTH" "configuration"
6102 The authenticators section of the configuration, introduced by
6104 begin authenticators
6106 defines mechanisms for the use of the SMTP AUTH command. The default
6107 configuration file contains two commented-out example authenticators
6108 which support plaintext username/password authentication using the
6109 standard PLAIN mechanism and the traditional but non-standard LOGIN
6110 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6111 to support most MUA software.
6113 The example PLAIN authenticator looks like this:
6116 # driver = plaintext
6117 # server_set_id = $auth2
6118 # server_prompts = :
6119 # server_condition = Authentication is not yet configured
6120 # server_advertise_condition = ${if def:tls_in_cipher }
6122 And the example LOGIN authenticator looks like this:
6125 # driver = plaintext
6126 # server_set_id = $auth1
6127 # server_prompts = <| Username: | Password:
6128 # server_condition = Authentication is not yet configured
6129 # server_advertise_condition = ${if def:tls_in_cipher }
6132 The &%server_set_id%& option makes Exim remember the authenticated username
6133 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6134 &%server_prompts%& option configures the &(plaintext)& authenticator so
6135 that it implements the details of the specific authentication mechanism,
6136 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6137 when Exim offers authentication to clients; in the examples, this is only
6138 when TLS or SSL has been started, so to enable the authenticators you also
6139 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6141 The &%server_condition%& setting defines how to verify that the username and
6142 password are correct. In the examples it just produces an error message.
6143 To make the authenticators work, you can use a string expansion
6144 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6146 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6147 usercode and password are in different positions.
6148 Chapter &<<CHAPplaintext>>& covers both.
6150 .ecindex IIDconfiwal
6154 . ////////////////////////////////////////////////////////////////////////////
6155 . ////////////////////////////////////////////////////////////////////////////
6157 .chapter "Regular expressions" "CHAPregexp"
6159 .cindex "regular expressions" "library"
6161 Exim supports the use of regular expressions in many of its options. It
6162 uses the PCRE regular expression library; this provides regular expression
6163 matching that is compatible with Perl 5. The syntax and semantics of
6164 regular expressions is discussed in many Perl reference books, and also in
6165 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6166 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6168 The documentation for the syntax and semantics of the regular expressions that
6169 are supported by PCRE is included in the PCRE distribution, and no further
6170 description is included here. The PCRE functions are called from Exim using
6171 the default option settings (that is, with no PCRE options set), except that
6172 the PCRE_CASELESS option is set when the matching is required to be
6175 In most cases, when a regular expression is required in an Exim configuration,
6176 it has to start with a circumflex, in order to distinguish it from plain text
6177 or an &"ends with"& wildcard. In this example of a configuration setting, the
6178 second item in the colon-separated list is a regular expression.
6180 domains = a.b.c : ^\\d{3} : *.y.z : ...
6182 The doubling of the backslash is required because of string expansion that
6183 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6184 of this issue, and a way of avoiding the need for doubling backslashes. The
6185 regular expression that is eventually used in this example contains just one
6186 backslash. The circumflex is included in the regular expression, and has the
6187 normal effect of &"anchoring"& it to the start of the string that is being
6190 There are, however, two cases where a circumflex is not required for the
6191 recognition of a regular expression: these are the &%match%& condition in a
6192 string expansion, and the &%matches%& condition in an Exim filter file. In
6193 these cases, the relevant string is always treated as a regular expression; if
6194 it does not start with a circumflex, the expression is not anchored, and can
6195 match anywhere in the subject string.
6197 In all cases, if you want a regular expression to match at the end of a string,
6198 you must code the $ metacharacter to indicate this. For example:
6200 domains = ^\\d{3}\\.example
6202 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6205 domains = ^\\d{3}\\.example\$
6207 if you want &'example'& to be the top-level domain. The backslash before the
6208 $ is needed because string expansion also interprets dollar characters.
6212 . ////////////////////////////////////////////////////////////////////////////
6213 . ////////////////////////////////////////////////////////////////////////////
6215 .chapter "File and database lookups" "CHAPfdlookup"
6216 .scindex IIDfidalo1 "file" "lookups"
6217 .scindex IIDfidalo2 "database" "lookups"
6218 .cindex "lookup" "description of"
6219 Exim can be configured to look up data in files or databases as it processes
6220 messages. Two different kinds of syntax are used:
6223 A string that is to be expanded may contain explicit lookup requests. These
6224 cause parts of the string to be replaced by data that is obtained from the
6225 lookup. Lookups of this type are conditional expansion items. Different results
6226 can be defined for the cases of lookup success and failure. See chapter
6227 &<<CHAPexpand>>&, where string expansions are described in detail.
6229 Lists of domains, hosts, and email addresses can contain lookup requests as a
6230 way of avoiding excessively long linear lists. In this case, the data that is
6231 returned by the lookup is often (but not always) discarded; whether the lookup
6232 succeeds or fails is what really counts. These kinds of list are described in
6233 chapter &<<CHAPdomhosaddlists>>&.
6236 String expansions, lists, and lookups interact with each other in such a way
6237 that there is no order in which to describe any one of them that does not
6238 involve references to the others. Each of these three chapters makes more sense
6239 if you have read the other two first. If you are reading this for the first
6240 time, be aware that some of it will make a lot more sense after you have read
6241 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6243 .section "Examples of different lookup syntax" "SECID60"
6244 It is easy to confuse the two different kinds of lookup, especially as the
6245 lists that may contain the second kind are always expanded before being
6246 processed as lists. Therefore, they may also contain lookups of the first kind.
6247 Be careful to distinguish between the following two examples:
6249 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6250 domains = lsearch;/some/file
6252 The first uses a string expansion, the result of which must be a domain list.
6253 No strings have been specified for a successful or a failing lookup; the
6254 defaults in this case are the looked-up data and an empty string, respectively.
6255 The expansion takes place before the string is processed as a list, and the
6256 file that is searched could contain lines like this:
6258 192.168.3.4: domain1:domain2:...
6259 192.168.1.9: domain3:domain4:...
6261 When the lookup succeeds, the result of the expansion is a list of domains (and
6262 possibly other types of item that are allowed in domain lists).
6264 In the second example, the lookup is a single item in a domain list. It causes
6265 Exim to use a lookup to see if the domain that is being processed can be found
6266 in the file. The file could contains lines like this:
6271 Any data that follows the keys is not relevant when checking that the domain
6272 matches the list item.
6274 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6275 Consider a file containing lines like this:
6277 192.168.5.6: lsearch;/another/file
6279 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6280 first &%domains%& setting above generates the second setting, which therefore
6281 causes a second lookup to occur.
6283 The rest of this chapter describes the different lookup types that are
6284 available. Any of them can be used in any part of the configuration where a
6285 lookup is permitted.
6288 .section "Lookup types" "SECID61"
6289 .cindex "lookup" "types of"
6290 .cindex "single-key lookup" "definition of"
6291 Two different types of data lookup are implemented:
6294 The &'single-key'& type requires the specification of a file in which to look,
6295 and a single key to search for. The key must be a non-empty string for the
6296 lookup to succeed. The lookup type determines how the file is searched.
6298 .cindex "query-style lookup" "definition of"
6299 The &'query-style'& type accepts a generalized database query. No particular
6300 key value is assumed by Exim for query-style lookups. You can use whichever
6301 Exim variables you need to construct the database query.
6304 The code for each lookup type is in a separate source file that is included in
6305 the binary of Exim only if the corresponding compile-time option is set. The
6306 default settings in &_src/EDITME_& are:
6311 which means that only linear searching and DBM lookups are included by default.
6312 For some types of lookup (e.g. SQL databases), you need to install appropriate
6313 libraries and header files before building Exim.
6318 .section "Single-key lookup types" "SECTsinglekeylookups"
6319 .cindex "lookup" "single-key types"
6320 .cindex "single-key lookup" "list of types"
6321 The following single-key lookup types are implemented:
6324 .cindex "cdb" "description of"
6325 .cindex "lookup" "cdb"
6326 .cindex "binary zero" "in lookup key"
6327 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6328 string without a terminating binary zero. The cdb format is designed for
6329 indexed files that are read frequently and never updated, except by total
6330 re-creation. As such, it is particularly suitable for large files containing
6331 aliases or other indexed data referenced by an MTA. Information about cdb can
6332 be found in several places:
6334 &url(http://www.pobox.com/~djb/cdb.html)
6335 &url(ftp://ftp.corpit.ru/pub/tinycdb/)
6336 &url(http://packages.debian.org/stable/utils/freecdb.html)
6338 A cdb distribution is not needed in order to build Exim with cdb support,
6339 because the code for reading cdb files is included directly in Exim itself.
6340 However, no means of building or testing cdb files is provided with Exim, so
6341 you need to obtain a cdb distribution in order to do this.
6343 .cindex "DBM" "lookup type"
6344 .cindex "lookup" "dbm"
6345 .cindex "binary zero" "in lookup key"
6346 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6347 DBM file by looking up the record with the given key. A terminating binary
6348 zero is included in the key that is passed to the DBM library. See section
6349 &<<SECTdb>>& for a discussion of DBM libraries.
6351 .cindex "Berkeley DB library" "file format"
6352 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6353 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6354 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6355 the DB_UNKNOWN option. This enables it to handle any of the types of database
6356 that the library supports, and can be useful for accessing DBM files created by
6357 other applications. (For earlier DB versions, DB_HASH is always used.)
6359 .cindex "lookup" "dbmjz"
6360 .cindex "lookup" "dbm &-- embedded NULs"
6362 .cindex "dbmjz lookup type"
6363 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6364 interpreted as an Exim list; the elements of the list are joined together with
6365 ASCII NUL characters to form the lookup key. An example usage would be to
6366 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6367 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6368 &(cram_md5)& authenticator.
6370 .cindex "lookup" "dbmnz"
6371 .cindex "lookup" "dbm &-- terminating zero"
6372 .cindex "binary zero" "in lookup key"
6374 .cindex "&_/etc/userdbshadow.dat_&"
6375 .cindex "dbmnz lookup type"
6376 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6377 is not included in the key that is passed to the DBM library. You may need this
6378 if you want to look up data in files that are created by or shared with some
6379 other application that does not use terminating zeros. For example, you need to
6380 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6381 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6382 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6383 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6385 .cindex "lookup" "dsearch"
6386 .cindex "dsearch lookup type"
6387 &(dsearch)&: The given file must be a directory; this is searched for an entry
6388 whose name is the key by calling the &[lstat()]& function. The key may not
6389 contain any forward slash characters. If &[lstat()]& succeeds, the result of
6390 the lookup is the name of the entry, which may be a file, directory,
6391 symbolic link, or any other kind of directory entry. An example of how this
6392 lookup can be used to support virtual domains is given in section
6393 &<<SECTvirtualdomains>>&.
6395 .cindex "lookup" "iplsearch"
6396 .cindex "iplsearch lookup type"
6397 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6398 terminated by a colon or white space or the end of the line. The keys in the
6399 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6400 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6401 being interpreted as a key terminator. For example:
6403 1.2.3.4: data for 1.2.3.4
6404 192.168.0.0/16: data for 192.168.0.0/16
6405 "abcd::cdab": data for abcd::cdab
6406 "abcd:abcd::/32" data for abcd:abcd::/32
6408 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6409 file is searched linearly, using the CIDR masks where present, until a matching
6410 key is found. The first key that matches is used; there is no attempt to find a
6411 &"best"& match. Apart from the way the keys are matched, the processing for
6412 &(iplsearch)& is the same as for &(lsearch)&.
6414 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6415 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6416 lookup types support only literal keys.
6418 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6419 the implicit key is the host's IP address rather than its name (see section
6420 &<<SECThoslispatsikey>>&).
6422 .cindex "linear search"
6423 .cindex "lookup" "lsearch"
6424 .cindex "lsearch lookup type"
6425 .cindex "case sensitivity" "in lsearch lookup"
6426 &(lsearch)&: The given file is a text file that is searched linearly for a
6427 line beginning with the search key, terminated by a colon or white space or the
6428 end of the line. The search is case-insensitive; that is, upper and lower case
6429 letters are treated as the same. The first occurrence of the key that is found
6430 in the file is used.
6432 White space between the key and the colon is permitted. The remainder of the
6433 line, with leading and trailing white space removed, is the data. This can be
6434 continued onto subsequent lines by starting them with any amount of white
6435 space, but only a single space character is included in the data at such a
6436 junction. If the data begins with a colon, the key must be terminated by a
6441 Empty lines and lines beginning with # are ignored, even if they occur in the
6442 middle of an item. This is the traditional textual format of alias files. Note
6443 that the keys in an &(lsearch)& file are literal strings. There is no
6444 wildcarding of any kind.
6446 .cindex "lookup" "lsearch &-- colons in keys"
6447 .cindex "white space" "in lsearch key"
6448 In most &(lsearch)& files, keys are not required to contain colons or #
6449 characters, or white space. However, if you need this feature, it is available.
6450 If a key begins with a doublequote character, it is terminated only by a
6451 matching quote (or end of line), and the normal escaping rules apply to its
6452 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6453 quoted keys (exactly as for unquoted keys). There is no special handling of
6454 quotes for the data part of an &(lsearch)& line.
6457 .cindex "NIS lookup type"
6458 .cindex "lookup" "NIS"
6459 .cindex "binary zero" "in lookup key"
6460 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
6461 the given key, without a terminating binary zero. There is a variant called
6462 &(nis0)& which does include the terminating binary zero in the key. This is
6463 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6464 aliases; the full map names must be used.
6467 .cindex "wildlsearch lookup type"
6468 .cindex "lookup" "wildlsearch"
6469 .cindex "nwildlsearch lookup type"
6470 .cindex "lookup" "nwildlsearch"
6471 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6472 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6473 the file may be wildcarded. The difference between these two lookup types is
6474 that for &(wildlsearch)&, each key in the file is string-expanded before being
6475 used, whereas for &(nwildlsearch)&, no expansion takes place.
6477 .cindex "case sensitivity" "in (n)wildlsearch lookup"
6478 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
6479 file that are regular expressions can be made case-sensitive by the use of
6480 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
6482 . ==== As this is a nested list, any displays it contains must be indented
6483 . ==== as otherwise they are too far to the left.
6486 The string may begin with an asterisk to mean &"ends with"&. For example:
6488 *.a.b.c data for anything.a.b.c
6489 *fish data for anythingfish
6492 The string may begin with a circumflex to indicate a regular expression. For
6493 example, for &(wildlsearch)&:
6495 ^\N\d+\.a\.b\N data for <digits>.a.b
6497 Note the use of &`\N`& to disable expansion of the contents of the regular
6498 expression. If you are using &(nwildlsearch)&, where the keys are not
6499 string-expanded, the equivalent entry is:
6501 ^\d+\.a\.b data for <digits>.a.b
6503 The case-insensitive flag is set at the start of compiling the regular
6504 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
6505 For example, to make the entire pattern case-sensitive:
6507 ^(?-i)\d+\.a\.b data for <digits>.a.b
6510 If the regular expression contains white space or colon characters, you must
6511 either quote it (see &(lsearch)& above), or represent these characters in other
6512 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
6513 colon. This may be easier than quoting, because if you quote, you have to
6514 escape all the backslashes inside the quotes.
6516 &*Note*&: It is not possible to capture substrings in a regular expression
6517 match for later use, because the results of all lookups are cached. If a lookup
6518 is repeated, the result is taken from the cache, and no actual pattern matching
6519 takes place. The values of all the numeric variables are unset after a
6520 &((n)wildlsearch)& match.
6523 Although I cannot see it being of much use, the general matching function that
6524 is used to implement &((n)wildlsearch)& means that the string may begin with a
6525 lookup name terminated by a semicolon, and followed by lookup data. For
6528 cdb;/some/file data for keys that match the file
6530 The data that is obtained from the nested lookup is discarded.
6533 Keys that do not match any of these patterns are interpreted literally. The
6534 continuation rules for the data are the same as for &(lsearch)&, and keys may
6535 be followed by optional colons.
6537 &*Warning*&: Unlike most other single-key lookup types, a file of data for
6538 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
6539 lookup types support only literal keys.
6543 .section "Query-style lookup types" "SECID62"
6544 .cindex "lookup" "query-style types"
6545 .cindex "query-style lookup" "list of types"
6546 The supported query-style lookup types are listed below. Further details about
6547 many of them are given in later sections.
6550 .cindex "DNS" "as a lookup type"
6551 .cindex "lookup" "DNS"
6552 &(dnsdb)&: This does a DNS search for one or more records whose domain names
6553 are given in the supplied query. The resulting data is the contents of the
6554 records. See section &<<SECTdnsdb>>&.
6556 .cindex "InterBase lookup type"
6557 .cindex "lookup" "InterBase"
6558 &(ibase)&: This does a lookup in an InterBase database.
6560 .cindex "LDAP" "lookup type"
6561 .cindex "lookup" "LDAP"
6562 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
6563 returns attributes from a single entry. There is a variant called &(ldapm)&
6564 that permits values from multiple entries to be returned. A third variant
6565 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
6566 any attribute values. See section &<<SECTldap>>&.
6568 .cindex "MySQL" "lookup type"
6569 .cindex "lookup" "MySQL"
6570 &(mysql)&: The format of the query is an SQL statement that is passed to a
6571 MySQL database. See section &<<SECTsql>>&.
6573 .cindex "NIS+ lookup type"
6574 .cindex "lookup" "NIS+"
6575 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
6576 the field to be returned. See section &<<SECTnisplus>>&.
6578 .cindex "Oracle" "lookup type"
6579 .cindex "lookup" "Oracle"
6580 &(oracle)&: The format of the query is an SQL statement that is passed to an
6581 Oracle database. See section &<<SECTsql>>&.
6583 .cindex "lookup" "passwd"
6584 .cindex "passwd lookup type"
6585 .cindex "&_/etc/passwd_&"
6586 &(passwd)& is a query-style lookup with queries that are just user names. The
6587 lookup calls &[getpwnam()]& to interrogate the system password data, and on
6588 success, the result string is the same as you would get from an &(lsearch)&
6589 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
6590 password value. For example:
6592 *:42:42:King Rat:/home/kr:/bin/bash
6595 .cindex "PostgreSQL lookup type"
6596 .cindex "lookup" "PostgreSQL"
6597 &(pgsql)&: The format of the query is an SQL statement that is passed to a
6598 PostgreSQL database. See section &<<SECTsql>>&.
6601 .cindex "sqlite lookup type"
6602 .cindex "lookup" "sqlite"
6603 &(sqlite)&: The format of the query is a file name followed by an SQL statement
6604 that is passed to an SQLite database. See section &<<SECTsqlite>>&.
6607 &(testdb)&: This is a lookup type that is used for testing Exim. It is
6608 not likely to be useful in normal operation.
6610 .cindex "whoson lookup type"
6611 .cindex "lookup" "whoson"
6612 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
6613 allows a server to check whether a particular (dynamically allocated) IP
6614 address is currently allocated to a known (trusted) user and, optionally, to
6615 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
6616 at one time for &"POP before SMTP"& authentication, but that approach has been
6617 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
6618 &"POP before SMTP"& checking using ACL statements such as
6620 require condition = \
6621 ${lookup whoson {$sender_host_address}{yes}{no}}
6623 The query consists of a single IP address. The value returned is the name of
6624 the authenticated user, which is stored in the variable &$value$&. However, in
6625 this example, the data in &$value$& is not used; the result of the lookup is
6626 one of the fixed strings &"yes"& or &"no"&.
6631 .section "Temporary errors in lookups" "SECID63"
6632 .cindex "lookup" "temporary error in"
6633 Lookup functions can return temporary error codes if the lookup cannot be
6634 completed. For example, an SQL or LDAP database might be unavailable. For this
6635 reason, it is not advisable to use a lookup that might do this for critical
6636 options such as a list of local domains.
6638 When a lookup cannot be completed in a router or transport, delivery
6639 of the message (to the relevant address) is deferred, as for any other
6640 temporary error. In other circumstances Exim may assume the lookup has failed,
6641 or may give up altogether.
6645 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
6646 .cindex "wildcard lookups"
6647 .cindex "lookup" "default values"
6648 .cindex "lookup" "wildcard"
6649 .cindex "lookup" "* added to type"
6650 .cindex "default" "in single-key lookups"
6651 In this context, a &"default value"& is a value specified by the administrator
6652 that is to be used if a lookup fails.
6654 &*Note:*& This section applies only to single-key lookups. For query-style
6655 lookups, the facilities of the query language must be used. An attempt to
6656 specify a default for a query-style lookup provokes an error.
6658 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
6659 and the initial lookup fails, the key &"*"& is looked up in the file to
6660 provide a default value. See also the section on partial matching below.
6662 .cindex "*@ with single-key lookup"
6663 .cindex "lookup" "*@ added to type"
6664 .cindex "alias file" "per-domain default"
6665 Alternatively, if &"*@"& is added to a single-key lookup type (for example
6666 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
6667 character, a second lookup is done with everything before the last @ replaced
6668 by *. This makes it possible to provide per-domain defaults in alias files
6669 that include the domains in the keys. If the second lookup fails (or doesn't
6670 take place because there is no @ in the key), &"*"& is looked up.
6671 For example, a &(redirect)& router might contain:
6673 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
6675 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
6676 looks up these keys, in this order:
6682 The data is taken from whichever key it finds first. &*Note*&: In an
6683 &(lsearch)& file, this does not mean the first of these keys in the file. A
6684 complete scan is done for each key, and only if it is not found at all does
6685 Exim move on to try the next key.
6689 .section "Partial matching in single-key lookups" "SECTpartiallookup"
6690 .cindex "partial matching"
6691 .cindex "wildcard lookups"
6692 .cindex "lookup" "partial matching"
6693 .cindex "lookup" "wildcard"
6694 .cindex "asterisk" "in search type"
6695 The normal operation of a single-key lookup is to search the file for an exact
6696 match with the given key. However, in a number of situations where domains are
6697 being looked up, it is useful to be able to do partial matching. In this case,
6698 information in the file that has a key starting with &"*."& is matched by any
6699 domain that ends with the components that follow the full stop. For example, if
6700 a key in a DBM file is
6702 *.dates.fict.example
6704 then when partial matching is enabled this is matched by (amongst others)
6705 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
6706 by &'dates.fict.example'&, if that does not appear as a separate key in the
6709 &*Note*&: Partial matching is not available for query-style lookups. It is
6710 also not available for any lookup items in address lists (see section
6711 &<<SECTaddresslist>>&).
6713 Partial matching is implemented by doing a series of separate lookups using
6714 keys constructed by modifying the original subject key. This means that it can
6715 be used with any of the single-key lookup types, provided that
6716 partial matching keys
6717 beginning with a special prefix (default &"*."&) are included in the data file.
6718 Keys in the file that do not begin with the prefix are matched only by
6719 unmodified subject keys when partial matching is in use.
6721 Partial matching is requested by adding the string &"partial-"& to the front of
6722 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
6723 is done, the subject key is first looked up unmodified; if that fails, &"*."&
6724 is added at the start of the subject key, and it is looked up again. If that
6725 fails, further lookups are tried with dot-separated components removed from the
6726 start of the subject key, one-by-one, and &"*."& added on the front of what
6729 A minimum number of two non-* components are required. This can be adjusted
6730 by including a number before the hyphen in the search type. For example,
6731 &%partial3-lsearch%& specifies a minimum of three non-* components in the
6732 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
6733 subject key is &'2250.dates.fict.example'& then the following keys are looked
6734 up when the minimum number of non-* components is two:
6736 2250.dates.fict.example
6737 *.2250.dates.fict.example
6738 *.dates.fict.example
6741 As soon as one key in the sequence is successfully looked up, the lookup
6744 .cindex "lookup" "partial matching &-- changing prefix"
6745 .cindex "prefix" "for partial matching"
6746 The use of &"*."& as the partial matching prefix is a default that can be
6747 changed. The motivation for this feature is to allow Exim to operate with file
6748 formats that are used by other MTAs. A different prefix can be supplied in
6749 parentheses instead of the hyphen after &"partial"&. For example:
6751 domains = partial(.)lsearch;/some/file
6753 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
6754 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
6755 components is unchanged). The prefix may consist of any punctuation characters
6756 other than a closing parenthesis. It may be empty, for example:
6758 domains = partial1()cdb;/some/file
6760 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
6761 &`a.b.c`&, &`b.c`&, and &`c`&.
6763 If &"partial0"& is specified, what happens at the end (when the lookup with
6764 just one non-wild component has failed, and the original key is shortened right
6765 down to the null string) depends on the prefix:
6768 If the prefix has zero length, the whole lookup fails.
6770 If the prefix has length 1, a lookup for just the prefix is done. For
6771 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
6773 Otherwise, if the prefix ends in a dot, the dot is removed, and the
6774 remainder is looked up. With the default prefix, therefore, the final lookup is
6775 for &"*"& on its own.
6777 Otherwise, the whole prefix is looked up.
6781 If the search type ends in &"*"& or &"*@"& (see section
6782 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
6783 this implies happens after all partial lookups have failed. If &"partial0"& is
6784 specified, adding &"*"& to the search type has no effect with the default
6785 prefix, because the &"*"& key is already included in the sequence of partial
6786 lookups. However, there might be a use for lookup types such as
6787 &"partial0(.)lsearch*"&.
6789 The use of &"*"& in lookup partial matching differs from its use as a wildcard
6790 in domain lists and the like. Partial matching works only in terms of
6791 dot-separated components; a key such as &`*fict.example`&
6792 in a database file is useless, because the asterisk in a partial matching
6793 subject key is always followed by a dot.
6798 .section "Lookup caching" "SECID64"
6799 .cindex "lookup" "caching"
6800 .cindex "caching" "lookup data"
6801 Exim caches all lookup results in order to avoid needless repetition of
6802 lookups. However, because (apart from the daemon) Exim operates as a collection
6803 of independent, short-lived processes, this caching applies only within a
6804 single Exim process. There is no inter-process lookup caching facility.
6806 For single-key lookups, Exim keeps the relevant files open in case there is
6807 another lookup that needs them. In some types of configuration this can lead to
6808 many files being kept open for messages with many recipients. To avoid hitting
6809 the operating system limit on the number of simultaneously open files, Exim
6810 closes the least recently used file when it needs to open more files than its
6811 own internal limit, which can be changed via the &%lookup_open_max%& option.
6813 The single-key lookup files are closed and the lookup caches are flushed at
6814 strategic points during delivery &-- for example, after all routing is
6820 .section "Quoting lookup data" "SECID65"
6821 .cindex "lookup" "quoting"
6822 .cindex "quoting" "in lookups"
6823 When data from an incoming message is included in a query-style lookup, there
6824 is the possibility of special characters in the data messing up the syntax of
6825 the query. For example, a NIS+ query that contains
6829 will be broken if the local part happens to contain a closing square bracket.
6830 For NIS+, data can be enclosed in double quotes like this:
6832 [name="$local_part"]
6834 but this still leaves the problem of a double quote in the data. The rule for
6835 NIS+ is that double quotes must be doubled. Other lookup types have different
6836 rules, and to cope with the differing requirements, an expansion operator
6837 of the following form is provided:
6839 ${quote_<lookup-type>:<string>}
6841 For example, the safest way to write the NIS+ query is
6843 [name="${quote_nisplus:$local_part}"]
6845 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
6846 operator can be used for all lookup types, but has no effect for single-key
6847 lookups, since no quoting is ever needed in their key strings.
6852 .section "More about dnsdb" "SECTdnsdb"
6853 .cindex "dnsdb lookup"
6854 .cindex "lookup" "dnsdb"
6855 .cindex "DNS" "as a lookup type"
6856 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
6857 of a record type and a domain name, separated by an equals sign. For example,
6858 an expansion string could contain:
6860 ${lookup dnsdb{mx=a.b.example}{$value}fail}
6862 If the lookup succeeds, the result is placed in &$value$&, which in this case
6863 is used on its own as the result. If the lookup does not succeed, the
6864 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
6865 &<<SECTforexpfai>>& for an explanation of what this means.
6867 The supported DNS record types are A, CNAME, MX, NS, PTR, SPF, SRV, TLSA and TXT,
6868 and, when Exim is compiled with IPv6 support, AAAA (and A6 if that is also
6869 configured). If no type is given, TXT is assumed. When the type is PTR,
6870 the data can be an IP address, written as normal; inversion and the addition of
6871 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
6873 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
6875 If the data for a PTR record is not a syntactically valid IP address, it is not
6876 altered and nothing is added.
6878 For any record type, if multiple records are found (or, for A6 lookups, if a
6879 single record leads to multiple addresses), the data is returned as a
6880 concatenation, with newline as the default separator. The order, of course,
6881 depends on the DNS resolver. You can specify a different separator character
6882 between multiple records by putting a right angle-bracket followed immediately
6883 by the new separator at the start of the query. For example:
6885 ${lookup dnsdb{>: a=host1.example}}
6887 It is permitted to specify a space as the separator character. Further
6888 white space is ignored.
6890 .cindex "MX record" "in &(dnsdb)& lookup"
6891 .cindex "SRV record" "in &(dnsdb)& lookup"
6892 For an MX lookup, both the preference value and the host name are returned for
6893 each record, separated by a space. For an SRV lookup, the priority, weight,
6894 port, and host name are returned for each record, separated by spaces.
6896 An alternate field separator can be specified using a comma after the main
6897 separator character, followed immediately by the field separator.
6900 .cindex "TXT record" "in &(dnsdb)& lookup"
6901 .cindex "SPF record" "in &(dnsdb)& lookup"
6902 For TXT records with multiple items of data, only the first item is returned,
6903 unless a separator for them is specified using a comma after the separator
6904 character followed immediately by the TXT record item separator. To concatenate
6905 items without a separator, use a semicolon instead. For SPF records the
6906 default behaviour is to concatenate multiple items without using a separator.
6908 ${lookup dnsdb{>\n,: txt=a.b.example}}
6909 ${lookup dnsdb{>\n; txt=a.b.example}}
6910 ${lookup dnsdb{spf=example.org}}
6912 It is permitted to specify a space as the separator character. Further
6913 white space is ignored.
6915 .section "Pseudo dnsdb record types" "SECID66"
6916 .cindex "MX record" "in &(dnsdb)& lookup"
6917 By default, both the preference value and the host name are returned for
6918 each MX record, separated by a space. If you want only host names, you can use
6919 the pseudo-type MXH:
6921 ${lookup dnsdb{mxh=a.b.example}}
6923 In this case, the preference values are omitted, and just the host names are
6926 .cindex "name server for enclosing domain"
6927 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
6928 records on the given domain, but if none are found, it removes the first
6929 component of the domain name, and tries again. This process continues until NS
6930 records are found or there are no more components left (or there is a DNS
6931 error). In other words, it may return the name servers for a top-level domain,
6932 but it never returns the root name servers. If there are no NS records for the
6933 top-level domain, the lookup fails. Consider these examples:
6935 ${lookup dnsdb{zns=xxx.quercite.com}}
6936 ${lookup dnsdb{zns=xxx.edu}}
6938 Assuming that in each case there are no NS records for the full domain name,
6939 the first returns the name servers for &%quercite.com%&, and the second returns
6940 the name servers for &%edu%&.
6942 You should be careful about how you use this lookup because, unless the
6943 top-level domain does not exist, the lookup always returns some host names. The
6944 sort of use to which this might be put is for seeing if the name servers for a
6945 given domain are on a blacklist. You can probably assume that the name servers
6946 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
6949 .cindex "CSA" "in &(dnsdb)& lookup"
6950 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
6951 records according to the CSA rules, which are described in section
6952 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
6953 not sufficient because of the extra parent domain search behaviour of CSA. The
6954 result of a successful lookup such as:
6956 ${lookup dnsdb {csa=$sender_helo_name}}
6958 has two space-separated fields: an authorization code and a target host name.
6959 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
6960 authorization required but absent, or &"?"& for unknown.
6962 .cindex "A+" "in &(dnsdb)& lookup"
6963 The pseudo-type A+ performs an A6 lookup (if configured) followed by an AAAA
6964 and then an A lookup. All results are returned; defer processing
6965 (see below) is handled separately for each lookup. Example:
6967 ${lookup dnsdb {>; a+=$sender_helo_name}}
6971 .section "Multiple dnsdb lookups" "SECID67"
6972 In the previous sections, &(dnsdb)& lookups for a single domain are described.
6973 However, you can specify a list of domains or IP addresses in a single
6974 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
6975 the default separator, but with the ability to change this. For example:
6977 ${lookup dnsdb{one.domain.com:two.domain.com}}
6978 ${lookup dnsdb{a=one.host.com:two.host.com}}
6979 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
6981 In order to retain backwards compatibility, there is one special case: if
6982 the lookup type is PTR and no change of separator is specified, Exim looks
6983 to see if the rest of the string is precisely one IPv6 address. In this
6984 case, it does not treat it as a list.
6986 The data from each lookup is concatenated, with newline separators by default,
6987 in the same way that multiple DNS records for a single item are handled. A
6988 different separator can be specified, as described above.
6990 Modifiers for &(dnsdb)& lookups are givien by optional keywords,
6991 each followed by a comma,
6992 that may appear before the record type.
6994 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
6995 temporary DNS error for any of them, the behaviour is controlled by
6996 a defer-option modifier.
6997 The possible keywords are
6998 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
6999 With &"strict"& behaviour, any temporary DNS error causes the
7000 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
7001 ignored, and the behaviour is as if the DNS lookup failed to find anything.
7002 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
7003 error causes the whole lookup to defer only if none of the other lookups
7004 succeed. The default is &"lax"&, so the following lookups are equivalent:
7006 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
7007 ${lookup dnsdb{a=one.host.com:two.host.com}}
7009 Thus, in the default case, as long as at least one of the DNS lookups
7010 yields some data, the lookup succeeds.
7012 .cindex "DNSSEC" "dns lookup"
7013 Use of &(DNSSEC)& is controlled by a dnssec modifier.
7014 The possible keywords are
7015 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
7016 With &"strict"& or &"lax"& DNSSEC information is requested
7018 With &"strict"& a response from the DNS resolver that
7019 is not labelled as authenticated data
7020 is treated as equivalent to a temporary DNS error.
7021 The default is &"never"&.
7023 See also the &$lookup_dnssec_authenticated$& variable.
7028 .section "More about LDAP" "SECTldap"
7029 .cindex "LDAP" "lookup, more about"
7030 .cindex "lookup" "LDAP"
7031 .cindex "Solaris" "LDAP"
7032 The original LDAP implementation came from the University of Michigan; this has
7033 become &"Open LDAP"&, and there are now two different releases. Another
7034 implementation comes from Netscape, and Solaris 7 and subsequent releases
7035 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7036 the lookup function level, their error handling is different. For this reason
7037 it is necessary to set a compile-time variable when building Exim with LDAP, to
7038 indicate which LDAP library is in use. One of the following should appear in
7039 your &_Local/Makefile_&:
7041 LDAP_LIB_TYPE=UMICHIGAN
7042 LDAP_LIB_TYPE=OPENLDAP1
7043 LDAP_LIB_TYPE=OPENLDAP2
7044 LDAP_LIB_TYPE=NETSCAPE
7045 LDAP_LIB_TYPE=SOLARIS
7047 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7048 same interface as the University of Michigan version.
7050 There are three LDAP lookup types in Exim. These behave slightly differently in
7051 the way they handle the results of a query:
7054 &(ldap)& requires the result to contain just one entry; if there are more, it
7057 &(ldapdn)& also requires the result to contain just one entry, but it is the
7058 Distinguished Name that is returned rather than any attribute values.
7060 &(ldapm)& permits the result to contain more than one entry; the attributes
7061 from all of them are returned.
7065 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7066 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7067 the data returned by a successful lookup is described in the next section.
7068 First we explain how LDAP queries are coded.
7071 .section "Format of LDAP queries" "SECTforldaque"
7072 .cindex "LDAP" "query format"
7073 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7074 the configuration of a &(redirect)& router one might have this setting:
7076 data = ${lookup ldap \
7077 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7078 c=UK?mailbox?base?}}
7080 .cindex "LDAP" "with TLS"
7081 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7082 secure (encrypted) LDAP connections. The second of these ensures that an
7083 encrypted TLS connection is used.
7085 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7086 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7087 See the &%ldap_start_tls%& option.
7089 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7090 controlled. Every part of the TLS configuration can be configured by settings in
7091 &_exim.conf_&. Depending on the version of the client libraries installed on
7092 your system, some of the initialization may have required setting options in
7093 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7094 certificates. This revealed a nuance where the current UID that exim was
7095 running as could affect which config files it read. With Exim 4.83, these
7096 methods become optional, only taking effect if not specifically set in
7100 .section "LDAP quoting" "SECID68"
7101 .cindex "LDAP" "quoting"
7102 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7103 and the second because the LDAP query is represented as a URL. Furthermore,
7104 within an LDAP query, two different kinds of quoting are required. For this
7105 reason, there are two different LDAP-specific quoting operators.
7107 The &%quote_ldap%& operator is designed for use on strings that are part of
7108 filter specifications. Conceptually, it first does the following conversions on
7116 in accordance with RFC 2254. The resulting string is then quoted according
7117 to the rules for URLs, that is, all non-alphanumeric characters except
7121 are converted to their hex values, preceded by a percent sign. For example:
7123 ${quote_ldap: a(bc)*, a<yz>; }
7127 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7129 Removing the URL quoting, this is (with a leading and a trailing space):
7131 a\28bc\29\2A, a<yz>;
7133 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7134 base DN specifications in queries. Conceptually, it first converts the string
7135 by inserting a backslash in front of any of the following characters:
7139 It also inserts a backslash before any leading spaces or # characters, and
7140 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7141 is then quoted according to the rules for URLs. For example:
7143 ${quote_ldap_dn: a(bc)*, a<yz>; }
7147 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7149 Removing the URL quoting, this is (with a trailing space):
7151 \ a(bc)*\, a\<yz\>\;\
7153 There are some further comments about quoting in the section on LDAP
7154 authentication below.
7157 .section "LDAP connections" "SECID69"
7158 .cindex "LDAP" "connections"
7159 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7160 is in use, via a Unix domain socket. The example given above does not specify
7161 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7164 ldap://<hostname>:<port>/...
7166 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7167 used. When no server is specified in a query, a list of default servers is
7168 taken from the &%ldap_default_servers%& configuration option. This supplies a
7169 colon-separated list of servers which are tried in turn until one successfully
7170 handles a query, or there is a serious error. Successful handling either
7171 returns the requested data, or indicates that it does not exist. Serious errors
7172 are syntactical, or multiple values when only a single value is expected.
7173 Errors which cause the next server to be tried are connection failures, bind
7174 failures, and timeouts.
7176 For each server name in the list, a port number can be given. The standard way
7177 of specifying a host and port is to use a colon separator (RFC 1738). Because
7178 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7179 doubled. For example
7181 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7183 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7184 to the LDAP library with no server name, and the library's default (normally
7185 the local host) is used.
7187 If you are using the OpenLDAP library, you can connect to an LDAP server using
7188 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7189 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7190 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7193 For this type of connection, instead of a host name for the server, a pathname
7194 for the socket is required, and the port number is not relevant. The pathname
7195 can be specified either as an item in &%ldap_default_servers%&, or inline in
7196 the query. In the former case, you can have settings such as
7198 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7200 When the pathname is given in the query, you have to escape the slashes as
7201 &`%2F`& to fit in with the LDAP URL syntax. For example:
7203 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7205 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7206 a pathname, it uses the Unix domain socket code, even if the query actually
7207 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7208 socket connection. This behaviour means that you can use a setting of
7209 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7210 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7211 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7214 If an explicit &`ldapi`& type is given in a query when a host name is
7215 specified, an error is diagnosed. However, if there are more items in
7216 &%ldap_default_servers%&, they are tried. In other words:
7219 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7222 Using &`ldapi`& with a host name causes an error.
7226 Using &`ldapi`& with no host or path in the query, and no setting of
7227 &%ldap_default_servers%&, does whatever the library does by default.
7231 .section "LDAP authentication and control information" "SECID70"
7232 .cindex "LDAP" "authentication"
7233 The LDAP URL syntax provides no way of passing authentication and other control
7234 information to the server. To make this possible, the URL in an LDAP query may
7235 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7236 spaces. If a value contains spaces it must be enclosed in double quotes, and
7237 when double quotes are used, backslash is interpreted in the usual way inside
7238 them. The following names are recognized:
7240 &`DEREFERENCE`& set the dereferencing parameter
7241 &`NETTIME `& set a timeout for a network operation
7242 &`USER `& set the DN, for authenticating the LDAP bind
7243 &`PASS `& set the password, likewise
7244 &`REFERRALS `& set the referrals parameter
7245 &`SERVERS `& set alternate server list for this query only
7246 &`SIZE `& set the limit for the number of entries returned
7247 &`TIME `& set the maximum waiting time for a query
7249 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7250 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7251 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7252 library from trying to follow referrals issued by the LDAP server.
7254 The name CONNECT is an obsolete name for NETTIME, retained for
7255 backwards compatibility. This timeout (specified as a number of seconds) is
7256 enforced from the client end for operations that can be carried out over a
7257 network. Specifically, it applies to network connections and calls to the
7258 &'ldap_result()'& function. If the value is greater than zero, it is used if
7259 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7260 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7261 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7262 Netscape SDK; for OpenLDAP no action is taken.
7264 The TIME parameter (also a number of seconds) is passed to the server to
7265 set a server-side limit on the time taken to complete a search.
7267 The SERVERS parameter allows you to specify an alternate list of ldap servers
7268 to use for an individual lookup. The global ldap_servers option provides a
7269 default list of ldap servers, and a single lookup can specify a single ldap
7270 server to use. But when you need to do a lookup with a list of servers that is
7271 different than the default list (maybe different order, maybe a completely
7272 different set of servers), the SERVERS parameter allows you to specify this
7273 alternate list (colon-separated).
7275 Here is an example of an LDAP query in an Exim lookup that uses some of these
7276 values. This is a single line, folded to fit on the page:
7279 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7280 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7283 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7284 any of the auxiliary data. Exim configuration settings that include lookups
7285 which contain password information should be preceded by &"hide"& to prevent
7286 non-admin users from using the &%-bP%& option to see their values.
7288 The auxiliary data items may be given in any order. The default is no
7289 connection timeout (the system timeout is used), no user or password, no limit
7290 on the number of entries returned, and no time limit on queries.
7292 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7293 removes any URL quoting that it may contain before passing it LDAP. Apparently
7294 some libraries do this for themselves, but some do not. Removing the URL
7295 quoting has two advantages:
7298 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7299 DNs as with DNs inside actual queries.
7301 It permits spaces inside USER= DNs.
7304 For example, a setting such as
7306 USER=cn=${quote_ldap_dn:$1}
7308 should work even if &$1$& contains spaces.
7310 Expanded data for the PASS= value should be quoted using the &%quote%&
7311 expansion operator, rather than the LDAP quote operators. The only reason this
7312 field needs quoting is to ensure that it conforms to the Exim syntax, which
7313 does not allow unquoted spaces. For example:
7317 The LDAP authentication mechanism can be used to check passwords as part of
7318 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7323 .section "Format of data returned by LDAP" "SECID71"
7324 .cindex "LDAP" "returned data formats"
7325 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7326 as a sequence of values, for example
7328 cn=manager, o=University of Cambridge, c=UK
7330 The &(ldap)& lookup type generates an error if more than one entry matches the
7331 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7332 the result between the data from different entries. It is possible for multiple
7333 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7334 you know that whatever values are returned all came from a single entry in the
7337 In the common case where you specify a single attribute in your LDAP query, the
7338 result is not quoted, and does not contain the attribute name. If the attribute
7339 has multiple values, they are separated by commas.
7341 If you specify multiple attributes, the result contains space-separated, quoted
7342 strings, each preceded by the attribute name and an equals sign. Within the
7343 quotes, the quote character, backslash, and newline are escaped with
7344 backslashes, and commas are used to separate multiple values for the attribute.
7346 Any commas in attribute values are doubled
7347 (permitting treatment of the values as a comma-separated list).
7349 Apart from the escaping, the string within quotes takes the same form as the
7350 output when a single attribute is requested. Specifying no attributes is the
7351 same as specifying all of an entry's attributes.
7354 Here are some examples of the output format. The first line of each pair is an
7355 LDAP query, and the second is the data that is returned. The attribute called
7356 &%attr1%& has two values, one of them with an embedded comma, whereas
7357 &%attr2%& has only one value:
7359 ldap:///o=base?attr1?sub?(uid=fred)
7362 ldap:///o=base?attr2?sub?(uid=fred)
7365 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7366 attr1="value1.1,value1,,2" attr2="value two"
7368 ldap:///o=base??sub?(uid=fred)
7369 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
7373 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7374 results of LDAP lookups.
7375 The &%extract%& operator in string expansions can be used to pick out
7376 individual fields from data that consists of &'key'&=&'value'& pairs.
7378 The &%listextract%& operator should be used to pick out individual values
7379 of attributes, even when only a single value is expected.
7380 The doubling of embedded commas allows you to use the returned data as a
7381 comma separated list (using the "<," syntax for changing the input list separator).
7387 .section "More about NIS+" "SECTnisplus"
7388 .cindex "NIS+ lookup type"
7389 .cindex "lookup" "NIS+"
7390 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7391 and field name. If this is given, the result of a successful query is the
7392 contents of the named field; otherwise the result consists of a concatenation
7393 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
7394 values containing spaces are quoted. For example, the query
7396 [name=mg1456],passwd.org_dir
7398 might return the string
7400 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
7401 home=/home/mg1456 shell=/bin/bash shadow=""
7403 (split over two lines here to fit on the page), whereas
7405 [name=mg1456],passwd.org_dir:gcos
7411 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
7412 for the given indexed key. The effect of the &%quote_nisplus%& expansion
7413 operator is to double any quote characters within the text.
7417 .section "SQL lookups" "SECTsql"
7418 .cindex "SQL lookup types"
7419 .cindex "MySQL" "lookup type"
7420 .cindex "PostgreSQL lookup type"
7421 .cindex "lookup" "MySQL"
7422 .cindex "lookup" "PostgreSQL"
7423 .cindex "Oracle" "lookup type"
7424 .cindex "lookup" "Oracle"
7425 .cindex "InterBase lookup type"
7426 .cindex "lookup" "InterBase"
7427 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, and SQLite
7428 databases. Queries for these databases contain SQL statements, so an example
7431 ${lookup mysql{select mailbox from users where id='userx'}\
7434 If the result of the query contains more than one field, the data for each
7435 field in the row is returned, preceded by its name, so the result of
7437 ${lookup pgsql{select home,name from users where id='userx'}\
7442 home=/home/userx name="Mister X"
7444 Empty values and values containing spaces are double quoted, with embedded
7445 quotes escaped by a backslash. If the result of the query contains just one
7446 field, the value is passed back verbatim, without a field name, for example:
7450 If the result of the query yields more than one row, it is all concatenated,
7451 with a newline between the data for each row.
7454 .section "More about MySQL, PostgreSQL, Oracle, and InterBase" "SECID72"
7455 .cindex "MySQL" "lookup type"
7456 .cindex "PostgreSQL lookup type"
7457 .cindex "lookup" "MySQL"
7458 .cindex "lookup" "PostgreSQL"
7459 .cindex "Oracle" "lookup type"
7460 .cindex "lookup" "Oracle"
7461 .cindex "InterBase lookup type"
7462 .cindex "lookup" "InterBase"
7463 If any MySQL, PostgreSQL, Oracle, or InterBase lookups are used, the
7464 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, or &%ibase_servers%&
7465 option (as appropriate) must be set to a colon-separated list of server
7467 (For MySQL and PostgreSQL only, the global option need not be set if all
7468 queries contain their own server information &-- see section
7469 &<<SECTspeserque>>&.) Each item in the list is a slash-separated list of four
7470 items: host name, database name, user name, and password. In the case of
7471 Oracle, the host name field is used for the &"service name"&, and the database
7472 name field is not used and should be empty. For example:
7474 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
7476 Because password data is sensitive, you should always precede the setting with
7477 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
7478 option. Here is an example where two MySQL servers are listed:
7480 hide mysql_servers = localhost/users/root/secret:\
7481 otherhost/users/root/othersecret
7483 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
7484 because this is a colon-separated list, the colon has to be doubled. For each
7485 query, these parameter groups are tried in order until a connection is made and
7486 a query is successfully processed. The result of a query may be that no data is
7487 found, but that is still a successful query. In other words, the list of
7488 servers provides a backup facility, not a list of different places to look.
7490 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
7491 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
7492 respectively, and the characters single-quote, double-quote, and backslash
7493 itself are escaped with backslashes. The &%quote_pgsql%& expansion operator, in
7494 addition, escapes the percent and underscore characters. This cannot be done
7495 for MySQL because these escapes are not recognized in contexts where these
7496 characters are not special.
7498 .section "Specifying the server in the query" "SECTspeserque"
7499 For MySQL and PostgreSQL lookups (but not currently for Oracle and InterBase),
7500 it is possible to specify a list of servers with an individual query. This is
7501 done by starting the query with
7503 &`servers=`&&'server1:server2:server3:...'&&`;`&
7505 Each item in the list may take one of two forms:
7507 If it contains no slashes it is assumed to be just a host name. The appropriate
7508 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
7509 of the same name, and the remaining parameters (database, user, password) are
7512 If it contains any slashes, it is taken as a complete parameter set.
7514 The list of servers is used in exactly the same way as the global list.
7515 Once a connection to a server has happened and a query has been
7516 successfully executed, processing of the lookup ceases.
7518 This feature is intended for use in master/slave situations where updates
7519 are occurring and you want to update the master rather than a slave. If the
7520 master is in the list as a backup for reading, you might have a global setting
7523 mysql_servers = slave1/db/name/pw:\
7527 In an updating lookup, you could then write:
7529 ${lookup mysql{servers=master; UPDATE ...} }
7531 That query would then be sent only to the master server. If, on the other hand,
7532 the master is not to be used for reading, and so is not present in the global
7533 option, you can still update it by a query of this form:
7535 ${lookup pgsql{servers=master/db/name/pw; UPDATE ...} }
7539 .section "Special MySQL features" "SECID73"
7540 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
7541 causes a connection to the server on the local host by means of a Unix domain
7542 socket. An alternate socket can be specified in parentheses. The full syntax of
7543 each item in &%mysql_servers%& is:
7545 <&'hostname'&>::<&'port'&>(<&'socket name'&>)/<&'database'&>/&&&
7546 <&'user'&>/<&'password'&>
7548 Any of the three sub-parts of the first field can be omitted. For normal use on
7549 the local host it can be left blank or set to just &"localhost"&.
7551 No database need be supplied &-- but if it is absent here, it must be given in
7554 If a MySQL query is issued that does not request any data (an insert, update,
7555 or delete command), the result of the lookup is the number of rows affected.
7557 &*Warning*&: This can be misleading. If an update does not actually change
7558 anything (for example, setting a field to the value it already has), the result
7559 is zero because no rows are affected.
7562 .section "Special PostgreSQL features" "SECID74"
7563 PostgreSQL lookups can also use Unix domain socket connections to the database.
7564 This is usually faster and costs less CPU time than a TCP/IP connection.
7565 However it can be used only if the mail server runs on the same machine as the
7566 database server. A configuration line for PostgreSQL via Unix domain sockets
7569 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
7571 In other words, instead of supplying a host name, a path to the socket is
7572 given. The path name is enclosed in parentheses so that its slashes aren't
7573 visually confused with the delimiters for the other server parameters.
7575 If a PostgreSQL query is issued that does not request any data (an insert,
7576 update, or delete command), the result of the lookup is the number of rows
7579 .section "More about SQLite" "SECTsqlite"
7580 .cindex "lookup" "SQLite"
7581 .cindex "sqlite lookup type"
7582 SQLite is different to the other SQL lookups because a file name is required in
7583 addition to the SQL query. An SQLite database is a single file, and there is no
7584 daemon as in the other SQL databases. The interface to Exim requires the name
7585 of the file, as an absolute path, to be given at the start of the query. It is
7586 separated from the query by white space. This means that the path name cannot
7587 contain white space. Here is a lookup expansion example:
7589 ${lookup sqlite {/some/thing/sqlitedb \
7590 select name from aliases where id='userx';}}
7592 In a list, the syntax is similar. For example:
7594 domainlist relay_to_domains = sqlite;/some/thing/sqlitedb \
7595 select * from relays where ip='$sender_host_address';
7597 The only character affected by the &%quote_sqlite%& operator is a single
7598 quote, which it doubles.
7600 The SQLite library handles multiple simultaneous accesses to the database
7601 internally. Multiple readers are permitted, but only one process can
7602 update at once. Attempts to access the database while it is being updated
7603 are rejected after a timeout period, during which the SQLite library
7604 waits for the lock to be released. In Exim, the default timeout is set
7605 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
7611 . ////////////////////////////////////////////////////////////////////////////
7612 . ////////////////////////////////////////////////////////////////////////////
7614 .chapter "Domain, host, address, and local part lists" &&&
7615 "CHAPdomhosaddlists" &&&
7616 "Domain, host, and address lists"
7617 .scindex IIDdohoadli "lists of domains; hosts; etc."
7618 A number of Exim configuration options contain lists of domains, hosts,
7619 email addresses, or local parts. For example, the &%hold_domains%& option
7620 contains a list of domains whose delivery is currently suspended. These lists
7621 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
7622 arguments to expansion conditions such as &%match_domain%&.
7624 Each item in one of these lists is a pattern to be matched against a domain,
7625 host, email address, or local part, respectively. In the sections below, the
7626 different types of pattern for each case are described, but first we cover some
7627 general facilities that apply to all four kinds of list.
7631 .section "Expansion of lists" "SECID75"
7632 .cindex "expansion" "of lists"
7633 Each list is expanded as a single string before it is used. The result of
7634 expansion must be a list, possibly containing empty items, which is split up
7635 into separate items for matching. By default, colon is the separator character,
7636 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
7637 &<<SECTempitelis>>& for details of the list syntax; the second of these
7638 discusses the way to specify empty list items.
7641 If the string expansion is forced to fail, Exim behaves as if the item it is
7642 testing (domain, host, address, or local part) is not in the list. Other
7643 expansion failures cause temporary errors.
7645 If an item in a list is a regular expression, backslashes, dollars and possibly
7646 other special characters in the expression must be protected against
7647 misinterpretation by the string expander. The easiest way to do this is to use
7648 the &`\N`& expansion feature to indicate that the contents of the regular
7649 expression should not be expanded. For example, in an ACL you might have:
7651 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
7652 ${lookup{$domain}lsearch{/badsenders/bydomain}}
7654 The first item is a regular expression that is protected from expansion by
7655 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
7656 senders based on the receiving domain.
7661 .section "Negated items in lists" "SECID76"
7662 .cindex "list" "negation"
7663 .cindex "negation" "in lists"
7664 Items in a list may be positive or negative. Negative items are indicated by a
7665 leading exclamation mark, which may be followed by optional white space. A list
7666 defines a set of items (domains, etc). When Exim processes one of these lists,
7667 it is trying to find out whether a domain, host, address, or local part
7668 (respectively) is in the set that is defined by the list. It works like this:
7670 The list is scanned from left to right. If a positive item is matched, the
7671 subject that is being checked is in the set; if a negative item is matched, the
7672 subject is not in the set. If the end of the list is reached without the
7673 subject having matched any of the patterns, it is in the set if the last item
7674 was a negative one, but not if it was a positive one. For example, the list in
7676 domainlist relay_to_domains = !a.b.c : *.b.c
7678 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
7679 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
7680 list is positive. However, if the setting were
7682 domainlist relay_to_domains = !a.b.c
7684 then all domains other than &'a.b.c'& would match because the last item in the
7685 list is negative. In other words, a list that ends with a negative item behaves
7686 as if it had an extra item &`:*`& on the end.
7688 Another way of thinking about positive and negative items in lists is to read
7689 the connector as &"or"& after a positive item and as &"and"& after a negative
7694 .section "File names in lists" "SECTfilnamlis"
7695 .cindex "list" "file name in"
7696 If an item in a domain, host, address, or local part list is an absolute file
7697 name (beginning with a slash character), each line of the file is read and
7698 processed as if it were an independent item in the list, except that further
7699 file names are not allowed,
7700 and no expansion of the data from the file takes place.
7701 Empty lines in the file are ignored, and the file may also contain comment
7705 For domain and host lists, if a # character appears anywhere in a line of the
7706 file, it and all following characters are ignored.
7708 Because local parts may legitimately contain # characters, a comment in an
7709 address list or local part list file is recognized only if # is preceded by
7710 white space or the start of the line. For example:
7712 not#comment@x.y.z # but this is a comment
7716 Putting a file name in a list has the same effect as inserting each line of the
7717 file as an item in the list (blank lines and comments excepted). However, there
7718 is one important difference: the file is read each time the list is processed,
7719 so if its contents vary over time, Exim's behaviour changes.
7721 If a file name is preceded by an exclamation mark, the sense of any match
7722 within the file is inverted. For example, if
7724 hold_domains = !/etc/nohold-domains
7726 and the file contains the lines
7731 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
7732 any domain matching &`*.b.c`& is not.
7736 .section "An lsearch file is not an out-of-line list" "SECID77"
7737 As will be described in the sections that follow, lookups can be used in lists
7738 to provide indexed methods of checking list membership. There has been some
7739 confusion about the way &(lsearch)& lookups work in lists. Because
7740 an &(lsearch)& file contains plain text and is scanned sequentially, it is
7741 sometimes thought that it is allowed to contain wild cards and other kinds of
7742 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
7743 always fixed strings, just as for any other single-key lookup type.
7745 If you want to use a file to contain wild-card patterns that form part of a
7746 list, just give the file name on its own, without a search type, as described
7747 in the previous section. You could also use the &(wildlsearch)& or
7748 &(nwildlsearch)&, but there is no advantage in doing this.
7753 .section "Named lists" "SECTnamedlists"
7754 .cindex "named lists"
7755 .cindex "list" "named"
7756 A list of domains, hosts, email addresses, or local parts can be given a name
7757 which is then used to refer to the list elsewhere in the configuration. This is
7758 particularly convenient if the same list is required in several different
7759 places. It also allows lists to be given meaningful names, which can improve
7760 the readability of the configuration. For example, it is conventional to define
7761 a domain list called &'local_domains'& for all the domains that are handled
7762 locally on a host, using a configuration line such as
7764 domainlist local_domains = localhost:my.dom.example
7766 Named lists are referenced by giving their name preceded by a plus sign, so,
7767 for example, a router that is intended to handle local domains would be
7768 configured with the line
7770 domains = +local_domains
7772 The first router in a configuration is often one that handles all domains
7773 except the local ones, using a configuration with a negated item like this:
7777 domains = ! +local_domains
7778 transport = remote_smtp
7781 The four kinds of named list are created by configuration lines starting with
7782 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
7783 respectively. Then there follows the name that you are defining, followed by an
7784 equals sign and the list itself. For example:
7786 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
7787 addresslist bad_senders = cdb;/etc/badsenders
7789 A named list may refer to other named lists:
7791 domainlist dom1 = first.example : second.example
7792 domainlist dom2 = +dom1 : third.example
7793 domainlist dom3 = fourth.example : +dom2 : fifth.example
7795 &*Warning*&: If the last item in a referenced list is a negative one, the
7796 effect may not be what you intended, because the negation does not propagate
7797 out to the higher level. For example, consider:
7799 domainlist dom1 = !a.b
7800 domainlist dom2 = +dom1 : *.b
7802 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
7803 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
7804 means it matches the second list as well. The effect is not the same as
7806 domainlist dom2 = !a.b : *.b
7808 where &'x.y'& does not match. It's best to avoid negation altogether in
7809 referenced lists if you can.
7811 Named lists may have a performance advantage. When Exim is routing an
7812 address or checking an incoming message, it caches the result of tests on named
7813 lists. So, if you have a setting such as
7815 domains = +local_domains
7817 on several of your routers
7818 or in several ACL statements,
7819 the actual test is done only for the first one. However, the caching works only
7820 if there are no expansions within the list itself or any sublists that it
7821 references. In other words, caching happens only for lists that are known to be
7822 the same each time they are referenced.
7824 By default, there may be up to 16 named lists of each type. This limit can be
7825 extended by changing a compile-time variable. The use of domain and host lists
7826 is recommended for concepts such as local domains, relay domains, and relay
7827 hosts. The default configuration is set up like this.
7831 .section "Named lists compared with macros" "SECID78"
7832 .cindex "list" "named compared with macro"
7833 .cindex "macro" "compared with named list"
7834 At first sight, named lists might seem to be no different from macros in the
7835 configuration file. However, macros are just textual substitutions. If you
7838 ALIST = host1 : host2
7839 auth_advertise_hosts = !ALIST
7841 it probably won't do what you want, because that is exactly the same as
7843 auth_advertise_hosts = !host1 : host2
7845 Notice that the second host name is not negated. However, if you use a host
7848 hostlist alist = host1 : host2
7849 auth_advertise_hosts = ! +alist
7851 the negation applies to the whole list, and so that is equivalent to
7853 auth_advertise_hosts = !host1 : !host2
7857 .section "Named list caching" "SECID79"
7858 .cindex "list" "caching of named"
7859 .cindex "caching" "named lists"
7860 While processing a message, Exim caches the result of checking a named list if
7861 it is sure that the list is the same each time. In practice, this means that
7862 the cache operates only if the list contains no $ characters, which guarantees
7863 that it will not change when it is expanded. Sometimes, however, you may have
7864 an expanded list that you know will be the same each time within a given
7865 message. For example:
7867 domainlist special_domains = \
7868 ${lookup{$sender_host_address}cdb{/some/file}}
7870 This provides a list of domains that depends only on the sending host's IP
7871 address. If this domain list is referenced a number of times (for example,
7872 in several ACL lines, or in several routers) the result of the check is not
7873 cached by default, because Exim does not know that it is going to be the
7874 same list each time.
7876 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
7877 cache the result anyway. For example:
7879 domainlist_cache special_domains = ${lookup{...
7881 If you do this, you should be absolutely sure that caching is going to do
7882 the right thing in all cases. When in doubt, leave it out.
7886 .section "Domain lists" "SECTdomainlist"
7887 .cindex "domain list" "patterns for"
7888 .cindex "list" "domain list"
7889 Domain lists contain patterns that are to be matched against a mail domain.
7890 The following types of item may appear in domain lists:
7893 .cindex "primary host name"
7894 .cindex "host name" "matched in domain list"
7895 .oindex "&%primary_hostname%&"
7896 .cindex "domain list" "matching primary host name"
7897 .cindex "@ in a domain list"
7898 If a pattern consists of a single @ character, it matches the local host name,
7899 as set by the &%primary_hostname%& option (or defaulted). This makes it
7900 possible to use the same configuration file on several different hosts that
7901 differ only in their names.
7903 .cindex "@[] in a domain list"
7904 .cindex "domain list" "matching local IP interfaces"
7905 .cindex "domain literal"
7906 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
7907 in square brackets (as in an email address that contains a domain literal), but
7908 only if that IP address is recognized as local for email routing purposes. The
7909 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
7910 control which of a host's several IP addresses are treated as local.
7911 In today's Internet, the use of domain literals is controversial.
7914 .cindex "@mx_primary"
7915 .cindex "@mx_secondary"
7916 .cindex "domain list" "matching MX pointers to local host"
7917 If a pattern consists of the string &`@mx_any`& it matches any domain that
7918 has an MX record pointing to the local host or to any host that is listed in
7919 .oindex "&%hosts_treat_as_local%&"
7920 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
7921 are similar, except that the first matches only when a primary MX target is the
7922 local host, and the second only when no primary MX target is the local host,
7923 but a secondary MX target is. &"Primary"& means an MX record with the lowest
7924 preference value &-- there may of course be more than one of them.
7926 The MX lookup that takes place when matching a pattern of this type is
7927 performed with the resolver options for widening names turned off. Thus, for
7928 example, a single-component domain will &'not'& be expanded by adding the
7929 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
7930 options of the &(dnslookup)& router for a discussion of domain widening.
7932 Sometimes you may want to ignore certain IP addresses when using one of these
7933 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
7934 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
7935 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
7936 on a router). For example:
7938 domains = @mx_any/ignore=127.0.0.1
7940 This example matches any domain that has an MX record pointing to one of
7941 the local host's IP addresses other than 127.0.0.1.
7943 The list of IP addresses is in fact processed by the same code that processes
7944 host lists, so it may contain CIDR-coded network specifications and it may also
7945 contain negative items.
7947 Because the list of IP addresses is a sublist within a domain list, you have to
7948 be careful about delimiters if there is more than one address. Like any other
7949 list, the default delimiter can be changed. Thus, you might have:
7951 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
7952 an.other.domain : ...
7954 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
7955 involved, it is easiest to change the delimiter for the main list as well:
7957 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
7958 an.other.domain ? ...
7961 .cindex "asterisk" "in domain list"
7962 .cindex "domain list" "asterisk in"
7963 .cindex "domain list" "matching &""ends with""&"
7964 If a pattern starts with an asterisk, the remaining characters of the pattern
7965 are compared with the terminating characters of the domain. The use of &"*"& in
7966 domain lists differs from its use in partial matching lookups. In a domain
7967 list, the character following the asterisk need not be a dot, whereas partial
7968 matching works only in terms of dot-separated components. For example, a domain
7969 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
7973 .cindex "regular expressions" "in domain list"
7974 .cindex "domain list" "matching regular expression"
7975 If a pattern starts with a circumflex character, it is treated as a regular
7976 expression, and matched against the domain using a regular expression matching
7977 function. The circumflex is treated as part of the regular expression.
7978 Email domains are case-independent, so this regular expression match is by
7979 default case-independent, but you can make it case-dependent by starting it
7980 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
7981 are given in chapter &<<CHAPregexp>>&.
7983 &*Warning*&: Because domain lists are expanded before being processed, you
7984 must escape any backslash and dollar characters in the regular expression, or
7985 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
7986 it is not to be expanded (unless you really do want to build a regular
7987 expression by expansion, of course).
7989 .cindex "lookup" "in domain list"
7990 .cindex "domain list" "matching by lookup"
7991 If a pattern starts with the name of a single-key lookup type followed by a
7992 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
7993 must be a file name in a suitable format for the lookup type. For example, for
7994 &"cdb;"& it must be an absolute path:
7996 domains = cdb;/etc/mail/local_domains.cdb
7998 The appropriate type of lookup is done on the file using the domain name as the
7999 key. In most cases, the data that is looked up is not used; Exim is interested
8000 only in whether or not the key is present in the file. However, when a lookup
8001 is used for the &%domains%& option on a router
8002 or a &%domains%& condition in an ACL statement, the data is preserved in the
8003 &$domain_data$& variable and can be referred to in other router options or
8004 other statements in the same ACL.
8007 Any of the single-key lookup type names may be preceded by
8008 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8010 domains = partial-dbm;/partial/domains
8012 This causes partial matching logic to be invoked; a description of how this
8013 works is given in section &<<SECTpartiallookup>>&.
8016 .cindex "asterisk" "in lookup type"
8017 Any of the single-key lookup types may be followed by an asterisk. This causes
8018 a default lookup for a key consisting of a single asterisk to be done if the
8019 original lookup fails. This is not a useful feature when using a domain list to
8020 select particular domains (because any domain would match), but it might have
8021 value if the result of the lookup is being used via the &$domain_data$&
8024 If the pattern starts with the name of a query-style lookup type followed by a
8025 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8026 pattern must be an appropriate query for the lookup type, as described in
8027 chapter &<<CHAPfdlookup>>&. For example:
8029 hold_domains = mysql;select domain from holdlist \
8030 where domain = '${quote_mysql:$domain}';
8032 In most cases, the data that is looked up is not used (so for an SQL query, for
8033 example, it doesn't matter what field you select). Exim is interested only in
8034 whether or not the query succeeds. However, when a lookup is used for the
8035 &%domains%& option on a router, the data is preserved in the &$domain_data$&
8036 variable and can be referred to in other options.
8038 .cindex "domain list" "matching literal domain name"
8039 If none of the above cases apply, a caseless textual comparison is made
8040 between the pattern and the domain.
8043 Here is an example that uses several different kinds of pattern:
8045 domainlist funny_domains = \
8048 *.foundation.fict.example : \
8049 \N^[1-2]\d{3}\.fict\.example$\N : \
8050 partial-dbm;/opt/data/penguin/book : \
8051 nis;domains.byname : \
8052 nisplus;[name=$domain,status=local],domains.org_dir
8054 There are obvious processing trade-offs among the various matching modes. Using
8055 an asterisk is faster than a regular expression, and listing a few names
8056 explicitly probably is too. The use of a file or database lookup is expensive,
8057 but may be the only option if hundreds of names are required. Because the
8058 patterns are tested in order, it makes sense to put the most commonly matched
8063 .section "Host lists" "SECThostlist"
8064 .cindex "host list" "patterns in"
8065 .cindex "list" "host list"
8066 Host lists are used to control what remote hosts are allowed to do. For
8067 example, some hosts may be allowed to use the local host as a relay, and some
8068 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8069 two different ways, by name or by IP address. In a host list, some types of
8070 pattern are matched to a host name, and some are matched to an IP address.
8071 You need to be particularly careful with this when single-key lookups are
8072 involved, to ensure that the right value is being used as the key.
8075 .section "Special host list patterns" "SECID80"
8076 .cindex "empty item in hosts list"
8077 .cindex "host list" "empty string in"
8078 If a host list item is the empty string, it matches only when no remote host is
8079 involved. This is the case when a message is being received from a local
8080 process using SMTP on the standard input, that is, when a TCP/IP connection is
8083 .cindex "asterisk" "in host list"
8084 The special pattern &"*"& in a host list matches any host or no host. Neither
8085 the IP address nor the name is actually inspected.
8089 .section "Host list patterns that match by IP address" "SECThoslispatip"
8090 .cindex "host list" "matching IP addresses"
8091 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8092 the incoming address actually appears in the IPv6 host as
8093 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8094 list, it is converted into a traditional IPv4 address first. (Not all operating
8095 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8098 The following types of pattern in a host list check the remote host by
8099 inspecting its IP address:
8102 If the pattern is a plain domain name (not a regular expression, not starting
8103 with *, not a lookup of any kind), Exim calls the operating system function
8104 to find the associated IP address(es). Exim uses the newer
8105 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8106 This typically causes a forward DNS lookup of the name. The result is compared
8107 with the IP address of the subject host.
8109 If there is a temporary problem (such as a DNS timeout) with the host name
8110 lookup, a temporary error occurs. For example, if the list is being used in an
8111 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8112 temporary SMTP error code. If no IP address can be found for the host name,
8113 what happens is described in section &<<SECTbehipnot>>& below.
8116 .cindex "@ in a host list"
8117 If the pattern is &"@"&, the primary host name is substituted and used as a
8118 domain name, as just described.
8121 If the pattern is an IP address, it is matched against the IP address of the
8122 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8123 IPv6 addresses can be given in colon-separated format, but the colons have to
8124 be doubled so as not to be taken as item separators when the default list
8125 separator is used. IPv6 addresses are recognized even when Exim is compiled
8126 without IPv6 support. This means that if they appear in a host list on an
8127 IPv4-only host, Exim will not treat them as host names. They are just addresses
8128 that can never match a client host.
8131 .cindex "@[] in a host list"
8132 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8133 the local host. For example, if the local host is an IPv4 host with one
8134 interface address 10.45.23.56, these two ACL statements have the same effect:
8136 accept hosts = 127.0.0.1 : 10.45.23.56
8140 .cindex "CIDR notation"
8141 If the pattern is an IP address followed by a slash and a mask length (for
8142 example 10.11.42.0/24), it is matched against the IP address of the subject
8143 host under the given mask. This allows, an entire network of hosts to be
8144 included (or excluded) by a single item. The mask uses CIDR notation; it
8145 specifies the number of address bits that must match, starting from the most
8146 significant end of the address.
8148 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8149 of a range of addresses. It is the number of bits in the network portion of the
8150 address. The above example specifies a 24-bit netmask, so it matches all 256
8151 addresses in the 10.11.42.0 network. An item such as
8155 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8156 32 for an IPv4 address is the same as no mask at all; just a single address
8159 Here is another example which shows an IPv4 and an IPv6 network:
8161 recipient_unqualified_hosts = 192.168.0.0/16: \
8162 3ffe::ffff::836f::::/48
8164 The doubling of list separator characters applies only when these items
8165 appear inline in a host list. It is not required when indirecting via a file.
8168 recipient_unqualified_hosts = /opt/exim/unqualnets
8170 could make use of a file containing
8175 to have exactly the same effect as the previous example. When listing IPv6
8176 addresses inline, it is usually more convenient to use the facility for
8177 changing separator characters. This list contains the same two networks:
8179 recipient_unqualified_hosts = <; 172.16.0.0/12; \
8182 The separator is changed to semicolon by the leading &"<;"& at the start of the
8188 .section "Host list patterns for single-key lookups by host address" &&&
8189 "SECThoslispatsikey"
8190 .cindex "host list" "lookup of IP address"
8191 When a host is to be identified by a single-key lookup of its complete IP
8192 address, the pattern takes this form:
8194 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8198 hosts_lookup = net-cdb;/hosts-by-ip.db
8200 The text form of the IP address of the subject host is used as the lookup key.
8201 IPv6 addresses are converted to an unabbreviated form, using lower case
8202 letters, with dots as separators because colon is the key terminator in
8203 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
8204 quoting the keys, but this is a facility that was added later.] The data
8205 returned by the lookup is not used.
8207 .cindex "IP address" "masking"
8208 .cindex "host list" "masked IP address"
8209 Single-key lookups can also be performed using masked IP addresses, using
8210 patterns of this form:
8212 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8216 net24-dbm;/networks.db
8218 The IP address of the subject host is masked using <&'number'&> as the mask
8219 length. A textual string is constructed from the masked value, followed by the
8220 mask, and this is used as the lookup key. For example, if the host's IP address
8221 is 192.168.34.6, the key that is looked up for the above example is
8222 &"192.168.34.0/24"&.
8224 When an IPv6 address is converted to a string, dots are normally used instead
8225 of colons, so that keys in &(lsearch)& files need not contain colons (which
8226 terminate &(lsearch)& keys). This was implemented some time before the ability
8227 to quote keys was made available in &(lsearch)& files. However, the more
8228 recently implemented &(iplsearch)& files do require colons in IPv6 keys
8229 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
8230 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
8231 converted using colons and not dots. In all cases, full, unabbreviated IPv6
8232 addresses are always used.
8234 Ideally, it would be nice to tidy up this anomalous situation by changing to
8235 colons in all cases, given that quoting is now available for &(lsearch)&.
8236 However, this would be an incompatible change that might break some existing
8239 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
8240 IPv6 address) is not the same as specifying just &%net-%& without a number. In
8241 the former case the key strings include the mask value, whereas in the latter
8242 case the IP address is used on its own.
8246 .section "Host list patterns that match by host name" "SECThoslispatnam"
8247 .cindex "host" "lookup failures"
8248 .cindex "unknown host name"
8249 .cindex "host list" "matching host name"
8250 There are several types of pattern that require Exim to know the name of the
8251 remote host. These are either wildcard patterns or lookups by name. (If a
8252 complete hostname is given without any wildcarding, it is used to find an IP
8253 address to match against, as described in section &<<SECThoslispatip>>&
8256 If the remote host name is not already known when Exim encounters one of these
8257 patterns, it has to be found from the IP address.
8258 Although many sites on the Internet are conscientious about maintaining reverse
8259 DNS data for their hosts, there are also many that do not do this.
8260 Consequently, a name cannot always be found, and this may lead to unwanted
8261 effects. Take care when configuring host lists with wildcarded name patterns.
8262 Consider what will happen if a name cannot be found.
8264 Because of the problems of determining host names from IP addresses, matching
8265 against host names is not as common as matching against IP addresses.
8267 By default, in order to find a host name, Exim first does a reverse DNS lookup;
8268 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
8269 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
8270 are done can be changed by setting the &%host_lookup_order%& option. For
8271 security, once Exim has found one or more names, it looks up the IP addresses
8272 for these names and compares them with the IP address that it started with.
8273 Only those names whose IP addresses match are accepted. Any other names are
8274 discarded. If no names are left, Exim behaves as if the host name cannot be
8275 found. In the most common case there is only one name and one IP address.
8277 There are some options that control what happens if a host name cannot be
8278 found. These are described in section &<<SECTbehipnot>>& below.
8280 .cindex "host" "alias for"
8281 .cindex "alias for host"
8282 As a result of aliasing, hosts may have more than one name. When processing any
8283 of the following types of pattern, all the host's names are checked:
8286 .cindex "asterisk" "in host list"
8287 If a pattern starts with &"*"& the remainder of the item must match the end of
8288 the host name. For example, &`*.b.c`& matches all hosts whose names end in
8289 &'.b.c'&. This special simple form is provided because this is a very common
8290 requirement. Other kinds of wildcarding require the use of a regular
8293 .cindex "regular expressions" "in host list"
8294 .cindex "host list" "regular expression in"
8295 If the item starts with &"^"& it is taken to be a regular expression which is
8296 matched against the host name. Host names are case-independent, so this regular
8297 expression match is by default case-independent, but you can make it
8298 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
8299 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
8304 is a regular expression that matches either of the two hosts &'a.c.d'& or
8305 &'b.c.d'&. When a regular expression is used in a host list, you must take care
8306 that backslash and dollar characters are not misinterpreted as part of the
8307 string expansion. The simplest way to do this is to use &`\N`& to mark that
8308 part of the string as non-expandable. For example:
8310 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
8312 &*Warning*&: If you want to match a complete host name, you must include the
8313 &`$`& terminating metacharacter in the regular expression, as in the above
8314 example. Without it, a match at the start of the host name is all that is
8321 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
8322 .cindex "host" "lookup failures, permanent"
8323 While processing a host list, Exim may need to look up an IP address from a
8324 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
8325 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
8326 behaviour when it fails to find the information it is seeking is the same.
8328 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
8329 apply to temporary DNS errors, whose handling is described in the next section.
8331 .cindex "&`+include_unknown`&"
8332 .cindex "&`+ignore_unknown`&"
8333 Exim parses a host list from left to right. If it encounters a permanent
8334 lookup failure in any item in the host list before it has found a match,
8335 Exim treats it as a failure and the default behavior is as if the host
8336 does not match the list. This may not always be what you want to happen.
8337 To change Exim's behaviour, the special items &`+include_unknown`& or
8338 &`+ignore_unknown`& may appear in the list (at top level &-- they are
8339 not recognized in an indirected file).
8342 If any item that follows &`+include_unknown`& requires information that
8343 cannot found, Exim behaves as if the host does match the list. For example,
8345 host_reject_connection = +include_unknown:*.enemy.ex
8347 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
8348 any hosts whose name it cannot find.
8351 If any item that follows &`+ignore_unknown`& requires information that cannot
8352 be found, Exim ignores that item and proceeds to the rest of the list. For
8355 accept hosts = +ignore_unknown : friend.example : \
8358 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
8359 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
8360 name can be found for 192.168.4.5, it is rejected.
8363 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
8364 list. The effect of each one lasts until the next, or until the end of the
8367 .section "Mixing wildcarded host names and addresses in host lists" &&&
8369 .cindex "host list" "mixing names and addresses in"
8371 This section explains the host/ip processing logic with the same concepts
8372 as the previous section, but specifically addresses what happens when a
8373 wildcarded hostname is one of the items in the hostlist.
8376 If you have name lookups or wildcarded host names and
8377 IP addresses in the same host list, you should normally put the IP
8378 addresses first. For example, in an ACL you could have:
8380 accept hosts = 10.9.8.7 : *.friend.example
8382 The reason you normally would order it this way lies in the
8383 left-to-right way that Exim processes lists. It can test IP addresses
8384 without doing any DNS lookups, but when it reaches an item that requires
8385 a host name, it fails if it cannot find a host name to compare with the
8386 pattern. If the above list is given in the opposite order, the
8387 &%accept%& statement fails for a host whose name cannot be found, even
8388 if its IP address is 10.9.8.7.
8391 If you really do want to do the name check first, and still recognize the IP
8392 address, you can rewrite the ACL like this:
8394 accept hosts = *.friend.example
8395 accept hosts = 10.9.8.7
8397 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
8398 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
8399 &`+ignore_unknown`&, which was discussed in depth in the first example in
8404 .section "Temporary DNS errors when looking up host information" &&&
8406 .cindex "host" "lookup failures, temporary"
8407 .cindex "&`+include_defer`&"
8408 .cindex "&`+ignore_defer`&"
8409 A temporary DNS lookup failure normally causes a defer action (except when
8410 &%dns_again_means_nonexist%& converts it into a permanent error). However,
8411 host lists can include &`+ignore_defer`& and &`+include_defer`&, analagous to
8412 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
8413 section. These options should be used with care, probably only in non-critical
8414 host lists such as whitelists.
8418 .section "Host list patterns for single-key lookups by host name" &&&
8419 "SECThoslispatnamsk"
8420 .cindex "unknown host name"
8421 .cindex "host list" "matching host name"
8422 If a pattern is of the form
8424 <&'single-key-search-type'&>;<&'search-data'&>
8428 dbm;/host/accept/list
8430 a single-key lookup is performed, using the host name as its key. If the
8431 lookup succeeds, the host matches the item. The actual data that is looked up
8434 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
8435 keys in the file, not IP addresses. If you want to do lookups based on IP
8436 addresses, you must precede the search type with &"net-"& (see section
8437 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
8438 two items in the same list, one doing an address lookup and one doing a name
8439 lookup, both using the same file.
8443 .section "Host list patterns for query-style lookups" "SECID81"
8444 If a pattern is of the form
8446 <&'query-style-search-type'&>;<&'query'&>
8448 the query is obeyed, and if it succeeds, the host matches the item. The actual
8449 data that is looked up is not used. The variables &$sender_host_address$& and
8450 &$sender_host_name$& can be used in the query. For example:
8452 hosts_lookup = pgsql;\
8453 select ip from hostlist where ip='$sender_host_address'
8455 The value of &$sender_host_address$& for an IPv6 address contains colons. You
8456 can use the &%sg%& expansion item to change this if you need to. If you want to
8457 use masked IP addresses in database queries, you can use the &%mask%& expansion
8460 If the query contains a reference to &$sender_host_name$&, Exim automatically
8461 looks up the host name if it has not already done so. (See section
8462 &<<SECThoslispatnam>>& for comments on finding host names.)
8464 Historical note: prior to release 4.30, Exim would always attempt to find a
8465 host name before running the query, unless the search type was preceded by
8466 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
8467 still recognized for query-style lookups, but its presence or absence has no
8468 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
8469 See section &<<SECThoslispatsikey>>&.)
8475 .section "Address lists" "SECTaddresslist"
8476 .cindex "list" "address list"
8477 .cindex "address list" "empty item"
8478 .cindex "address list" "patterns"
8479 Address lists contain patterns that are matched against mail addresses. There
8480 is one special case to be considered: the sender address of a bounce message is
8481 always empty. You can test for this by providing an empty item in an address
8482 list. For example, you can set up a router to process bounce messages by
8483 using this option setting:
8487 The presence of the colon creates an empty item. If you do not provide any
8488 data, the list is empty and matches nothing. The empty sender can also be
8489 detected by a regular expression that matches an empty string,
8490 and by a query-style lookup that succeeds when &$sender_address$& is empty.
8492 Non-empty items in an address list can be straightforward email addresses. For
8495 senders = jbc@askone.example : hs@anacreon.example
8497 A certain amount of wildcarding is permitted. If a pattern contains an @
8498 character, but is not a regular expression and does not begin with a
8499 semicolon-terminated lookup type (described below), the local part of the
8500 subject address is compared with the local part of the pattern, which may start
8501 with an asterisk. If the local parts match, the domain is checked in exactly
8502 the same way as for a pattern in a domain list. For example, the domain can be
8503 wildcarded, refer to a named list, or be a lookup:
8505 deny senders = *@*.spamming.site:\
8506 *@+hostile_domains:\
8507 bozo@partial-lsearch;/list/of/dodgy/sites:\
8508 *@dbm;/bad/domains.db
8510 .cindex "local part" "starting with !"
8511 .cindex "address list" "local part starting with !"
8512 If a local part that begins with an exclamation mark is required, it has to be
8513 specified using a regular expression, because otherwise the exclamation mark is
8514 treated as a sign of negation, as is standard in lists.
8516 If a non-empty pattern that is not a regular expression or a lookup does not
8517 contain an @ character, it is matched against the domain part of the subject
8518 address. The only two formats that are recognized this way are a literal
8519 domain, or a domain pattern that starts with *. In both these cases, the effect
8520 is the same as if &`*@`& preceded the pattern. For example:
8522 deny senders = enemy.domain : *.enemy.domain
8525 The following kinds of more complicated address list pattern can match any
8526 address, including the empty address that is characteristic of bounce message
8530 .cindex "regular expressions" "in address list"
8531 .cindex "address list" "regular expression in"
8532 If (after expansion) a pattern starts with &"^"&, a regular expression match is
8533 done against the complete address, with the pattern as the regular expression.
8534 You must take care that backslash and dollar characters are not misinterpreted
8535 as part of the string expansion. The simplest way to do this is to use &`\N`&
8536 to mark that part of the string as non-expandable. For example:
8538 deny senders = \N^.*this.*@example\.com$\N : \
8539 \N^\d{8}.+@spamhaus.example$\N : ...
8541 The &`\N`& sequences are removed by the expansion, so these items do indeed
8542 start with &"^"& by the time they are being interpreted as address patterns.
8545 .cindex "address list" "lookup for complete address"
8546 Complete addresses can be looked up by using a pattern that starts with a
8547 lookup type terminated by a semicolon, followed by the data for the lookup. For
8550 deny senders = cdb;/etc/blocked.senders : \
8551 mysql;select address from blocked where \
8552 address='${quote_mysql:$sender_address}'
8554 Both query-style and single-key lookup types can be used. For a single-key
8555 lookup type, Exim uses the complete address as the key. However, empty keys are
8556 not supported for single-key lookups, so a match against the empty address
8557 always fails. This restriction does not apply to query-style lookups.
8559 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
8560 cannot be used, and is ignored if specified, with an entry being written to the
8562 .cindex "*@ with single-key lookup"
8563 However, you can configure lookup defaults, as described in section
8564 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
8565 default. For example, with this lookup:
8567 accept senders = lsearch*@;/some/file
8569 the file could contains lines like this:
8571 user1@domain1.example
8574 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
8577 nimrod@jaeger.example
8581 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
8582 would mean that every address matches, thus rendering the test useless.
8584 &*Warning 2*&: Do not confuse these two kinds of item:
8586 deny recipients = dbm*@;/some/file
8587 deny recipients = *@dbm;/some/file
8589 The first does a whole address lookup, with defaulting, as just described,
8590 because it starts with a lookup type. The second matches the local part and
8591 domain independently, as described in a bullet point below.
8595 The following kinds of address list pattern can match only non-empty addresses.
8596 If the subject address is empty, a match against any of these pattern types
8601 .cindex "@@ with single-key lookup"
8602 .cindex "address list" "@@ lookup type"
8603 .cindex "address list" "split local part and domain"
8604 If a pattern starts with &"@@"& followed by a single-key lookup item
8605 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
8606 split into a local part and a domain. The domain is looked up in the file. If
8607 it is not found, there is no match. If it is found, the data that is looked up
8608 from the file is treated as a colon-separated list of local part patterns, each
8609 of which is matched against the subject local part in turn.
8611 .cindex "asterisk" "in address list"
8612 The lookup may be a partial one, and/or one involving a search for a default
8613 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
8614 patterns that are looked up can be regular expressions or begin with &"*"&, or
8615 even be further lookups. They may also be independently negated. For example,
8618 deny senders = @@dbm;/etc/reject-by-domain
8620 the data from which the DBM file is built could contain lines like
8622 baddomain.com: !postmaster : *
8624 to reject all senders except &%postmaster%& from that domain.
8626 .cindex "local part" "starting with !"
8627 If a local part that actually begins with an exclamation mark is required, it
8628 has to be specified using a regular expression. In &(lsearch)& files, an entry
8629 may be split over several lines by indenting the second and subsequent lines,
8630 but the separating colon must still be included at line breaks. White space
8631 surrounding the colons is ignored. For example:
8633 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
8636 As in all colon-separated lists in Exim, a colon can be included in an item by
8639 If the last item in the list starts with a right angle-bracket, the remainder
8640 of the item is taken as a new key to look up in order to obtain a continuation
8641 list of local parts. The new key can be any sequence of characters. Thus one
8642 might have entries like
8644 aol.com: spammer1 : spammer 2 : >*
8645 xyz.com: spammer3 : >*
8648 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
8649 local parts for all domains, in addition to the specific local parts listed for
8650 each domain. Of course, using this feature costs another lookup each time a
8651 chain is followed, but the effort needed to maintain the data is reduced.
8653 .cindex "loop" "in lookups"
8654 It is possible to construct loops using this facility, and in order to catch
8655 them, the chains may be no more than fifty items long.
8658 The @@<&'lookup'&> style of item can also be used with a query-style
8659 lookup, but in this case, the chaining facility is not available. The lookup
8660 can only return a single list of local parts.
8663 &*Warning*&: There is an important difference between the address list items
8664 in these two examples:
8667 senders = *@+my_list
8669 In the first one, &`my_list`& is a named address list, whereas in the second
8670 example it is a named domain list.
8675 .section "Case of letters in address lists" "SECTcasletadd"
8676 .cindex "case of local parts"
8677 .cindex "address list" "case forcing"
8678 .cindex "case forcing in address lists"
8679 Domains in email addresses are always handled caselessly, but for local parts
8680 case may be significant on some systems (see &%caseful_local_part%& for how
8681 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
8682 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
8683 blocking lists should be done in a case-independent manner. Since most address
8684 lists in Exim are used for this kind of control, Exim attempts to do this by
8687 The domain portion of an address is always lowercased before matching it to an
8688 address list. The local part is lowercased by default, and any string
8689 comparisons that take place are done caselessly. This means that the data in
8690 the address list itself, in files included as plain file names, and in any file
8691 that is looked up using the &"@@"& mechanism, can be in any case. However, the
8692 keys in files that are looked up by a search type other than &(lsearch)& (which
8693 works caselessly) must be in lower case, because these lookups are not
8696 .cindex "&`+caseful`&"
8697 To allow for the possibility of caseful address list matching, if an item in
8698 an address list is the string &"+caseful"&, the original case of the local
8699 part is restored for any comparisons that follow, and string comparisons are no
8700 longer case-independent. This does not affect the domain, which remains in
8701 lower case. However, although independent matches on the domain alone are still
8702 performed caselessly, regular expressions that match against an entire address
8703 become case-sensitive after &"+caseful"& has been seen.
8707 .section "Local part lists" "SECTlocparlis"
8708 .cindex "list" "local part list"
8709 .cindex "local part" "list"
8710 Case-sensitivity in local part lists is handled in the same way as for address
8711 lists, as just described. The &"+caseful"& item can be used if required. In a
8712 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
8713 set false, the subject is lowercased and the matching is initially
8714 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
8715 matching in the local part list, but not elsewhere in the router. If
8716 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
8717 option is case-sensitive from the start.
8719 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
8720 comments are handled in the same way as address lists &-- they are recognized
8721 only if the # is preceded by white space or the start of the line.
8722 Otherwise, local part lists are matched in the same way as domain lists, except
8723 that the special items that refer to the local host (&`@`&, &`@[]`&,
8724 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
8725 Refer to section &<<SECTdomainlist>>& for details of the other available item
8727 .ecindex IIDdohoadli
8732 . ////////////////////////////////////////////////////////////////////////////
8733 . ////////////////////////////////////////////////////////////////////////////
8735 .chapter "String expansions" "CHAPexpand"
8736 .scindex IIDstrexp "expansion" "of strings"
8737 Many strings in Exim's run time configuration are expanded before use. Some of
8738 them are expanded every time they are used; others are expanded only once.
8740 When a string is being expanded it is copied verbatim from left to right except
8741 when a dollar or backslash character is encountered. A dollar specifies the
8742 start of a portion of the string that is interpreted and replaced as described
8743 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
8744 escape character, as described in the following section.
8746 Whether a string is expanded depends upon the context. Usually this is solely
8747 dependent upon the option for which a value is sought; in this documentation,
8748 options for which string expansion is performed are marked with † after
8749 the data type. ACL rules always expand strings. A couple of expansion
8750 conditions do not expand some of the brace-delimited branches, for security
8755 .section "Literal text in expanded strings" "SECTlittext"
8756 .cindex "expansion" "including literal text"
8757 An uninterpreted dollar can be included in an expanded string by putting a
8758 backslash in front of it. A backslash can be used to prevent any special
8759 character being treated specially in an expansion, including backslash itself.
8760 If the string appears in quotes in the configuration file, two backslashes are
8761 required because the quotes themselves cause interpretation of backslashes when
8762 the string is read in (see section &<<SECTstrings>>&).
8764 .cindex "expansion" "non-expandable substrings"
8765 A portion of the string can specified as non-expandable by placing it between
8766 two occurrences of &`\N`&. This is particularly useful for protecting regular
8767 expressions, which often contain backslashes and dollar signs. For example:
8769 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
8771 On encountering the first &`\N`&, the expander copies subsequent characters
8772 without interpretation until it reaches the next &`\N`& or the end of the
8777 .section "Character escape sequences in expanded strings" "SECID82"
8778 .cindex "expansion" "escape sequences"
8779 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
8780 expanded string is recognized as an escape sequence for the character newline,
8781 carriage return, or tab, respectively. A backslash followed by up to three
8782 octal digits is recognized as an octal encoding for a single character, and a
8783 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
8786 These escape sequences are also recognized in quoted strings when they are read
8787 in. Their interpretation in expansions as well is useful for unquoted strings,
8788 and for other cases such as looked-up strings that are then expanded.
8791 .section "Testing string expansions" "SECID83"
8792 .cindex "expansion" "testing"
8793 .cindex "testing" "string expansion"
8795 Many expansions can be tested by calling Exim with the &%-be%& option. This
8796 takes the command arguments, or lines from the standard input if there are no
8797 arguments, runs them through the string expansion code, and writes the results
8798 to the standard output. Variables based on configuration values are set up, but
8799 since no message is being processed, variables such as &$local_part$& have no
8800 value. Nevertheless the &%-be%& option can be useful for checking out file and
8801 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
8804 Exim gives up its root privilege when it is called with the &%-be%& option, and
8805 instead runs under the uid and gid it was called with, to prevent users from
8806 using &%-be%& for reading files to which they do not have access.
8809 If you want to test expansions that include variables whose values are taken
8810 from a message, there are two other options that can be used. The &%-bem%&
8811 option is like &%-be%& except that it is followed by a file name. The file is
8812 read as a message before doing the test expansions. For example:
8814 exim -bem /tmp/test.message '$h_subject:'
8816 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
8817 Exim message identifier. For example:
8819 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
8821 This loads the message from Exim's spool before doing the test expansions, and
8822 is therefore restricted to admin users.
8825 .section "Forced expansion failure" "SECTforexpfai"
8826 .cindex "expansion" "forced failure"
8827 A number of expansions that are described in the following section have
8828 alternative &"true"& and &"false"& substrings, enclosed in brace characters
8829 (which are sometimes called &"curly brackets"&). Which of the two strings is
8830 used depends on some condition that is evaluated as part of the expansion. If,
8831 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
8832 the entire string expansion fails in a way that can be detected by the code
8833 that requested the expansion. This is called &"forced expansion failure"&, and
8834 its consequences depend on the circumstances. In some cases it is no different
8835 from any other expansion failure, but in others a different action may be
8836 taken. Such variations are mentioned in the documentation of the option that is
8842 .section "Expansion items" "SECTexpansionitems"
8843 The following items are recognized in expanded strings. White space may be used
8844 between sub-items that are keywords or substrings enclosed in braces inside an
8845 outer set of braces, to improve readability. &*Warning*&: Within braces,
8846 white space is significant.
8849 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
8850 .cindex "expansion" "variables"
8851 Substitute the contents of the named variable, for example:
8856 The second form can be used to separate the name from subsequent alphanumeric
8857 characters. This form (using braces) is available only for variables; it does
8858 &'not'& apply to message headers. The names of the variables are given in
8859 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
8860 given, the expansion fails.
8862 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
8863 .cindex "expansion" "operators"
8864 The string is first itself expanded, and then the operation specified by
8865 <&'op'&> is applied to it. For example:
8869 The string starts with the first character after the colon, which may be
8870 leading white space. A list of operators is given in section &<<SECTexpop>>&
8871 below. The operator notation is used for simple expansion items that have just
8872 one argument, because it reduces the number of braces and therefore makes the
8873 string easier to understand.
8875 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
8876 This item inserts &"basic"& header lines. It is described with the &%header%&
8877 expansion item below.
8880 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
8881 .cindex "expansion" "calling an acl"
8882 .cindex "&%acl%&" "call from expansion"
8883 The name and zero to nine argument strings are first expanded separately. The expanded
8884 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
8885 Any unused are made empty. The variable &$acl_narg$& is set to the number of
8886 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
8887 and may use the variables; if another acl expansion is used the values
8888 are restored after it returns. If the ACL sets
8889 a value using a "message =" modifier and returns accept or deny, the value becomes
8890 the result of the expansion.
8891 If no message is set and the ACL returns accept or deny
8892 the expansion result is an empty string.
8893 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
8896 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
8897 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
8898 .cindex "expansion" "extracting cerificate fields"
8899 .cindex "&%certextract%&" "certificate fields"
8900 .cindex "certificate" "extracting fields"
8901 The <&'certificate'&> must be a variable of type certificate.
8902 The field name is expanded and used to retrive the relevant field from
8903 the certificate. Supported fields are:
8907 &`subject `& RFC4514 DN
8908 &`issuer `& RFC4514 DN
8913 &`subj_altname `& tagged list
8917 If the field is found,
8918 <&'string2'&> is expanded, and replaces the whole item;
8919 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
8920 variable &$value$& contains the value that has been extracted. Afterwards, it
8921 is restored to any previous value it might have had.
8923 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
8924 key is not found. If {<&'string2'&>} is also omitted, the value that was
8927 Some field names take optional modifiers, appended and separated by commas.
8929 The field selectors marked as "RFC4514" above
8930 output a Distinguished Name string which is
8932 parseable by Exim as a comma-separated tagged list
8933 (the exceptions being elements containin commas).
8934 RDN elements of a single type may be selected by
8935 a modifier of the type label; if so the expansion
8936 result is a list (newline-separated by default).
8937 The separator may be changed by another modifer of
8938 a right angle-bracket followed immediately by the new separator.
8939 Recognised RDN type labels include "CN", "O", "OU" and "DC".
8941 The field selectors marked as "time" above
8942 take an optional modifier of "int"
8943 for which the result is the number of seconds since epoch.
8944 Otherwise the result is a human-readable string
8945 in the timezone selected by the main "timezone" option.
8947 The field selectors marked as "list" above return a list,
8948 newline-separated by default,
8949 (embedded separator characters in elements are doubled).
8950 The separator may be changed by a modifier of
8951 a right angle-bracket followed immediately by the new separator.
8953 The field selectors marked as "tagged" above
8954 prefix each list element with a type string and an equals sign.
8955 Elements of only one type may be selected by a modifier
8956 which is one of "dns", "uri" or "mail";
8957 if so the elenment tags are omitted.
8959 If not otherwise noted field values are presented in human-readable form.
8961 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
8962 {*&<&'arg'&>&*}...}*&"
8964 This expansion dynamically loads and then calls a locally-written C function.
8965 This functionality is available only if Exim is compiled with
8969 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
8970 object so that it doesn't reload the same object file in the same Exim process
8971 (but of course Exim does start new processes frequently).
8973 There may be from zero to eight arguments to the function. When compiling
8974 a local function that is to be called in this way, &_local_scan.h_& should be
8975 included. The Exim variables and functions that are defined by that API
8976 are also available for dynamically loaded functions. The function itself
8977 must have the following type:
8979 int dlfunction(uschar **yield, int argc, uschar *argv[])
8981 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
8982 function should return one of the following values:
8984 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
8985 into the expanded string that is being built.
8987 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
8988 from &'yield'&, if it is set.
8990 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
8991 taken from &'yield'& if it is set.
8993 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
8995 When compiling a function that is to be used in this way with gcc,
8996 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
8997 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
8999 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9000 {*&<&'string3'&>&*}}*&"
9001 .cindex "expansion" "extracting substrings by key"
9002 .cindex "&%extract%&" "substrings by key"
9003 The key and <&'string1'&> are first expanded separately. Leading and trailing
9004 white space is removed from the key (but not from any of the strings). The key
9005 must not consist entirely of digits. The expanded <&'string1'&> must be of the
9008 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9011 where the equals signs and spaces (but not both) are optional. If any of the
9012 values contain white space, they must be enclosed in double quotes, and any
9013 values that are enclosed in double quotes are subject to escape processing as
9014 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9015 for the value that corresponds to the key. The search is case-insensitive. If
9016 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9017 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9018 variable &$value$& contains the value that has been extracted. Afterwards, it
9019 is restored to any previous value it might have had.
9021 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9022 key is not found. If {<&'string2'&>} is also omitted, the value that was
9023 extracted is used. Thus, for example, these two expansions are identical, and
9026 ${extract{gid}{uid=1984 gid=2001}}
9027 ${extract{gid}{uid=1984 gid=2001}{$value}}
9029 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9030 appear, for example:
9032 ${extract{Z}{A=... B=...}{$value} fail }
9034 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9035 {<&'string2'&>} must be present for &"fail"& to be recognized.
9038 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
9039 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9040 .cindex "expansion" "extracting substrings by number"
9041 .cindex "&%extract%&" "substrings by number"
9042 The <&'number'&> argument must consist entirely of decimal digits,
9043 apart from leading and trailing white space, which is ignored.
9044 This is what distinguishes this form of &%extract%& from the previous kind. It
9045 behaves in the same way, except that, instead of extracting a named field, it
9046 extracts from <&'string1'&> the field whose number is given as the first
9047 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
9048 <&'string3'&> as before.
9050 The fields in the string are separated by any one of the characters in the
9051 separator string. These may include space or tab characters.
9052 The first field is numbered one. If the number is negative, the fields are
9053 counted from the end of the string, with the rightmost one numbered -1. If the
9054 number given is zero, the entire string is returned. If the modulus of the
9055 number is greater than the number of fields in the string, the result is the
9056 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
9057 provided. For example:
9059 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
9063 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
9065 yields &"99"&. Two successive separators mean that the field between them is
9066 empty (for example, the fifth field above).
9069 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
9070 .cindex "list" "selecting by condition"
9071 .cindex "expansion" "selecting from list by condition"
9073 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9074 default, but the separator can be changed in the usual way. For each item
9075 in this list, its value is place in &$item$&, and then the condition is
9076 evaluated. If the condition is true, &$item$& is added to the output as an
9077 item in a new list; if the condition is false, the item is discarded. The
9078 separator used for the output list is the same as the one used for the
9079 input, but a separator setting is not included in the output. For example:
9081 ${filter{a:b:c}{!eq{$item}{b}}
9083 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
9084 to what it was before. See also the &*map*& and &*reduce*& expansion items.
9087 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9088 .cindex "hash function" "textual"
9089 .cindex "expansion" "textual hash"
9090 This is a textual hashing function, and was the first to be implemented in
9091 early versions of Exim. In current releases, there are other hashing functions
9092 (numeric, MD5, and SHA-1), which are described below.
9094 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
9095 <&'n'&>. If you are using fixed values for these numbers, that is, if
9096 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
9097 use the simpler operator notation that avoids some of the braces:
9099 ${hash_<n>_<m>:<string>}
9101 The second number is optional (in both notations). If <&'n'&> is greater than
9102 or equal to the length of the string, the expansion item returns the string.
9103 Otherwise it computes a new string of length <&'n'&> by applying a hashing
9104 function to the string. The new string consists of characters taken from the
9105 first <&'m'&> characters of the string
9107 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
9109 If <&'m'&> is not present the value 26 is used, so that only lower case
9110 letters appear. For example:
9112 &`$hash{3}{monty}} `& yields &`jmg`&
9113 &`$hash{5}{monty}} `& yields &`monty`&
9114 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
9117 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
9118 &*$h_*&<&'header&~name'&>&*:*&" &&&
9119 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9120 &*$bh_*&<&'header&~name'&>&*:*&" &&&
9121 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9122 &*$rh_*&<&'header&~name'&>&*:*&"
9123 .cindex "expansion" "header insertion"
9124 .vindex "&$header_$&"
9125 .vindex "&$bheader_$&"
9126 .vindex "&$rheader_$&"
9127 .cindex "header lines" "in expansion strings"
9128 .cindex "header lines" "character sets"
9129 .cindex "header lines" "decoding"
9130 Substitute the contents of the named message header line, for example
9134 The newline that terminates a header line is not included in the expansion, but
9135 internal newlines (caused by splitting the header line over several physical
9136 lines) may be present.
9138 The difference between &%rheader%&, &%bheader%&, and &%header%& is in the way
9139 the data in the header line is interpreted.
9142 .cindex "white space" "in header lines"
9143 &%rheader%& gives the original &"raw"& content of the header line, with no
9144 processing at all, and without the removal of leading and trailing white space.
9147 .cindex "base64 encoding" "in header lines"
9148 &%bheader%& removes leading and trailing white space, and then decodes base64
9149 or quoted-printable MIME &"words"& within the header text, but does no
9150 character set translation. If decoding of what looks superficially like a MIME
9151 &"word"& fails, the raw string is returned. If decoding
9152 .cindex "binary zero" "in header line"
9153 produces a binary zero character, it is replaced by a question mark &-- this is
9154 what Exim does for binary zeros that are actually received in header lines.
9157 &%header%& tries to translate the string as decoded by &%bheader%& to a
9158 standard character set. This is an attempt to produce the same string as would
9159 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
9160 returned. Translation is attempted only on operating systems that support the
9161 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
9162 a system Makefile or in &_Local/Makefile_&.
9165 In a filter file, the target character set for &%header%& can be specified by a
9166 command of the following form:
9168 headers charset "UTF-8"
9170 This command affects all references to &$h_$& (or &$header_$&) expansions in
9171 subsequently obeyed filter commands. In the absence of this command, the target
9172 character set in a filter is taken from the setting of the &%headers_charset%&
9173 option in the runtime configuration. The value of this option defaults to the
9174 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
9177 Header names follow the syntax of RFC 2822, which states that they may contain
9178 any printing characters except space and colon. Consequently, curly brackets
9179 &'do not'& terminate header names, and should not be used to enclose them as
9180 if they were variables. Attempting to do so causes a syntax error.
9182 Only header lines that are common to all copies of a message are visible to
9183 this mechanism. These are the original header lines that are received with the
9184 message, and any that are added by an ACL statement or by a system
9185 filter. Header lines that are added to a particular copy of a message by a
9186 router or transport are not accessible.
9188 For incoming SMTP messages, no header lines are visible in ACLs that are obeyed
9189 before the DATA ACL, because the header structure is not set up until the
9190 message is received. Header lines that are added in a RCPT ACL (for example)
9191 are saved until the message's incoming header lines are available, at which
9192 point they are added. When a DATA ACL is running, however, header lines added
9193 by earlier ACLs are visible.
9195 Upper case and lower case letters are synonymous in header names. If the
9196 following character is white space, the terminating colon may be omitted, but
9197 this is not recommended, because you may then forget it when it is needed. When
9198 white space terminates the header name, it is included in the expanded string.
9199 If the message does not contain the given header, the expansion item is
9200 replaced by an empty string. (See the &%def%& condition in section
9201 &<<SECTexpcond>>& for a means of testing for the existence of a header.)
9203 If there is more than one header with the same name, they are all concatenated
9204 to form the substitution string, up to a maximum length of 64K. Unless
9205 &%rheader%& is being used, leading and trailing white space is removed from
9206 each header before concatenation, and a completely empty header is ignored. A
9207 newline character is then inserted between non-empty headers, but there is no
9208 newline at the very end. For the &%header%& and &%bheader%& expansion, for
9209 those headers that contain lists of addresses, a comma is also inserted at the
9210 junctions between headers. This does not happen for the &%rheader%& expansion.
9213 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
9214 .cindex "expansion" "hmac hashing"
9216 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
9217 shared secret and some text into a message authentication code, as specified in
9218 RFC 2104. This differs from &`${md5:secret_text...}`& or
9219 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
9220 cryptographic hash, allowing for authentication that is not possible with MD5
9221 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
9222 present. For example:
9224 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
9226 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
9229 dd97e3ba5d1a61b5006108f8c8252953
9231 As an example of how this might be used, you might put in the main part of
9232 an Exim configuration:
9234 SPAMSCAN_SECRET=cohgheeLei2thahw
9236 In a router or a transport you could then have:
9239 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
9240 ${hmac{md5}{SPAMSCAN_SECRET}\
9241 {${primary_hostname},${message_exim_id},$h_message-id:}}
9243 Then given a message, you can check where it was scanned by looking at the
9244 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
9245 this header line is authentic by recomputing the authentication code from the
9246 host name, message ID and the &'Message-id:'& header line. This can be done
9247 using Exim's &%-be%& option, or by other means, for example by using the
9248 &'hmac_md5_hex()'& function in Perl.
9251 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9252 .cindex "expansion" "conditional"
9253 .cindex "&%if%&, expansion item"
9254 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
9255 item; otherwise <&'string2'&> is used. The available conditions are described
9256 in section &<<SECTexpcond>>& below. For example:
9258 ${if eq {$local_part}{postmaster} {yes}{no} }
9260 The second string need not be present; if it is not and the condition is not
9261 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
9262 be present instead of the second string (without any curly brackets). In this
9263 case, the expansion is forced to fail if the condition is not true (see section
9264 &<<SECTforexpfai>>&).
9266 If both strings are omitted, the result is the string &`true`& if the condition
9267 is true, and the empty string if the condition is false. This makes it less
9268 cumbersome to write custom ACL and router conditions. For example, instead of
9270 condition = ${if >{$acl_m4}{3}{true}{false}}
9274 condition = ${if >{$acl_m4}{3}}
9277 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9278 .cindex "expansion" "string truncation"
9279 .cindex "&%length%& expansion item"
9280 The &%length%& item is used to extract the initial portion of a string. Both
9281 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
9282 you are using a fixed value for the number, that is, if <&'string1'&> does not
9283 change when expanded, you can use the simpler operator notation that avoids
9286 ${length_<n>:<string>}
9288 The result of this item is either the first <&'n'&> characters or the whole
9289 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
9290 &%strlen%&, which gives the length of a string.
9293 .vitem "&*${listextract{*&<&'number'&>&*}&&&
9294 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9295 .cindex "expansion" "extracting list elements by number"
9296 .cindex "&%listextract%&" "extract list elements by number"
9297 .cindex "list" "extracting elements by number"
9298 The <&'number'&> argument must consist entirely of decimal digits,
9299 apart from an optional leading minus,
9300 and leading and trailing white space (which is ignored).
9302 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9303 default, but the separator can be changed in the usual way.
9305 The first field of the list is numbered one.
9306 If the number is negative, the fields are
9307 counted from the end of the list, with the rightmost one numbered -1.
9308 The numbered element of the list is extracted and placed in &$value$&,
9309 then <&'string2'&> is expanded as the result.
9311 If the modulus of the
9312 number is zero or greater than the number of fields in the string,
9313 the result is the expansion of <&'string3'&>.
9317 ${listextract{2}{x:42:99}}
9321 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
9323 yields &"result: 99"&.
9325 If {<&'string3'&>} is omitted, an empty string is used for string3.
9326 If {<&'string2'&>} is also omitted, the value that was
9328 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
9331 .vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
9332 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9333 This is the first of one of two different types of lookup item, which are both
9334 described in the next item.
9336 .vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
9337 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9338 .cindex "expansion" "lookup in"
9339 .cindex "file" "lookups"
9340 .cindex "lookup" "in expanded string"
9341 The two forms of lookup item specify data lookups in files and databases, as
9342 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
9343 lookups, and the second is used for query-style lookups. The <&'key'&>,
9344 <&'file'&>, and <&'query'&> strings are expanded before use.
9346 If there is any white space in a lookup item which is part of a filter command,
9347 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
9348 other place where white space is significant, the lookup item must be enclosed
9349 in double quotes. The use of data lookups in users' filter files may be locked
9350 out by the system administrator.
9353 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
9354 During its expansion, the variable &$value$& contains the data returned by the
9355 lookup. Afterwards it reverts to the value it had previously (at the outer
9356 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
9357 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
9358 string on failure. If <&'string2'&> is provided, it can itself be a nested
9359 lookup, thus providing a mechanism for looking up a default value when the
9360 original lookup fails.
9362 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
9363 data for the outer lookup while the parameters of the second lookup are
9364 expanded, and also while <&'string2'&> of the second lookup is expanded, should
9365 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
9366 appear, and in this case, if the lookup fails, the entire expansion is forced
9367 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
9368 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
9369 successful lookup, and nothing in the case of failure.
9371 For single-key lookups, the string &"partial"& is permitted to precede the
9372 search type in order to do partial matching, and * or *@ may follow a search
9373 type to request default lookups if the key does not match (see sections
9374 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
9376 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
9377 If a partial search is used, the variables &$1$& and &$2$& contain the wild
9378 and non-wild parts of the key during the expansion of the replacement text.
9379 They return to their previous values at the end of the lookup item.
9381 This example looks up the postmaster alias in the conventional alias file:
9383 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
9385 This example uses NIS+ to look up the full name of the user corresponding to
9386 the local part of an address, forcing the expansion to fail if it is not found:
9388 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
9393 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9394 .cindex "expansion" "list creation"
9396 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9397 default, but the separator can be changed in the usual way. For each item
9398 in this list, its value is place in &$item$&, and then <&'string2'&> is
9399 expanded and added to the output as an item in a new list. The separator used
9400 for the output list is the same as the one used for the input, but a separator
9401 setting is not included in the output. For example:
9403 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
9405 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
9406 value of &$item$& is restored to what it was before. See also the &*filter*&
9407 and &*reduce*& expansion items.
9409 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9410 .cindex "expansion" "numeric hash"
9411 .cindex "hash function" "numeric"
9412 The three strings are expanded; the first two must yield numbers. Call them
9413 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9414 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9415 can use the simpler operator notation that avoids some of the braces:
9417 ${nhash_<n>_<m>:<string>}
9419 The second number is optional (in both notations). If there is only one number,
9420 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
9421 processed by a div/mod hash function that returns two numbers, separated by a
9422 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
9425 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
9427 returns the string &"6/33"&.
9431 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
9432 .cindex "Perl" "use in expanded string"
9433 .cindex "expansion" "calling Perl from"
9434 This item is available only if Exim has been built to include an embedded Perl
9435 interpreter. The subroutine name and the arguments are first separately
9436 expanded, and then the Perl subroutine is called with those arguments. No
9437 additional arguments need be given; the maximum number permitted, including the
9438 name of the subroutine, is nine.
9440 The return value of the subroutine is inserted into the expanded string, unless
9441 the return value is &%undef%&. In that case, the expansion fails in the same
9442 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
9443 Whatever you return is evaluated in a scalar context. For example, if you
9444 return the name of a Perl vector, the return value is the size of the vector,
9447 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
9448 with the error message that was passed to &%die%&. More details of the embedded
9449 Perl facility are given in chapter &<<CHAPperl>>&.
9451 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
9452 out the use of this expansion item in filter files.
9455 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
9456 .cindex "&%prvs%& expansion item"
9457 The first argument is a complete email address and the second is secret
9458 keystring. The third argument, specifying a key number, is optional. If absent,
9459 it defaults to 0. The result of the expansion is a prvs-signed email address,
9460 to be typically used with the &%return_path%& option on an &(smtp)& transport
9461 as part of a bounce address tag validation (BATV) scheme. For more discussion
9462 and an example, see section &<<SECTverifyPRVS>>&.
9464 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
9465 {*&<&'string'&>&*}}*&"
9466 .cindex "&%prvscheck%& expansion item"
9467 This expansion item is the complement of the &%prvs%& item. It is used for
9468 checking prvs-signed addresses. If the expansion of the first argument does not
9469 yield a syntactically valid prvs-signed address, the whole item expands to the
9470 empty string. When the first argument does expand to a syntactically valid
9471 prvs-signed address, the second argument is expanded, with the prvs-decoded
9472 version of the address and the key number extracted from the address in the
9473 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
9475 These two variables can be used in the expansion of the second argument to
9476 retrieve the secret. The validity of the prvs-signed address is then checked
9477 against the secret. The result is stored in the variable &$prvscheck_result$&,
9478 which is empty for failure or &"1"& for success.
9480 The third argument is optional; if it is missing, it defaults to an empty
9481 string. This argument is now expanded. If the result is an empty string, the
9482 result of the expansion is the decoded version of the address. This is the case
9483 whether or not the signature was valid. Otherwise, the result of the expansion
9484 is the expansion of the third argument.
9486 All three variables can be used in the expansion of the third argument.
9487 However, once the expansion is complete, only &$prvscheck_result$& remains set.
9488 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
9490 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
9491 .cindex "expansion" "inserting an entire file"
9492 .cindex "file" "inserting into expansion"
9493 .cindex "&%readfile%& expansion item"
9494 The file name and end-of-line string are first expanded separately. The file is
9495 then read, and its contents replace the entire item. All newline characters in
9496 the file are replaced by the end-of-line string if it is present. Otherwise,
9497 newlines are left in the string.
9498 String expansion is not applied to the contents of the file. If you want this,
9499 you must wrap the item in an &%expand%& operator. If the file cannot be read,
9500 the string expansion fails.
9502 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
9503 locks out the use of this expansion item in filter files.
9507 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
9508 {*&<&'timeout'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
9509 .cindex "expansion" "inserting from a socket"
9510 .cindex "socket, use of in expansion"
9511 .cindex "&%readsocket%& expansion item"
9512 This item inserts data from a Unix domain or Internet socket into the expanded
9513 string. The minimal way of using it uses just two arguments, as in these
9516 ${readsocket{/socket/name}{request string}}
9517 ${readsocket{inet:some.host:1234}{request string}}
9519 For a Unix domain socket, the first substring must be the path to the socket.
9520 For an Internet socket, the first substring must contain &`inet:`& followed by
9521 a host name or IP address, followed by a colon and a port, which can be a
9522 number or the name of a TCP port in &_/etc/services_&. An IP address may
9523 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
9526 ${readsocket{inet:[::1]:1234}{request string}}
9528 Only a single host name may be given, but if looking it up yields more than
9529 one IP address, they are each tried in turn until a connection is made. For
9530 both kinds of socket, Exim makes a connection, writes the request string
9531 (unless it is an empty string) and reads from the socket until an end-of-file
9532 is read. A timeout of 5 seconds is applied. Additional, optional arguments
9533 extend what can be done. Firstly, you can vary the timeout. For example:
9535 ${readsocket{/socket/name}{request string}{3s}}
9537 A fourth argument allows you to change any newlines that are in the data
9538 that is read, in the same way as for &%readfile%& (see above). This example
9539 turns them into spaces:
9541 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
9543 As with all expansions, the substrings are expanded before the processing
9544 happens. Errors in these sub-expansions cause the expansion to fail. In
9545 addition, the following errors can occur:
9548 Failure to create a socket file descriptor;
9550 Failure to connect the socket;
9552 Failure to write the request string;
9554 Timeout on reading from the socket.
9557 By default, any of these errors causes the expansion to fail. However, if
9558 you supply a fifth substring, it is expanded and used when any of the above
9559 errors occurs. For example:
9561 ${readsocket{/socket/name}{request string}{3s}{\n}\
9564 You can test for the existence of a Unix domain socket by wrapping this
9565 expansion in &`${if exists`&, but there is a race condition between that test
9566 and the actual opening of the socket, so it is safer to use the fifth argument
9567 if you want to be absolutely sure of avoiding an expansion error for a
9568 non-existent Unix domain socket, or a failure to connect to an Internet socket.
9570 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
9571 locks out the use of this expansion item in filter files.
9574 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9575 .cindex "expansion" "reducing a list to a scalar"
9576 .cindex "list" "reducing to a scalar"
9579 This operation reduces a list to a single, scalar string. After expansion,
9580 <&'string1'&> is interpreted as a list, colon-separated by default, but the
9581 separator can be changed in the usual way. Then <&'string2'&> is expanded and
9582 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
9583 list is assigned to &$item$& in turn, and <&'string3'&> is expanded for each of
9584 them. The result of that expansion is assigned to &$value$& before the next
9585 iteration. When the end of the list is reached, the final value of &$value$& is
9586 added to the expansion output. The &*reduce*& expansion item can be used in a
9587 number of ways. For example, to add up a list of numbers:
9589 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
9591 The result of that expansion would be &`6`&. The maximum of a list of numbers
9594 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
9596 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
9597 restored to what they were before. See also the &*filter*& and &*map*&
9600 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
9601 This item inserts &"raw"& header lines. It is described with the &%header%&
9602 expansion item above.
9604 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
9605 {*&<&'string2'&>&*}}*&"
9606 .cindex "expansion" "running a command"
9607 .cindex "&%run%& expansion item"
9608 The command and its arguments are first expanded as one string. The string is
9609 split apart into individual arguments by spaces, and then the command is run
9610 in a separate process, but under the same uid and gid. As in other command
9611 executions from Exim, a shell is not used by default. If the command requires
9612 a shell, you must explicitly code it.
9614 Since the arguments are split by spaces, when there is a variable expansion
9615 which has an empty result, it will cause the situation that the argument will
9616 simply be omitted when the program is actually executed by Exim. If the
9617 script/program requires a specific number of arguments and the expanded
9618 variable could possibly result in this empty expansion, the variable must be
9619 quoted. This is more difficult if the expanded variable itself could result
9620 in a string containing quotes, because it would interfere with the quotes
9621 around the command arguments. A possible guard against this is to wrap the
9622 variable in the &%sg%& operator to change any quote marks to some other
9625 The standard input for the command exists, but is empty. The standard output
9626 and standard error are set to the same file descriptor.
9627 .cindex "return code" "from &%run%& expansion"
9629 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
9630 and replaces the entire item; during this expansion, the standard output/error
9631 from the command is in the variable &$value$&. If the command fails,
9632 <&'string2'&>, if present, is expanded and used. Once again, during the
9633 expansion, the standard output/error from the command is in the variable
9636 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
9637 can be the word &"fail"& (not in braces) to force expansion failure if the
9638 command does not succeed. If both strings are omitted, the result is contents
9639 of the standard output/error on success, and nothing on failure.
9641 .vindex "&$run_in_acl$&"
9642 The standard output/error of the command is put in the variable &$value$&.
9643 In this ACL example, the output of a command is logged for the admin to
9646 warn condition = ${run{/usr/bin/id}{yes}{no}}
9647 log_message = Output of id: $value
9649 If the command requires shell idioms, such as the > redirect operator, the
9650 shell must be invoked directly, such as with:
9652 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
9656 The return code from the command is put in the variable &$runrc$&, and this
9657 remains set afterwards, so in a filter file you can do things like this:
9659 if "${run{x y z}{}}$runrc" is 1 then ...
9660 elif $runrc is 2 then ...
9664 If execution of the command fails (for example, the command does not exist),
9665 the return code is 127 &-- the same code that shells use for non-existent
9668 &*Warning*&: In a router or transport, you cannot assume the order in which
9669 option values are expanded, except for those preconditions whose order of
9670 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
9671 by the expansion of one option, and use it in another.
9673 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
9674 out the use of this expansion item in filter files.
9677 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
9678 .cindex "expansion" "string substitution"
9679 .cindex "&%sg%& expansion item"
9680 This item works like Perl's substitution operator (s) with the global (/g)
9681 option; hence its name. However, unlike the Perl equivalent, Exim does not
9682 modify the subject string; instead it returns the modified string for insertion
9683 into the overall expansion. The item takes three arguments: the subject string,
9684 a regular expression, and a substitution string. For example:
9686 ${sg{abcdefabcdef}{abc}{xyz}}
9688 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
9689 if any $ or \ characters are required in the regular expression or in the
9690 substitution string, they have to be escaped. For example:
9692 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
9694 yields &"defabc"&, and
9696 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
9698 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
9699 the regular expression from string expansion.
9704 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
9705 .cindex sorting a list
9706 .cindex list sorting
9707 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9708 default, but the separator can be changed in the usual way.
9709 The <&'comparator'&> argument is interpreted as the operator
9710 of a two-argument expansion condition.
9711 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
9712 The comparison should return true when applied to two values
9713 if the first value should sort before the second value.
9714 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
9715 the element being placed in &$item$&,
9716 to give values for comparison.
9718 The item result is a sorted list,
9719 with the original list separator,
9720 of the list elements (in full) of the original.
9724 ${sort{3:2:1:4}{<}{$item}}
9726 sorts a list of numbers, and
9728 ${sort {$lookup dnsdb{>:,,mx=example.com}} {<} {${listextract{1}{<,$item}}}}
9730 will sort an MX lookup into priority order.
9734 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9735 .cindex "&%substr%& expansion item"
9736 .cindex "substring extraction"
9737 .cindex "expansion" "substring extraction"
9738 The three strings are expanded; the first two must yield numbers. Call them
9739 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9740 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9741 can use the simpler operator notation that avoids some of the braces:
9743 ${substr_<n>_<m>:<string>}
9745 The second number is optional (in both notations).
9746 If it is absent in the simpler format, the preceding underscore must also be
9749 The &%substr%& item can be used to extract more general substrings than
9750 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
9751 length required. For example
9753 ${substr{3}{2}{$local_part}}
9755 If the starting offset is greater than the string length the result is the
9756 null string; if the length plus starting offset is greater than the string
9757 length, the result is the right-hand part of the string, starting from the
9758 given offset. The first character in the string has offset zero.
9760 The &%substr%& expansion item can take negative offset values to count
9761 from the right-hand end of its operand. The last character is offset -1, the
9762 second-last is offset -2, and so on. Thus, for example,
9764 ${substr{-5}{2}{1234567}}
9766 yields &"34"&. If the absolute value of a negative offset is greater than the
9767 length of the string, the substring starts at the beginning of the string, and
9768 the length is reduced by the amount of overshoot. Thus, for example,
9770 ${substr{-5}{2}{12}}
9772 yields an empty string, but
9774 ${substr{-3}{2}{12}}
9778 When the second number is omitted from &%substr%&, the remainder of the string
9779 is taken if the offset is positive. If it is negative, all characters in the
9780 string preceding the offset point are taken. For example, an offset of -1 and
9781 no length, as in these semantically identical examples:
9784 ${substr{-1}{abcde}}
9786 yields all but the last character of the string, that is, &"abcd"&.
9790 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
9791 {*&<&'replacements'&>&*}}*&"
9792 .cindex "expansion" "character translation"
9793 .cindex "&%tr%& expansion item"
9794 This item does single-character translation on its subject string. The second
9795 argument is a list of characters to be translated in the subject string. Each
9796 matching character is replaced by the corresponding character from the
9797 replacement list. For example
9799 ${tr{abcdea}{ac}{13}}
9801 yields &`1b3de1`&. If there are duplicates in the second character string, the
9802 last occurrence is used. If the third string is shorter than the second, its
9803 last character is replicated. However, if it is empty, no translation takes
9809 .section "Expansion operators" "SECTexpop"
9810 .cindex "expansion" "operators"
9811 For expansion items that perform transformations on a single argument string,
9812 the &"operator"& notation is used because it is simpler and uses fewer braces.
9813 The substring is first expanded before the operation is applied to it. The
9814 following operations can be performed:
9817 .vitem &*${address:*&<&'string'&>&*}*&
9818 .cindex "expansion" "RFC 2822 address handling"
9819 .cindex "&%address%& expansion item"
9820 The string is interpreted as an RFC 2822 address, as it might appear in a
9821 header line, and the effective address is extracted from it. If the string does
9822 not parse successfully, the result is empty.
9825 .vitem &*${addresses:*&<&'string'&>&*}*&
9826 .cindex "expansion" "RFC 2822 address handling"
9827 .cindex "&%addresses%& expansion item"
9828 The string (after expansion) is interpreted as a list of addresses in RFC
9829 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
9830 operative address (&'local-part@domain'&) is extracted from each item, and the
9831 result of the expansion is a colon-separated list, with appropriate
9832 doubling of colons should any happen to be present in the email addresses.
9833 Syntactically invalid RFC2822 address items are omitted from the output.
9835 It is possible to specify a character other than colon for the output
9836 separator by starting the string with > followed by the new separator
9837 character. For example:
9839 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
9841 expands to &`ceo@up.stairs&&sec@base.ment`&. Compare the &*address*& (singular)
9842 expansion item, which extracts the working address from a single RFC2822
9843 address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
9846 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
9847 a strict interpretation of header line formatting. Exim parses the bare,
9848 unquoted portion of an email address and if it finds a comma, treats it as an
9849 email address seperator. For the example header line:
9851 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
9853 The first example below demonstrates that Q-encoded email addresses are parsed
9854 properly if it is given the raw header (in this example, &`$rheader_from:`&).
9855 It does not see the comma because it's still encoded as "=2C". The second
9856 example below is passed the contents of &`$header_from:`&, meaning it gets
9857 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
9858 The third example shows that the presence of a comma is skipped when it is
9861 # exim -be '${addresses:From: \
9862 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
9864 # exim -be '${addresses:From: Last, First <user@example.com>}'
9865 Last:user@example.com
9866 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
9870 .vitem &*${base62:*&<&'digits'&>&*}*&
9871 .cindex "&%base62%& expansion item"
9872 .cindex "expansion" "conversion to base 62"
9873 The string must consist entirely of decimal digits. The number is converted to
9874 base 62 and output as a string of six characters, including leading zeros. In
9875 the few operating environments where Exim uses base 36 instead of base 62 for
9876 its message identifiers (because those systems do not have case-sensitive file
9877 names), base 36 is used by this operator, despite its name. &*Note*&: Just to
9878 be absolutely clear: this is &'not'& base64 encoding.
9880 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
9881 .cindex "&%base62d%& expansion item"
9882 .cindex "expansion" "conversion to base 62"
9883 The string must consist entirely of base-62 digits, or, in operating
9884 environments where Exim uses base 36 instead of base 62 for its message
9885 identifiers, base-36 digits. The number is converted to decimal and output as a
9889 .vitem &*${domain:*&<&'string'&>&*}*&
9890 .cindex "domain" "extraction"
9891 .cindex "expansion" "domain extraction"
9892 The string is interpreted as an RFC 2822 address and the domain is extracted
9893 from it. If the string does not parse successfully, the result is empty.
9896 .vitem &*${escape:*&<&'string'&>&*}*&
9897 .cindex "expansion" "escaping non-printing characters"
9898 .cindex "&%escape%& expansion item"
9899 If the string contains any non-printing characters, they are converted to
9900 escape sequences starting with a backslash. Whether characters with the most
9901 significant bit set (so-called &"8-bit characters"&) count as printing or not
9902 is controlled by the &%print_topbitchars%& option.
9905 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
9906 .cindex "expansion" "expression evaluation"
9907 .cindex "expansion" "arithmetic expression"
9908 .cindex "&%eval%& expansion item"
9909 These items supports simple arithmetic and bitwise logical operations in
9910 expansion strings. The string (after expansion) must be a conventional
9911 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
9912 logical operators, and parentheses. All operations are carried out using
9913 integer arithmetic. The operator priorities are as follows (the same as in the
9914 C programming language):
9916 .irow &'highest:'& "not (~), negate (-)"
9917 .irow "" "multiply (*), divide (/), remainder (%)"
9918 .irow "" "plus (+), minus (-)"
9919 .irow "" "shift-left (<<), shift-right (>>)"
9922 .irow &'lowest:'& "or (|)"
9924 Binary operators with the same priority are evaluated from left to right. White
9925 space is permitted before or after operators.
9927 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
9928 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
9929 decimal, even if they start with a leading zero; hexadecimal numbers are not
9930 permitted. This can be useful when processing numbers extracted from dates or
9931 times, which often do have leading zeros.
9933 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
9935 respectively. Negative numbers are supported. The result of the computation is
9936 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
9939 &`${eval:1+1} `& yields 2
9940 &`${eval:1+2*3} `& yields 7
9941 &`${eval:(1+2)*3} `& yields 9
9942 &`${eval:2+42%5} `& yields 4
9943 &`${eval:0xc&5} `& yields 4
9944 &`${eval:0xc|5} `& yields 13
9945 &`${eval:0xc^5} `& yields 9
9946 &`${eval:0xc>>1} `& yields 6
9947 &`${eval:0xc<<1} `& yields 24
9948 &`${eval:~255&0x1234} `& yields 4608
9949 &`${eval:-(~255&0x1234)} `& yields -4608
9952 As a more realistic example, in an ACL you might have
9954 deny message = Too many bad recipients
9957 {>{$rcpt_count}{10}} \
9960 {$recipients_count} \
9961 {${eval:$rcpt_count/2}} \
9965 The condition is true if there have been more than 10 RCPT commands and
9966 fewer than half of them have resulted in a valid recipient.
9969 .vitem &*${expand:*&<&'string'&>&*}*&
9970 .cindex "expansion" "re-expansion of substring"
9971 The &%expand%& operator causes a string to be expanded for a second time. For
9974 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
9976 first looks up a string in a file while expanding the operand for &%expand%&,
9977 and then re-expands what it has found.
9980 .vitem &*${from_utf8:*&<&'string'&>&*}*&
9982 .cindex "UTF-8" "conversion from"
9983 .cindex "expansion" "UTF-8 conversion"
9984 .cindex "&%from_utf8%& expansion item"
9985 The world is slowly moving towards Unicode, although there are no standards for
9986 email yet. However, other applications (including some databases) are starting
9987 to store data in Unicode, using UTF-8 encoding. This operator converts from a
9988 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
9989 converted to underscores. The input must be a valid UTF-8 string. If it is not,
9990 the result is an undefined sequence of bytes.
9992 Unicode code points with values less than 256 are compatible with ASCII and
9993 ISO-8859-1 (also known as Latin-1).
9994 For example, character 169 is the copyright symbol in both cases, though the
9995 way it is encoded is different. In UTF-8, more than one byte is needed for
9996 characters with code values greater than 127, whereas ISO-8859-1 is a
9997 single-byte encoding (but thereby limited to 256 characters). This makes
9998 translation from UTF-8 to ISO-8859-1 straightforward.
10001 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10002 .cindex "hash function" "textual"
10003 .cindex "expansion" "textual hash"
10004 The &%hash%& operator is a simpler interface to the hashing function that can
10005 be used when the two parameters are fixed numbers (as opposed to strings that
10006 change when expanded). The effect is the same as
10008 ${hash{<n>}{<m>}{<string>}}
10010 See the description of the general &%hash%& item above for details. The
10011 abbreviation &%h%& can be used when &%hash%& is used as an operator.
10015 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
10016 .cindex "base64 encoding" "conversion from hex"
10017 .cindex "expansion" "hex to base64"
10018 .cindex "&%hex2b64%& expansion item"
10019 This operator converts a hex string into one that is base64 encoded. This can
10020 be useful for processing the output of the MD5 and SHA-1 hashing functions.
10024 .vitem &*${hexquote:*&<&'string'&>&*}*&
10025 .cindex "quoting" "hex-encoded unprintable characters"
10026 .cindex "&%hexquote%& expansion item"
10027 This operator converts non-printable characters in a string into a hex
10028 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
10029 as is, and other byte values are converted to &`\xNN`&, for example a
10030 byte value 127 is converted to &`\x7f`&.
10033 .vitem &*${lc:*&<&'string'&>&*}*&
10034 .cindex "case forcing in strings"
10035 .cindex "string" "case forcing"
10036 .cindex "lower casing"
10037 .cindex "expansion" "case forcing"
10038 .cindex "&%lc%& expansion item"
10039 This forces the letters in the string into lower-case, for example:
10044 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
10045 .cindex "expansion" "string truncation"
10046 .cindex "&%length%& expansion item"
10047 The &%length%& operator is a simpler interface to the &%length%& function that
10048 can be used when the parameter is a fixed number (as opposed to a string that
10049 changes when expanded). The effect is the same as
10051 ${length{<number>}{<string>}}
10053 See the description of the general &%length%& item above for details. Note that
10054 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
10055 when &%length%& is used as an operator.
10058 .vitem &*${listcount:*&<&'string'&>&*}*&
10059 .cindex "expansion" "list item count"
10060 .cindex "list" "item count"
10061 .cindex "list" "count of items"
10062 .cindex "&%listcount%& expansion item"
10063 The string is interpreted as a list and the number of items is returned.
10066 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
10067 .cindex "expansion" "named list"
10068 .cindex "&%listnamed%& expansion item"
10069 The name is interpreted as a named list and the content of the list is returned,
10070 expanding any referenced lists, re-quoting as needed for colon-separation.
10071 If the optional type is given it must be one of "a", "d", "h" or "l"
10072 and selects address-, domain-, host- or localpart- lists to search among respectively.
10073 Otherwise all types are searched in an undefined order and the first
10074 matching list is returned.
10077 .vitem &*${local_part:*&<&'string'&>&*}*&
10078 .cindex "expansion" "local part extraction"
10079 .cindex "&%local_part%& expansion item"
10080 The string is interpreted as an RFC 2822 address and the local part is
10081 extracted from it. If the string does not parse successfully, the result is
10085 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
10086 .cindex "masked IP address"
10087 .cindex "IP address" "masking"
10088 .cindex "CIDR notation"
10089 .cindex "expansion" "IP address masking"
10090 .cindex "&%mask%& expansion item"
10091 If the form of the string to be operated on is not an IP address followed by a
10092 slash and an integer (that is, a network address in CIDR notation), the
10093 expansion fails. Otherwise, this operator converts the IP address to binary,
10094 masks off the least significant bits according to the bit count, and converts
10095 the result back to text, with mask appended. For example,
10097 ${mask:10.111.131.206/28}
10099 returns the string &"10.111.131.192/28"&. Since this operation is expected to
10100 be mostly used for looking up masked addresses in files, the result for an IPv6
10101 address uses dots to separate components instead of colons, because colon
10102 terminates a key string in lsearch files. So, for example,
10104 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
10108 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
10110 Letters in IPv6 addresses are always output in lower case.
10113 .vitem &*${md5:*&<&'string'&>&*}*&
10115 .cindex "expansion" "MD5 hash"
10116 .cindex "certificate fingerprint"
10117 .cindex "&%md5%& expansion item"
10118 The &%md5%& operator computes the MD5 hash value of the string, and returns it
10119 as a 32-digit hexadecimal number, in which any letters are in lower case.
10122 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10123 .cindex "expansion" "numeric hash"
10124 .cindex "hash function" "numeric"
10125 The &%nhash%& operator is a simpler interface to the numeric hashing function
10126 that can be used when the two parameters are fixed numbers (as opposed to
10127 strings that change when expanded). The effect is the same as
10129 ${nhash{<n>}{<m>}{<string>}}
10131 See the description of the general &%nhash%& item above for details.
10134 .vitem &*${quote:*&<&'string'&>&*}*&
10135 .cindex "quoting" "in string expansions"
10136 .cindex "expansion" "quoting"
10137 .cindex "&%quote%& expansion item"
10138 The &%quote%& operator puts its argument into double quotes if it
10139 is an empty string or
10140 contains anything other than letters, digits, underscores, dots, and hyphens.
10141 Any occurrences of double quotes and backslashes are escaped with a backslash.
10142 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
10143 respectively For example,
10151 The place where this is useful is when the argument is a substitution from a
10152 variable or a message header.
10154 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
10155 .cindex "&%quote_local_part%& expansion item"
10156 This operator is like &%quote%&, except that it quotes the string only if
10157 required to do so by the rules of RFC 2822 for quoting local parts. For
10158 example, a plus sign would not cause quoting (but it would for &%quote%&).
10159 If you are creating a new email address from the contents of &$local_part$&
10160 (or any other unknown data), you should always use this operator.
10163 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
10164 .cindex "quoting" "lookup-specific"
10165 This operator applies lookup-specific quoting rules to the string. Each
10166 query-style lookup type has its own quoting rules which are described with
10167 the lookups in chapter &<<CHAPfdlookup>>&. For example,
10169 ${quote_ldap:two * two}
10175 For single-key lookup types, no quoting is ever necessary and this operator
10176 yields an unchanged string.
10179 .vitem &*${randint:*&<&'n'&>&*}*&
10180 .cindex "random number"
10181 This operator returns a somewhat random number which is less than the
10182 supplied number and is at least 0. The quality of this randomness depends
10183 on how Exim was built; the values are not suitable for keying material.
10184 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
10185 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
10186 for versions of GnuTLS with that function.
10187 Otherwise, the implementation may be arc4random(), random() seeded by
10188 srandomdev() or srandom(), or a custom implementation even weaker than
10192 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
10193 .cindex "expansion" "IP address"
10194 This operator reverses an IP address; for IPv4 addresses, the result is in
10195 dotted-quad decimal form, while for IPv6 addreses the result is in
10196 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
10197 for DNS. For example,
10199 ${reverse_ip:192.0.2.4}
10200 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
10205 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
10209 .vitem &*${rfc2047:*&<&'string'&>&*}*&
10210 .cindex "expansion" "RFC 2047"
10211 .cindex "RFC 2047" "expansion operator"
10212 .cindex "&%rfc2047%& expansion item"
10213 This operator encodes text according to the rules of RFC 2047. This is an
10214 encoding that is used in header lines to encode non-ASCII characters. It is
10215 assumed that the input string is in the encoding specified by the
10216 &%headers_charset%& option, which defaults to ISO-8859-1. If the string
10217 contains only characters in the range 33&--126, and no instances of the
10220 ? = ( ) < > @ , ; : \ " . [ ] _
10222 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
10223 string, using as many &"encoded words"& as necessary to encode all the
10227 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
10228 .cindex "expansion" "RFC 2047"
10229 .cindex "RFC 2047" "decoding"
10230 .cindex "&%rfc2047d%& expansion item"
10231 This operator decodes strings that are encoded as per RFC 2047. Binary zero
10232 bytes are replaced by question marks. Characters are converted into the
10233 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
10234 not recognized unless &%check_rfc2047_length%& is set false.
10236 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
10237 access a header line, RFC 2047 decoding is done automatically. You do not need
10238 to use this operator as well.
10242 .vitem &*${rxquote:*&<&'string'&>&*}*&
10243 .cindex "quoting" "in regular expressions"
10244 .cindex "regular expressions" "quoting"
10245 .cindex "&%rxquote%& expansion item"
10246 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
10247 characters in its argument. This is useful when substituting the values of
10248 variables or headers inside regular expressions.
10251 .vitem &*${sha1:*&<&'string'&>&*}*&
10252 .cindex "SHA-1 hash"
10253 .cindex "expansion" "SHA-1 hashing"
10254 .cindex "certificate fingerprint"
10255 .cindex "&%sha2%& expansion item"
10256 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
10257 it as a 40-digit hexadecimal number, in which any letters are in upper case.
10260 .vitem &*${sha256:*&<&'certificate'&>&*}*&
10261 .cindex "SHA-256 hash"
10262 .cindex "certificate fingerprint"
10263 .cindex "expansion" "SHA-256 hashing"
10264 .cindex "&%sha256%& expansion item"
10265 The &%sha256%& operator computes the SHA-256 hash fingerprint of the
10268 it as a 64-digit hexadecimal number, in which any letters are in upper case.
10269 Only arguments which are a single variable of certificate type are supported.
10272 .vitem &*${stat:*&<&'string'&>&*}*&
10273 .cindex "expansion" "statting a file"
10274 .cindex "file" "extracting characteristics"
10275 .cindex "&%stat%& expansion item"
10276 The string, after expansion, must be a file path. A call to the &[stat()]&
10277 function is made for this path. If &[stat()]& fails, an error occurs and the
10278 expansion fails. If it succeeds, the data from the stat replaces the item, as a
10279 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
10280 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
10281 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
10282 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
10283 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
10284 can extract individual fields using the &%extract%& expansion item.
10286 The use of the &%stat%& expansion in users' filter files can be locked out by
10287 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
10288 systems for files larger than 2GB.
10290 .vitem &*${str2b64:*&<&'string'&>&*}*&
10291 .cindex "expansion" "base64 encoding"
10292 .cindex "base64 encoding" "in string expansion"
10293 .cindex "&%str2b64%& expansion item"
10294 This operator converts a string into one that is base64 encoded.
10298 .vitem &*${strlen:*&<&'string'&>&*}*&
10299 .cindex "expansion" "string length"
10300 .cindex "string" "length in expansion"
10301 .cindex "&%strlen%& expansion item"
10302 The item is replace by the length of the expanded string, expressed as a
10303 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
10306 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
10307 .cindex "&%substr%& expansion item"
10308 .cindex "substring extraction"
10309 .cindex "expansion" "substring expansion"
10310 The &%substr%& operator is a simpler interface to the &%substr%& function that
10311 can be used when the two parameters are fixed numbers (as opposed to strings
10312 that change when expanded). The effect is the same as
10314 ${substr{<start>}{<length>}{<string>}}
10316 See the description of the general &%substr%& item above for details. The
10317 abbreviation &%s%& can be used when &%substr%& is used as an operator.
10319 .vitem &*${time_eval:*&<&'string'&>&*}*&
10320 .cindex "&%time_eval%& expansion item"
10321 .cindex "time interval" "decoding"
10322 This item converts an Exim time interval such as &`2d4h5m`& into a number of
10325 .vitem &*${time_interval:*&<&'string'&>&*}*&
10326 .cindex "&%time_interval%& expansion item"
10327 .cindex "time interval" "formatting"
10328 The argument (after sub-expansion) must be a sequence of decimal digits that
10329 represents an interval of time as a number of seconds. It is converted into a
10330 number of larger units and output in Exim's normal time format, for example,
10333 .vitem &*${uc:*&<&'string'&>&*}*&
10334 .cindex "case forcing in strings"
10335 .cindex "string" "case forcing"
10336 .cindex "upper casing"
10337 .cindex "expansion" "case forcing"
10338 .cindex "&%uc%& expansion item"
10339 This forces the letters in the string into upper-case.
10341 .vitem &*${utf8clean:*&<&'string'&>&*}*&
10342 .cindex "correction of invalid utf-8 sequences in strings"
10343 .cindex "utf-8" "utf-8 sequences"
10344 .cindex "incorrect utf-8"
10345 .cindex "expansion" "utf-8 forcing"
10346 .cindex "&%utf8clean%& expansion item"
10347 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
10355 .section "Expansion conditions" "SECTexpcond"
10356 .scindex IIDexpcond "expansion" "conditions"
10357 The following conditions are available for testing by the &%${if%& construct
10358 while expanding strings:
10361 .vitem &*!*&<&'condition'&>
10362 .cindex "expansion" "negating a condition"
10363 .cindex "negation" "in expansion condition"
10364 Preceding any condition with an exclamation mark negates the result of the
10367 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10368 .cindex "numeric comparison"
10369 .cindex "expansion" "numeric comparison"
10370 There are a number of symbolic operators for doing numeric comparisons. They
10376 &`>= `& greater or equal
10378 &`<= `& less or equal
10382 ${if >{$message_size}{10M} ...
10384 Note that the general negation operator provides for inequality testing. The
10385 two strings must take the form of optionally signed decimal integers,
10386 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
10387 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
10388 As a special case, the numerical value of an empty string is taken as
10391 In all cases, a relative comparator OP is testing if <&'string1'&> OP
10392 <&'string2'&>; the above example is checking if &$message_size$& is larger than
10393 10M, not if 10M is larger than &$message_size$&.
10396 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
10397 {*&<&'arg2'&>&*}...}*&
10398 .cindex "expansion" "calling an acl"
10399 .cindex "&%acl%&" "expansion condition"
10400 The name and zero to nine argument strings are first expanded separately. The expanded
10401 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
10402 Any unused are made empty. The variable &$acl_narg$& is set to the number of
10403 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
10404 and may use the variables; if another acl expansion is used the values
10405 are restored after it returns. If the ACL sets
10406 a value using a "message =" modifier the variable $value becomes
10407 the result of the expansion, otherwise it is empty.
10408 If the ACL returns accept the condition is true; if deny, false.
10409 If the ACL returns defer the result is a forced-fail.
10411 .vitem &*bool&~{*&<&'string'&>&*}*&
10412 .cindex "expansion" "boolean parsing"
10413 .cindex "&%bool%& expansion condition"
10414 This condition turns a string holding a true or false representation into
10415 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
10416 (case-insensitively); also integer numbers map to true if non-zero,
10418 An empty string is treated as false.
10419 Leading and trailing whitespace is ignored;
10420 thus a string consisting only of whitespace is false.
10421 All other string values will result in expansion failure.
10423 When combined with ACL variables, this expansion condition will let you
10424 make decisions in one place and act on those decisions in another place.
10427 ${if bool{$acl_m_privileged_sender} ...
10431 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
10432 .cindex "expansion" "boolean parsing"
10433 .cindex "&%bool_lax%& expansion condition"
10434 Like &%bool%&, this condition turns a string into a boolean state. But
10435 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
10436 loose definition that the Router &%condition%& option uses. The empty string
10437 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
10438 true. Leading and trailing whitespace is ignored.
10440 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
10442 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10443 .cindex "expansion" "encrypted comparison"
10444 .cindex "encrypted strings, comparing"
10445 .cindex "&%crypteq%& expansion condition"
10446 This condition is included in the Exim binary if it is built to support any
10447 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
10448 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
10449 included in the binary.
10451 The &%crypteq%& condition has two arguments. The first is encrypted and
10452 compared against the second, which is already encrypted. The second string may
10453 be in the LDAP form for storing encrypted strings, which starts with the
10454 encryption type in curly brackets, followed by the data. If the second string
10455 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
10456 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
10457 Typically this will be a field from a password file. An example of an encrypted
10458 string in LDAP form is:
10460 {md5}CY9rzUYh03PK3k6DJie09g==
10462 If such a string appears directly in an expansion, the curly brackets have to
10463 be quoted, because they are part of the expansion syntax. For example:
10465 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
10467 The following encryption types (whose names are matched case-independently) are
10472 .cindex "base64 encoding" "in encrypted password"
10473 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
10474 printable characters to compare with the remainder of the second string. If the
10475 length of the comparison string is 24, Exim assumes that it is base64 encoded
10476 (as in the above example). If the length is 32, Exim assumes that it is a
10477 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
10481 .cindex "SHA-1 hash"
10482 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
10483 printable characters to compare with the remainder of the second string. If the
10484 length of the comparison string is 28, Exim assumes that it is base64 encoded.
10485 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
10486 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
10489 .cindex "&[crypt()]&"
10490 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
10491 only the first eight characters of the password. However, in modern operating
10492 systems this is no longer true, and in many cases the entire password is used,
10493 whatever its length.
10496 .cindex "&[crypt16()]&"
10497 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
10498 use up to 16 characters of the password in some operating systems. Again, in
10499 modern operating systems, more characters may be used.
10501 Exim has its own version of &[crypt16()]&, which is just a double call to
10502 &[crypt()]&. For operating systems that have their own version, setting
10503 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
10504 operating system version instead of its own. This option is set by default in
10505 the OS-dependent &_Makefile_& for those operating systems that are known to
10506 support &[crypt16()]&.
10508 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
10509 it was not using the same algorithm as some operating systems' versions. It
10510 turns out that as well as &[crypt16()]& there is a function called
10511 &[bigcrypt()]& in some operating systems. This may or may not use the same
10512 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
10514 However, since there is now a move away from the traditional &[crypt()]&
10515 functions towards using SHA1 and other algorithms, tidying up this area of
10516 Exim is seen as very low priority.
10518 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
10519 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
10520 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
10521 default is &`{crypt}`&. Whatever the default, you can always use either
10522 function by specifying it explicitly in curly brackets.
10524 .vitem &*def:*&<&'variable&~name'&>
10525 .cindex "expansion" "checking for empty variable"
10526 .cindex "&%def%& expansion condition"
10527 The &%def%& condition must be followed by the name of one of the expansion
10528 variables defined in section &<<SECTexpvar>>&. The condition is true if the
10529 variable does not contain the empty string. For example:
10531 ${if def:sender_ident {from $sender_ident}}
10533 Note that the variable name is given without a leading &%$%& character. If the
10534 variable does not exist, the expansion fails.
10536 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
10537 &~&*def:h_*&<&'header&~name'&>&*:*&"
10538 .cindex "expansion" "checking header line existence"
10539 This condition is true if a message is being processed and the named header
10540 exists in the message. For example,
10542 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
10544 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
10545 the header name must be terminated by a colon if white space does not follow.
10547 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10548 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10549 .cindex "string" "comparison"
10550 .cindex "expansion" "string comparison"
10551 .cindex "&%eq%& expansion condition"
10552 .cindex "&%eqi%& expansion condition"
10553 The two substrings are first expanded. The condition is true if the two
10554 resulting strings are identical. For &%eq%& the comparison includes the case of
10555 letters, whereas for &%eqi%& the comparison is case-independent.
10557 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
10558 .cindex "expansion" "file existence test"
10559 .cindex "file" "existence test"
10560 .cindex "&%exists%&, expansion condition"
10561 The substring is first expanded and then interpreted as an absolute path. The
10562 condition is true if the named file (or directory) exists. The existence test
10563 is done by calling the &[stat()]& function. The use of the &%exists%& test in
10564 users' filter files may be locked out by the system administrator.
10566 .vitem &*first_delivery*&
10567 .cindex "delivery" "first"
10568 .cindex "first delivery"
10569 .cindex "expansion" "first delivery test"
10570 .cindex "&%first_delivery%& expansion condition"
10571 This condition, which has no data, is true during a message's first delivery
10572 attempt. It is false during any subsequent delivery attempts.
10575 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
10576 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
10577 .cindex "list" "iterative conditions"
10578 .cindex "expansion" "&*forall*& condition"
10579 .cindex "expansion" "&*forany*& condition"
10581 These conditions iterate over a list. The first argument is expanded to form
10582 the list. By default, the list separator is a colon, but it can be changed by
10583 the normal method. The second argument is interpreted as a condition that is to
10584 be applied to each item in the list in turn. During the interpretation of the
10585 condition, the current list item is placed in a variable called &$item$&.
10587 For &*forany*&, interpretation stops if the condition is true for any item, and
10588 the result of the whole condition is true. If the condition is false for all
10589 items in the list, the overall condition is false.
10591 For &*forall*&, interpretation stops if the condition is false for any item,
10592 and the result of the whole condition is false. If the condition is true for
10593 all items in the list, the overall condition is true.
10595 Note that negation of &*forany*& means that the condition must be false for all
10596 items for the overall condition to succeed, and negation of &*forall*& means
10597 that the condition must be false for at least one item. In this example, the
10598 list separator is changed to a comma:
10600 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
10602 The value of &$item$& is saved and restored while &*forany*& or &*forall*& is
10603 being processed, to enable these expansion items to be nested.
10605 To scan a named list, expand it with the &*listnamed*& operator.
10608 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10609 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10610 .cindex "string" "comparison"
10611 .cindex "expansion" "string comparison"
10612 .cindex "&%ge%& expansion condition"
10613 .cindex "&%gei%& expansion condition"
10614 The two substrings are first expanded. The condition is true if the first
10615 string is lexically greater than or equal to the second string. For &%ge%& the
10616 comparison includes the case of letters, whereas for &%gei%& the comparison is
10619 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10620 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10621 .cindex "string" "comparison"
10622 .cindex "expansion" "string comparison"
10623 .cindex "&%gt%& expansion condition"
10624 .cindex "&%gti%& expansion condition"
10625 The two substrings are first expanded. The condition is true if the first
10626 string is lexically greater than the second string. For &%gt%& the comparison
10627 includes the case of letters, whereas for &%gti%& the comparison is
10630 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10631 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10632 .cindex "string" "comparison"
10633 .cindex "list" "iterative conditions"
10634 Both strings are expanded; the second string is treated as a list of simple
10635 strings; if the first string is a member of the second, then the condition
10638 These are simpler to use versions of the more powerful &*forany*& condition.
10639 Examples, and the &*forany*& equivalents:
10641 ${if inlist{needle}{foo:needle:bar}}
10642 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
10643 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
10644 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
10647 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
10648 &*isip4&~{*&<&'string'&>&*}*& &&&
10649 &*isip6&~{*&<&'string'&>&*}*&
10650 .cindex "IP address" "testing string format"
10651 .cindex "string" "testing for IP address"
10652 .cindex "&%isip%& expansion condition"
10653 .cindex "&%isip4%& expansion condition"
10654 .cindex "&%isip6%& expansion condition"
10655 The substring is first expanded, and then tested to see if it has the form of
10656 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
10657 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
10659 For an IPv4 address, the test is for four dot-separated components, each of
10660 which consists of from one to three digits. For an IPv6 address, up to eight
10661 colon-separated components are permitted, each containing from one to four
10662 hexadecimal digits. There may be fewer than eight components if an empty
10663 component (adjacent colons) is present. Only one empty component is permitted.
10665 &*Note*&: The checks are just on the form of the address; actual numerical
10666 values are not considered. Thus, for example, 999.999.999.999 passes the IPv4
10667 check. The main use of these tests is to distinguish between IP addresses and
10668 host names, or between IPv4 and IPv6 addresses. For example, you could use
10670 ${if isip4{$sender_host_address}...
10672 to test which IP version an incoming SMTP connection is using.
10674 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
10675 .cindex "LDAP" "use for authentication"
10676 .cindex "expansion" "LDAP authentication test"
10677 .cindex "&%ldapauth%& expansion condition"
10678 This condition supports user authentication using LDAP. See section
10679 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
10680 queries. For this use, the query must contain a user name and password. The
10681 query itself is not used, and can be empty. The condition is true if the
10682 password is not empty, and the user name and password are accepted by the LDAP
10683 server. An empty password is rejected without calling LDAP because LDAP binds
10684 with an empty password are considered anonymous regardless of the username, and
10685 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
10686 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
10690 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10691 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10692 .cindex "string" "comparison"
10693 .cindex "expansion" "string comparison"
10694 .cindex "&%le%& expansion condition"
10695 .cindex "&%lei%& expansion condition"
10696 The two substrings are first expanded. The condition is true if the first
10697 string is lexically less than or equal to the second string. For &%le%& the
10698 comparison includes the case of letters, whereas for &%lei%& the comparison is
10701 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10702 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10703 .cindex "string" "comparison"
10704 .cindex "expansion" "string comparison"
10705 .cindex "&%lt%& expansion condition"
10706 .cindex "&%lti%& expansion condition"
10707 The two substrings are first expanded. The condition is true if the first
10708 string is lexically less than the second string. For &%lt%& the comparison
10709 includes the case of letters, whereas for &%lti%& the comparison is
10713 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10714 .cindex "expansion" "regular expression comparison"
10715 .cindex "regular expressions" "match in expanded string"
10716 .cindex "&%match%& expansion condition"
10717 The two substrings are first expanded. The second is then treated as a regular
10718 expression and applied to the first. Because of the pre-expansion, if the
10719 regular expression contains dollar, or backslash characters, they must be
10720 escaped. Care must also be taken if the regular expression contains braces
10721 (curly brackets). A closing brace must be escaped so that it is not taken as a
10722 premature termination of <&'string2'&>. The easiest approach is to use the
10723 &`\N`& feature to disable expansion of the regular expression.
10726 ${if match {$local_part}{\N^\d{3}\N} ...
10728 If the whole expansion string is in double quotes, further escaping of
10729 backslashes is also required.
10731 The condition is true if the regular expression match succeeds.
10732 The regular expression is not required to begin with a circumflex
10733 metacharacter, but if there is no circumflex, the expression is not anchored,
10734 and it may match anywhere in the subject, not just at the start. If you want
10735 the pattern to match at the end of the subject, you must include the &`$`&
10736 metacharacter at an appropriate point.
10738 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
10739 At the start of an &%if%& expansion the values of the numeric variable
10740 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
10741 succeeds causes them to be reset to the substrings of that condition and they
10742 will have these values during the expansion of the success string. At the end
10743 of the &%if%& expansion, the previous values are restored. After testing a
10744 combination of conditions using &%or%&, the subsequent values of the numeric
10745 variables are those of the condition that succeeded.
10747 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10748 .cindex "&%match_address%& expansion condition"
10749 See &*match_local_part*&.
10751 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10752 .cindex "&%match_domain%& expansion condition"
10753 See &*match_local_part*&.
10755 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10756 .cindex "&%match_ip%& expansion condition"
10757 This condition matches an IP address to a list of IP address patterns. It must
10758 be followed by two argument strings. The first (after expansion) must be an IP
10759 address or an empty string. The second (not expanded) is a restricted host
10760 list that can match only an IP address, not a host name. For example:
10762 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
10764 The specific types of host list item that are permitted in the list are:
10767 An IP address, optionally with a CIDR mask.
10769 A single asterisk, which matches any IP address.
10771 An empty item, which matches only if the IP address is empty. This could be
10772 useful for testing for a locally submitted message or one from specific hosts
10773 in a single test such as
10774 . ==== As this is a nested list, any displays it contains must be indented
10775 . ==== as otherwise they are too far to the left. This comment applies to
10776 . ==== the use of xmlto plus fop. There's no problem when formatting with
10777 . ==== sdop, with or without the extra indent.
10779 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
10781 where the first item in the list is the empty string.
10783 The item @[] matches any of the local host's interface addresses.
10785 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
10786 even if &`net-`& is not specified. There is never any attempt to turn the IP
10787 address into a host name. The most common type of linear search for
10788 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
10789 masks. For example:
10791 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
10793 It is of course possible to use other kinds of lookup, and in such a case, you
10794 do need to specify the &`net-`& prefix if you want to specify a specific
10795 address mask, for example:
10797 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
10799 However, unless you are combining a &%match_ip%& condition with others, it is
10800 just as easy to use the fact that a lookup is itself a condition, and write:
10802 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
10806 Note that <&'string2'&> is not itself subject to string expansion, unless
10807 Exim was built with the EXPAND_LISTMATCH_RHS option.
10809 Consult section &<<SECThoslispatip>>& for further details of these patterns.
10811 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10812 .cindex "domain list" "in expansion condition"
10813 .cindex "address list" "in expansion condition"
10814 .cindex "local part" "list, in expansion condition"
10815 .cindex "&%match_local_part%& expansion condition"
10816 This condition, together with &%match_address%& and &%match_domain%&, make it
10817 possible to test domain, address, and local part lists within expansions. Each
10818 condition requires two arguments: an item and a list to match. A trivial
10821 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
10823 In each case, the second argument may contain any of the allowable items for a
10824 list of the appropriate type. Also, because the second argument (after
10825 expansion) is a standard form of list, it is possible to refer to a named list.
10826 Thus, you can use conditions like this:
10828 ${if match_domain{$domain}{+local_domains}{...
10830 .cindex "&`+caseful`&"
10831 For address lists, the matching starts off caselessly, but the &`+caseful`&
10832 item can be used, as in all address lists, to cause subsequent items to
10833 have their local parts matched casefully. Domains are always matched
10836 Note that <&'string2'&> is not itself subject to string expansion, unless
10837 Exim was built with the EXPAND_LISTMATCH_RHS option.
10839 &*Note*&: Host lists are &'not'& supported in this way. This is because
10840 hosts have two identities: a name and an IP address, and it is not clear
10841 how to specify cleanly how such a test would work. However, IP addresses can be
10842 matched using &%match_ip%&.
10844 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
10845 .cindex "PAM authentication"
10846 .cindex "AUTH" "with PAM"
10847 .cindex "Solaris" "PAM support"
10848 .cindex "expansion" "PAM authentication test"
10849 .cindex "&%pam%& expansion condition"
10850 &'Pluggable Authentication Modules'&
10851 (&url(http://www.kernel.org/pub/linux/libs/pam/)) are a facility that is
10852 available in the latest releases of Solaris and in some GNU/Linux
10853 distributions. The Exim support, which is intended for use in conjunction with
10854 the SMTP AUTH command, is available only if Exim is compiled with
10858 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
10859 in some releases of GNU/Linux &%-ldl%& is also needed.
10861 The argument string is first expanded, and the result must be a
10862 colon-separated list of strings. Leading and trailing white space is ignored.
10863 The PAM module is initialized with the service name &"exim"& and the user name
10864 taken from the first item in the colon-separated data string (<&'string1'&>).
10865 The remaining items in the data string are passed over in response to requests
10866 from the authentication function. In the simple case there will only be one
10867 request, for a password, so the data consists of just two strings.
10869 There can be problems if any of the strings are permitted to contain colon
10870 characters. In the usual way, these have to be doubled to avoid being taken as
10871 separators. If the data is being inserted from a variable, the &%sg%& expansion
10872 item can be used to double any existing colons. For example, the configuration
10873 of a LOGIN authenticator might contain this setting:
10875 server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
10877 For a PLAIN authenticator you could use:
10879 server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
10881 In some operating systems, PAM authentication can be done only from a process
10882 running as root. Since Exim is running as the Exim user when receiving
10883 messages, this means that PAM cannot be used directly in those systems.
10884 A patched version of the &'pam_unix'& module that comes with the
10885 Linux PAM package is available from &url(http://www.e-admin.de/pam_exim/).
10886 The patched module allows one special uid/gid combination, in addition to root,
10887 to authenticate. If you build the patched module to allow the Exim user and
10888 group, PAM can then be used from an Exim authenticator.
10891 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
10892 .cindex "&'pwcheck'& daemon"
10894 .cindex "expansion" "&'pwcheck'& authentication test"
10895 .cindex "&%pwcheck%& expansion condition"
10896 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
10897 This is one way of making it possible for passwords to be checked by a process
10898 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
10899 deprecated. Its replacement is &'saslauthd'& (see below).
10901 The pwcheck support is not included in Exim by default. You need to specify
10902 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
10903 building Exim. For example:
10905 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
10907 You do not need to install the full Cyrus software suite in order to use
10908 the pwcheck daemon. You can compile and install just the daemon alone
10909 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
10910 access to the &_/var/pwcheck_& directory.
10912 The &%pwcheck%& condition takes one argument, which must be the user name and
10913 password, separated by a colon. For example, in a LOGIN authenticator
10914 configuration, you might have this:
10916 server_condition = ${if pwcheck{$auth1:$auth2}}
10918 Again, for a PLAIN authenticator configuration, this would be:
10920 server_condition = ${if pwcheck{$auth2:$auth3}}
10922 .vitem &*queue_running*&
10923 .cindex "queue runner" "detecting when delivering from"
10924 .cindex "expansion" "queue runner test"
10925 .cindex "&%queue_running%& expansion condition"
10926 This condition, which has no data, is true during delivery attempts that are
10927 initiated by queue runner processes, and false otherwise.
10930 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
10932 .cindex "expansion" "Radius authentication"
10933 .cindex "&%radius%& expansion condition"
10934 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
10935 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
10936 the Radius client configuration file in order to build Exim with Radius
10939 With just that one setting, Exim expects to be linked with the &%radiusclient%&
10940 library, using the original API. If you are using release 0.4.0 or later of
10941 this library, you need to set
10943 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
10945 in &_Local/Makefile_& when building Exim. You can also link Exim with the
10946 &%libradius%& library that comes with FreeBSD. To do this, set
10948 RADIUS_LIB_TYPE=RADLIB
10950 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
10951 You may also have to supply a suitable setting in EXTRALIBS so that the
10952 Radius library can be found when Exim is linked.
10954 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
10955 Radius client library, which calls the Radius server. The condition is true if
10956 the authentication is successful. For example:
10958 server_condition = ${if radius{<arguments>}}
10962 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
10963 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
10964 .cindex "&'saslauthd'& daemon"
10966 .cindex "expansion" "&'saslauthd'& authentication test"
10967 .cindex "&%saslauthd%& expansion condition"
10968 This condition supports user authentication using the Cyrus &'saslauthd'&
10969 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
10970 Using this daemon is one way of making it possible for passwords to be checked
10971 by a process that is not running as root.
10973 The saslauthd support is not included in Exim by default. You need to specify
10974 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
10975 building Exim. For example:
10977 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
10979 You do not need to install the full Cyrus software suite in order to use
10980 the saslauthd daemon. You can compile and install just the daemon alone
10981 from the Cyrus SASL library.
10983 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
10984 two are mandatory. For example:
10986 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
10988 The service and the realm are optional (which is why the arguments are enclosed
10989 in their own set of braces). For details of the meaning of the service and
10990 realm, and how to run the daemon, consult the Cyrus documentation.
10995 .section "Combining expansion conditions" "SECID84"
10996 .cindex "expansion" "combining conditions"
10997 Several conditions can be tested at once by combining them using the &%and%&
10998 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
10999 conditions on their own, and precede their lists of sub-conditions. Each
11000 sub-condition must be enclosed in braces within the overall braces that contain
11001 the list. No repetition of &%if%& is used.
11005 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
11006 .cindex "&""or""& expansion condition"
11007 .cindex "expansion" "&""or""& of conditions"
11008 The sub-conditions are evaluated from left to right. The condition is true if
11009 any one of the sub-conditions is true.
11012 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
11014 When a true sub-condition is found, the following ones are parsed but not
11015 evaluated. If there are several &"match"& sub-conditions the values of the
11016 numeric variables afterwards are taken from the first one that succeeds.
11018 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
11019 .cindex "&""and""& expansion condition"
11020 .cindex "expansion" "&""and""& of conditions"
11021 The sub-conditions are evaluated from left to right. The condition is true if
11022 all of the sub-conditions are true. If there are several &"match"&
11023 sub-conditions, the values of the numeric variables afterwards are taken from
11024 the last one. When a false sub-condition is found, the following ones are
11025 parsed but not evaluated.
11027 .ecindex IIDexpcond
11032 .section "Expansion variables" "SECTexpvar"
11033 .cindex "expansion" "variables, list of"
11034 This section contains an alphabetical list of all the expansion variables. Some
11035 of them are available only when Exim is compiled with specific options such as
11036 support for TLS or the content scanning extension.
11039 .vitem "&$0$&, &$1$&, etc"
11040 .cindex "numerical variables (&$1$& &$2$& etc)"
11041 When a &%match%& expansion condition succeeds, these variables contain the
11042 captured substrings identified by the regular expression during subsequent
11043 processing of the success string of the containing &%if%& expansion item.
11044 However, they do not retain their values afterwards; in fact, their previous
11045 values are restored at the end of processing an &%if%& item. The numerical
11046 variables may also be set externally by some other matching process which
11047 precedes the expansion of the string. For example, the commands available in
11048 Exim filter files include an &%if%& command with its own regular expression
11049 matching condition.
11051 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
11052 Within an acl condition, expansion condition or expansion item
11053 any arguments are copied to these variables,
11054 any unused variables being made empty.
11056 .vitem "&$acl_c...$&"
11057 Values can be placed in these variables by the &%set%& modifier in an ACL. They
11058 can be given any name that starts with &$acl_c$& and is at least six characters
11059 long, but the sixth character must be either a digit or an underscore. For
11060 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
11061 variables persist throughout the lifetime of an SMTP connection. They can be
11062 used to pass information between ACLs and between different invocations of the
11063 same ACL. When a message is received, the values of these variables are saved
11064 with the message, and can be accessed by filters, routers, and transports
11065 during subsequent delivery.
11067 .vitem "&$acl_m...$&"
11068 These variables are like the &$acl_c...$& variables, except that their values
11069 are reset after a message has been received. Thus, if several messages are
11070 received in one SMTP connection, &$acl_m...$& values are not passed on from one
11071 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
11072 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
11073 message is received, the values of these variables are saved with the message,
11074 and can be accessed by filters, routers, and transports during subsequent
11077 .vitem &$acl_narg$&
11078 Within an acl condition, expansion condition or expansion item
11079 this variable has the number of arguments.
11081 .vitem &$acl_verify_message$&
11082 .vindex "&$acl_verify_message$&"
11083 After an address verification has failed, this variable contains the failure
11084 message. It retains its value for use in subsequent modifiers. The message can
11085 be preserved by coding like this:
11087 warn !verify = sender
11088 set acl_m0 = $acl_verify_message
11090 You can use &$acl_verify_message$& during the expansion of the &%message%& or
11091 &%log_message%& modifiers, to include information about the verification
11094 .vitem &$address_data$&
11095 .vindex "&$address_data$&"
11096 This variable is set by means of the &%address_data%& option in routers. The
11097 value then remains with the address while it is processed by subsequent routers
11098 and eventually a transport. If the transport is handling multiple addresses,
11099 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
11100 for more details. &*Note*&: The contents of &$address_data$& are visible in
11103 If &$address_data$& is set when the routers are called from an ACL to verify
11104 a recipient address, the final value is still in the variable for subsequent
11105 conditions and modifiers of the ACL statement. If routing the address caused it
11106 to be redirected to just one address, the child address is also routed as part
11107 of the verification, and in this case the final value of &$address_data$& is
11108 from the child's routing.
11110 If &$address_data$& is set when the routers are called from an ACL to verify a
11111 sender address, the final value is also preserved, but this time in
11112 &$sender_address_data$&, to distinguish it from data from a recipient
11115 In both cases (recipient and sender verification), the value does not persist
11116 after the end of the current ACL statement. If you want to preserve
11117 these values for longer, you can save them in ACL variables.
11119 .vitem &$address_file$&
11120 .vindex "&$address_file$&"
11121 When, as a result of aliasing, forwarding, or filtering, a message is directed
11122 to a specific file, this variable holds the name of the file when the transport
11123 is running. At other times, the variable is empty. For example, using the
11124 default configuration, if user &%r2d2%& has a &_.forward_& file containing
11126 /home/r2d2/savemail
11128 then when the &(address_file)& transport is running, &$address_file$&
11129 contains the text string &`/home/r2d2/savemail`&.
11130 .cindex "Sieve filter" "value of &$address_file$&"
11131 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
11132 then up to the transport configuration to generate an appropriate absolute path
11133 to the relevant file.
11135 .vitem &$address_pipe$&
11136 .vindex "&$address_pipe$&"
11137 When, as a result of aliasing or forwarding, a message is directed to a pipe,
11138 this variable holds the pipe command when the transport is running.
11140 .vitem "&$auth1$& &-- &$auth3$&"
11141 .vindex "&$auth1$&, &$auth2$&, etc"
11142 These variables are used in SMTP authenticators (see chapters
11143 &<<CHAPplaintext>>&&--&<<CHAPspa>>&). Elsewhere, they are empty.
11145 .vitem &$authenticated_id$&
11146 .cindex "authentication" "id"
11147 .vindex "&$authenticated_id$&"
11148 When a server successfully authenticates a client it may be configured to
11149 preserve some of the authentication information in the variable
11150 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
11151 user/password authenticator configuration might preserve the user name for use
11152 in the routers. Note that this is not the same information that is saved in
11153 &$sender_host_authenticated$&.
11154 When a message is submitted locally (that is, not over a TCP connection)
11155 the value of &$authenticated_id$& is normally the login name of the calling
11156 process. However, a trusted user can override this by means of the &%-oMai%&
11157 command line option.
11159 .vitem &$authenticated_fail_id$&
11160 .cindex "authentication" "fail" "id"
11161 .vindex "&$authenticated_fail_id$&"
11162 When an authentication attempt fails, the variable &$authenticated_fail_id$&
11163 will contain the failed authentication id. If more than one authentication
11164 id is attempted, it will contain only the last one. The variable is
11165 available for processing in the ACL's, generally the quit or notquit ACL.
11166 A message to a local recipient could still be accepted without requiring
11167 authentication, which means this variable could also be visible in all of
11171 .vitem &$authenticated_sender$&
11172 .cindex "sender" "authenticated"
11173 .cindex "authentication" "sender"
11174 .cindex "AUTH" "on MAIL command"
11175 .vindex "&$authenticated_sender$&"
11176 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
11177 SMTP MAIL command if it believes the sender is sufficiently trusted, as
11178 described in section &<<SECTauthparamail>>&. Unless the data is the string
11179 &"<>"&, it is set as the authenticated sender of the message, and the value is
11180 available during delivery in the &$authenticated_sender$& variable. If the
11181 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
11183 .vindex "&$qualify_domain$&"
11184 When a message is submitted locally (that is, not over a TCP connection), the
11185 value of &$authenticated_sender$& is an address constructed from the login
11186 name of the calling process and &$qualify_domain$&, except that a trusted user
11187 can override this by means of the &%-oMas%& command line option.
11190 .vitem &$authentication_failed$&
11191 .cindex "authentication" "failure"
11192 .vindex "&$authentication_failed$&"
11193 This variable is set to &"1"& in an Exim server if a client issues an AUTH
11194 command that does not succeed. Otherwise it is set to &"0"&. This makes it
11195 possible to distinguish between &"did not try to authenticate"&
11196 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
11197 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
11198 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
11199 negative response to an AUTH command, including (for example) an attempt to use
11200 an undefined mechanism.
11202 .vitem &$av_failed$&
11203 .cindex "content scanning" "AV scanner failure"
11204 This variable is available when Exim is compiled with the content-scanning
11205 extension. It is set to &"0"& by default, but will be set to &"1"& if any
11206 problem occurs with the virus scanner (specified by &%av_scanner%&) during
11207 the ACL malware condition.
11209 .vitem &$body_linecount$&
11210 .cindex "message body" "line count"
11211 .cindex "body of message" "line count"
11212 .vindex "&$body_linecount$&"
11213 When a message is being received or delivered, this variable contains the
11214 number of lines in the message's body. See also &$message_linecount$&.
11216 .vitem &$body_zerocount$&
11217 .cindex "message body" "binary zero count"
11218 .cindex "body of message" "binary zero count"
11219 .cindex "binary zero" "in message body"
11220 .vindex "&$body_zerocount$&"
11221 When a message is being received or delivered, this variable contains the
11222 number of binary zero bytes (ASCII NULs) in the message's body.
11224 .vitem &$bounce_recipient$&
11225 .vindex "&$bounce_recipient$&"
11226 This is set to the recipient address of a bounce message while Exim is creating
11227 it. It is useful if a customized bounce message text file is in use (see
11228 chapter &<<CHAPemsgcust>>&).
11230 .vitem &$bounce_return_size_limit$&
11231 .vindex "&$bounce_return_size_limit$&"
11232 This contains the value set in the &%bounce_return_size_limit%& option, rounded
11233 up to a multiple of 1000. It is useful when a customized error message text
11234 file is in use (see chapter &<<CHAPemsgcust>>&).
11236 .vitem &$caller_gid$&
11237 .cindex "gid (group id)" "caller"
11238 .vindex "&$caller_gid$&"
11239 The real group id under which the process that called Exim was running. This is
11240 not the same as the group id of the originator of a message (see
11241 &$originator_gid$&). If Exim re-execs itself, this variable in the new
11242 incarnation normally contains the Exim gid.
11244 .vitem &$caller_uid$&
11245 .cindex "uid (user id)" "caller"
11246 .vindex "&$caller_uid$&"
11247 The real user id under which the process that called Exim was running. This is
11248 not the same as the user id of the originator of a message (see
11249 &$originator_uid$&). If Exim re-execs itself, this variable in the new
11250 incarnation normally contains the Exim uid.
11252 .vitem &$compile_date$&
11253 .vindex "&$compile_date$&"
11254 The date on which the Exim binary was compiled.
11256 .vitem &$compile_number$&
11257 .vindex "&$compile_number$&"
11258 The building process for Exim keeps a count of the number
11259 of times it has been compiled. This serves to distinguish different
11260 compilations of the same version of the program.
11262 .vitem &$demime_errorlevel$&
11263 .vindex "&$demime_errorlevel$&"
11264 This variable is available when Exim is compiled with
11265 the content-scanning extension and the obsolete &%demime%& condition. For
11266 details, see section &<<SECTdemimecond>>&.
11268 .vitem &$demime_reason$&
11269 .vindex "&$demime_reason$&"
11270 This variable is available when Exim is compiled with the
11271 content-scanning extension and the obsolete &%demime%& condition. For details,
11272 see section &<<SECTdemimecond>>&.
11274 .vitem &$dnslist_domain$& &&&
11275 &$dnslist_matched$& &&&
11276 &$dnslist_text$& &&&
11278 .vindex "&$dnslist_domain$&"
11279 .vindex "&$dnslist_matched$&"
11280 .vindex "&$dnslist_text$&"
11281 .vindex "&$dnslist_value$&"
11282 .cindex "black list (DNS)"
11283 When a DNS (black) list lookup succeeds, these variables are set to contain
11284 the following data from the lookup: the list's domain name, the key that was
11285 looked up, the contents of any associated TXT record, and the value from the
11286 main A record. See section &<<SECID204>>& for more details.
11289 .vindex "&$domain$&"
11290 When an address is being routed, or delivered on its own, this variable
11291 contains the domain. Uppercase letters in the domain are converted into lower
11292 case for &$domain$&.
11294 Global address rewriting happens when a message is received, so the value of
11295 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
11296 is set during user filtering, but not during system filtering, because a
11297 message may have many recipients and the system filter is called just once.
11299 When more than one address is being delivered at once (for example, several
11300 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
11301 have the same domain. Transports can be restricted to handling only one domain
11302 at a time if the value of &$domain$& is required at transport time &-- this is
11303 the default for local transports. For further details of the environment in
11304 which local transports are run, see chapter &<<CHAPenvironment>>&.
11306 .oindex "&%delay_warning_condition%&"
11307 At the end of a delivery, if all deferred addresses have the same domain, it is
11308 set in &$domain$& during the expansion of &%delay_warning_condition%&.
11310 The &$domain$& variable is also used in some other circumstances:
11313 When an ACL is running for a RCPT command, &$domain$& contains the domain of
11314 the recipient address. The domain of the &'sender'& address is in
11315 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
11316 normally set during the running of the MAIL ACL. However, if the sender address
11317 is verified with a callout during the MAIL ACL, the sender domain is placed in
11318 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
11319 the &(smtp)& transport.
11322 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
11323 &$domain$& contains the domain portion of the address that is being rewritten;
11324 it can be used in the expansion of the replacement address, for example, to
11325 rewrite domains by file lookup.
11328 With one important exception, whenever a domain list is being scanned,
11329 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
11330 a &%sender_domains%& condition in an ACL is being processed, the subject domain
11331 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
11332 that, in a RCPT ACL, the sender domain list can be dependent on the
11333 recipient domain (which is what is in &$domain$& at this time).
11336 .cindex "ETRN" "value of &$domain$&"
11337 .oindex "&%smtp_etrn_command%&"
11338 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
11339 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
11343 .vitem &$domain_data$&
11344 .vindex "&$domain_data$&"
11345 When the &%domains%& option on a router matches a domain by
11346 means of a lookup, the data read by the lookup is available during the running
11347 of the router as &$domain_data$&. In addition, if the driver routes the
11348 address to a transport, the value is available in that transport. If the
11349 transport is handling multiple addresses, the value from the first address is
11352 &$domain_data$& is also set when the &%domains%& condition in an ACL matches a
11353 domain by means of a lookup. The data read by the lookup is available during
11354 the rest of the ACL statement. In all other situations, this variable expands
11357 .vitem &$exim_gid$&
11358 .vindex "&$exim_gid$&"
11359 This variable contains the numerical value of the Exim group id.
11361 .vitem &$exim_path$&
11362 .vindex "&$exim_path$&"
11363 This variable contains the path to the Exim binary.
11365 .vitem &$exim_uid$&
11366 .vindex "&$exim_uid$&"
11367 This variable contains the numerical value of the Exim user id.
11369 .vitem &$found_extension$&
11370 .vindex "&$found_extension$&"
11371 This variable is available when Exim is compiled with the
11372 content-scanning extension and the obsolete &%demime%& condition. For details,
11373 see section &<<SECTdemimecond>>&.
11375 .vitem &$header_$&<&'name'&>
11376 This is not strictly an expansion variable. It is expansion syntax for
11377 inserting the message header line with the given name. Note that the name must
11378 be terminated by colon or white space, because it may contain a wide variety of
11379 characters. Note also that braces must &'not'& be used.
11381 .vitem &$headers_added$&
11382 .vindex "&$headers_added$&"
11383 Within an ACL this variable contains the headers added so far by
11384 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
11385 The headers are a newline-separated list.
11389 When the &%check_local_user%& option is set for a router, the user's home
11390 directory is placed in &$home$& when the check succeeds. In particular, this
11391 means it is set during the running of users' filter files. A router may also
11392 explicitly set a home directory for use by a transport; this can be overridden
11393 by a setting on the transport itself.
11395 When running a filter test via the &%-bf%& option, &$home$& is set to the value
11396 of the environment variable HOME.
11400 If a router assigns an address to a transport (any transport), and passes a
11401 list of hosts with the address, the value of &$host$& when the transport starts
11402 to run is the name of the first host on the list. Note that this applies both
11403 to local and remote transports.
11405 .cindex "transport" "filter"
11406 .cindex "filter" "transport filter"
11407 For the &(smtp)& transport, if there is more than one host, the value of
11408 &$host$& changes as the transport works its way through the list. In
11409 particular, when the &(smtp)& transport is expanding its options for encryption
11410 using TLS, or for specifying a transport filter (see chapter
11411 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
11414 When used in the client part of an authenticator configuration (see chapter
11415 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
11416 client is connected.
11419 .vitem &$host_address$&
11420 .vindex "&$host_address$&"
11421 This variable is set to the remote host's IP address whenever &$host$& is set
11422 for a remote connection. It is also set to the IP address that is being checked
11423 when the &%ignore_target_hosts%& option is being processed.
11425 .vitem &$host_data$&
11426 .vindex "&$host_data$&"
11427 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
11428 result of the lookup is made available in the &$host_data$& variable. This
11429 allows you, for example, to do things like this:
11431 deny hosts = net-lsearch;/some/file
11432 message = $host_data
11434 .vitem &$host_lookup_deferred$&
11435 .cindex "host name" "lookup, failure of"
11436 .vindex "&$host_lookup_deferred$&"
11437 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
11438 message comes from a remote host and there is an attempt to look up the host's
11439 name from its IP address, and the attempt is not successful, one of these
11440 variables is set to &"1"&.
11443 If the lookup receives a definite negative response (for example, a DNS lookup
11444 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
11447 If there is any kind of problem during the lookup, such that Exim cannot
11448 tell whether or not the host name is defined (for example, a timeout for a DNS
11449 lookup), &$host_lookup_deferred$& is set to &"1"&.
11452 Looking up a host's name from its IP address consists of more than just a
11453 single reverse lookup. Exim checks that a forward lookup of at least one of the
11454 names it receives from a reverse lookup yields the original IP address. If this
11455 is not the case, Exim does not accept the looked up name(s), and
11456 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
11457 IP address (for example, the existence of a PTR record in the DNS) is not
11458 sufficient on its own for the success of a host name lookup. If the reverse
11459 lookup succeeds, but there is a lookup problem such as a timeout when checking
11460 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
11461 &"1"&. See also &$sender_host_name$&.
11463 .vitem &$host_lookup_failed$&
11464 .vindex "&$host_lookup_failed$&"
11465 See &$host_lookup_deferred$&.
11467 .vitem &$host_port$&
11468 .vindex "&$host_port$&"
11469 This variable is set to the remote host's TCP port whenever &$host$& is set
11470 for an outbound connection.
11474 .vindex "&$inode$&"
11475 The only time this variable is set is while expanding the &%directory_file%&
11476 option in the &(appendfile)& transport. The variable contains the inode number
11477 of the temporary file which is about to be renamed. It can be used to construct
11478 a unique name for the file.
11480 .vitem &$interface_address$&
11481 .vindex "&$interface_address$&"
11482 This is an obsolete name for &$received_ip_address$&.
11484 .vitem &$interface_port$&
11485 .vindex "&$interface_port$&"
11486 This is an obsolete name for &$received_port$&.
11490 This variable is used during the expansion of &*forall*& and &*forany*&
11491 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
11492 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
11496 .vindex "&$ldap_dn$&"
11497 This variable, which is available only when Exim is compiled with LDAP support,
11498 contains the DN from the last entry in the most recently successful LDAP
11501 .vitem &$load_average$&
11502 .vindex "&$load_average$&"
11503 This variable contains the system load average, multiplied by 1000 so that it
11504 is an integer. For example, if the load average is 0.21, the value of the
11505 variable is 210. The value is recomputed every time the variable is referenced.
11507 .vitem &$local_part$&
11508 .vindex "&$local_part$&"
11509 When an address is being routed, or delivered on its own, this
11510 variable contains the local part. When a number of addresses are being
11511 delivered together (for example, multiple RCPT commands in an SMTP
11512 session), &$local_part$& is not set.
11514 Global address rewriting happens when a message is received, so the value of
11515 &$local_part$& during routing and delivery is the value after rewriting.
11516 &$local_part$& is set during user filtering, but not during system filtering,
11517 because a message may have many recipients and the system filter is called just
11520 .vindex "&$local_part_prefix$&"
11521 .vindex "&$local_part_suffix$&"
11522 If a local part prefix or suffix has been recognized, it is not included in the
11523 value of &$local_part$& during routing and subsequent delivery. The values of
11524 any prefix or suffix are in &$local_part_prefix$& and
11525 &$local_part_suffix$&, respectively.
11527 When a message is being delivered to a file, pipe, or autoreply transport as a
11528 result of aliasing or forwarding, &$local_part$& is set to the local part of
11529 the parent address, not to the file name or command (see &$address_file$& and
11532 When an ACL is running for a RCPT command, &$local_part$& contains the
11533 local part of the recipient address.
11535 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
11536 &$local_part$& contains the local part of the address that is being rewritten;
11537 it can be used in the expansion of the replacement address, for example.
11539 In all cases, all quoting is removed from the local part. For example, for both
11542 "abc:xyz"@test.example
11543 abc\:xyz@test.example
11545 the value of &$local_part$& is
11549 If you use &$local_part$& to create another address, you should always wrap it
11550 inside a quoting operator. For example, in a &(redirect)& router you could
11553 data = ${quote_local_part:$local_part}@new.domain.example
11555 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
11556 to process local parts in a case-dependent manner in a router, you can set the
11557 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
11559 .vitem &$local_part_data$&
11560 .vindex "&$local_part_data$&"
11561 When the &%local_parts%& option on a router matches a local part by means of a
11562 lookup, the data read by the lookup is available during the running of the
11563 router as &$local_part_data$&. In addition, if the driver routes the address
11564 to a transport, the value is available in that transport. If the transport is
11565 handling multiple addresses, the value from the first address is used.
11567 &$local_part_data$& is also set when the &%local_parts%& condition in an ACL
11568 matches a local part by means of a lookup. The data read by the lookup is
11569 available during the rest of the ACL statement. In all other situations, this
11570 variable expands to nothing.
11572 .vitem &$local_part_prefix$&
11573 .vindex "&$local_part_prefix$&"
11574 When an address is being routed or delivered, and a
11575 specific prefix for the local part was recognized, it is available in this
11576 variable, having been removed from &$local_part$&.
11578 .vitem &$local_part_suffix$&
11579 .vindex "&$local_part_suffix$&"
11580 When an address is being routed or delivered, and a
11581 specific suffix for the local part was recognized, it is available in this
11582 variable, having been removed from &$local_part$&.
11584 .vitem &$local_scan_data$&
11585 .vindex "&$local_scan_data$&"
11586 This variable contains the text returned by the &[local_scan()]& function when
11587 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
11589 .vitem &$local_user_gid$&
11590 .vindex "&$local_user_gid$&"
11591 See &$local_user_uid$&.
11593 .vitem &$local_user_uid$&
11594 .vindex "&$local_user_uid$&"
11595 This variable and &$local_user_gid$& are set to the uid and gid after the
11596 &%check_local_user%& router precondition succeeds. This means that their values
11597 are available for the remaining preconditions (&%senders%&, &%require_files%&,
11598 and &%condition%&), for the &%address_data%& expansion, and for any
11599 router-specific expansions. At all other times, the values in these variables
11600 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
11602 .vitem &$localhost_number$&
11603 .vindex "&$localhost_number$&"
11604 This contains the expanded value of the
11605 &%localhost_number%& option. The expansion happens after the main options have
11608 .vitem &$log_inodes$&
11609 .vindex "&$log_inodes$&"
11610 The number of free inodes in the disk partition where Exim's
11611 log files are being written. The value is recalculated whenever the variable is
11612 referenced. If the relevant file system does not have the concept of inodes,
11613 the value of is -1. See also the &%check_log_inodes%& option.
11615 .vitem &$log_space$&
11616 .vindex "&$log_space$&"
11617 The amount of free space (as a number of kilobytes) in the disk
11618 partition where Exim's log files are being written. The value is recalculated
11619 whenever the variable is referenced. If the operating system does not have the
11620 ability to find the amount of free space (only true for experimental systems),
11621 the space value is -1. See also the &%check_log_space%& option.
11624 .vitem &$lookup_dnssec_authenticated$&
11625 .vindex "&$lookup_dnssec_authenticated$&"
11626 This variable is set after a DNS lookup done by
11627 a dnsdb lookup expansion, dnslookup router or smtp transport.
11628 It will be empty if &(DNSSEC)& was not requested,
11629 &"no"& if the result was not labelled as authenticated data
11630 and &"yes"& if it was.
11632 .vitem &$mailstore_basename$&
11633 .vindex "&$mailstore_basename$&"
11634 This variable is set only when doing deliveries in &"mailstore"& format in the
11635 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
11636 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
11637 contains the basename of the files that are being written, that is, the name
11638 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
11641 .vitem &$malware_name$&
11642 .vindex "&$malware_name$&"
11643 This variable is available when Exim is compiled with the
11644 content-scanning extension. It is set to the name of the virus that was found
11645 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
11647 .vitem &$max_received_linelength$&
11648 .vindex "&$max_received_linelength$&"
11649 .cindex "maximum" "line length"
11650 .cindex "line length" "maximum"
11651 This variable contains the number of bytes in the longest line that was
11652 received as part of the message, not counting the line termination
11655 .vitem &$message_age$&
11656 .cindex "message" "age of"
11657 .vindex "&$message_age$&"
11658 This variable is set at the start of a delivery attempt to contain the number
11659 of seconds since the message was received. It does not change during a single
11662 .vitem &$message_body$&
11663 .cindex "body of message" "expansion variable"
11664 .cindex "message body" "in expansion"
11665 .cindex "binary zero" "in message body"
11666 .vindex "&$message_body$&"
11667 .oindex "&%message_body_visible%&"
11668 This variable contains the initial portion of a message's body while it is
11669 being delivered, and is intended mainly for use in filter files. The maximum
11670 number of characters of the body that are put into the variable is set by the
11671 &%message_body_visible%& configuration option; the default is 500.
11673 .oindex "&%message_body_newlines%&"
11674 By default, newlines are converted into spaces in &$message_body$&, to make it
11675 easier to search for phrases that might be split over a line break. However,
11676 this can be disabled by setting &%message_body_newlines%& to be true. Binary
11677 zeros are always converted into spaces.
11679 .vitem &$message_body_end$&
11680 .cindex "body of message" "expansion variable"
11681 .cindex "message body" "in expansion"
11682 .vindex "&$message_body_end$&"
11683 This variable contains the final portion of a message's
11684 body while it is being delivered. The format and maximum size are as for
11687 .vitem &$message_body_size$&
11688 .cindex "body of message" "size"
11689 .cindex "message body" "size"
11690 .vindex "&$message_body_size$&"
11691 When a message is being delivered, this variable contains the size of the body
11692 in bytes. The count starts from the character after the blank line that
11693 separates the body from the header. Newlines are included in the count. See
11694 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
11696 .vitem &$message_exim_id$&
11697 .vindex "&$message_exim_id$&"
11698 When a message is being received or delivered, this variable contains the
11699 unique message id that is generated and used by Exim to identify the message.
11700 An id is not created for a message until after its header has been successfully
11701 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
11702 line; it is the local id that Exim assigns to the message, for example:
11703 &`1BXTIK-0001yO-VA`&.
11705 .vitem &$message_headers$&
11706 .vindex &$message_headers$&
11707 This variable contains a concatenation of all the header lines when a message
11708 is being processed, except for lines added by routers or transports. The header
11709 lines are separated by newline characters. Their contents are decoded in the
11710 same way as a header line that is inserted by &%bheader%&.
11712 .vitem &$message_headers_raw$&
11713 .vindex &$message_headers_raw$&
11714 This variable is like &$message_headers$& except that no processing of the
11715 contents of header lines is done.
11717 .vitem &$message_id$&
11718 This is an old name for &$message_exim_id$&. It is now deprecated.
11720 .vitem &$message_linecount$&
11721 .vindex "&$message_linecount$&"
11722 This variable contains the total number of lines in the header and body of the
11723 message. Compare &$body_linecount$&, which is the count for the body only.
11724 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
11725 number of lines received. Before delivery happens (that is, before filters,
11726 routers, and transports run) the count is increased to include the
11727 &'Received:'& header line that Exim standardly adds, and also any other header
11728 lines that are added by ACLs. The blank line that separates the message header
11729 from the body is not counted.
11731 As with the special case of &$message_size$&, during the expansion of the
11732 appendfile transport's maildir_tag option in maildir format, the value of
11733 &$message_linecount$& is the precise size of the number of newlines in the
11734 file that has been written (minus one for the blank line between the
11735 header and the body).
11737 Here is an example of the use of this variable in a DATA ACL:
11739 deny message = Too many lines in message header
11741 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
11743 In the MAIL and RCPT ACLs, the value is zero because at that stage the
11744 message has not yet been received.
11746 .vitem &$message_size$&
11747 .cindex "size" "of message"
11748 .cindex "message" "size"
11749 .vindex "&$message_size$&"
11750 When a message is being processed, this variable contains its size in bytes. In
11751 most cases, the size includes those headers that were received with the
11752 message, but not those (such as &'Envelope-to:'&) that are added to individual
11753 deliveries as they are written. However, there is one special case: during the
11754 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
11755 doing a delivery in maildir format, the value of &$message_size$& is the
11756 precise size of the file that has been written. See also
11757 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
11759 .cindex "RCPT" "value of &$message_size$&"
11760 While running a per message ACL (mail/rcpt/predata), &$message_size$&
11761 contains the size supplied on the MAIL command, or -1 if no size was given. The
11762 value may not, of course, be truthful.
11764 .vitem &$mime_$&&'xxx'&
11765 A number of variables whose names start with &$mime$& are
11766 available when Exim is compiled with the content-scanning extension. For
11767 details, see section &<<SECTscanmimepart>>&.
11769 .vitem "&$n0$& &-- &$n9$&"
11770 These variables are counters that can be incremented by means
11771 of the &%add%& command in filter files.
11773 .vitem &$original_domain$&
11774 .vindex "&$domain$&"
11775 .vindex "&$original_domain$&"
11776 When a top-level address is being processed for delivery, this contains the
11777 same value as &$domain$&. However, if a &"child"& address (for example,
11778 generated by an alias, forward, or filter file) is being processed, this
11779 variable contains the domain of the original address (lower cased). This
11780 differs from &$parent_domain$& only when there is more than one level of
11781 aliasing or forwarding. When more than one address is being delivered in a
11782 single transport run, &$original_domain$& is not set.
11784 If a new address is created by means of a &%deliver%& command in a system
11785 filter, it is set up with an artificial &"parent"& address. This has the local
11786 part &'system-filter'& and the default qualify domain.
11788 .vitem &$original_local_part$&
11789 .vindex "&$local_part$&"
11790 .vindex "&$original_local_part$&"
11791 When a top-level address is being processed for delivery, this contains the
11792 same value as &$local_part$&, unless a prefix or suffix was removed from the
11793 local part, because &$original_local_part$& always contains the full local
11794 part. When a &"child"& address (for example, generated by an alias, forward, or
11795 filter file) is being processed, this variable contains the full local part of
11796 the original address.
11798 If the router that did the redirection processed the local part
11799 case-insensitively, the value in &$original_local_part$& is in lower case.
11800 This variable differs from &$parent_local_part$& only when there is more than
11801 one level of aliasing or forwarding. When more than one address is being
11802 delivered in a single transport run, &$original_local_part$& is not set.
11804 If a new address is created by means of a &%deliver%& command in a system
11805 filter, it is set up with an artificial &"parent"& address. This has the local
11806 part &'system-filter'& and the default qualify domain.
11808 .vitem &$originator_gid$&
11809 .cindex "gid (group id)" "of originating user"
11810 .cindex "sender" "gid"
11811 .vindex "&$caller_gid$&"
11812 .vindex "&$originator_gid$&"
11813 This variable contains the value of &$caller_gid$& that was set when the
11814 message was received. For messages received via the command line, this is the
11815 gid of the sending user. For messages received by SMTP over TCP/IP, this is
11816 normally the gid of the Exim user.
11818 .vitem &$originator_uid$&
11819 .cindex "uid (user id)" "of originating user"
11820 .cindex "sender" "uid"
11821 .vindex "&$caller_uid$&"
11822 .vindex "&$originaltor_uid$&"
11823 The value of &$caller_uid$& that was set when the message was received. For
11824 messages received via the command line, this is the uid of the sending user.
11825 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
11828 .vitem &$parent_domain$&
11829 .vindex "&$parent_domain$&"
11830 This variable is similar to &$original_domain$& (see
11831 above), except that it refers to the immediately preceding parent address.
11833 .vitem &$parent_local_part$&
11834 .vindex "&$parent_local_part$&"
11835 This variable is similar to &$original_local_part$&
11836 (see above), except that it refers to the immediately preceding parent address.
11839 .cindex "pid (process id)" "of current process"
11841 This variable contains the current process id.
11843 .vitem &$pipe_addresses$&
11844 .cindex "filter" "transport filter"
11845 .cindex "transport" "filter"
11846 .vindex "&$pipe_addresses$&"
11847 This is not an expansion variable, but is mentioned here because the string
11848 &`$pipe_addresses`& is handled specially in the command specification for the
11849 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
11850 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
11851 It cannot be used in general expansion strings, and provokes an &"unknown
11852 variable"& error if encountered.
11854 .vitem &$primary_hostname$&
11855 .vindex "&$primary_hostname$&"
11856 This variable contains the value set by &%primary_hostname%& in the
11857 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
11858 a single-component name, Exim calls &[gethostbyname()]& (or
11859 &[getipnodebyname()]& where available) in an attempt to acquire a fully
11860 qualified host name. See also &$smtp_active_hostname$&.
11863 .vitem &$prvscheck_address$&
11864 This variable is used in conjunction with the &%prvscheck%& expansion item,
11865 which is described in sections &<<SECTexpansionitems>>& and
11866 &<<SECTverifyPRVS>>&.
11868 .vitem &$prvscheck_keynum$&
11869 This variable is used in conjunction with the &%prvscheck%& expansion item,
11870 which is described in sections &<<SECTexpansionitems>>& and
11871 &<<SECTverifyPRVS>>&.
11873 .vitem &$prvscheck_result$&
11874 This variable is used in conjunction with the &%prvscheck%& expansion item,
11875 which is described in sections &<<SECTexpansionitems>>& and
11876 &<<SECTverifyPRVS>>&.
11878 .vitem &$qualify_domain$&
11879 .vindex "&$qualify_domain$&"
11880 The value set for the &%qualify_domain%& option in the configuration file.
11882 .vitem &$qualify_recipient$&
11883 .vindex "&$qualify_recipient$&"
11884 The value set for the &%qualify_recipient%& option in the configuration file,
11885 or if not set, the value of &$qualify_domain$&.
11887 .vitem &$rcpt_count$&
11888 .vindex "&$rcpt_count$&"
11889 When a message is being received by SMTP, this variable contains the number of
11890 RCPT commands received for the current message. If this variable is used in a
11891 RCPT ACL, its value includes the current command.
11893 .vitem &$rcpt_defer_count$&
11894 .vindex "&$rcpt_defer_count$&"
11895 .cindex "4&'xx'& responses" "count of"
11896 When a message is being received by SMTP, this variable contains the number of
11897 RCPT commands in the current message that have previously been rejected with a
11898 temporary (4&'xx'&) response.
11900 .vitem &$rcpt_fail_count$&
11901 .vindex "&$rcpt_fail_count$&"
11902 When a message is being received by SMTP, this variable contains the number of
11903 RCPT commands in the current message that have previously been rejected with a
11904 permanent (5&'xx'&) response.
11906 .vitem &$received_count$&
11907 .vindex "&$received_count$&"
11908 This variable contains the number of &'Received:'& header lines in the message,
11909 including the one added by Exim (so its value is always greater than zero). It
11910 is available in the DATA ACL, the non-SMTP ACL, and while routing and
11913 .vitem &$received_for$&
11914 .vindex "&$received_for$&"
11915 If there is only a single recipient address in an incoming message, this
11916 variable contains that address when the &'Received:'& header line is being
11917 built. The value is copied after recipient rewriting has happened, but before
11918 the &[local_scan()]& function is run.
11920 .vitem &$received_ip_address$&
11921 .vindex "&$received_ip_address$&"
11922 As soon as an Exim server starts processing an incoming TCP/IP connection, this
11923 variable is set to the address of the local IP interface, and &$received_port$&
11924 is set to the local port number. (The remote IP address and port are in
11925 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
11926 the port value is -1 unless it has been set using the &%-oMi%& command line
11929 As well as being useful in ACLs (including the &"connect"& ACL), these variable
11930 could be used, for example, to make the file name for a TLS certificate depend
11931 on which interface and/or port is being used for the incoming connection. The
11932 values of &$received_ip_address$& and &$received_port$& are saved with any
11933 messages that are received, thus making these variables available at delivery
11936 &*Note:*& There are no equivalent variables for outgoing connections, because
11937 the values are unknown (unless they are explicitly set by options of the
11938 &(smtp)& transport).
11940 .vitem &$received_port$&
11941 .vindex "&$received_port$&"
11942 See &$received_ip_address$&.
11944 .vitem &$received_protocol$&
11945 .vindex "&$received_protocol$&"
11946 When a message is being processed, this variable contains the name of the
11947 protocol by which it was received. Most of the names used by Exim are defined
11948 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
11949 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
11950 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
11951 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
11952 connection and the client was successfully authenticated.
11954 Exim uses the protocol name &"smtps"& for the case when encryption is
11955 automatically set up on connection without the use of STARTTLS (see
11956 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
11957 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
11958 where the client initially uses EHLO, sets up an encrypted connection using
11959 STARTTLS, and then uses HELO afterwards.
11961 The &%-oMr%& option provides a way of specifying a custom protocol name for
11962 messages that are injected locally by trusted callers. This is commonly used to
11963 identify messages that are being re-injected after some kind of scanning.
11965 .vitem &$received_time$&
11966 .vindex "&$received_time$&"
11967 This variable contains the date and time when the current message was received,
11968 as a number of seconds since the start of the Unix epoch.
11970 .vitem &$recipient_data$&
11971 .vindex "&$recipient_data$&"
11972 This variable is set after an indexing lookup success in an ACL &%recipients%&
11973 condition. It contains the data from the lookup, and the value remains set
11974 until the next &%recipients%& test. Thus, you can do things like this:
11976 &`require recipients = cdb*@;/some/file`&
11977 &`deny `&&'some further test involving'& &`$recipient_data`&
11979 &*Warning*&: This variable is set only when a lookup is used as an indexing
11980 method in the address list, using the semicolon syntax as in the example above.
11981 The variable is not set for a lookup that is used as part of the string
11982 expansion that all such lists undergo before being interpreted.
11984 .vitem &$recipient_verify_failure$&
11985 .vindex "&$recipient_verify_failure$&"
11986 In an ACL, when a recipient verification fails, this variable contains
11987 information about the failure. It is set to one of the following words:
11990 &"qualify"&: The address was unqualified (no domain), and the message
11991 was neither local nor came from an exempted host.
11994 &"route"&: Routing failed.
11997 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
11998 or before the MAIL command (that is, on initial connection, HELO, or
12002 &"recipient"&: The RCPT command in a callout was rejected.
12005 &"postmaster"&: The postmaster check in a callout was rejected.
12008 The main use of this variable is expected to be to distinguish between
12009 rejections of MAIL and rejections of RCPT.
12011 .vitem &$recipients$&
12012 .vindex "&$recipients$&"
12013 This variable contains a list of envelope recipients for a message. A comma and
12014 a space separate the addresses in the replacement text. However, the variable
12015 is not generally available, to prevent exposure of Bcc recipients in
12016 unprivileged users' filter files. You can use &$recipients$& only in these
12020 In a system filter file.
12022 In the ACLs associated with the DATA command and with non-SMTP messages, that
12023 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
12024 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
12025 &%acl_not_smtp_mime%&.
12027 From within a &[local_scan()]& function.
12031 .vitem &$recipients_count$&
12032 .vindex "&$recipients_count$&"
12033 When a message is being processed, this variable contains the number of
12034 envelope recipients that came with the message. Duplicates are not excluded
12035 from the count. While a message is being received over SMTP, the number
12036 increases for each accepted recipient. It can be referenced in an ACL.
12039 .vitem &$regex_match_string$&
12040 .vindex "&$regex_match_string$&"
12041 This variable is set to contain the matching regular expression after a
12042 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
12045 .vitem &$reply_address$&
12046 .vindex "&$reply_address$&"
12047 When a message is being processed, this variable contains the contents of the
12048 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
12049 contents of the &'From:'& header line. Apart from the removal of leading
12050 white space, the value is not processed in any way. In particular, no RFC 2047
12051 decoding or character code translation takes place.
12053 .vitem &$return_path$&
12054 .vindex "&$return_path$&"
12055 When a message is being delivered, this variable contains the return path &--
12056 the sender field that will be sent as part of the envelope. It is not enclosed
12057 in <> characters. At the start of routing an address, &$return_path$& has the
12058 same value as &$sender_address$&, but if, for example, an incoming message to a
12059 mailing list has been expanded by a router which specifies a different address
12060 for bounce messages, &$return_path$& subsequently contains the new bounce
12061 address, whereas &$sender_address$& always contains the original sender address
12062 that was received with the message. In other words, &$sender_address$& contains
12063 the incoming envelope sender, and &$return_path$& contains the outgoing
12066 .vitem &$return_size_limit$&
12067 .vindex "&$return_size_limit$&"
12068 This is an obsolete name for &$bounce_return_size_limit$&.
12070 .vitem &$router_name$&
12071 .cindex "router" "name"
12072 .cindex "name" "of router"
12073 .vindex "&$router_name$&"
12074 During the running of a router this variable contains its name.
12077 .cindex "return code" "from &%run%& expansion"
12078 .vindex "&$runrc$&"
12079 This variable contains the return code from a command that is run by the
12080 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
12081 assume the order in which option values are expanded, except for those
12082 preconditions whose order of testing is documented. Therefore, you cannot
12083 reliably expect to set &$runrc$& by the expansion of one option, and use it in
12086 .vitem &$self_hostname$&
12087 .oindex "&%self%&" "value of host name"
12088 .vindex "&$self_hostname$&"
12089 When an address is routed to a supposedly remote host that turns out to be the
12090 local host, what happens is controlled by the &%self%& generic router option.
12091 One of its values causes the address to be passed to another router. When this
12092 happens, &$self_hostname$& is set to the name of the local host that the
12093 original router encountered. In other circumstances its contents are null.
12095 .vitem &$sender_address$&
12096 .vindex "&$sender_address$&"
12097 When a message is being processed, this variable contains the sender's address
12098 that was received in the message's envelope. The case of letters in the address
12099 is retained, in both the local part and the domain. For bounce messages, the
12100 value of this variable is the empty string. See also &$return_path$&.
12102 .vitem &$sender_address_data$&
12103 .vindex "&$address_data$&"
12104 .vindex "&$sender_address_data$&"
12105 If &$address_data$& is set when the routers are called from an ACL to verify a
12106 sender address, the final value is preserved in &$sender_address_data$&, to
12107 distinguish it from data from a recipient address. The value does not persist
12108 after the end of the current ACL statement. If you want to preserve it for
12109 longer, you can save it in an ACL variable.
12111 .vitem &$sender_address_domain$&
12112 .vindex "&$sender_address_domain$&"
12113 The domain portion of &$sender_address$&.
12115 .vitem &$sender_address_local_part$&
12116 .vindex "&$sender_address_local_part$&"
12117 The local part portion of &$sender_address$&.
12119 .vitem &$sender_data$&
12120 .vindex "&$sender_data$&"
12121 This variable is set after a lookup success in an ACL &%senders%& condition or
12122 in a router &%senders%& option. It contains the data from the lookup, and the
12123 value remains set until the next &%senders%& test. Thus, you can do things like
12126 &`require senders = cdb*@;/some/file`&
12127 &`deny `&&'some further test involving'& &`$sender_data`&
12129 &*Warning*&: This variable is set only when a lookup is used as an indexing
12130 method in the address list, using the semicolon syntax as in the example above.
12131 The variable is not set for a lookup that is used as part of the string
12132 expansion that all such lists undergo before being interpreted.
12134 .vitem &$sender_fullhost$&
12135 .vindex "&$sender_fullhost$&"
12136 When a message is received from a remote host, this variable contains the host
12137 name and IP address in a single string. It ends with the IP address in square
12138 brackets, followed by a colon and a port number if the logging of ports is
12139 enabled. The format of the rest of the string depends on whether the host
12140 issued a HELO or EHLO SMTP command, and whether the host name was verified by
12141 looking up its IP address. (Looking up the IP address can be forced by the
12142 &%host_lookup%& option, independent of verification.) A plain host name at the
12143 start of the string is a verified host name; if this is not present,
12144 verification either failed or was not requested. A host name in parentheses is
12145 the argument of a HELO or EHLO command. This is omitted if it is identical to
12146 the verified host name or to the host's IP address in square brackets.
12148 .vitem &$sender_helo_name$&
12149 .vindex "&$sender_helo_name$&"
12150 When a message is received from a remote host that has issued a HELO or EHLO
12151 command, the argument of that command is placed in this variable. It is also
12152 set if HELO or EHLO is used when a message is received using SMTP locally via
12153 the &%-bs%& or &%-bS%& options.
12155 .vitem &$sender_host_address$&
12156 .vindex "&$sender_host_address$&"
12157 When a message is received from a remote host using SMTP,
12158 this variable contains that
12159 host's IP address. For locally non-SMTP submitted messages, it is empty.
12161 .vitem &$sender_host_authenticated$&
12162 .vindex "&$sender_host_authenticated$&"
12163 This variable contains the name (not the public name) of the authenticator
12164 driver that successfully authenticated the client from which the message was
12165 received. It is empty if there was no successful authentication. See also
12166 &$authenticated_id$&.
12168 .vitem &$sender_host_dnssec$&
12169 .vindex "&$sender_host_dnssec$&"
12170 If an attempt to populate &$sender_host_name$& has been made
12171 (by reference, &%hosts_lookup%& or
12172 otherwise) then this boolean will have been set true if, and only if, the
12173 resolver library states that the reverse DNS was authenticated data. At all
12174 other times, this variable is false.
12176 It is likely that you will need to coerce DNSSEC support on in the resolver
12177 library, by setting:
12182 Exim does not perform DNSSEC validation itself, instead leaving that to a
12183 validating resolver (eg, unbound, or bind with suitable configuration).
12185 Exim does not (currently) check to see if the forward DNS was also secured
12186 with DNSSEC, only the reverse DNS.
12188 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
12189 mechanism in the list, then this variable will be false.
12192 .vitem &$sender_host_name$&
12193 .vindex "&$sender_host_name$&"
12194 When a message is received from a remote host, this variable contains the
12195 host's name as obtained by looking up its IP address. For messages received by
12196 other means, this variable is empty.
12198 .vindex "&$host_lookup_failed$&"
12199 If the host name has not previously been looked up, a reference to
12200 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
12201 A looked up name is accepted only if it leads back to the original IP address
12202 via a forward lookup. If either the reverse or the forward lookup fails to find
12203 any data, or if the forward lookup does not yield the original IP address,
12204 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
12206 .vindex "&$host_lookup_deferred$&"
12207 However, if either of the lookups cannot be completed (for example, there is a
12208 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
12209 &$host_lookup_failed$& remains set to &"0"&.
12211 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
12212 host name again if there is a subsequent reference to &$sender_host_name$&
12213 in the same Exim process, but it does try again if &$host_lookup_deferred$&
12216 Exim does not automatically look up every calling host's name. If you want
12217 maximum efficiency, you should arrange your configuration so that it avoids
12218 these lookups altogether. The lookup happens only if one or more of the
12219 following are true:
12222 A string containing &$sender_host_name$& is expanded.
12224 The calling host matches the list in &%host_lookup%&. In the default
12225 configuration, this option is set to *, so it must be changed if lookups are
12226 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
12228 Exim needs the host name in order to test an item in a host list. The items
12229 that require this are described in sections &<<SECThoslispatnam>>& and
12230 &<<SECThoslispatnamsk>>&.
12232 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
12233 In this case, the host name is required to compare with the name quoted in any
12234 EHLO or HELO commands that the client issues.
12236 The remote host issues a EHLO or HELO command that quotes one of the
12237 domains in &%helo_lookup_domains%&. The default value of this option is
12238 . ==== As this is a nested list, any displays it contains must be indented
12239 . ==== as otherwise they are too far to the left.
12241 helo_lookup_domains = @ : @[]
12243 which causes a lookup if a remote host (incorrectly) gives the server's name or
12244 IP address in an EHLO or HELO command.
12248 .vitem &$sender_host_port$&
12249 .vindex "&$sender_host_port$&"
12250 When a message is received from a remote host, this variable contains the port
12251 number that was used on the remote host.
12253 .vitem &$sender_ident$&
12254 .vindex "&$sender_ident$&"
12255 When a message is received from a remote host, this variable contains the
12256 identification received in response to an RFC 1413 request. When a message has
12257 been received locally, this variable contains the login name of the user that
12260 .vitem &$sender_rate_$&&'xxx'&
12261 A number of variables whose names begin &$sender_rate_$& are set as part of the
12262 &%ratelimit%& ACL condition. Details are given in section
12263 &<<SECTratelimiting>>&.
12265 .vitem &$sender_rcvhost$&
12266 .cindex "DNS" "reverse lookup"
12267 .cindex "reverse DNS lookup"
12268 .vindex "&$sender_rcvhost$&"
12269 This is provided specifically for use in &'Received:'& headers. It starts with
12270 either the verified host name (as obtained from a reverse DNS lookup) or, if
12271 there is no verified host name, the IP address in square brackets. After that
12272 there may be text in parentheses. When the first item is a verified host name,
12273 the first thing in the parentheses is the IP address in square brackets,
12274 followed by a colon and a port number if port logging is enabled. When the
12275 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
12278 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
12279 was used and its argument was not identical to the real host name or IP
12280 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
12281 all three items are present in the parentheses, a newline and tab are inserted
12282 into the string, to improve the formatting of the &'Received:'& header.
12284 .vitem &$sender_verify_failure$&
12285 .vindex "&$sender_verify_failure$&"
12286 In an ACL, when a sender verification fails, this variable contains information
12287 about the failure. The details are the same as for
12288 &$recipient_verify_failure$&.
12290 .vitem &$sending_ip_address$&
12291 .vindex "&$sending_ip_address$&"
12292 This variable is set whenever an outgoing SMTP connection to another host has
12293 been set up. It contains the IP address of the local interface that is being
12294 used. This is useful if a host that has more than one IP address wants to take
12295 on different personalities depending on which one is being used. For incoming
12296 connections, see &$received_ip_address$&.
12298 .vitem &$sending_port$&
12299 .vindex "&$sending_port$&"
12300 This variable is set whenever an outgoing SMTP connection to another host has
12301 been set up. It contains the local port that is being used. For incoming
12302 connections, see &$received_port$&.
12304 .vitem &$smtp_active_hostname$&
12305 .vindex "&$smtp_active_hostname$&"
12306 During an incoming SMTP session, this variable contains the value of the active
12307 host name, as specified by the &%smtp_active_hostname%& option. The value of
12308 &$smtp_active_hostname$& is saved with any message that is received, so its
12309 value can be consulted during routing and delivery.
12311 .vitem &$smtp_command$&
12312 .vindex "&$smtp_command$&"
12313 During the processing of an incoming SMTP command, this variable contains the
12314 entire command. This makes it possible to distinguish between HELO and EHLO in
12315 the HELO ACL, and also to distinguish between commands such as these:
12320 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
12321 command, the address in &$smtp_command$& is the original address before any
12322 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
12323 the address after SMTP-time rewriting.
12325 .vitem &$smtp_command_argument$&
12326 .cindex "SMTP" "command, argument for"
12327 .vindex "&$smtp_command_argument$&"
12328 While an ACL is running to check an SMTP command, this variable contains the
12329 argument, that is, the text that follows the command name, with leading white
12330 space removed. Following the introduction of &$smtp_command$&, this variable is
12331 somewhat redundant, but is retained for backwards compatibility.
12333 .vitem &$smtp_count_at_connection_start$&
12334 .vindex "&$smtp_count_at_connection_start$&"
12335 This variable is set greater than zero only in processes spawned by the Exim
12336 daemon for handling incoming SMTP connections. The name is deliberately long,
12337 in order to emphasize what the contents are. When the daemon accepts a new
12338 connection, it increments this variable. A copy of the variable is passed to
12339 the child process that handles the connection, but its value is fixed, and
12340 never changes. It is only an approximation of how many incoming connections
12341 there actually are, because many other connections may come and go while a
12342 single connection is being processed. When a child process terminates, the
12343 daemon decrements its copy of the variable.
12345 .vitem "&$sn0$& &-- &$sn9$&"
12346 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
12347 that were current at the end of the system filter file. This allows a system
12348 filter file to set values that can be tested in users' filter files. For
12349 example, a system filter could set a value indicating how likely it is that a
12350 message is junk mail.
12352 .vitem &$spam_$&&'xxx'&
12353 A number of variables whose names start with &$spam$& are available when Exim
12354 is compiled with the content-scanning extension. For details, see section
12355 &<<SECTscanspamass>>&.
12358 .vitem &$spool_directory$&
12359 .vindex "&$spool_directory$&"
12360 The name of Exim's spool directory.
12362 .vitem &$spool_inodes$&
12363 .vindex "&$spool_inodes$&"
12364 The number of free inodes in the disk partition where Exim's spool files are
12365 being written. The value is recalculated whenever the variable is referenced.
12366 If the relevant file system does not have the concept of inodes, the value of
12367 is -1. See also the &%check_spool_inodes%& option.
12369 .vitem &$spool_space$&
12370 .vindex "&$spool_space$&"
12371 The amount of free space (as a number of kilobytes) in the disk partition where
12372 Exim's spool files are being written. The value is recalculated whenever the
12373 variable is referenced. If the operating system does not have the ability to
12374 find the amount of free space (only true for experimental systems), the space
12375 value is -1. For example, to check in an ACL that there is at least 50
12376 megabytes free on the spool, you could write:
12378 condition = ${if > {$spool_space}{50000}}
12380 See also the &%check_spool_space%& option.
12383 .vitem &$thisaddress$&
12384 .vindex "&$thisaddress$&"
12385 This variable is set only during the processing of the &%foranyaddress%&
12386 command in a filter file. Its use is explained in the description of that
12387 command, which can be found in the separate document entitled &'Exim's
12388 interfaces to mail filtering'&.
12390 .vitem &$tls_in_bits$&
12391 .vindex "&$tls_in_bits$&"
12392 Contains an approximation of the TLS cipher's bit-strength
12393 on the inbound connection; the meaning of
12394 this depends upon the TLS implementation used.
12395 If TLS has not been negotiated, the value will be 0.
12396 The value of this is automatically fed into the Cyrus SASL authenticator
12397 when acting as a server, to specify the "external SSF" (a SASL term).
12399 The deprecated &$tls_bits$& variable refers to the inbound side
12400 except when used in the context of an outbound SMTP delivery, when it refers to
12403 .vitem &$tls_out_bits$&
12404 .vindex "&$tls_out_bits$&"
12405 Contains an approximation of the TLS cipher's bit-strength
12406 on an outbound SMTP connection; the meaning of
12407 this depends upon the TLS implementation used.
12408 If TLS has not been negotiated, the value will be 0.
12410 .vitem &$tls_in_ourcert$&
12411 .vindex "&$tls_in_ourcert$&"
12412 This variable refers to the certificate presented to the peer of an
12413 inbound connection when the message was received.
12414 It is only useful as the argument of a
12416 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12418 or a &%def%& condition.
12420 .vitem &$tls_in_peercert$&
12421 .vindex "&$tls_in_peercert$&"
12422 This variable refers to the certificate presented by the peer of an
12423 inbound connection when the message was received.
12424 It is only useful as the argument of a
12426 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12428 or a &%def%& condition.
12430 .vitem &$tls_out_ourcert$&
12431 .vindex "&$tls_out_ourcert$&"
12432 This variable refers to the certificate presented to the peer of an
12433 outbound connection. It is only useful as the argument of a
12435 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12437 or a &%def%& condition.
12439 .vitem &$tls_out_peercert$&
12440 .vindex "&$tls_out_peercert$&"
12441 This variable refers to the certificate presented by the peer of an
12442 outbound connection. It is only useful as the argument of a
12444 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12446 or a &%def%& condition.
12448 .vitem &$tls_in_certificate_verified$&
12449 .vindex "&$tls_in_certificate_verified$&"
12450 This variable is set to &"1"& if a TLS certificate was verified when the
12451 message was received, and &"0"& otherwise.
12453 The deprecated &$tls_certificate_verfied$& variable refers to the inbound side
12454 except when used in the context of an outbound SMTP delivery, when it refers to
12457 .vitem &$tls_out_certificate_verified$&
12458 .vindex "&$tls_out_certificate_verified$&"
12459 This variable is set to &"1"& if a TLS certificate was verified when an
12460 outbound SMTP connection was made,
12461 and &"0"& otherwise.
12463 .vitem &$tls_in_cipher$&
12464 .vindex "&$tls_in_cipher$&"
12465 .vindex "&$tls_cipher$&"
12466 When a message is received from a remote host over an encrypted SMTP
12467 connection, this variable is set to the cipher suite that was negotiated, for
12468 example DES-CBC3-SHA. In other circumstances, in particular, for message
12469 received over unencrypted connections, the variable is empty. Testing
12470 &$tls_cipher$& for emptiness is one way of distinguishing between encrypted and
12471 non-encrypted connections during ACL processing.
12473 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
12474 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
12475 becomes the same as &$tls_out_cipher$&.
12477 .vitem &$tls_out_cipher$&
12478 .vindex "&$tls_out_cipher$&"
12480 cleared before any outgoing SMTP connection is made,
12481 and then set to the outgoing cipher suite if one is negotiated. See chapter
12482 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
12483 details of the &(smtp)& transport.
12485 .vitem &$tls_in_ocsp$&
12486 .vindex "&$tls_in_ocsp$&"
12487 When a message is received from a remote client connection
12488 the result of any OCSP request from the client is encoded in this variable:
12490 0 OCSP proof was not requested (default value)
12491 1 No response to request
12492 2 Response not verified
12493 3 Verification failed
12494 4 Verification succeeded
12497 .vitem &$tls_out_ocsp$&
12498 .vindex "&$tls_out_ocsp$&"
12499 When a message is sent to a remote host connection
12500 the result of any OCSP request made is encoded in this variable.
12501 See &$tls_in_ocsp$& for values.
12503 .vitem &$tls_in_peerdn$&
12504 .vindex "&$tls_in_peerdn$&"
12505 .vindex "&$tls_peerdn$&"
12506 When a message is received from a remote host over an encrypted SMTP
12507 connection, and Exim is configured to request a certificate from the client,
12508 the value of the Distinguished Name of the certificate is made available in the
12509 &$tls_in_peerdn$& during subsequent processing.
12511 The deprecated &$tls_peerdn$& variable refers to the inbound side
12512 except when used in the context of an outbound SMTP delivery, when it refers to
12515 .vitem &$tls_out_peerdn$&
12516 .vindex "&$tls_out_peerdn$&"
12517 When a message is being delivered to a remote host over an encrypted SMTP
12518 connection, and Exim is configured to request a certificate from the server,
12519 the value of the Distinguished Name of the certificate is made available in the
12520 &$tls_out_peerdn$& during subsequent processing.
12522 .vitem &$tls_in_sni$&
12523 .vindex "&$tls_in_sni$&"
12524 .vindex "&$tls_sni$&"
12525 .cindex "TLS" "Server Name Indication"
12526 When a TLS session is being established, if the client sends the Server
12527 Name Indication extension, the value will be placed in this variable.
12528 If the variable appears in &%tls_certificate%& then this option and
12529 some others, described in &<<SECTtlssni>>&,
12530 will be re-expanded early in the TLS session, to permit
12531 a different certificate to be presented (and optionally a different key to be
12532 used) to the client, based upon the value of the SNI extension.
12534 The deprecated &$tls_sni$& variable refers to the inbound side
12535 except when used in the context of an outbound SMTP delivery, when it refers to
12538 .vitem &$tls_out_sni$&
12539 .vindex "&$tls_out_sni$&"
12540 .cindex "TLS" "Server Name Indication"
12542 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
12545 .vitem &$tod_bsdinbox$&
12546 .vindex "&$tod_bsdinbox$&"
12547 The time of day and the date, in the format required for BSD-style mailbox
12548 files, for example: Thu Oct 17 17:14:09 1995.
12550 .vitem &$tod_epoch$&
12551 .vindex "&$tod_epoch$&"
12552 The time and date as a number of seconds since the start of the Unix epoch.
12554 .vitem &$tod_epoch_l$&
12555 .vindex "&$tod_epoch_l$&"
12556 The time and date as a number of microseconds since the start of the Unix epoch.
12558 .vitem &$tod_full$&
12559 .vindex "&$tod_full$&"
12560 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
12561 +0100. The timezone is always given as a numerical offset from UTC, with
12562 positive values used for timezones that are ahead (east) of UTC, and negative
12563 values for those that are behind (west).
12566 .vindex "&$tod_log$&"
12567 The time and date in the format used for writing Exim's log files, for example:
12568 1995-10-12 15:32:29, but without a timezone.
12570 .vitem &$tod_logfile$&
12571 .vindex "&$tod_logfile$&"
12572 This variable contains the date in the format yyyymmdd. This is the format that
12573 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
12576 .vitem &$tod_zone$&
12577 .vindex "&$tod_zone$&"
12578 This variable contains the numerical value of the local timezone, for example:
12581 .vitem &$tod_zulu$&
12582 .vindex "&$tod_zulu$&"
12583 This variable contains the UTC date and time in &"Zulu"& format, as specified
12584 by ISO 8601, for example: 20030221154023Z.
12586 .vitem &$transport_name$&
12587 .cindex "transport" "name"
12588 .cindex "name" "of transport"
12589 .vindex "&$transport_name$&"
12590 During the running of a transport, this variable contains its name.
12593 .vindex "&$value$&"
12594 This variable contains the result of an expansion lookup, extraction operation,
12595 or external command, as described above. It is also used during a
12596 &*reduce*& expansion.
12598 .vitem &$verify_mode$&
12599 .vindex "&$verify_mode$&"
12600 While a router or transport is being run in verify mode
12601 or for cutthrough delivery,
12602 contains "S" for sender-verification or "R" for recipient-verification.
12605 .vitem &$version_number$&
12606 .vindex "&$version_number$&"
12607 The version number of Exim.
12609 .vitem &$warn_message_delay$&
12610 .vindex "&$warn_message_delay$&"
12611 This variable is set only during the creation of a message warning about a
12612 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
12614 .vitem &$warn_message_recipients$&
12615 .vindex "&$warn_message_recipients$&"
12616 This variable is set only during the creation of a message warning about a
12617 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
12623 . ////////////////////////////////////////////////////////////////////////////
12624 . ////////////////////////////////////////////////////////////////////////////
12626 .chapter "Embedded Perl" "CHAPperl"
12627 .scindex IIDperl "Perl" "calling from Exim"
12628 Exim can be built to include an embedded Perl interpreter. When this is done,
12629 Perl subroutines can be called as part of the string expansion process. To make
12630 use of the Perl support, you need version 5.004 or later of Perl installed on
12631 your system. To include the embedded interpreter in the Exim binary, include
12636 in your &_Local/Makefile_& and then build Exim in the normal way.
12639 .section "Setting up so Perl can be used" "SECID85"
12640 .oindex "&%perl_startup%&"
12641 Access to Perl subroutines is via a global configuration option called
12642 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
12643 no &%perl_startup%& option in the Exim configuration file then no Perl
12644 interpreter is started and there is almost no overhead for Exim (since none of
12645 the Perl library will be paged in unless used). If there is a &%perl_startup%&
12646 option then the associated value is taken to be Perl code which is executed in
12647 a newly created Perl interpreter.
12649 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
12650 need backslashes before any characters to escape special meanings. The option
12651 should usually be something like
12653 perl_startup = do '/etc/exim.pl'
12655 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
12656 use from Exim. Exim can be configured either to start up a Perl interpreter as
12657 soon as it is entered, or to wait until the first time it is needed. Starting
12658 the interpreter at the beginning ensures that it is done while Exim still has
12659 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
12660 fact used in a particular run. Also, note that this does not mean that Exim is
12661 necessarily running as root when Perl is called at a later time. By default,
12662 the interpreter is started only when it is needed, but this can be changed in
12666 .oindex "&%perl_at_start%&"
12667 Setting &%perl_at_start%& (a boolean option) in the configuration requests
12668 a startup when Exim is entered.
12670 The command line option &%-ps%& also requests a startup when Exim is entered,
12671 overriding the setting of &%perl_at_start%&.
12674 There is also a command line option &%-pd%& (for delay) which suppresses the
12675 initial startup, even if &%perl_at_start%& is set.
12678 .section "Calling Perl subroutines" "SECID86"
12679 When the configuration file includes a &%perl_startup%& option you can make use
12680 of the string expansion item to call the Perl subroutines that are defined
12681 by the &%perl_startup%& code. The operator is used in any of the following
12685 ${perl{foo}{argument}}
12686 ${perl{foo}{argument1}{argument2} ... }
12688 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
12689 arguments may be passed. Passing more than this results in an expansion failure
12690 with an error message of the form
12692 Too many arguments passed to Perl subroutine "foo" (max is 8)
12694 The return value of the Perl subroutine is evaluated in a scalar context before
12695 it is passed back to Exim to be inserted into the expanded string. If the
12696 return value is &'undef'&, the expansion is forced to fail in the same way as
12697 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
12698 by obeying Perl's &%die%& function, the expansion fails with the error message
12699 that was passed to &%die%&.
12702 .section "Calling Exim functions from Perl" "SECID87"
12703 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
12704 is available to call back into Exim's string expansion function. For example,
12707 my $lp = Exim::expand_string('$local_part');
12709 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
12710 Note those are single quotes and not double quotes to protect against
12711 &$local_part$& being interpolated as a Perl variable.
12713 If the string expansion is forced to fail by a &"fail"& item, the result of
12714 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
12715 expansion string, the Perl call from the original expansion string fails with
12716 an appropriate error message, in the same way as if &%die%& were used.
12718 .cindex "debugging" "from embedded Perl"
12719 .cindex "log" "writing from embedded Perl"
12720 Two other Exim functions are available for use from within Perl code.
12721 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
12722 debugging is enabled. If you want a newline at the end, you must supply it.
12723 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
12724 timestamp. In this case, you should not supply a terminating newline.
12727 .section "Use of standard output and error by Perl" "SECID88"
12728 .cindex "Perl" "standard output and error"
12729 You should not write to the standard error or output streams from within your
12730 Perl code, as it is not defined how these are set up. In versions of Exim
12731 before 4.50, it is possible for the standard output or error to refer to the
12732 SMTP connection during message reception via the daemon. Writing to this stream
12733 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
12734 error streams are connected to &_/dev/null_& in the daemon. The chaos is
12735 avoided, but the output is lost.
12737 .cindex "Perl" "use of &%warn%&"
12738 The Perl &%warn%& statement writes to the standard error stream by default.
12739 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
12740 you have no control. When Exim starts up the Perl interpreter, it arranges for
12741 output from the &%warn%& statement to be written to the Exim main log. You can
12742 change this by including appropriate Perl magic somewhere in your Perl code.
12743 For example, to discard &%warn%& output completely, you need this:
12745 $SIG{__WARN__} = sub { };
12747 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
12748 example, the code for the subroutine is empty, so it does nothing, but you can
12749 include any Perl code that you like. The text of the &%warn%& message is passed
12750 as the first subroutine argument.
12754 . ////////////////////////////////////////////////////////////////////////////
12755 . ////////////////////////////////////////////////////////////////////////////
12757 .chapter "Starting the daemon and the use of network interfaces" &&&
12758 "CHAPinterfaces" &&&
12759 "Starting the daemon"
12760 .cindex "daemon" "starting"
12761 .cindex "interface" "listening"
12762 .cindex "network interface"
12763 .cindex "interface" "network"
12764 .cindex "IP address" "for listening"
12765 .cindex "daemon" "listening IP addresses"
12766 .cindex "TCP/IP" "setting listening interfaces"
12767 .cindex "TCP/IP" "setting listening ports"
12768 A host that is connected to a TCP/IP network may have one or more physical
12769 hardware network interfaces. Each of these interfaces may be configured as one
12770 or more &"logical"& interfaces, which are the entities that a program actually
12771 works with. Each of these logical interfaces is associated with an IP address.
12772 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
12773 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
12774 knowledge about the host's interfaces for use in three different circumstances:
12777 When a listening daemon is started, Exim needs to know which interfaces
12778 and ports to listen on.
12780 When Exim is routing an address, it needs to know which IP addresses
12781 are associated with local interfaces. This is required for the correct
12782 processing of MX lists by removing the local host and others with the
12783 same or higher priority values. Also, Exim needs to detect cases
12784 when an address is routed to an IP address that in fact belongs to the
12785 local host. Unless the &%self%& router option or the &%allow_localhost%&
12786 option of the smtp transport is set (as appropriate), this is treated
12787 as an error situation.
12789 When Exim connects to a remote host, it may need to know which interface to use
12790 for the outgoing connection.
12794 Exim's default behaviour is likely to be appropriate in the vast majority
12795 of cases. If your host has only one interface, and you want all its IP
12796 addresses to be treated in the same way, and you are using only the
12797 standard SMTP port, you should not need to take any special action. The
12798 rest of this chapter does not apply to you.
12800 In a more complicated situation you may want to listen only on certain
12801 interfaces, or on different ports, and for this reason there are a number of
12802 options that can be used to influence Exim's behaviour. The rest of this
12803 chapter describes how they operate.
12805 When a message is received over TCP/IP, the interface and port that were
12806 actually used are set in &$received_ip_address$& and &$received_port$&.
12810 .section "Starting a listening daemon" "SECID89"
12811 When a listening daemon is started (by means of the &%-bd%& command line
12812 option), the interfaces and ports on which it listens are controlled by the
12816 &%daemon_smtp_ports%& contains a list of default ports
12818 (For backward compatibility, this option can also be specified in the singular.)
12820 &%local_interfaces%& contains list of interface IP addresses on which to
12821 listen. Each item may optionally also specify a port.
12824 The default list separator in both cases is a colon, but this can be changed as
12825 described in section &<<SECTlistconstruct>>&. When IPv6 addresses are involved,
12826 it is usually best to change the separator to avoid having to double all the
12827 colons. For example:
12829 local_interfaces = <; 127.0.0.1 ; \
12832 3ffe:ffff:836f::fe86:a061
12834 There are two different formats for specifying a port along with an IP address
12835 in &%local_interfaces%&:
12838 The port is added onto the address with a dot separator. For example, to listen
12839 on port 1234 on two different IP addresses:
12841 local_interfaces = <; 192.168.23.65.1234 ; \
12842 3ffe:ffff:836f::fe86:a061.1234
12845 The IP address is enclosed in square brackets, and the port is added
12846 with a colon separator, for example:
12848 local_interfaces = <; [192.168.23.65]:1234 ; \
12849 [3ffe:ffff:836f::fe86:a061]:1234
12853 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
12854 default setting contains just one port:
12856 daemon_smtp_ports = smtp
12858 If more than one port is listed, each interface that does not have its own port
12859 specified listens on all of them. Ports that are listed in
12860 &%daemon_smtp_ports%& can be identified either by name (defined in
12861 &_/etc/services_&) or by number. However, when ports are given with individual
12862 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
12866 .section "Special IP listening addresses" "SECID90"
12867 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
12868 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
12869 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
12870 instead of setting up separate listening sockets for each interface. The
12871 default value of &%local_interfaces%& is
12873 local_interfaces = 0.0.0.0
12875 when Exim is built without IPv6 support; otherwise it is:
12877 local_interfaces = <; ::0 ; 0.0.0.0
12879 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
12883 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
12884 The &%-oX%& command line option can be used to override the values of
12885 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
12886 instance. Another way of doing this would be to use macros and the &%-D%&
12887 option. However, &%-oX%& can be used by any admin user, whereas modification of
12888 the runtime configuration by &%-D%& is allowed only when the caller is root or
12891 The value of &%-oX%& is a list of items. The default colon separator can be
12892 changed in the usual way if required. If there are any items that do not
12893 contain dots or colons (that is, are not IP addresses), the value of
12894 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
12895 items that do contain dots or colons, the value of &%local_interfaces%& is
12896 replaced by those items. Thus, for example,
12900 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
12903 -oX 192.168.34.5.1125
12905 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
12906 (However, since &%local_interfaces%& now contains no items without ports, the
12907 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
12911 .section "Support for the obsolete SSMTP (or SMTPS) protocol" "SECTsupobssmt"
12912 .cindex "ssmtp protocol"
12913 .cindex "smtps protocol"
12914 .cindex "SMTP" "ssmtp protocol"
12915 .cindex "SMTP" "smtps protocol"
12916 Exim supports the obsolete SSMTP protocol (also known as SMTPS) that was used
12917 before the STARTTLS command was standardized for SMTP. Some legacy clients
12918 still use this protocol. If the &%tls_on_connect_ports%& option is set to a
12919 list of port numbers or service names,
12920 connections to those ports must use SSMTP. The most
12921 common use of this option is expected to be
12923 tls_on_connect_ports = 465
12925 because 465 is the usual port number used by the legacy clients. There is also
12926 a command line option &%-tls-on-connect%&, which forces all ports to behave in
12927 this way when a daemon is started.
12929 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
12930 daemon to listen on those ports. You must still specify them in
12931 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
12932 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
12933 connections via the daemon.)
12938 .section "IPv6 address scopes" "SECID92"
12939 .cindex "IPv6" "address scopes"
12940 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
12941 can, in principle, have the same link-local IPv6 address on different
12942 interfaces. Thus, additional information is needed, over and above the IP
12943 address, to distinguish individual interfaces. A convention of using a
12944 percent sign followed by something (often the interface name) has been
12945 adopted in some cases, leading to addresses like this:
12947 fe80::202:b3ff:fe03:45c1%eth0
12949 To accommodate this usage, a percent sign followed by an arbitrary string is
12950 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
12951 to convert a textual IPv6 address for actual use. This function recognizes the
12952 percent convention in operating systems that support it, and it processes the
12953 address appropriately. Unfortunately, some older libraries have problems with
12954 &[getaddrinfo()]&. If
12956 IPV6_USE_INET_PTON=yes
12958 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
12959 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
12960 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
12961 function.) Of course, this means that the additional functionality of
12962 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
12964 .section "Disabling IPv6" "SECID93"
12965 .cindex "IPv6" "disabling"
12966 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
12967 run on a host whose kernel does not support IPv6. The binary will fall back to
12968 using IPv4, but it may waste resources looking up AAAA records, and trying to
12969 connect to IPv6 addresses, causing delays to mail delivery. If you set the
12970 .oindex "&%disable_ipv6%&"
12971 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
12972 activities take place. AAAA records are never looked up, and any IPv6 addresses
12973 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
12974 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
12975 to handle IPv6 literal addresses.
12977 On the other hand, when IPv6 is in use, there may be times when you want to
12978 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
12979 option to globally suppress the lookup of AAAA records for specified domains,
12980 and you can use the &%ignore_target_hosts%& generic router option to ignore
12981 IPv6 addresses in an individual router.
12985 .section "Examples of starting a listening daemon" "SECID94"
12986 The default case in an IPv6 environment is
12988 daemon_smtp_ports = smtp
12989 local_interfaces = <; ::0 ; 0.0.0.0
12991 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
12992 Either one or two sockets may be used, depending on the characteristics of
12993 the TCP/IP stack. (This is complicated and messy; for more information,
12994 read the comments in the &_daemon.c_& source file.)
12996 To specify listening on ports 25 and 26 on all interfaces:
12998 daemon_smtp_ports = 25 : 26
13000 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
13002 local_interfaces = <; ::0.25 ; ::0.26 \
13003 0.0.0.0.25 ; 0.0.0.0.26
13005 To listen on the default port on all IPv4 interfaces, and on port 26 on the
13006 IPv4 loopback address only:
13008 local_interfaces = 0.0.0.0 : 127.0.0.1.26
13010 To specify listening on the default port on specific interfaces only:
13012 local_interfaces = 10.0.0.67 : 192.168.34.67
13014 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
13018 .section "Recognizing the local host" "SECTreclocipadd"
13019 The &%local_interfaces%& option is also used when Exim needs to determine
13020 whether or not an IP address refers to the local host. That is, the IP
13021 addresses of all the interfaces on which a daemon is listening are always
13024 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
13025 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
13026 available interfaces from the operating system, and extracts the relevant
13027 (that is, IPv4 or IPv6) addresses to use for checking.
13029 Some systems set up large numbers of virtual interfaces in order to provide
13030 many virtual web servers. In this situation, you may want to listen for
13031 email on only a few of the available interfaces, but nevertheless treat all
13032 interfaces as local when routing. You can do this by setting
13033 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
13034 &"all"& wildcard values. These addresses are recognized as local, but are not
13035 used for listening. Consider this example:
13037 local_interfaces = <; 127.0.0.1 ; ::1 ; \
13039 3ffe:2101:12:1:a00:20ff:fe86:a061
13041 extra_local_interfaces = <; ::0 ; 0.0.0.0
13043 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
13044 address, but all available interface addresses are treated as local when
13047 In some environments the local host name may be in an MX list, but with an IP
13048 address that is not assigned to any local interface. In other cases it may be
13049 desirable to treat other host names as if they referred to the local host. Both
13050 these cases can be handled by setting the &%hosts_treat_as_local%& option.
13051 This contains host names rather than IP addresses. When a host is referenced
13052 during routing, either via an MX record or directly, it is treated as the local
13053 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
13054 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
13058 .section "Delivering to a remote host" "SECID95"
13059 Delivery to a remote host is handled by the smtp transport. By default, it
13060 allows the system's TCP/IP functions to choose which interface to use (if
13061 there is more than one) when connecting to a remote host. However, the
13062 &%interface%& option can be set to specify which interface is used. See the
13063 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
13069 . ////////////////////////////////////////////////////////////////////////////
13070 . ////////////////////////////////////////////////////////////////////////////
13072 .chapter "Main configuration" "CHAPmainconfig"
13073 .scindex IIDconfima "configuration file" "main section"
13074 .scindex IIDmaiconf "main configuration"
13075 The first part of the run time configuration file contains three types of item:
13078 Macro definitions: These lines start with an upper case letter. See section
13079 &<<SECTmacrodefs>>& for details of macro processing.
13081 Named list definitions: These lines start with one of the words &"domainlist"&,
13082 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
13083 section &<<SECTnamedlists>>&.
13085 Main configuration settings: Each setting occupies one line of the file
13086 (with possible continuations). If any setting is preceded by the word
13087 &"hide"&, the &%-bP%& command line option displays its value to admin users
13088 only. See section &<<SECTcos>>& for a description of the syntax of these option
13092 This chapter specifies all the main configuration options, along with their
13093 types and default values. For ease of finding a particular option, they appear
13094 in alphabetical order in section &<<SECTalomo>>& below. However, because there
13095 are now so many options, they are first listed briefly in functional groups, as
13096 an aid to finding the name of the option you are looking for. Some options are
13097 listed in more than one group.
13099 .section "Miscellaneous" "SECID96"
13101 .row &%bi_command%& "to run for &%-bi%& command line option"
13102 .row &%disable_ipv6%& "do no IPv6 processing"
13103 .row &%keep_malformed%& "for broken files &-- should not happen"
13104 .row &%localhost_number%& "for unique message ids in clusters"
13105 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
13106 .row &%message_body_visible%& "how much to show in &$message_body$&"
13107 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
13108 .row &%print_topbitchars%& "top-bit characters are printing"
13109 .row &%timezone%& "force time zone"
13113 .section "Exim parameters" "SECID97"
13115 .row &%exim_group%& "override compiled-in value"
13116 .row &%exim_path%& "override compiled-in value"
13117 .row &%exim_user%& "override compiled-in value"
13118 .row &%primary_hostname%& "default from &[uname()]&"
13119 .row &%split_spool_directory%& "use multiple directories"
13120 .row &%spool_directory%& "override compiled-in value"
13125 .section "Privilege controls" "SECID98"
13127 .row &%admin_groups%& "groups that are Exim admin users"
13128 .row &%deliver_drop_privilege%& "drop root for delivery processes"
13129 .row &%local_from_check%& "insert &'Sender:'& if necessary"
13130 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
13131 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
13132 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
13133 .row &%never_users%& "do not run deliveries as these"
13134 .row &%prod_requires_admin%& "forced delivery requires admin user"
13135 .row &%queue_list_requires_admin%& "queue listing requires admin user"
13136 .row &%trusted_groups%& "groups that are trusted"
13137 .row &%trusted_users%& "users that are trusted"
13142 .section "Logging" "SECID99"
13144 .row &%hosts_connection_nolog%& "exemption from connect logging"
13145 .row &%log_file_path%& "override compiled-in value"
13146 .row &%log_selector%& "set/unset optional logging"
13147 .row &%log_timezone%& "add timezone to log lines"
13148 .row &%message_logs%& "create per-message logs"
13149 .row &%preserve_message_logs%& "after message completion"
13150 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
13151 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
13152 .row &%syslog_facility%& "set syslog &""facility""& field"
13153 .row &%syslog_processname%& "set syslog &""ident""& field"
13154 .row &%syslog_timestamp%& "timestamp syslog lines"
13155 .row &%write_rejectlog%& "control use of message log"
13160 .section "Frozen messages" "SECID100"
13162 .row &%auto_thaw%& "sets time for retrying frozen messages"
13163 .row &%freeze_tell%& "send message when freezing"
13164 .row &%move_frozen_messages%& "to another directory"
13165 .row &%timeout_frozen_after%& "keep frozen messages only so long"
13170 .section "Data lookups" "SECID101"
13172 .row &%ibase_servers%& "InterBase servers"
13173 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
13174 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
13175 .row &%ldap_cert_file%& "client cert file for LDAP"
13176 .row &%ldap_cert_key%& "client key file for LDAP"
13177 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
13178 .row &%ldap_default_servers%& "used if no server in query"
13179 .row &%ldap_require_cert%& "action to take without LDAP server cert"
13180 .row &%ldap_start_tls%& "require TLS within LDAP"
13181 .row &%ldap_version%& "set protocol version"
13182 .row &%lookup_open_max%& "lookup files held open"
13183 .row &%mysql_servers%& "default MySQL servers"
13184 .row &%oracle_servers%& "Oracle servers"
13185 .row &%pgsql_servers%& "default PostgreSQL servers"
13186 .row &%sqlite_lock_timeout%& "as it says"
13191 .section "Message ids" "SECID102"
13193 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
13194 .row &%message_id_header_text%& "ditto"
13199 .section "Embedded Perl Startup" "SECID103"
13201 .row &%perl_at_start%& "always start the interpreter"
13202 .row &%perl_startup%& "code to obey when starting Perl"
13207 .section "Daemon" "SECID104"
13209 .row &%daemon_smtp_ports%& "default ports"
13210 .row &%daemon_startup_retries%& "number of times to retry"
13211 .row &%daemon_startup_sleep%& "time to sleep between tries"
13212 .row &%extra_local_interfaces%& "not necessarily listened on"
13213 .row &%local_interfaces%& "on which to listen, with optional ports"
13214 .row &%pid_file_path%& "override compiled-in value"
13215 .row &%queue_run_max%& "maximum simultaneous queue runners"
13220 .section "Resource control" "SECID105"
13222 .row &%check_log_inodes%& "before accepting a message"
13223 .row &%check_log_space%& "before accepting a message"
13224 .row &%check_spool_inodes%& "before accepting a message"
13225 .row &%check_spool_space%& "before accepting a message"
13226 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
13227 .row &%queue_only_load%& "queue incoming if load high"
13228 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
13229 .row &%queue_run_max%& "maximum simultaneous queue runners"
13230 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
13231 .row &%smtp_accept_max%& "simultaneous incoming connections"
13232 .row &%smtp_accept_max_nonmail%& "non-mail commands"
13233 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
13234 .row &%smtp_accept_max_per_connection%& "messages per connection"
13235 .row &%smtp_accept_max_per_host%& "connections from one host"
13236 .row &%smtp_accept_queue%& "queue mail if more connections"
13237 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
13239 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
13240 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
13241 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
13242 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
13243 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
13248 .section "Policy controls" "SECID106"
13250 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
13251 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
13252 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
13253 .row &%acl_smtp_auth%& "ACL for AUTH"
13254 .row &%acl_smtp_connect%& "ACL for connection"
13255 .row &%acl_smtp_data%& "ACL for DATA"
13256 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
13257 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
13258 .row &%acl_smtp_etrn%& "ACL for ETRN"
13259 .row &%acl_smtp_expn%& "ACL for EXPN"
13260 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
13261 .row &%acl_smtp_mail%& "ACL for MAIL"
13262 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
13263 .row &%acl_smtp_mime%& "ACL for MIME parts"
13264 .row &%acl_smtp_predata%& "ACL for start of data"
13265 .row &%acl_smtp_quit%& "ACL for QUIT"
13266 .row &%acl_smtp_rcpt%& "ACL for RCPT"
13267 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
13268 .row &%acl_smtp_vrfy%& "ACL for VRFY"
13269 .row &%av_scanner%& "specify virus scanner"
13270 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
13272 .row &%dns_csa_search_limit%& "control CSA parent search depth"
13273 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
13274 .row &%header_maxsize%& "total size of message header"
13275 .row &%header_line_maxsize%& "individual header line limit"
13276 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
13277 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
13278 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
13279 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
13280 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
13281 .row &%host_lookup%& "host name looked up for these hosts"
13282 .row &%host_lookup_order%& "order of DNS and local name lookups"
13283 .row &%host_reject_connection%& "reject connection from these hosts"
13284 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
13285 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
13286 .row &%message_size_limit%& "for all messages"
13287 .row &%percent_hack_domains%& "recognize %-hack for these domains"
13288 .row &%spamd_address%& "set interface to SpamAssassin"
13289 .row &%strict_acl_vars%& "object to unset ACL variables"
13294 .section "Callout cache" "SECID107"
13296 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
13298 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
13300 .row &%callout_negative_expire%& "timeout for negative address cache item"
13301 .row &%callout_positive_expire%& "timeout for positive address cache item"
13302 .row &%callout_random_local_part%& "string to use for &""random""& testing"
13307 .section "TLS" "SECID108"
13309 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
13310 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
13311 .row &%openssl_options%& "adjust OpenSSL compatibility options"
13312 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
13313 .row &%tls_certificate%& "location of server certificate"
13314 .row &%tls_crl%& "certificate revocation list"
13315 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
13316 .row &%tls_dhparam%& "DH parameters for server"
13317 .row &%tls_ocsp_file%& "location of server certificate status proof"
13318 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
13319 .row &%tls_privatekey%& "location of server private key"
13320 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
13321 .row &%tls_require_ciphers%& "specify acceptable ciphers"
13322 .row &%tls_try_verify_hosts%& "try to verify client certificate"
13323 .row &%tls_verify_certificates%& "expected client certificates"
13324 .row &%tls_verify_hosts%& "insist on client certificate verify"
13329 .section "Local user handling" "SECID109"
13331 .row &%finduser_retries%& "useful in NIS environments"
13332 .row &%gecos_name%& "used when creating &'Sender:'&"
13333 .row &%gecos_pattern%& "ditto"
13334 .row &%max_username_length%& "for systems that truncate"
13335 .row &%unknown_login%& "used when no login name found"
13336 .row &%unknown_username%& "ditto"
13337 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
13338 .row &%uucp_from_sender%& "ditto"
13343 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
13345 .row &%header_maxsize%& "total size of message header"
13346 .row &%header_line_maxsize%& "individual header line limit"
13347 .row &%message_size_limit%& "applies to all messages"
13348 .row &%percent_hack_domains%& "recognize %-hack for these domains"
13349 .row &%received_header_text%& "expanded to make &'Received:'&"
13350 .row &%received_headers_max%& "for mail loop detection"
13351 .row &%recipients_max%& "limit per message"
13352 .row &%recipients_max_reject%& "permanently reject excess recipients"
13358 .section "Non-SMTP incoming messages" "SECID111"
13360 .row &%receive_timeout%& "for non-SMTP messages"
13367 .section "Incoming SMTP messages" "SECID112"
13368 See also the &'Policy controls'& section above.
13371 .row &%host_lookup%& "host name looked up for these hosts"
13372 .row &%host_lookup_order%& "order of DNS and local name lookups"
13373 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
13374 .row &%rfc1413_hosts%& "make ident calls to these hosts"
13375 .row &%rfc1413_query_timeout%& "zero disables ident calls"
13376 .row &%sender_unqualified_hosts%& "may send unqualified senders"
13377 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
13378 .row &%smtp_accept_max%& "simultaneous incoming connections"
13379 .row &%smtp_accept_max_nonmail%& "non-mail commands"
13380 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
13381 .row &%smtp_accept_max_per_connection%& "messages per connection"
13382 .row &%smtp_accept_max_per_host%& "connections from one host"
13383 .row &%smtp_accept_queue%& "queue mail if more connections"
13384 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
13386 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
13387 .row &%smtp_active_hostname%& "host name to use in messages"
13388 .row &%smtp_banner%& "text for welcome banner"
13389 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
13390 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
13391 .row &%smtp_enforce_sync%& "of SMTP command/responses"
13392 .row &%smtp_etrn_command%& "what to run for ETRN"
13393 .row &%smtp_etrn_serialize%& "only one at once"
13394 .row &%smtp_load_reserve%& "only reserve hosts if this load"
13395 .row &%smtp_max_unknown_commands%& "before dropping connection"
13396 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
13397 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
13398 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
13399 .row &%smtp_receive_timeout%& "per command or data line"
13400 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
13401 .row &%smtp_return_error_details%& "give detail on rejections"
13406 .section "SMTP extensions" "SECID113"
13408 .row &%accept_8bitmime%& "advertise 8BITMIME"
13409 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
13410 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
13411 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
13412 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
13413 .row &%prdr_enable%& "advertise PRDR to all hosts"
13414 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
13419 .section "Processing messages" "SECID114"
13421 .row &%allow_domain_literals%& "recognize domain literal syntax"
13422 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
13423 .row &%allow_utf8_domains%& "in addresses"
13424 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
13426 .row &%delivery_date_remove%& "from incoming messages"
13427 .row &%envelope_to_remove%& "from incoming messages"
13428 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
13429 .row &%headers_charset%& "default for translations"
13430 .row &%qualify_domain%& "default for senders"
13431 .row &%qualify_recipient%& "default for recipients"
13432 .row &%return_path_remove%& "from incoming messages"
13433 .row &%strip_excess_angle_brackets%& "in addresses"
13434 .row &%strip_trailing_dot%& "at end of addresses"
13435 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
13440 .section "System filter" "SECID115"
13442 .row &%system_filter%& "locate system filter"
13443 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
13445 .row &%system_filter_file_transport%& "transport for delivery to a file"
13446 .row &%system_filter_group%& "group for filter running"
13447 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
13448 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
13449 .row &%system_filter_user%& "user for filter running"
13454 .section "Routing and delivery" "SECID116"
13456 .row &%disable_ipv6%& "do no IPv6 processing"
13457 .row &%dns_again_means_nonexist%& "for broken domains"
13458 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
13459 .row &%dns_dnssec_ok%& "parameter for resolver"
13460 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
13461 .row &%dns_retrans%& "parameter for resolver"
13462 .row &%dns_retry%& "parameter for resolver"
13463 .row &%dns_use_edns0%& "parameter for resolver"
13464 .row &%hold_domains%& "hold delivery for these domains"
13465 .row &%local_interfaces%& "for routing checks"
13466 .row &%queue_domains%& "no immediate delivery for these"
13467 .row &%queue_only%& "no immediate delivery at all"
13468 .row &%queue_only_file%& "no immediate delivery if file exists"
13469 .row &%queue_only_load%& "no immediate delivery if load is high"
13470 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
13471 .row &%queue_only_override%& "allow command line to override"
13472 .row &%queue_run_in_order%& "order of arrival"
13473 .row &%queue_run_max%& "of simultaneous queue runners"
13474 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
13475 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
13476 .row &%remote_sort_domains%& "order of remote deliveries"
13477 .row &%retry_data_expire%& "timeout for retry data"
13478 .row &%retry_interval_max%& "safety net for retry rules"
13483 .section "Bounce and warning messages" "SECID117"
13485 .row &%bounce_message_file%& "content of bounce"
13486 .row &%bounce_message_text%& "content of bounce"
13487 .row &%bounce_return_body%& "include body if returning message"
13488 .row &%bounce_return_message%& "include original message in bounce"
13489 .row &%bounce_return_size_limit%& "limit on returned message"
13490 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
13491 .row &%dsn_from%& "set &'From:'& contents in bounces"
13492 .row &%errors_copy%& "copy bounce messages"
13493 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
13494 .row &%delay_warning%& "time schedule"
13495 .row &%delay_warning_condition%& "condition for warning messages"
13496 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
13497 .row &%smtp_return_error_details%& "give detail on rejections"
13498 .row &%warn_message_file%& "content of warning message"
13503 .section "Alphabetical list of main options" "SECTalomo"
13504 Those options that undergo string expansion before use are marked with
13507 .option accept_8bitmime main boolean true
13509 .cindex "8-bit characters"
13510 .cindex "log" "selectors"
13511 .cindex "log" "8BITMIME"
13512 This option causes Exim to send 8BITMIME in its response to an SMTP
13513 EHLO command, and to accept the BODY= parameter on MAIL commands.
13514 However, though Exim is 8-bit clean, it is not a protocol converter, and it
13515 takes no steps to do anything special with messages received by this route.
13517 Historically Exim kept this option off by default, but the maintainers
13518 feel that in today's Internet, this causes more problems than it solves.
13519 It now defaults to true.
13520 A more detailed analysis of the issues is provided by Dan Bernstein:
13522 &url(http://cr.yp.to/smtp/8bitmime.html)
13525 To log received 8BITMIME status use
13527 log_selector = +8bitmime
13530 .option acl_not_smtp main string&!! unset
13531 .cindex "&ACL;" "for non-SMTP messages"
13532 .cindex "non-SMTP messages" "ACLs for"
13533 This option defines the ACL that is run when a non-SMTP message has been
13534 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
13537 .option acl_not_smtp_mime main string&!! unset
13538 This option defines the ACL that is run for individual MIME parts of non-SMTP
13539 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
13542 .option acl_not_smtp_start main string&!! unset
13543 .cindex "&ACL;" "at start of non-SMTP message"
13544 .cindex "non-SMTP messages" "ACLs for"
13545 This option defines the ACL that is run before Exim starts reading a
13546 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
13548 .option acl_smtp_auth main string&!! unset
13549 .cindex "&ACL;" "setting up for SMTP commands"
13550 .cindex "AUTH" "ACL for"
13551 This option defines the ACL that is run when an SMTP AUTH command is
13552 received. See chapter &<<CHAPACL>>& for further details.
13554 .option acl_smtp_connect main string&!! unset
13555 .cindex "&ACL;" "on SMTP connection"
13556 This option defines the ACL that is run when an SMTP connection is received.
13557 See chapter &<<CHAPACL>>& for further details.
13559 .option acl_smtp_data main string&!! unset
13560 .cindex "DATA" "ACL for"
13561 This option defines the ACL that is run after an SMTP DATA command has been
13562 processed and the message itself has been received, but before the final
13563 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
13565 .option acl_smtp_data_prdr main string&!! accept
13566 .cindex "PRDR" "ACL for"
13567 .cindex "DATA" "PRDR ACL for"
13568 .cindex "&ACL;" "PRDR-related"
13569 .cindex "&ACL;" "per-user data processing"
13570 This option defines the ACL that,
13571 if the PRDR feature has been negotiated,
13572 is run for each recipient after an SMTP DATA command has been
13573 processed and the message itself has been received, but before the
13574 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
13576 .option acl_smtp_etrn main string&!! unset
13577 .cindex "ETRN" "ACL for"
13578 This option defines the ACL that is run when an SMTP ETRN command is
13579 received. See chapter &<<CHAPACL>>& for further details.
13581 .option acl_smtp_expn main string&!! unset
13582 .cindex "EXPN" "ACL for"
13583 This option defines the ACL that is run when an SMTP EXPN command is
13584 received. See chapter &<<CHAPACL>>& for further details.
13586 .option acl_smtp_helo main string&!! unset
13587 .cindex "EHLO" "ACL for"
13588 .cindex "HELO" "ACL for"
13589 This option defines the ACL that is run when an SMTP EHLO or HELO
13590 command is received. See chapter &<<CHAPACL>>& for further details.
13593 .option acl_smtp_mail main string&!! unset
13594 .cindex "MAIL" "ACL for"
13595 This option defines the ACL that is run when an SMTP MAIL command is
13596 received. See chapter &<<CHAPACL>>& for further details.
13598 .option acl_smtp_mailauth main string&!! unset
13599 .cindex "AUTH" "on MAIL command"
13600 This option defines the ACL that is run when there is an AUTH parameter on
13601 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
13602 &<<CHAPSMTPAUTH>>& for details of authentication.
13604 .option acl_smtp_mime main string&!! unset
13605 .cindex "MIME content scanning" "ACL for"
13606 This option is available when Exim is built with the content-scanning
13607 extension. It defines the ACL that is run for each MIME part in a message. See
13608 section &<<SECTscanmimepart>>& for details.
13610 .option acl_smtp_predata main string&!! unset
13611 This option defines the ACL that is run when an SMTP DATA command is
13612 received, before the message itself is received. See chapter &<<CHAPACL>>& for
13615 .option acl_smtp_quit main string&!! unset
13616 .cindex "QUIT, ACL for"
13617 This option defines the ACL that is run when an SMTP QUIT command is
13618 received. See chapter &<<CHAPACL>>& for further details.
13620 .option acl_smtp_rcpt main string&!! unset
13621 .cindex "RCPT" "ACL for"
13622 This option defines the ACL that is run when an SMTP RCPT command is
13623 received. See chapter &<<CHAPACL>>& for further details.
13625 .option acl_smtp_starttls main string&!! unset
13626 .cindex "STARTTLS, ACL for"
13627 This option defines the ACL that is run when an SMTP STARTTLS command is
13628 received. See chapter &<<CHAPACL>>& for further details.
13630 .option acl_smtp_vrfy main string&!! unset
13631 .cindex "VRFY" "ACL for"
13632 This option defines the ACL that is run when an SMTP VRFY command is
13633 received. See chapter &<<CHAPACL>>& for further details.
13635 .option admin_groups main "string list&!!" unset
13636 .cindex "admin user"
13637 This option is expanded just once, at the start of Exim's processing. If the
13638 current group or any of the supplementary groups of an Exim caller is in this
13639 colon-separated list, the caller has admin privileges. If all your system
13640 programmers are in a specific group, for example, you can give them all Exim
13641 admin privileges by putting that group in &%admin_groups%&. However, this does
13642 not permit them to read Exim's spool files (whose group owner is the Exim gid).
13643 To permit this, you have to add individuals to the Exim group.
13645 .option allow_domain_literals main boolean false
13646 .cindex "domain literal"
13647 If this option is set, the RFC 2822 domain literal format is permitted in
13648 email addresses. The option is not set by default, because the domain literal
13649 format is not normally required these days, and few people know about it. It
13650 has, however, been exploited by mail abusers.
13652 Unfortunately, it seems that some DNS black list maintainers are using this
13653 format to report black listing to postmasters. If you want to accept messages
13654 addressed to your hosts by IP address, you need to set
13655 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
13656 domains (defined in the named domain list &%local_domains%& in the default
13657 configuration). This &"magic string"& matches the domain literal form of all
13658 the local host's IP addresses.
13661 .option allow_mx_to_ip main boolean false
13662 .cindex "MX record" "pointing to IP address"
13663 It appears that more and more DNS zone administrators are breaking the rules
13664 and putting domain names that look like IP addresses on the right hand side of
13665 MX records. Exim follows the rules and rejects this, giving an error message
13666 that explains the mis-configuration. However, some other MTAs support this
13667 practice, so to avoid &"Why can't Exim do this?"& complaints,
13668 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
13669 recommended, except when you have no other choice.
13671 .option allow_utf8_domains main boolean false
13672 .cindex "domain" "UTF-8 characters in"
13673 .cindex "UTF-8" "in domain name"
13674 Lots of discussion is going on about internationalized domain names. One
13675 camp is strongly in favour of just using UTF-8 characters, and it seems
13676 that at least two other MTAs permit this. This option allows Exim users to
13677 experiment if they wish.
13679 If it is set true, Exim's domain parsing function allows valid
13680 UTF-8 multicharacters to appear in domain name components, in addition to
13681 letters, digits, and hyphens. However, just setting this option is not
13682 enough; if you want to look up these domain names in the DNS, you must also
13683 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
13684 suitable setting is:
13686 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
13687 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
13689 Alternatively, you can just disable this feature by setting
13691 dns_check_names_pattern =
13693 That is, set the option to an empty string so that no check is done.
13696 .option auth_advertise_hosts main "host list&!!" *
13697 .cindex "authentication" "advertising"
13698 .cindex "AUTH" "advertising"
13699 If any server authentication mechanisms are configured, Exim advertises them in
13700 response to an EHLO command only if the calling host matches this list.
13701 Otherwise, Exim does not advertise AUTH.
13702 Exim does not accept AUTH commands from clients to which it has not
13703 advertised the availability of AUTH. The advertising of individual
13704 authentication mechanisms can be controlled by the use of the
13705 &%server_advertise_condition%& generic authenticator option on the individual
13706 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
13708 Certain mail clients (for example, Netscape) require the user to provide a name
13709 and password for authentication if AUTH is advertised, even though it may
13710 not be needed (the host may accept messages from hosts on its local LAN without
13711 authentication, for example). The &%auth_advertise_hosts%& option can be used
13712 to make these clients more friendly by excluding them from the set of hosts to
13713 which Exim advertises AUTH.
13715 .cindex "AUTH" "advertising when encrypted"
13716 If you want to advertise the availability of AUTH only when the connection
13717 is encrypted using TLS, you can make use of the fact that the value of this
13718 option is expanded, with a setting like this:
13720 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
13722 .vindex "&$tls_in_cipher$&"
13723 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
13724 the expansion is empty, thus matching no hosts. Otherwise, the result of the
13725 expansion is *, which matches all hosts.
13728 .option auto_thaw main time 0s
13729 .cindex "thawing messages"
13730 .cindex "unfreezing messages"
13731 If this option is set to a time greater than zero, a queue runner will try a
13732 new delivery attempt on any frozen message, other than a bounce message, if
13733 this much time has passed since it was frozen. This may result in the message
13734 being re-frozen if nothing has changed since the last attempt. It is a way of
13735 saying &"keep on trying, even though there are big problems"&.
13737 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
13738 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
13739 thought to be very useful any more, and its use should probably be avoided.
13742 .option av_scanner main string "see below"
13743 This option is available if Exim is built with the content-scanning extension.
13744 It specifies which anti-virus scanner to use. The default value is:
13746 sophie:/var/run/sophie
13748 If the value of &%av_scanner%& starts with a dollar character, it is expanded
13749 before use. See section &<<SECTscanvirus>>& for further details.
13752 .option bi_command main string unset
13754 This option supplies the name of a command that is run when Exim is called with
13755 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
13756 just the command name, it is not a complete command line. If an argument is
13757 required, it must come from the &%-oA%& command line option.
13760 .option bounce_message_file main string unset
13761 .cindex "bounce message" "customizing"
13762 .cindex "customizing" "bounce message"
13763 This option defines a template file containing paragraphs of text to be used
13764 for constructing bounce messages. Details of the file's contents are given in
13765 chapter &<<CHAPemsgcust>>&. See also &%warn_message_file%&.
13768 .option bounce_message_text main string unset
13769 When this option is set, its contents are included in the default bounce
13770 message immediately after &"This message was created automatically by mail
13771 delivery software."& It is not used if &%bounce_message_file%& is set.
13773 .option bounce_return_body main boolean true
13774 .cindex "bounce message" "including body"
13775 This option controls whether the body of an incoming message is included in a
13776 bounce message when &%bounce_return_message%& is true. The default setting
13777 causes the entire message, both header and body, to be returned (subject to the
13778 value of &%bounce_return_size_limit%&). If this option is false, only the
13779 message header is included. In the case of a non-SMTP message containing an
13780 error that is detected during reception, only those header lines preceding the
13781 point at which the error was detected are returned.
13782 .cindex "bounce message" "including original"
13784 .option bounce_return_message main boolean true
13785 If this option is set false, none of the original message is included in
13786 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
13787 &%bounce_return_body%&.
13790 .option bounce_return_size_limit main integer 100K
13791 .cindex "size" "of bounce, limit"
13792 .cindex "bounce message" "size limit"
13793 .cindex "limit" "bounce message size"
13794 This option sets a limit in bytes on the size of messages that are returned to
13795 senders as part of bounce messages when &%bounce_return_message%& is true. The
13796 limit should be less than the value of the global &%message_size_limit%& and of
13797 any &%message_size_limit%& settings on transports, to allow for the bounce text
13798 that Exim generates. If this option is set to zero there is no limit.
13800 When the body of any message that is to be included in a bounce message is
13801 greater than the limit, it is truncated, and a comment pointing this out is
13802 added at the top. The actual cutoff may be greater than the value given, owing
13803 to the use of buffering for transferring the message in chunks (typically 8K in
13804 size). The idea is to save bandwidth on those undeliverable 15-megabyte
13807 .option bounce_sender_authentication main string unset
13808 .cindex "bounce message" "sender authentication"
13809 .cindex "authentication" "bounce message"
13810 .cindex "AUTH" "on bounce message"
13811 This option provides an authenticated sender address that is sent with any
13812 bounce messages generated by Exim that are sent over an authenticated SMTP
13813 connection. A typical setting might be:
13815 bounce_sender_authentication = mailer-daemon@my.domain.example
13817 which would cause bounce messages to be sent using the SMTP command:
13819 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
13821 The value of &%bounce_sender_authentication%& must always be a complete email
13824 .option callout_domain_negative_expire main time 3h
13825 .cindex "caching" "callout timeouts"
13826 .cindex "callout" "caching timeouts"
13827 This option specifies the expiry time for negative callout cache data for a
13828 domain. See section &<<SECTcallver>>& for details of callout verification, and
13829 section &<<SECTcallvercache>>& for details of the caching.
13832 .option callout_domain_positive_expire main time 7d
13833 This option specifies the expiry time for positive callout cache data for a
13834 domain. See section &<<SECTcallver>>& for details of callout verification, and
13835 section &<<SECTcallvercache>>& for details of the caching.
13838 .option callout_negative_expire main time 2h
13839 This option specifies the expiry time for negative callout cache data for an
13840 address. See section &<<SECTcallver>>& for details of callout verification, and
13841 section &<<SECTcallvercache>>& for details of the caching.
13844 .option callout_positive_expire main time 24h
13845 This option specifies the expiry time for positive callout cache data for an
13846 address. See section &<<SECTcallver>>& for details of callout verification, and
13847 section &<<SECTcallvercache>>& for details of the caching.
13850 .option callout_random_local_part main string&!! "see below"
13851 This option defines the &"random"& local part that can be used as part of
13852 callout verification. The default value is
13854 $primary_hostname-$tod_epoch-testing
13856 See section &<<CALLaddparcall>>& for details of how this value is used.
13859 .option check_log_inodes main integer 0
13860 See &%check_spool_space%& below.
13863 .option check_log_space main integer 0
13864 See &%check_spool_space%& below.
13866 .oindex "&%check_rfc2047_length%&"
13867 .cindex "RFC 2047" "disabling length check"
13868 .option check_rfc2047_length main boolean true
13869 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
13870 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
13871 word; strings to be encoded that exceed this length are supposed to use
13872 multiple encoded words. By default, Exim does not recognize encoded words that
13873 exceed the maximum length. However, it seems that some software, in violation
13874 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
13875 set false, Exim recognizes encoded words of any length.
13878 .option check_spool_inodes main integer 0
13879 See &%check_spool_space%& below.
13882 .option check_spool_space main integer 0
13883 .cindex "checking disk space"
13884 .cindex "disk space, checking"
13885 .cindex "spool directory" "checking space"
13886 The four &%check_...%& options allow for checking of disk resources before a
13887 message is accepted.
13889 .vindex "&$log_inodes$&"
13890 .vindex "&$log_space$&"
13891 .vindex "&$spool_inodes$&"
13892 .vindex "&$spool_space$&"
13893 When any of these options are set, they apply to all incoming messages. If you
13894 want to apply different checks to different kinds of message, you can do so by
13895 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
13896 &$spool_space$& in an ACL with appropriate additional conditions.
13899 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
13900 either value is greater than zero, for example:
13902 check_spool_space = 10M
13903 check_spool_inodes = 100
13905 The spool partition is the one that contains the directory defined by
13906 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
13909 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
13910 files are written if either is greater than zero. These should be set only if
13911 &%log_file_path%& and &%spool_directory%& refer to different partitions.
13913 If there is less space or fewer inodes than requested, Exim refuses to accept
13914 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
13915 error response to the MAIL command. If ESMTP is in use and there was a
13916 SIZE parameter on the MAIL command, its value is added to the
13917 &%check_spool_space%& value, and the check is performed even if
13918 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
13920 The values for &%check_spool_space%& and &%check_log_space%& are held as a
13921 number of kilobytes. If a non-multiple of 1024 is specified, it is rounded up.
13923 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
13924 failure a message is written to stderr and Exim exits with a non-zero code, as
13925 it obviously cannot send an error message of any kind.
13927 .option daemon_smtp_ports main string &`smtp`&
13928 .cindex "port" "for daemon"
13929 .cindex "TCP/IP" "setting listening ports"
13930 This option specifies one or more default SMTP ports on which the Exim daemon
13931 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
13932 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
13934 .option daemon_startup_retries main integer 9
13935 .cindex "daemon startup, retrying"
13936 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
13937 the daemon at startup when it cannot immediately bind a listening socket
13938 (typically because the socket is already in use): &%daemon_startup_retries%&
13939 defines the number of retries after the first failure, and
13940 &%daemon_startup_sleep%& defines the length of time to wait between retries.
13942 .option daemon_startup_sleep main time 30s
13943 See &%daemon_startup_retries%&.
13945 .option delay_warning main "time list" 24h
13946 .cindex "warning of delay"
13947 .cindex "delay warning, specifying"
13948 When a message is delayed, Exim sends a warning message to the sender at
13949 intervals specified by this option. The data is a colon-separated list of times
13950 after which to send warning messages. If the value of the option is an empty
13951 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
13952 message has been on the queue for longer than the last time, the last interval
13953 between the times is used to compute subsequent warning times. For example,
13956 delay_warning = 4h:8h:24h
13958 the first message is sent after 4 hours, the second after 8 hours, and
13959 the third one after 24 hours. After that, messages are sent every 16 hours,
13960 because that is the interval between the last two times on the list. If you set
13961 just one time, it specifies the repeat interval. For example, with:
13965 messages are repeated every six hours. To stop warnings after a given time, set
13966 a very large time at the end of the list. For example:
13968 delay_warning = 2h:12h:99d
13970 Note that the option is only evaluated at the time a delivery attempt fails,
13971 which depends on retry and queue-runner configuration.
13972 Typically retries will be configured more frequently than warning messages.
13974 .option delay_warning_condition main string&!! "see below"
13975 .vindex "&$domain$&"
13976 The string is expanded at the time a warning message might be sent. If all the
13977 deferred addresses have the same domain, it is set in &$domain$& during the
13978 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
13979 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
13980 &"false"& (the comparison being done caselessly) then the warning message is
13981 not sent. The default is:
13983 delay_warning_condition = ${if or {\
13984 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
13985 { match{$h_precedence:}{(?i)bulk|list|junk} }\
13986 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
13989 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
13990 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
13991 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
13992 &"auto-replied"& in an &'Auto-Submitted:'& header.
13994 .option deliver_drop_privilege main boolean false
13995 .cindex "unprivileged delivery"
13996 .cindex "delivery" "unprivileged"
13997 If this option is set true, Exim drops its root privilege at the start of a
13998 delivery process, and runs as the Exim user throughout. This severely restricts
13999 the kinds of local delivery that are possible, but is viable in certain types
14000 of configuration. There is a discussion about the use of root privilege in
14001 chapter &<<CHAPsecurity>>&.
14003 .option deliver_queue_load_max main fixed-point unset
14004 .cindex "load average"
14005 .cindex "queue runner" "abandoning"
14006 When this option is set, a queue run is abandoned if the system load average
14007 becomes greater than the value of the option. The option has no effect on
14008 ancient operating systems on which Exim cannot determine the load average.
14009 See also &%queue_only_load%& and &%smtp_load_reserve%&.
14012 .option delivery_date_remove main boolean true
14013 .cindex "&'Delivery-date:'& header line"
14014 Exim's transports have an option for adding a &'Delivery-date:'& header to a
14015 message when it is delivered, in exactly the same way as &'Return-path:'& is
14016 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
14017 should not be present in incoming messages, and this option causes them to be
14018 removed at the time the message is received, to avoid any problems that might
14019 occur when a delivered message is subsequently sent on to some other recipient.
14021 .option disable_fsync main boolean false
14022 .cindex "&[fsync()]&, disabling"
14023 This option is available only if Exim was built with the compile-time option
14024 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
14025 a runtime configuration generates an &"unknown option"& error. You should not
14026 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
14027 really, really, really understand what you are doing. &'No pre-compiled
14028 distributions of Exim should ever make this option available.'&
14030 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
14031 updated files' data to be written to disc before continuing. Unexpected events
14032 such as crashes and power outages may cause data to be lost or scrambled.
14033 Here be Dragons. &*Beware.*&
14036 .option disable_ipv6 main boolean false
14037 .cindex "IPv6" "disabling"
14038 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
14039 activities take place. AAAA records are never looked up, and any IPv6 addresses
14040 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
14041 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14042 to handle IPv6 literal addresses.
14045 .option dns_again_means_nonexist main "domain list&!!" unset
14046 .cindex "DNS" "&""try again""& response; overriding"
14047 DNS lookups give a &"try again"& response for the DNS errors
14048 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
14049 keep trying to deliver a message, or to give repeated temporary errors to
14050 incoming mail. Sometimes the effect is caused by a badly set up name server and
14051 may persist for a long time. If a domain which exhibits this problem matches
14052 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
14053 This option should be used with care. You can make it apply to reverse lookups
14054 by a setting such as this:
14056 dns_again_means_nonexist = *.in-addr.arpa
14058 This option applies to all DNS lookups that Exim does. It also applies when the
14059 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
14060 since these are most likely to be caused by DNS lookup problems. The
14061 &(dnslookup)& router has some options of its own for controlling what happens
14062 when lookups for MX or SRV records give temporary errors. These more specific
14063 options are applied after this global option.
14065 .option dns_check_names_pattern main string "see below"
14066 .cindex "DNS" "pre-check of name syntax"
14067 When this option is set to a non-empty string, it causes Exim to check domain
14068 names for characters that are not allowed in host names before handing them to
14069 the DNS resolver, because some resolvers give temporary errors for names that
14070 contain unusual characters. If a domain name contains any unwanted characters,
14071 a &"not found"& result is forced, and the resolver is not called. The check is
14072 done by matching the domain name against a regular expression, which is the
14073 value of this option. The default pattern is
14075 dns_check_names_pattern = \
14076 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
14078 which permits only letters, digits, slashes, and hyphens in components, but
14079 they must start and end with a letter or digit. Slashes are not, in fact,
14080 permitted in host names, but they are found in certain NS records (which can be
14081 accessed in Exim by using a &%dnsdb%& lookup). If you set
14082 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
14085 .option dns_csa_search_limit main integer 5
14086 This option controls the depth of parental searching for CSA SRV records in the
14087 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
14089 .option dns_csa_use_reverse main boolean true
14090 This option controls whether or not an IP address, given as a CSA domain, is
14091 reversed and looked up in the reverse DNS, as described in more detail in
14092 section &<<SECTverifyCSA>>&.
14095 .option dns_dnssec_ok main integer -1
14096 .cindex "DNS" "resolver options"
14097 .cindex "DNS" "DNSSEC"
14098 If this option is set to a non-negative number then Exim will initialise the
14099 DNS resolver library to either use or not use DNSSEC, overriding the system
14100 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
14102 If the resolver library does not support DNSSEC then this option has no effect.
14105 .option dns_ipv4_lookup main "domain list&!!" unset
14106 .cindex "IPv6" "DNS lookup for AAAA records"
14107 .cindex "DNS" "IPv6 lookup for AAAA records"
14108 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
14109 looks for IPv6 address records (AAAA records) as well as IPv4 address records
14110 (A records) when trying to find IP addresses for hosts, unless the host's
14111 domain matches this list.
14113 This is a fudge to help with name servers that give big delays or otherwise do
14114 not work for the AAAA record type. In due course, when the world's name
14115 servers have all been upgraded, there should be no need for this option.
14118 .option dns_retrans main time 0s
14119 .cindex "DNS" "resolver options"
14120 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
14121 retransmission and retry parameters for DNS lookups. Values of zero (the
14122 defaults) leave the system default settings unchanged. The first value is the
14123 time between retries, and the second is the number of retries. It isn't
14124 totally clear exactly how these settings affect the total time a DNS lookup may
14125 take. I haven't found any documentation about timeouts on DNS lookups; these
14126 parameter values are available in the external resolver interface structure,
14127 but nowhere does it seem to describe how they are used or what you might want
14131 .option dns_retry main integer 0
14132 See &%dns_retrans%& above.
14135 .option dns_use_edns0 main integer -1
14136 .cindex "DNS" "resolver options"
14137 .cindex "DNS" "EDNS0"
14138 If this option is set to a non-negative number then Exim will initialise the
14139 DNS resolver library to either use or not use EDNS0 extensions, overriding
14140 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
14143 If the resolver library does not support EDNS0 then this option has no effect.
14146 .option drop_cr main boolean false
14147 This is an obsolete option that is now a no-op. It used to affect the way Exim
14148 handled CR and LF characters in incoming messages. What happens now is
14149 described in section &<<SECTlineendings>>&.
14151 .option dsn_from main "string&!!" "see below"
14152 .cindex "&'From:'& header line" "in bounces"
14153 .cindex "bounce messages" "&'From:'& line, specifying"
14154 This option can be used to vary the contents of &'From:'& header lines in
14155 bounces and other automatically generated messages (&"Delivery Status
14156 Notifications"& &-- hence the name of the option). The default setting is:
14158 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
14160 The value is expanded every time it is needed. If the expansion fails, a
14161 panic is logged, and the default value is used.
14163 .option envelope_to_remove main boolean true
14164 .cindex "&'Envelope-to:'& header line"
14165 Exim's transports have an option for adding an &'Envelope-to:'& header to a
14166 message when it is delivered, in exactly the same way as &'Return-path:'& is
14167 handled. &'Envelope-to:'& records the original recipient address from the
14168 messages's envelope that caused the delivery to happen. Such headers should not
14169 be present in incoming messages, and this option causes them to be removed at
14170 the time the message is received, to avoid any problems that might occur when a
14171 delivered message is subsequently sent on to some other recipient.
14174 .option errors_copy main "string list&!!" unset
14175 .cindex "bounce message" "copy to other address"
14176 .cindex "copy of bounce message"
14177 Setting this option causes Exim to send bcc copies of bounce messages that it
14178 generates to other addresses. &*Note*&: This does not apply to bounce messages
14179 coming from elsewhere. The value of the option is a colon-separated list of
14180 items. Each item consists of a pattern, terminated by white space, followed by
14181 a comma-separated list of email addresses. If a pattern contains spaces, it
14182 must be enclosed in double quotes.
14184 Each pattern is processed in the same way as a single item in an address list
14185 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
14186 the bounce message, the message is copied to the addresses on the list. The
14187 items are scanned in order, and once a matching one is found, no further items
14188 are examined. For example:
14190 errors_copy = spqr@mydomain postmaster@mydomain.example :\
14191 rqps@mydomain hostmaster@mydomain.example,\
14192 postmaster@mydomain.example
14194 .vindex "&$domain$&"
14195 .vindex "&$local_part$&"
14196 The address list is expanded before use. The expansion variables &$local_part$&
14197 and &$domain$& are set from the original recipient of the error message, and if
14198 there was any wildcard matching in the pattern, the expansion
14199 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
14200 variables &$0$&, &$1$&, etc. are set in the normal way.
14203 .option errors_reply_to main string unset
14204 .cindex "bounce message" "&'Reply-to:'& in"
14205 By default, Exim's bounce and delivery warning messages contain the header line
14207 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
14209 .oindex &%quota_warn_message%&
14210 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
14211 A warning message that is generated by the &%quota_warn_message%& option in an
14212 &(appendfile)& transport may contain its own &'From:'& header line that
14213 overrides the default.
14215 Experience shows that people reply to bounce messages. If the
14216 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
14217 and warning messages. For example:
14219 errors_reply_to = postmaster@my.domain.example
14221 The value of the option is not expanded. It must specify a valid RFC 2822
14222 address. However, if a warning message that is generated by the
14223 &%quota_warn_message%& option in an &(appendfile)& transport contain its
14224 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
14228 .option exim_group main string "compile-time configured"
14229 .cindex "gid (group id)" "Exim's own"
14230 .cindex "Exim group"
14231 This option changes the gid under which Exim runs when it gives up root
14232 privilege. The default value is compiled into the binary. The value of this
14233 option is used only when &%exim_user%& is also set. Unless it consists entirely
14234 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
14235 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
14239 .option exim_path main string "see below"
14240 .cindex "Exim binary, path name"
14241 This option specifies the path name of the Exim binary, which is used when Exim
14242 needs to re-exec itself. The default is set up to point to the file &'exim'& in
14243 the directory configured at compile time by the BIN_DIRECTORY setting. It
14244 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
14246 &*Warning*&: Do not use a macro to define the value of this option, because
14247 you will break those Exim utilities that scan the configuration file to find
14248 where the binary is. (They then use the &%-bP%& option to extract option
14249 settings such as the value of &%spool_directory%&.)
14252 .option exim_user main string "compile-time configured"
14253 .cindex "uid (user id)" "Exim's own"
14254 .cindex "Exim user"
14255 This option changes the uid under which Exim runs when it gives up root
14256 privilege. The default value is compiled into the binary. Ownership of the run
14257 time configuration file and the use of the &%-C%& and &%-D%& command line
14258 options is checked against the values in the binary, not what is set here.
14260 Unless it consists entirely of digits, the string is looked up using
14261 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
14262 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
14263 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
14266 .option extra_local_interfaces main "string list" unset
14267 This option defines network interfaces that are to be considered local when
14268 routing, but which are not used for listening by the daemon. See section
14269 &<<SECTreclocipadd>>& for details.
14272 . Allow this long option name to split; give it unsplit as a fifth argument
14273 . for the automatic .oindex that is generated by .option.
14275 .option "extract_addresses_remove_ &~&~arguments" main boolean true &&&
14276 extract_addresses_remove_arguments
14278 .cindex "command line" "addresses with &%-t%&"
14279 .cindex "Sendmail compatibility" "&%-t%& option"
14280 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
14281 are present on the command line when the &%-t%& option is used to build an
14282 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
14283 line addresses are removed from the recipients list. This is also how Smail
14284 behaves. However, other Sendmail documentation (the O'Reilly book) states that
14285 command line addresses are added to those obtained from the header lines. When
14286 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
14287 argument headers. If it is set false, Exim adds rather than removes argument
14291 .option finduser_retries main integer 0
14292 .cindex "NIS, retrying user lookups"
14293 On systems running NIS or other schemes in which user and group information is
14294 distributed from a remote system, there can be times when &[getpwnam()]& and
14295 related functions fail, even when given valid data, because things time out.
14296 Unfortunately these failures cannot be distinguished from genuine &"not found"&
14297 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
14298 many extra times to find a user or a group, waiting for one second between
14301 .cindex "&_/etc/passwd_&" "multiple reading of"
14302 You should not set this option greater than zero if your user information is in
14303 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
14304 search the file multiple times for non-existent users, and also cause delay.
14308 .option freeze_tell main "string list, comma separated" unset
14309 .cindex "freezing messages" "sending a message when freezing"
14310 On encountering certain errors, or when configured to do so in a system filter,
14311 ACL, or special router, Exim freezes a message. This means that no further
14312 delivery attempts take place until an administrator thaws the message, or the
14313 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
14314 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
14315 warning message whenever it freezes something, unless the message it is
14316 freezing is a locally-generated bounce message. (Without this exception there
14317 is the possibility of looping.) The warning message is sent to the addresses
14318 supplied as the comma-separated value of this option. If several of the
14319 message's addresses cause freezing, only a single message is sent. If the
14320 freezing was automatic, the reason(s) for freezing can be found in the message
14321 log. If you configure freezing in a filter or ACL, you must arrange for any
14322 logging that you require.
14325 .option gecos_name main string&!! unset
14327 .cindex "&""gecos""& field, parsing"
14328 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
14329 password file to hold other information in addition to users' real names. Exim
14330 looks up this field for use when it is creating &'Sender:'& or &'From:'&
14331 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
14332 of the field are used unchanged, except that, if an ampersand is encountered,
14333 it is replaced by the user's login name with the first character forced to
14334 upper case, since this is a convention that is observed on many systems.
14336 When these options are set, &%gecos_pattern%& is treated as a regular
14337 expression that is to be applied to the field (again with && replaced by the
14338 login name), and if it matches, &%gecos_name%& is expanded and used as the
14341 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
14342 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
14343 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
14344 name terminates at the first comma, the following can be used:
14346 gecos_pattern = ([^,]*)
14350 .option gecos_pattern main string unset
14351 See &%gecos_name%& above.
14354 .option gnutls_compat_mode main boolean unset
14355 This option controls whether GnuTLS is used in compatibility mode in an Exim
14356 server. This reduces security slightly, but improves interworking with older
14357 implementations of TLS.
14360 option gnutls_allow_auto_pkcs11 main boolean unset
14361 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
14362 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
14365 &url(http://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
14370 .option headers_charset main string "see below"
14371 This option sets a default character set for translating from encoded MIME
14372 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
14373 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
14374 ultimate default is ISO-8859-1. For more details see the description of header
14375 insertions in section &<<SECTexpansionitems>>&.
14379 .option header_maxsize main integer "see below"
14380 .cindex "header section" "maximum size of"
14381 .cindex "limit" "size of message header section"
14382 This option controls the overall maximum size of a message's header
14383 section. The default is the value of HEADER_MAXSIZE in
14384 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
14385 sections are rejected.
14388 .option header_line_maxsize main integer 0
14389 .cindex "header lines" "maximum size of"
14390 .cindex "limit" "size of one header line"
14391 This option limits the length of any individual header line in a message, after
14392 all the continuations have been joined together. Messages with individual
14393 header lines that are longer than the limit are rejected. The default value of
14394 zero means &"no limit"&.
14399 .option helo_accept_junk_hosts main "host list&!!" unset
14400 .cindex "HELO" "accepting junk data"
14401 .cindex "EHLO" "accepting junk data"
14402 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
14403 mail, and gives an error response for invalid data. Unfortunately, there are
14404 some SMTP clients that send syntactic junk. They can be accommodated by setting
14405 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
14406 if you want to do semantic checking.
14407 See also &%helo_allow_chars%& for a way of extending the permitted character
14411 .option helo_allow_chars main string unset
14412 .cindex "HELO" "underscores in"
14413 .cindex "EHLO" "underscores in"
14414 .cindex "underscore in EHLO/HELO"
14415 This option can be set to a string of rogue characters that are permitted in
14416 all EHLO and HELO names in addition to the standard letters, digits,
14417 hyphens, and dots. If you really must allow underscores, you can set
14419 helo_allow_chars = _
14421 Note that the value is one string, not a list.
14424 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
14425 .cindex "HELO" "forcing reverse lookup"
14426 .cindex "EHLO" "forcing reverse lookup"
14427 If the domain given by a client in a HELO or EHLO command matches this
14428 list, a reverse lookup is done in order to establish the host's true name. The
14429 default forces a lookup if the client host gives the server's name or any of
14430 its IP addresses (in brackets), something that broken clients have been seen to
14434 .option helo_try_verify_hosts main "host list&!!" unset
14435 .cindex "HELO verifying" "optional"
14436 .cindex "EHLO" "verifying, optional"
14437 By default, Exim just checks the syntax of HELO and EHLO commands (see
14438 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
14439 to do more extensive checking of the data supplied by these commands. The ACL
14440 condition &`verify = helo`& is provided to make this possible.
14441 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
14442 to force the check to occur. From release 4.53 onwards, this is no longer
14443 necessary. If the check has not been done before &`verify = helo`& is
14444 encountered, it is done at that time. Consequently, this option is obsolete.
14445 Its specification is retained here for backwards compatibility.
14447 When an EHLO or HELO command is received, if the calling host matches
14448 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
14449 EHLO command either:
14452 is an IP literal matching the calling address of the host, or
14454 .cindex "DNS" "reverse lookup"
14455 .cindex "reverse DNS lookup"
14456 matches the host name that Exim obtains by doing a reverse lookup of the
14457 calling host address, or
14459 when looked up using &[gethostbyname()]& (or &[getipnodebyname()]& when
14460 available) yields the calling host address.
14463 However, the EHLO or HELO command is not rejected if any of the checks
14464 fail. Processing continues, but the result of the check is remembered, and can
14465 be detected later in an ACL by the &`verify = helo`& condition.
14467 .option helo_verify_hosts main "host list&!!" unset
14468 .cindex "HELO verifying" "mandatory"
14469 .cindex "EHLO" "verifying, mandatory"
14470 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
14471 backwards compatibility. For hosts that match this option, Exim checks the host
14472 name given in the HELO or EHLO in the same way as for
14473 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
14474 rejected with a 550 error, and entries are written to the main and reject logs.
14475 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
14478 .option hold_domains main "domain list&!!" unset
14479 .cindex "domain" "delaying delivery"
14480 .cindex "delivery" "delaying certain domains"
14481 This option allows mail for particular domains to be held on the queue
14482 manually. The option is overridden if a message delivery is forced with the
14483 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
14484 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
14485 item in &%hold_domains%&, no routing or delivery for that address is done, and
14486 it is deferred every time the message is looked at.
14488 This option is intended as a temporary operational measure for delaying the
14489 delivery of mail while some problem is being sorted out, or some new
14490 configuration tested. If you just want to delay the processing of some
14491 domains until a queue run occurs, you should use &%queue_domains%& or
14492 &%queue_smtp_domains%&, not &%hold_domains%&.
14494 A setting of &%hold_domains%& does not override Exim's code for removing
14495 messages from the queue if they have been there longer than the longest retry
14496 time in any retry rule. If you want to hold messages for longer than the normal
14497 retry times, insert a dummy retry rule with a long retry time.
14500 .option host_lookup main "host list&!!" unset
14501 .cindex "host name" "lookup, forcing"
14502 Exim does not look up the name of a calling host from its IP address unless it
14503 is required to compare against some host list, or the host matches
14504 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
14505 option (which normally contains IP addresses rather than host names). The
14506 default configuration file contains
14510 which causes a lookup to happen for all hosts. If the expense of these lookups
14511 is felt to be too great, the setting can be changed or removed.
14513 After a successful reverse lookup, Exim does a forward lookup on the name it
14514 has obtained, to verify that it yields the IP address that it started with. If
14515 this check fails, Exim behaves as if the name lookup failed.
14517 .vindex "&$host_lookup_failed$&"
14518 .vindex "&$sender_host_name$&"
14519 After any kind of failure, the host name (in &$sender_host_name$&) remains
14520 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
14521 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
14522 &`verify = reverse_host_lookup`& in ACLs.
14525 .option host_lookup_order main "string list" &`bydns:byaddr`&
14526 This option specifies the order of different lookup methods when Exim is trying
14527 to find a host name from an IP address. The default is to do a DNS lookup
14528 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
14529 if that fails. You can change the order of these lookups, or omit one entirely,
14532 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
14533 multiple PTR records in the DNS and the IP address is not listed in
14534 &_/etc/hosts_&. Different operating systems give different results in this
14535 case. That is why the default tries a DNS lookup first.
14539 .option host_reject_connection main "host list&!!" unset
14540 .cindex "host" "rejecting connections from"
14541 If this option is set, incoming SMTP calls from the hosts listed are rejected
14542 as soon as the connection is made.
14543 This option is obsolete, and retained only for backward compatibility, because
14544 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
14545 connections immediately.
14547 The ability to give an immediate rejection (either by this option or using an
14548 ACL) is provided for use in unusual cases. Many hosts will just try again,
14549 sometimes without much delay. Normally, it is better to use an ACL to reject
14550 incoming messages at a later stage, such as after RCPT commands. See
14551 chapter &<<CHAPACL>>&.
14554 .option hosts_connection_nolog main "host list&!!" unset
14555 .cindex "host" "not logging connections from"
14556 This option defines a list of hosts for which connection logging does not
14557 happen, even though the &%smtp_connection%& log selector is set. For example,
14558 you might want not to log SMTP connections from local processes, or from
14559 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
14560 the daemon; you should therefore strive to restrict its value to a short inline
14561 list of IP addresses and networks. To disable logging SMTP connections from
14562 local processes, you must create a host list with an empty item. For example:
14564 hosts_connection_nolog = :
14566 If the &%smtp_connection%& log selector is not set, this option has no effect.
14570 .option hosts_treat_as_local main "domain list&!!" unset
14571 .cindex "local host" "domains treated as"
14572 .cindex "host" "treated as local"
14573 If this option is set, any host names that match the domain list are treated as
14574 if they were the local host when Exim is scanning host lists obtained from MX
14576 or other sources. Note that the value of this option is a domain list, not a
14577 host list, because it is always used to check host names, not IP addresses.
14579 This option also applies when Exim is matching the special items
14580 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
14581 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
14582 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
14583 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
14584 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
14585 interfaces and recognizing the local host.
14588 .option ibase_servers main "string list" unset
14589 .cindex "InterBase" "server list"
14590 This option provides a list of InterBase servers and associated connection data,
14591 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
14592 The option is available only if Exim has been built with InterBase support.
14596 .option ignore_bounce_errors_after main time 10w
14597 .cindex "bounce message" "discarding"
14598 .cindex "discarding bounce message"
14599 This option affects the processing of bounce messages that cannot be delivered,
14600 that is, those that suffer a permanent delivery failure. (Bounce messages that
14601 suffer temporary delivery failures are of course retried in the usual way.)
14603 After a permanent delivery failure, bounce messages are frozen,
14604 because there is no sender to whom they can be returned. When a frozen bounce
14605 message has been on the queue for more than the given time, it is unfrozen at
14606 the next queue run, and a further delivery is attempted. If delivery fails
14607 again, the bounce message is discarded. This makes it possible to keep failed
14608 bounce messages around for a shorter time than the normal maximum retry time
14609 for frozen messages. For example,
14611 ignore_bounce_errors_after = 12h
14613 retries failed bounce message deliveries after 12 hours, discarding any further
14614 failures. If the value of this option is set to a zero time period, bounce
14615 failures are discarded immediately. Setting a very long time (as in the default
14616 value) has the effect of disabling this option. For ways of automatically
14617 dealing with other kinds of frozen message, see &%auto_thaw%& and
14618 &%timeout_frozen_after%&.
14621 .option ignore_fromline_hosts main "host list&!!" unset
14622 .cindex "&""From""& line"
14623 .cindex "UUCP" "&""From""& line"
14624 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
14625 the headers of a message. By default this is treated as the start of the
14626 message's body, which means that any following headers are not recognized as
14627 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
14628 match those hosts that insist on sending it. If the sender is actually a local
14629 process rather than a remote host, and is using &%-bs%& to inject the messages,
14630 &%ignore_fromline_local%& must be set to achieve this effect.
14633 .option ignore_fromline_local main boolean false
14634 See &%ignore_fromline_hosts%& above.
14637 .option keep_malformed main time 4d
14638 This option specifies the length of time to keep messages whose spool files
14639 have been corrupted in some way. This should, of course, never happen. At the
14640 next attempt to deliver such a message, it gets removed. The incident is
14644 .option ldap_ca_cert_dir main string unset
14645 .cindex "LDAP", "TLS CA certificate directory"
14646 This option indicates which directory contains CA certificates for verifying
14647 a TLS certificate presented by an LDAP server.
14648 While Exim does not provide a default value, your SSL library may.
14649 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
14650 and constrained to be a directory.
14653 .option ldap_ca_cert_file main string unset
14654 .cindex "LDAP", "TLS CA certificate file"
14655 This option indicates which file contains CA certificates for verifying
14656 a TLS certificate presented by an LDAP server.
14657 While Exim does not provide a default value, your SSL library may.
14658 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
14659 and constrained to be a file.
14662 .option ldap_cert_file main string unset
14663 .cindex "LDAP" "TLS client certificate file"
14664 This option indicates which file contains an TLS client certificate which
14665 Exim should present to the LDAP server during TLS negotiation.
14666 Should be used together with &%ldap_cert_key%&.
14669 .option ldap_cert_key main string unset
14670 .cindex "LDAP" "TLS client key file"
14671 This option indicates which file contains the secret/private key to use
14672 to prove identity to the LDAP server during TLS negotiation.
14673 Should be used together with &%ldap_cert_file%&, which contains the
14674 identity to be proven.
14677 .option ldap_cipher_suite main string unset
14678 .cindex "LDAP" "TLS cipher suite"
14679 This controls the TLS cipher-suite negotiation during TLS negotiation with
14680 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
14681 cipher-suite options with OpenSSL (as used by LDAP client libraries).
14684 .option ldap_default_servers main "string list" unset
14685 .cindex "LDAP" "default servers"
14686 This option provides a list of LDAP servers which are tried in turn when an
14687 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
14688 details of LDAP queries. This option is available only when Exim has been built
14692 .option ldap_require_cert main string unset.
14693 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
14694 This should be one of the values "hard", "demand", "allow", "try" or "never".
14695 A value other than one of these is interpreted as "never".
14696 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
14697 Although Exim does not set a default, the LDAP library probably defaults
14701 .option ldap_start_tls main boolean false
14702 .cindex "LDAP" "whether or not to negotiate TLS"
14703 If set, Exim will attempt to negotiate TLS with the LDAP server when
14704 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
14705 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
14707 In the event of failure to negotiate TLS, the action taken is controlled
14708 by &%ldap_require_cert%&.
14711 .option ldap_version main integer unset
14712 .cindex "LDAP" "protocol version, forcing"
14713 This option can be used to force Exim to set a specific protocol version for
14714 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
14715 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
14716 the LDAP headers; otherwise it is 2. This option is available only when Exim
14717 has been built with LDAP support.
14721 .option local_from_check main boolean true
14722 .cindex "&'Sender:'& header line" "disabling addition of"
14723 .cindex "&'From:'& header line" "disabling checking of"
14724 When a message is submitted locally (that is, not over a TCP/IP connection) by
14725 an untrusted user, Exim removes any existing &'Sender:'& header line, and
14726 checks that the &'From:'& header line matches the login of the calling user and
14727 the domain specified by &%qualify_domain%&.
14729 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
14730 locally submitted message is automatically qualified by Exim, unless the
14731 &%-bnq%& command line option is used.
14733 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
14734 on the local part. If the &'From:'& header line does not match, Exim adds a
14735 &'Sender:'& header with an address constructed from the calling user's login
14736 and the default qualify domain.
14738 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
14739 and no &'Sender:'& header is ever added. If, in addition, you want to retain
14740 &'Sender:'& header lines supplied by untrusted users, you must also set
14741 &%local_sender_retain%& to be true.
14743 .cindex "envelope sender"
14744 These options affect only the header lines in the message. The envelope sender
14745 is still forced to be the login id at the qualify domain unless
14746 &%untrusted_set_sender%& permits the user to supply an envelope sender.
14748 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
14749 request similar header line checking. See section &<<SECTthesenhea>>&, which
14750 has more details about &'Sender:'& processing.
14755 .option local_from_prefix main string unset
14756 When Exim checks the &'From:'& header line of locally submitted messages for
14757 matching the login id (see &%local_from_check%& above), it can be configured to
14758 ignore certain prefixes and suffixes in the local part of the address. This is
14759 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
14760 appropriate lists, in the same form as the &%local_part_prefix%& and
14761 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
14764 local_from_prefix = *-
14766 is set, a &'From:'& line containing
14768 From: anything-user@your.domain.example
14770 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
14771 matches the actual sender address that is constructed from the login name and
14775 .option local_from_suffix main string unset
14776 See &%local_from_prefix%& above.
14779 .option local_interfaces main "string list" "see below"
14780 This option controls which network interfaces are used by the daemon for
14781 listening; they are also used to identify the local host when routing. Chapter
14782 &<<CHAPinterfaces>>& contains a full description of this option and the related
14783 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
14784 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
14785 &%local_interfaces%& is
14787 local_interfaces = 0.0.0.0
14789 when Exim is built without IPv6 support; otherwise it is
14791 local_interfaces = <; ::0 ; 0.0.0.0
14794 .option local_scan_timeout main time 5m
14795 .cindex "timeout" "for &[local_scan()]& function"
14796 .cindex "&[local_scan()]& function" "timeout"
14797 This timeout applies to the &[local_scan()]& function (see chapter
14798 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
14799 the incoming message is rejected with a temporary error if it is an SMTP
14800 message. For a non-SMTP message, the message is dropped and Exim ends with a
14801 non-zero code. The incident is logged on the main and reject logs.
14805 .option local_sender_retain main boolean false
14806 .cindex "&'Sender:'& header line" "retaining from local submission"
14807 When a message is submitted locally (that is, not over a TCP/IP connection) by
14808 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
14809 do not want this to happen, you must set &%local_sender_retain%&, and you must
14810 also set &%local_from_check%& to be false (Exim will complain if you do not).
14811 See also the ACL modifier &`control = suppress_local_fixups`&. Section
14812 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
14817 .option localhost_number main string&!! unset
14818 .cindex "host" "locally unique number for"
14819 .cindex "message ids" "with multiple hosts"
14820 .vindex "&$localhost_number$&"
14821 Exim's message ids are normally unique only within the local host. If
14822 uniqueness among a set of hosts is required, each host must set a different
14823 value for the &%localhost_number%& option. The string is expanded immediately
14824 after reading the configuration file (so that a number can be computed from the
14825 host name, for example) and the result of the expansion must be a number in the
14826 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
14827 systems). This is available in subsequent string expansions via the variable
14828 &$localhost_number$&. When &%localhost_number is set%&, the final two
14829 characters of the message id, instead of just being a fractional part of the
14830 time, are computed from the time and the local host number as described in
14831 section &<<SECTmessiden>>&.
14835 .option log_file_path main "string list&!!" "set at compile time"
14836 .cindex "log" "file path for"
14837 This option sets the path which is used to determine the names of Exim's log
14838 files, or indicates that logging is to be to syslog, or both. It is expanded
14839 when Exim is entered, so it can, for example, contain a reference to the host
14840 name. If no specific path is set for the log files at compile or run time, they
14841 are written in a sub-directory called &_log_& in Exim's spool directory.
14842 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
14843 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
14844 used. If this string is fixed at your installation (contains no expansion
14845 variables) it is recommended that you do not set this option in the
14846 configuration file, but instead supply the path using LOG_FILE_PATH in
14847 &_Local/Makefile_& so that it is available to Exim for logging errors detected
14848 early on &-- in particular, failure to read the configuration file.
14851 .option log_selector main string unset
14852 .cindex "log" "selectors"
14853 This option can be used to reduce or increase the number of things that Exim
14854 writes to its log files. Its argument is made up of names preceded by plus or
14855 minus characters. For example:
14857 log_selector = +arguments -retry_defer
14859 A list of possible names and what they control is given in the chapter on
14860 logging, in section &<<SECTlogselector>>&.
14863 .option log_timezone main boolean false
14864 .cindex "log" "timezone for entries"
14865 .vindex "&$tod_log$&"
14866 .vindex "&$tod_zone$&"
14867 By default, the timestamps on log lines are in local time without the
14868 timezone. This means that if your timezone changes twice a year, the timestamps
14869 in log lines are ambiguous for an hour when the clocks go back. One way of
14870 avoiding this problem is to set the timezone to UTC. An alternative is to set
14871 &%log_timezone%& true. This turns on the addition of the timezone offset to
14872 timestamps in log lines. Turning on this option can add quite a lot to the size
14873 of log files because each line is extended by 6 characters. Note that the
14874 &$tod_log$& variable contains the log timestamp without the zone, but there is
14875 another variable called &$tod_zone$& that contains just the timezone offset.
14878 .option lookup_open_max main integer 25
14879 .cindex "too many open files"
14880 .cindex "open files, too many"
14881 .cindex "file" "too many open"
14882 .cindex "lookup" "maximum open files"
14883 .cindex "limit" "open files for lookups"
14884 This option limits the number of simultaneously open files for single-key
14885 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
14886 Exim normally keeps these files open during routing, because often the same
14887 file is required several times. If the limit is reached, Exim closes the least
14888 recently used file. Note that if you are using the &'ndbm'& library, it
14889 actually opens two files for each logical DBM database, though it still counts
14890 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
14891 open files"& errors with NDBM, you need to reduce the value of
14892 &%lookup_open_max%&.
14895 .option max_username_length main integer 0
14896 .cindex "length of login name"
14897 .cindex "user name" "maximum length"
14898 .cindex "limit" "user name length"
14899 Some operating systems are broken in that they truncate long arguments to
14900 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
14901 this option is set greater than zero, any attempt to call &[getpwnam()]& with
14902 an argument that is longer behaves as if &[getpwnam()]& failed.
14905 .option message_body_newlines main bool false
14906 .cindex "message body" "newlines in variables"
14907 .cindex "newline" "in message body variables"
14908 .vindex "&$message_body$&"
14909 .vindex "&$message_body_end$&"
14910 By default, newlines in the message body are replaced by spaces when setting
14911 the &$message_body$& and &$message_body_end$& expansion variables. If this
14912 option is set true, this no longer happens.
14915 .option message_body_visible main integer 500
14916 .cindex "body of message" "visible size"
14917 .cindex "message body" "visible size"
14918 .vindex "&$message_body$&"
14919 .vindex "&$message_body_end$&"
14920 This option specifies how much of a message's body is to be included in the
14921 &$message_body$& and &$message_body_end$& expansion variables.
14924 .option message_id_header_domain main string&!! unset
14925 .cindex "&'Message-ID:'& header line"
14926 If this option is set, the string is expanded and used as the right hand side
14927 (domain) of the &'Message-ID:'& header that Exim creates if a
14928 locally-originated incoming message does not have one. &"Locally-originated"&
14929 means &"not received over TCP/IP."&
14930 Otherwise, the primary host name is used.
14931 Only letters, digits, dot and hyphen are accepted; any other characters are
14932 replaced by hyphens. If the expansion is forced to fail, or if the result is an
14933 empty string, the option is ignored.
14936 .option message_id_header_text main string&!! unset
14937 If this variable is set, the string is expanded and used to augment the text of
14938 the &'Message-id:'& header that Exim creates if a locally-originated incoming
14939 message does not have one. The text of this header is required by RFC 2822 to
14940 take the form of an address. By default, Exim uses its internal message id as
14941 the local part, and the primary host name as the domain. If this option is set,
14942 it is expanded, and provided the expansion is not forced to fail, and does not
14943 yield an empty string, the result is inserted into the header immediately
14944 before the @, separated from the internal message id by a dot. Any characters
14945 that are illegal in an address are automatically converted into hyphens. This
14946 means that variables such as &$tod_log$& can be used, because the spaces and
14947 colons will become hyphens.
14950 .option message_logs main boolean true
14951 .cindex "message logs" "disabling"
14952 .cindex "log" "message log; disabling"
14953 If this option is turned off, per-message log files are not created in the
14954 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
14955 Exim, by reducing the number of files involved in handling a message from a
14956 minimum of four (header spool file, body spool file, delivery journal, and
14957 per-message log) to three. The other major I/O activity is Exim's main log,
14958 which is not affected by this option.
14961 .option message_size_limit main string&!! 50M
14962 .cindex "message" "size limit"
14963 .cindex "limit" "message size"
14964 .cindex "size" "of message, limit"
14965 This option limits the maximum size of message that Exim will process. The
14966 value is expanded for each incoming connection so, for example, it can be made
14967 to depend on the IP address of the remote host for messages arriving via
14968 TCP/IP. After expansion, the value must be a sequence of decimal digits,
14969 optionally followed by K or M.
14971 &*Note*&: This limit cannot be made to depend on a message's sender or any
14972 other properties of an individual message, because it has to be advertised in
14973 the server's response to EHLO. String expansion failure causes a temporary
14974 error. A value of zero means no limit, but its use is not recommended. See also
14975 &%bounce_return_size_limit%&.
14977 Incoming SMTP messages are failed with a 552 error if the limit is
14978 exceeded; locally-generated messages either get a stderr message or a delivery
14979 failure message to the sender, depending on the &%-oe%& setting. Rejection of
14980 an oversized message is logged in both the main and the reject logs. See also
14981 the generic transport option &%message_size_limit%&, which limits the size of
14982 message that an individual transport can process.
14984 If you use a virus-scanner and set this option to to a value larger than the
14985 maximum size that your virus-scanner is configured to support, you may get
14986 failures triggered by large mails. The right size to configure for the
14987 virus-scanner depends upon what data is passed and the options in use but it's
14988 probably safest to just set it to a little larger than this value. Eg, with a
14989 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
14990 some problems may result.
14992 A value of 0 will disable size limit checking; Exim will still advertise the
14993 SIZE extension in an EHLO response, but without a limit, so as to permit
14994 SMTP clients to still indicate the message size along with the MAIL verb.
14997 .option move_frozen_messages main boolean false
14998 .cindex "frozen messages" "moving"
14999 This option, which is available only if Exim has been built with the setting
15001 SUPPORT_MOVE_FROZEN_MESSAGES=yes
15003 in &_Local/Makefile_&, causes frozen messages and their message logs to be
15004 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
15005 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
15006 standard utilities for handling such moved messages, and they do not show up in
15007 lists generated by &%-bp%& or by the Exim monitor.
15010 .option mua_wrapper main boolean false
15011 Setting this option true causes Exim to run in a very restrictive mode in which
15012 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
15013 contains a full description of this facility.
15017 .option mysql_servers main "string list" unset
15018 .cindex "MySQL" "server list"
15019 This option provides a list of MySQL servers and associated connection data, to
15020 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
15021 option is available only if Exim has been built with MySQL support.
15024 .option never_users main "string list&!!" unset
15025 This option is expanded just once, at the start of Exim's processing. Local
15026 message deliveries are normally run in processes that are setuid to the
15027 recipient, and remote deliveries are normally run under Exim's own uid and gid.
15028 It is usually desirable to prevent any deliveries from running as root, as a
15031 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
15032 list of users that must not be used for local deliveries. This list is fixed in
15033 the binary and cannot be overridden by the configuration file. By default, it
15034 contains just the single user name &"root"&. The &%never_users%& runtime option
15035 can be used to add more users to the fixed list.
15037 If a message is to be delivered as one of the users on the fixed list or the
15038 &%never_users%& list, an error occurs, and delivery is deferred. A common
15041 never_users = root:daemon:bin
15043 Including root is redundant if it is also on the fixed list, but it does no
15044 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
15048 .option openssl_options main "string list" "+no_sslv2"
15049 .cindex "OpenSSL "compatibility options"
15050 This option allows an administrator to adjust the SSL options applied
15051 by OpenSSL to connections. It is given as a space-separated list of items,
15052 each one to be +added or -subtracted from the current value.
15054 This option is only available if Exim is built against OpenSSL. The values
15055 available for this option vary according to the age of your OpenSSL install.
15056 The &"all"& value controls a subset of flags which are available, typically
15057 the bug workaround options. The &'SSL_CTX_set_options'& man page will
15058 list the values known on your system and Exim should support all the
15059 &"bug workaround"& options and many of the &"modifying"& options. The Exim
15060 names lose the leading &"SSL_OP_"& and are lower-cased.
15062 Note that adjusting the options can have severe impact upon the security of
15063 SSL as used by Exim. It is possible to disable safety checks and shoot
15064 yourself in the foot in various unpleasant ways. This option should not be
15065 adjusted lightly. An unrecognised item will be detected at startup, by
15066 invoking Exim with the &%-bV%& flag.
15068 The option affects Exim operating both as a server and as a client.
15070 Historical note: prior to release 4.80, Exim defaulted this value to
15071 "+dont_insert_empty_fragments", which may still be needed for compatibility
15072 with some clients, but which lowers security by increasing exposure to
15073 some now infamous attacks.
15077 # Make both old MS and old Eudora happy:
15078 openssl_options = -all +microsoft_big_sslv3_buffer \
15079 +dont_insert_empty_fragments
15081 # Disable older protocol versions:
15082 openssl_options = +no_sslv2 +no_sslv3
15085 Possible options may include:
15089 &`allow_unsafe_legacy_renegotiation`&
15091 &`cipher_server_preference`&
15093 &`dont_insert_empty_fragments`&
15097 &`legacy_server_connect`&
15099 &`microsoft_big_sslv3_buffer`&
15101 &`microsoft_sess_id_bug`&
15103 &`msie_sslv2_rsa_padding`&
15105 &`netscape_challenge_bug`&
15107 &`netscape_reuse_cipher_change_bug`&
15111 &`no_session_resumption_on_renegotiation`&
15125 &`safari_ecdhe_ecdsa_bug`&
15129 &`single_ecdh_use`&
15131 &`ssleay_080_client_dh_bug`&
15133 &`sslref2_reuse_cert_type_bug`&
15135 &`tls_block_padding_bug`&
15139 &`tls_rollback_bug`&
15142 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
15143 all clients connecting using the MacOS SecureTransport TLS facility prior
15144 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
15145 to negotiate TLS then this option value might help, provided that your OpenSSL
15146 release is new enough to contain this work-around. This may be a situation
15147 where you have to upgrade OpenSSL to get buggy clients working.
15150 .option oracle_servers main "string list" unset
15151 .cindex "Oracle" "server list"
15152 This option provides a list of Oracle servers and associated connection data,
15153 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
15154 The option is available only if Exim has been built with Oracle support.
15157 .option percent_hack_domains main "domain list&!!" unset
15158 .cindex "&""percent hack""&"
15159 .cindex "source routing" "in email address"
15160 .cindex "address" "source-routed"
15161 The &"percent hack"& is the convention whereby a local part containing a
15162 percent sign is re-interpreted as a new email address, with the percent
15163 replaced by @. This is sometimes called &"source routing"&, though that term is
15164 also applied to RFC 2822 addresses that begin with an @ character. If this
15165 option is set, Exim implements the percent facility for those domains listed,
15166 but no others. This happens before an incoming SMTP address is tested against
15169 &*Warning*&: The &"percent hack"& has often been abused by people who are
15170 trying to get round relaying restrictions. For this reason, it is best avoided
15171 if at all possible. Unfortunately, a number of less security-conscious MTAs
15172 implement it unconditionally. If you are running Exim on a gateway host, and
15173 routing mail through to internal MTAs without processing the local parts, it is
15174 a good idea to reject recipient addresses with percent characters in their
15175 local parts. Exim's default configuration does this.
15178 .option perl_at_start main boolean false
15179 This option is available only when Exim is built with an embedded Perl
15180 interpreter. See chapter &<<CHAPperl>>& for details of its use.
15183 .option perl_startup main string unset
15184 This option is available only when Exim is built with an embedded Perl
15185 interpreter. See chapter &<<CHAPperl>>& for details of its use.
15188 .option pgsql_servers main "string list" unset
15189 .cindex "PostgreSQL lookup type" "server list"
15190 This option provides a list of PostgreSQL servers and associated connection
15191 data, to be used in conjunction with &(pgsql)& lookups (see section
15192 &<<SECID72>>&). The option is available only if Exim has been built with
15193 PostgreSQL support.
15196 .option pid_file_path main string&!! "set at compile time"
15197 .cindex "daemon" "pid file path"
15198 .cindex "pid file, path for"
15199 This option sets the name of the file to which the Exim daemon writes its
15200 process id. The string is expanded, so it can contain, for example, references
15203 pid_file_path = /var/log/$primary_hostname/exim.pid
15205 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
15207 The value set by the option can be overridden by the &%-oP%& command line
15208 option. A pid file is not written if a &"non-standard"& daemon is run by means
15209 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
15212 .option pipelining_advertise_hosts main "host list&!!" *
15213 .cindex "PIPELINING" "suppressing advertising"
15214 This option can be used to suppress the advertisement of the SMTP
15215 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
15216 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
15217 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
15218 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
15219 that clients will use it; &"out of order"& commands that are &"expected"& do
15220 not count as protocol errors (see &%smtp_max_synprot_errors%&).
15223 .option prdr_enable main boolean false
15224 .cindex "PRDR" "enabling on server"
15225 This option can be used to enable the Per-Recipient Data Response extension
15226 to SMTP, defined by Eric Hall.
15227 If the option is set, PRDR is advertised by Exim when operating as a server.
15228 If the client requests PRDR, and more than one recipient, for a message
15229 an additional ACL is called for each recipient after the message content
15230 is recieved. See section &<<SECTPRDRACL>>&.
15232 .option preserve_message_logs main boolean false
15233 .cindex "message logs" "preserving"
15234 If this option is set, message log files are not deleted when messages are
15235 completed. Instead, they are moved to a sub-directory of the spool directory
15236 called &_msglog.OLD_&, where they remain available for statistical or debugging
15237 purposes. This is a dangerous option to set on systems with any appreciable
15238 volume of mail. Use with care!
15241 .option primary_hostname main string "see below"
15242 .cindex "name" "of local host"
15243 .cindex "host" "name of local"
15244 .cindex "local host" "name of"
15245 .vindex "&$primary_hostname$&"
15246 This specifies the name of the current host. It is used in the default EHLO or
15247 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
15248 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
15249 The value is also used by default in some SMTP response messages from an Exim
15250 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
15252 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
15253 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
15254 contains only one component, Exim passes it to &[gethostbyname()]& (or
15255 &[getipnodebyname()]& when available) in order to obtain the fully qualified
15256 version. The variable &$primary_hostname$& contains the host name, whether set
15257 explicitly by this option, or defaulted.
15260 .option print_topbitchars main boolean false
15261 .cindex "printing characters"
15262 .cindex "8-bit characters"
15263 By default, Exim considers only those characters whose codes lie in the range
15264 32&--126 to be printing characters. In a number of circumstances (for example,
15265 when writing log entries) non-printing characters are converted into escape
15266 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
15267 is set, code values of 128 and above are also considered to be printing
15270 This option also affects the header syntax checks performed by the
15271 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
15272 the user's full name when constructing From: and Sender: addresses (as
15273 described in section &<<SECTconstr>>&). Setting this option can cause
15274 Exim to generate eight bit message headers that do not conform to the
15278 .option process_log_path main string unset
15279 .cindex "process log path"
15280 .cindex "log" "process log"
15281 .cindex "&'exiwhat'&"
15282 This option sets the name of the file to which an Exim process writes its
15283 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
15284 utility script. If this option is unset, the file called &_exim-process.info_&
15285 in Exim's spool directory is used. The ability to specify the name explicitly
15286 can be useful in environments where two different Exims are running, using
15287 different spool directories.
15290 .option prod_requires_admin main boolean true
15294 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
15295 admin user unless &%prod_requires_admin%& is set false. See also
15296 &%queue_list_requires_admin%&.
15299 .option qualify_domain main string "see below"
15300 .cindex "domain" "for qualifying addresses"
15301 .cindex "address" "qualification"
15302 This option specifies the domain name that is added to any envelope sender
15303 addresses that do not have a domain qualification. It also applies to
15304 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
15305 are accepted by default only for locally-generated messages. Qualification is
15306 also applied to addresses in header lines such as &'From:'& and &'To:'& for
15307 locally-generated messages, unless the &%-bnq%& command line option is used.
15309 Messages from external sources must always contain fully qualified addresses,
15310 unless the sending host matches &%sender_unqualified_hosts%& or
15311 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
15312 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
15313 necessary. Internally, Exim always works with fully qualified envelope
15314 addresses. If &%qualify_domain%& is not set, it defaults to the
15315 &%primary_hostname%& value.
15318 .option qualify_recipient main string "see below"
15319 This option allows you to specify a different domain for qualifying recipient
15320 addresses to the one that is used for senders. See &%qualify_domain%& above.
15324 .option queue_domains main "domain list&!!" unset
15325 .cindex "domain" "specifying non-immediate delivery"
15326 .cindex "queueing incoming messages"
15327 .cindex "message" "queueing certain domains"
15328 This option lists domains for which immediate delivery is not required.
15329 A delivery process is started whenever a message is received, but only those
15330 domains that do not match are processed. All other deliveries wait until the
15331 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
15334 .option queue_list_requires_admin main boolean true
15336 The &%-bp%& command-line option, which lists the messages that are on the
15337 queue, requires the caller to be an admin user unless
15338 &%queue_list_requires_admin%& is set false. See also &%prod_requires_admin%&.
15341 .option queue_only main boolean false
15342 .cindex "queueing incoming messages"
15343 .cindex "message" "queueing unconditionally"
15344 If &%queue_only%& is set, a delivery process is not automatically started
15345 whenever a message is received. Instead, the message waits on the queue for the
15346 next queue run. Even if &%queue_only%& is false, incoming messages may not get
15347 delivered immediately when certain conditions (such as heavy load) occur.
15349 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
15350 and &%-odi%& command line options override &%queue_only%& unless
15351 &%queue_only_override%& is set false. See also &%queue_only_file%&,
15352 &%queue_only_load%&, and &%smtp_accept_queue%&.
15355 .option queue_only_file main string unset
15356 .cindex "queueing incoming messages"
15357 .cindex "message" "queueing by file existence"
15358 This option can be set to a colon-separated list of absolute path names, each
15359 one optionally preceded by &"smtp"&. When Exim is receiving a message,
15360 it tests for the existence of each listed path using a call to &[stat()]&. For
15361 each path that exists, the corresponding queueing option is set.
15362 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
15363 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
15365 queue_only_file = smtp/some/file
15367 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
15368 &_/some/file_& exists.
15371 .option queue_only_load main fixed-point unset
15372 .cindex "load average"
15373 .cindex "queueing incoming messages"
15374 .cindex "message" "queueing by load"
15375 If the system load average is higher than this value, incoming messages from
15376 all sources are queued, and no automatic deliveries are started. If this
15377 happens during local or remote SMTP input, all subsequent messages received on
15378 the same SMTP connection are queued by default, whatever happens to the load in
15379 the meantime, but this can be changed by setting &%queue_only_load_latch%&
15382 Deliveries will subsequently be performed by queue runner processes. This
15383 option has no effect on ancient operating systems on which Exim cannot
15384 determine the load average. See also &%deliver_queue_load_max%& and
15385 &%smtp_load_reserve%&.
15388 .option queue_only_load_latch main boolean true
15389 .cindex "load average" "re-evaluating per message"
15390 When this option is true (the default), once one message has been queued
15391 because the load average is higher than the value set by &%queue_only_load%&,
15392 all subsequent messages received on the same SMTP connection are also queued.
15393 This is a deliberate choice; even though the load average may fall below the
15394 threshold, it doesn't seem right to deliver later messages on the same
15395 connection when not delivering earlier ones. However, there are special
15396 circumstances such as very long-lived connections from scanning appliances
15397 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
15398 should be set false. This causes the value of the load average to be
15399 re-evaluated for each message.
15402 .option queue_only_override main boolean true
15403 .cindex "queueing incoming messages"
15404 When this option is true, the &%-od%&&'x'& command line options override the
15405 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
15406 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
15407 to override; they are accepted, but ignored.
15410 .option queue_run_in_order main boolean false
15411 .cindex "queue runner" "processing messages in order"
15412 If this option is set, queue runs happen in order of message arrival instead of
15413 in an arbitrary order. For this to happen, a complete list of the entire queue
15414 must be set up before the deliveries start. When the queue is all held in a
15415 single directory (the default), a single list is created for both the ordered
15416 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
15417 single list is not created when &%queue_run_in_order%& is false. In this case,
15418 the sub-directories are processed one at a time (in a random order), and this
15419 avoids setting up one huge list for the whole queue. Thus, setting
15420 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
15421 when the queue is large, because of the extra work in setting up the single,
15422 large list. In most situations, &%queue_run_in_order%& should not be set.
15426 .option queue_run_max main integer 5
15427 .cindex "queue runner" "maximum number of"
15428 This controls the maximum number of queue runner processes that an Exim daemon
15429 can run simultaneously. This does not mean that it starts them all at once,
15430 but rather that if the maximum number are still running when the time comes to
15431 start another one, it refrains from starting another one. This can happen with
15432 very large queues and/or very sluggish deliveries. This option does not,
15433 however, interlock with other processes, so additional queue runners can be
15434 started by other means, or by killing and restarting the daemon.
15436 Setting this option to zero does not suppress queue runs; rather, it disables
15437 the limit, allowing any number of simultaneous queue runner processes to be
15438 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
15439 the daemon's command line.
15441 .option queue_smtp_domains main "domain list&!!" unset
15442 .cindex "queueing incoming messages"
15443 .cindex "message" "queueing remote deliveries"
15444 When this option is set, a delivery process is started whenever a message is
15445 received, routing is performed, and local deliveries take place.
15446 However, if any SMTP deliveries are required for domains that match
15447 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
15448 message waits on the queue for the next queue run. Since routing of the message
15449 has taken place, Exim knows to which remote hosts it must be delivered, and so
15450 when the queue run happens, multiple messages for the same host are delivered
15451 over a single SMTP connection. The &%-odqs%& command line option causes all
15452 SMTP deliveries to be queued in this way, and is equivalent to setting
15453 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
15457 .option receive_timeout main time 0s
15458 .cindex "timeout" "for non-SMTP input"
15459 This option sets the timeout for accepting a non-SMTP message, that is, the
15460 maximum time that Exim waits when reading a message on the standard input. If
15461 the value is zero, it will wait for ever. This setting is overridden by the
15462 &%-or%& command line option. The timeout for incoming SMTP messages is
15463 controlled by &%smtp_receive_timeout%&.
15465 .option received_header_text main string&!! "see below"
15466 .cindex "customizing" "&'Received:'& header"
15467 .cindex "&'Received:'& header line" "customizing"
15468 This string defines the contents of the &'Received:'& message header that is
15469 added to each message, except for the timestamp, which is automatically added
15470 on at the end (preceded by a semicolon). The string is expanded each time it is
15471 used. If the expansion yields an empty string, no &'Received:'& header line is
15472 added to the message. Otherwise, the string should start with the text
15473 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
15474 header lines. The default setting is:
15477 received_header_text = Received: \
15478 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
15479 {${if def:sender_ident \
15480 {from ${quote_local_part:$sender_ident} }}\
15481 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
15482 by $primary_hostname \
15483 ${if def:received_protocol {with $received_protocol}} \
15484 ${if def:tls_in_cipher {($tls_in_cipher)\n\t}}\
15485 (Exim $version_number)\n\t\
15486 ${if def:sender_address \
15487 {(envelope-from <$sender_address>)\n\t}}\
15488 id $message_exim_id\
15489 ${if def:received_for {\n\tfor $received_for}}
15492 The reference to the TLS cipher is omitted when Exim is built without TLS
15493 support. The use of conditional expansions ensures that this works for both
15494 locally generated messages and messages received from remote hosts, giving
15495 header lines such as the following:
15497 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
15498 by marley.carol.example with esmtp (Exim 4.00)
15499 (envelope-from <bob@carol.example>)
15500 id 16IOWa-00019l-00
15501 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
15502 Received: by scrooge.carol.example with local (Exim 4.00)
15503 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
15505 Until the body of the message has been received, the timestamp is the time when
15506 the message started to be received. Once the body has arrived, and all policy
15507 checks have taken place, the timestamp is updated to the time at which the
15508 message was accepted.
15511 .option received_headers_max main integer 30
15512 .cindex "loop" "prevention"
15513 .cindex "mail loop prevention"
15514 .cindex "&'Received:'& header line" "counting"
15515 When a message is to be delivered, the number of &'Received:'& headers is
15516 counted, and if it is greater than this parameter, a mail loop is assumed to
15517 have occurred, the delivery is abandoned, and an error message is generated.
15518 This applies to both local and remote deliveries.
15521 .option recipient_unqualified_hosts main "host list&!!" unset
15522 .cindex "unqualified addresses"
15523 .cindex "host" "unqualified addresses from"
15524 This option lists those hosts from which Exim is prepared to accept unqualified
15525 recipient addresses in message envelopes. The addresses are made fully
15526 qualified by the addition of the &%qualify_recipient%& value. This option also
15527 affects message header lines. Exim does not reject unqualified recipient
15528 addresses in headers, but it qualifies them only if the message came from a
15529 host that matches &%recipient_unqualified_hosts%&,
15530 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
15531 option was not set.
15534 .option recipients_max main integer 0
15535 .cindex "limit" "number of recipients"
15536 .cindex "recipient" "maximum number"
15537 If this option is set greater than zero, it specifies the maximum number of
15538 original recipients for any message. Additional recipients that are generated
15539 by aliasing or forwarding do not count. SMTP messages get a 452 response for
15540 all recipients over the limit; earlier recipients are delivered as normal.
15541 Non-SMTP messages with too many recipients are failed, and no deliveries are
15544 .cindex "RCPT" "maximum number of incoming"
15545 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
15546 RCPT commands in a single message.
15549 .option recipients_max_reject main boolean false
15550 If this option is set true, Exim rejects SMTP messages containing too many
15551 recipients by giving 552 errors to the surplus RCPT commands, and a 554
15552 error to the eventual DATA command. Otherwise (the default) it gives a 452
15553 error to the surplus RCPT commands and accepts the message on behalf of the
15554 initial set of recipients. The remote server should then re-send the message
15555 for the remaining recipients at a later time.
15558 .option remote_max_parallel main integer 2
15559 .cindex "delivery" "parallelism for remote"
15560 This option controls parallel delivery of one message to a number of remote
15561 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
15562 does all the remote deliveries for a message one by one. Otherwise, if a single
15563 message has to be delivered to more than one remote host, or if several copies
15564 have to be sent to the same remote host, up to &%remote_max_parallel%&
15565 deliveries are done simultaneously. If more than &%remote_max_parallel%&
15566 deliveries are required, the maximum number of processes are started, and as
15567 each one finishes, another is begun. The order of starting processes is the
15568 same as if sequential delivery were being done, and can be controlled by the
15569 &%remote_sort_domains%& option. If parallel delivery takes place while running
15570 with debugging turned on, the debugging output from each delivery process is
15571 tagged with its process id.
15573 This option controls only the maximum number of parallel deliveries for one
15574 message in one Exim delivery process. Because Exim has no central queue
15575 manager, there is no way of controlling the total number of simultaneous
15576 deliveries if the configuration allows a delivery attempt as soon as a message
15579 .cindex "number of deliveries"
15580 .cindex "delivery" "maximum number of"
15581 If you want to control the total number of deliveries on the system, you
15582 need to set the &%queue_only%& option. This ensures that all incoming messages
15583 are added to the queue without starting a delivery process. Then set up an Exim
15584 daemon to start queue runner processes at appropriate intervals (probably
15585 fairly often, for example, every minute), and limit the total number of queue
15586 runners by setting the &%queue_run_max%& parameter. Because each queue runner
15587 delivers only one message at a time, the maximum number of deliveries that can
15588 then take place at once is &%queue_run_max%& multiplied by
15589 &%remote_max_parallel%&.
15591 If it is purely remote deliveries you want to control, use
15592 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
15593 doing the SMTP routing before queueing, so that several messages for the same
15594 host will eventually get delivered down the same connection.
15597 .option remote_sort_domains main "domain list&!!" unset
15598 .cindex "sorting remote deliveries"
15599 .cindex "delivery" "sorting remote"
15600 When there are a number of remote deliveries for a message, they are sorted by
15601 domain into the order given by this list. For example,
15603 remote_sort_domains = *.cam.ac.uk:*.uk
15605 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
15606 then to those in the &%uk%& domain, then to any others.
15609 .option retry_data_expire main time 7d
15610 .cindex "hints database" "data expiry"
15611 This option sets a &"use before"& time on retry information in Exim's hints
15612 database. Any older retry data is ignored. This means that, for example, once a
15613 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
15617 .option retry_interval_max main time 24h
15618 .cindex "retry" "limit on interval"
15619 .cindex "limit" "on retry interval"
15620 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
15621 intervals between delivery attempts for messages that cannot be delivered
15622 straight away. This option sets an overall limit to the length of time between
15623 retries. It cannot be set greater than 24 hours; any attempt to do so forces
15627 .option return_path_remove main boolean true
15628 .cindex "&'Return-path:'& header line" "removing"
15629 RFC 2821, section 4.4, states that an SMTP server must insert a
15630 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
15631 The &'Return-path:'& header preserves the sender address as received in the
15632 MAIL command. This description implies that this header should not be present
15633 in an incoming message. If &%return_path_remove%& is true, any existing
15634 &'Return-path:'& headers are removed from messages at the time they are
15635 received. Exim's transports have options for adding &'Return-path:'& headers at
15636 the time of delivery. They are normally used only for final local deliveries.
15639 .option return_size_limit main integer 100K
15640 This option is an obsolete synonym for &%bounce_return_size_limit%&.
15643 .option rfc1413_hosts main "host list&!!" *
15645 .cindex "host" "for RFC 1413 calls"
15646 RFC 1413 identification calls are made to any client host which matches an item
15649 .option rfc1413_query_timeout main time 5s
15650 .cindex "RFC 1413" "query timeout"
15651 .cindex "timeout" "for RFC 1413 call"
15652 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
15653 no RFC 1413 calls are ever made.
15656 .option sender_unqualified_hosts main "host list&!!" unset
15657 .cindex "unqualified addresses"
15658 .cindex "host" "unqualified addresses from"
15659 This option lists those hosts from which Exim is prepared to accept unqualified
15660 sender addresses. The addresses are made fully qualified by the addition of
15661 &%qualify_domain%&. This option also affects message header lines. Exim does
15662 not reject unqualified addresses in headers that contain sender addresses, but
15663 it qualifies them only if the message came from a host that matches
15664 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
15665 using TCP/IP), and the &%-bnq%& option was not set.
15668 .option smtp_accept_keepalive main boolean true
15669 .cindex "keepalive" "on incoming connection"
15670 This option controls the setting of the SO_KEEPALIVE option on incoming
15671 TCP/IP socket connections. When set, it causes the kernel to probe idle
15672 connections periodically, by sending packets with &"old"& sequence numbers. The
15673 other end of the connection should send an acknowledgment if the connection is
15674 still okay or a reset if the connection has been aborted. The reason for doing
15675 this is that it has the beneficial effect of freeing up certain types of
15676 connection that can get stuck when the remote host is disconnected without
15677 tidying up the TCP/IP call properly. The keepalive mechanism takes several
15678 hours to detect unreachable hosts.
15682 .option smtp_accept_max main integer 20
15683 .cindex "limit" "incoming SMTP connections"
15684 .cindex "SMTP" "incoming connection count"
15686 This option specifies the maximum number of simultaneous incoming SMTP calls
15687 that Exim will accept. It applies only to the listening daemon; there is no
15688 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
15689 value is set to zero, no limit is applied. However, it is required to be
15690 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
15691 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
15693 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
15694 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
15695 that limit has not been reached for the client host, &%smtp_accept_reserve%&
15696 and &%smtp_load_reserve%& are then checked before accepting the connection.
15699 .option smtp_accept_max_nonmail main integer 10
15700 .cindex "limit" "non-mail SMTP commands"
15701 .cindex "SMTP" "limiting non-mail commands"
15702 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
15703 the connection if there are too many. This option defines &"too many"&. The
15704 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
15705 client looping sending EHLO, for example. The check is applied only if the
15706 client host matches &%smtp_accept_max_nonmail_hosts%&.
15708 When a new message is expected, one occurrence of RSET is not counted. This
15709 allows a client to send one RSET between messages (this is not necessary,
15710 but some clients do it). Exim also allows one uncounted occurrence of HELO
15711 or EHLO, and one occurrence of STARTTLS between messages. After
15712 starting up a TLS session, another EHLO is expected, and so it too is not
15713 counted. The first occurrence of AUTH in a connection, or immediately
15714 following STARTTLS is not counted. Otherwise, all commands other than
15715 MAIL, RCPT, DATA, and QUIT are counted.
15718 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
15719 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
15720 check by setting this option. The default value makes it apply to all hosts. By
15721 changing the value, you can exclude any badly-behaved hosts that you have to
15725 . Allow this long option name to split; give it unsplit as a fifth argument
15726 . for the automatic .oindex that is generated by .option.
15727 . We insert " &~&~" which is both pretty nasty visually and results in
15728 . non-searchable text. HowItWorks.txt mentions an option for inserting
15729 . zero-width-space, which would be nicer visually and results in (at least)
15730 . html that Firefox will split on when it's forced to reflow (rather than
15731 . inserting a horizontal scrollbar). However, the text is still not
15732 . searchable. NM changed this occurrence for bug 1197 to no longer allow
15733 . the option name to split.
15735 .option "smtp_accept_max_per_connection" main integer 1000 &&&
15736 smtp_accept_max_per_connection
15737 .cindex "SMTP" "limiting incoming message count"
15738 .cindex "limit" "messages per SMTP connection"
15739 The value of this option limits the number of MAIL commands that Exim is
15740 prepared to accept over a single SMTP connection, whether or not each command
15741 results in the transfer of a message. After the limit is reached, a 421
15742 response is given to subsequent MAIL commands. This limit is a safety
15743 precaution against a client that goes mad (incidents of this type have been
15747 .option smtp_accept_max_per_host main string&!! unset
15748 .cindex "limit" "SMTP connections from one host"
15749 .cindex "host" "limiting SMTP connections from"
15750 This option restricts the number of simultaneous IP connections from a single
15751 host (strictly, from a single IP address) to the Exim daemon. The option is
15752 expanded, to enable different limits to be applied to different hosts by
15753 reference to &$sender_host_address$&. Once the limit is reached, additional
15754 connection attempts from the same host are rejected with error code 421. This
15755 is entirely independent of &%smtp_accept_reserve%&. The option's default value
15756 of zero imposes no limit. If this option is set greater than zero, it is
15757 required that &%smtp_accept_max%& be non-zero.
15759 &*Warning*&: When setting this option you should not use any expansion
15760 constructions that take an appreciable amount of time. The expansion and test
15761 happen in the main daemon loop, in order to reject additional connections
15762 without forking additional processes (otherwise a denial-of-service attack
15763 could cause a vast number or processes to be created). While the daemon is
15764 doing this processing, it cannot accept any other incoming connections.
15768 .option smtp_accept_queue main integer 0
15769 .cindex "SMTP" "incoming connection count"
15770 .cindex "queueing incoming messages"
15771 .cindex "message" "queueing by SMTP connection count"
15772 If the number of simultaneous incoming SMTP connections being handled via the
15773 listening daemon exceeds this value, messages received by SMTP are just placed
15774 on the queue; no delivery processes are started automatically. The count is
15775 fixed at the start of an SMTP connection. It cannot be updated in the
15776 subprocess that receives messages, and so the queueing or not queueing applies
15777 to all messages received in the same connection.
15779 A value of zero implies no limit, and clearly any non-zero value is useful only
15780 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
15781 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
15782 various &%-od%&&'x'& command line options.
15785 . See the comment on smtp_accept_max_per_connection
15787 .option "smtp_accept_queue_per_connection" main integer 10 &&&
15788 smtp_accept_queue_per_connection
15789 .cindex "queueing incoming messages"
15790 .cindex "message" "queueing by message count"
15791 This option limits the number of delivery processes that Exim starts
15792 automatically when receiving messages via SMTP, whether via the daemon or by
15793 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
15794 and the number of messages received in a single SMTP session exceeds this
15795 number, subsequent messages are placed on the queue, but no delivery processes
15796 are started. This helps to limit the number of Exim processes when a server
15797 restarts after downtime and there is a lot of mail waiting for it on other
15798 systems. On large systems, the default should probably be increased, and on
15799 dial-in client systems it should probably be set to zero (that is, disabled).
15802 .option smtp_accept_reserve main integer 0
15803 .cindex "SMTP" "incoming call count"
15804 .cindex "host" "reserved"
15805 When &%smtp_accept_max%& is set greater than zero, this option specifies a
15806 number of SMTP connections that are reserved for connections from the hosts
15807 that are specified in &%smtp_reserve_hosts%&. The value set in
15808 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
15809 restricted to this number of connections; the option specifies a minimum number
15810 of connection slots for them, not a maximum. It is a guarantee that this group
15811 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
15812 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
15815 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
15816 set to 5, once there are 45 active connections (from any hosts), new
15817 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
15818 provided the other criteria for acceptance are met.
15821 .option smtp_active_hostname main string&!! unset
15822 .cindex "host" "name in SMTP responses"
15823 .cindex "SMTP" "host name in responses"
15824 .vindex "&$primary_hostname$&"
15825 This option is provided for multi-homed servers that want to masquerade as
15826 several different hosts. At the start of an incoming SMTP connection, its value
15827 is expanded and used instead of the value of &$primary_hostname$& in SMTP
15828 responses. For example, it is used as domain name in the response to an
15829 incoming HELO or EHLO command.
15831 .vindex "&$smtp_active_hostname$&"
15832 The active hostname is placed in the &$smtp_active_hostname$& variable, which
15833 is saved with any messages that are received. It is therefore available for use
15834 in routers and transports when the message is later delivered.
15836 If this option is unset, or if its expansion is forced to fail, or if the
15837 expansion results in an empty string, the value of &$primary_hostname$& is
15838 used. Other expansion failures cause a message to be written to the main and
15839 panic logs, and the SMTP command receives a temporary error. Typically, the
15840 value of &%smtp_active_hostname%& depends on the incoming interface address.
15843 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
15844 {cox.mydomain}{box.mydomain}}
15847 Although &$smtp_active_hostname$& is primarily concerned with incoming
15848 messages, it is also used as the default for HELO commands in callout
15849 verification if there is no remote transport from which to obtain a
15850 &%helo_data%& value.
15852 .option smtp_banner main string&!! "see below"
15853 .cindex "SMTP" "welcome banner"
15854 .cindex "banner for SMTP"
15855 .cindex "welcome banner for SMTP"
15856 .cindex "customizing" "SMTP banner"
15857 This string, which is expanded every time it is used, is output as the initial
15858 positive response to an SMTP connection. The default setting is:
15860 smtp_banner = $smtp_active_hostname ESMTP Exim \
15861 $version_number $tod_full
15863 Failure to expand the string causes a panic error. If you want to create a
15864 multiline response to the initial SMTP connection, use &"\n"& in the string at
15865 appropriate points, but not at the end. Note that the 220 code is not included
15866 in this string. Exim adds it automatically (several times in the case of a
15867 multiline response).
15870 .option smtp_check_spool_space main boolean true
15871 .cindex "checking disk space"
15872 .cindex "disk space, checking"
15873 .cindex "spool directory" "checking space"
15874 When this option is set, if an incoming SMTP session encounters the SIZE
15875 option on a MAIL command, it checks that there is enough space in the
15876 spool directory's partition to accept a message of that size, while still
15877 leaving free the amount specified by &%check_spool_space%& (even if that value
15878 is zero). If there isn't enough space, a temporary error code is returned.
15881 .option smtp_connect_backlog main integer 20
15882 .cindex "connection backlog"
15883 .cindex "SMTP" "connection backlog"
15884 .cindex "backlog of connections"
15885 This option specifies a maximum number of waiting SMTP connections. Exim passes
15886 this value to the TCP/IP system when it sets up its listener. Once this number
15887 of connections are waiting for the daemon's attention, subsequent connection
15888 attempts are refused at the TCP/IP level. At least, that is what the manuals
15889 say; in some circumstances such connection attempts have been observed to time
15890 out instead. For large systems it is probably a good idea to increase the
15891 value (to 50, say). It also gives some protection against denial-of-service
15892 attacks by SYN flooding.
15895 .option smtp_enforce_sync main boolean true
15896 .cindex "SMTP" "synchronization checking"
15897 .cindex "synchronization checking in SMTP"
15898 The SMTP protocol specification requires the client to wait for a response from
15899 the server at certain points in the dialogue. Without PIPELINING these
15900 synchronization points are after every command; with PIPELINING they are
15901 fewer, but they still exist.
15903 Some spamming sites send out a complete set of SMTP commands without waiting
15904 for any response. Exim protects against this by rejecting a message if the
15905 client has sent further input when it should not have. The error response &"554
15906 SMTP synchronization error"& is sent, and the connection is dropped. Testing
15907 for this error cannot be perfect because of transmission delays (unexpected
15908 input may be on its way but not yet received when Exim checks). However, it
15909 does detect many instances.
15911 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
15912 If you want to disable the check selectively (for example, only for certain
15913 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
15914 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
15918 .option smtp_etrn_command main string&!! unset
15919 .cindex "ETRN" "command to be run"
15920 .vindex "&$domain$&"
15921 If this option is set, the given command is run whenever an SMTP ETRN
15922 command is received from a host that is permitted to issue such commands (see
15923 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
15924 are independently expanded. The expansion variable &$domain$& is set to the
15925 argument of the ETRN command, and no syntax checking is done on it. For
15928 smtp_etrn_command = /etc/etrn_command $domain \
15929 $sender_host_address
15931 A new process is created to run the command, but Exim does not wait for it to
15932 complete. Consequently, its status cannot be checked. If the command cannot be
15933 run, a line is written to the panic log, but the ETRN caller still receives
15934 a 250 success response. Exim is normally running under its own uid when
15935 receiving SMTP, so it is not possible for it to change the uid before running
15939 .option smtp_etrn_serialize main boolean true
15940 .cindex "ETRN" "serializing"
15941 When this option is set, it prevents the simultaneous execution of more than
15942 one identical command as a result of ETRN in an SMTP connection. See
15943 section &<<SECTETRN>>& for details.
15946 .option smtp_load_reserve main fixed-point unset
15947 .cindex "load average"
15948 If the system load average ever gets higher than this, incoming SMTP calls are
15949 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
15950 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
15951 the load is over the limit. The option has no effect on ancient operating
15952 systems on which Exim cannot determine the load average. See also
15953 &%deliver_queue_load_max%& and &%queue_only_load%&.
15957 .option smtp_max_synprot_errors main integer 3
15958 .cindex "SMTP" "limiting syntax and protocol errors"
15959 .cindex "limit" "SMTP syntax and protocol errors"
15960 Exim rejects SMTP commands that contain syntax or protocol errors. In
15961 particular, a syntactically invalid email address, as in this command:
15963 RCPT TO:<abc xyz@a.b.c>
15965 causes immediate rejection of the command, before any other tests are done.
15966 (The ACL cannot be run if there is no valid address to set up for it.) An
15967 example of a protocol error is receiving RCPT before MAIL. If there are
15968 too many syntax or protocol errors in one SMTP session, the connection is
15969 dropped. The limit is set by this option.
15971 .cindex "PIPELINING" "expected errors"
15972 When the PIPELINING extension to SMTP is in use, some protocol errors are
15973 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
15974 Exim assumes that PIPELINING will be used if it advertises it (see
15975 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
15976 not count towards the limit.
15980 .option smtp_max_unknown_commands main integer 3
15981 .cindex "SMTP" "limiting unknown commands"
15982 .cindex "limit" "unknown SMTP commands"
15983 If there are too many unrecognized commands in an incoming SMTP session, an
15984 Exim server drops the connection. This is a defence against some kinds of abuse
15987 into making connections to SMTP ports; in these circumstances, a number of
15988 non-SMTP command lines are sent first.
15992 .option smtp_ratelimit_hosts main "host list&!!" unset
15993 .cindex "SMTP" "rate limiting"
15994 .cindex "limit" "rate of message arrival"
15995 .cindex "RCPT" "rate limiting"
15996 Some sites find it helpful to be able to limit the rate at which certain hosts
15997 can send them messages, and the rate at which an individual message can specify
16000 Exim has two rate-limiting facilities. This section describes the older
16001 facility, which can limit rates within a single connection. The newer
16002 &%ratelimit%& ACL condition can limit rates across all connections. See section
16003 &<<SECTratelimiting>>& for details of the newer facility.
16005 When a host matches &%smtp_ratelimit_hosts%&, the values of
16006 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
16007 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
16008 respectively. Each option, if set, must contain a set of four comma-separated
16012 A threshold, before which there is no rate limiting.
16014 An initial time delay. Unlike other times in Exim, numbers with decimal
16015 fractional parts are allowed here.
16017 A factor by which to increase the delay each time.
16019 A maximum value for the delay. This should normally be less than 5 minutes,
16020 because after that time, the client is liable to timeout the SMTP command.
16023 For example, these settings have been used successfully at the site which
16024 first suggested this feature, for controlling mail from their customers:
16026 smtp_ratelimit_mail = 2,0.5s,1.05,4m
16027 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
16029 The first setting specifies delays that are applied to MAIL commands after
16030 two have been received over a single connection. The initial delay is 0.5
16031 seconds, increasing by a factor of 1.05 each time. The second setting applies
16032 delays to RCPT commands when more than four occur in a single message.
16035 .option smtp_ratelimit_mail main string unset
16036 See &%smtp_ratelimit_hosts%& above.
16039 .option smtp_ratelimit_rcpt main string unset
16040 See &%smtp_ratelimit_hosts%& above.
16043 .option smtp_receive_timeout main time 5m
16044 .cindex "timeout" "for SMTP input"
16045 .cindex "SMTP" "input timeout"
16046 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
16047 input, including batch SMTP. If a line of input (either an SMTP command or a
16048 data line) is not received within this time, the SMTP connection is dropped and
16049 the message is abandoned.
16050 A line is written to the log containing one of the following messages:
16052 SMTP command timeout on connection from...
16053 SMTP data timeout on connection from...
16055 The former means that Exim was expecting to read an SMTP command; the latter
16056 means that it was in the DATA phase, reading the contents of a message.
16060 The value set by this option can be overridden by the
16061 &%-os%& command-line option. A setting of zero time disables the timeout, but
16062 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
16063 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
16064 timeout is controlled by &%receive_timeout%& and &%-or%&.
16067 .option smtp_reserve_hosts main "host list&!!" unset
16068 This option defines hosts for which SMTP connections are reserved; see
16069 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
16072 .option smtp_return_error_details main boolean false
16073 .cindex "SMTP" "details policy failures"
16074 .cindex "policy control" "rejection, returning details"
16075 In the default state, Exim uses bland messages such as
16076 &"Administrative prohibition"& when it rejects SMTP commands for policy
16077 reasons. Many sysadmins like this because it gives away little information
16078 to spammers. However, some other sysadmins who are applying strict checking
16079 policies want to give out much fuller information about failures. Setting
16080 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
16081 example, instead of &"Administrative prohibition"&, it might give:
16083 550-Rejected after DATA: '>' missing at end of address:
16084 550 failing address in "From" header is: <user@dom.ain
16087 .option spamd_address main string "see below"
16088 This option is available when Exim is compiled with the content-scanning
16089 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
16090 The default value is
16094 See section &<<SECTscanspamass>>& for more details.
16098 .option split_spool_directory main boolean false
16099 .cindex "multiple spool directories"
16100 .cindex "spool directory" "split"
16101 .cindex "directories, multiple"
16102 If this option is set, it causes Exim to split its input directory into 62
16103 subdirectories, each with a single alphanumeric character as its name. The
16104 sixth character of the message id is used to allocate messages to
16105 subdirectories; this is the least significant base-62 digit of the time of
16106 arrival of the message.
16108 Splitting up the spool in this way may provide better performance on systems
16109 where there are long mail queues, by reducing the number of files in any one
16110 directory. The msglog directory is also split up in a similar way to the input
16111 directory; however, if &%preserve_message_logs%& is set, all old msglog files
16112 are still placed in the single directory &_msglog.OLD_&.
16114 It is not necessary to take any special action for existing messages when
16115 changing &%split_spool_directory%&. Exim notices messages that are in the
16116 &"wrong"& place, and continues to process them. If the option is turned off
16117 after a period of being on, the subdirectories will eventually empty and be
16118 automatically deleted.
16120 When &%split_spool_directory%& is set, the behaviour of queue runner processes
16121 changes. Instead of creating a list of all messages in the queue, and then
16122 trying to deliver each one in turn, it constructs a list of those in one
16123 sub-directory and tries to deliver them, before moving on to the next
16124 sub-directory. The sub-directories are processed in a random order. This
16125 spreads out the scanning of the input directories, and uses less memory. It is
16126 particularly beneficial when there are lots of messages on the queue. However,
16127 if &%queue_run_in_order%& is set, none of this new processing happens. The
16128 entire queue has to be scanned and sorted before any deliveries can start.
16131 .option spool_directory main string&!! "set at compile time"
16132 .cindex "spool directory" "path to"
16133 This defines the directory in which Exim keeps its spool, that is, the messages
16134 it is waiting to deliver. The default value is taken from the compile-time
16135 configuration setting, if there is one. If not, this option must be set. The
16136 string is expanded, so it can contain, for example, a reference to
16137 &$primary_hostname$&.
16139 If the spool directory name is fixed on your installation, it is recommended
16140 that you set it at build time rather than from this option, particularly if the
16141 log files are being written to the spool directory (see &%log_file_path%&).
16142 Otherwise log files cannot be used for errors that are detected early on, such
16143 as failures in the configuration file.
16145 By using this option to override the compiled-in path, it is possible to run
16146 tests of Exim without using the standard spool.
16148 .option sqlite_lock_timeout main time 5s
16149 .cindex "sqlite lookup type" "lock timeout"
16150 This option controls the timeout that the &(sqlite)& lookup uses when trying to
16151 access an SQLite database. See section &<<SECTsqlite>>& for more details.
16153 .option strict_acl_vars main boolean false
16154 .cindex "&ACL;" "variables, handling unset"
16155 This option controls what happens if a syntactically valid but undefined ACL
16156 variable is referenced. If it is false (the default), an empty string
16157 is substituted; if it is true, an error is generated. See section
16158 &<<SECTaclvariables>>& for details of ACL variables.
16160 .option strip_excess_angle_brackets main boolean false
16161 .cindex "angle brackets, excess"
16162 If this option is set, redundant pairs of angle brackets round &"route-addr"&
16163 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
16164 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
16165 passed on to another MTA, the excess angle brackets are not passed on. If this
16166 option is not set, multiple pairs of angle brackets cause a syntax error.
16169 .option strip_trailing_dot main boolean false
16170 .cindex "trailing dot on domain"
16171 .cindex "dot" "trailing on domain"
16172 If this option is set, a trailing dot at the end of a domain in an address is
16173 ignored. If this is in the envelope and the message is passed on to another
16174 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
16175 domain causes a syntax error.
16176 However, addresses in header lines are checked only when an ACL requests header
16180 .option syslog_duplication main boolean true
16181 .cindex "syslog" "duplicate log lines; suppressing"
16182 When Exim is logging to syslog, it writes the log lines for its three
16183 separate logs at different syslog priorities so that they can in principle
16184 be separated on the logging hosts. Some installations do not require this
16185 separation, and in those cases, the duplication of certain log lines is a
16186 nuisance. If &%syslog_duplication%& is set false, only one copy of any
16187 particular log line is written to syslog. For lines that normally go to
16188 both the main log and the reject log, the reject log version (possibly
16189 containing message header lines) is written, at LOG_NOTICE priority.
16190 Lines that normally go to both the main and the panic log are written at
16191 the LOG_ALERT priority.
16194 .option syslog_facility main string unset
16195 .cindex "syslog" "facility; setting"
16196 This option sets the syslog &"facility"& name, used when Exim is logging to
16197 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
16198 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
16199 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
16200 details of Exim's logging.
16204 .option syslog_processname main string &`exim`&
16205 .cindex "syslog" "process name; setting"
16206 This option sets the syslog &"ident"& name, used when Exim is logging to
16207 syslog. The value must be no longer than 32 characters. See chapter
16208 &<<CHAPlog>>& for details of Exim's logging.
16212 .option syslog_timestamp main boolean true
16213 .cindex "syslog" "timestamps"
16214 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
16215 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
16216 details of Exim's logging.
16219 .option system_filter main string&!! unset
16220 .cindex "filter" "system filter"
16221 .cindex "system filter" "specifying"
16222 .cindex "Sieve filter" "not available for system filter"
16223 This option specifies an Exim filter file that is applied to all messages at
16224 the start of each delivery attempt, before any routing is done. System filters
16225 must be Exim filters; they cannot be Sieve filters. If the system filter
16226 generates any deliveries to files or pipes, or any new mail messages, the
16227 appropriate &%system_filter_..._transport%& option(s) must be set, to define
16228 which transports are to be used. Details of this facility are given in chapter
16229 &<<CHAPsystemfilter>>&.
16232 .option system_filter_directory_transport main string&!! unset
16233 .vindex "&$address_file$&"
16234 This sets the name of the transport driver that is to be used when the
16235 &%save%& command in a system message filter specifies a path ending in &"/"&,
16236 implying delivery of each message into a separate file in some directory.
16237 During the delivery, the variable &$address_file$& contains the path name.
16240 .option system_filter_file_transport main string&!! unset
16241 .cindex "file" "transport for system filter"
16242 This sets the name of the transport driver that is to be used when the &%save%&
16243 command in a system message filter specifies a path not ending in &"/"&. During
16244 the delivery, the variable &$address_file$& contains the path name.
16246 .option system_filter_group main string unset
16247 .cindex "gid (group id)" "system filter"
16248 This option is used only when &%system_filter_user%& is also set. It sets the
16249 gid under which the system filter is run, overriding any gid that is associated
16250 with the user. The value may be numerical or symbolic.
16252 .option system_filter_pipe_transport main string&!! unset
16253 .cindex "&(pipe)& transport" "for system filter"
16254 .vindex "&$address_pipe$&"
16255 This specifies the transport driver that is to be used when a &%pipe%& command
16256 is used in a system filter. During the delivery, the variable &$address_pipe$&
16257 contains the pipe command.
16260 .option system_filter_reply_transport main string&!! unset
16261 .cindex "&(autoreply)& transport" "for system filter"
16262 This specifies the transport driver that is to be used when a &%mail%& command
16263 is used in a system filter.
16266 .option system_filter_user main string unset
16267 .cindex "uid (user id)" "system filter"
16268 If this option is set to root, the system filter is run in the main Exim
16269 delivery process, as root. Otherwise, the system filter runs in a separate
16270 process, as the given user, defaulting to the Exim run-time user.
16271 Unless the string consists entirely of digits, it
16272 is looked up in the password data. Failure to find the named user causes a
16273 configuration error. The gid is either taken from the password data, or
16274 specified by &%system_filter_group%&. When the uid is specified numerically,
16275 &%system_filter_group%& is required to be set.
16277 If the system filter generates any pipe, file, or reply deliveries, the uid
16278 under which the filter is run is used when transporting them, unless a
16279 transport option overrides.
16282 .option tcp_nodelay main boolean true
16283 .cindex "daemon" "TCP_NODELAY on sockets"
16284 .cindex "Nagle algorithm"
16285 .cindex "TCP_NODELAY on listening sockets"
16286 If this option is set false, it stops the Exim daemon setting the
16287 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
16288 turns off the &"Nagle algorithm"&, which is a way of improving network
16289 performance in interactive (character-by-character) situations. Turning it off
16290 should improve Exim's performance a bit, so that is what happens by default.
16291 However, it appears that some broken clients cannot cope, and time out. Hence
16292 this option. It affects only those sockets that are set up for listening by the
16293 daemon. Sockets created by the smtp transport for delivering mail always set
16297 .option timeout_frozen_after main time 0s
16298 .cindex "frozen messages" "timing out"
16299 .cindex "timeout" "frozen messages"
16300 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
16301 message of any kind that has been on the queue for longer than the given time
16302 is automatically cancelled at the next queue run. If the frozen message is a
16303 bounce message, it is just discarded; otherwise, a bounce is sent to the
16304 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
16305 If you want to timeout frozen bounce messages earlier than other kinds of
16306 frozen message, see &%ignore_bounce_errors_after%&.
16308 &*Note:*& the default value of zero means no timeouts; with this setting,
16309 frozen messages remain on the queue forever (except for any frozen bounce
16310 messages that are released by &%ignore_bounce_errors_after%&).
16313 .option timezone main string unset
16314 .cindex "timezone, setting"
16315 The value of &%timezone%& is used to set the environment variable TZ while
16316 running Exim (if it is different on entry). This ensures that all timestamps
16317 created by Exim are in the required timezone. If you want all your timestamps
16318 to be in UTC (aka GMT) you should set
16322 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
16323 or, if that is not set, from the value of the TZ environment variable when Exim
16324 is built. If &%timezone%& is set to the empty string, either at build or run
16325 time, any existing TZ variable is removed from the environment when Exim
16326 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
16327 unfortunately not all, operating systems.
16330 .option tls_advertise_hosts main "host list&!!" unset
16331 .cindex "TLS" "advertising"
16332 .cindex "encryption" "on SMTP connection"
16333 .cindex "SMTP" "encrypted connection"
16334 When Exim is built with support for TLS encrypted connections, the availability
16335 of the STARTTLS command to set up an encrypted session is advertised in
16336 response to EHLO only to those client hosts that match this option. See
16337 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
16340 .option tls_certificate main string&!! unset
16341 .cindex "TLS" "server certificate; location of"
16342 .cindex "certificate" "server, location of"
16343 The value of this option is expanded, and must then be the absolute path to a
16344 file which contains the server's certificates. The server's private key is also
16345 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
16346 &<<CHAPTLS>>& for further details.
16348 &*Note*&: The certificates defined by this option are used only when Exim is
16349 receiving incoming messages as a server. If you want to supply certificates for
16350 use when sending messages as a client, you must set the &%tls_certificate%&
16351 option in the relevant &(smtp)& transport.
16353 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
16354 if the OpenSSL build supports TLS extensions and the TLS client sends the
16355 Server Name Indication extension, then this option and others documented in
16356 &<<SECTtlssni>>& will be re-expanded.
16358 .option tls_crl main string&!! unset
16359 .cindex "TLS" "server certificate revocation list"
16360 .cindex "certificate" "revocation list for server"
16361 This option specifies a certificate revocation list. The expanded value must
16362 be the name of a file that contains a CRL in PEM format.
16364 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
16367 .option tls_dh_max_bits main integer 2236
16368 .cindex "TLS" "D-H bit count"
16369 The number of bits used for Diffie-Hellman key-exchange may be suggested by
16370 the chosen TLS library. That value might prove to be too high for
16371 interoperability. This option provides a maximum clamp on the value
16372 suggested, trading off security for interoperability.
16374 The value must be at least 1024.
16376 The value 2236 was chosen because, at time of adding the option, it was the
16377 hard-coded maximum value supported by the NSS cryptographic library, as used
16378 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
16380 If you prefer more security and are willing to break some clients, raise this
16383 Note that the value passed to GnuTLS for *generating* a new prime may be a
16384 little less than this figure, because GnuTLS is inexact and may produce a
16385 larger prime than requested.
16388 .option tls_dhparam main string&!! unset
16389 .cindex "TLS" "D-H parameters for server"
16390 The value of this option is expanded and indicates the source of DH parameters
16391 to be used by Exim.
16393 If it is a filename starting with a &`/`&, then it names a file from which DH
16394 parameters should be loaded. If the file exists, it should hold a PEM-encoded
16395 PKCS#3 representation of the DH prime. If the file does not exist, for
16396 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
16397 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
16398 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
16399 and treated as though the &%tls_dhparam%& were set to "none".
16401 If this option expands to the string "none", then no DH parameters will be
16404 If this option expands to the string "historic" and Exim is using GnuTLS, then
16405 Exim will attempt to load a file from inside the spool directory. If the file
16406 does not exist, Exim will attempt to create it.
16407 See section &<<SECTgnutlsparam>>& for further details.
16409 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
16410 a default DH prime; the default is the 2048 bit prime described in section
16411 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
16412 in IKE is assigned number 23.
16414 Otherwise, the option must expand to the name used by Exim for any of a number
16415 of DH primes specified in RFC 2409, RFC 3526 and RFC 5114. As names, Exim uses
16416 "ike" followed by the number used by IKE, of "default" which corresponds to
16419 The available primes are:
16420 &`ike1`&, &`ike2`&, &`ike5`&,
16421 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
16422 &`ike22`&, &`ike23`& (aka &`default`&) and &`ike24`&.
16424 Some of these will be too small to be accepted by clients.
16425 Some may be too large to be accepted by clients.
16427 The TLS protocol does not negotiate an acceptable size for this; clients tend
16428 to hard-drop connections if what is offered by the server is unacceptable,
16429 whether too large or too small, and there's no provision for the client to
16430 tell the server what these constraints are. Thus, as a server operator, you
16431 need to make an educated guess as to what is most likely to work for your
16434 Some known size constraints suggest that a bit-size in the range 2048 to 2236
16435 is most likely to maximise interoperability. The upper bound comes from
16436 applications using the Mozilla Network Security Services (NSS) library, which
16437 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
16438 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
16439 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
16440 acceptable bound from 1024 to 2048.
16443 .option tls_ocsp_file main string&!! unset
16445 must if set expand to the absolute path to a file which contains a current
16446 status proof for the server's certificate, as obtained from the
16447 Certificate Authority.
16450 .option tls_on_connect_ports main "string list" unset
16451 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
16452 operate the obsolete SSMTP (SMTPS) protocol, where a TLS session is immediately
16453 set up without waiting for the client to issue a STARTTLS command. For
16454 further details, see section &<<SECTsupobssmt>>&.
16458 .option tls_privatekey main string&!! unset
16459 .cindex "TLS" "server private key; location of"
16460 The value of this option is expanded, and must then be the absolute path to a
16461 file which contains the server's private key. If this option is unset, or if
16462 the expansion is forced to fail, or the result is an empty string, the private
16463 key is assumed to be in the same file as the server's certificates. See chapter
16464 &<<CHAPTLS>>& for further details.
16466 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
16469 .option tls_remember_esmtp main boolean false
16470 .cindex "TLS" "esmtp state; remembering"
16471 .cindex "TLS" "broken clients"
16472 If this option is set true, Exim violates the RFCs by remembering that it is in
16473 &"esmtp"& state after successfully negotiating a TLS session. This provides
16474 support for broken clients that fail to send a new EHLO after starting a
16478 .option tls_require_ciphers main string&!! unset
16479 .cindex "TLS" "requiring specific ciphers"
16480 .cindex "cipher" "requiring specific"
16481 This option controls which ciphers can be used for incoming TLS connections.
16482 The &(smtp)& transport has an option of the same name for controlling outgoing
16483 connections. This option is expanded for each connection, so can be varied for
16484 different clients if required. The value of this option must be a list of
16485 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
16486 in somewhat different ways. If GnuTLS is being used, the client controls the
16487 preference order of the available ciphers. Details are given in sections
16488 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
16491 .option tls_try_verify_hosts main "host list&!!" unset
16492 .cindex "TLS" "client certificate verification"
16493 .cindex "certificate" "verification of client"
16494 See &%tls_verify_hosts%& below.
16497 .option tls_verify_certificates main string&!! system
16498 .cindex "TLS" "client certificate verification"
16499 .cindex "certificate" "verification of client"
16500 The value of this option is expanded, and must then be either the
16502 or the absolute path to
16503 a file or directory containing permitted certificates for clients that
16504 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
16506 The "system" value for the option will use a
16507 system default location compiled into the SSL library.
16508 This is not available for GnuTLS versions preceding 3.0.20,
16509 and will be taken as empty; an explicit location
16512 The use of a directory for the option value is not avilable for GnuTLS versions
16513 preceding 3.3.6 and a single file must be used.
16515 With OpenSSL the certificates specified
16517 either by file or directory
16518 are added to those given by the system default location.
16520 These certificates should be for the certificate authorities trusted, rather
16521 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
16522 the value is a file then the certificates are sent by Exim as a server to
16523 connecting clients, defining the list of accepted certificate authorities.
16524 Thus the values defined should be considered public data. To avoid this,
16525 use the explicit directory version.
16527 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
16529 A forced expansion failure or setting to an empty string is equivalent to
16533 .option tls_verify_hosts main "host list&!!" unset
16534 .cindex "TLS" "client certificate verification"
16535 .cindex "certificate" "verification of client"
16536 This option, along with &%tls_try_verify_hosts%&, controls the checking of
16537 certificates from clients. The expected certificates are defined by
16538 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
16539 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
16540 &%tls_verify_certificates%& is not set.
16542 Any client that matches &%tls_verify_hosts%& is constrained by
16543 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
16544 present one of the listed certificates. If it does not, the connection is
16545 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
16546 the host to use TLS. It can still send SMTP commands through unencrypted
16547 connections. Forcing a client to use TLS has to be done separately using an
16548 ACL to reject inappropriate commands when the connection is not encrypted.
16550 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
16551 matches this option (but not &%tls_verify_hosts%&), Exim requests a
16552 certificate and checks it against &%tls_verify_certificates%&, but does not
16553 abort the connection if there is no certificate or if it does not match. This
16554 state can be detected in an ACL, which makes it possible to implement policies
16555 such as &"accept for relay only if a verified certificate has been received,
16556 but accept for local delivery if encrypted, even without a verified
16559 Client hosts that match neither of these lists are not asked to present
16563 .option trusted_groups main "string list&!!" unset
16564 .cindex "trusted groups"
16565 .cindex "groups" "trusted"
16566 This option is expanded just once, at the start of Exim's processing. If this
16567 option is set, any process that is running in one of the listed groups, or
16568 which has one of them as a supplementary group, is trusted. The groups can be
16569 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
16570 details of what trusted callers are permitted to do. If neither
16571 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
16574 .option trusted_users main "string list&!!" unset
16575 .cindex "trusted users"
16576 .cindex "user" "trusted"
16577 This option is expanded just once, at the start of Exim's processing. If this
16578 option is set, any process that is running as one of the listed users is
16579 trusted. The users can be specified numerically or by name. See section
16580 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
16581 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
16582 Exim user are trusted.
16584 .option unknown_login main string&!! unset
16585 .cindex "uid (user id)" "unknown caller"
16586 .vindex "&$caller_uid$&"
16587 This is a specialized feature for use in unusual configurations. By default, if
16588 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
16589 gives up. The &%unknown_login%& option can be used to set a login name to be
16590 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
16591 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
16592 is used for the user's real name (gecos field), unless this has been set by the
16595 .option unknown_username main string unset
16596 See &%unknown_login%&.
16598 .option untrusted_set_sender main "address list&!!" unset
16599 .cindex "trusted users"
16600 .cindex "sender" "setting by untrusted user"
16601 .cindex "untrusted user setting sender"
16602 .cindex "user" "untrusted setting sender"
16603 .cindex "envelope sender"
16604 When an untrusted user submits a message to Exim using the standard input, Exim
16605 normally creates an envelope sender address from the user's login and the
16606 default qualification domain. Data from the &%-f%& option (for setting envelope
16607 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
16608 is used) is ignored.
16610 However, untrusted users are permitted to set an empty envelope sender address,
16611 to declare that a message should never generate any bounces. For example:
16613 exim -f '<>' user@domain.example
16615 .vindex "&$sender_ident$&"
16616 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
16617 other envelope sender addresses in a controlled way. When it is set, untrusted
16618 users are allowed to set envelope sender addresses that match any of the
16619 patterns in the list. Like all address lists, the string is expanded. The
16620 identity of the user is in &$sender_ident$&, so you can, for example, restrict
16621 users to setting senders that start with their login ids
16622 followed by a hyphen
16623 by a setting like this:
16625 untrusted_set_sender = ^$sender_ident-
16627 If you want to allow untrusted users to set envelope sender addresses without
16628 restriction, you can use
16630 untrusted_set_sender = *
16632 The &%untrusted_set_sender%& option applies to all forms of local input, but
16633 only to the setting of the envelope sender. It does not permit untrusted users
16634 to use the other options which trusted user can use to override message
16635 parameters. Furthermore, it does not stop Exim from removing an existing
16636 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
16637 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
16638 overriding these actions. The handling of the &'Sender:'& header is also
16639 described in section &<<SECTthesenhea>>&.
16641 The log line for a message's arrival shows the envelope sender following
16642 &"<="&. For local messages, the user's login always follows, after &"U="&. In
16643 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
16644 envelope sender address, the user's login is shown in parentheses after the
16648 .option uucp_from_pattern main string "see below"
16649 .cindex "&""From""& line"
16650 .cindex "UUCP" "&""From""& line"
16651 Some applications that pass messages to an MTA via a command line interface use
16652 an initial line starting with &"From&~"& to pass the envelope sender. In
16653 particular, this is used by UUCP software. Exim recognizes such a line by means
16654 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
16655 matches, the sender address is constructed by expanding the contents of
16656 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
16657 default pattern recognizes lines in the following two forms:
16659 From ph10 Fri Jan 5 12:35 GMT 1996
16660 From ph10 Fri, 7 Jan 97 14:00:00 GMT
16662 The pattern can be seen by running
16664 exim -bP uucp_from_pattern
16666 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
16667 year in the second case. The first word after &"From&~"& is matched in the
16668 regular expression by a parenthesized subpattern. The default value for
16669 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
16670 (&"ph10"& in the example above) as the message's sender. See also
16671 &%ignore_fromline_hosts%&.
16674 .option uucp_from_sender main string&!! &`$1`&
16675 See &%uucp_from_pattern%& above.
16678 .option warn_message_file main string unset
16679 .cindex "warning of delay" "customizing the message"
16680 .cindex "customizing" "warning message"
16681 This option defines a template file containing paragraphs of text to be used
16682 for constructing the warning message which is sent by Exim when a message has
16683 been on the queue for a specified amount of time, as specified by
16684 &%delay_warning%&. Details of the file's contents are given in chapter
16685 &<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
16688 .option write_rejectlog main boolean true
16689 .cindex "reject log" "disabling"
16690 If this option is set false, Exim no longer writes anything to the reject log.
16691 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
16692 .ecindex IIDconfima
16693 .ecindex IIDmaiconf
16698 . ////////////////////////////////////////////////////////////////////////////
16699 . ////////////////////////////////////////////////////////////////////////////
16701 .chapter "Generic options for routers" "CHAProutergeneric"
16702 .scindex IIDgenoprou1 "options" "generic; for routers"
16703 .scindex IIDgenoprou2 "generic options" "router"
16704 This chapter describes the generic options that apply to all routers.
16705 Those that are preconditions are marked with ‡ in the &"use"& field.
16707 For a general description of how a router operates, see sections
16708 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
16709 which the preconditions are tested. The order of expansion of the options that
16710 provide data for a transport is: &%errors_to%&, &%headers_add%&,
16711 &%headers_remove%&, &%transport%&.
16715 .option address_data routers string&!! unset
16716 .cindex "router" "data attached to address"
16717 The string is expanded just before the router is run, that is, after all the
16718 precondition tests have succeeded. If the expansion is forced to fail, the
16719 router declines, the value of &%address_data%& remains unchanged, and the
16720 &%more%& option controls what happens next. Other expansion failures cause
16721 delivery of the address to be deferred.
16723 .vindex "&$address_data$&"
16724 When the expansion succeeds, the value is retained with the address, and can be
16725 accessed using the variable &$address_data$& in the current router, subsequent
16726 routers, and the eventual transport.
16728 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
16729 that runs a user's filter file, the contents of &$address_data$& are accessible
16730 in the filter. This is not normally a problem, because such data is usually
16731 either not confidential or it &"belongs"& to the current user, but if you do
16732 put confidential data into &$address_data$& you need to remember this point.
16734 Even if the router declines or passes, the value of &$address_data$& remains
16735 with the address, though it can be changed by another &%address_data%& setting
16736 on a subsequent router. If a router generates child addresses, the value of
16737 &$address_data$& propagates to them. This also applies to the special kind of
16738 &"child"& that is generated by a router with the &%unseen%& option.
16740 The idea of &%address_data%& is that you can use it to look up a lot of data
16741 for the address once, and then pick out parts of the data later. For example,
16742 you could use a single LDAP lookup to return a string of the form
16744 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
16746 In the transport you could pick out the mailbox by a setting such as
16748 file = ${extract{mailbox}{$address_data}}
16750 This makes the configuration file less messy, and also reduces the number of
16751 lookups (though Exim does cache lookups).
16753 .vindex "&$sender_address_data$&"
16754 .vindex "&$address_data$&"
16755 The &%address_data%& facility is also useful as a means of passing information
16756 from one router to another, and from a router to a transport. In addition, if
16757 &$address_data$& is set by a router when verifying a recipient address from an
16758 ACL, it remains available for use in the rest of the ACL statement. After
16759 verifying a sender, the value is transferred to &$sender_address_data$&.
16763 .option address_test routers&!? boolean true
16765 .cindex "router" "skipping when address testing"
16766 If this option is set false, the router is skipped when routing is being tested
16767 by means of the &%-bt%& command line option. This can be a convenience when
16768 your first router sends messages to an external scanner, because it saves you
16769 having to set the &"already scanned"& indicator when testing real address
16774 .option cannot_route_message routers string&!! unset
16775 .cindex "router" "customizing &""cannot route""& message"
16776 .cindex "customizing" "&""cannot route""& message"
16777 This option specifies a text message that is used when an address cannot be
16778 routed because Exim has run out of routers. The default message is
16779 &"Unrouteable address"&. This option is useful only on routers that have
16780 &%more%& set false, or on the very last router in a configuration, because the
16781 value that is used is taken from the last router that is considered. This
16782 includes a router that is skipped because its preconditions are not met, as
16783 well as a router that declines. For example, using the default configuration,
16786 cannot_route_message = Remote domain not found in DNS
16788 on the first router, which is a &(dnslookup)& router with &%more%& set false,
16791 cannot_route_message = Unknown local user
16793 on the final router that checks for local users. If string expansion fails for
16794 this option, the default message is used. Unless the expansion failure was
16795 explicitly forced, a message about the failure is written to the main and panic
16796 logs, in addition to the normal message about the routing failure.
16799 .option caseful_local_part routers boolean false
16800 .cindex "case of local parts"
16801 .cindex "router" "case of local parts"
16802 By default, routers handle the local parts of addresses in a case-insensitive
16803 manner, though the actual case is preserved for transmission with the message.
16804 If you want the case of letters to be significant in a router, you must set
16805 this option true. For individual router options that contain address or local
16806 part lists (for example, &%local_parts%&), case-sensitive matching can be
16807 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
16810 .vindex "&$local_part$&"
16811 .vindex "&$original_local_part$&"
16812 .vindex "&$parent_local_part$&"
16813 The value of the &$local_part$& variable is forced to lower case while a
16814 router is running unless &%caseful_local_part%& is set. When a router assigns
16815 an address to a transport, the value of &$local_part$& when the transport runs
16816 is the same as it was in the router. Similarly, when a router generates child
16817 addresses by aliasing or forwarding, the values of &$original_local_part$&
16818 and &$parent_local_part$& are those that were used by the redirecting router.
16820 This option applies to the processing of an address by a router. When a
16821 recipient address is being processed in an ACL, there is a separate &%control%&
16822 modifier that can be used to specify case-sensitive processing within the ACL
16823 (see section &<<SECTcontrols>>&).
16827 .option check_local_user routers&!? boolean false
16828 .cindex "local user, checking in router"
16829 .cindex "router" "checking for local user"
16830 .cindex "&_/etc/passwd_&"
16832 When this option is true, Exim checks that the local part of the recipient
16833 address (with affixes removed if relevant) is the name of an account on the
16834 local system. The check is done by calling the &[getpwnam()]& function rather
16835 than trying to read &_/etc/passwd_& directly. This means that other methods of
16836 holding password data (such as NIS) are supported. If the local part is a local
16837 user, &$home$& is set from the password data, and can be tested in other
16838 preconditions that are evaluated after this one (the order of evaluation is
16839 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
16840 overridden by &%router_home_directory%&. If the local part is not a local user,
16841 the router is skipped.
16843 If you want to check that the local part is either the name of a local user
16844 or matches something else, you cannot combine &%check_local_user%& with a
16845 setting of &%local_parts%&, because that specifies the logical &'and'& of the
16846 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
16847 setting to achieve this. For example:
16849 local_parts = passwd;$local_part : lsearch;/etc/other/users
16851 Note, however, that the side effects of &%check_local_user%& (such as setting
16852 up a home directory) do not occur when a &(passwd)& lookup is used in a
16853 &%local_parts%& (or any other) precondition.
16857 .option condition routers&!? string&!! unset
16858 .cindex "router" "customized precondition"
16859 This option specifies a general precondition test that has to succeed for the
16860 router to be called. The &%condition%& option is the last precondition to be
16861 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
16862 result is a forced failure, or an empty string, or one of the strings &"0"& or
16863 &"no"& or &"false"& (checked without regard to the case of the letters), the
16864 router is skipped, and the address is offered to the next one.
16866 If the result is any other value, the router is run (as this is the last
16867 precondition to be evaluated, all the other preconditions must be true).
16869 This option is unusual in that multiple &%condition%& options may be present.
16870 All &%condition%& options must succeed.
16872 The &%condition%& option provides a means of applying custom conditions to the
16873 running of routers. Note that in the case of a simple conditional expansion,
16874 the default expansion values are exactly what is wanted. For example:
16876 condition = ${if >{$message_age}{600}}
16878 Because of the default behaviour of the string expansion, this is equivalent to
16880 condition = ${if >{$message_age}{600}{true}{}}
16883 A multiple condition example, which succeeds:
16885 condition = ${if >{$message_age}{600}}
16886 condition = ${if !eq{${lc:$local_part}}{postmaster}}
16890 If the expansion fails (other than forced failure) delivery is deferred. Some
16891 of the other precondition options are common special cases that could in fact
16892 be specified using &%condition%&.
16895 Historical note: We have &%condition%& on ACLs and on Routers. Routers
16896 are far older, and use one set of semantics. ACLs are newer and when
16897 they were created, the ACL &%condition%& process was given far stricter
16898 parse semantics. The &%bool{}%& expansion condition uses the same rules as
16899 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
16900 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
16901 Router rules processing behavior.
16903 This is best illustrated in an example:
16905 # If used in an ACL condition will fail with a syntax error, but
16906 # in a router condition any extra characters are treated as a string
16908 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
16911 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
16914 In each example above, the &%if%& statement actually ends after
16915 &"{google.com}}"&. Since no true or false braces were defined, the
16916 default &%if%& behavior is to return a boolean true or a null answer
16917 (which evaluates to false). The rest of the line is then treated as a
16918 string. So the first example resulted in the boolean answer &"true"&
16919 with the string &" {yes} {no}}"& appended to it. The second example
16920 resulted in the null output (indicating false) with the string
16921 &" {yes} {no}}"& appended to it.
16923 In fact you can put excess forward braces in too. In the router
16924 &%condition%&, Exim's parser only looks for &"{"& symbols when they
16925 mean something, like after a &"$"& or when required as part of a
16926 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
16929 Thus, in a Router, the above expansion strings will both always evaluate
16930 true, as the result of expansion is a non-empty string which doesn't
16931 match an explicit false value. This can be tricky to debug. By
16932 contrast, in an ACL either of those strings will always result in an
16933 expansion error because the result doesn't look sufficiently boolean.
16937 .option debug_print routers string&!! unset
16938 .cindex "testing" "variables in drivers"
16939 If this option is set and debugging is enabled (see the &%-d%& command line
16940 option) or in address-testing mode (see the &%-bt%& command line option),
16941 the string is expanded and included in the debugging output.
16942 If expansion of the string fails, the error message is written to the debugging
16943 output, and Exim carries on processing.
16944 This option is provided to help with checking out the values of variables and
16945 so on when debugging router configurations. For example, if a &%condition%&
16946 option appears not to be working, &%debug_print%& can be used to output the
16947 variables it references. The output happens after checks for &%domains%&,
16948 &%local_parts%&, and &%check_local_user%& but before any other preconditions
16949 are tested. A newline is added to the text if it does not end with one.
16950 The variable &$router_name$& contains the name of the router.
16954 .option disable_logging routers boolean false
16955 If this option is set true, nothing is logged for any routing errors
16956 or for any deliveries caused by this router. You should not set this option
16957 unless you really, really know what you are doing. See also the generic
16958 transport option of the same name.
16961 .option domains routers&!? "domain list&!!" unset
16962 .cindex "router" "restricting to specific domains"
16963 .vindex "&$domain_data$&"
16964 If this option is set, the router is skipped unless the current domain matches
16965 the list. If the match is achieved by means of a file lookup, the data that the
16966 lookup returned for the domain is placed in &$domain_data$& for use in string
16967 expansions of the driver's private options. See section &<<SECTrouprecon>>& for
16968 a list of the order in which preconditions are evaluated.
16972 .option driver routers string unset
16973 This option must always be set. It specifies which of the available routers is
16978 .option errors_to routers string&!! unset
16979 .cindex "envelope sender"
16980 .cindex "router" "changing address for errors"
16981 If a router successfully handles an address, it may assign the address to a
16982 transport for delivery or it may generate child addresses. In both cases, if
16983 there is a delivery problem during later processing, the resulting bounce
16984 message is sent to the address that results from expanding this string,
16985 provided that the address verifies successfully. The &%errors_to%& option is
16986 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
16988 The &%errors_to%& setting associated with an address can be overridden if it
16989 subsequently passes through other routers that have their own &%errors_to%&
16990 settings, or if the message is delivered by a transport with a &%return_path%&
16993 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
16994 the expansion fails to verify, the errors address associated with the incoming
16995 address is used. At top level, this is the envelope sender. A non-forced
16996 expansion failure causes delivery to be deferred.
16998 If an address for which &%errors_to%& has been set ends up being delivered over
16999 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
17000 any bounces that are generated by other MTAs on the delivery route are also
17001 sent there. You can set &%errors_to%& to the empty string by either of these
17007 An expansion item that yields an empty string has the same effect. If you do
17008 this, a locally detected delivery error for addresses processed by this router
17009 no longer gives rise to a bounce message; the error is discarded. If the
17010 address is delivered to a remote host, the return path is set to &`<>`&, unless
17011 overridden by the &%return_path%& option on the transport.
17013 .vindex "&$address_data$&"
17014 If for some reason you want to discard local errors, but use a non-empty
17015 MAIL command for remote delivery, you can preserve the original return
17016 path in &$address_data$& in the router, and reinstate it in the transport by
17017 setting &%return_path%&.
17019 The most common use of &%errors_to%& is to direct mailing list bounces to the
17020 manager of the list, as described in section &<<SECTmailinglists>>&, or to
17021 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
17025 .option expn routers&!? boolean true
17026 .cindex "address" "testing"
17027 .cindex "testing" "addresses"
17028 .cindex "EXPN" "router skipping"
17029 .cindex "router" "skipping for EXPN"
17030 If this option is turned off, the router is skipped when testing an address
17031 as a result of processing an SMTP EXPN command. You might, for example,
17032 want to turn it off on a router for users' &_.forward_& files, while leaving it
17033 on for the system alias file.
17034 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17037 The use of the SMTP EXPN command is controlled by an ACL (see chapter
17038 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
17039 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
17043 .option fail_verify routers boolean false
17044 .cindex "router" "forcing verification failure"
17045 Setting this option has the effect of setting both &%fail_verify_sender%& and
17046 &%fail_verify_recipient%& to the same value.
17050 .option fail_verify_recipient routers boolean false
17051 If this option is true and an address is accepted by this router when
17052 verifying a recipient, verification fails.
17056 .option fail_verify_sender routers boolean false
17057 If this option is true and an address is accepted by this router when
17058 verifying a sender, verification fails.
17062 .option fallback_hosts routers "string list" unset
17063 .cindex "router" "fallback hosts"
17064 .cindex "fallback" "hosts specified on router"
17065 String expansion is not applied to this option. The argument must be a
17066 colon-separated list of host names or IP addresses. The list separator can be
17067 changed (see section &<<SECTlistconstruct>>&), and a port can be specified with
17068 each name or address. In fact, the format of each item is exactly the same as
17069 defined for the list of hosts in a &(manualroute)& router (see section
17070 &<<SECTformatonehostitem>>&).
17072 If a router queues an address for a remote transport, this host list is
17073 associated with the address, and used instead of the transport's fallback host
17074 list. If &%hosts_randomize%& is set on the transport, the order of the list is
17075 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
17076 transport for further details.
17079 .option group routers string&!! "see below"
17080 .cindex "gid (group id)" "local delivery"
17081 .cindex "local transports" "uid and gid"
17082 .cindex "transport" "local"
17083 .cindex "router" "setting group"
17084 When a router queues an address for a transport, and the transport does not
17085 specify a group, the group given here is used when running the delivery
17087 The group may be specified numerically or by name. If expansion fails, the
17088 error is logged and delivery is deferred.
17089 The default is unset, unless &%check_local_user%& is set, when the default
17090 is taken from the password information. See also &%initgroups%& and &%user%&
17091 and the discussion in chapter &<<CHAPenvironment>>&.
17095 .option headers_add routers list&!! unset
17096 .cindex "header lines" "adding"
17097 .cindex "router" "adding header lines"
17098 This option specifies a list of text headers, newline-separated,
17099 that is associated with any addresses that are accepted by the router.
17100 Each item is separately expanded, at routing time. However, this
17101 option has no effect when an address is just being verified. The way in which
17102 the text is used to add header lines at transport time is described in section
17103 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
17104 message is in the process of being transported. This means that references to
17105 header lines in string expansions in the transport's configuration do not
17106 &"see"& the added header lines.
17108 The &%headers_add%& option is expanded after &%errors_to%&, but before
17109 &%headers_remove%& and &%transport%&. If an item is empty, or if
17110 an item expansion is forced to fail, the item has no effect. Other expansion
17111 failures are treated as configuration errors.
17113 Unlike most options, &%headers_add%& can be specified multiple times
17114 for a router; all listed headers are added.
17116 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
17117 router that has the &%one_time%& option set.
17119 .cindex "duplicate addresses"
17120 .oindex "&%unseen%&"
17121 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
17122 additions are deleted when the address is passed on to subsequent routers.
17123 For a &%redirect%& router, if a generated address is the same as the incoming
17124 address, this can lead to duplicate addresses with different header
17125 modifications. Exim does not do duplicate deliveries (except, in certain
17126 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
17127 which of the duplicates is discarded, so this ambiguous situation should be
17128 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
17132 .option headers_remove routers list&!! unset
17133 .cindex "header lines" "removing"
17134 .cindex "router" "removing header lines"
17135 This option specifies a list of text headers, colon-separated,
17136 that is associated with any addresses that are accepted by the router.
17137 Each item is separately expanded, at routing time. However, this
17138 option has no effect when an address is just being verified. The way in which
17139 the text is used to remove header lines at transport time is described in
17140 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
17141 the message is in the process of being transported. This means that references
17142 to header lines in string expansions in the transport's configuration still
17143 &"see"& the original header lines.
17145 The &%headers_remove%& option is expanded after &%errors_to%& and
17146 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
17147 the item has no effect. Other expansion failures are treated as configuration
17150 Unlike most options, &%headers_remove%& can be specified multiple times
17151 for a router; all listed headers are removed.
17153 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
17154 router that has the &%one_time%& option set.
17156 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
17157 removal requests are deleted when the address is passed on to subsequent
17158 routers, and this can lead to problems with duplicates -- see the similar
17159 warning for &%headers_add%& above.
17162 .option ignore_target_hosts routers "host list&!!" unset
17163 .cindex "IP address" "discarding"
17164 .cindex "router" "discarding IP addresses"
17165 Although this option is a host list, it should normally contain IP address
17166 entries rather than names. If any host that is looked up by the router has an
17167 IP address that matches an item in this list, Exim behaves as if that IP
17168 address did not exist. This option allows you to cope with rogue DNS entries
17171 remote.domain.example. A 127.0.0.1
17175 ignore_target_hosts = 127.0.0.1
17177 on the relevant router. If all the hosts found by a &(dnslookup)& router are
17178 discarded in this way, the router declines. In a conventional configuration, an
17179 attempt to mail to such a domain would normally provoke the &"unrouteable
17180 domain"& error, and an attempt to verify an address in the domain would fail.
17181 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
17182 router declines if presented with one of the listed addresses.
17184 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
17185 means of the first or the second of the following settings, respectively:
17187 ignore_target_hosts = 0.0.0.0/0
17188 ignore_target_hosts = <; 0::0/0
17190 The pattern in the first line matches all IPv4 addresses, whereas the pattern
17191 in the second line matches all IPv6 addresses.
17193 This option may also be useful for ignoring link-local and site-local IPv6
17194 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
17195 is expanded before use as a list, it is possible to make it dependent on the
17196 domain that is being routed.
17198 .vindex "&$host_address$&"
17199 During its expansion, &$host_address$& is set to the IP address that is being
17202 .option initgroups routers boolean false
17203 .cindex "additional groups"
17204 .cindex "groups" "additional"
17205 .cindex "local transports" "uid and gid"
17206 .cindex "transport" "local"
17207 If the router queues an address for a transport, and this option is true, and
17208 the uid supplied by the router is not overridden by the transport, the
17209 &[initgroups()]& function is called when running the transport to ensure that
17210 any additional groups associated with the uid are set up. See also &%group%&
17211 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
17215 .option local_part_prefix routers&!? "string list" unset
17216 .cindex "router" "prefix for local part"
17217 .cindex "prefix" "for local part, used in router"
17218 If this option is set, the router is skipped unless the local part starts with
17219 one of the given strings, or &%local_part_prefix_optional%& is true. See
17220 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
17223 The list is scanned from left to right, and the first prefix that matches is
17224 used. A limited form of wildcard is available; if the prefix begins with an
17225 asterisk, it matches the longest possible sequence of arbitrary characters at
17226 the start of the local part. An asterisk should therefore always be followed by
17227 some character that does not occur in normal local parts.
17228 .cindex "multiple mailboxes"
17229 .cindex "mailbox" "multiple"
17230 Wildcarding can be used to set up multiple user mailboxes, as described in
17231 section &<<SECTmulbox>>&.
17233 .vindex "&$local_part$&"
17234 .vindex "&$local_part_prefix$&"
17235 During the testing of the &%local_parts%& option, and while the router is
17236 running, the prefix is removed from the local part, and is available in the
17237 expansion variable &$local_part_prefix$&. When a message is being delivered, if
17238 the router accepts the address, this remains true during subsequent delivery by
17239 a transport. In particular, the local part that is transmitted in the RCPT
17240 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
17241 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
17242 the relevant transport.
17244 When an address is being verified, &%local_part_prefix%& affects only the
17245 behaviour of the router. If the callout feature of verification is in use, this
17246 means that the full address, including the prefix, will be used during the
17249 The prefix facility is commonly used to handle local parts of the form
17250 &%owner-something%&. Another common use is to support local parts of the form
17251 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
17252 to tell a user their forwarding is broken &-- by placing a router like this one
17253 immediately before the router that handles &_.forward_& files:
17257 local_part_prefix = real-
17259 transport = local_delivery
17261 For security, it would probably be a good idea to restrict the use of this
17262 router to locally-generated messages, using a condition such as this:
17264 condition = ${if match {$sender_host_address}\
17265 {\N^(|127\.0\.0\.1)$\N}}
17268 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
17269 both conditions must be met if not optional. Care must be taken if wildcards
17270 are used in both a prefix and a suffix on the same router. Different
17271 separator characters must be used to avoid ambiguity.
17274 .option local_part_prefix_optional routers boolean false
17275 See &%local_part_prefix%& above.
17279 .option local_part_suffix routers&!? "string list" unset
17280 .cindex "router" "suffix for local part"
17281 .cindex "suffix for local part" "used in router"
17282 This option operates in the same way as &%local_part_prefix%&, except that the
17283 local part must end (rather than start) with the given string, the
17284 &%local_part_suffix_optional%& option determines whether the suffix is
17285 mandatory, and the wildcard * character, if present, must be the last
17286 character of the suffix. This option facility is commonly used to handle local
17287 parts of the form &%something-request%& and multiple user mailboxes of the form
17291 .option local_part_suffix_optional routers boolean false
17292 See &%local_part_suffix%& above.
17296 .option local_parts routers&!? "local part list&!!" unset
17297 .cindex "router" "restricting to specific local parts"
17298 .cindex "local part" "checking in router"
17299 The router is run only if the local part of the address matches the list.
17300 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17302 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
17303 string is expanded, it is possible to make it depend on the domain, for
17306 local_parts = dbm;/usr/local/specials/$domain
17308 .vindex "&$local_part_data$&"
17309 If the match is achieved by a lookup, the data that the lookup returned
17310 for the local part is placed in the variable &$local_part_data$& for use in
17311 expansions of the router's private options. You might use this option, for
17312 example, if you have a large number of local virtual domains, and you want to
17313 send all postmaster mail to the same place without having to set up an alias in
17314 each virtual domain:
17318 local_parts = postmaster
17319 data = postmaster@real.domain.example
17323 .option log_as_local routers boolean "see below"
17324 .cindex "log" "delivery line"
17325 .cindex "delivery" "log line format"
17326 Exim has two logging styles for delivery, the idea being to make local
17327 deliveries stand out more visibly from remote ones. In the &"local"& style, the
17328 recipient address is given just as the local part, without a domain. The use of
17329 this style is controlled by this option. It defaults to true for the &(accept)&
17330 router, and false for all the others. This option applies only when a
17331 router assigns an address to a transport. It has no effect on routers that
17332 redirect addresses.
17336 .option more routers boolean&!! true
17337 The result of string expansion for this option must be a valid boolean value,
17338 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
17339 result causes an error, and delivery is deferred. If the expansion is forced to
17340 fail, the default value for the option (true) is used. Other failures cause
17341 delivery to be deferred.
17343 If this option is set false, and the router declines to handle the address, no
17344 further routers are tried, routing fails, and the address is bounced.
17346 However, if the router explicitly passes an address to the following router by
17347 means of the setting
17351 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
17352 does not affect the behaviour if one of the precondition tests fails. In that
17353 case, the address is always passed to the next router.
17355 Note that &%address_data%& is not considered to be a precondition. If its
17356 expansion is forced to fail, the router declines, and the value of &%more%&
17357 controls what happens next.
17360 .option pass_on_timeout routers boolean false
17361 .cindex "timeout" "of router"
17362 .cindex "router" "timeout"
17363 If a router times out during a host lookup, it normally causes deferral of the
17364 address. If &%pass_on_timeout%& is set, the address is passed on to the next
17365 router, overriding &%no_more%&. This may be helpful for systems that are
17366 intermittently connected to the Internet, or those that want to pass to a smart
17367 host any messages that cannot immediately be delivered.
17369 There are occasional other temporary errors that can occur while doing DNS
17370 lookups. They are treated in the same way as a timeout, and this option
17371 applies to all of them.
17375 .option pass_router routers string unset
17376 .cindex "router" "go to after &""pass""&"
17377 Routers that recognize the generic &%self%& option (&(dnslookup)&,
17378 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
17379 routing to continue, and overriding a false setting of &%more%&. When one of
17380 these routers returns &"pass"&, the address is normally handed on to the next
17381 router in sequence. This can be changed by setting &%pass_router%& to the name
17382 of another router. However (unlike &%redirect_router%&) the named router must
17383 be below the current router, to avoid loops. Note that this option applies only
17384 to the special case of &"pass"&. It does not apply when a router returns
17385 &"decline"& because it cannot handle an address.
17389 .option redirect_router routers string unset
17390 .cindex "router" "start at after redirection"
17391 Sometimes an administrator knows that it is pointless to reprocess addresses
17392 generated from alias or forward files with the same router again. For
17393 example, if an alias file translates real names into login ids there is no
17394 point searching the alias file a second time, especially if it is a large file.
17396 The &%redirect_router%& option can be set to the name of any router instance.
17397 It causes the routing of any generated addresses to start at the named router
17398 instead of at the first router. This option has no effect if the router in
17399 which it is set does not generate new addresses.
17403 .option require_files routers&!? "string list&!!" unset
17404 .cindex "file" "requiring for router"
17405 .cindex "router" "requiring file existence"
17406 This option provides a general mechanism for predicating the running of a
17407 router on the existence or non-existence of certain files or directories.
17408 Before running a router, as one of its precondition tests, Exim works its way
17409 through the &%require_files%& list, expanding each item separately.
17411 Because the list is split before expansion, any colons in expansion items must
17412 be doubled, or the facility for using a different list separator must be used.
17413 If any expansion is forced to fail, the item is ignored. Other expansion
17414 failures cause routing of the address to be deferred.
17416 If any expanded string is empty, it is ignored. Otherwise, except as described
17417 below, each string must be a fully qualified file path, optionally preceded by
17418 &"!"&. The paths are passed to the &[stat()]& function to test for the
17419 existence of the files or directories. The router is skipped if any paths not
17420 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
17423 If &[stat()]& cannot determine whether a file exists or not, delivery of
17424 the message is deferred. This can happen when NFS-mounted filesystems are
17427 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
17428 options, so you cannot use it to check for the existence of a file in which to
17429 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
17430 full list of the order in which preconditions are evaluated.) However, as
17431 these options are all expanded, you can use the &%exists%& expansion condition
17432 to make such tests. The &%require_files%& option is intended for checking files
17433 that the router may be going to use internally, or which are needed by a
17434 transport (for example &_.procmailrc_&).
17436 During delivery, the &[stat()]& function is run as root, but there is a
17437 facility for some checking of the accessibility of a file by another user.
17438 This is not a proper permissions check, but just a &"rough"& check that
17439 operates as follows:
17441 If an item in a &%require_files%& list does not contain any forward slash
17442 characters, it is taken to be the user (and optional group, separated by a
17443 comma) to be checked for subsequent files in the list. If no group is specified
17444 but the user is specified symbolically, the gid associated with the uid is
17447 require_files = mail:/some/file
17448 require_files = $local_part:$home/.procmailrc
17450 If a user or group name in a &%require_files%& list does not exist, the
17451 &%require_files%& condition fails.
17453 Exim performs the check by scanning along the components of the file path, and
17454 checking the access for the given uid and gid. It checks for &"x"& access on
17455 directories, and &"r"& access on the final file. Note that this means that file
17456 access control lists, if the operating system has them, are ignored.
17458 &*Warning 1*&: When the router is being run to verify addresses for an
17459 incoming SMTP message, Exim is not running as root, but under its own uid. This
17460 may affect the result of a &%require_files%& check. In particular, &[stat()]&
17461 may yield the error EACCES (&"Permission denied"&). This means that the Exim
17462 user is not permitted to read one of the directories on the file's path.
17464 &*Warning 2*&: Even when Exim is running as root while delivering a message,
17465 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
17466 without root access. In this case, if a check for access by a particular user
17467 is requested, Exim creates a subprocess that runs as that user, and tries the
17468 check again in that process.
17470 The default action for handling an unresolved EACCES is to consider it to
17471 be caused by a configuration error, and routing is deferred because the
17472 existence or non-existence of the file cannot be determined. However, in some
17473 circumstances it may be desirable to treat this condition as if the file did
17474 not exist. If the file name (or the exclamation mark that precedes the file
17475 name for non-existence) is preceded by a plus sign, the EACCES error is treated
17476 as if the file did not exist. For example:
17478 require_files = +/some/file
17480 If the router is not an essential part of verification (for example, it
17481 handles users' &_.forward_& files), another solution is to set the &%verify%&
17482 option false so that the router is skipped when verifying.
17486 .option retry_use_local_part routers boolean "see below"
17487 .cindex "hints database" "retry keys"
17488 .cindex "local part" "in retry keys"
17489 When a delivery suffers a temporary routing failure, a retry record is created
17490 in Exim's hints database. For addresses whose routing depends only on the
17491 domain, the key for the retry record should not involve the local part, but for
17492 other addresses, both the domain and the local part should be included.
17493 Usually, remote routing is of the former kind, and local routing is of the
17496 This option controls whether the local part is used to form the key for retry
17497 hints for addresses that suffer temporary errors while being handled by this
17498 router. The default value is true for any router that has &%check_local_user%&
17499 set, and false otherwise. Note that this option does not apply to hints keys
17500 for transport delays; they are controlled by a generic transport option of the
17503 The setting of &%retry_use_local_part%& applies only to the router on which it
17504 appears. If the router generates child addresses, they are routed
17505 independently; this setting does not become attached to them.
17509 .option router_home_directory routers string&!! unset
17510 .cindex "router" "home directory for"
17511 .cindex "home directory" "for router"
17513 This option sets a home directory for use while the router is running. (Compare
17514 &%transport_home_directory%&, which sets a home directory for later
17515 transporting.) In particular, if used on a &(redirect)& router, this option
17516 sets a value for &$home$& while a filter is running. The value is expanded;
17517 forced expansion failure causes the option to be ignored &-- other failures
17518 cause the router to defer.
17520 Expansion of &%router_home_directory%& happens immediately after the
17521 &%check_local_user%& test (if configured), before any further expansions take
17523 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17525 While the router is running, &%router_home_directory%& overrides the value of
17526 &$home$& that came from &%check_local_user%&.
17528 When a router accepts an address and assigns it to a local transport (including
17529 the cases when a &(redirect)& router generates a pipe, file, or autoreply
17530 delivery), the home directory setting for the transport is taken from the first
17531 of these values that is set:
17534 The &%home_directory%& option on the transport;
17536 The &%transport_home_directory%& option on the router;
17538 The password data if &%check_local_user%& is set on the router;
17540 The &%router_home_directory%& option on the router.
17543 In other words, &%router_home_directory%& overrides the password data for the
17544 router, but not for the transport.
17548 .option self routers string freeze
17549 .cindex "MX record" "pointing to local host"
17550 .cindex "local host" "MX pointing to"
17551 This option applies to those routers that use a recipient address to find a
17552 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
17553 and &(manualroute)& routers.
17554 Certain configurations of the &(queryprogram)& router can also specify a list
17556 Usually such routers are configured to send the message to a remote host via an
17557 &(smtp)& transport. The &%self%& option specifies what happens when the first
17558 host on the list turns out to be the local host.
17559 The way in which Exim checks for the local host is described in section
17560 &<<SECTreclocipadd>>&.
17562 Normally this situation indicates either an error in Exim's configuration (for
17563 example, the router should be configured not to process this domain), or an
17564 error in the DNS (for example, the MX should not point to this host). For this
17565 reason, the default action is to log the incident, defer the address, and
17566 freeze the message. The following alternatives are provided for use in special
17571 Delivery of the message is tried again later, but the message is not frozen.
17573 .vitem "&%reroute%&: <&'domain'&>"
17574 The domain is changed to the given domain, and the address is passed back to
17575 be reprocessed by the routers. No rewriting of headers takes place. This
17576 behaviour is essentially a redirection.
17578 .vitem "&%reroute: rewrite:%& <&'domain'&>"
17579 The domain is changed to the given domain, and the address is passed back to be
17580 reprocessed by the routers. Any headers that contain the original domain are
17585 .vindex "&$self_hostname$&"
17586 The router passes the address to the next router, or to the router named in the
17587 &%pass_router%& option if it is set. This overrides &%no_more%&. During
17588 subsequent routing and delivery, the variable &$self_hostname$& contains the
17589 name of the local host that the router encountered. This can be used to
17590 distinguish between different cases for hosts with multiple names. The
17596 ensures that only those addresses that routed to the local host are passed on.
17597 Without &%no_more%&, addresses that were declined for other reasons would also
17598 be passed to the next router.
17601 Delivery fails and an error report is generated.
17604 .cindex "local host" "sending to"
17605 The anomaly is ignored and the address is queued for the transport. This
17606 setting should be used with extreme caution. For an &(smtp)& transport, it
17607 makes sense only in cases where the program that is listening on the SMTP port
17608 is not this version of Exim. That is, it must be some other MTA, or Exim with a
17609 different configuration file that handles the domain in another way.
17614 .option senders routers&!? "address list&!!" unset
17615 .cindex "router" "checking senders"
17616 If this option is set, the router is skipped unless the message's sender
17617 address matches something on the list.
17618 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17621 There are issues concerning verification when the running of routers is
17622 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
17623 setting, it sets the sender to the null string. When using the &%-bt%& option
17624 to check a configuration file, it is necessary also to use the &%-f%& option to
17625 set an appropriate sender. For incoming mail, the sender is unset when
17626 verifying the sender, but is available when verifying any recipients. If the
17627 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
17631 .option translate_ip_address routers string&!! unset
17632 .cindex "IP address" "translating"
17633 .cindex "packet radio"
17634 .cindex "router" "IP address translation"
17635 There exist some rare networking situations (for example, packet radio) where
17636 it is helpful to be able to translate IP addresses generated by normal routing
17637 mechanisms into other IP addresses, thus performing a kind of manual IP
17638 routing. This should be done only if the normal IP routing of the TCP/IP stack
17639 is inadequate or broken. Because this is an extremely uncommon requirement, the
17640 code to support this option is not included in the Exim binary unless
17641 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
17643 .vindex "&$host_address$&"
17644 The &%translate_ip_address%& string is expanded for every IP address generated
17645 by the router, with the generated address set in &$host_address$&. If the
17646 expansion is forced to fail, no action is taken.
17647 For any other expansion error, delivery of the message is deferred.
17648 If the result of the expansion is an IP address, that replaces the original
17649 address; otherwise the result is assumed to be a host name &-- this is looked
17650 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
17651 produce one or more replacement IP addresses. For example, to subvert all IP
17652 addresses in some specific networks, this could be added to a router:
17654 translate_ip_address = \
17655 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
17658 The file would contain lines like
17660 10.2.3.128/26 some.host
17661 10.8.4.34/26 10.44.8.15
17663 You should not make use of this facility unless you really understand what you
17668 .option transport routers string&!! unset
17669 This option specifies the transport to be used when a router accepts an address
17670 and sets it up for delivery. A transport is never needed if a router is used
17671 only for verification. The value of the option is expanded at routing time,
17672 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
17673 and result must be the name of one of the configured transports. If it is not,
17674 delivery is deferred.
17676 The &%transport%& option is not used by the &(redirect)& router, but it does
17677 have some private options that set up transports for pipe and file deliveries
17678 (see chapter &<<CHAPredirect>>&).
17682 .option transport_current_directory routers string&!! unset
17683 .cindex "current directory for local transport"
17684 This option associates a current directory with any address that is routed
17685 to a local transport. This can happen either because a transport is
17686 explicitly configured for the router, or because it generates a delivery to a
17687 file or a pipe. During the delivery process (that is, at transport time), this
17688 option string is expanded and is set as the current directory, unless
17689 overridden by a setting on the transport.
17690 If the expansion fails for any reason, including forced failure, an error is
17691 logged, and delivery is deferred.
17692 See chapter &<<CHAPenvironment>>& for details of the local delivery
17698 .option transport_home_directory routers string&!! "see below"
17699 .cindex "home directory" "for local transport"
17700 This option associates a home directory with any address that is routed to a
17701 local transport. This can happen either because a transport is explicitly
17702 configured for the router, or because it generates a delivery to a file or a
17703 pipe. During the delivery process (that is, at transport time), the option
17704 string is expanded and is set as the home directory, unless overridden by a
17705 setting of &%home_directory%& on the transport.
17706 If the expansion fails for any reason, including forced failure, an error is
17707 logged, and delivery is deferred.
17709 If the transport does not specify a home directory, and
17710 &%transport_home_directory%& is not set for the router, the home directory for
17711 the transport is taken from the password data if &%check_local_user%& is set for
17712 the router. Otherwise it is taken from &%router_home_directory%& if that option
17713 is set; if not, no home directory is set for the transport.
17715 See chapter &<<CHAPenvironment>>& for further details of the local delivery
17721 .option unseen routers boolean&!! false
17722 .cindex "router" "carrying on after success"
17723 The result of string expansion for this option must be a valid boolean value,
17724 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
17725 result causes an error, and delivery is deferred. If the expansion is forced to
17726 fail, the default value for the option (false) is used. Other failures cause
17727 delivery to be deferred.
17729 When this option is set true, routing does not cease if the router accepts the
17730 address. Instead, a copy of the incoming address is passed to the next router,
17731 overriding a false setting of &%more%&. There is little point in setting
17732 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
17733 the value of &%unseen%& contains expansion items (and therefore, presumably, is
17734 sometimes true and sometimes false).
17736 .cindex "copy of message (&%unseen%& option)"
17737 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
17738 qualifier in filter files. It can be used to cause copies of messages to be
17739 delivered to some other destination, while also carrying out a normal delivery.
17740 In effect, the current address is made into a &"parent"& that has two children
17741 &-- one that is delivered as specified by this router, and a clone that goes on
17742 to be routed further. For this reason, &%unseen%& may not be combined with the
17743 &%one_time%& option in a &(redirect)& router.
17745 &*Warning*&: Header lines added to the address (or specified for removal) by
17746 this router or by previous routers affect the &"unseen"& copy of the message
17747 only. The clone that continues to be processed by further routers starts with
17748 no added headers and none specified for removal. For a &%redirect%& router, if
17749 a generated address is the same as the incoming address, this can lead to
17750 duplicate addresses with different header modifications. Exim does not do
17751 duplicate deliveries (except, in certain circumstances, to pipes -- see section
17752 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
17753 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
17754 &%redirect%& router may be of help.
17756 Unlike the handling of header modifications, any data that was set by the
17757 &%address_data%& option in the current or previous routers &'is'& passed on to
17758 subsequent routers.
17761 .option user routers string&!! "see below"
17762 .cindex "uid (user id)" "local delivery"
17763 .cindex "local transports" "uid and gid"
17764 .cindex "transport" "local"
17765 .cindex "router" "user for filter processing"
17766 .cindex "filter" "user for processing"
17767 When a router queues an address for a transport, and the transport does not
17768 specify a user, the user given here is used when running the delivery process.
17769 The user may be specified numerically or by name. If expansion fails, the
17770 error is logged and delivery is deferred.
17771 This user is also used by the &(redirect)& router when running a filter file.
17772 The default is unset, except when &%check_local_user%& is set. In this case,
17773 the default is taken from the password information. If the user is specified as
17774 a name, and &%group%& is not set, the group associated with the user is used.
17775 See also &%initgroups%& and &%group%& and the discussion in chapter
17776 &<<CHAPenvironment>>&.
17780 .option verify routers&!? boolean true
17781 Setting this option has the effect of setting &%verify_sender%& and
17782 &%verify_recipient%& to the same value.
17785 .option verify_only routers&!? boolean false
17786 .cindex "EXPN" "with &%verify_only%&"
17788 .cindex "router" "used only when verifying"
17789 If this option is set, the router is used only when verifying an address,
17790 delivering in cutthrough mode or
17791 testing with the &%-bv%& option, not when actually doing a delivery, testing
17792 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
17793 restricted to verifying only senders or recipients by means of
17794 &%verify_sender%& and &%verify_recipient%&.
17796 &*Warning*&: When the router is being run to verify addresses for an incoming
17797 SMTP message, Exim is not running as root, but under its own uid. If the router
17798 accesses any files, you need to make sure that they are accessible to the Exim
17802 .option verify_recipient routers&!? boolean true
17803 If this option is false, the router is skipped when verifying recipient
17805 delivering in cutthrough mode
17806 or testing recipient verification using &%-bv%&.
17807 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17809 See also the &$verify_mode$& variable.
17812 .option verify_sender routers&!? boolean true
17813 If this option is false, the router is skipped when verifying sender addresses
17814 or testing sender verification using &%-bvs%&.
17815 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17817 See also the &$verify_mode$& variable.
17818 .ecindex IIDgenoprou1
17819 .ecindex IIDgenoprou2
17826 . ////////////////////////////////////////////////////////////////////////////
17827 . ////////////////////////////////////////////////////////////////////////////
17829 .chapter "The accept router" "CHID4"
17830 .cindex "&(accept)& router"
17831 .cindex "routers" "&(accept)&"
17832 The &(accept)& router has no private options of its own. Unless it is being
17833 used purely for verification (see &%verify_only%&) a transport is required to
17834 be defined by the generic &%transport%& option. If the preconditions that are
17835 specified by generic options are met, the router accepts the address and queues
17836 it for the given transport. The most common use of this router is for setting
17837 up deliveries to local mailboxes. For example:
17841 domains = mydomain.example
17843 transport = local_delivery
17845 The &%domains%& condition in this example checks the domain of the address, and
17846 &%check_local_user%& checks that the local part is the login of a local user.
17847 When both preconditions are met, the &(accept)& router runs, and queues the
17848 address for the &(local_delivery)& transport.
17855 . ////////////////////////////////////////////////////////////////////////////
17856 . ////////////////////////////////////////////////////////////////////////////
17858 .chapter "The dnslookup router" "CHAPdnslookup"
17859 .scindex IIDdnsrou1 "&(dnslookup)& router"
17860 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
17861 The &(dnslookup)& router looks up the hosts that handle mail for the
17862 recipient's domain in the DNS. A transport must always be set for this router,
17863 unless &%verify_only%& is set.
17865 If SRV support is configured (see &%check_srv%& below), Exim first searches for
17866 SRV records. If none are found, or if SRV support is not configured,
17867 MX records are looked up. If no MX records exist, address records are sought.
17868 However, &%mx_domains%& can be set to disable the direct use of address
17871 MX records of equal priority are sorted by Exim into a random order. Exim then
17872 looks for address records for the host names obtained from MX or SRV records.
17873 When a host has more than one IP address, they are sorted into a random order,
17874 except that IPv6 addresses are always sorted before IPv4 addresses. If all the
17875 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
17876 generic option, the router declines.
17878 Unless they have the highest priority (lowest MX value), MX records that point
17879 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
17880 are discarded, together with any other MX records of equal or lower priority.
17882 .cindex "MX record" "pointing to local host"
17883 .cindex "local host" "MX pointing to"
17884 .oindex "&%self%&" "in &(dnslookup)& router"
17885 If the host pointed to by the highest priority MX record, or looked up as an
17886 address record, is the local host, or matches &%hosts_treat_as_local%&, what
17887 happens is controlled by the generic &%self%& option.
17890 .section "Problems with DNS lookups" "SECTprowitdnsloo"
17891 There have been problems with DNS servers when SRV records are looked up.
17892 Some mis-behaving servers return a DNS error or timeout when a non-existent
17893 SRV record is sought. Similar problems have in the past been reported for
17894 MX records. The global &%dns_again_means_nonexist%& option can help with this
17895 problem, but it is heavy-handed because it is a global option.
17897 For this reason, there are two options, &%srv_fail_domains%& and
17898 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
17899 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
17900 an attempt to look up an SRV or MX record causes one of these results, and the
17901 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
17902 such record"&. In the case of an SRV lookup, this means that the router
17903 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
17904 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
17905 case routing fails.
17908 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
17909 .cindex "&(dnslookup)& router" "declines"
17910 There are a few cases where a &(dnslookup)& router will decline to accept
17911 an address; if such a router is expected to handle "all remaining non-local
17912 domains", then it is important to set &%no_more%&.
17914 Reasons for a &(dnslookup)& router to decline currently include:
17916 The domain does not exist in DNS
17918 The domain exists but the MX record's host part is just "."; this is a common
17919 convention (borrowed from SRV) used to indicate that there is no such service
17920 for this domain and to not fall back to trying A/AAAA records.
17922 Ditto, but for SRV records, when &%check_srv%& is set on this router.
17924 MX record points to a non-existent host.
17926 MX record points to an IP address and the main section option
17927 &%allow_mx_to_ip%& is not set.
17929 MX records exist and point to valid hosts, but all hosts resolve only to
17930 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
17932 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
17933 &%dns_check_names_pattern%& for handling one variant of this)
17935 &%check_secondary_mx%& is set on this router but the local host can
17936 not be found in the MX records (see below)
17942 .section "Private options for dnslookup" "SECID118"
17943 .cindex "options" "&(dnslookup)& router"
17944 The private options for the &(dnslookup)& router are as follows:
17946 .option check_secondary_mx dnslookup boolean false
17947 .cindex "MX record" "checking for secondary"
17948 If this option is set, the router declines unless the local host is found in
17949 (and removed from) the list of hosts obtained by MX lookup. This can be used to
17950 process domains for which the local host is a secondary mail exchanger
17951 differently to other domains. The way in which Exim decides whether a host is
17952 the local host is described in section &<<SECTreclocipadd>>&.
17955 .option check_srv dnslookup string&!! unset
17956 .cindex "SRV record" "enabling use of"
17957 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
17958 addition to MX and address records. The support is disabled by default. To
17959 enable SRV support, set the &%check_srv%& option to the name of the service
17960 required. For example,
17964 looks for SRV records that refer to the normal smtp service. The option is
17965 expanded, so the service name can vary from message to message or address
17966 to address. This might be helpful if SRV records are being used for a
17967 submission service. If the expansion is forced to fail, the &%check_srv%&
17968 option is ignored, and the router proceeds to look for MX records in the
17971 When the expansion succeeds, the router searches first for SRV records for
17972 the given service (it assumes TCP protocol). A single SRV record with a
17973 host name that consists of just a single dot indicates &"no such service for
17974 this domain"&; if this is encountered, the router declines. If other kinds of
17975 SRV record are found, they are used to construct a host list for delivery
17976 according to the rules of RFC 2782. MX records are not sought in this case.
17978 When no SRV records are found, MX records (and address records) are sought in
17979 the traditional way. In other words, SRV records take precedence over MX
17980 records, just as MX records take precedence over address records. Note that
17981 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
17982 defined it. It is apparently believed that MX records are sufficient for email
17983 and that SRV records should not be used for this purpose. However, SRV records
17984 have an additional &"weight"& feature which some people might find useful when
17985 trying to split an SMTP load between hosts of different power.
17987 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
17988 when there is a DNS lookup error.
17992 .option dnssec_request_domains dnslookup "domain list&!!" unset
17993 .cindex "MX record" "security"
17994 .cindex "DNSSEC" "MX lookup"
17995 .cindex "security" "MX lookup"
17996 .cindex "DNS" "DNSSEC"
17997 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
17998 the dnssec request bit set.
17999 This applies to all of the SRV, MX A6, AAAA, A lookup sequence.
18003 .option dnssec_require_domains dnslookup "domain list&!!" unset
18004 .cindex "MX record" "security"
18005 .cindex "DNSSEC" "MX lookup"
18006 .cindex "security" "MX lookup"
18007 .cindex "DNS" "DNSSEC"
18008 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
18009 the dnssec request bit set. Any returns not having the Authenticated Data bit
18010 (AD bit) set wil be ignored and logged as a host-lookup failure.
18011 This applies to all of the SRV, MX A6, AAAA, A lookup sequence.
18015 .option mx_domains dnslookup "domain list&!!" unset
18016 .cindex "MX record" "required to exist"
18017 .cindex "SRV record" "required to exist"
18018 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
18019 record in order to be recognized. (The name of this option could be improved.)
18020 For example, if all the mail hosts in &'fict.example'& are known to have MX
18021 records, except for those in &'discworld.fict.example'&, you could use this
18024 mx_domains = ! *.discworld.fict.example : *.fict.example
18026 This specifies that messages addressed to a domain that matches the list but
18027 has no MX record should be bounced immediately instead of being routed using
18028 the address record.
18031 .option mx_fail_domains dnslookup "domain list&!!" unset
18032 If the DNS lookup for MX records for one of the domains in this list causes a
18033 DNS lookup error, Exim behaves as if no MX records were found. See section
18034 &<<SECTprowitdnsloo>>& for more discussion.
18039 .option qualify_single dnslookup boolean true
18040 .cindex "DNS" "resolver options"
18041 .cindex "DNS" "qualifying single-component names"
18042 When this option is true, the resolver option RES_DEFNAMES is set for DNS
18043 lookups. Typically, but not standardly, this causes the resolver to qualify
18044 single-component names with the default domain. For example, on a machine
18045 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
18046 &'thesaurus.ref.example'& inside the resolver. For details of what your
18047 resolver actually does, consult your man pages for &'resolver'& and
18052 .option rewrite_headers dnslookup boolean true
18053 .cindex "rewriting" "header lines"
18054 .cindex "header lines" "rewriting"
18055 If the domain name in the address that is being processed is not fully
18056 qualified, it may be expanded to its full form by a DNS lookup. For example, if
18057 an address is specified as &'dormouse@teaparty'&, the domain might be
18058 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
18059 occur as a result of setting the &%widen_domains%& option. If
18060 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
18061 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
18062 header lines of the message are rewritten with the full domain name.
18064 This option should be turned off only when it is known that no message is
18065 ever going to be sent outside an environment where the abbreviation makes
18068 When an MX record is looked up in the DNS and matches a wildcard record, name
18069 servers normally return a record containing the name that has been looked up,
18070 making it impossible to detect whether a wildcard was present or not. However,
18071 some name servers have recently been seen to return the wildcard entry. If the
18072 name returned by a DNS lookup begins with an asterisk, it is not used for
18076 .option same_domain_copy_routing dnslookup boolean false
18077 .cindex "address" "copying routing"
18078 Addresses with the same domain are normally routed by the &(dnslookup)& router
18079 to the same list of hosts. However, this cannot be presumed, because the router
18080 options and preconditions may refer to the local part of the address. By
18081 default, therefore, Exim routes each address in a message independently. DNS
18082 servers run caches, so repeated DNS lookups are not normally expensive, and in
18083 any case, personal messages rarely have more than a few recipients.
18085 If you are running mailing lists with large numbers of subscribers at the same
18086 domain, and you are using a &(dnslookup)& router which is independent of the
18087 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
18088 lookups for identical domains in one message. In this case, when &(dnslookup)&
18089 routes an address to a remote transport, any other unrouted addresses in the
18090 message that have the same domain are automatically given the same routing
18091 without processing them independently,
18092 provided the following conditions are met:
18095 No router that processed the address specified &%headers_add%& or
18096 &%headers_remove%&.
18098 The router did not change the address in any way, for example, by &"widening"&
18105 .option search_parents dnslookup boolean false
18106 .cindex "DNS" "resolver options"
18107 When this option is true, the resolver option RES_DNSRCH is set for DNS
18108 lookups. This is different from the &%qualify_single%& option in that it
18109 applies to domains containing dots. Typically, but not standardly, it causes
18110 the resolver to search for the name in the current domain and in parent
18111 domains. For example, on a machine in the &'fict.example'& domain, if looking
18112 up &'teaparty.wonderland'& failed, the resolver would try
18113 &'teaparty.wonderland.fict.example'&. For details of what your resolver
18114 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
18116 Setting this option true can cause problems in domains that have a wildcard MX
18117 record, because any domain that does not have its own MX record matches the
18122 .option srv_fail_domains dnslookup "domain list&!!" unset
18123 If the DNS lookup for SRV records for one of the domains in this list causes a
18124 DNS lookup error, Exim behaves as if no SRV records were found. See section
18125 &<<SECTprowitdnsloo>>& for more discussion.
18130 .option widen_domains dnslookup "string list" unset
18131 .cindex "domain" "partial; widening"
18132 If a DNS lookup fails and this option is set, each of its strings in turn is
18133 added onto the end of the domain, and the lookup is tried again. For example,
18136 widen_domains = fict.example:ref.example
18138 is set and a lookup of &'klingon.dictionary'& fails,
18139 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
18140 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
18141 and &%search_parents%& options can cause some widening to be undertaken inside
18142 the DNS resolver. &%widen_domains%& is not applied to sender addresses
18143 when verifying, unless &%rewrite_headers%& is false (not the default).
18146 .section "Effect of qualify_single and search_parents" "SECID119"
18147 When a domain from an envelope recipient is changed by the resolver as a result
18148 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
18149 corresponding address in the message's header lines unless &%rewrite_headers%&
18150 is set false. Exim then re-routes the address, using the full domain.
18152 These two options affect only the DNS lookup that takes place inside the router
18153 for the domain of the address that is being routed. They do not affect lookups
18154 such as that implied by
18158 that may happen while processing a router precondition before the router is
18159 entered. No widening ever takes place for these lookups.
18160 .ecindex IIDdnsrou1
18161 .ecindex IIDdnsrou2
18171 . ////////////////////////////////////////////////////////////////////////////
18172 . ////////////////////////////////////////////////////////////////////////////
18174 .chapter "The ipliteral router" "CHID5"
18175 .cindex "&(ipliteral)& router"
18176 .cindex "domain literal" "routing"
18177 .cindex "routers" "&(ipliteral)&"
18178 This router has no private options. Unless it is being used purely for
18179 verification (see &%verify_only%&) a transport is required to be defined by the
18180 generic &%transport%& option. The router accepts the address if its domain part
18181 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
18182 router handles the address
18186 by setting up delivery to the host with that IP address. IPv4 domain literals
18187 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
18188 are similar, but the address is preceded by &`ipv6:`&. For example:
18190 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
18192 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
18193 grounds that sooner or later somebody will try it.
18195 .oindex "&%self%&" "in &(ipliteral)& router"
18196 If the IP address matches something in &%ignore_target_hosts%&, the router
18197 declines. If an IP literal turns out to refer to the local host, the generic
18198 &%self%& option determines what happens.
18200 The RFCs require support for domain literals; however, their use is
18201 controversial in today's Internet. If you want to use this router, you must
18202 also set the main configuration option &%allow_domain_literals%&. Otherwise,
18203 Exim will not recognize the domain literal syntax in addresses.
18207 . ////////////////////////////////////////////////////////////////////////////
18208 . ////////////////////////////////////////////////////////////////////////////
18210 .chapter "The iplookup router" "CHID6"
18211 .cindex "&(iplookup)& router"
18212 .cindex "routers" "&(iplookup)&"
18213 The &(iplookup)& router was written to fulfil a specific requirement in
18214 Cambridge University (which in fact no longer exists). For this reason, it is
18215 not included in the binary of Exim by default. If you want to include it, you
18218 ROUTER_IPLOOKUP=yes
18220 in your &_Local/Makefile_& configuration file.
18222 The &(iplookup)& router routes an address by sending it over a TCP or UDP
18223 connection to one or more specific hosts. The host can then return the same or
18224 a different address &-- in effect rewriting the recipient address in the
18225 message's envelope. The new address is then passed on to subsequent routers. If
18226 this process fails, the address can be passed on to other routers, or delivery
18227 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
18228 must not be specified for it.
18230 .cindex "options" "&(iplookup)& router"
18231 .option hosts iplookup string unset
18232 This option must be supplied. Its value is a colon-separated list of host
18233 names. The hosts are looked up using &[gethostbyname()]&
18234 (or &[getipnodebyname()]& when available)
18235 and are tried in order until one responds to the query. If none respond, what
18236 happens is controlled by &%optional%&.
18239 .option optional iplookup boolean false
18240 If &%optional%& is true, if no response is obtained from any host, the address
18241 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
18242 delivery to the address is deferred.
18245 .option port iplookup integer 0
18246 .cindex "port" "&(iplookup)& router"
18247 This option must be supplied. It specifies the port number for the TCP or UDP
18251 .option protocol iplookup string udp
18252 This option can be set to &"udp"& or &"tcp"& to specify which of the two
18253 protocols is to be used.
18256 .option query iplookup string&!! "see below"
18257 This defines the content of the query that is sent to the remote hosts. The
18260 $local_part@$domain $local_part@$domain
18262 The repetition serves as a way of checking that a response is to the correct
18263 query in the default case (see &%response_pattern%& below).
18266 .option reroute iplookup string&!! unset
18267 If this option is not set, the rerouted address is precisely the byte string
18268 returned by the remote host, up to the first white space, if any. If set, the
18269 string is expanded to form the rerouted address. It can include parts matched
18270 in the response by &%response_pattern%& by means of numeric variables such as
18271 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
18272 whether or not a pattern is in use. In all cases, the rerouted address must end
18273 up in the form &'local_part@domain'&.
18276 .option response_pattern iplookup string unset
18277 This option can be set to a regular expression that is applied to the string
18278 returned from the remote host. If the pattern does not match the response, the
18279 router declines. If &%response_pattern%& is not set, no checking of the
18280 response is done, unless the query was defaulted, in which case there is a
18281 check that the text returned after the first white space is the original
18282 address. This checks that the answer that has been received is in response to
18283 the correct question. For example, if the response is just a new domain, the
18284 following could be used:
18286 response_pattern = ^([^@]+)$
18287 reroute = $local_part@$1
18290 .option timeout iplookup time 5s
18291 This specifies the amount of time to wait for a response from the remote
18292 machine. The same timeout is used for the &[connect()]& function for a TCP
18293 call. It does not apply to UDP.
18298 . ////////////////////////////////////////////////////////////////////////////
18299 . ////////////////////////////////////////////////////////////////////////////
18301 .chapter "The manualroute router" "CHID7"
18302 .scindex IIDmanrou1 "&(manualroute)& router"
18303 .scindex IIDmanrou2 "routers" "&(manualroute)&"
18304 .cindex "domain" "manually routing"
18305 The &(manualroute)& router is so-called because it provides a way of manually
18306 routing an address according to its domain. It is mainly used when you want to
18307 route addresses to remote hosts according to your own rules, bypassing the
18308 normal DNS routing that looks up MX records. However, &(manualroute)& can also
18309 route to local transports, a facility that may be useful if you want to save
18310 messages for dial-in hosts in local files.
18312 The &(manualroute)& router compares a list of domain patterns with the domain
18313 it is trying to route. If there is no match, the router declines. Each pattern
18314 has associated with it a list of hosts and some other optional data, which may
18315 include a transport. The combination of a pattern and its data is called a
18316 &"routing rule"&. For patterns that do not have an associated transport, the
18317 generic &%transport%& option must specify a transport, unless the router is
18318 being used purely for verification (see &%verify_only%&).
18321 In the case of verification, matching the domain pattern is sufficient for the
18322 router to accept the address. When actually routing an address for delivery,
18323 an address that matches a domain pattern is queued for the associated
18324 transport. If the transport is not a local one, a host list must be associated
18325 with the pattern; IP addresses are looked up for the hosts, and these are
18326 passed to the transport along with the mail address. For local transports, a
18327 host list is optional. If it is present, it is passed in &$host$& as a single
18330 The list of routing rules can be provided as an inline string in
18331 &%route_list%&, or the data can be obtained by looking up the domain in a file
18332 or database by setting &%route_data%&. Only one of these settings may appear in
18333 any one instance of &(manualroute)&. The format of routing rules is described
18334 below, following the list of private options.
18337 .section "Private options for manualroute" "SECTprioptman"
18339 .cindex "options" "&(manualroute)& router"
18340 The private options for the &(manualroute)& router are as follows:
18342 .option host_all_ignored manualroute string defer
18343 See &%host_find_failed%&.
18345 .option host_find_failed manualroute string freeze
18346 This option controls what happens when &(manualroute)& tries to find an IP
18347 address for a host, and the host does not exist. The option can be set to one
18348 of the following values:
18357 The default (&"freeze"&) assumes that this state is a serious configuration
18358 error. The difference between &"pass"& and &"decline"& is that the former
18359 forces the address to be passed to the next router (or the router defined by
18362 overriding &%no_more%&, whereas the latter passes the address to the next
18363 router only if &%more%& is true.
18365 The value &"ignore"& causes Exim to completely ignore a host whose IP address
18366 cannot be found. If all the hosts in the list are ignored, the behaviour is
18367 controlled by the &%host_all_ignored%& option. This takes the same values
18368 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
18370 The &%host_find_failed%& option applies only to a definite &"does not exist"&
18371 state; if a host lookup gets a temporary error, delivery is deferred unless the
18372 generic &%pass_on_timeout%& option is set.
18375 .option hosts_randomize manualroute boolean false
18376 .cindex "randomized host list"
18377 .cindex "host" "list of; randomized"
18378 If this option is set, the order of the items in a host list in a routing rule
18379 is randomized each time the list is used, unless an option in the routing rule
18380 overrides (see below). Randomizing the order of a host list can be used to do
18381 crude load sharing. However, if more than one mail address is routed by the
18382 same router to the same host list, the host lists are considered to be the same
18383 (even though they may be randomized into different orders) for the purpose of
18384 deciding whether to batch the deliveries into a single SMTP transaction.
18386 When &%hosts_randomize%& is true, a host list may be split
18387 into groups whose order is separately randomized. This makes it possible to
18388 set up MX-like behaviour. The boundaries between groups are indicated by an
18389 item that is just &`+`& in the host list. For example:
18391 route_list = * host1:host2:host3:+:host4:host5
18393 The order of the first three hosts and the order of the last two hosts is
18394 randomized for each use, but the first three always end up before the last two.
18395 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
18396 randomized host list is passed to an &(smtp)& transport that also has
18397 &%hosts_randomize set%&, the list is not re-randomized.
18400 .option route_data manualroute string&!! unset
18401 If this option is set, it must expand to yield the data part of a routing rule.
18402 Typically, the expansion string includes a lookup based on the domain. For
18405 route_data = ${lookup{$domain}dbm{/etc/routes}}
18407 If the expansion is forced to fail, or the result is an empty string, the
18408 router declines. Other kinds of expansion failure cause delivery to be
18412 .option route_list manualroute "string list" unset
18413 This string is a list of routing rules, in the form defined below. Note that,
18414 unlike most string lists, the items are separated by semicolons. This is so
18415 that they may contain colon-separated host lists.
18418 .option same_domain_copy_routing manualroute boolean false
18419 .cindex "address" "copying routing"
18420 Addresses with the same domain are normally routed by the &(manualroute)&
18421 router to the same list of hosts. However, this cannot be presumed, because the
18422 router options and preconditions may refer to the local part of the address. By
18423 default, therefore, Exim routes each address in a message independently. DNS
18424 servers run caches, so repeated DNS lookups are not normally expensive, and in
18425 any case, personal messages rarely have more than a few recipients.
18427 If you are running mailing lists with large numbers of subscribers at the same
18428 domain, and you are using a &(manualroute)& router which is independent of the
18429 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
18430 lookups for identical domains in one message. In this case, when
18431 &(manualroute)& routes an address to a remote transport, any other unrouted
18432 addresses in the message that have the same domain are automatically given the
18433 same routing without processing them independently. However, this is only done
18434 if &%headers_add%& and &%headers_remove%& are unset.
18439 .section "Routing rules in route_list" "SECID120"
18440 The value of &%route_list%& is a string consisting of a sequence of routing
18441 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
18442 entered as two semicolons. Alternatively, the list separator can be changed as
18443 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
18444 Empty rules are ignored. The format of each rule is
18446 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
18448 The following example contains two rules, each with a simple domain pattern and
18452 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
18453 thes.ref.example mail-3.ref.example:mail-4.ref.example
18455 The three parts of a rule are separated by white space. The pattern and the
18456 list of hosts can be enclosed in quotes if necessary, and if they are, the
18457 usual quoting rules apply. Each rule in a &%route_list%& must start with a
18458 single domain pattern, which is the only mandatory item in the rule. The
18459 pattern is in the same format as one item in a domain list (see section
18460 &<<SECTdomainlist>>&),
18461 except that it may not be the name of an interpolated file.
18462 That is, it may be wildcarded, or a regular expression, or a file or database
18463 lookup (with semicolons doubled, because of the use of semicolon as a separator
18464 in a &%route_list%&).
18466 The rules in &%route_list%& are searched in order until one of the patterns
18467 matches the domain that is being routed. The list of hosts and then options are
18468 then used as described below. If there is no match, the router declines. When
18469 &%route_list%& is set, &%route_data%& must not be set.
18473 .section "Routing rules in route_data" "SECID121"
18474 The use of &%route_list%& is convenient when there are only a small number of
18475 routing rules. For larger numbers, it is easier to use a file or database to
18476 hold the routing information, and use the &%route_data%& option instead.
18477 The value of &%route_data%& is a list of hosts, followed by (optional) options.
18478 Most commonly, &%route_data%& is set as a string that contains an
18479 expansion lookup. For example, suppose we place two routing rules in a file
18482 dict.ref.example: mail-1.ref.example:mail-2.ref.example
18483 thes.ref.example: mail-3.ref.example:mail-4.ref.example
18485 This data can be accessed by setting
18487 route_data = ${lookup{$domain}lsearch{/the/file/name}}
18489 Failure of the lookup results in an empty string, causing the router to
18490 decline. However, you do not have to use a lookup in &%route_data%&. The only
18491 requirement is that the result of expanding the string is a list of hosts,
18492 possibly followed by options, separated by white space. The list of hosts must
18493 be enclosed in quotes if it contains white space.
18498 .section "Format of the list of hosts" "SECID122"
18499 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
18500 always separately expanded before use. If the expansion fails, the router
18501 declines. The result of the expansion must be a colon-separated list of names
18502 and/or IP addresses, optionally also including ports. The format of each item
18503 in the list is described in the next section. The list separator can be changed
18504 as described in section &<<SECTlistconstruct>>&.
18506 If the list of hosts was obtained from a &%route_list%& item, the following
18507 variables are set during its expansion:
18510 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
18511 If the domain was matched against a regular expression, the numeric variables
18512 &$1$&, &$2$&, etc. may be set. For example:
18514 route_list = ^domain(\d+) host-$1.text.example
18517 &$0$& is always set to the entire domain.
18519 &$1$& is also set when partial matching is done in a file lookup.
18522 .vindex "&$value$&"
18523 If the pattern that matched the domain was a lookup item, the data that was
18524 looked up is available in the expansion variable &$value$&. For example:
18526 route_list = lsearch;;/some/file.routes $value
18530 Note the doubling of the semicolon in the pattern that is necessary because
18531 semicolon is the default route list separator.
18535 .section "Format of one host item" "SECTformatonehostitem"
18536 Each item in the list of hosts is either a host name or an IP address,
18537 optionally with an attached port number. When no port is given, an IP address
18538 is not enclosed in brackets. When a port is specified, it overrides the port
18539 specification on the transport. The port is separated from the name or address
18540 by a colon. This leads to some complications:
18543 Because colon is the default separator for the list of hosts, either
18544 the colon that specifies a port must be doubled, or the list separator must
18545 be changed. The following two examples have the same effect:
18547 route_list = * "host1.tld::1225 : host2.tld::1226"
18548 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
18551 When IPv6 addresses are involved, it gets worse, because they contain
18552 colons of their own. To make this case easier, it is permitted to
18553 enclose an IP address (either v4 or v6) in square brackets if a port
18554 number follows. For example:
18556 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
18560 .section "How the list of hosts is used" "SECThostshowused"
18561 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
18562 the hosts is tried, in the order specified, when carrying out the SMTP
18563 delivery. However, the order can be changed by setting the &%hosts_randomize%&
18564 option, either on the router (see section &<<SECTprioptman>>& above), or on the
18567 Hosts may be listed by name or by IP address. An unadorned name in the list of
18568 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
18569 interpreted as an indirection to a sublist of hosts obtained by looking up MX
18570 records in the DNS. For example:
18572 route_list = * x.y.z:p.q.r/MX:e.f.g
18574 If this feature is used with a port specifier, the port must come last. For
18577 route_list = * dom1.tld/mx::1225
18579 If the &%hosts_randomize%& option is set, the order of the items in the list is
18580 randomized before any lookups are done. Exim then scans the list; for any name
18581 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
18582 be an interface on the local host and the item is not the first in the list,
18583 Exim discards it and any subsequent items. If it is the first item, what
18584 happens is controlled by the
18585 .oindex "&%self%&" "in &(manualroute)& router"
18586 &%self%& option of the router.
18588 A name on the list that is followed by &`/MX`& is replaced with the list of
18589 hosts obtained by looking up MX records for the name. This is always a DNS
18590 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
18591 below) are not relevant here. The order of these hosts is determined by the
18592 preference values in the MX records, according to the usual rules. Because
18593 randomizing happens before the MX lookup, it does not affect the order that is
18594 defined by MX preferences.
18596 If the local host is present in the sublist obtained from MX records, but is
18597 not the most preferred host in that list, it and any equally or less
18598 preferred hosts are removed before the sublist is inserted into the main list.
18600 If the local host is the most preferred host in the MX list, what happens
18601 depends on where in the original list of hosts the &`/MX`& item appears. If it
18602 is not the first item (that is, there are previous hosts in the main list),
18603 Exim discards this name and any subsequent items in the main list.
18605 If the MX item is first in the list of hosts, and the local host is the
18606 most preferred host, what happens is controlled by the &%self%& option of the
18609 DNS failures when lookup up the MX records are treated in the same way as DNS
18610 failures when looking up IP addresses: &%pass_on_timeout%& and
18611 &%host_find_failed%& are used when relevant.
18613 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
18614 whether obtained from an MX lookup or not.
18618 .section "How the options are used" "SECThowoptused"
18619 The options are a sequence of words; in practice no more than three are ever
18620 present. One of the words can be the name of a transport; this overrides the
18621 &%transport%& option on the router for this particular routing rule only. The
18622 other words (if present) control randomization of the list of hosts on a
18623 per-rule basis, and how the IP addresses of the hosts are to be found when
18624 routing to a remote transport. These options are as follows:
18627 &%randomize%&: randomize the order of the hosts in this list, overriding the
18628 setting of &%hosts_randomize%& for this routing rule only.
18630 &%no_randomize%&: do not randomize the order of the hosts in this list,
18631 overriding the setting of &%hosts_randomize%& for this routing rule only.
18633 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
18634 find IP addresses. This function may ultimately cause a DNS lookup, but it may
18635 also look in &_/etc/hosts_& or other sources of information.
18637 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
18638 no address records are found. If there is a temporary DNS error (such as a
18639 timeout), delivery is deferred.
18644 route_list = domain1 host1:host2:host3 randomize bydns;\
18645 domain2 host4:host5
18647 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
18648 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
18649 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
18650 or &[gethostbyname()]&, and the result of the lookup is the result of that
18653 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
18654 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
18655 instead of TRY_AGAIN. That is why the default action is to try a DNS
18656 lookup first. Only if that gives a definite &"no such host"& is the local
18661 If no IP address for a host can be found, what happens is controlled by the
18662 &%host_find_failed%& option.
18665 When an address is routed to a local transport, IP addresses are not looked up.
18666 The host list is passed to the transport in the &$host$& variable.
18670 .section "Manualroute examples" "SECID123"
18671 In some of the examples that follow, the presence of the &%remote_smtp%&
18672 transport, as defined in the default configuration file, is assumed:
18675 .cindex "smart host" "example router"
18676 The &(manualroute)& router can be used to forward all external mail to a
18677 &'smart host'&. If you have set up, in the main part of the configuration, a
18678 named domain list that contains your local domains, for example:
18680 domainlist local_domains = my.domain.example
18682 You can arrange for all other domains to be routed to a smart host by making
18683 your first router something like this:
18686 driver = manualroute
18687 domains = !+local_domains
18688 transport = remote_smtp
18689 route_list = * smarthost.ref.example
18691 This causes all non-local addresses to be sent to the single host
18692 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
18693 they are tried in order
18694 (but you can use &%hosts_randomize%& to vary the order each time).
18695 Another way of configuring the same thing is this:
18698 driver = manualroute
18699 transport = remote_smtp
18700 route_list = !+local_domains smarthost.ref.example
18702 There is no difference in behaviour between these two routers as they stand.
18703 However, they behave differently if &%no_more%& is added to them. In the first
18704 example, the router is skipped if the domain does not match the &%domains%&
18705 precondition; the following router is always tried. If the router runs, it
18706 always matches the domain and so can never decline. Therefore, &%no_more%&
18707 would have no effect. In the second case, the router is never skipped; it
18708 always runs. However, if it doesn't match the domain, it declines. In this case
18709 &%no_more%& would prevent subsequent routers from running.
18712 .cindex "mail hub example"
18713 A &'mail hub'& is a host which receives mail for a number of domains via MX
18714 records in the DNS and delivers it via its own private routing mechanism. Often
18715 the final destinations are behind a firewall, with the mail hub being the one
18716 machine that can connect to machines both inside and outside the firewall. The
18717 &(manualroute)& router is usually used on a mail hub to route incoming messages
18718 to the correct hosts. For a small number of domains, the routing can be inline,
18719 using the &%route_list%& option, but for a larger number a file or database
18720 lookup is easier to manage.
18722 If the domain names are in fact the names of the machines to which the mail is
18723 to be sent by the mail hub, the configuration can be quite simple. For
18727 driver = manualroute
18728 transport = remote_smtp
18729 route_list = *.rhodes.tvs.example $domain
18731 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
18732 whose names are the same as the mail domains. A similar approach can be taken
18733 if the host name can be obtained from the domain name by a string manipulation
18734 that the expansion facilities can handle. Otherwise, a lookup based on the
18735 domain can be used to find the host:
18738 driver = manualroute
18739 transport = remote_smtp
18740 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
18742 The result of the lookup must be the name or IP address of the host (or
18743 hosts) to which the address is to be routed. If the lookup fails, the route
18744 data is empty, causing the router to decline. The address then passes to the
18748 .cindex "batched SMTP output example"
18749 .cindex "SMTP" "batched outgoing; example"
18750 You can use &(manualroute)& to deliver messages to pipes or files in batched
18751 SMTP format for onward transportation by some other means. This is one way of
18752 storing mail for a dial-up host when it is not connected. The route list entry
18753 can be as simple as a single domain name in a configuration like this:
18756 driver = manualroute
18757 transport = batchsmtp_appendfile
18758 route_list = saved.domain.example
18760 though often a pattern is used to pick up more than one domain. If there are
18761 several domains or groups of domains with different transport requirements,
18762 different transports can be listed in the routing information:
18765 driver = manualroute
18767 *.saved.domain1.example $domain batch_appendfile; \
18768 *.saved.domain2.example \
18769 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
18772 .vindex "&$domain$&"
18774 The first of these just passes the domain in the &$host$& variable, which
18775 doesn't achieve much (since it is also in &$domain$&), but the second does a
18776 file lookup to find a value to pass, causing the router to decline to handle
18777 the address if the lookup fails.
18780 .cindex "UUCP" "example of router for"
18781 Routing mail directly to UUCP software is a specific case of the use of
18782 &(manualroute)& in a gateway to another mail environment. This is an example of
18783 one way it can be done:
18789 command = /usr/local/bin/uux -r - \
18790 ${substr_-5:$host}!rmail ${local_part}
18791 return_fail_output = true
18796 driver = manualroute
18798 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
18800 The file &_/usr/local/exim/uucphosts_& contains entries like
18802 darksite.ethereal.example: darksite.UUCP
18804 It can be set up more simply without adding and removing &".UUCP"& but this way
18805 makes clear the distinction between the domain name
18806 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
18808 .ecindex IIDmanrou1
18809 .ecindex IIDmanrou2
18818 . ////////////////////////////////////////////////////////////////////////////
18819 . ////////////////////////////////////////////////////////////////////////////
18821 .chapter "The queryprogram router" "CHAPdriverlast"
18822 .scindex IIDquerou1 "&(queryprogram)& router"
18823 .scindex IIDquerou2 "routers" "&(queryprogram)&"
18824 .cindex "routing" "by external program"
18825 The &(queryprogram)& router routes an address by running an external command
18826 and acting on its output. This is an expensive way to route, and is intended
18827 mainly for use in lightly-loaded systems, or for performing experiments.
18828 However, if it is possible to use the precondition options (&%domains%&,
18829 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
18830 be used in special cases, even on a busy host. There are the following private
18832 .cindex "options" "&(queryprogram)& router"
18834 .option command queryprogram string&!! unset
18835 This option must be set. It specifies the command that is to be run. The
18836 command is split up into a command name and arguments, and then each is
18837 expanded separately (exactly as for a &(pipe)& transport, described in chapter
18838 &<<CHAPpipetransport>>&).
18841 .option command_group queryprogram string unset
18842 .cindex "gid (group id)" "in &(queryprogram)& router"
18843 This option specifies a gid to be set when running the command while routing an
18844 address for deliver. It must be set if &%command_user%& specifies a numerical
18845 uid. If it begins with a digit, it is interpreted as the numerical value of the
18846 gid. Otherwise it is looked up using &[getgrnam()]&.
18849 .option command_user queryprogram string unset
18850 .cindex "uid (user id)" "for &(queryprogram)&"
18851 This option must be set. It specifies the uid which is set when running the
18852 command while routing an address for delivery. If the value begins with a digit,
18853 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
18854 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
18855 not set, a value for the gid also.
18857 &*Warning:*& Changing uid and gid is possible only when Exim is running as
18858 root, which it does during a normal delivery in a conventional configuration.
18859 However, when an address is being verified during message reception, Exim is
18860 usually running as the Exim user, not as root. If the &(queryprogram)& router
18861 is called from a non-root process, Exim cannot change uid or gid before running
18862 the command. In this circumstance the command runs under the current uid and
18866 .option current_directory queryprogram string /
18867 This option specifies an absolute path which is made the current directory
18868 before running the command.
18871 .option timeout queryprogram time 1h
18872 If the command does not complete within the timeout period, its process group
18873 is killed and the message is frozen. A value of zero time specifies no
18877 The standard output of the command is connected to a pipe, which is read when
18878 the command terminates. It should consist of a single line of output,
18879 containing up to five fields, separated by white space. The maximum length of
18880 the line is 1023 characters. Longer lines are silently truncated. The first
18881 field is one of the following words (case-insensitive):
18884 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
18887 &'Decline'&: the router declines; pass the address to the next router, unless
18888 &%no_more%& is set.
18890 &'Fail'&: routing failed; do not pass the address to any more routers. Any
18891 subsequent text on the line is an error message. If the router is run as part
18892 of address verification during an incoming SMTP message, the message is
18893 included in the SMTP response.
18895 &'Defer'&: routing could not be completed at this time; try again later. Any
18896 subsequent text on the line is an error message which is logged. It is not
18897 included in any SMTP response.
18899 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
18901 &'Pass'&: pass the address to the next router (or the router specified by
18902 &%pass_router%&), overriding &%no_more%&.
18904 &'Redirect'&: the message is redirected. The remainder of the line is a list of
18905 new addresses, which are routed independently, starting with the first router,
18906 or the router specified by &%redirect_router%&, if set.
18909 When the first word is &'accept'&, the remainder of the line consists of a
18910 number of keyed data values, as follows (split into two lines here, to fit on
18913 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
18914 LOOKUP=byname|bydns DATA=<text>
18916 The data items can be given in any order, and all are optional. If no transport
18917 is included, the transport specified by the generic &%transport%& option is
18918 used. The list of hosts and the lookup type are needed only if the transport is
18919 an &(smtp)& transport that does not itself supply a list of hosts.
18921 The format of the list of hosts is the same as for the &(manualroute)& router.
18922 As well as host names and IP addresses with optional port numbers, as described
18923 in section &<<SECTformatonehostitem>>&, it may contain names followed by
18924 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
18925 (see section &<<SECThostshowused>>&).
18927 If the lookup type is not specified, Exim behaves as follows when trying to
18928 find an IP address for each host: First, a DNS lookup is done. If this yields
18929 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
18930 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
18931 result of the lookup is the result of that call.
18933 .vindex "&$address_data$&"
18934 If the DATA field is set, its value is placed in the &$address_data$&
18935 variable. For example, this return line
18937 accept hosts=x1.y.example:x2.y.example data="rule1"
18939 routes the address to the default transport, passing a list of two hosts. When
18940 the transport runs, the string &"rule1"& is in &$address_data$&.
18941 .ecindex IIDquerou1
18942 .ecindex IIDquerou2
18947 . ////////////////////////////////////////////////////////////////////////////
18948 . ////////////////////////////////////////////////////////////////////////////
18950 .chapter "The redirect router" "CHAPredirect"
18951 .scindex IIDredrou1 "&(redirect)& router"
18952 .scindex IIDredrou2 "routers" "&(redirect)&"
18953 .cindex "alias file" "in a &(redirect)& router"
18954 .cindex "address redirection" "&(redirect)& router"
18955 The &(redirect)& router handles several kinds of address redirection. Its most
18956 common uses are for resolving local part aliases from a central alias file
18957 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
18958 files, but it has many other potential uses. The incoming address can be
18959 redirected in several different ways:
18962 It can be replaced by one or more new addresses which are themselves routed
18965 It can be routed to be delivered to a given file or directory.
18967 It can be routed to be delivered to a specified pipe command.
18969 It can cause an automatic reply to be generated.
18971 It can be forced to fail, optionally with a custom error message.
18973 It can be temporarily deferred, optionally with a custom message.
18975 It can be discarded.
18978 The generic &%transport%& option must not be set for &(redirect)& routers.
18979 However, there are some private options which define transports for delivery to
18980 files and pipes, and for generating autoreplies. See the &%file_transport%&,
18981 &%pipe_transport%& and &%reply_transport%& descriptions below.
18985 .section "Redirection data" "SECID124"
18986 The router operates by interpreting a text string which it obtains either by
18987 expanding the contents of the &%data%& option, or by reading the entire
18988 contents of a file whose name is given in the &%file%& option. These two
18989 options are mutually exclusive. The first is commonly used for handling system
18990 aliases, in a configuration like this:
18994 data = ${lookup{$local_part}lsearch{/etc/aliases}}
18996 If the lookup fails, the expanded string in this example is empty. When the
18997 expansion of &%data%& results in an empty string, the router declines. A forced
18998 expansion failure also causes the router to decline; other expansion failures
18999 cause delivery to be deferred.
19001 A configuration using &%file%& is commonly used for handling users'
19002 &_.forward_& files, like this:
19007 file = $home/.forward
19010 If the file does not exist, or causes no action to be taken (for example, it is
19011 empty or consists only of comments), the router declines. &*Warning*&: This
19012 is not the case when the file contains syntactically valid items that happen to
19013 yield empty addresses, for example, items containing only RFC 2822 address
19018 .section "Forward files and address verification" "SECID125"
19019 .cindex "address redirection" "while verifying"
19020 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
19021 &_.forward_& files, as in the example above. There are two reasons for this:
19024 When Exim is receiving an incoming SMTP message from a remote host, it is
19025 running under the Exim uid, not as root. Exim is unable to change uid to read
19026 the file as the user, and it may not be able to read it as the Exim user. So in
19027 practice the router may not be able to operate.
19029 However, even when the router can operate, the existence of a &_.forward_& file
19030 is unimportant when verifying an address. What should be checked is whether the
19031 local part is a valid user name or not. Cutting out the redirection processing
19032 saves some resources.
19040 .section "Interpreting redirection data" "SECID126"
19041 .cindex "Sieve filter" "specifying in redirection data"
19042 .cindex "filter" "specifying in redirection data"
19043 The contents of the data string, whether obtained from &%data%& or &%file%&,
19044 can be interpreted in two different ways:
19047 If the &%allow_filter%& option is set true, and the data begins with the text
19048 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
19049 &'filtering'& instructions in the form of an Exim or Sieve filter file,
19050 respectively. Details of the syntax and semantics of filter files are described
19051 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
19052 document is intended for use by end users.
19054 Otherwise, the data must be a comma-separated list of redirection items, as
19055 described in the next section.
19058 When a message is redirected to a file (a &"mail folder"&), the file name given
19059 in a non-filter redirection list must always be an absolute path. A filter may
19060 generate a relative path &-- how this is handled depends on the transport's
19061 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
19062 for the &(appendfile)& transport.
19066 .section "Items in a non-filter redirection list" "SECTitenonfilred"
19067 .cindex "address redirection" "non-filter list items"
19068 When the redirection data is not an Exim or Sieve filter, for example, if it
19069 comes from a conventional alias or forward file, it consists of a list of
19070 addresses, file names, pipe commands, or certain special items (see section
19071 &<<SECTspecitredli>>& below). The special items can be individually enabled or
19072 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
19073 depending on their default values. The items in the list are separated by
19074 commas or newlines.
19075 If a comma is required in an item, the entire item must be enclosed in double
19078 Lines starting with a # character are comments, and are ignored, and # may
19079 also appear following a comma, in which case everything between the # and the
19080 next newline character is ignored.
19082 If an item is entirely enclosed in double quotes, these are removed. Otherwise
19083 double quotes are retained because some forms of mail address require their use
19084 (but never to enclose the entire address). In the following description,
19085 &"item"& refers to what remains after any surrounding double quotes have been
19088 .vindex "&$local_part$&"
19089 &*Warning*&: If you use an Exim expansion to construct a redirection address,
19090 and the expansion contains a reference to &$local_part$&, you should make use
19091 of the &%quote_local_part%& expansion operator, in case the local part contains
19092 special characters. For example, to redirect all mail for the domain
19093 &'obsolete.example'&, retaining the existing local part, you could use this
19096 data = ${quote_local_part:$local_part}@newdomain.example
19100 .section "Redirecting to a local mailbox" "SECTredlocmai"
19101 .cindex "routing" "loops in"
19102 .cindex "loop" "while routing, avoidance of"
19103 .cindex "address redirection" "to local mailbox"
19104 A redirection item may safely be the same as the address currently under
19105 consideration. This does not cause a routing loop, because a router is
19106 automatically skipped if any ancestor of the address that is being processed
19107 is the same as the current address and was processed by the current router.
19108 Such an address is therefore passed to the following routers, so it is handled
19109 as if there were no redirection. When making this loop-avoidance test, the
19110 complete local part, including any prefix or suffix, is used.
19112 .cindex "address redirection" "local part without domain"
19113 Specifying the same local part without a domain is a common usage in personal
19114 filter files when the user wants to have messages delivered to the local
19115 mailbox and also forwarded elsewhere. For example, the user whose login is
19116 &'cleo'& might have a &_.forward_& file containing this:
19118 cleo, cleopatra@egypt.example
19120 .cindex "backslash in alias file"
19121 .cindex "alias file" "backslash in"
19122 For compatibility with other MTAs, such unqualified local parts may be
19123 preceded by &"\"&, but this is not a requirement for loop prevention. However,
19124 it does make a difference if more than one domain is being handled
19127 If an item begins with &"\"& and the rest of the item parses as a valid RFC
19128 2822 address that does not include a domain, the item is qualified using the
19129 domain of the incoming address. In the absence of a leading &"\"&, unqualified
19130 addresses are qualified using the value in &%qualify_recipient%&, but you can
19131 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
19133 Care must be taken if there are alias names for local users.
19134 Consider an MTA handling a single local domain where the system alias file
19139 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
19140 messages in the local mailbox, and also forward copies elsewhere. He creates
19143 Sam.Reman, spqr@reme.elsewhere.example
19145 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
19146 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
19147 second time round, because it has previously routed it,
19148 and the following routers presumably cannot handle the alias. The forward file
19149 should really contain
19151 spqr, spqr@reme.elsewhere.example
19153 but because this is such a common error, the &%check_ancestor%& option (see
19154 below) exists to provide a way to get round it. This is normally set on a
19155 &(redirect)& router that is handling users' &_.forward_& files.
19159 .section "Special items in redirection lists" "SECTspecitredli"
19160 In addition to addresses, the following types of item may appear in redirection
19161 lists (that is, in non-filter redirection data):
19164 .cindex "pipe" "in redirection list"
19165 .cindex "address redirection" "to pipe"
19166 An item is treated as a pipe command if it begins with &"|"& and does not parse
19167 as a valid RFC 2822 address that includes a domain. A transport for running the
19168 command must be specified by the &%pipe_transport%& option.
19169 Normally, either the router or the transport specifies a user and a group under
19170 which to run the delivery. The default is to use the Exim user and group.
19172 Single or double quotes can be used for enclosing the individual arguments of
19173 the pipe command; no interpretation of escapes is done for single quotes. If
19174 the command contains a comma character, it is necessary to put the whole item
19175 in double quotes, for example:
19177 "|/some/command ready,steady,go"
19179 since items in redirection lists are terminated by commas. Do not, however,
19180 quote just the command. An item such as
19182 |"/some/command ready,steady,go"
19184 is interpreted as a pipe with a rather strange command name, and no arguments.
19186 Note that the above example assumes that the text comes from a lookup source
19187 of some sort, so that the quotes are part of the data. If composing a
19188 redirect router with a &%data%& option directly specifying this command, the
19189 quotes will be used by the configuration parser to define the extent of one
19190 string, but will not be passed down into the redirect router itself. There
19191 are two main approaches to get around this: escape quotes to be part of the
19192 data itself, or avoid using this mechanism and instead create a custom
19193 transport with the &%command%& option set and reference that transport from
19194 an &%accept%& router.
19197 .cindex "file" "in redirection list"
19198 .cindex "address redirection" "to file"
19199 An item is interpreted as a path name if it begins with &"/"& and does not
19200 parse as a valid RFC 2822 address that includes a domain. For example,
19202 /home/world/minbari
19204 is treated as a file name, but
19206 /s=molari/o=babylon/@x400gate.way
19208 is treated as an address. For a file name, a transport must be specified using
19209 the &%file_transport%& option. However, if the generated path name ends with a
19210 forward slash character, it is interpreted as a directory name rather than a
19211 file name, and &%directory_transport%& is used instead.
19213 Normally, either the router or the transport specifies a user and a group under
19214 which to run the delivery. The default is to use the Exim user and group.
19216 .cindex "&_/dev/null_&"
19217 However, if a redirection item is the path &_/dev/null_&, delivery to it is
19218 bypassed at a high level, and the log entry shows &"**bypassed**"&
19219 instead of a transport name. In this case the user and group are not used.
19222 .cindex "included address list"
19223 .cindex "address redirection" "included external list"
19224 If an item is of the form
19226 :include:<path name>
19228 a list of further items is taken from the given file and included at that
19229 point. &*Note*&: Such a file can not be a filter file; it is just an
19230 out-of-line addition to the list. The items in the included list are separated
19231 by commas or newlines and are not subject to expansion. If this is the first
19232 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
19233 the alias name. This example is incorrect:
19235 list1 :include:/opt/lists/list1
19237 It must be given as
19239 list1: :include:/opt/lists/list1
19242 .cindex "address redirection" "to black hole"
19243 Sometimes you want to throw away mail to a particular local part. Making the
19244 &%data%& option expand to an empty string does not work, because that causes
19245 the router to decline. Instead, the alias item
19246 .cindex "black hole"
19247 .cindex "abandoning mail"
19248 &':blackhole:'& can be used. It does what its name implies. No delivery is
19249 done, and no error message is generated. This has the same effect as specifing
19250 &_/dev/null_& as a destination, but it can be independently disabled.
19252 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
19253 delivery is done for the original local part, even if other redirection items
19254 are present. If you are generating a multi-item list (for example, by reading a
19255 database) and need the ability to provide a no-op item, you must use
19259 .cindex "delivery" "forcing failure"
19260 .cindex "delivery" "forcing deferral"
19261 .cindex "failing delivery" "forcing"
19262 .cindex "deferred delivery, forcing"
19263 .cindex "customizing" "failure message"
19264 An attempt to deliver a particular address can be deferred or forced to fail by
19265 redirection items of the form
19270 respectively. When a redirection list contains such an item, it applies
19271 to the entire redirection; any other items in the list are ignored. Any
19272 text following &':fail:'& or &':defer:'& is placed in the error text
19273 associated with the failure. For example, an alias file might contain:
19275 X.Employee: :fail: Gone away, no forwarding address
19277 In the case of an address that is being verified from an ACL or as the subject
19279 .cindex "VRFY" "error text, display of"
19280 VRFY command, the text is included in the SMTP error response by
19282 .cindex "EXPN" "error text, display of"
19283 The text is not included in the response to an EXPN command. In non-SMTP cases
19284 the text is included in the error message that Exim generates.
19286 .cindex "SMTP" "error codes"
19287 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
19288 &':fail:'&. However, if the message starts with three digits followed by a
19289 space, optionally followed by an extended code of the form &'n.n.n'&, also
19290 followed by a space, and the very first digit is the same as the default error
19291 code, the code from the message is used instead. If the very first digit is
19292 incorrect, a panic error is logged, and the default code is used. You can
19293 suppress the use of the supplied code in a redirect router by setting the
19294 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
19297 .vindex "&$acl_verify_message$&"
19298 In an ACL, an explicitly provided message overrides the default, but the
19299 default message is available in the variable &$acl_verify_message$& and can
19300 therefore be included in a custom message if this is desired.
19302 Normally the error text is the rest of the redirection list &-- a comma does
19303 not terminate it &-- but a newline does act as a terminator. Newlines are not
19304 normally present in alias expansions. In &(lsearch)& lookups they are removed
19305 as part of the continuation process, but they may exist in other kinds of
19306 lookup and in &':include:'& files.
19308 During routing for message delivery (as opposed to verification), a redirection
19309 containing &':fail:'& causes an immediate failure of the incoming address,
19310 whereas &':defer:'& causes the message to remain on the queue so that a
19311 subsequent delivery attempt can happen at a later time. If an address is
19312 deferred for too long, it will ultimately fail, because the normal retry
19316 .cindex "alias file" "exception to default"
19317 Sometimes it is useful to use a single-key search type with a default (see
19318 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
19319 for exceptions to the default. These can be handled by aliasing them to
19320 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
19321 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
19322 results in an empty redirection list has the same effect.
19326 .section "Duplicate addresses" "SECTdupaddr"
19327 .cindex "duplicate addresses"
19328 .cindex "address duplicate, discarding"
19329 .cindex "pipe" "duplicated"
19330 Exim removes duplicate addresses from the list to which it is delivering, so as
19331 to deliver just one copy to each address. This does not apply to deliveries
19332 routed to pipes by different immediate parent addresses, but an indirect
19333 aliasing scheme of the type
19335 pipe: |/some/command $local_part
19339 does not work with a message that is addressed to both local parts, because
19340 when the second is aliased to the intermediate local part &"pipe"& it gets
19341 discarded as being the same as a previously handled address. However, a scheme
19344 localpart1: |/some/command $local_part
19345 localpart2: |/some/command $local_part
19347 does result in two different pipe deliveries, because the immediate parents of
19348 the pipes are distinct.
19352 .section "Repeated redirection expansion" "SECID128"
19353 .cindex "repeated redirection expansion"
19354 .cindex "address redirection" "repeated for each delivery attempt"
19355 When a message cannot be delivered to all of its recipients immediately,
19356 leading to two or more delivery attempts, redirection expansion is carried out
19357 afresh each time for those addresses whose children were not all previously
19358 delivered. If redirection is being used as a mailing list, this can lead to new
19359 members of the list receiving copies of old messages. The &%one_time%& option
19360 can be used to avoid this.
19363 .section "Errors in redirection lists" "SECID129"
19364 .cindex "address redirection" "errors"
19365 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
19366 error is skipped, and an entry is written to the main log. This may be useful
19367 for mailing lists that are automatically managed. Otherwise, if an error is
19368 detected while generating the list of new addresses, the original address is
19369 deferred. See also &%syntax_errors_to%&.
19373 .section "Private options for the redirect router" "SECID130"
19375 .cindex "options" "&(redirect)& router"
19376 The private options for the &(redirect)& router are as follows:
19379 .option allow_defer redirect boolean false
19380 Setting this option allows the use of &':defer:'& in non-filter redirection
19381 data, or the &%defer%& command in an Exim filter file.
19384 .option allow_fail redirect boolean false
19385 .cindex "failing delivery" "from filter"
19386 If this option is true, the &':fail:'& item can be used in a redirection list,
19387 and the &%fail%& command may be used in an Exim filter file.
19390 .option allow_filter redirect boolean false
19391 .cindex "filter" "enabling use of"
19392 .cindex "Sieve filter" "enabling use of"
19393 Setting this option allows Exim to interpret redirection data that starts with
19394 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
19395 are some features of Exim filter files that some administrators may wish to
19396 lock out; see the &%forbid_filter_%&&'xxx'& options below.
19398 It is also possible to lock out Exim filters or Sieve filters while allowing
19399 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
19402 The filter is run using the uid and gid set by the generic &%user%& and
19403 &%group%& options. These take their defaults from the password data if
19404 &%check_local_user%& is set, so in the normal case of users' personal filter
19405 files, the filter is run as the relevant user. When &%allow_filter%& is set
19406 true, Exim insists that either &%check_local_user%& or &%user%& is set.
19410 .option allow_freeze redirect boolean false
19411 .cindex "freezing messages" "allowing in filter"
19412 Setting this option allows the use of the &%freeze%& command in an Exim filter.
19413 This command is more normally encountered in system filters, and is disabled by
19414 default for redirection filters because it isn't something you usually want to
19415 let ordinary users do.
19419 .option check_ancestor redirect boolean false
19420 This option is concerned with handling generated addresses that are the same
19421 as some address in the list of redirection ancestors of the current address.
19422 Although it is turned off by default in the code, it is set in the default
19423 configuration file for handling users' &_.forward_& files. It is recommended
19424 for this use of the &(redirect)& router.
19426 When &%check_ancestor%& is set, if a generated address (including the domain)
19427 is the same as any ancestor of the current address, it is replaced by a copy of
19428 the current address. This helps in the case where local part A is aliased to B,
19429 and B has a &_.forward_& file pointing back to A. For example, within a single
19430 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
19431 &_&~jb/.forward_& contains:
19433 \Joe.Bloggs, <other item(s)>
19435 Without the &%check_ancestor%& setting, either local part (&"jb"& or
19436 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
19437 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
19438 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
19439 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
19440 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
19441 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
19442 original address. See also the &%repeat_use%& option below.
19445 .option check_group redirect boolean "see below"
19446 When the &%file%& option is used, the group owner of the file is checked only
19447 when this option is set. The permitted groups are those listed in the
19448 &%owngroups%& option, together with the user's default group if
19449 &%check_local_user%& is set. If the file has the wrong group, routing is
19450 deferred. The default setting for this option is true if &%check_local_user%&
19451 is set and the &%modemask%& option permits the group write bit, or if the
19452 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
19456 .option check_owner redirect boolean "see below"
19457 When the &%file%& option is used, the owner of the file is checked only when
19458 this option is set. If &%check_local_user%& is set, the local user is
19459 permitted; otherwise the owner must be one of those listed in the &%owners%&
19460 option. The default value for this option is true if &%check_local_user%& or
19461 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
19464 .option data redirect string&!! unset
19465 This option is mutually exclusive with &%file%&. One or other of them must be
19466 set, but not both. The contents of &%data%& are expanded, and then used as the
19467 list of forwarding items, or as a set of filtering instructions. If the
19468 expansion is forced to fail, or the result is an empty string or a string that
19469 has no effect (consists entirely of comments), the router declines.
19471 When filtering instructions are used, the string must begin with &"#Exim
19472 filter"&, and all comments in the string, including this initial one, must be
19473 terminated with newline characters. For example:
19475 data = #Exim filter\n\
19476 if $h_to: contains Exim then save $home/mail/exim endif
19478 If you are reading the data from a database where newlines cannot be included,
19479 you can use the &${sg}$& expansion item to turn the escape string of your
19480 choice into a newline.
19483 .option directory_transport redirect string&!! unset
19484 A &(redirect)& router sets up a direct delivery to a directory when a path name
19485 ending with a slash is specified as a new &"address"&. The transport used is
19486 specified by this option, which, after expansion, must be the name of a
19487 configured transport. This should normally be an &(appendfile)& transport.
19490 .option file redirect string&!! unset
19491 This option specifies the name of a file that contains the redirection data. It
19492 is mutually exclusive with the &%data%& option. The string is expanded before
19493 use; if the expansion is forced to fail, the router declines. Other expansion
19494 failures cause delivery to be deferred. The result of a successful expansion
19495 must be an absolute path. The entire file is read and used as the redirection
19496 data. If the data is an empty string or a string that has no effect (consists
19497 entirely of comments), the router declines.
19499 .cindex "NFS" "checking for file existence"
19500 If the attempt to open the file fails with a &"does not exist"& error, Exim
19501 runs a check on the containing directory,
19502 unless &%ignore_enotdir%& is true (see below).
19503 If the directory does not appear to exist, delivery is deferred. This can
19504 happen when users' &_.forward_& files are in NFS-mounted directories, and there
19505 is a mount problem. If the containing directory does exist, but the file does
19506 not, the router declines.
19509 .option file_transport redirect string&!! unset
19510 .vindex "&$address_file$&"
19511 A &(redirect)& router sets up a direct delivery to a file when a path name not
19512 ending in a slash is specified as a new &"address"&. The transport used is
19513 specified by this option, which, after expansion, must be the name of a
19514 configured transport. This should normally be an &(appendfile)& transport. When
19515 it is running, the file name is in &$address_file$&.
19518 .option filter_prepend_home redirect boolean true
19519 When this option is true, if a &(save)& command in an Exim filter specifies a
19520 relative path, and &$home$& is defined, it is automatically prepended to the
19521 relative path. If this option is set false, this action does not happen. The
19522 relative path is then passed to the transport unmodified.
19525 .option forbid_blackhole redirect boolean false
19526 If this option is true, the &':blackhole:'& item may not appear in a
19530 .option forbid_exim_filter redirect boolean false
19531 If this option is set true, only Sieve filters are permitted when
19532 &%allow_filter%& is true.
19537 .option forbid_file redirect boolean false
19538 .cindex "delivery" "to file; forbidding"
19539 .cindex "Sieve filter" "forbidding delivery to a file"
19540 .cindex "Sieve filter" "&""keep""& facility; disabling"
19541 If this option is true, this router may not generate a new address that
19542 specifies delivery to a local file or directory, either from a filter or from a
19543 conventional forward file. This option is forced to be true if &%one_time%& is
19544 set. It applies to Sieve filters as well as to Exim filters, but if true, it
19545 locks out the Sieve's &"keep"& facility.
19548 .option forbid_filter_dlfunc redirect boolean false
19549 .cindex "filter" "locking out certain features"
19550 If this option is true, string expansions in Exim filters are not allowed to
19551 make use of the &%dlfunc%& expansion facility to run dynamically loaded
19554 .option forbid_filter_existstest redirect boolean false
19555 .cindex "expansion" "statting a file"
19556 If this option is true, string expansions in Exim filters are not allowed to
19557 make use of the &%exists%& condition or the &%stat%& expansion item.
19559 .option forbid_filter_logwrite redirect boolean false
19560 If this option is true, use of the logging facility in Exim filters is not
19561 permitted. Logging is in any case available only if the filter is being run
19562 under some unprivileged uid (which is normally the case for ordinary users'
19563 &_.forward_& files).
19566 .option forbid_filter_lookup redirect boolean false
19567 If this option is true, string expansions in Exim filter files are not allowed
19568 to make use of &%lookup%& items.
19571 .option forbid_filter_perl redirect boolean false
19572 This option has an effect only if Exim is built with embedded Perl support. If
19573 it is true, string expansions in Exim filter files are not allowed to make use
19574 of the embedded Perl support.
19577 .option forbid_filter_readfile redirect boolean false
19578 If this option is true, string expansions in Exim filter files are not allowed
19579 to make use of &%readfile%& items.
19582 .option forbid_filter_readsocket redirect boolean false
19583 If this option is true, string expansions in Exim filter files are not allowed
19584 to make use of &%readsocket%& items.
19587 .option forbid_filter_reply redirect boolean false
19588 If this option is true, this router may not generate an automatic reply
19589 message. Automatic replies can be generated only from Exim or Sieve filter
19590 files, not from traditional forward files. This option is forced to be true if
19591 &%one_time%& is set.
19594 .option forbid_filter_run redirect boolean false
19595 If this option is true, string expansions in Exim filter files are not allowed
19596 to make use of &%run%& items.
19599 .option forbid_include redirect boolean false
19600 If this option is true, items of the form
19602 :include:<path name>
19604 are not permitted in non-filter redirection lists.
19607 .option forbid_pipe redirect boolean false
19608 .cindex "delivery" "to pipe; forbidding"
19609 If this option is true, this router may not generate a new address which
19610 specifies delivery to a pipe, either from an Exim filter or from a conventional
19611 forward file. This option is forced to be true if &%one_time%& is set.
19614 .option forbid_sieve_filter redirect boolean false
19615 If this option is set true, only Exim filters are permitted when
19616 &%allow_filter%& is true.
19619 .cindex "SMTP" "error codes"
19620 .option forbid_smtp_code redirect boolean false
19621 If this option is set true, any SMTP error codes that are present at the start
19622 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
19623 the default codes (451 and 550, respectively) are always used.
19628 .option hide_child_in_errmsg redirect boolean false
19629 .cindex "bounce message" "redirection details; suppressing"
19630 If this option is true, it prevents Exim from quoting a child address if it
19631 generates a bounce or delay message for it. Instead it says &"an address
19632 generated from <&'the top level address'&>"&. Of course, this applies only to
19633 bounces generated locally. If a message is forwarded to another host, &'its'&
19634 bounce may well quote the generated address.
19637 .option ignore_eacces redirect boolean false
19639 If this option is set and an attempt to open a redirection file yields the
19640 EACCES error (permission denied), the &(redirect)& router behaves as if the
19641 file did not exist.
19644 .option ignore_enotdir redirect boolean false
19646 If this option is set and an attempt to open a redirection file yields the
19647 ENOTDIR error (something on the path is not a directory), the &(redirect)&
19648 router behaves as if the file did not exist.
19650 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
19651 router that has the &%file%& option set discovers that the file does not exist
19652 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
19653 against unmounted NFS directories. If the parent can not be statted, delivery
19654 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
19655 is set, because that option tells Exim to ignore &"something on the path is not
19656 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
19657 that some operating systems give ENOENT where others give ENOTDIR.
19661 .option include_directory redirect string unset
19662 If this option is set, the path names of any &':include:'& items in a
19663 redirection list must start with this directory.
19666 .option modemask redirect "octal integer" 022
19667 This specifies mode bits which must not be set for a file specified by the
19668 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
19671 .option one_time redirect boolean false
19672 .cindex "one-time aliasing/forwarding expansion"
19673 .cindex "alias file" "one-time expansion"
19674 .cindex "forward file" "one-time expansion"
19675 .cindex "mailing lists" "one-time expansion"
19676 .cindex "address redirection" "one-time expansion"
19677 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
19678 files each time it tries to deliver a message causes a problem when one or more
19679 of the generated addresses fails be delivered at the first attempt. The problem
19680 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
19681 but of what happens when the redirection list changes during the time that the
19682 message is on Exim's queue. This is particularly true in the case of mailing
19683 lists, where new subscribers might receive copies of messages that were posted
19684 before they subscribed.
19686 If &%one_time%& is set and any addresses generated by the router fail to
19687 deliver at the first attempt, the failing addresses are added to the message as
19688 &"top level"& addresses, and the parent address that generated them is marked
19689 &"delivered"&. Thus, redirection does not happen again at the next delivery
19692 &*Warning 1*&: Any header line addition or removal that is specified by this
19693 router would be lost if delivery did not succeed at the first attempt. For this
19694 reason, the &%headers_add%& and &%headers_remove%& generic options are not
19695 permitted when &%one_time%& is set.
19697 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
19698 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
19699 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
19701 &*Warning 3*&: The &%unseen%& generic router option may not be set with
19704 The original top-level address is remembered with each of the generated
19705 addresses, and is output in any log messages. However, any intermediate parent
19706 addresses are not recorded. This makes a difference to the log only if
19707 &%all_parents%& log selector is set. It is expected that &%one_time%& will
19708 typically be used for mailing lists, where there is normally just one level of
19712 .option owners redirect "string list" unset
19713 .cindex "ownership" "alias file"
19714 .cindex "ownership" "forward file"
19715 .cindex "alias file" "ownership"
19716 .cindex "forward file" "ownership"
19717 This specifies a list of permitted owners for the file specified by &%file%&.
19718 This list is in addition to the local user when &%check_local_user%& is set.
19719 See &%check_owner%& above.
19722 .option owngroups redirect "string list" unset
19723 This specifies a list of permitted groups for the file specified by &%file%&.
19724 The list is in addition to the local user's primary group when
19725 &%check_local_user%& is set. See &%check_group%& above.
19728 .option pipe_transport redirect string&!! unset
19729 .vindex "&$address_pipe$&"
19730 A &(redirect)& router sets up a direct delivery to a pipe when a string
19731 starting with a vertical bar character is specified as a new &"address"&. The
19732 transport used is specified by this option, which, after expansion, must be the
19733 name of a configured transport. This should normally be a &(pipe)& transport.
19734 When the transport is run, the pipe command is in &$address_pipe$&.
19737 .option qualify_domain redirect string&!! unset
19738 .vindex "&$qualify_recipient$&"
19739 If this option is set, and an unqualified address (one without a domain) is
19740 generated, and that address would normally be qualified by the global setting
19741 in &%qualify_recipient%&, it is instead qualified with the domain specified by
19742 expanding this string. If the expansion fails, the router declines. If you want
19743 to revert to the default, you can have the expansion generate
19744 &$qualify_recipient$&.
19746 This option applies to all unqualified addresses generated by Exim filters,
19747 but for traditional &_.forward_& files, it applies only to addresses that are
19748 not preceded by a backslash. Sieve filters cannot generate unqualified
19751 .option qualify_preserve_domain redirect boolean false
19752 .cindex "domain" "in redirection; preserving"
19753 .cindex "preserving domain in redirection"
19754 .cindex "address redirection" "domain; preserving"
19755 If this option is set, the router's local &%qualify_domain%& option must not be
19756 set (a configuration error occurs if it is). If an unqualified address (one
19757 without a domain) is generated, it is qualified with the domain of the parent
19758 address (the immediately preceding ancestor) instead of the global
19759 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
19760 this applies whether or not the address is preceded by a backslash.
19763 .option repeat_use redirect boolean true
19764 If this option is set false, the router is skipped for a child address that has
19765 any ancestor that was routed by this router. This test happens before any of
19766 the other preconditions are tested. Exim's default anti-looping rules skip
19767 only when the ancestor is the same as the current address. See also
19768 &%check_ancestor%& above and the generic &%redirect_router%& option.
19771 .option reply_transport redirect string&!! unset
19772 A &(redirect)& router sets up an automatic reply when a &%mail%& or
19773 &%vacation%& command is used in a filter file. The transport used is specified
19774 by this option, which, after expansion, must be the name of a configured
19775 transport. This should normally be an &(autoreply)& transport. Other transports
19776 are unlikely to do anything sensible or useful.
19779 .option rewrite redirect boolean true
19780 .cindex "address redirection" "disabling rewriting"
19781 If this option is set false, addresses generated by the router are not
19782 subject to address rewriting. Otherwise, they are treated like new addresses
19783 and are rewritten according to the global rewriting rules.
19786 .option sieve_subaddress redirect string&!! unset
19787 The value of this option is passed to a Sieve filter to specify the
19788 :subaddress part of an address.
19790 .option sieve_useraddress redirect string&!! unset
19791 The value of this option is passed to a Sieve filter to specify the :user part
19792 of an address. However, if it is unset, the entire original local part
19793 (including any prefix or suffix) is used for :user.
19796 .option sieve_vacation_directory redirect string&!! unset
19797 .cindex "Sieve filter" "vacation directory"
19798 To enable the &"vacation"& extension for Sieve filters, you must set
19799 &%sieve_vacation_directory%& to the directory where vacation databases are held
19800 (do not put anything else in that directory), and ensure that the
19801 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
19802 needs their own directory; Exim will create it if necessary.
19806 .option skip_syntax_errors redirect boolean false
19807 .cindex "forward file" "broken"
19808 .cindex "address redirection" "broken files"
19809 .cindex "alias file" "broken"
19810 .cindex "broken alias or forward files"
19811 .cindex "ignoring faulty addresses"
19812 .cindex "skipping faulty addresses"
19813 .cindex "error" "skipping bad syntax"
19814 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
19815 non-filter redirection data are skipped, and each failing address is logged. If
19816 &%syntax_errors_to%& is set, a message is sent to the address it defines,
19817 giving details of the failures. If &%syntax_errors_text%& is set, its contents
19818 are expanded and placed at the head of the error message generated by
19819 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
19820 be the same address as the generic &%errors_to%& option. The
19821 &%skip_syntax_errors%& option is often used when handling mailing lists.
19823 If all the addresses in a redirection list are skipped because of syntax
19824 errors, the router declines to handle the original address, and it is passed to
19825 the following routers.
19827 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
19828 error in the filter causes filtering to be abandoned without any action being
19829 taken. The incident is logged, and the router declines to handle the address,
19830 so it is passed to the following routers.
19832 .cindex "Sieve filter" "syntax errors in"
19833 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
19834 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
19835 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
19837 &%skip_syntax_errors%& can be used to specify that errors in users' forward
19838 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
19839 option, used with an address that does not get redirected, can be used to
19840 notify users of these errors, by means of a router like this:
19846 file = $home/.forward
19847 file_transport = address_file
19848 pipe_transport = address_pipe
19849 reply_transport = address_reply
19852 syntax_errors_to = real-$local_part@$domain
19853 syntax_errors_text = \
19854 This is an automatically generated message. An error has\n\
19855 been found in your .forward file. Details of the error are\n\
19856 reported below. While this error persists, you will receive\n\
19857 a copy of this message for every message that is addressed\n\
19858 to you. If your .forward file is a filter file, or if it is\n\
19859 a non-filter file containing no valid forwarding addresses,\n\
19860 a copy of each incoming message will be put in your normal\n\
19861 mailbox. If a non-filter file contains at least one valid\n\
19862 forwarding address, forwarding to the valid addresses will\n\
19863 happen, and those will be the only deliveries that occur.
19865 You also need a router to ensure that local addresses that are prefixed by
19866 &`real-`& are recognized, but not forwarded or filtered. For example, you could
19867 put this immediately before the &(userforward)& router:
19872 local_part_prefix = real-
19873 transport = local_delivery
19875 For security, it would probably be a good idea to restrict the use of this
19876 router to locally-generated messages, using a condition such as this:
19878 condition = ${if match {$sender_host_address}\
19879 {\N^(|127\.0\.0\.1)$\N}}
19883 .option syntax_errors_text redirect string&!! unset
19884 See &%skip_syntax_errors%& above.
19887 .option syntax_errors_to redirect string unset
19888 See &%skip_syntax_errors%& above.
19889 .ecindex IIDredrou1
19890 .ecindex IIDredrou2
19897 . ////////////////////////////////////////////////////////////////////////////
19898 . ////////////////////////////////////////////////////////////////////////////
19900 .chapter "Environment for running local transports" "CHAPenvironment" &&&
19901 "Environment for local transports"
19902 .scindex IIDenvlotra1 "local transports" "environment for"
19903 .scindex IIDenvlotra2 "environment for local transports"
19904 .scindex IIDenvlotra3 "transport" "local; environment for"
19905 Local transports handle deliveries to files and pipes. (The &(autoreply)&
19906 transport can be thought of as similar to a pipe.) Exim always runs transports
19907 in subprocesses, under specified uids and gids. Typical deliveries to local
19908 mailboxes run under the uid and gid of the local user.
19910 Exim also sets a specific current directory while running the transport; for
19911 some transports a home directory setting is also relevant. The &(pipe)&
19912 transport is the only one that sets up environment variables; see section
19913 &<<SECTpipeenv>>& for details.
19915 The values used for the uid, gid, and the directories may come from several
19916 different places. In many cases, the router that handles the address associates
19917 settings with that address as a result of its &%check_local_user%&, &%group%&,
19918 or &%user%& options. However, values may also be given in the transport's own
19919 configuration, and these override anything that comes from the router.
19923 .section "Concurrent deliveries" "SECID131"
19924 .cindex "concurrent deliveries"
19925 .cindex "simultaneous deliveries"
19926 If two different messages for the same local recipient arrive more or less
19927 simultaneously, the two delivery processes are likely to run concurrently. When
19928 the &(appendfile)& transport is used to write to a file, Exim applies locking
19929 rules to stop concurrent processes from writing to the same file at the same
19932 However, when you use a &(pipe)& transport, it is up to you to arrange any
19933 locking that is needed. Here is a silly example:
19937 command = /bin/sh -c 'cat >>/some/file'
19939 This is supposed to write the message at the end of the file. However, if two
19940 messages arrive at the same time, the file will be scrambled. You can use the
19941 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
19942 file using the same algorithm that Exim itself uses.
19947 .section "Uids and gids" "SECTenvuidgid"
19948 .cindex "local transports" "uid and gid"
19949 .cindex "transport" "local; uid and gid"
19950 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
19951 overrides any group that the router set in the address, even if &%user%& is not
19952 set for the transport. This makes it possible, for example, to run local mail
19953 delivery under the uid of the recipient (set by the router), but in a special
19954 group (set by the transport). For example:
19957 # User/group are set by check_local_user in this router
19961 transport = group_delivery
19964 # This transport overrides the group
19966 driver = appendfile
19967 file = /var/spool/mail/$local_part
19970 If &%user%& is set for a transport, its value overrides what is set in the
19971 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
19972 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
19975 .oindex "&%initgroups%&"
19976 When the uid is taken from the transport's configuration, the &[initgroups()]&
19977 function is called for the groups associated with that uid if the
19978 &%initgroups%& option is set for the transport. When the uid is not specified
19979 by the transport, but is associated with the address by a router, the option
19980 for calling &[initgroups()]& is taken from the router configuration.
19982 .cindex "&(pipe)& transport" "uid for"
19983 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
19984 is set and &%user%& is not set, the uid of the process that called Exim to
19985 receive the message is used, and if &%group%& is not set, the corresponding
19986 original gid is also used.
19988 This is the detailed preference order for obtaining a gid; the first of the
19989 following that is set is used:
19992 A &%group%& setting of the transport;
19994 A &%group%& setting of the router;
19996 A gid associated with a user setting of the router, either as a result of
19997 &%check_local_user%& or an explicit non-numeric &%user%& setting;
19999 The group associated with a non-numeric &%user%& setting of the transport;
20001 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
20002 the uid is the creator's uid;
20004 The Exim gid if the Exim uid is being used as a default.
20007 If, for example, the user is specified numerically on the router and there are
20008 no group settings, no gid is available. In this situation, an error occurs.
20009 This is different for the uid, for which there always is an ultimate default.
20010 The first of the following that is set is used:
20013 A &%user%& setting of the transport;
20015 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
20017 A &%user%& setting of the router;
20019 A &%check_local_user%& setting of the router;
20024 Of course, an error will still occur if the uid that is chosen is on the
20025 &%never_users%& list.
20031 .section "Current and home directories" "SECID132"
20032 .cindex "current directory for local transport"
20033 .cindex "home directory" "for local transport"
20034 .cindex "transport" "local; home directory for"
20035 .cindex "transport" "local; current directory for"
20036 Routers may set current and home directories for local transports by means of
20037 the &%transport_current_directory%& and &%transport_home_directory%& options.
20038 However, if the transport's &%current_directory%& or &%home_directory%& options
20039 are set, they override the router's values. In detail, the home directory
20040 for a local transport is taken from the first of these values that is set:
20043 The &%home_directory%& option on the transport;
20045 The &%transport_home_directory%& option on the router;
20047 The password data if &%check_local_user%& is set on the router;
20049 The &%router_home_directory%& option on the router.
20052 The current directory is taken from the first of these values that is set:
20055 The &%current_directory%& option on the transport;
20057 The &%transport_current_directory%& option on the router.
20061 If neither the router nor the transport sets a current directory, Exim uses the
20062 value of the home directory, if it is set. Otherwise it sets the current
20063 directory to &_/_& before running a local transport.
20067 .section "Expansion variables derived from the address" "SECID133"
20068 .vindex "&$domain$&"
20069 .vindex "&$local_part$&"
20070 .vindex "&$original_domain$&"
20071 Normally a local delivery is handling a single address, and in that case the
20072 variables such as &$domain$& and &$local_part$& are set during local
20073 deliveries. However, in some circumstances more than one address may be handled
20074 at once (for example, while writing batch SMTP for onward transmission by some
20075 other means). In this case, the variables associated with the local part are
20076 never set, &$domain$& is set only if all the addresses have the same domain,
20077 and &$original_domain$& is never set.
20078 .ecindex IIDenvlotra1
20079 .ecindex IIDenvlotra2
20080 .ecindex IIDenvlotra3
20088 . ////////////////////////////////////////////////////////////////////////////
20089 . ////////////////////////////////////////////////////////////////////////////
20091 .chapter "Generic options for transports" "CHAPtransportgeneric"
20092 .scindex IIDgenoptra1 "generic options" "transport"
20093 .scindex IIDgenoptra2 "options" "generic; for transports"
20094 .scindex IIDgenoptra3 "transport" "generic options for"
20095 The following generic options apply to all transports:
20098 .option body_only transports boolean false
20099 .cindex "transport" "body only"
20100 .cindex "message" "transporting body only"
20101 .cindex "body of message" "transporting"
20102 If this option is set, the message's headers are not transported. It is
20103 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
20104 or &(pipe)& transports, the settings of &%message_prefix%& and
20105 &%message_suffix%& should be checked, because this option does not
20106 automatically suppress them.
20109 .option current_directory transports string&!! unset
20110 .cindex "transport" "current directory for"
20111 This specifies the current directory that is to be set while running the
20112 transport, overriding any value that may have been set by the router.
20113 If the expansion fails for any reason, including forced failure, an error is
20114 logged, and delivery is deferred.
20117 .option disable_logging transports boolean false
20118 If this option is set true, nothing is logged for any
20119 deliveries by the transport or for any
20120 transport errors. You should not set this option unless you really, really know
20121 what you are doing.
20124 .option debug_print transports string&!! unset
20125 .cindex "testing" "variables in drivers"
20126 If this option is set and debugging is enabled (see the &%-d%& command line
20127 option), the string is expanded and included in the debugging output when the
20129 If expansion of the string fails, the error message is written to the debugging
20130 output, and Exim carries on processing.
20131 This facility is provided to help with checking out the values of variables and
20132 so on when debugging driver configurations. For example, if a &%headers_add%&
20133 option is not working properly, &%debug_print%& could be used to output the
20134 variables it references. A newline is added to the text if it does not end with
20136 The variables &$transport_name$& and &$router_name$& contain the name of the
20137 transport and the router that called it.
20139 .option delivery_date_add transports boolean false
20140 .cindex "&'Delivery-date:'& header line"
20141 If this option is true, a &'Delivery-date:'& header is added to the message.
20142 This gives the actual time the delivery was made. As this is not a standard
20143 header, Exim has a configuration option (&%delivery_date_remove%&) which
20144 requests its removal from incoming messages, so that delivered messages can
20145 safely be resent to other recipients.
20148 .option driver transports string unset
20149 This specifies which of the available transport drivers is to be used.
20150 There is no default, and this option must be set for every transport.
20153 .option envelope_to_add transports boolean false
20154 .cindex "&'Envelope-to:'& header line"
20155 If this option is true, an &'Envelope-to:'& header is added to the message.
20156 This gives the original address(es) in the incoming envelope that caused this
20157 delivery to happen. More than one address may be present if the transport is
20158 configured to handle several addresses at once, or if more than one original
20159 address was redirected to the same final address. As this is not a standard
20160 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
20161 its removal from incoming messages, so that delivered messages can safely be
20162 resent to other recipients.
20165 .option group transports string&!! "Exim group"
20166 .cindex "transport" "group; specifying"
20167 This option specifies a gid for running the transport process, overriding any
20168 value that the router supplies, and also overriding any value associated with
20169 &%user%& (see below).
20172 .option headers_add transports list&!! unset
20173 .cindex "header lines" "adding in transport"
20174 .cindex "transport" "header lines; adding"
20175 This option specifies a list of text headers, newline-separated,
20176 which are (separately) expanded and added to the header
20177 portion of a message as it is transported, as described in section
20178 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
20179 routers. If the result of the expansion is an empty string, or if the expansion
20180 is forced to fail, no action is taken. Other expansion failures are treated as
20181 errors and cause the delivery to be deferred.
20183 Unlike most options, &%headers_add%& can be specified multiple times
20184 for a transport; all listed headers are added.
20187 .option headers_only transports boolean false
20188 .cindex "transport" "header lines only"
20189 .cindex "message" "transporting headers only"
20190 .cindex "header lines" "transporting"
20191 If this option is set, the message's body is not transported. It is mutually
20192 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
20193 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
20194 checked, since this option does not automatically suppress them.
20197 .option headers_remove transports list&!! unset
20198 .cindex "header lines" "removing"
20199 .cindex "transport" "header lines; removing"
20200 This option specifies a list of header names, colon-separated;
20201 these headers are omitted from the message as it is transported, as described
20202 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
20204 Each list item is separately expanded.
20205 If the result of the expansion is an empty string, or if the expansion
20206 is forced to fail, no action is taken. Other expansion failures are treated as
20207 errors and cause the delivery to be deferred.
20209 Unlike most options, &%headers_remove%& can be specified multiple times
20210 for a router; all listed headers are removed.
20214 .option headers_rewrite transports string unset
20215 .cindex "transport" "header lines; rewriting"
20216 .cindex "rewriting" "at transport time"
20217 This option allows addresses in header lines to be rewritten at transport time,
20218 that is, as the message is being copied to its destination. The contents of the
20219 option are a colon-separated list of rewriting rules. Each rule is in exactly
20220 the same form as one of the general rewriting rules that are applied when a
20221 message is received. These are described in chapter &<<CHAPrewrite>>&. For
20224 headers_rewrite = a@b c@d f : \
20227 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
20228 &'w@z'& in all address-bearing header lines. The rules are applied to the
20229 header lines just before they are written out at transport time, so they affect
20230 only those copies of the message that pass through the transport. However, only
20231 the message's original header lines, and any that were added by a system
20232 filter, are rewritten. If a router or transport adds header lines, they are not
20233 affected by this option. These rewriting rules are &'not'& applied to the
20234 envelope. You can change the return path using &%return_path%&, but you cannot
20235 change envelope recipients at this time.
20238 .option home_directory transports string&!! unset
20239 .cindex "transport" "home directory for"
20241 This option specifies a home directory setting for a local transport,
20242 overriding any value that may be set by the router. The home directory is
20243 placed in &$home$& while expanding the transport's private options. It is also
20244 used as the current directory if no current directory is set by the
20245 &%current_directory%& option on the transport or the
20246 &%transport_current_directory%& option on the router. If the expansion fails
20247 for any reason, including forced failure, an error is logged, and delivery is
20251 .option initgroups transports boolean false
20252 .cindex "additional groups"
20253 .cindex "groups" "additional"
20254 .cindex "transport" "group; additional"
20255 If this option is true and the uid for the delivery process is provided by the
20256 transport, the &[initgroups()]& function is called when running the transport
20257 to ensure that any additional groups associated with the uid are set up.
20260 .option message_size_limit transports string&!! 0
20261 .cindex "limit" "message size per transport"
20262 .cindex "size" "of message, limit"
20263 .cindex "transport" "message size; limiting"
20264 This option controls the size of messages passed through the transport. It is
20265 expanded before use; the result of the expansion must be a sequence of decimal
20266 digits, optionally followed by K or M. If the expansion fails for any reason,
20267 including forced failure, or if the result is not of the required form,
20268 delivery is deferred. If the value is greater than zero and the size of a
20269 message exceeds this limit, the address is failed. If there is any chance that
20270 the resulting bounce message could be routed to the same transport, you should
20271 ensure that &%return_size_limit%& is less than the transport's
20272 &%message_size_limit%&, as otherwise the bounce message will fail to get
20277 .option rcpt_include_affixes transports boolean false
20278 .cindex "prefix" "for local part, including in envelope"
20279 .cindex "suffix for local part" "including in envelope"
20280 .cindex "local part" "prefix"
20281 .cindex "local part" "suffix"
20282 When this option is false (the default), and an address that has had any
20283 affixes (prefixes or suffixes) removed from the local part is delivered by any
20284 form of SMTP or LMTP, the affixes are not included. For example, if a router
20287 local_part_prefix = *-
20289 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
20292 RCPT TO:<xyz@some.domain>
20294 This is also the case when an ACL-time callout is being used to verify a
20295 recipient address. However, if &%rcpt_include_affixes%& is set true, the
20296 whole local part is included in the RCPT command. This option applies to BSMTP
20297 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
20298 &(lmtp)& and &(smtp)& transports.
20301 .option retry_use_local_part transports boolean "see below"
20302 .cindex "hints database" "retry keys"
20303 When a delivery suffers a temporary failure, a retry record is created
20304 in Exim's hints database. For remote deliveries, the key for the retry record
20305 is based on the name and/or IP address of the failing remote host. For local
20306 deliveries, the key is normally the entire address, including both the local
20307 part and the domain. This is suitable for most common cases of local delivery
20308 temporary failure &-- for example, exceeding a mailbox quota should delay only
20309 deliveries to that mailbox, not to the whole domain.
20311 However, in some special cases you may want to treat a temporary local delivery
20312 as a failure associated with the domain, and not with a particular local part.
20313 (For example, if you are storing all mail for some domain in files.) You can do
20314 this by setting &%retry_use_local_part%& false.
20316 For all the local transports, its default value is true. For remote transports,
20317 the default value is false for tidiness, but changing the value has no effect
20318 on a remote transport in the current implementation.
20321 .option return_path transports string&!! unset
20322 .cindex "envelope sender"
20323 .cindex "transport" "return path; changing"
20324 .cindex "return path" "changing in transport"
20325 If this option is set, the string is expanded at transport time and replaces
20326 the existing return path (envelope sender) value in the copy of the message
20327 that is being delivered. An empty return path is permitted. This feature is
20328 designed for remote deliveries, where the value of this option is used in the
20329 SMTP MAIL command. If you set &%return_path%& for a local transport, the
20330 only effect is to change the address that is placed in the &'Return-path:'&
20331 header line, if one is added to the message (see the next option).
20333 &*Note:*& A changed return path is not logged unless you add
20334 &%return_path_on_delivery%& to the log selector.
20336 .vindex "&$return_path$&"
20337 The expansion can refer to the existing value via &$return_path$&. This is
20338 either the message's envelope sender, or an address set by the
20339 &%errors_to%& option on a router. If the expansion is forced to fail, no
20340 replacement occurs; if it fails for another reason, delivery is deferred. This
20341 option can be used to support VERP (Variable Envelope Return Paths) &-- see
20342 section &<<SECTverp>>&.
20344 &*Note*&: If a delivery error is detected locally, including the case when a
20345 remote server rejects a message at SMTP time, the bounce message is not sent to
20346 the value of this option. It is sent to the previously set errors address.
20347 This defaults to the incoming sender address, but can be changed by setting
20348 &%errors_to%& in a router.
20352 .option return_path_add transports boolean false
20353 .cindex "&'Return-path:'& header line"
20354 If this option is true, a &'Return-path:'& header is added to the message.
20355 Although the return path is normally available in the prefix line of BSD
20356 mailboxes, this is commonly not displayed by MUAs, and so the user does not
20357 have easy access to it.
20359 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
20360 the delivery SMTP server makes the final delivery"&. This implies that this
20361 header should not be present in incoming messages. Exim has a configuration
20362 option, &%return_path_remove%&, which requests removal of this header from
20363 incoming messages, so that delivered messages can safely be resent to other
20367 .option shadow_condition transports string&!! unset
20368 See &%shadow_transport%& below.
20371 .option shadow_transport transports string unset
20372 .cindex "shadow transport"
20373 .cindex "transport" "shadow"
20374 A local transport may set the &%shadow_transport%& option to the name of
20375 another local transport. Shadow remote transports are not supported.
20377 Whenever a delivery to the main transport succeeds, and either
20378 &%shadow_condition%& is unset, or its expansion does not result in the empty
20379 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
20380 passed to the shadow transport, with the same delivery address or addresses. If
20381 expansion fails, no action is taken except that non-forced expansion failures
20382 cause a log line to be written.
20384 The result of the shadow transport is discarded and does not affect the
20385 subsequent processing of the message. Only a single level of shadowing is
20386 provided; the &%shadow_transport%& option is ignored on any transport when it
20387 is running as a shadow. Options concerned with output from pipes are also
20388 ignored. The log line for the successful delivery has an item added on the end,
20391 ST=<shadow transport name>
20393 If the shadow transport did not succeed, the error message is put in
20394 parentheses afterwards. Shadow transports can be used for a number of different
20395 purposes, including keeping more detailed log information than Exim normally
20396 provides, and implementing automatic acknowledgment policies based on message
20397 headers that some sites insist on.
20400 .option transport_filter transports string&!! unset
20401 .cindex "transport" "filter"
20402 .cindex "filter" "transport filter"
20403 This option sets up a filtering (in the Unix shell sense) process for messages
20404 at transport time. It should not be confused with mail filtering as set up by
20405 individual users or via a system filter.
20407 When the message is about to be written out, the command specified by
20408 &%transport_filter%& is started up in a separate, parallel process, and
20409 the entire message, including the header lines, is passed to it on its standard
20410 input (this in fact is done from a third process, to avoid deadlock). The
20411 command must be specified as an absolute path.
20413 The lines of the message that are written to the transport filter are
20414 terminated by newline (&"\n"&). The message is passed to the filter before any
20415 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
20416 lines beginning with a dot, and also before any processing implied by the
20417 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
20418 &(pipe)& transports.
20420 The standard error for the filter process is set to the same destination as its
20421 standard output; this is read and written to the message's ultimate
20422 destination. The process that writes the message to the filter, the
20423 filter itself, and the original process that reads the result and delivers it
20424 are all run in parallel, like a shell pipeline.
20426 The filter can perform any transformations it likes, but of course should take
20427 care not to break RFC 2822 syntax. Exim does not check the result, except to
20428 test for a final newline when SMTP is in use. All messages transmitted over
20429 SMTP must end with a newline, so Exim supplies one if it is missing.
20431 .cindex "content scanning" "per user"
20432 A transport filter can be used to provide content-scanning on a per-user basis
20433 at delivery time if the only required effect of the scan is to modify the
20434 message. For example, a content scan could insert a new header line containing
20435 a spam score. This could be interpreted by a filter in the user's MUA. It is
20436 not possible to discard a message at this stage.
20438 .cindex "SMTP" "SIZE"
20439 A problem might arise if the filter increases the size of a message that is
20440 being sent down an SMTP connection. If the receiving SMTP server has indicated
20441 support for the SIZE parameter, Exim will have sent the size of the message
20442 at the start of the SMTP session. If what is actually sent is substantially
20443 more, the server might reject the message. This can be worked round by setting
20444 the &%size_addition%& option on the &(smtp)& transport, either to allow for
20445 additions to the message, or to disable the use of SIZE altogether.
20447 .vindex "&$pipe_addresses$&"
20448 The value of the &%transport_filter%& option is the command string for starting
20449 the filter, which is run directly from Exim, not under a shell. The string is
20450 parsed by Exim in the same way as a command string for the &(pipe)& transport:
20451 Exim breaks it up into arguments and then expands each argument separately (see
20452 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
20453 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
20454 of arguments, one for each address that applies to this delivery. (This isn't
20455 an ideal name for this feature here, but as it was already implemented for the
20456 &(pipe)& transport, it seemed sensible not to change it.)
20459 .vindex "&$host_address$&"
20460 The expansion variables &$host$& and &$host_address$& are available when the
20461 transport is a remote one. They contain the name and IP address of the host to
20462 which the message is being sent. For example:
20464 transport_filter = /some/directory/transport-filter.pl \
20465 $host $host_address $sender_address $pipe_addresses
20468 Two problems arise if you want to use more complicated expansion items to
20469 generate transport filter commands, both of which due to the fact that the
20470 command is split up &'before'& expansion.
20472 If an expansion item contains white space, you must quote it, so that it is all
20473 part of the same command item. If the entire option setting is one such
20474 expansion item, you have to take care what kind of quoting you use. For
20477 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
20479 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
20480 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
20481 stripped by Exim when it read the option's value. When the value is used, if
20482 the single quotes were missing, the line would be split into two items,
20483 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
20484 Exim tried to expand the first one.
20486 Except for the special case of &$pipe_addresses$& that is mentioned above, an
20487 expansion cannot generate multiple arguments, or a command name followed by
20488 arguments. Consider this example:
20490 transport_filter = ${lookup{$host}lsearch{/a/file}\
20491 {$value}{/bin/cat}}
20493 The result of the lookup is interpreted as the name of the command, even
20494 if it contains white space. The simplest way round this is to use a shell:
20496 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
20497 {$value}{/bin/cat}}
20501 The filter process is run under the same uid and gid as the normal delivery.
20502 For remote deliveries this is the Exim uid/gid by default. The command should
20503 normally yield a zero return code. Transport filters are not supposed to fail.
20504 A non-zero code is taken to mean that the transport filter encountered some
20505 serious problem. Delivery of the message is deferred; the message remains on
20506 the queue and is tried again later. It is not possible to cause a message to be
20507 bounced from a transport filter.
20509 If a transport filter is set on an autoreply transport, the original message is
20510 passed through the filter as it is being copied into the newly generated
20511 message, which happens if the &%return_message%& option is set.
20514 .option transport_filter_timeout transports time 5m
20515 .cindex "transport" "filter, timeout"
20516 When Exim is reading the output of a transport filter, it applies a timeout
20517 that can be set by this option. Exceeding the timeout is normally treated as a
20518 temporary delivery failure. However, if a transport filter is used with a
20519 &(pipe)& transport, a timeout in the transport filter is treated in the same
20520 way as a timeout in the pipe command itself. By default, a timeout is a hard
20521 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
20522 becomes a temporary error.
20525 .option user transports string&!! "Exim user"
20526 .cindex "uid (user id)" "local delivery"
20527 .cindex "transport" "user, specifying"
20528 This option specifies the user under whose uid the delivery process is to be
20529 run, overriding any uid that may have been set by the router. If the user is
20530 given as a name, the uid is looked up from the password data, and the
20531 associated group is taken as the value of the gid to be used if the &%group%&
20534 For deliveries that use local transports, a user and group are normally
20535 specified explicitly or implicitly (for example, as a result of
20536 &%check_local_user%&) by the router or transport.
20538 .cindex "hints database" "access by remote transport"
20539 For remote transports, you should leave this option unset unless you really are
20540 sure you know what you are doing. When a remote transport is running, it needs
20541 to be able to access Exim's hints databases, because each host may have its own
20543 .ecindex IIDgenoptra1
20544 .ecindex IIDgenoptra2
20545 .ecindex IIDgenoptra3
20552 . ////////////////////////////////////////////////////////////////////////////
20553 . ////////////////////////////////////////////////////////////////////////////
20555 .chapter "Address batching in local transports" "CHAPbatching" &&&
20557 .cindex "transport" "local; address batching in"
20558 The only remote transport (&(smtp)&) is normally configured to handle more than
20559 one address at a time, so that when several addresses are routed to the same
20560 remote host, just one copy of the message is sent. Local transports, however,
20561 normally handle one address at a time. That is, a separate instance of the
20562 transport is run for each address that is routed to the transport. A separate
20563 copy of the message is delivered each time.
20565 .cindex "batched local delivery"
20566 .oindex "&%batch_max%&"
20567 .oindex "&%batch_id%&"
20568 In special cases, it may be desirable to handle several addresses at once in a
20569 local transport, for example:
20572 In an &(appendfile)& transport, when storing messages in files for later
20573 delivery by some other means, a single copy of the message with multiple
20574 recipients saves space.
20576 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
20577 a single copy saves time, and is the normal way LMTP is expected to work.
20579 In a &(pipe)& transport, when passing the message
20580 to a scanner program or
20581 to some other delivery mechanism such as UUCP, multiple recipients may be
20585 These three local transports all have the same options for controlling multiple
20586 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
20587 repeating the information for each transport, these options are described here.
20589 The &%batch_max%& option specifies the maximum number of addresses that can be
20590 delivered together in a single run of the transport. Its default value is one
20591 (no batching). When more than one address is routed to a transport that has a
20592 &%batch_max%& value greater than one, the addresses are delivered in a batch
20593 (that is, in a single run of the transport with multiple recipients), subject
20594 to certain conditions:
20597 .vindex "&$local_part$&"
20598 If any of the transport's options contain a reference to &$local_part$&, no
20599 batching is possible.
20601 .vindex "&$domain$&"
20602 If any of the transport's options contain a reference to &$domain$&, only
20603 addresses with the same domain are batched.
20605 .cindex "customizing" "batching condition"
20606 If &%batch_id%& is set, it is expanded for each address, and only those
20607 addresses with the same expanded value are batched. This allows you to specify
20608 customized batching conditions. Failure of the expansion for any reason,
20609 including forced failure, disables batching, but it does not stop the delivery
20612 Batched addresses must also have the same errors address (where to send
20613 delivery errors), the same header additions and removals, the same user and
20614 group for the transport, and if a host list is present, the first host must
20618 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
20619 both when the file or pipe command is specified in the transport, and when it
20620 is specified by a &(redirect)& router, but all the batched addresses must of
20621 course be routed to the same file or pipe command. These two transports have an
20622 option called &%use_bsmtp%&, which causes them to deliver the message in
20623 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
20624 &%check_string%& and &%escape_string%& options are forced to the values
20627 escape_string = ".."
20629 when batched SMTP is in use. A full description of the batch SMTP mechanism is
20630 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
20631 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
20633 .cindex "&'Envelope-to:'& header line"
20634 If the generic &%envelope_to_add%& option is set for a batching transport, the
20635 &'Envelope-to:'& header that is added to the message contains all the addresses
20636 that are being processed together. If you are using a batching &(appendfile)&
20637 transport without &%use_bsmtp%&, the only way to preserve the recipient
20638 addresses is to set the &%envelope_to_add%& option.
20640 .cindex "&(pipe)& transport" "with multiple addresses"
20641 .vindex "&$pipe_addresses$&"
20642 If you are using a &(pipe)& transport without BSMTP, and setting the
20643 transport's &%command%& option, you can include &$pipe_addresses$& as part of
20644 the command. This is not a true variable; it is a bit of magic that causes each
20645 of the recipient addresses to be inserted into the command as a separate
20646 argument. This provides a way of accessing all the addresses that are being
20647 delivered in the batch. &*Note:*& This is not possible for pipe commands that
20648 are specified by a &(redirect)& router.
20653 . ////////////////////////////////////////////////////////////////////////////
20654 . ////////////////////////////////////////////////////////////////////////////
20656 .chapter "The appendfile transport" "CHAPappendfile"
20657 .scindex IIDapptra1 "&(appendfile)& transport"
20658 .scindex IIDapptra2 "transports" "&(appendfile)&"
20659 .cindex "directory creation"
20660 .cindex "creating directories"
20661 The &(appendfile)& transport delivers a message by appending it to an existing
20662 file, or by creating an entirely new file in a specified directory. Single
20663 files to which messages are appended can be in the traditional Unix mailbox
20664 format, or optionally in the MBX format supported by the Pine MUA and
20665 University of Washington IMAP daemon, &'inter alia'&. When each message is
20666 being delivered as a separate file, &"maildir"& format can optionally be used
20667 to give added protection against failures that happen part-way through the
20668 delivery. A third form of separate-file delivery known as &"mailstore"& is also
20669 supported. For all file formats, Exim attempts to create as many levels of
20670 directory as necessary, provided that &%create_directory%& is set.
20672 The code for the optional formats is not included in the Exim binary by
20673 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
20674 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
20677 .cindex "quota" "system"
20678 Exim recognizes system quota errors, and generates an appropriate message. Exim
20679 also supports its own quota control within the transport, for use when the
20680 system facility is unavailable or cannot be used for some reason.
20682 If there is an error while appending to a file (for example, quota exceeded or
20683 partition filled), Exim attempts to reset the file's length and last
20684 modification time back to what they were before. If there is an error while
20685 creating an entirely new file, the new file is removed.
20687 Before appending to a file, a number of security checks are made, and the
20688 file is locked. A detailed description is given below, after the list of
20691 The &(appendfile)& transport is most commonly used for local deliveries to
20692 users' mailboxes. However, it can also be used as a pseudo-remote transport for
20693 putting messages into files for remote delivery by some means other than Exim.
20694 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
20699 .section "The file and directory options" "SECTfildiropt"
20700 The &%file%& option specifies a single file, to which the message is appended;
20701 the &%directory%& option specifies a directory, in which a new file containing
20702 the message is created. Only one of these two options can be set, and for
20703 normal deliveries to mailboxes, one of them &'must'& be set.
20705 .vindex "&$address_file$&"
20706 .vindex "&$local_part$&"
20707 However, &(appendfile)& is also used for delivering messages to files or
20708 directories whose names (or parts of names) are obtained from alias,
20709 forwarding, or filtering operations (for example, a &%save%& command in a
20710 user's Exim filter). When such a transport is running, &$local_part$& contains
20711 the local part that was aliased or forwarded, and &$address_file$& contains the
20712 name (or partial name) of the file or directory generated by the redirection
20713 operation. There are two cases:
20716 If neither &%file%& nor &%directory%& is set, the redirection operation
20717 must specify an absolute path (one that begins with &`/`&). This is the most
20718 common case when users with local accounts use filtering to sort mail into
20719 different folders. See for example, the &(address_file)& transport in the
20720 default configuration. If the path ends with a slash, it is assumed to be the
20721 name of a directory. A delivery to a directory can also be forced by setting
20722 &%maildir_format%& or &%mailstore_format%&.
20724 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
20725 used to determine the file or directory name for the delivery. Normally, the
20726 contents of &$address_file$& are used in some way in the string expansion.
20730 .cindex "Sieve filter" "configuring &(appendfile)&"
20731 .cindex "Sieve filter" "relative mailbox path handling"
20732 As an example of the second case, consider an environment where users do not
20733 have home directories. They may be permitted to use Exim filter commands of the
20738 or Sieve filter commands of the form:
20740 require "fileinto";
20741 fileinto "folder23";
20743 In this situation, the expansion of &%file%& or &%directory%& in the transport
20744 must transform the relative path into an appropriate absolute file name. In the
20745 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
20746 is used as a result of a &"keep"& action in the filter. This example shows one
20747 way of handling this requirement:
20749 file = ${if eq{$address_file}{inbox} \
20750 {/var/mail/$local_part} \
20751 {${if eq{${substr_0_1:$address_file}}{/} \
20753 {$home/mail/$address_file} \
20757 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
20758 location, absolute paths are used without change, and other folders are in the
20759 &_mail_& directory within the home directory.
20761 &*Note 1*&: While processing an Exim filter, a relative path such as
20762 &_folder23_& is turned into an absolute path if a home directory is known to
20763 the router. In particular, this is the case if &%check_local_user%& is set. If
20764 you want to prevent this happening at routing time, you can set
20765 &%router_home_directory%& empty. This forces the router to pass the relative
20766 path to the transport.
20768 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
20769 the &%file%& or &%directory%& option is still used if it is set.
20774 .section "Private options for appendfile" "SECID134"
20775 .cindex "options" "&(appendfile)& transport"
20779 .option allow_fifo appendfile boolean false
20780 .cindex "fifo (named pipe)"
20781 .cindex "named pipe (fifo)"
20782 .cindex "pipe" "named (fifo)"
20783 Setting this option permits delivery to named pipes (FIFOs) as well as to
20784 regular files. If no process is reading the named pipe at delivery time, the
20785 delivery is deferred.
20788 .option allow_symlink appendfile boolean false
20789 .cindex "symbolic link" "to mailbox"
20790 .cindex "mailbox" "symbolic link"
20791 By default, &(appendfile)& will not deliver if the path name for the file is
20792 that of a symbolic link. Setting this option relaxes that constraint, but there
20793 are security issues involved in the use of symbolic links. Be sure you know
20794 what you are doing if you set this. Details of exactly what this option affects
20795 are included in the discussion which follows this list of options.
20798 .option batch_id appendfile string&!! unset
20799 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
20800 However, batching is automatically disabled for &(appendfile)& deliveries that
20801 happen as a result of forwarding or aliasing or other redirection directly to a
20805 .option batch_max appendfile integer 1
20806 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
20809 .option check_group appendfile boolean false
20810 When this option is set, the group owner of the file defined by the &%file%&
20811 option is checked to see that it is the same as the group under which the
20812 delivery process is running. The default setting is false because the default
20813 file mode is 0600, which means that the group is irrelevant.
20816 .option check_owner appendfile boolean true
20817 When this option is set, the owner of the file defined by the &%file%& option
20818 is checked to ensure that it is the same as the user under which the delivery
20819 process is running.
20822 .option check_string appendfile string "see below"
20823 .cindex "&""From""& line"
20824 As &(appendfile)& writes the message, the start of each line is tested for
20825 matching &%check_string%&, and if it does, the initial matching characters are
20826 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
20827 a literal string, not a regular expression, and the case of any letters it
20828 contains is significant.
20830 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
20831 are forced to &"."& and &".."& respectively, and any settings in the
20832 configuration are ignored. Otherwise, they default to &"From&~"& and
20833 &">From&~"& when the &%file%& option is set, and unset when any of the
20834 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
20836 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
20837 suitable for traditional &"BSD"& mailboxes, where a line beginning with
20838 &"From&~"& indicates the start of a new message. All four options need changing
20839 if another format is used. For example, to deliver to mailboxes in MMDF format:
20840 .cindex "MMDF format mailbox"
20841 .cindex "mailbox" "MMDF format"
20843 check_string = "\1\1\1\1\n"
20844 escape_string = "\1\1\1\1 \n"
20845 message_prefix = "\1\1\1\1\n"
20846 message_suffix = "\1\1\1\1\n"
20848 .option create_directory appendfile boolean true
20849 .cindex "directory creation"
20850 When this option is true, Exim attempts to create any missing superior
20851 directories for the file that it is about to write. A created directory's mode
20852 is given by the &%directory_mode%& option.
20854 The group ownership of a newly created directory is highly dependent on the
20855 operating system (and possibly the file system) that is being used. For
20856 example, in Solaris, if the parent directory has the setgid bit set, its group
20857 is propagated to the child; if not, the currently set group is used. However,
20858 in FreeBSD, the parent's group is always used.
20862 .option create_file appendfile string anywhere
20863 This option constrains the location of files and directories that are created
20864 by this transport. It applies to files defined by the &%file%& option and
20865 directories defined by the &%directory%& option. In the case of maildir
20866 delivery, it applies to the top level directory, not the maildir directories
20869 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
20870 &"belowhome"&. In the second and third cases, a home directory must have been
20871 set for the transport. This option is not useful when an explicit file name is
20872 given for normal mailbox deliveries. It is intended for the case when file
20873 names are generated from users' &_.forward_& files. These are usually handled
20874 by an &(appendfile)& transport called &%address_file%&. See also
20875 &%file_must_exist%&.
20878 .option directory appendfile string&!! unset
20879 This option is mutually exclusive with the &%file%& option, but one of &%file%&
20880 or &%directory%& must be set, unless the delivery is the direct result of a
20881 redirection (see section &<<SECTfildiropt>>&).
20883 When &%directory%& is set, the string is expanded, and the message is delivered
20884 into a new file or files in or below the given directory, instead of being
20885 appended to a single mailbox file. A number of different formats are provided
20886 (see &%maildir_format%& and &%mailstore_format%&), and see section
20887 &<<SECTopdir>>& for further details of this form of delivery.
20890 .option directory_file appendfile string&!! "see below"
20892 .vindex "&$inode$&"
20893 When &%directory%& is set, but neither &%maildir_format%& nor
20894 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
20895 whose name is obtained by expanding this string. The default value is:
20897 q${base62:$tod_epoch}-$inode
20899 This generates a unique name from the current time, in base 62 form, and the
20900 inode of the file. The variable &$inode$& is available only when expanding this
20904 .option directory_mode appendfile "octal integer" 0700
20905 If &(appendfile)& creates any directories as a result of the
20906 &%create_directory%& option, their mode is specified by this option.
20909 .option escape_string appendfile string "see description"
20910 See &%check_string%& above.
20913 .option file appendfile string&!! unset
20914 This option is mutually exclusive with the &%directory%& option, but one of
20915 &%file%& or &%directory%& must be set, unless the delivery is the direct result
20916 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
20917 specifies a single file, to which the message is appended. One or more of
20918 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
20921 .cindex "NFS" "lock file"
20922 .cindex "locking files"
20923 .cindex "lock files"
20924 If you are using more than one host to deliver over NFS into the same
20925 mailboxes, you should always use lock files.
20927 The string value is expanded for each delivery, and must yield an absolute
20928 path. The most common settings of this option are variations on one of these
20931 file = /var/spool/mail/$local_part
20932 file = /home/$local_part/inbox
20935 .cindex "&""sticky""& bit"
20936 In the first example, all deliveries are done into the same directory. If Exim
20937 is configured to use lock files (see &%use_lockfile%& below) it must be able to
20938 create a file in the directory, so the &"sticky"& bit must be turned on for
20939 deliveries to be possible, or alternatively the &%group%& option can be used to
20940 run the delivery under a group id which has write access to the directory.
20944 .option file_format appendfile string unset
20945 .cindex "file" "mailbox; checking existing format"
20946 This option requests the transport to check the format of an existing file
20947 before adding to it. The check consists of matching a specific string at the
20948 start of the file. The value of the option consists of an even number of
20949 colon-separated strings. The first of each pair is the test string, and the
20950 second is the name of a transport. If the transport associated with a matched
20951 string is not the current transport, control is passed over to the other
20952 transport. For example, suppose the standard &(local_delivery)& transport has
20955 file_format = "From : local_delivery :\
20956 \1\1\1\1\n : local_mmdf_delivery"
20958 Mailboxes that begin with &"From"& are still handled by this transport, but if
20959 a mailbox begins with four binary ones followed by a newline, control is passed
20960 to a transport called &%local_mmdf_delivery%&, which presumably is configured
20961 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
20962 is assumed to match the current transport. If the start of a mailbox doesn't
20963 match any string, or if the transport named for a given string is not defined,
20964 delivery is deferred.
20967 .option file_must_exist appendfile boolean false
20968 If this option is true, the file specified by the &%file%& option must exist.
20969 A temporary error occurs if it does not, causing delivery to be deferred.
20970 If this option is false, the file is created if it does not exist.
20973 .option lock_fcntl_timeout appendfile time 0s
20974 .cindex "timeout" "mailbox locking"
20975 .cindex "mailbox" "locking, blocking and non-blocking"
20976 .cindex "locking files"
20977 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
20978 when locking an open mailbox file. If the call fails, the delivery process
20979 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
20980 Non-blocking calls are used so that the file is not kept open during the wait
20981 for the lock; the reason for this is to make it as safe as possible for
20982 deliveries over NFS in the case when processes might be accessing an NFS
20983 mailbox without using a lock file. This should not be done, but
20984 misunderstandings and hence misconfigurations are not unknown.
20986 On a busy system, however, the performance of a non-blocking lock approach is
20987 not as good as using a blocking lock with a timeout. In this case, the waiting
20988 is done inside the system call, and Exim's delivery process acquires the lock
20989 and can proceed as soon as the previous lock holder releases it.
20991 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
20992 timeout, are used. There may still be some retrying: the maximum number of
20995 (lock_retries * lock_interval) / lock_fcntl_timeout
20997 rounded up to the next whole number. In other words, the total time during
20998 which &(appendfile)& is trying to get a lock is roughly the same, unless
20999 &%lock_fcntl_timeout%& is set very large.
21001 You should consider setting this option if you are getting a lot of delayed
21002 local deliveries because of errors of the form
21004 failed to lock mailbox /some/file (fcntl)
21007 .option lock_flock_timeout appendfile time 0s
21008 This timeout applies to file locking when using &[flock()]& (see
21009 &%use_flock%&); the timeout operates in a similar manner to
21010 &%lock_fcntl_timeout%&.
21013 .option lock_interval appendfile time 3s
21014 This specifies the time to wait between attempts to lock the file. See below
21015 for details of locking.
21018 .option lock_retries appendfile integer 10
21019 This specifies the maximum number of attempts to lock the file. A value of zero
21020 is treated as 1. See below for details of locking.
21023 .option lockfile_mode appendfile "octal integer" 0600
21024 This specifies the mode of the created lock file, when a lock file is being
21025 used (see &%use_lockfile%& and &%use_mbx_lock%&).
21028 .option lockfile_timeout appendfile time 30m
21029 .cindex "timeout" "mailbox locking"
21030 When a lock file is being used (see &%use_lockfile%&), if a lock file already
21031 exists and is older than this value, it is assumed to have been left behind by
21032 accident, and Exim attempts to remove it.
21035 .option mailbox_filecount appendfile string&!! unset
21036 .cindex "mailbox" "specifying size of"
21037 .cindex "size" "of mailbox"
21038 If this option is set, it is expanded, and the result is taken as the current
21039 number of files in the mailbox. It must be a decimal number, optionally
21040 followed by K or M. This provides a way of obtaining this information from an
21041 external source that maintains the data.
21044 .option mailbox_size appendfile string&!! unset
21045 .cindex "mailbox" "specifying size of"
21046 .cindex "size" "of mailbox"
21047 If this option is set, it is expanded, and the result is taken as the current
21048 size the mailbox. It must be a decimal number, optionally followed by K or M.
21049 This provides a way of obtaining this information from an external source that
21050 maintains the data. This is likely to be helpful for maildir deliveries where
21051 it is computationally expensive to compute the size of a mailbox.
21055 .option maildir_format appendfile boolean false
21056 .cindex "maildir format" "specifying"
21057 If this option is set with the &%directory%& option, the delivery is into a new
21058 file, in the &"maildir"& format that is used by other mail software. When the
21059 transport is activated directly from a &(redirect)& router (for example, the
21060 &(address_file)& transport in the default configuration), setting
21061 &%maildir_format%& causes the path received from the router to be treated as a
21062 directory, whether or not it ends with &`/`&. This option is available only if
21063 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
21064 &<<SECTmaildirdelivery>>& below for further details.
21067 .option maildir_quota_directory_regex appendfile string "See below"
21068 .cindex "maildir format" "quota; directories included in"
21069 .cindex "quota" "maildir; directories included in"
21070 This option is relevant only when &%maildir_use_size_file%& is set. It defines
21071 a regular expression for specifying directories, relative to the quota
21072 directory (see &%quota_directory%&), that should be included in the quota
21073 calculation. The default value is:
21075 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
21077 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
21078 (directories whose names begin with a dot). If you want to exclude the
21080 folder from the count (as some sites do), you need to change this setting to
21082 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
21084 This uses a negative lookahead in the regular expression to exclude the
21085 directory whose name is &_.Trash_&. When a directory is excluded from quota
21086 calculations, quota processing is bypassed for any messages that are delivered
21087 directly into that directory.
21090 .option maildir_retries appendfile integer 10
21091 This option specifies the number of times to retry when writing a file in
21092 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
21095 .option maildir_tag appendfile string&!! unset
21096 This option applies only to deliveries in maildir format, and is described in
21097 section &<<SECTmaildirdelivery>>& below.
21100 .option maildir_use_size_file appendfile&!! boolean false
21101 .cindex "maildir format" "&_maildirsize_& file"
21102 The result of string expansion for this option must be a valid boolean value.
21103 If it is true, it enables support for &_maildirsize_& files. Exim
21104 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
21105 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
21106 value is zero. See &%maildir_quota_directory_regex%& above and section
21107 &<<SECTmaildirdelivery>>& below for further details.
21109 .option maildirfolder_create_regex appendfile string unset
21110 .cindex "maildir format" "&_maildirfolder_& file"
21111 .cindex "&_maildirfolder_&, creating"
21112 The value of this option is a regular expression. If it is unset, it has no
21113 effect. Otherwise, before a maildir delivery takes place, the pattern is
21114 matched against the name of the maildir directory, that is, the directory
21115 containing the &_new_& and &_tmp_& subdirectories that will be used for the
21116 delivery. If there is a match, Exim checks for the existence of a file called
21117 &_maildirfolder_& in the directory, and creates it if it does not exist.
21118 See section &<<SECTmaildirdelivery>>& for more details.
21121 .option mailstore_format appendfile boolean false
21122 .cindex "mailstore format" "specifying"
21123 If this option is set with the &%directory%& option, the delivery is into two
21124 new files in &"mailstore"& format. The option is available only if
21125 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
21126 below for further details.
21129 .option mailstore_prefix appendfile string&!! unset
21130 This option applies only to deliveries in mailstore format, and is described in
21131 section &<<SECTopdir>>& below.
21134 .option mailstore_suffix appendfile string&!! unset
21135 This option applies only to deliveries in mailstore format, and is described in
21136 section &<<SECTopdir>>& below.
21139 .option mbx_format appendfile boolean false
21140 .cindex "locking files"
21141 .cindex "file" "locking"
21142 .cindex "file" "MBX format"
21143 .cindex "MBX format, specifying"
21144 This option is available only if Exim has been compiled with SUPPORT_MBX
21145 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
21146 the message is appended to the mailbox file in MBX format instead of
21147 traditional Unix format. This format is supported by Pine4 and its associated
21148 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
21150 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
21151 automatically changed by the use of &%mbx_format%&. They should normally be set
21152 empty when using MBX format, so this option almost always appears in this
21159 If none of the locking options are mentioned in the configuration,
21160 &%use_mbx_lock%& is assumed and the other locking options default to false. It
21161 is possible to specify the other kinds of locking with &%mbx_format%&, but
21162 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
21163 interworks with &'c-client'&, providing for shared access to the mailbox. It
21164 should not be used if any program that does not use this form of locking is
21165 going to access the mailbox, nor should it be used if the mailbox file is NFS
21166 mounted, because it works only when the mailbox is accessed from a single host.
21168 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
21169 the standard version of &'c-client'&, because as long as it has a mailbox open
21170 (this means for the whole of a Pine or IMAP session), Exim will not be able to
21171 append messages to it.
21174 .option message_prefix appendfile string&!! "see below"
21175 .cindex "&""From""& line"
21176 The string specified here is expanded and output at the start of every message.
21177 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
21178 in which case it is:
21180 message_prefix = "From ${if def:return_path{$return_path}\
21181 {MAILER-DAEMON}} $tod_bsdinbox\n"
21183 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21184 &`\n`& to &`\r\n`& in &%message_prefix%&.
21186 .option message_suffix appendfile string&!! "see below"
21187 The string specified here is expanded and output at the end of every message.
21188 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
21189 in which case it is a single newline character. The suffix can be suppressed by
21194 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21195 &`\n`& to &`\r\n`& in &%message_suffix%&.
21197 .option mode appendfile "octal integer" 0600
21198 If the output file is created, it is given this mode. If it already exists and
21199 has wider permissions, they are reduced to this mode. If it has narrower
21200 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
21201 if the delivery is the result of a &%save%& command in a filter file specifying
21202 a particular mode, the mode of the output file is always forced to take that
21203 value, and this option is ignored.
21206 .option mode_fail_narrower appendfile boolean true
21207 This option applies in the case when an existing mailbox file has a narrower
21208 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
21209 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
21210 continues with the delivery attempt, using the existing mode of the file.
21213 .option notify_comsat appendfile boolean false
21214 If this option is true, the &'comsat'& daemon is notified after every
21215 successful delivery to a user mailbox. This is the daemon that notifies logged
21216 on users about incoming mail.
21219 .option quota appendfile string&!! unset
21220 .cindex "quota" "imposed by Exim"
21221 This option imposes a limit on the size of the file to which Exim is appending,
21222 or to the total space used in the directory tree when the &%directory%& option
21223 is set. In the latter case, computation of the space used is expensive, because
21224 all the files in the directory (and any sub-directories) have to be
21225 individually inspected and their sizes summed. (See &%quota_size_regex%& and
21226 &%maildir_use_size_file%& for ways to avoid this in environments where users
21227 have no shell access to their mailboxes).
21229 As there is no interlock against two simultaneous deliveries into a
21230 multi-file mailbox, it is possible for the quota to be overrun in this case.
21231 For single-file mailboxes, of course, an interlock is a necessity.
21233 A file's size is taken as its &'used'& value. Because of blocking effects, this
21234 may be a lot less than the actual amount of disk space allocated to the file.
21235 If the sizes of a number of files are being added up, the rounding effect can
21236 become quite noticeable, especially on systems that have large block sizes.
21237 Nevertheless, it seems best to stick to the &'used'& figure, because this is
21238 the obvious value which users understand most easily.
21240 The value of the option is expanded, and must then be a numerical value
21241 (decimal point allowed), optionally followed by one of the letters K, M, or G,
21242 for kilobytes, megabytes, or gigabytes. If Exim is running on a system with
21243 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
21246 &*Note*&: A value of zero is interpreted as &"no quota"&.
21248 The expansion happens while Exim is running as root, before it changes uid for
21249 the delivery. This means that files that are inaccessible to the end user can
21250 be used to hold quota values that are looked up in the expansion. When delivery
21251 fails because this quota is exceeded, the handling of the error is as for
21252 system quota failures.
21254 By default, Exim's quota checking mimics system quotas, and restricts the
21255 mailbox to the specified maximum size, though the value is not accurate to the
21256 last byte, owing to separator lines and additional headers that may get added
21257 during message delivery. When a mailbox is nearly full, large messages may get
21258 refused even though small ones are accepted, because the size of the current
21259 message is added to the quota when the check is made. This behaviour can be
21260 changed by setting &%quota_is_inclusive%& false. When this is done, the check
21261 for exceeding the quota does not include the current message. Thus, deliveries
21262 continue until the quota has been exceeded; thereafter, no further messages are
21263 delivered. See also &%quota_warn_threshold%&.
21266 .option quota_directory appendfile string&!! unset
21267 This option defines the directory to check for quota purposes when delivering
21268 into individual files. The default is the delivery directory, or, if a file
21269 called &_maildirfolder_& exists in a maildir directory, the parent of the
21270 delivery directory.
21273 .option quota_filecount appendfile string&!! 0
21274 This option applies when the &%directory%& option is set. It limits the total
21275 number of files in the directory (compare the inode limit in system quotas). It
21276 can only be used if &%quota%& is also set. The value is expanded; an expansion
21277 failure causes delivery to be deferred. A value of zero is interpreted as
21281 .option quota_is_inclusive appendfile boolean true
21282 See &%quota%& above.
21285 .option quota_size_regex appendfile string unset
21286 This option applies when one of the delivery modes that writes a separate file
21287 for each message is being used. When Exim wants to find the size of one of
21288 these files in order to test the quota, it first checks &%quota_size_regex%&.
21289 If this is set to a regular expression that matches the file name, and it
21290 captures one string, that string is interpreted as a representation of the
21291 file's size. The value of &%quota_size_regex%& is not expanded.
21293 This feature is useful only when users have no shell access to their mailboxes
21294 &-- otherwise they could defeat the quota simply by renaming the files. This
21295 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
21296 the file length to the file name. For example:
21298 maildir_tag = ,S=$message_size
21299 quota_size_regex = ,S=(\d+)
21301 An alternative to &$message_size$& is &$message_linecount$&, which contains the
21302 number of lines in the message.
21304 The regular expression should not assume that the length is at the end of the
21305 file name (even though &%maildir_tag%& puts it there) because maildir MUAs
21306 sometimes add other information onto the ends of message file names.
21308 Section &<<SECID136>>& contains further information.
21311 .option quota_warn_message appendfile string&!! "see below"
21312 See below for the use of this option. If it is not set when
21313 &%quota_warn_threshold%& is set, it defaults to
21315 quota_warn_message = "\
21316 To: $local_part@$domain\n\
21317 Subject: Your mailbox\n\n\
21318 This message is automatically created \
21319 by mail delivery software.\n\n\
21320 The size of your mailbox has exceeded \
21321 a warning threshold that is\n\
21322 set by the system administrator.\n"
21326 .option quota_warn_threshold appendfile string&!! 0
21327 .cindex "quota" "warning threshold"
21328 .cindex "mailbox" "size warning"
21329 .cindex "size" "of mailbox"
21330 This option is expanded in the same way as &%quota%& (see above). If the
21331 resulting value is greater than zero, and delivery of the message causes the
21332 size of the file or total space in the directory tree to cross the given
21333 threshold, a warning message is sent. If &%quota%& is also set, the threshold
21334 may be specified as a percentage of it by following the value with a percent
21338 quota_warn_threshold = 75%
21340 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
21341 percent sign is ignored.
21343 The warning message itself is specified by the &%quota_warn_message%& option,
21344 and it must start with a &'To:'& header line containing the recipient(s) of the
21345 warning message. These do not necessarily have to include the recipient(s) of
21346 the original message. A &'Subject:'& line should also normally be supplied. You
21347 can include any other header lines that you want. If you do not include a
21348 &'From:'& line, the default is:
21350 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
21352 .oindex &%errors_reply_to%&
21353 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
21356 The &%quota%& option does not have to be set in order to use this option; they
21357 are independent of one another except when the threshold is specified as a
21361 .option use_bsmtp appendfile boolean false
21362 .cindex "envelope sender"
21363 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
21364 format, with the envelope sender and recipient(s) included as SMTP commands. If
21365 you want to include a leading HELO command with such messages, you can do
21366 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
21367 for details of batch SMTP.
21370 .option use_crlf appendfile boolean false
21371 .cindex "carriage return"
21373 This option causes lines to be terminated with the two-character CRLF sequence
21374 (carriage return, linefeed) instead of just a linefeed character. In the case
21375 of batched SMTP, the byte sequence written to the file is then an exact image
21376 of what would be sent down a real SMTP connection.
21378 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
21379 (which are used to supply the traditional &"From&~"& and blank line separators
21380 in Berkeley-style mailboxes) are written verbatim, so must contain their own
21381 carriage return characters if these are needed. In cases where these options
21382 have non-empty defaults, the values end with a single linefeed, so they must be
21383 changed to end with &`\r\n`& if &%use_crlf%& is set.
21386 .option use_fcntl_lock appendfile boolean "see below"
21387 This option controls the use of the &[fcntl()]& function to lock a file for
21388 exclusive use when a message is being appended. It is set by default unless
21389 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
21390 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
21391 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
21394 .option use_flock_lock appendfile boolean false
21395 This option is provided to support the use of &[flock()]& for file locking, for
21396 the few situations where it is needed. Most modern operating systems support
21397 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
21398 each other. Exim uses &[fcntl()]& locking by default.
21400 This option is required only if you are using an operating system where
21401 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
21402 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
21403 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
21405 .cindex "Solaris" "&[flock()]& support"
21406 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
21407 have it (and some, I think, provide a not quite right version built on top of
21408 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
21409 the ability to use it, and any attempt to do so will cause a configuration
21412 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
21413 is just being mapped onto &[fcntl()]& by the OS).
21416 .option use_lockfile appendfile boolean "see below"
21417 If this option is turned off, Exim does not attempt to create a lock file when
21418 appending to a mailbox file. In this situation, the only locking is by
21419 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
21420 sure that every MUA that is ever going to look at your users' mailboxes uses
21421 &[fcntl()]& rather than a lock file, and even then only when you are not
21422 delivering over NFS from more than one host.
21424 .cindex "NFS" "lock file"
21425 In order to append to an NFS file safely from more than one host, it is
21426 necessary to take out a lock &'before'& opening the file, and the lock file
21427 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
21430 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
21431 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
21432 except when &%mbx_format%& is set.
21435 .option use_mbx_lock appendfile boolean "see below"
21436 This option is available only if Exim has been compiled with SUPPORT_MBX
21437 set in &_Local/Makefile_&. Setting the option specifies that special MBX
21438 locking rules be used. It is set by default if &%mbx_format%& is set and none
21439 of the locking options are mentioned in the configuration. The locking rules
21440 are the same as are used by the &'c-client'& library that underlies Pine and
21441 the IMAP4 and POP daemons that come with it (see the discussion below). The
21442 rules allow for shared access to the mailbox. However, this kind of locking
21443 does not work when the mailbox is NFS mounted.
21445 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
21446 &%use_flock_lock%& to control what kind of locking is used in implementing the
21447 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
21448 without &%use_fcntl_lock%& or &%use_flock_lock%&.
21453 .section "Operational details for appending" "SECTopappend"
21454 .cindex "appending to a file"
21455 .cindex "file" "appending"
21456 Before appending to a file, the following preparations are made:
21459 If the name of the file is &_/dev/null_&, no action is taken, and a success
21463 .cindex "directory creation"
21464 If any directories on the file's path are missing, Exim creates them if the
21465 &%create_directory%& option is set. A created directory's mode is given by the
21466 &%directory_mode%& option.
21469 If &%file_format%& is set, the format of an existing file is checked. If this
21470 indicates that a different transport should be used, control is passed to that
21474 .cindex "file" "locking"
21475 .cindex "locking files"
21476 .cindex "NFS" "lock file"
21477 If &%use_lockfile%& is set, a lock file is built in a way that will work
21478 reliably over NFS, as follows:
21481 Create a &"hitching post"& file whose name is that of the lock file with the
21482 current time, primary host name, and process id added, by opening for writing
21483 as a new file. If this fails with an access error, delivery is deferred.
21485 Close the hitching post file, and hard link it to the lock file name.
21487 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
21488 Unlink the hitching post name.
21490 Otherwise, use &[stat()]& to get information about the hitching post file, and
21491 then unlink hitching post name. If the number of links is exactly two, creation
21492 of the lock file succeeded but something (for example, an NFS server crash and
21493 restart) caused this fact not to be communicated to the &[link()]& call.
21495 If creation of the lock file failed, wait for &%lock_interval%& and try again,
21496 up to &%lock_retries%& times. However, since any program that writes to a
21497 mailbox should complete its task very quickly, it is reasonable to time out old
21498 lock files that are normally the result of user agent and system crashes. If an
21499 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
21500 it before trying again.
21504 A call is made to &[lstat()]& to discover whether the main file exists, and if
21505 so, what its characteristics are. If &[lstat()]& fails for any reason other
21506 than non-existence, delivery is deferred.
21509 .cindex "symbolic link" "to mailbox"
21510 .cindex "mailbox" "symbolic link"
21511 If the file does exist and is a symbolic link, delivery is deferred, unless the
21512 &%allow_symlink%& option is set, in which case the ownership of the link is
21513 checked, and then &[stat()]& is called to find out about the real file, which
21514 is then subjected to the checks below. The check on the top-level link
21515 ownership prevents one user creating a link for another's mailbox in a sticky
21516 directory, though allowing symbolic links in this case is definitely not a good
21517 idea. If there is a chain of symbolic links, the intermediate ones are not
21521 If the file already exists but is not a regular file, or if the file's owner
21522 and group (if the group is being checked &-- see &%check_group%& above) are
21523 different from the user and group under which the delivery is running,
21524 delivery is deferred.
21527 If the file's permissions are more generous than specified, they are reduced.
21528 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
21529 is set false, in which case the delivery is tried using the existing
21533 The file's inode number is saved, and the file is then opened for appending.
21534 If this fails because the file has vanished, &(appendfile)& behaves as if it
21535 hadn't existed (see below). For any other failures, delivery is deferred.
21538 If the file is opened successfully, check that the inode number hasn't
21539 changed, that it is still a regular file, and that the owner and permissions
21540 have not changed. If anything is wrong, defer delivery and freeze the message.
21543 If the file did not exist originally, defer delivery if the &%file_must_exist%&
21544 option is set. Otherwise, check that the file is being created in a permitted
21545 directory if the &%create_file%& option is set (deferring on failure), and then
21546 open for writing as a new file, with the O_EXCL and O_CREAT options,
21547 except when dealing with a symbolic link (the &%allow_symlink%& option must be
21548 set). In this case, which can happen if the link points to a non-existent file,
21549 the file is opened for writing using O_CREAT but not O_EXCL, because
21550 that prevents link following.
21553 .cindex "loop" "while file testing"
21554 If opening fails because the file exists, obey the tests given above for
21555 existing files. However, to avoid looping in a situation where the file is
21556 being continuously created and destroyed, the exists/not-exists loop is broken
21557 after 10 repetitions, and the message is then frozen.
21560 If opening fails with any other error, defer delivery.
21563 .cindex "file" "locking"
21564 .cindex "locking files"
21565 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
21566 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
21567 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
21568 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
21569 file, and an exclusive lock on the file whose name is
21571 /tmp/.<device-number>.<inode-number>
21573 using the device and inode numbers of the open mailbox file, in accordance with
21574 the MBX locking rules. This file is created with a mode that is specified by
21575 the &%lockfile_mode%& option.
21577 If Exim fails to lock the file, there are two possible courses of action,
21578 depending on the value of the locking timeout. This is obtained from
21579 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
21581 If the timeout value is zero, the file is closed, Exim waits for
21582 &%lock_interval%&, and then goes back and re-opens the file as above and tries
21583 to lock it again. This happens up to &%lock_retries%& times, after which the
21584 delivery is deferred.
21586 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
21587 &[flock()]& are used (with the given timeout), so there has already been some
21588 waiting involved by the time locking fails. Nevertheless, Exim does not give up
21589 immediately. It retries up to
21591 (lock_retries * lock_interval) / <timeout>
21593 times (rounded up).
21596 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
21597 and/or &[flock()]& locks) and then deletes the lock file if one was created.
21600 .section "Operational details for delivery to a new file" "SECTopdir"
21601 .cindex "delivery" "to single file"
21602 .cindex "&""From""& line"
21603 When the &%directory%& option is set instead of &%file%&, each message is
21604 delivered into a newly-created file or set of files. When &(appendfile)& is
21605 activated directly from a &(redirect)& router, neither &%file%& nor
21606 &%directory%& is normally set, because the path for delivery is supplied by the
21607 router. (See for example, the &(address_file)& transport in the default
21608 configuration.) In this case, delivery is to a new file if either the path name
21609 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
21611 No locking is required while writing the message to a new file, so the various
21612 locking options of the transport are ignored. The &"From"& line that by default
21613 separates messages in a single file is not normally needed, nor is the escaping
21614 of message lines that start with &"From"&, and there is no need to ensure a
21615 newline at the end of each message. Consequently, the default values for
21616 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
21617 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
21619 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
21620 the files in the delivery directory by default. However, you can specify a
21621 different directory by setting &%quota_directory%&. Also, for maildir
21622 deliveries (see below) the &_maildirfolder_& convention is honoured.
21625 .cindex "maildir format"
21626 .cindex "mailstore format"
21627 There are three different ways in which delivery to individual files can be
21628 done, controlled by the settings of the &%maildir_format%& and
21629 &%mailstore_format%& options. Note that code to support maildir or mailstore
21630 formats is not included in the binary unless SUPPORT_MAILDIR or
21631 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
21633 .cindex "directory creation"
21634 In all three cases an attempt is made to create the directory and any necessary
21635 sub-directories if they do not exist, provided that the &%create_directory%&
21636 option is set (the default). The location of a created directory can be
21637 constrained by setting &%create_file%&. A created directory's mode is given by
21638 the &%directory_mode%& option. If creation fails, or if the
21639 &%create_directory%& option is not set when creation is required, delivery is
21644 .section "Maildir delivery" "SECTmaildirdelivery"
21645 .cindex "maildir format" "description of"
21646 If the &%maildir_format%& option is true, Exim delivers each message by writing
21647 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
21648 directory that is defined by the &%directory%& option (the &"delivery
21649 directory"&). If the delivery is successful, the file is renamed into the
21650 &_new_& subdirectory.
21652 In the file name, <&'stime'&> is the current time of day in seconds, and
21653 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
21654 Exim checks that the time-of-day clock has moved on by at least one microsecond
21655 before terminating the delivery process. This guarantees uniqueness for the
21656 file name. However, as a precaution, Exim calls &[stat()]& for the file before
21657 opening it. If any response other than ENOENT (does not exist) is given,
21658 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
21660 Before Exim carries out a maildir delivery, it ensures that subdirectories
21661 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
21662 do not exist, Exim tries to create them and any superior directories in their
21663 path, subject to the &%create_directory%& and &%create_file%& options. If the
21664 &%maildirfolder_create_regex%& option is set, and the regular expression it
21665 contains matches the delivery directory, Exim also ensures that a file called
21666 &_maildirfolder_& exists in the delivery directory. If a missing directory or
21667 &_maildirfolder_& file cannot be created, delivery is deferred.
21669 These features make it possible to use Exim to create all the necessary files
21670 and directories in a maildir mailbox, including subdirectories for maildir++
21671 folders. Consider this example:
21673 maildir_format = true
21674 directory = /var/mail/$local_part\
21675 ${if eq{$local_part_suffix}{}{}\
21676 {/.${substr_1:$local_part_suffix}}}
21677 maildirfolder_create_regex = /\.[^/]+$
21679 If &$local_part_suffix$& is empty (there was no suffix for the local part),
21680 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
21681 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
21682 not match this name, so Exim will not look for or create the file
21683 &_/var/mail/pimbo/maildirfolder_&, though it will create
21684 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
21686 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
21687 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
21688 does match &%maildirfolder_create_regex%&. In this case, Exim will create
21689 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
21690 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
21692 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
21693 not inadvertently match the toplevel maildir directory, because a
21694 &_maildirfolder_& file at top level would completely break quota calculations.
21696 .cindex "quota" "in maildir delivery"
21697 .cindex "maildir++"
21698 If Exim is required to check a &%quota%& setting before a maildir delivery, and
21699 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
21700 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
21701 Exim assumes the directory is a maildir++ folder directory, which is one level
21702 down from the user's top level mailbox directory. This causes it to start at
21703 the parent directory instead of the current directory when calculating the
21704 amount of space used.
21706 One problem with delivering into a multi-file mailbox is that it is
21707 computationally expensive to compute the size of the mailbox for quota
21708 checking. Various approaches have been taken to reduce the amount of work
21709 needed. The next two sections describe two of them. A third alternative is to
21710 use some external process for maintaining the size data, and use the expansion
21711 of the &%mailbox_size%& option as a way of importing it into Exim.
21716 .section "Using tags to record message sizes" "SECID135"
21717 If &%maildir_tag%& is set, the string is expanded for each delivery.
21718 When the maildir file is renamed into the &_new_& sub-directory, the
21719 tag is added to its name. However, if adding the tag takes the length of the
21720 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
21721 the tag is dropped and the maildir file is created with no tag.
21724 .vindex "&$message_size$&"
21725 Tags can be used to encode the size of files in their names; see
21726 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
21727 happens after the message has been written. The value of the &$message_size$&
21728 variable is set to the number of bytes actually written. If the expansion is
21729 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
21730 be deferred. The expanded tag may contain any printing characters except &"/"&.
21731 Non-printing characters in the string are ignored; if the resulting string is
21732 empty, it is ignored. If it starts with an alphanumeric character, a leading
21733 colon is inserted; this default has not proven to be the path that popular
21734 maildir implementations have chosen (but changing it in Exim would break
21735 backwards compatibility).
21737 For one common implementation, you might set:
21739 maildir_tag = ,S=${message_size}
21741 but you should check the documentation of the other software to be sure.
21743 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
21744 as this allows Exim to extract the size from your tag, instead of having to
21745 &[stat()]& each message file.
21748 .section "Using a maildirsize file" "SECID136"
21749 .cindex "quota" "in maildir delivery"
21750 .cindex "maildir format" "&_maildirsize_& file"
21751 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
21752 storing quota and message size information in a file called &_maildirsize_&
21753 within the toplevel maildir directory. If this file does not exist, Exim
21754 creates it, setting the quota from the &%quota%& option of the transport. If
21755 the maildir directory itself does not exist, it is created before any attempt
21756 to write a &_maildirsize_& file.
21758 The &_maildirsize_& file is used to hold information about the sizes of
21759 messages in the maildir, thus speeding up quota calculations. The quota value
21760 in the file is just a cache; if the quota is changed in the transport, the new
21761 value overrides the cached value when the next message is delivered. The cache
21762 is maintained for the benefit of other programs that access the maildir and
21763 need to know the quota.
21765 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
21766 file is maintained (with a zero quota setting), but no quota is imposed.
21768 A regular expression is available for controlling which directories in the
21769 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
21770 See the description of the &%maildir_quota_directory_regex%& option above for
21774 .section "Mailstore delivery" "SECID137"
21775 .cindex "mailstore format" "description of"
21776 If the &%mailstore_format%& option is true, each message is written as two
21777 files in the given directory. A unique base name is constructed from the
21778 message id and the current delivery process, and the files that are written use
21779 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
21780 contains the message's envelope, and the &_.msg_& file contains the message
21781 itself. The base name is placed in the variable &$mailstore_basename$&.
21783 During delivery, the envelope is first written to a file with the suffix
21784 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
21785 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
21786 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
21787 file before accessing either of them. An alternative approach is to wait for
21788 the absence of a &_.tmp_& file.
21790 The envelope file starts with any text defined by the &%mailstore_prefix%&
21791 option, expanded and terminated by a newline if there isn't one. Then follows
21792 the sender address on one line, then all the recipient addresses, one per line.
21793 There can be more than one recipient only if the &%batch_max%& option is set
21794 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
21795 appended to the file, followed by a newline if it does not end with one.
21797 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
21798 failure, it is ignored. Other expansion errors are treated as serious
21799 configuration errors, and delivery is deferred. The variable
21800 &$mailstore_basename$& is available for use during these expansions.
21803 .section "Non-special new file delivery" "SECID138"
21804 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
21805 file is created directly in the named directory. For example, when delivering
21806 messages into files in batched SMTP format for later delivery to some host (see
21807 section &<<SECTbatchSMTP>>&), a setting such as
21809 directory = /var/bsmtp/$host
21811 might be used. A message is written to a file with a temporary name, which is
21812 then renamed when the delivery is complete. The final name is obtained by
21813 expanding the contents of the &%directory_file%& option.
21814 .ecindex IIDapptra1
21815 .ecindex IIDapptra2
21822 . ////////////////////////////////////////////////////////////////////////////
21823 . ////////////////////////////////////////////////////////////////////////////
21825 .chapter "The autoreply transport" "CHID8"
21826 .scindex IIDauttra1 "transports" "&(autoreply)&"
21827 .scindex IIDauttra2 "&(autoreply)& transport"
21828 The &(autoreply)& transport is not a true transport in that it does not cause
21829 the message to be transmitted. Instead, it generates a new mail message as an
21830 automatic reply to the incoming message. &'References:'& and
21831 &'Auto-Submitted:'& header lines are included. These are constructed according
21832 to the rules in RFCs 2822 and 3834, respectively.
21834 If the router that passes the message to this transport does not have the
21835 &%unseen%& option set, the original message (for the current recipient) is not
21836 delivered anywhere. However, when the &%unseen%& option is set on the router
21837 that passes the message to this transport, routing of the address continues, so
21838 another router can set up a normal message delivery.
21841 The &(autoreply)& transport is usually run as the result of mail filtering, a
21842 &"vacation"& message being the standard example. However, it can also be run
21843 directly from a router like any other transport. To reduce the possibility of
21844 message cascades, messages created by the &(autoreply)& transport always have
21845 empty envelope sender addresses, like bounce messages.
21847 The parameters of the message to be sent can be specified in the configuration
21848 by options described below. However, these are used only when the address
21849 passed to the transport does not contain its own reply information. When the
21850 transport is run as a consequence of a
21852 or &%vacation%& command in a filter file, the parameters of the message are
21853 supplied by the filter, and passed with the address. The transport's options
21854 that define the message are then ignored (so they are not usually set in this
21855 case). The message is specified entirely by the filter or by the transport; it
21856 is never built from a mixture of options. However, the &%file_optional%&,
21857 &%mode%&, and &%return_message%& options apply in all cases.
21859 &(Autoreply)& is implemented as a local transport. When used as a result of a
21860 command in a user's filter file, &(autoreply)& normally runs under the uid and
21861 gid of the user, and with appropriate current and home directories (see chapter
21862 &<<CHAPenvironment>>&).
21864 There is a subtle difference between routing a message to a &(pipe)& transport
21865 that generates some text to be returned to the sender, and routing it to an
21866 &(autoreply)& transport. This difference is noticeable only if more than one
21867 address from the same message is so handled. In the case of a pipe, the
21868 separate outputs from the different addresses are gathered up and returned to
21869 the sender in a single message, whereas if &(autoreply)& is used, a separate
21870 message is generated for each address that is passed to it.
21872 Non-printing characters are not permitted in the header lines generated for the
21873 message that &(autoreply)& creates, with the exception of newlines that are
21874 immediately followed by white space. If any non-printing characters are found,
21875 the transport defers.
21876 Whether characters with the top bit set count as printing characters or not is
21877 controlled by the &%print_topbitchars%& global option.
21879 If any of the generic options for manipulating headers (for example,
21880 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
21881 of the original message that is included in the generated message when
21882 &%return_message%& is set. They do not apply to the generated message itself.
21884 .vindex "&$sender_address$&"
21885 If the &(autoreply)& transport receives return code 2 from Exim when it submits
21886 the message, indicating that there were no recipients, it does not treat this
21887 as an error. This means that autoreplies sent to &$sender_address$& when this
21888 is empty (because the incoming message is a bounce message) do not cause
21889 problems. They are just discarded.
21893 .section "Private options for autoreply" "SECID139"
21894 .cindex "options" "&(autoreply)& transport"
21896 .option bcc autoreply string&!! unset
21897 This specifies the addresses that are to receive &"blind carbon copies"& of the
21898 message when the message is specified by the transport.
21901 .option cc autoreply string&!! unset
21902 This specifies recipients of the message and the contents of the &'Cc:'& header
21903 when the message is specified by the transport.
21906 .option file autoreply string&!! unset
21907 The contents of the file are sent as the body of the message when the message
21908 is specified by the transport. If both &%file%& and &%text%& are set, the text
21909 string comes first.
21912 .option file_expand autoreply boolean false
21913 If this is set, the contents of the file named by the &%file%& option are
21914 subjected to string expansion as they are added to the message.
21917 .option file_optional autoreply boolean false
21918 If this option is true, no error is generated if the file named by the &%file%&
21919 option or passed with the address does not exist or cannot be read.
21922 .option from autoreply string&!! unset
21923 This specifies the contents of the &'From:'& header when the message is
21924 specified by the transport.
21927 .option headers autoreply string&!! unset
21928 This specifies additional RFC 2822 headers that are to be added to the message
21929 when the message is specified by the transport. Several can be given by using
21930 &"\n"& to separate them. There is no check on the format.
21933 .option log autoreply string&!! unset
21934 This option names a file in which a record of every message sent is logged when
21935 the message is specified by the transport.
21938 .option mode autoreply "octal integer" 0600
21939 If either the log file or the &"once"& file has to be created, this mode is
21943 .option never_mail autoreply "address list&!!" unset
21944 If any run of the transport creates a message with a recipient that matches any
21945 item in the list, that recipient is quietly discarded. If all recipients are
21946 discarded, no message is created. This applies both when the recipients are
21947 generated by a filter and when they are specified in the transport.
21951 .option once autoreply string&!! unset
21952 This option names a file or DBM database in which a record of each &'To:'&
21953 recipient is kept when the message is specified by the transport. &*Note*&:
21954 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
21956 If &%once%& is unset, or is set to an empty string, the message is always sent.
21957 By default, if &%once%& is set to a non-empty file name, the message
21958 is not sent if a potential recipient is already listed in the database.
21959 However, if the &%once_repeat%& option specifies a time greater than zero, the
21960 message is sent if that much time has elapsed since a message was last sent to
21961 this recipient. A setting of zero time for &%once_repeat%& (the default)
21962 prevents a message from being sent a second time &-- in this case, zero means
21965 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
21966 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
21967 greater than zero, it changes the way Exim implements the &%once%& option.
21968 Instead of using a DBM file to record every recipient it sends to, it uses a
21969 regular file, whose size will never get larger than the given value.
21971 In the file, Exim keeps a linear list of recipient addresses and the times at
21972 which they were sent messages. If the file is full when a new address needs to
21973 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
21974 means that a given recipient may receive multiple messages, but at
21975 unpredictable intervals that depend on the rate of turnover of addresses in the
21976 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
21979 .option once_file_size autoreply integer 0
21980 See &%once%& above.
21983 .option once_repeat autoreply time&!! 0s
21984 See &%once%& above.
21985 After expansion, the value of this option must be a valid time value.
21988 .option reply_to autoreply string&!! unset
21989 This specifies the contents of the &'Reply-To:'& header when the message is
21990 specified by the transport.
21993 .option return_message autoreply boolean false
21994 If this is set, a copy of the original message is returned with the new
21995 message, subject to the maximum size set in the &%return_size_limit%& global
21996 configuration option.
21999 .option subject autoreply string&!! unset
22000 This specifies the contents of the &'Subject:'& header when the message is
22001 specified by the transport. It is tempting to quote the original subject in
22002 automatic responses. For example:
22004 subject = Re: $h_subject:
22006 There is a danger in doing this, however. It may allow a third party to
22007 subscribe your users to an opt-in mailing list, provided that the list accepts
22008 bounce messages as subscription confirmations. Well-managed lists require a
22009 non-bounce message to confirm a subscription, so the danger is relatively
22014 .option text autoreply string&!! unset
22015 This specifies a single string to be used as the body of the message when the
22016 message is specified by the transport. If both &%text%& and &%file%& are set,
22017 the text comes first.
22020 .option to autoreply string&!! unset
22021 This specifies recipients of the message and the contents of the &'To:'& header
22022 when the message is specified by the transport.
22023 .ecindex IIDauttra1
22024 .ecindex IIDauttra2
22029 . ////////////////////////////////////////////////////////////////////////////
22030 . ////////////////////////////////////////////////////////////////////////////
22032 .chapter "The lmtp transport" "CHAPLMTP"
22033 .cindex "transports" "&(lmtp)&"
22034 .cindex "&(lmtp)& transport"
22035 .cindex "LMTP" "over a pipe"
22036 .cindex "LMTP" "over a socket"
22037 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
22039 or by interacting with a Unix domain socket.
22040 This transport is something of a cross between the &(pipe)& and &(smtp)&
22041 transports. Exim also has support for using LMTP over TCP/IP; this is
22042 implemented as an option for the &(smtp)& transport. Because LMTP is expected
22043 to be of minority interest, the default build-time configure in &_src/EDITME_&
22044 has it commented out. You need to ensure that
22048 .cindex "options" "&(lmtp)& transport"
22049 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
22050 included in the Exim binary. The private options of the &(lmtp)& transport are
22053 .option batch_id lmtp string&!! unset
22054 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22057 .option batch_max lmtp integer 1
22058 This limits the number of addresses that can be handled in a single delivery.
22059 Most LMTP servers can handle several addresses at once, so it is normally a
22060 good idea to increase this value. See the description of local delivery
22061 batching in chapter &<<CHAPbatching>>&.
22064 .option command lmtp string&!! unset
22065 This option must be set if &%socket%& is not set. The string is a command which
22066 is run in a separate process. It is split up into a command name and list of
22067 arguments, each of which is separately expanded (so expansion cannot change the
22068 number of arguments). The command is run directly, not via a shell. The message
22069 is passed to the new process using the standard input and output to operate the
22072 .option ignore_quota lmtp boolean false
22073 .cindex "LMTP" "ignoring quota errors"
22074 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
22075 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
22076 in its response to the LHLO command.
22078 .option socket lmtp string&!! unset
22079 This option must be set if &%command%& is not set. The result of expansion must
22080 be the name of a Unix domain socket. The transport connects to the socket and
22081 delivers the message to it using the LMTP protocol.
22084 .option timeout lmtp time 5m
22085 The transport is aborted if the created process or Unix domain socket does not
22086 respond to LMTP commands or message input within this timeout. Delivery
22087 is deferred, and will be tried again later. Here is an example of a typical
22092 command = /some/local/lmtp/delivery/program
22096 This delivers up to 20 addresses at a time, in a mixture of domains if
22097 necessary, running as the user &'exim'&.
22101 . ////////////////////////////////////////////////////////////////////////////
22102 . ////////////////////////////////////////////////////////////////////////////
22104 .chapter "The pipe transport" "CHAPpipetransport"
22105 .scindex IIDpiptra1 "transports" "&(pipe)&"
22106 .scindex IIDpiptra2 "&(pipe)& transport"
22107 The &(pipe)& transport is used to deliver messages via a pipe to a command
22108 running in another process. One example is the use of &(pipe)& as a
22109 pseudo-remote transport for passing messages to some other delivery mechanism
22110 (such as UUCP). Another is the use by individual users to automatically process
22111 their incoming messages. The &(pipe)& transport can be used in one of the
22115 .vindex "&$local_part$&"
22116 A router routes one address to a transport in the normal way, and the
22117 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
22118 contains the local part of the address (as usual), and the command that is run
22119 is specified by the &%command%& option on the transport.
22121 .vindex "&$pipe_addresses$&"
22122 If the &%batch_max%& option is set greater than 1 (the default is 1), the
22123 transport can handle more than one address in a single run. In this case, when
22124 more than one address is routed to the transport, &$local_part$& is not set
22125 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
22126 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
22127 that are routed to the transport.
22129 .vindex "&$address_pipe$&"
22130 A router redirects an address directly to a pipe command (for example, from an
22131 alias or forward file). In this case, &$address_pipe$& contains the text of the
22132 pipe command, and the &%command%& option on the transport is ignored unless
22133 &%force_command%& is set. If only one address is being transported
22134 (&%batch_max%& is not greater than one, or only one address was redirected to
22135 this pipe command), &$local_part$& contains the local part that was redirected.
22139 The &(pipe)& transport is a non-interactive delivery method. Exim can also
22140 deliver messages over pipes using the LMTP interactive protocol. This is
22141 implemented by the &(lmtp)& transport.
22143 In the case when &(pipe)& is run as a consequence of an entry in a local user's
22144 &_.forward_& file, the command runs under the uid and gid of that user. In
22145 other cases, the uid and gid have to be specified explicitly, either on the
22146 transport or on the router that handles the address. Current and &"home"&
22147 directories are also controllable. See chapter &<<CHAPenvironment>>& for
22148 details of the local delivery environment and chapter &<<CHAPbatching>>&
22149 for a discussion of local delivery batching.
22152 .section "Concurrent delivery" "SECID140"
22153 If two messages arrive at almost the same time, and both are routed to a pipe
22154 delivery, the two pipe transports may be run concurrently. You must ensure that
22155 any pipe commands you set up are robust against this happening. If the commands
22156 write to a file, the &%exim_lock%& utility might be of use.
22161 .section "Returned status and data" "SECID141"
22162 .cindex "&(pipe)& transport" "returned data"
22163 If the command exits with a non-zero return code, the delivery is deemed to
22164 have failed, unless either the &%ignore_status%& option is set (in which case
22165 the return code is treated as zero), or the return code is one of those listed
22166 in the &%temp_errors%& option, which are interpreted as meaning &"try again
22167 later"&. In this case, delivery is deferred. Details of a permanent failure are
22168 logged, but are not included in the bounce message, which merely contains
22169 &"local delivery failed"&.
22171 If the command exits on a signal and the &%freeze_signal%& option is set then
22172 the message will be frozen in the queue. If that option is not set, a bounce
22173 will be sent as normal.
22175 If the return code is greater than 128 and the command being run is a shell
22176 script, it normally means that the script was terminated by a signal whose
22177 value is the return code minus 128. The &%freeze_signal%& option does not
22178 apply in this case.
22180 If Exim is unable to run the command (that is, if &[execve()]& fails), the
22181 return code is set to 127. This is the value that a shell returns if it is
22182 asked to run a non-existent command. The wording for the log line suggests that
22183 a non-existent command may be the problem.
22185 The &%return_output%& option can affect the result of a pipe delivery. If it is
22186 set and the command produces any output on its standard output or standard
22187 error streams, the command is considered to have failed, even if it gave a zero
22188 return code or if &%ignore_status%& is set. The output from the command is
22189 included as part of the bounce message. The &%return_fail_output%& option is
22190 similar, except that output is returned only when the command exits with a
22191 failure return code, that is, a value other than zero or a code that matches
22196 .section "How the command is run" "SECThowcommandrun"
22197 .cindex "&(pipe)& transport" "path for command"
22198 The command line is (by default) broken down into a command name and arguments
22199 by the &(pipe)& transport itself. The &%allow_commands%& and
22200 &%restrict_to_path%& options can be used to restrict the commands that may be
22203 .cindex "quoting" "in pipe command"
22204 Unquoted arguments are delimited by white space. If an argument appears in
22205 double quotes, backslash is interpreted as an escape character in the usual
22206 way. If an argument appears in single quotes, no escaping is done.
22208 String expansion is applied to the command line except when it comes from a
22209 traditional &_.forward_& file (commands from a filter file are expanded). The
22210 expansion is applied to each argument in turn rather than to the whole line.
22211 For this reason, any string expansion item that contains white space must be
22212 quoted so as to be contained within a single argument. A setting such as
22214 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
22216 will not work, because the expansion item gets split between several
22217 arguments. You have to write
22219 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
22221 to ensure that it is all in one argument. The expansion is done in this way,
22222 argument by argument, so that the number of arguments cannot be changed as a
22223 result of expansion, and quotes or backslashes in inserted variables do not
22224 interact with external quoting. However, this leads to problems if you want to
22225 generate multiple arguments (or the command name plus arguments) from a single
22226 expansion. In this situation, the simplest solution is to use a shell. For
22229 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
22232 .cindex "transport" "filter"
22233 .cindex "filter" "transport filter"
22234 .vindex "&$pipe_addresses$&"
22235 Special handling takes place when an argument consists of precisely the text
22236 &`$pipe_addresses`&. This is not a general expansion variable; the only
22237 place this string is recognized is when it appears as an argument for a pipe or
22238 transport filter command. It causes each address that is being handled to be
22239 inserted in the argument list at that point &'as a separate argument'&. This
22240 avoids any problems with spaces or shell metacharacters, and is of use when a
22241 &(pipe)& transport is handling groups of addresses in a batch.
22243 If &%force_command%& is enabled on the transport, Special handling takes place
22244 for an argument that consists of precisely the text &`$address_pipe`&. It
22245 is handled similarly to &$pipe_addresses$& above. It is expanded and each
22246 argument is inserted in the argument list at that point
22247 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
22248 the only item in the argument; in fact, if it were then &%force_command%&
22249 should behave as a no-op. Rather, it should be used to adjust the command
22250 run while preserving the argument vector separation.
22252 After splitting up into arguments and expansion, the resulting command is run
22253 in a subprocess directly from the transport, &'not'& under a shell. The
22254 message that is being delivered is supplied on the standard input, and the
22255 standard output and standard error are both connected to a single pipe that is
22256 read by Exim. The &%max_output%& option controls how much output the command
22257 may produce, and the &%return_output%& and &%return_fail_output%& options
22258 control what is done with it.
22260 Not running the command under a shell (by default) lessens the security risks
22261 in cases when a command from a user's filter file is built out of data that was
22262 taken from an incoming message. If a shell is required, it can of course be
22263 explicitly specified as the command to be run. However, there are circumstances
22264 where existing commands (for example, in &_.forward_& files) expect to be run
22265 under a shell and cannot easily be modified. To allow for these cases, there is
22266 an option called &%use_shell%&, which changes the way the &(pipe)& transport
22267 works. Instead of breaking up the command line as just described, it expands it
22268 as a single string and passes the result to &_/bin/sh_&. The
22269 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
22270 with &%use_shell%&, and the whole mechanism is inherently less secure.
22274 .section "Environment variables" "SECTpipeenv"
22275 .cindex "&(pipe)& transport" "environment for command"
22276 .cindex "environment for pipe transport"
22277 The environment variables listed below are set up when the command is invoked.
22278 This list is a compromise for maximum compatibility with other MTAs. Note that
22279 the &%environment%& option can be used to add additional variables to this
22282 &`DOMAIN `& the domain of the address
22283 &`HOME `& the home directory, if set
22284 &`HOST `& the host name when called from a router (see below)
22285 &`LOCAL_PART `& see below
22286 &`LOCAL_PART_PREFIX `& see below
22287 &`LOCAL_PART_SUFFIX `& see below
22288 &`LOGNAME `& see below
22289 &`MESSAGE_ID `& Exim's local ID for the message
22290 &`PATH `& as specified by the &%path%& option below
22291 &`QUALIFY_DOMAIN `& the sender qualification domain
22292 &`RECIPIENT `& the complete recipient address
22293 &`SENDER `& the sender of the message (empty if a bounce)
22294 &`SHELL `& &`/bin/sh`&
22295 &`TZ `& the value of the &%timezone%& option, if set
22296 &`USER `& see below
22298 When a &(pipe)& transport is called directly from (for example) an &(accept)&
22299 router, LOCAL_PART is set to the local part of the address. When it is
22300 called as a result of a forward or alias expansion, LOCAL_PART is set to
22301 the local part of the address that was expanded. In both cases, any affixes are
22302 removed from the local part, and made available in LOCAL_PART_PREFIX and
22303 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
22304 same value as LOCAL_PART for compatibility with other MTAs.
22307 HOST is set only when a &(pipe)& transport is called from a router that
22308 associates hosts with an address, typically when using &(pipe)& as a
22309 pseudo-remote transport. HOST is set to the first host name specified by
22313 If the transport's generic &%home_directory%& option is set, its value is used
22314 for the HOME environment variable. Otherwise, a home directory may be set
22315 by the router's &%transport_home_directory%& option, which defaults to the
22316 user's home directory if &%check_local_user%& is set.
22319 .section "Private options for pipe" "SECID142"
22320 .cindex "options" "&(pipe)& transport"
22324 .option allow_commands pipe "string list&!!" unset
22325 .cindex "&(pipe)& transport" "permitted commands"
22326 The string is expanded, and is then interpreted as a colon-separated list of
22327 permitted commands. If &%restrict_to_path%& is not set, the only commands
22328 permitted are those in the &%allow_commands%& list. They need not be absolute
22329 paths; the &%path%& option is still used for relative paths. If
22330 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
22331 in the &%allow_commands%& list, or a name without any slashes that is found on
22332 the path. In other words, if neither &%allow_commands%& nor
22333 &%restrict_to_path%& is set, there is no restriction on the command, but
22334 otherwise only commands that are permitted by one or the other are allowed. For
22337 allow_commands = /usr/bin/vacation
22339 and &%restrict_to_path%& is not set, the only permitted command is
22340 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
22341 &%use_shell%& is set.
22344 .option batch_id pipe string&!! unset
22345 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22348 .option batch_max pipe integer 1
22349 This limits the number of addresses that can be handled in a single delivery.
22350 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22353 .option check_string pipe string unset
22354 As &(pipe)& writes the message, the start of each line is tested for matching
22355 &%check_string%&, and if it does, the initial matching characters are replaced
22356 by the contents of &%escape_string%&, provided both are set. The value of
22357 &%check_string%& is a literal string, not a regular expression, and the case of
22358 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
22359 of &%check_string%& and &%escape_string%& are forced to values that implement
22360 the SMTP escaping protocol. Any settings made in the configuration file are
22364 .option command pipe string&!! unset
22365 This option need not be set when &(pipe)& is being used to deliver to pipes
22366 obtained directly from address redirections. In other cases, the option must be
22367 set, to provide a command to be run. It need not yield an absolute path (see
22368 the &%path%& option below). The command is split up into separate arguments by
22369 Exim, and each argument is separately expanded, as described in section
22370 &<<SECThowcommandrun>>& above.
22373 .option environment pipe string&!! unset
22374 .cindex "&(pipe)& transport" "environment for command"
22375 .cindex "environment for &(pipe)& transport"
22376 This option is used to add additional variables to the environment in which the
22377 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
22378 a string which is expanded, and then interpreted as a colon-separated list of
22379 environment settings of the form <&'name'&>=<&'value'&>.
22382 .option escape_string pipe string unset
22383 See &%check_string%& above.
22386 .option freeze_exec_fail pipe boolean false
22387 .cindex "exec failure"
22388 .cindex "failure of exec"
22389 .cindex "&(pipe)& transport" "failure of exec"
22390 Failure to exec the command in a pipe transport is by default treated like
22391 any other failure while running the command. However, if &%freeze_exec_fail%&
22392 is set, failure to exec is treated specially, and causes the message to be
22393 frozen, whatever the setting of &%ignore_status%&.
22396 .option freeze_signal pipe boolean false
22397 .cindex "signal exit"
22398 .cindex "&(pipe)& transport", "signal exit"
22399 Normally if the process run by a command in a pipe transport exits on a signal,
22400 a bounce message is sent. If &%freeze_signal%& is set, the message will be
22401 frozen in Exim's queue instead.
22404 .option force_command pipe boolean false
22405 .cindex "force command"
22406 .cindex "&(pipe)& transport", "force command"
22407 Normally when a router redirects an address directly to a pipe command
22408 the &%command%& option on the transport is ignored. If &%force_command%&
22409 is set, the &%command%& option will used. This is especially
22410 useful for forcing a wrapper or additional argument to be added to the
22411 command. For example:
22413 command = /usr/bin/remote_exec myhost -- $address_pipe
22417 Note that &$address_pipe$& is handled specially in &%command%& when
22418 &%force_command%& is set, expanding out to the original argument vector as
22419 separate items, similarly to a Unix shell &`"$@"`& construct.
22421 .option ignore_status pipe boolean false
22422 If this option is true, the status returned by the subprocess that is set up to
22423 run the command is ignored, and Exim behaves as if zero had been returned.
22424 Otherwise, a non-zero status or termination by signal causes an error return
22425 from the transport unless the status value is one of those listed in
22426 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
22428 &*Note*&: This option does not apply to timeouts, which do not return a status.
22429 See the &%timeout_defer%& option for how timeouts are handled.
22431 .option log_defer_output pipe boolean false
22432 .cindex "&(pipe)& transport" "logging output"
22433 If this option is set, and the status returned by the command is
22434 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
22435 and any output was produced, the first line of it is written to the main log.
22438 .option log_fail_output pipe boolean false
22439 If this option is set, and the command returns any output, and also ends with a
22440 return code that is neither zero nor one of the return codes listed in
22441 &%temp_errors%& (that is, the delivery failed), the first line of output is
22442 written to the main log. This option and &%log_output%& are mutually exclusive.
22443 Only one of them may be set.
22447 .option log_output pipe boolean false
22448 If this option is set and the command returns any output, the first line of
22449 output is written to the main log, whatever the return code. This option and
22450 &%log_fail_output%& are mutually exclusive. Only one of them may be set.
22454 .option max_output pipe integer 20K
22455 This specifies the maximum amount of output that the command may produce on its
22456 standard output and standard error file combined. If the limit is exceeded, the
22457 process running the command is killed. This is intended as a safety measure to
22458 catch runaway processes. The limit is applied independently of the settings of
22459 the options that control what is done with such output (for example,
22460 &%return_output%&). Because of buffering effects, the amount of output may
22461 exceed the limit by a small amount before Exim notices.
22464 .option message_prefix pipe string&!! "see below"
22465 The string specified here is expanded and output at the start of every message.
22466 The default is unset if &%use_bsmtp%& is set. Otherwise it is
22469 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
22473 .cindex "&%tmail%&"
22474 .cindex "&""From""& line"
22475 This is required by the commonly used &_/usr/bin/vacation_& program.
22476 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
22477 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
22482 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
22483 &`\n`& to &`\r\n`& in &%message_prefix%&.
22486 .option message_suffix pipe string&!! "see below"
22487 The string specified here is expanded and output at the end of every message.
22488 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
22489 The suffix can be suppressed by setting
22493 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
22494 &`\n`& to &`\r\n`& in &%message_suffix%&.
22497 .option path pipe string "see below"
22498 This option specifies the string that is set up in the PATH environment
22499 variable of the subprocess. The default is:
22503 If the &%command%& option does not yield an absolute path name, the command is
22504 sought in the PATH directories, in the usual way. &*Warning*&: This does not
22505 apply to a command specified as a transport filter.
22508 .option permit_coredump pipe boolean false
22509 Normally Exim inhibits core-dumps during delivery. If you have a need to get
22510 a core-dump of a pipe command, enable this command. This enables core-dumps
22511 during delivery and affects both the Exim binary and the pipe command run.
22512 It is recommended that this option remain off unless and until you have a need
22513 for it and that this only be enabled when needed, as the risk of excessive
22514 resource consumption can be quite high. Note also that Exim is typically
22515 installed as a setuid binary and most operating systems will inhibit coredumps
22516 of these by default, so further OS-specific action may be required.
22519 .option pipe_as_creator pipe boolean false
22520 .cindex "uid (user id)" "local delivery"
22521 If the generic &%user%& option is not set and this option is true, the delivery
22522 process is run under the uid that was in force when Exim was originally called
22523 to accept the message. If the group id is not otherwise set (via the generic
22524 &%group%& option), the gid that was in force when Exim was originally called to
22525 accept the message is used.
22528 .option restrict_to_path pipe boolean false
22529 When this option is set, any command name not listed in &%allow_commands%& must
22530 contain no slashes. The command is searched for only in the directories listed
22531 in the &%path%& option. This option is intended for use in the case when a pipe
22532 command has been generated from a user's &_.forward_& file. This is usually
22533 handled by a &(pipe)& transport called &%address_pipe%&.
22536 .option return_fail_output pipe boolean false
22537 If this option is true, and the command produced any output and ended with a
22538 return code other than zero or one of the codes listed in &%temp_errors%& (that
22539 is, the delivery failed), the output is returned in the bounce message.
22540 However, if the message has a null sender (that is, it is itself a bounce
22541 message), output from the command is discarded. This option and
22542 &%return_output%& are mutually exclusive. Only one of them may be set.
22546 .option return_output pipe boolean false
22547 If this option is true, and the command produced any output, the delivery is
22548 deemed to have failed whatever the return code from the command, and the output
22549 is returned in the bounce message. Otherwise, the output is just discarded.
22550 However, if the message has a null sender (that is, it is a bounce message),
22551 output from the command is always discarded, whatever the setting of this
22552 option. This option and &%return_fail_output%& are mutually exclusive. Only one
22553 of them may be set.
22557 .option temp_errors pipe "string list" "see below"
22558 .cindex "&(pipe)& transport" "temporary failure"
22559 This option contains either a colon-separated list of numbers, or a single
22560 asterisk. If &%ignore_status%& is false
22561 and &%return_output%& is not set,
22562 and the command exits with a non-zero return code, the failure is treated as
22563 temporary and the delivery is deferred if the return code matches one of the
22564 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
22565 codes are treated as permanent errors. The default setting contains the codes
22566 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
22567 compiled on a system that does not define these macros, it assumes values of 75
22568 and 73, respectively.
22571 .option timeout pipe time 1h
22572 If the command fails to complete within this time, it is killed. This normally
22573 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
22574 specifies no timeout. In order to ensure that any subprocesses created by the
22575 command are also killed, Exim makes the initial process a process group leader,
22576 and kills the whole process group on a timeout. However, this can be defeated
22577 if one of the processes starts a new process group.
22579 .option timeout_defer pipe boolean false
22580 A timeout in a &(pipe)& transport, either in the command that the transport
22581 runs, or in a transport filter that is associated with it, is by default
22582 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
22583 is set true, both kinds of timeout become temporary errors, causing the
22584 delivery to be deferred.
22586 .option umask pipe "octal integer" 022
22587 This specifies the umask setting for the subprocess that runs the command.
22590 .option use_bsmtp pipe boolean false
22591 .cindex "envelope sender"
22592 If this option is set true, the &(pipe)& transport writes messages in &"batch
22593 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
22594 commands. If you want to include a leading HELO command with such messages,
22595 you can do so by setting the &%message_prefix%& option. See section
22596 &<<SECTbatchSMTP>>& for details of batch SMTP.
22598 .option use_classresources pipe boolean false
22599 .cindex "class resources (BSD)"
22600 This option is available only when Exim is running on FreeBSD, NetBSD, or
22601 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
22602 resource limits when a &(pipe)& transport is run to perform a delivery. The
22603 limits for the uid under which the pipe is to run are obtained from the login
22607 .option use_crlf pipe boolean false
22608 .cindex "carriage return"
22610 This option causes lines to be terminated with the two-character CRLF sequence
22611 (carriage return, linefeed) instead of just a linefeed character. In the case
22612 of batched SMTP, the byte sequence written to the pipe is then an exact image
22613 of what would be sent down a real SMTP connection.
22615 The contents of the &%message_prefix%& and &%message_suffix%& options are
22616 written verbatim, so must contain their own carriage return characters if these
22617 are needed. When &%use_bsmtp%& is not set, the default values for both
22618 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
22619 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
22622 .option use_shell pipe boolean false
22623 .vindex "&$pipe_addresses$&"
22624 If this option is set, it causes the command to be passed to &_/bin/sh_&
22625 instead of being run directly from the transport, as described in section
22626 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
22627 where the command is expected to be run under a shell and cannot easily be
22628 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
22629 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
22630 command is expanded as a single string, and handed to &_/bin/sh_& as data for
22635 .section "Using an external local delivery agent" "SECID143"
22636 .cindex "local delivery" "using an external agent"
22637 .cindex "&'procmail'&"
22638 .cindex "external local delivery"
22639 .cindex "delivery" "&'procmail'&"
22640 .cindex "delivery" "by external agent"
22641 The &(pipe)& transport can be used to pass all messages that require local
22642 delivery to a separate local delivery agent such as &%procmail%&. When doing
22643 this, care must be taken to ensure that the pipe is run under an appropriate
22644 uid and gid. In some configurations one wants this to be a uid that is trusted
22645 by the delivery agent to supply the correct sender of the message. It may be
22646 necessary to recompile or reconfigure the delivery agent so that it trusts an
22647 appropriate user. The following is an example transport and router
22648 configuration for &%procmail%&:
22653 command = /usr/local/bin/procmail -d $local_part
22657 check_string = "From "
22658 escape_string = ">From "
22667 transport = procmail_pipe
22669 In this example, the pipe is run as the local user, but with the group set to
22670 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
22671 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
22672 user to supply a correct sender address. If you do not specify either a
22673 &%group%& or a &%user%& option, the pipe command is run as the local user. The
22674 home directory is the user's home directory by default.
22676 &*Note*&: The command that the pipe transport runs does &'not'& begin with
22680 as shown in some &%procmail%& documentation, because Exim does not by default
22681 use a shell to run pipe commands.
22684 The next example shows a transport and a router for a system where local
22685 deliveries are handled by the Cyrus IMAP server.
22688 local_delivery_cyrus:
22690 command = /usr/cyrus/bin/deliver \
22691 -m ${substr_1:$local_part_suffix} -- $local_part
22703 local_part_suffix = .*
22704 transport = local_delivery_cyrus
22706 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
22707 &%return_output%& to cause any text written by Cyrus to be returned to the
22709 .ecindex IIDpiptra1
22710 .ecindex IIDpiptra2
22713 . ////////////////////////////////////////////////////////////////////////////
22714 . ////////////////////////////////////////////////////////////////////////////
22716 .chapter "The smtp transport" "CHAPsmtptrans"
22717 .scindex IIDsmttra1 "transports" "&(smtp)&"
22718 .scindex IIDsmttra2 "&(smtp)& transport"
22719 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
22720 or LMTP protocol. The list of hosts to try can either be taken from the address
22721 that is being processed (having been set up by the router), or specified
22722 explicitly for the transport. Timeout and retry processing (see chapter
22723 &<<CHAPretry>>&) is applied to each IP address independently.
22726 .section "Multiple messages on a single connection" "SECID144"
22727 The sending of multiple messages over a single TCP/IP connection can arise in
22731 If a message contains more than &%max_rcpt%& (see below) addresses that are
22732 routed to the same host, more than one copy of the message has to be sent to
22733 that host. In this situation, multiple copies may be sent in a single run of
22734 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
22735 does when it has too many addresses to send in one message also depends on the
22736 value of the global &%remote_max_parallel%& option. Details are given in
22737 section &<<SECToutSMTPTCP>>&.)
22739 .cindex "hints database" "remembering routing"
22740 When a message has been successfully delivered over a TCP/IP connection, Exim
22741 looks in its hints database to see if there are any other messages awaiting a
22742 connection to the same host. If there are, a new delivery process is started
22743 for one of them, and the current TCP/IP connection is passed on to it. The new
22744 process may in turn send multiple copies and possibly create yet another
22749 For each copy sent over the same TCP/IP connection, a sequence counter is
22750 incremented, and if it ever gets to the value of &%connection_max_messages%&,
22751 no further messages are sent over that connection.
22755 .section "Use of the $host and $host_address variables" "SECID145"
22757 .vindex "&$host_address$&"
22758 At the start of a run of the &(smtp)& transport, the values of &$host$& and
22759 &$host_address$& are the name and IP address of the first host on the host list
22760 passed by the router. However, when the transport is about to connect to a
22761 specific host, and while it is connected to that host, &$host$& and
22762 &$host_address$& are set to the values for that host. These are the values
22763 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
22764 &%serialize_hosts%&, and the various TLS options are expanded.
22767 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
22768 .vindex &$tls_bits$&
22769 .vindex &$tls_cipher$&
22770 .vindex &$tls_peerdn$&
22771 .vindex &$tls_sni$&
22772 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
22773 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
22774 are the values that were set when the message was received.
22775 These are the values that are used for options that are expanded before any
22776 SMTP connections are made. Just before each connection is made, these four
22777 variables are emptied. If TLS is subsequently started, they are set to the
22778 appropriate values for the outgoing connection, and these are the values that
22779 are in force when any authenticators are run and when the
22780 &%authenticated_sender%& option is expanded.
22782 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
22783 and will be removed in a future release.
22786 .section "Private options for smtp" "SECID146"
22787 .cindex "options" "&(smtp)& transport"
22788 The private options of the &(smtp)& transport are as follows:
22791 .option address_retry_include_sender smtp boolean true
22792 .cindex "4&'xx'& responses" "retrying after"
22793 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
22794 is the combination of sender and recipient that is delayed in subsequent queue
22795 runs until the retry time is reached. You can delay the recipient without
22796 reference to the sender (which is what earlier versions of Exim did), by
22797 setting &%address_retry_include_sender%& false. However, this can lead to
22798 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
22800 .option allow_localhost smtp boolean false
22801 .cindex "local host" "sending to"
22802 .cindex "fallback" "hosts specified on transport"
22803 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
22804 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
22805 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
22806 the delivery anyway. This should be used only in special cases when the
22807 configuration ensures that no looping will result (for example, a differently
22808 configured Exim is listening on the port to which the message is sent).
22811 .option authenticated_sender smtp string&!! unset
22813 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
22814 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
22815 overriding any existing authenticated sender value. If the string expansion is
22816 forced to fail, the option is ignored. Other expansion failures cause delivery
22817 to be deferred. If the result of expansion is an empty string, that is also
22820 The expansion happens after the outgoing connection has been made and TLS
22821 started, if required. This means that the &$host$&, &$host_address$&,
22822 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
22823 particular connection.
22825 If the SMTP session is not authenticated, the expansion of
22826 &%authenticated_sender%& still happens (and can cause the delivery to be
22827 deferred if it fails), but no AUTH= item is added to MAIL commands
22828 unless &%authenticated_sender_force%& is true.
22830 This option allows you to use the &(smtp)& transport in LMTP mode to
22831 deliver mail to Cyrus IMAP and provide the proper local part as the
22832 &"authenticated sender"&, via a setting such as:
22834 authenticated_sender = $local_part
22836 This removes the need for IMAP subfolders to be assigned special ACLs to
22837 allow direct delivery to those subfolders.
22839 Because of expected uses such as that just described for Cyrus (when no
22840 domain is involved), there is no checking on the syntax of the provided
22844 .option authenticated_sender_force smtp boolean false
22845 If this option is set true, the &%authenticated_sender%& option's value
22846 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
22847 authenticated as a client.
22850 .option command_timeout smtp time 5m
22851 This sets a timeout for receiving a response to an SMTP command that has been
22852 sent out. It is also used when waiting for the initial banner line from the
22853 remote host. Its value must not be zero.
22856 .option connect_timeout smtp time 5m
22857 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
22858 to a remote host. A setting of zero allows the system timeout (typically
22859 several minutes) to act. To have any effect, the value of this option must be
22860 less than the system timeout. However, it has been observed that on some
22861 systems there is no system timeout, which is why the default value for this
22862 option is 5 minutes, a value recommended by RFC 1123.
22865 .option connection_max_messages smtp integer 500
22866 .cindex "SMTP" "passed connection"
22867 .cindex "SMTP" "multiple deliveries"
22868 .cindex "multiple SMTP deliveries"
22869 This controls the maximum number of separate message deliveries that are sent
22870 over a single TCP/IP connection. If the value is zero, there is no limit.
22871 For testing purposes, this value can be overridden by the &%-oB%& command line
22875 .option data_timeout smtp time 5m
22876 This sets a timeout for the transmission of each block in the data portion of
22877 the message. As a result, the overall timeout for a message depends on the size
22878 of the message. Its value must not be zero. See also &%final_timeout%&.
22881 .option delay_after_cutoff smtp boolean true
22882 This option controls what happens when all remote IP addresses for a given
22883 domain have been inaccessible for so long that they have passed their retry
22886 In the default state, if the next retry time has not been reached for any of
22887 them, the address is bounced without trying any deliveries. In other words,
22888 Exim delays retrying an IP address after the final cutoff time until a new
22889 retry time is reached, and can therefore bounce an address without ever trying
22890 a delivery, when machines have been down for a long time. Some people are
22891 unhappy at this prospect, so...
22893 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
22894 addresses are past their final cutoff time, Exim tries to deliver to those
22895 IP addresses that have not been tried since the message arrived. If there are
22896 none, of if they all fail, the address is bounced. In other words, it does not
22897 delay when a new message arrives, but immediately tries those expired IP
22898 addresses that haven't been tried since the message arrived. If there is a
22899 continuous stream of messages for the dead hosts, unsetting
22900 &%delay_after_cutoff%& means that there will be many more attempts to deliver
22904 .option dns_qualify_single smtp boolean true
22905 If the &%hosts%& or &%fallback_hosts%& option is being used,
22906 and the &%gethostbyname%& option is false,
22907 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
22908 in chapter &<<CHAPdnslookup>>& for more details.
22911 .option dns_search_parents smtp boolean false
22912 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
22913 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
22914 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
22918 .option dnssec_request_domains smtp "domain list&!!" unset
22919 .cindex "MX record" "security"
22920 .cindex "DNSSEC" "MX lookup"
22921 .cindex "security" "MX lookup"
22922 .cindex "DNS" "DNSSEC"
22923 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
22924 the dnssec request bit set.
22925 This applies to all of the SRV, MX A6, AAAA, A lookup sequence.
22929 .option dnssec_require_domains smtp "domain list&!!" unset
22930 .cindex "MX record" "security"
22931 .cindex "DNSSEC" "MX lookup"
22932 .cindex "security" "MX lookup"
22933 .cindex "DNS" "DNSSEC"
22934 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
22935 the dnssec request bit set. Any returns not having the Authenticated Data bit
22936 (AD bit) set wil be ignored and logged as a host-lookup failure.
22937 This applies to all of the SRV, MX A6, AAAA, A lookup sequence.
22941 .option dscp smtp string&!! unset
22942 .cindex "DCSP" "outbound"
22943 This option causes the DSCP value associated with a socket to be set to one
22944 of a number of fixed strings or to numeric value.
22945 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
22946 Common values include &`throughput`&, &`mincost`&, and on newer systems
22947 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
22949 The outbound packets from Exim will be marked with this value in the header
22950 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
22951 that these values will have any effect, not be stripped by networking
22952 equipment, or do much of anything without cooperation with your Network
22953 Engineer and those of all network operators between the source and destination.
22956 .option fallback_hosts smtp "string list" unset
22957 .cindex "fallback" "hosts specified on transport"
22958 String expansion is not applied to this option. The argument must be a
22959 colon-separated list of host names or IP addresses, optionally also including
22960 port numbers, though the separator can be changed, as described in section
22961 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
22962 item in a &%route_list%& setting for the &(manualroute)& router, as described
22963 in section &<<SECTformatonehostitem>>&.
22965 Fallback hosts can also be specified on routers, which associate them with the
22966 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
22967 &%fallback_hosts%& specified on the transport is used only if the address does
22968 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
22969 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
22970 However, &%hosts_randomize%& does apply to fallback host lists.
22972 If Exim is unable to deliver to any of the hosts for a particular address, and
22973 the errors are not permanent rejections, the address is put on a separate
22974 transport queue with its host list replaced by the fallback hosts, unless the
22975 address was routed via MX records and the current host was in the original MX
22976 list. In that situation, the fallback host list is not used.
22978 Once normal deliveries are complete, the fallback queue is delivered by
22979 re-running the same transports with the new host lists. If several failing
22980 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
22981 copy of the message is sent.
22983 The resolution of the host names on the fallback list is controlled by the
22984 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
22985 both to cases when the host list comes with the address and when it is taken
22986 from &%hosts%&. This option provides a &"use a smart host only if delivery
22990 .option final_timeout smtp time 10m
22991 This is the timeout that applies while waiting for the response to the final
22992 line containing just &"."& that terminates a message. Its value must not be
22995 .option gethostbyname smtp boolean false
22996 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
22997 being used, names are looked up using &[gethostbyname()]&
22998 (or &[getipnodebyname()]& when available)
22999 instead of using the DNS. Of course, that function may in fact use the DNS, but
23000 it may also consult other sources of information such as &_/etc/hosts_&.
23002 .option gnutls_compat_mode smtp boolean unset
23003 This option controls whether GnuTLS is used in compatibility mode in an Exim
23004 server. This reduces security slightly, but improves interworking with older
23005 implementations of TLS.
23007 .option helo_data smtp string&!! "see below"
23008 .cindex "HELO" "argument, setting"
23009 .cindex "EHLO" "argument, setting"
23010 .cindex "LHLO argument setting"
23011 The value of this option is expanded after a connection to a another host has
23012 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
23013 command that starts the outgoing SMTP or LMTP session. The default value of the
23018 During the expansion, the variables &$host$& and &$host_address$& are set to
23019 the identity of the remote host, and the variables &$sending_ip_address$& and
23020 &$sending_port$& are set to the local IP address and port number that are being
23021 used. These variables can be used to generate different values for different
23022 servers or different local IP addresses. For example, if you want the string
23023 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
23024 interface address, you could use this:
23026 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
23027 {$primary_hostname}}
23029 The use of &%helo_data%& applies both to sending messages and when doing
23032 .option hosts smtp "string list&!!" unset
23033 Hosts are associated with an address by a router such as &(dnslookup)&, which
23034 finds the hosts by looking up the address domain in the DNS, or by
23035 &(manualroute)&, which has lists of hosts in its configuration. However,
23036 email addresses can be passed to the &(smtp)& transport by any router, and not
23037 all of them can provide an associated list of hosts.
23039 The &%hosts%& option specifies a list of hosts to be used if the address being
23040 processed does not have any hosts associated with it. The hosts specified by
23041 &%hosts%& are also used, whether or not the address has its own hosts, if
23042 &%hosts_override%& is set.
23044 The string is first expanded, before being interpreted as a colon-separated
23045 list of host names or IP addresses, possibly including port numbers. The
23046 separator may be changed to something other than colon, as described in section
23047 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
23048 item in a &%route_list%& setting for the &(manualroute)& router, as described
23049 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
23050 of the &(manualroute)& router is not available here.
23052 If the expansion fails, delivery is deferred. Unless the failure was caused by
23053 the inability to complete a lookup, the error is logged to the panic log as
23054 well as the main log. Host names are looked up either by searching directly for
23055 address records in the DNS or by calling &[gethostbyname()]& (or
23056 &[getipnodebyname()]& when available), depending on the setting of the
23057 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
23058 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
23061 During delivery, the hosts are tried in order, subject to their retry status,
23062 unless &%hosts_randomize%& is set.
23065 .option hosts_avoid_esmtp smtp "host list&!!" unset
23066 .cindex "ESMTP, avoiding use of"
23067 .cindex "HELO" "forcing use of"
23068 .cindex "EHLO" "avoiding use of"
23069 .cindex "PIPELINING" "avoiding the use of"
23070 This option is for use with broken hosts that announce ESMTP facilities (for
23071 example, PIPELINING) and then fail to implement them properly. When a host
23072 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
23073 start of the SMTP session. This means that it cannot use any of the ESMTP
23074 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
23077 .option hosts_avoid_pipelining smtp "host list&!!" unset
23078 .cindex "PIPELINING" "avoiding the use of"
23079 Exim will not use the SMTP PIPELINING extension when delivering to any host
23080 that matches this list, even if the server host advertises PIPELINING support.
23083 .option hosts_avoid_tls smtp "host list&!!" unset
23084 .cindex "TLS" "avoiding for certain hosts"
23085 Exim will not try to start a TLS session when delivering to any host that
23086 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
23088 .option hosts_verify_avoid_tls smtp "host list&!!" *
23089 .cindex "TLS" "avoiding for certain hosts"
23090 Exim will not try to start a TLS session for a verify callout,
23091 or when delivering in cutthrough mode,
23092 to any host that matches this list.
23093 Note that the default is to not use TLS.
23096 .option hosts_max_try smtp integer 5
23097 .cindex "host" "maximum number to try"
23098 .cindex "limit" "number of hosts tried"
23099 .cindex "limit" "number of MX tried"
23100 .cindex "MX record" "maximum tried"
23101 This option limits the number of IP addresses that are tried for any one
23102 delivery in cases where there are temporary delivery errors. Section
23103 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
23106 .option hosts_max_try_hardlimit smtp integer 50
23107 This is an additional check on the maximum number of IP addresses that Exim
23108 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
23113 .option hosts_nopass_tls smtp "host list&!!" unset
23114 .cindex "TLS" "passing connection"
23115 .cindex "multiple SMTP deliveries"
23116 .cindex "TLS" "multiple message deliveries"
23117 For any host that matches this list, a connection on which a TLS session has
23118 been started will not be passed to a new delivery process for sending another
23119 message on the same connection. See section &<<SECTmulmessam>>& for an
23120 explanation of when this might be needed.
23123 .option hosts_override smtp boolean false
23124 If this option is set and the &%hosts%& option is also set, any hosts that are
23125 attached to the address are ignored, and instead the hosts specified by the
23126 &%hosts%& option are always used. This option does not apply to
23127 &%fallback_hosts%&.
23130 .option hosts_randomize smtp boolean false
23131 .cindex "randomized host list"
23132 .cindex "host" "list of; randomized"
23133 .cindex "fallback" "randomized hosts"
23134 If this option is set, and either the list of hosts is taken from the
23135 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
23136 were not obtained from MX records (this includes fallback hosts from the
23137 router), and were not randomized by the router, the order of trying the hosts
23138 is randomized each time the transport runs. Randomizing the order of a host
23139 list can be used to do crude load sharing.
23141 When &%hosts_randomize%& is true, a host list may be split into groups whose
23142 order is separately randomized. This makes it possible to set up MX-like
23143 behaviour. The boundaries between groups are indicated by an item that is just
23144 &`+`& in the host list. For example:
23146 hosts = host1:host2:host3:+:host4:host5
23148 The order of the first three hosts and the order of the last two hosts is
23149 randomized for each use, but the first three always end up before the last two.
23150 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
23152 .option hosts_require_auth smtp "host list&!!" unset
23153 .cindex "authentication" "required by client"
23154 This option provides a list of servers for which authentication must succeed
23155 before Exim will try to transfer a message. If authentication fails for
23156 servers which are not in this list, Exim tries to send unauthenticated. If
23157 authentication fails for one of these servers, delivery is deferred. This
23158 temporary error is detectable in the retry rules, so it can be turned into a
23159 hard failure if required. See also &%hosts_try_auth%&, and chapter
23160 &<<CHAPSMTPAUTH>>& for details of authentication.
23163 .option hosts_request_ocsp smtp "host list&!!" *
23164 .cindex "TLS" "requiring for certain servers"
23165 Exim will request a Certificate Status on a
23166 TLS session for any host that matches this list.
23167 &%tls_verify_certificates%& should also be set for the transport.
23169 .option hosts_require_ocsp smtp "host list&!!" unset
23170 .cindex "TLS" "requiring for certain servers"
23171 Exim will request, and check for a valid Certificate Status being given, on a
23172 TLS session for any host that matches this list.
23173 &%tls_verify_certificates%& should also be set for the transport.
23175 .option hosts_require_tls smtp "host list&!!" unset
23176 .cindex "TLS" "requiring for certain servers"
23177 Exim will insist on using a TLS session when delivering to any host that
23178 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
23179 &*Note*&: This option affects outgoing mail only. To insist on TLS for
23180 incoming messages, use an appropriate ACL.
23182 .option hosts_try_auth smtp "host list&!!" unset
23183 .cindex "authentication" "optional in client"
23184 This option provides a list of servers to which, provided they announce
23185 authentication support, Exim will attempt to authenticate as a client when it
23186 connects. If authentication fails, Exim will try to transfer the message
23187 unauthenticated. See also &%hosts_require_auth%&, and chapter
23188 &<<CHAPSMTPAUTH>>& for details of authentication.
23190 .option hosts_try_prdr smtp "host list&!!" *
23191 .cindex "PRDR" "enabling, optional in client"
23192 This option provides a list of servers to which, provided they announce
23193 PRDR support, Exim will attempt to negotiate PRDR
23194 for multi-recipient messages.
23195 The option can usually be left as default.
23197 .option interface smtp "string list&!!" unset
23198 .cindex "bind IP address"
23199 .cindex "IP address" "binding"
23201 .vindex "&$host_address$&"
23202 This option specifies which interface to bind to when making an outgoing SMTP
23203 call. The value is an IP address, not an interface name such as
23204 &`eth0`&. Do not confuse this with the interface address that was used when a
23205 message was received, which is in &$received_ip_address$&, formerly known as
23206 &$interface_address$&. The name was changed to minimize confusion with the
23207 outgoing interface address. There is no variable that contains an outgoing
23208 interface address because, unless it is set by this option, its value is
23211 During the expansion of the &%interface%& option the variables &$host$& and
23212 &$host_address$& refer to the host to which a connection is about to be made
23213 during the expansion of the string. Forced expansion failure, or an empty
23214 string result causes the option to be ignored. Otherwise, after expansion, the
23215 string must be a list of IP addresses, colon-separated by default, but the
23216 separator can be changed in the usual way. For example:
23218 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
23220 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
23221 connection. If none of them are the correct type, the option is ignored. If
23222 &%interface%& is not set, or is ignored, the system's IP functions choose which
23223 interface to use if the host has more than one.
23226 .option keepalive smtp boolean true
23227 .cindex "keepalive" "on outgoing connection"
23228 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
23229 connections. When set, it causes the kernel to probe idle connections
23230 periodically, by sending packets with &"old"& sequence numbers. The other end
23231 of the connection should send a acknowledgment if the connection is still okay
23232 or a reset if the connection has been aborted. The reason for doing this is
23233 that it has the beneficial effect of freeing up certain types of connection
23234 that can get stuck when the remote host is disconnected without tidying up the
23235 TCP/IP call properly. The keepalive mechanism takes several hours to detect
23239 .option lmtp_ignore_quota smtp boolean false
23240 .cindex "LMTP" "ignoring quota errors"
23241 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
23242 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
23243 has advertised support for IGNOREQUOTA in its response to the LHLO command.
23245 .option max_rcpt smtp integer 100
23246 .cindex "RCPT" "maximum number of outgoing"
23247 This option limits the number of RCPT commands that are sent in a single
23248 SMTP message transaction. Each set of addresses is treated independently, and
23249 so can cause parallel connections to the same host if &%remote_max_parallel%&
23253 .option multi_domain smtp boolean&!! true
23254 .vindex "&$domain$&"
23255 When this option is set, the &(smtp)& transport can handle a number of
23256 addresses containing a mixture of different domains provided they all resolve
23257 to the same list of hosts. Turning the option off restricts the transport to
23258 handling only one domain at a time. This is useful if you want to use
23259 &$domain$& in an expansion for the transport, because it is set only when there
23260 is a single domain involved in a remote delivery.
23262 It is expanded per-address and can depend on any of
23263 &$address_data$&, &$domain_data$&, &$local_part_data$&,
23264 &$host$&, &$host_address$& and &$host_port$&.
23266 .option port smtp string&!! "see below"
23267 .cindex "port" "sending TCP/IP"
23268 .cindex "TCP/IP" "setting outgoing port"
23269 This option specifies the TCP/IP port on the server to which Exim connects.
23270 &*Note:*& Do not confuse this with the port that was used when a message was
23271 received, which is in &$received_port$&, formerly known as &$interface_port$&.
23272 The name was changed to minimize confusion with the outgoing port. There is no
23273 variable that contains an outgoing port.
23275 If the value of this option begins with a digit it is taken as a port number;
23276 otherwise it is looked up using &[getservbyname()]&. The default value is
23277 normally &"smtp"&, but if &%protocol%& is set to &"lmtp"&, the default is
23278 &"lmtp"&. If the expansion fails, or if a port number cannot be found, delivery
23283 .option protocol smtp string smtp
23284 .cindex "LMTP" "over TCP/IP"
23285 .cindex "ssmtp protocol" "outbound"
23286 .cindex "TLS" "SSL-on-connect outbound"
23288 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
23289 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
23290 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
23291 deliveries into closed message stores. Exim also has support for running LMTP
23292 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
23294 If this option is set to &"smtps"&, the default vaule for the &%port%& option
23295 changes to &"smtps"&, and the transport initiates TLS immediately after
23296 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
23297 The Internet standards bodies strongly discourage use of this mode.
23300 .option retry_include_ip_address smtp boolean&!! true
23301 Exim normally includes both the host name and the IP address in the key it
23302 constructs for indexing retry data after a temporary delivery failure. This
23303 means that when one of several IP addresses for a host is failing, it gets
23304 tried periodically (controlled by the retry rules), but use of the other IP
23305 addresses is not affected.
23307 However, in some dialup environments hosts are assigned a different IP address
23308 each time they connect. In this situation the use of the IP address as part of
23309 the retry key leads to undesirable behaviour. Setting this option false causes
23310 Exim to use only the host name.
23311 Since it is expanded it can be made to depend on the host or domain.
23314 .option serialize_hosts smtp "host list&!!" unset
23315 .cindex "serializing connections"
23316 .cindex "host" "serializing connections"
23317 Because Exim operates in a distributed manner, if several messages for the same
23318 host arrive at around the same time, more than one simultaneous connection to
23319 the remote host can occur. This is not usually a problem except when there is a
23320 slow link between the hosts. In that situation it may be helpful to restrict
23321 Exim to one connection at a time. This can be done by setting
23322 &%serialize_hosts%& to match the relevant hosts.
23324 .cindex "hints database" "serializing deliveries to a host"
23325 Exim implements serialization by means of a hints database in which a record is
23326 written whenever a process connects to one of the restricted hosts. The record
23327 is deleted when the connection is completed. Obviously there is scope for
23328 records to get left lying around if there is a system or program crash. To
23329 guard against this, Exim ignores any records that are more than six hours old.
23331 If you set up this kind of serialization, you should also arrange to delete the
23332 relevant hints database whenever your system reboots. The names of the files
23333 start with &_misc_& and they are kept in the &_spool/db_& directory. There
23334 may be one or two files, depending on the type of DBM in use. The same files
23335 are used for ETRN serialization.
23338 .option size_addition smtp integer 1024
23339 .cindex "SMTP" "SIZE"
23340 .cindex "message" "size issue for transport filter"
23341 .cindex "size" "of message"
23342 .cindex "transport" "filter"
23343 .cindex "filter" "transport filter"
23344 If a remote SMTP server indicates that it supports the SIZE option of the
23345 MAIL command, Exim uses this to pass over the message size at the start of
23346 an SMTP transaction. It adds the value of &%size_addition%& to the value it
23347 sends, to allow for headers and other text that may be added during delivery by
23348 configuration options or in a transport filter. It may be necessary to increase
23349 this if a lot of text is added to messages.
23351 Alternatively, if the value of &%size_addition%& is set negative, it disables
23352 the use of the SIZE option altogether.
23355 .option tls_certificate smtp string&!! unset
23356 .cindex "TLS" "client certificate, location of"
23357 .cindex "certificate" "client, location of"
23359 .vindex "&$host_address$&"
23360 The value of this option must be the absolute path to a file which contains the
23361 client's certificate, for possible use when sending a message over an encrypted
23362 connection. The values of &$host$& and &$host_address$& are set to the name and
23363 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
23366 &*Note*&: This option must be set if you want Exim to be able to use a TLS
23367 certificate when sending messages as a client. The global option of the same
23368 name specifies the certificate for Exim as a server; it is not automatically
23369 assumed that the same certificate should be used when Exim is operating as a
23373 .option tls_crl smtp string&!! unset
23374 .cindex "TLS" "client certificate revocation list"
23375 .cindex "certificate" "revocation list for client"
23376 This option specifies a certificate revocation list. The expanded value must
23377 be the name of a file that contains a CRL in PEM format.
23380 .option tls_dh_min_bits smtp integer 1024
23381 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
23382 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
23383 key agreement is negotiated, the server will provide a large prime number
23384 for use. This option establishes the minimum acceptable size of that number.
23385 If the parameter offered by the server is too small, then the TLS handshake
23388 Only supported when using GnuTLS.
23391 .option tls_privatekey smtp string&!! unset
23392 .cindex "TLS" "client private key, location of"
23394 .vindex "&$host_address$&"
23395 The value of this option must be the absolute path to a file which contains the
23396 client's private key. This is used when sending a message over an encrypted
23397 connection using a client certificate. The values of &$host$& and
23398 &$host_address$& are set to the name and address of the server during the
23399 expansion. If this option is unset, or the expansion is forced to fail, or the
23400 result is an empty string, the private key is assumed to be in the same file as
23401 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
23404 .option tls_require_ciphers smtp string&!! unset
23405 .cindex "TLS" "requiring specific ciphers"
23406 .cindex "cipher" "requiring specific"
23408 .vindex "&$host_address$&"
23409 The value of this option must be a list of permitted cipher suites, for use
23410 when setting up an outgoing encrypted connection. (There is a global option of
23411 the same name for controlling incoming connections.) The values of &$host$& and
23412 &$host_address$& are set to the name and address of the server during the
23413 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
23414 is used in different ways by OpenSSL and GnuTLS (see sections
23415 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
23416 ciphers is a preference order.
23420 .option tls_sni smtp string&!! unset
23421 .cindex "TLS" "Server Name Indication"
23422 .vindex "&$tls_sni$&"
23423 If this option is set then it sets the $tls_out_sni variable and causes any
23424 TLS session to pass this value as the Server Name Indication extension to
23425 the remote side, which can be used by the remote side to select an appropriate
23426 certificate and private key for the session.
23428 See &<<SECTtlssni>>& for more information.
23430 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
23436 .option tls_tempfail_tryclear smtp boolean true
23437 .cindex "4&'xx'& responses" "to STARTTLS"
23438 When the server host is not in &%hosts_require_tls%&, and there is a problem in
23439 setting up a TLS session, this option determines whether or not Exim should try
23440 to deliver the message unencrypted. If it is set false, delivery to the
23441 current host is deferred; if there are other hosts, they are tried. If this
23442 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
23443 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
23444 TLS negotiation fails, Exim closes the current connection (because it is in an
23445 unknown state), opens a new one to the same host, and then tries the delivery
23449 .option tls_try_verify_hosts smtp "host list&!!" unset
23450 .cindex "TLS" "server certificate verification"
23451 .cindex "certificate" "verification of server"
23452 This option gives a list of hosts for which, on encrypted connections,
23453 certificate verification will be tried but need not succeed.
23454 The &%tls_verify_certificates%& option must also be set.
23455 Note that unless the host is in this list
23456 TLS connections will be denied to hosts using self-signed certificates
23457 when &%tls_verify_certificates%& is matched.
23458 The &$tls_out_certificate_verified$& variable is set when
23459 certificate verification succeeds.
23462 .option tls_verify_cert_hostnames smtp "host list&!!" *
23463 .cindex "TLS" "server certificate hostname verification"
23464 .cindex "certificate" "verification of server"
23465 This option give a list of hosts for which,
23466 while verifying the server certificate,
23467 checks will be included on the host name
23468 (note that this will generally be the result of a DNS MX lookup)
23469 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
23470 limited to being the initial component of a 3-or-more component FQDN.
23472 There is no equivalent checking on client certificates.
23475 .option tls_verify_certificates smtp string&!! system
23476 .cindex "TLS" "server certificate verification"
23477 .cindex "certificate" "verification of server"
23479 .vindex "&$host_address$&"
23480 The value of this option must be either the
23482 or the absolute path to
23483 a file or directory containing permitted certificates for servers,
23484 for use when setting up an encrypted connection.
23486 The "system" value for the option will use a location compiled into the SSL library.
23487 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
23488 is taken as empty and an explicit location
23491 The use of a directory for the option value is not avilable for GnuTLS versions
23492 preceding 3.3.6 and a single file must be used.
23494 With OpenSSL the certificates specified
23496 either by file or directory
23497 are added to those given by the system default location.
23499 The values of &$host$& and
23500 &$host_address$& are set to the name and address of the server during the
23501 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
23503 For back-compatability,
23504 if neither tls_verify_hosts nor tls_try_verify_hosts are set
23505 and certificate verification fails the TLS connection is closed.
23508 .option tls_verify_hosts smtp "host list&!!" unset
23509 .cindex "TLS" "server certificate verification"
23510 .cindex "certificate" "verification of server"
23511 This option gives a list of hosts for which. on encrypted connections,
23512 certificate verification must succeed.
23513 The &%tls_verify_certificates%& option must also be set.
23514 If both this option and &%tls_try_verify_hosts%& are unset
23515 operation is as if this option selected all hosts.
23520 .section "How the limits for the number of hosts to try are used" &&&
23522 .cindex "host" "maximum number to try"
23523 .cindex "limit" "hosts; maximum number tried"
23524 There are two options that are concerned with the number of hosts that are
23525 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
23526 &%hosts_max_try_hardlimit%&.
23529 The &%hosts_max_try%& option limits the number of hosts that are tried
23530 for a single delivery. However, despite the term &"host"& in its name, the
23531 option actually applies to each IP address independently. In other words, a
23532 multihomed host is treated as several independent hosts, just as it is for
23535 Many of the larger ISPs have multiple MX records which often point to
23536 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
23537 created as a result of routing one of these domains.
23539 Trying every single IP address on such a long list does not seem sensible; if
23540 several at the top of the list fail, it is reasonable to assume there is some
23541 problem that is likely to affect all of them. Roughly speaking, the value of
23542 &%hosts_max_try%& is the maximum number that are tried before deferring the
23543 delivery. However, the logic cannot be quite that simple.
23545 Firstly, IP addresses that are skipped because their retry times have not
23546 arrived do not count, and in addition, addresses that are past their retry
23547 limits are also not counted, even when they are tried. This means that when
23548 some IP addresses are past their retry limits, more than the value of
23549 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
23550 that all IP addresses are considered before timing out an email address (but
23551 see below for an exception).
23553 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
23554 list to see if there is a subsequent host with a different (higher valued) MX.
23555 If there is, that host is considered next, and the current IP address is used
23556 but not counted. This behaviour helps in the case of a domain with a retry rule
23557 that hardly ever delays any hosts, as is now explained:
23559 Consider the case of a long list of hosts with one MX value, and a few with a
23560 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
23561 hosts at the top of the list are tried at first. With the default retry rule,
23562 which specifies increasing retry times, the higher MX hosts are eventually
23563 tried when those at the top of the list are skipped because they have not
23564 reached their retry times.
23566 However, it is common practice to put a fixed short retry time on domains for
23567 large ISPs, on the grounds that their servers are rarely down for very long.
23568 Unfortunately, these are exactly the domains that tend to resolve to long lists
23569 of hosts. The short retry time means that the lowest MX hosts are tried every
23570 time. The attempts may be in a different order because of random sorting, but
23571 without the special MX check, the higher MX hosts would never be tried until
23572 all the lower MX hosts had timed out (which might be several days), because
23573 there are always some lower MX hosts that have reached their retry times. With
23574 the special check, Exim considers at least one IP address from each MX value at
23575 every delivery attempt, even if the &%hosts_max_try%& limit has already been
23578 The above logic means that &%hosts_max_try%& is not a hard limit, and in
23579 particular, Exim normally eventually tries all the IP addresses before timing
23580 out an email address. When &%hosts_max_try%& was implemented, this seemed a
23581 reasonable thing to do. Recently, however, some lunatic DNS configurations have
23582 been set up with hundreds of IP addresses for some domains. It can
23583 take a very long time indeed for an address to time out in these cases.
23585 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
23586 Exim never tries more than this number of IP addresses; if it hits this limit
23587 and they are all timed out, the email address is bounced, even though not all
23588 possible IP addresses have been tried.
23589 .ecindex IIDsmttra1
23590 .ecindex IIDsmttra2
23596 . ////////////////////////////////////////////////////////////////////////////
23597 . ////////////////////////////////////////////////////////////////////////////
23599 .chapter "Address rewriting" "CHAPrewrite"
23600 .scindex IIDaddrew "rewriting" "addresses"
23601 There are some circumstances in which Exim automatically rewrites domains in
23602 addresses. The two most common are when an address is given without a domain
23603 (referred to as an &"unqualified address"&) or when an address contains an
23604 abbreviated domain that is expanded by DNS lookup.
23606 Unqualified envelope addresses are accepted only for locally submitted
23607 messages, or for messages that are received from hosts matching
23608 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
23609 appropriate. Unqualified addresses in header lines are qualified if they are in
23610 locally submitted messages, or messages from hosts that are permitted to send
23611 unqualified envelope addresses. Otherwise, unqualified addresses in header
23612 lines are neither qualified nor rewritten.
23614 One situation in which Exim does &'not'& automatically rewrite a domain is
23615 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
23616 such a domain should be rewritten using the &"canonical"& name, and some MTAs
23617 do this. The new RFCs do not contain this suggestion.
23620 .section "Explicitly configured address rewriting" "SECID147"
23621 This chapter describes the rewriting rules that can be used in the
23622 main rewrite section of the configuration file, and also in the generic
23623 &%headers_rewrite%& option that can be set on any transport.
23625 Some people believe that configured address rewriting is a Mortal Sin.
23626 Others believe that life is not possible without it. Exim provides the
23627 facility; you do not have to use it.
23629 The main rewriting rules that appear in the &"rewrite"& section of the
23630 configuration file are applied to addresses in incoming messages, both envelope
23631 addresses and addresses in header lines. Each rule specifies the types of
23632 address to which it applies.
23634 Whether or not addresses in header lines are rewritten depends on the origin of
23635 the headers and the type of rewriting. Global rewriting, that is, rewriting
23636 rules from the rewrite section of the configuration file, is applied only to
23637 those headers that were received with the message. Header lines that are added
23638 by ACLs or by a system filter or by individual routers or transports (which
23639 are specific to individual recipient addresses) are not rewritten by the global
23642 Rewriting at transport time, by means of the &%headers_rewrite%& option,
23643 applies all headers except those added by routers and transports. That is, as
23644 well as the headers that were received with the message, it also applies to
23645 headers that were added by an ACL or a system filter.
23648 In general, rewriting addresses from your own system or domain has some
23649 legitimacy. Rewriting other addresses should be done only with great care and
23650 in special circumstances. The author of Exim believes that rewriting should be
23651 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
23652 Although it can sometimes be used as a routing tool, this is very strongly
23655 There are two commonly encountered circumstances where rewriting is used, as
23656 illustrated by these examples:
23659 The company whose domain is &'hitch.fict.example'& has a number of hosts that
23660 exchange mail with each other behind a firewall, but there is only a single
23661 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
23662 &'hitch.fict.example'& when sending mail off-site.
23664 A host rewrites the local parts of its own users so that, for example,
23665 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
23670 .section "When does rewriting happen?" "SECID148"
23671 .cindex "rewriting" "timing of"
23672 .cindex "&ACL;" "rewriting addresses in"
23673 Configured address rewriting can take place at several different stages of a
23674 message's processing.
23676 .vindex "&$sender_address$&"
23677 At the start of an ACL for MAIL, the sender address may have been rewritten
23678 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
23679 ordinary rewrite rules have yet been applied. If, however, the sender address
23680 is verified in the ACL, it is rewritten before verification, and remains
23681 rewritten thereafter. The subsequent value of &$sender_address$& is the
23682 rewritten address. This also applies if sender verification happens in a
23683 RCPT ACL. Otherwise, when the sender address is not verified, it is
23684 rewritten as soon as a message's header lines have been received.
23686 .vindex "&$domain$&"
23687 .vindex "&$local_part$&"
23688 Similarly, at the start of an ACL for RCPT, the current recipient's address
23689 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
23690 rewrite rules have yet been applied to it. However, the behaviour is different
23691 from the sender address when a recipient is verified. The address is rewritten
23692 for the verification, but the rewriting is not remembered at this stage. The
23693 value of &$local_part$& and &$domain$& after verification are always the same
23694 as they were before (that is, they contain the unrewritten &-- except for
23695 SMTP-time rewriting &-- address).
23697 As soon as a message's header lines have been received, all the envelope
23698 recipient addresses are permanently rewritten, and rewriting is also applied to
23699 the addresses in the header lines (if configured). This happens before adding
23700 any header lines that were specified in MAIL or RCPT ACLs, and
23701 .cindex "&[local_scan()]& function" "address rewriting; timing of"
23702 before the DATA ACL and &[local_scan()]& functions are run.
23704 When an address is being routed, either for delivery or for verification,
23705 rewriting is applied immediately to child addresses that are generated by
23706 redirection, unless &%no_rewrite%& is set on the router.
23708 .cindex "envelope sender" "rewriting at transport time"
23709 .cindex "rewriting" "at transport time"
23710 .cindex "header lines" "rewriting at transport time"
23711 At transport time, additional rewriting of addresses in header lines can be
23712 specified by setting the generic &%headers_rewrite%& option on a transport.
23713 This option contains rules that are identical in form to those in the rewrite
23714 section of the configuration file. They are applied to the original message
23715 header lines and any that were added by ACLs or a system filter. They are not
23716 applied to header lines that are added by routers or the transport.
23718 The outgoing envelope sender can be rewritten by means of the &%return_path%&
23719 transport option. However, it is not possible to rewrite envelope recipients at
23725 .section "Testing the rewriting rules that apply on input" "SECID149"
23726 .cindex "rewriting" "testing"
23727 .cindex "testing" "rewriting"
23728 Exim's input rewriting configuration appears in a part of the run time
23729 configuration file headed by &"begin rewrite"&. It can be tested by the
23730 &%-brw%& command line option. This takes an address (which can be a full RFC
23731 2822 address) as its argument. The output is a list of how the address would be
23732 transformed by the rewriting rules for each of the different places it might
23733 appear in an incoming message, that is, for each different header and for the
23734 envelope sender and recipient fields. For example,
23736 exim -brw ph10@exim.workshop.example
23738 might produce the output
23740 sender: Philip.Hazel@exim.workshop.example
23741 from: Philip.Hazel@exim.workshop.example
23742 to: ph10@exim.workshop.example
23743 cc: ph10@exim.workshop.example
23744 bcc: ph10@exim.workshop.example
23745 reply-to: Philip.Hazel@exim.workshop.example
23746 env-from: Philip.Hazel@exim.workshop.example
23747 env-to: ph10@exim.workshop.example
23749 which shows that rewriting has been set up for that address when used in any of
23750 the source fields, but not when it appears as a recipient address. At the
23751 present time, there is no equivalent way of testing rewriting rules that are
23752 set for a particular transport.
23755 .section "Rewriting rules" "SECID150"
23756 .cindex "rewriting" "rules"
23757 The rewrite section of the configuration file consists of lines of rewriting
23760 <&'source pattern'&> <&'replacement'&> <&'flags'&>
23762 Rewriting rules that are specified for the &%headers_rewrite%& generic
23763 transport option are given as a colon-separated list. Each item in the list
23764 takes the same form as a line in the main rewriting configuration (except that
23765 any colons must be doubled, of course).
23767 The formats of source patterns and replacement strings are described below.
23768 Each is terminated by white space, unless enclosed in double quotes, in which
23769 case normal quoting conventions apply inside the quotes. The flags are single
23770 characters which may appear in any order. Spaces and tabs between them are
23773 For each address that could potentially be rewritten, the rules are scanned in
23774 order, and replacements for the address from earlier rules can themselves be
23775 replaced by later rules (but see the &"q"& and &"R"& flags).
23777 The order in which addresses are rewritten is undefined, may change between
23778 releases, and must not be relied on, with one exception: when a message is
23779 received, the envelope sender is always rewritten first, before any header
23780 lines are rewritten. For example, the replacement string for a rewrite of an
23781 address in &'To:'& must not assume that the message's address in &'From:'& has
23782 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
23783 that the envelope sender has already been rewritten.
23785 .vindex "&$domain$&"
23786 .vindex "&$local_part$&"
23787 The variables &$local_part$& and &$domain$& can be used in the replacement
23788 string to refer to the address that is being rewritten. Note that lookup-driven
23789 rewriting can be done by a rule of the form
23793 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
23794 refer to the address that is being rewritten.
23797 .section "Rewriting patterns" "SECID151"
23798 .cindex "rewriting" "patterns"
23799 .cindex "address list" "in a rewriting pattern"
23800 The source pattern in a rewriting rule is any item which may appear in an
23801 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
23802 single-item address list, which means that it is expanded before being tested
23803 against the address. As always, if you use a regular expression as a pattern,
23804 you must take care to escape dollar and backslash characters, or use the &`\N`&
23805 facility to suppress string expansion within the regular expression.
23807 Domains in patterns should be given in lower case. Local parts in patterns are
23808 case-sensitive. If you want to do case-insensitive matching of local parts, you
23809 can use a regular expression that starts with &`^(?i)`&.
23811 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
23812 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
23813 depending on the type of match which occurred. These can be used in the
23814 replacement string to insert portions of the incoming address. &$0$& always
23815 refers to the complete incoming address. When a regular expression is used, the
23816 numerical variables are set from its capturing subexpressions. For other types
23817 of pattern they are set as follows:
23820 If a local part or domain starts with an asterisk, the numerical variables
23821 refer to the character strings matched by asterisks, with &$1$& associated with
23822 the first asterisk, and &$2$& with the second, if present. For example, if the
23825 *queen@*.fict.example
23827 is matched against the address &'hearts-queen@wonderland.fict.example'& then
23829 $0 = hearts-queen@wonderland.fict.example
23833 Note that if the local part does not start with an asterisk, but the domain
23834 does, it is &$1$& that contains the wild part of the domain.
23837 If the domain part of the pattern is a partial lookup, the wild and fixed parts
23838 of the domain are placed in the next available numerical variables. Suppose,
23839 for example, that the address &'foo@bar.baz.example'& is processed by a
23840 rewriting rule of the form
23842 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
23844 and the key in the file that matches the domain is &`*.baz.example`&. Then
23850 If the address &'foo@baz.example'& is looked up, this matches the same
23851 wildcard file entry, and in this case &$2$& is set to the empty string, but
23852 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
23853 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
23854 whole domain. For non-partial domain lookups, no numerical variables are set.
23858 .section "Rewriting replacements" "SECID152"
23859 .cindex "rewriting" "replacements"
23860 If the replacement string for a rule is a single asterisk, addresses that
23861 match the pattern and the flags are &'not'& rewritten, and no subsequent
23862 rewriting rules are scanned. For example,
23864 hatta@lookingglass.fict.example * f
23866 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
23869 .vindex "&$domain$&"
23870 .vindex "&$local_part$&"
23871 If the replacement string is not a single asterisk, it is expanded, and must
23872 yield a fully qualified address. Within the expansion, the variables
23873 &$local_part$& and &$domain$& refer to the address that is being rewritten.
23874 Any letters they contain retain their original case &-- they are not lower
23875 cased. The numerical variables are set up according to the type of pattern that
23876 matched the address, as described above. If the expansion is forced to fail by
23877 the presence of &"fail"& in a conditional or lookup item, rewriting by the
23878 current rule is abandoned, but subsequent rules may take effect. Any other
23879 expansion failure causes the entire rewriting operation to be abandoned, and an
23880 entry written to the panic log.
23884 .section "Rewriting flags" "SECID153"
23885 There are three different kinds of flag that may appear on rewriting rules:
23888 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
23891 A flag that specifies rewriting at SMTP time: S.
23893 Flags that control the rewriting process: Q, q, R, w.
23896 For rules that are part of the &%headers_rewrite%& generic transport option,
23897 E, F, T, and S are not permitted.
23901 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
23903 .cindex "rewriting" "flags"
23904 If none of the following flag letters, nor the &"S"& flag (see section
23905 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
23906 and to both the sender and recipient fields of the envelope, whereas a
23907 transport-time rewriting rule just applies to all headers. Otherwise, the
23908 rewriting rule is skipped unless the relevant addresses are being processed.
23910 &`E`& rewrite all envelope fields
23911 &`F`& rewrite the envelope From field
23912 &`T`& rewrite the envelope To field
23913 &`b`& rewrite the &'Bcc:'& header
23914 &`c`& rewrite the &'Cc:'& header
23915 &`f`& rewrite the &'From:'& header
23916 &`h`& rewrite all headers
23917 &`r`& rewrite the &'Reply-To:'& header
23918 &`s`& rewrite the &'Sender:'& header
23919 &`t`& rewrite the &'To:'& header
23921 "All headers" means all of the headers listed above that can be selected
23922 individually, plus their &'Resent-'& versions. It does not include
23923 other headers such as &'Subject:'& etc.
23925 You should be particularly careful about rewriting &'Sender:'& headers, and
23926 restrict this to special known cases in your own domains.
23929 .section "The SMTP-time rewriting flag" "SECTrewriteS"
23930 .cindex "SMTP" "rewriting malformed addresses"
23931 .cindex "RCPT" "rewriting argument of"
23932 .cindex "MAIL" "rewriting argument of"
23933 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
23934 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
23935 before any other processing; even before syntax checking. The pattern is
23936 required to be a regular expression, and it is matched against the whole of the
23937 data for the command, including any surrounding angle brackets.
23939 .vindex "&$domain$&"
23940 .vindex "&$local_part$&"
23941 This form of rewrite rule allows for the handling of addresses that are not
23942 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
23943 input). Because the input is not required to be a syntactically valid address,
23944 the variables &$local_part$& and &$domain$& are not available during the
23945 expansion of the replacement string. The result of rewriting replaces the
23946 original address in the MAIL or RCPT command.
23949 .section "Flags controlling the rewriting process" "SECID155"
23950 There are four flags which control the way the rewriting process works. These
23951 take effect only when a rule is invoked, that is, when the address is of the
23952 correct type (matches the flags) and matches the pattern:
23955 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
23956 unqualified local part. It is qualified with &%qualify_recipient%&. In the
23957 absence of &"Q"& the rewritten address must always include a domain.
23959 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
23960 even if no rewriting actually takes place because of a &"fail"& in the
23961 expansion. The &"q"& flag is not effective if the address is of the wrong type
23962 (does not match the flags) or does not match the pattern.
23964 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
23965 address, up to ten times. It can be combined with the &"q"& flag, to stop
23966 rewriting once it fails to match (after at least one successful rewrite).
23968 .cindex "rewriting" "whole addresses"
23969 When an address in a header is rewritten, the rewriting normally applies only
23970 to the working part of the address, with any comments and RFC 2822 &"phrase"&
23971 left unchanged. For example, rewriting might change
23973 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
23977 From: Ford Prefect <prefectf@hitch.fict.example>
23980 Sometimes there is a need to replace the whole address item, and this can be
23981 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
23982 causes an address in a header line to be rewritten, the entire address is
23983 replaced, not just the working part. The replacement must be a complete RFC
23984 2822 address, including the angle brackets if necessary. If text outside angle
23985 brackets contains a character whose value is greater than 126 or less than 32
23986 (except for tab), the text is encoded according to RFC 2047. The character set
23987 is taken from &%headers_charset%&, which defaults to ISO-8859-1.
23989 When the &"w"& flag is set on a rule that causes an envelope address to be
23990 rewritten, all but the working part of the replacement address is discarded.
23994 .section "Rewriting examples" "SECID156"
23995 Here is an example of the two common rewriting paradigms:
23997 *@*.hitch.fict.example $1@hitch.fict.example
23998 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
23999 {$value}fail}@hitch.fict.example bctfrF
24001 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
24002 the string expansion to fail if the lookup does not succeed. In this context it
24003 has the effect of leaving the original address unchanged, but Exim goes on to
24004 consider subsequent rewriting rules, if any, because the &"q"& flag is not
24005 present in that rule. An alternative to &"fail"& would be to supply &$1$&
24006 explicitly, which would cause the rewritten address to be the same as before,
24007 at the cost of a small bit of processing. Not supplying either of these is an
24008 error, since the rewritten address would then contain no local part.
24010 The first example above replaces the domain with a superior, more general
24011 domain. This may not be desirable for certain local parts. If the rule
24013 root@*.hitch.fict.example *
24015 were inserted before the first rule, rewriting would be suppressed for the
24016 local part &'root'& at any domain ending in &'hitch.fict.example'&.
24018 Rewriting can be made conditional on a number of tests, by making use of
24019 &${if$& in the expansion item. For example, to apply a rewriting rule only to
24020 messages that originate outside the local host:
24022 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
24023 {$1@hitch.fict.example}fail}"
24025 The replacement string is quoted in this example because it contains white
24028 .cindex "rewriting" "bang paths"
24029 .cindex "bang paths" "rewriting"
24030 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
24031 an address it treats it as an unqualified local part which it qualifies with
24032 the local qualification domain (if the source of the message is local or if the
24033 remote host is permitted to send unqualified addresses). Rewriting can
24034 sometimes be used to handle simple bang paths with a fixed number of
24035 components. For example, the rule
24037 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
24039 rewrites a two-component bang path &'host.name!user'& as the domain address
24040 &'user@host.name'&. However, there is a security implication in using this as
24041 a global rewriting rule for envelope addresses. It can provide a backdoor
24042 method for using your system as a relay, because the incoming addresses appear
24043 to be local. If the bang path addresses are received via SMTP, it is safer to
24044 use the &"S"& flag to rewrite them as they are received, so that relay checking
24045 can be done on the rewritten addresses.
24052 . ////////////////////////////////////////////////////////////////////////////
24053 . ////////////////////////////////////////////////////////////////////////////
24055 .chapter "Retry configuration" "CHAPretry"
24056 .scindex IIDretconf1 "retry" "configuration, description of"
24057 .scindex IIDregconf2 "configuration file" "retry section"
24058 The &"retry"& section of the runtime configuration file contains a list of
24059 retry rules that control how often Exim tries to deliver messages that cannot
24060 be delivered at the first attempt. If there are no retry rules (the section is
24061 empty or not present), there are no retries. In this situation, temporary
24062 errors are treated as permanent. The default configuration contains a single,
24063 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
24064 line option can be used to test which retry rule will be used for a given
24065 address, domain and error.
24067 The most common cause of retries is temporary failure to deliver to a remote
24068 host because the host is down, or inaccessible because of a network problem.
24069 Exim's retry processing in this case is applied on a per-host (strictly, per IP
24070 address) basis, not on a per-message basis. Thus, if one message has recently
24071 been delayed, delivery of a new message to the same host is not immediately
24072 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
24073 log selector is set, the message
24074 .cindex "retry" "time not reached"
24075 &"retry time not reached"& is written to the main log whenever a delivery is
24076 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
24077 the handling of errors during remote deliveries.
24079 Retry processing applies to routing as well as to delivering, except as covered
24080 in the next paragraph. The retry rules do not distinguish between these
24081 actions. It is not possible, for example, to specify different behaviour for
24082 failures to route the domain &'snark.fict.example'& and failures to deliver to
24083 the host &'snark.fict.example'&. I didn't think anyone would ever need this
24084 added complication, so did not implement it. However, although they share the
24085 same retry rule, the actual retry times for routing and transporting a given
24086 domain are maintained independently.
24088 When a delivery is not part of a queue run (typically an immediate delivery on
24089 receipt of a message), the routers are always run, and local deliveries are
24090 always attempted, even if retry times are set for them. This makes for better
24091 behaviour if one particular message is causing problems (for example, causing
24092 quota overflow, or provoking an error in a filter file). If such a delivery
24093 suffers a temporary failure, the retry data is updated as normal, and
24094 subsequent delivery attempts from queue runs occur only when the retry time for
24095 the local address is reached.
24097 .section "Changing retry rules" "SECID157"
24098 If you change the retry rules in your configuration, you should consider
24099 whether or not to delete the retry data that is stored in Exim's spool area in
24100 files with names like &_db/retry_&. Deleting any of Exim's hints files is
24101 always safe; that is why they are called &"hints"&.
24103 The hints retry data contains suggested retry times based on the previous
24104 rules. In the case of a long-running problem with a remote host, it might
24105 record the fact that the host has timed out. If your new rules increase the
24106 timeout time for such a host, you should definitely remove the old retry data
24107 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
24108 messages that it should now be retaining.
24112 .section "Format of retry rules" "SECID158"
24113 .cindex "retry" "rules"
24114 Each retry rule occupies one line and consists of three or four parts,
24115 separated by white space: a pattern, an error name, an optional list of sender
24116 addresses, and a list of retry parameters. The pattern and sender lists must be
24117 enclosed in double quotes if they contain white space. The rules are searched
24118 in order until one is found where the pattern, error name, and sender list (if
24119 present) match the failing host or address, the error that occurred, and the
24120 message's sender, respectively.
24123 The pattern is any single item that may appear in an address list (see section
24124 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
24125 which means that it is expanded before being tested against the address that
24126 has been delayed. A negated address list item is permitted. Address
24127 list processing treats a plain domain name as if it were preceded by &"*@"&,
24128 which makes it possible for many retry rules to start with just a domain. For
24131 lookingglass.fict.example * F,24h,30m;
24133 provides a rule for any address in the &'lookingglass.fict.example'& domain,
24136 alice@lookingglass.fict.example * F,24h,30m;
24138 applies only to temporary failures involving the local part &%alice%&.
24139 In practice, almost all rules start with a domain name pattern without a local
24142 .cindex "regular expressions" "in retry rules"
24143 &*Warning*&: If you use a regular expression in a retry rule pattern, it
24144 must match a complete address, not just a domain, because that is how regular
24145 expressions work in address lists.
24147 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
24148 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
24152 .section "Choosing which retry rule to use for address errors" "SECID159"
24153 When Exim is looking for a retry rule after a routing attempt has failed (for
24154 example, after a DNS timeout), each line in the retry configuration is tested
24155 against the complete address only if &%retry_use_local_part%& is set for the
24156 router. Otherwise, only the domain is used, except when matching against a
24157 regular expression, when the local part of the address is replaced with &"*"&.
24158 A domain on its own can match a domain pattern, or a pattern that starts with
24159 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
24160 &%check_local_user%& is true, and false for other routers.
24162 Similarly, when Exim is looking for a retry rule after a local delivery has
24163 failed (for example, after a mailbox full error), each line in the retry
24164 configuration is tested against the complete address only if
24165 &%retry_use_local_part%& is set for the transport (it defaults true for all
24168 .cindex "4&'xx'& responses" "retry rules for"
24169 However, when Exim is looking for a retry rule after a remote delivery attempt
24170 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
24171 whole address is always used as the key when searching the retry rules. The
24172 rule that is found is used to create a retry time for the combination of the
24173 failing address and the message's sender. It is the combination of sender and
24174 recipient that is delayed in subsequent queue runs until its retry time is
24175 reached. You can delay the recipient without regard to the sender by setting
24176 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
24177 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
24182 .section "Choosing which retry rule to use for host and message errors" &&&
24184 For a temporary error that is not related to an individual address (for
24185 example, a connection timeout), each line in the retry configuration is checked
24186 twice. First, the name of the remote host is used as a domain name (preceded by
24187 &"*@"& when matching a regular expression). If this does not match the line,
24188 the domain from the email address is tried in a similar fashion. For example,
24189 suppose the MX records for &'a.b.c.example'& are
24191 a.b.c.example MX 5 x.y.z.example
24195 and the retry rules are
24197 p.q.r.example * F,24h,30m;
24198 a.b.c.example * F,4d,45m;
24200 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
24201 first rule matches neither the host nor the domain, so Exim looks at the second
24202 rule. This does not match the host, but it does match the domain, so it is used
24203 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
24204 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
24205 first retry rule is used, because it matches the host.
24207 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
24208 first rule to determine retry times, but for all the other hosts for the domain
24209 &'a.b.c.example'&, the second rule is used. The second rule is also used if
24210 routing to &'a.b.c.example'& suffers a temporary failure.
24212 &*Note*&: The host name is used when matching the patterns, not its IP address.
24213 However, if a message is routed directly to an IP address without the use of a
24214 host name, for example, if a &(manualroute)& router contains a setting such as:
24216 route_list = *.a.example 192.168.34.23
24218 then the &"host name"& that is used when searching for a retry rule is the
24219 textual form of the IP address.
24221 .section "Retry rules for specific errors" "SECID161"
24222 .cindex "retry" "specific errors; specifying"
24223 The second field in a retry rule is the name of a particular error, or an
24224 asterisk, which matches any error. The errors that can be tested for are:
24227 .vitem &%auth_failed%&
24228 Authentication failed when trying to send to a host in the
24229 &%hosts_require_auth%& list in an &(smtp)& transport.
24231 .vitem &%data_4xx%&
24232 A 4&'xx'& error was received for an outgoing DATA command, either immediately
24233 after the command, or after sending the message's data.
24235 .vitem &%mail_4xx%&
24236 A 4&'xx'& error was received for an outgoing MAIL command.
24238 .vitem &%rcpt_4xx%&
24239 A 4&'xx'& error was received for an outgoing RCPT command.
24242 For the three 4&'xx'& errors, either the first or both of the x's can be given
24243 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
24244 recognize 452 errors given to RCPT commands for addresses in a certain domain,
24245 and have retries every ten minutes with a one-hour timeout, you could set up a
24246 retry rule of this form:
24248 the.domain.name rcpt_452 F,1h,10m
24250 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
24251 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
24254 .vitem &%lost_connection%&
24255 A server unexpectedly closed the SMTP connection. There may, of course,
24256 legitimate reasons for this (host died, network died), but if it repeats a lot
24257 for the same host, it indicates something odd.
24259 .vitem &%refused_MX%&
24260 A connection to a host obtained from an MX record was refused.
24262 .vitem &%refused_A%&
24263 A connection to a host not obtained from an MX record was refused.
24266 A connection was refused.
24268 .vitem &%timeout_connect_MX%&
24269 A connection attempt to a host obtained from an MX record timed out.
24271 .vitem &%timeout_connect_A%&
24272 A connection attempt to a host not obtained from an MX record timed out.
24274 .vitem &%timeout_connect%&
24275 A connection attempt timed out.
24277 .vitem &%timeout_MX%&
24278 There was a timeout while connecting or during an SMTP session with a host
24279 obtained from an MX record.
24281 .vitem &%timeout_A%&
24282 There was a timeout while connecting or during an SMTP session with a host not
24283 obtained from an MX record.
24286 There was a timeout while connecting or during an SMTP session.
24288 .vitem &%tls_required%&
24289 The server was required to use TLS (it matched &%hosts_require_tls%& in the
24290 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
24291 to STARTTLS, or there was a problem setting up the TLS connection.
24294 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
24297 .vitem &%quota_%&<&'time'&>
24298 .cindex "quota" "error testing in retry rule"
24299 .cindex "retry" "quota error testing"
24300 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
24301 transport, and the mailbox has not been accessed for <&'time'&>. For example,
24302 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
24306 .cindex "mailbox" "time of last read"
24307 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
24308 timeouts when the mailbox is full and is not being read by its owner. Ideally,
24309 it should be based on the last time that the user accessed the mailbox.
24310 However, it is not always possible to determine this. Exim uses the following
24314 If the mailbox is a single file, the time of last access (the &"atime"&) is
24315 used. As no new messages are being delivered (because the mailbox is over
24316 quota), Exim does not access the file, so this is the time of last user access.
24318 .cindex "maildir format" "time of last read"
24319 For a maildir delivery, the time of last modification of the &_new_&
24320 subdirectory is used. As the mailbox is over quota, no new files are created in
24321 the &_new_& subdirectory, because no new messages are being delivered. Any
24322 change to the &_new_& subdirectory is therefore assumed to be the result of an
24323 MUA moving a new message to the &_cur_& directory when it is first read. The
24324 time that is used is therefore the last time that the user read a new message.
24326 For other kinds of multi-file mailbox, the time of last access cannot be
24327 obtained, so a retry rule that uses this type of error field is never matched.
24330 The quota errors apply both to system-enforced quotas and to Exim's own quota
24331 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
24332 when a local delivery is deferred because a partition is full (the ENOSPC
24337 .section "Retry rules for specified senders" "SECID162"
24338 .cindex "retry" "rules; sender-specific"
24339 You can specify retry rules that apply only when the failing message has a
24340 specific sender. In particular, this can be used to define retry rules that
24341 apply only to bounce messages. The third item in a retry rule can be of this
24344 &`senders=`&<&'address list'&>
24346 The retry timings themselves are then the fourth item. For example:
24348 * rcpt_4xx senders=: F,1h,30m
24350 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
24351 host. If the address list contains white space, it must be enclosed in quotes.
24354 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
24356 &*Warning*&: This facility can be unhelpful if it is used for host errors
24357 (which do not depend on the recipient). The reason is that the sender is used
24358 only to match the retry rule. Once the rule has been found for a host error,
24359 its contents are used to set a retry time for the host, and this will apply to
24360 all messages, not just those with specific senders.
24362 When testing retry rules using &%-brt%&, you can supply a sender using the
24363 &%-f%& command line option, like this:
24365 exim -f "" -brt user@dom.ain
24367 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
24368 list is never matched.
24374 .section "Retry parameters" "SECID163"
24375 .cindex "retry" "parameters in rules"
24376 The third (or fourth, if a senders list is present) field in a retry rule is a
24377 sequence of retry parameter sets, separated by semicolons. Each set consists of
24379 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
24381 The letter identifies the algorithm for computing a new retry time; the cutoff
24382 time is the time beyond which this algorithm no longer applies, and the
24383 arguments vary the algorithm's action. The cutoff time is measured from the
24384 time that the first failure for the domain (combined with the local part if
24385 relevant) was detected, not from the time the message was received.
24387 .cindex "retry" "algorithms"
24388 .cindex "retry" "fixed intervals"
24389 .cindex "retry" "increasing intervals"
24390 .cindex "retry" "random intervals"
24391 The available algorithms are:
24394 &'F'&: retry at fixed intervals. There is a single time parameter specifying
24397 &'G'&: retry at geometrically increasing intervals. The first argument
24398 specifies a starting value for the interval, and the second a multiplier, which
24399 is used to increase the size of the interval at each retry.
24401 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
24402 retry, the previous interval is multiplied by the factor in order to get a
24403 maximum for the next interval. The minimum interval is the first argument of
24404 the parameter, and an actual interval is chosen randomly between them. Such a
24405 rule has been found to be helpful in cluster configurations when all the
24406 members of the cluster restart at once, and may therefore synchronize their
24407 queue processing times.
24410 When computing the next retry time, the algorithm definitions are scanned in
24411 order until one whose cutoff time has not yet passed is reached. This is then
24412 used to compute a new retry time that is later than the current time. In the
24413 case of fixed interval retries, this simply means adding the interval to the
24414 current time. For geometrically increasing intervals, retry intervals are
24415 computed from the rule's parameters until one that is greater than the previous
24416 interval is found. The main configuration variable
24417 .cindex "limit" "retry interval"
24418 .cindex "retry" "interval, maximum"
24419 .oindex "&%retry_interval_max%&"
24420 &%retry_interval_max%& limits the maximum interval between retries. It
24421 cannot be set greater than &`24h`&, which is its default value.
24423 A single remote domain may have a number of hosts associated with it, and each
24424 host may have more than one IP address. Retry algorithms are selected on the
24425 basis of the domain name, but are applied to each IP address independently. If,
24426 for example, a host has two IP addresses and one is unusable, Exim will
24427 generate retry times for it and will not try to use it until its next retry
24428 time comes. Thus the good IP address is likely to be tried first most of the
24431 .cindex "hints database" "use for retrying"
24432 Retry times are hints rather than promises. Exim does not make any attempt to
24433 run deliveries exactly at the computed times. Instead, a queue runner process
24434 starts delivery processes for delayed messages periodically, and these attempt
24435 new deliveries only for those addresses that have passed their next retry time.
24436 If a new message arrives for a deferred address, an immediate delivery attempt
24437 occurs only if the address has passed its retry time. In the absence of new
24438 messages, the minimum time between retries is the interval between queue runner
24439 processes. There is not much point in setting retry times of five minutes if
24440 your queue runners happen only once an hour, unless there are a significant
24441 number of incoming messages (which might be the case on a system that is
24442 sending everything to a smart host, for example).
24444 The data in the retry hints database can be inspected by using the
24445 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
24446 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
24447 &'exinext'& utility script can be used to find out what the next retry times
24448 are for the hosts associated with a particular mail domain, and also for local
24449 deliveries that have been deferred.
24452 .section "Retry rule examples" "SECID164"
24453 Here are some example retry rules:
24455 alice@wonderland.fict.example quota_5d F,7d,3h
24456 wonderland.fict.example quota_5d
24457 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
24458 lookingglass.fict.example * F,24h,30m;
24459 * refused_A F,2h,20m;
24460 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
24462 The first rule sets up special handling for mail to
24463 &'alice@wonderland.fict.example'& when there is an over-quota error and the
24464 mailbox has not been read for at least 5 days. Retries continue every three
24465 hours for 7 days. The second rule handles over-quota errors for all other local
24466 parts at &'wonderland.fict.example'&; the absence of a local part has the same
24467 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
24468 fail are bounced immediately if the mailbox has not been read for at least 5
24471 The third rule handles all other errors at &'wonderland.fict.example'&; retries
24472 happen every 15 minutes for an hour, then with geometrically increasing
24473 intervals until two days have passed since a delivery first failed. After the
24474 first hour there is a delay of one hour, then two hours, then four hours, and
24475 so on (this is a rather extreme example).
24477 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
24478 They happen every 30 minutes for 24 hours only. The remaining two rules handle
24479 all other domains, with special action for connection refusal from hosts that
24480 were not obtained from an MX record.
24482 The final rule in a retry configuration should always have asterisks in the
24483 first two fields so as to provide a general catch-all for any addresses that do
24484 not have their own special handling. This example tries every 15 minutes for 2
24485 hours, then with intervals starting at one hour and increasing by a factor of
24486 1.5 up to 16 hours, then every 8 hours up to 5 days.
24490 .section "Timeout of retry data" "SECID165"
24491 .cindex "timeout" "of retry data"
24492 .oindex "&%retry_data_expire%&"
24493 .cindex "hints database" "data expiry"
24494 .cindex "retry" "timeout of data"
24495 Exim timestamps the data that it writes to its retry hints database. When it
24496 consults the data during a delivery it ignores any that is older than the value
24497 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
24498 been tried for 7 days, Exim will try to deliver to it immediately a message
24499 arrives, and if that fails, it will calculate a retry time as if it were
24500 failing for the first time.
24502 This improves the behaviour for messages routed to rarely-used hosts such as MX
24503 backups. If such a host was down at one time, and happens to be down again when
24504 Exim tries a month later, using the old retry data would imply that it had been
24505 down all the time, which is not a justified assumption.
24507 If a host really is permanently dead, this behaviour causes a burst of retries
24508 every now and again, but only if messages routed to it are rare. If there is a
24509 message at least once every 7 days the retry data never expires.
24514 .section "Long-term failures" "SECID166"
24515 .cindex "delivery failure, long-term"
24516 .cindex "retry" "after long-term failure"
24517 Special processing happens when an email address has been failing for so long
24518 that the cutoff time for the last algorithm is reached. For example, using the
24519 default retry rule:
24521 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
24523 the cutoff time is four days. Reaching the retry cutoff is independent of how
24524 long any specific message has been failing; it is the length of continuous
24525 failure for the recipient address that counts.
24527 When the cutoff time is reached for a local delivery, or for all the IP
24528 addresses associated with a remote delivery, a subsequent delivery failure
24529 causes Exim to give up on the address, and a bounce message is generated.
24530 In order to cater for new messages that use the failing address, a next retry
24531 time is still computed from the final algorithm, and is used as follows:
24533 For local deliveries, one delivery attempt is always made for any subsequent
24534 messages. If this delivery fails, the address fails immediately. The
24535 post-cutoff retry time is not used.
24537 If the delivery is remote, there are two possibilities, controlled by the
24538 .oindex "&%delay_after_cutoff%&"
24539 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
24540 default. Until the post-cutoff retry time for one of the IP addresses is
24541 reached, the failing email address is bounced immediately, without a delivery
24542 attempt taking place. After that time, one new delivery attempt is made to
24543 those IP addresses that are past their retry times, and if that still fails,
24544 the address is bounced and new retry times are computed.
24546 In other words, when all the hosts for a given email address have been failing
24547 for a long time, Exim bounces rather then defers until one of the hosts' retry
24548 times is reached. Then it tries once, and bounces if that attempt fails. This
24549 behaviour ensures that few resources are wasted in repeatedly trying to deliver
24550 to a broken destination, but if the host does recover, Exim will eventually
24553 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
24554 addresses are past their final cutoff time, Exim tries to deliver to those IP
24555 addresses that have not been tried since the message arrived. If there are
24556 no suitable IP addresses, or if they all fail, the address is bounced. In other
24557 words, it does not delay when a new message arrives, but tries the expired
24558 addresses immediately, unless they have been tried since the message arrived.
24559 If there is a continuous stream of messages for the failing domains, setting
24560 &%delay_after_cutoff%& false means that there will be many more attempts to
24561 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
24564 .section "Deliveries that work intermittently" "SECID167"
24565 .cindex "retry" "intermittently working deliveries"
24566 Some additional logic is needed to cope with cases where a host is
24567 intermittently available, or when a message has some attribute that prevents
24568 its delivery when others to the same address get through. In this situation,
24569 because some messages are successfully delivered, the &"retry clock"& for the
24570 host or address keeps getting reset by the successful deliveries, and so
24571 failing messages remain on the queue for ever because the cutoff time is never
24574 Two exceptional actions are applied to prevent this happening. The first
24575 applies to errors that are related to a message rather than a remote host.
24576 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
24577 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
24578 commands, and quota failures. For this type of error, if a message's arrival
24579 time is earlier than the &"first failed"& time for the error, the earlier time
24580 is used when scanning the retry rules to decide when to try next and when to
24581 time out the address.
24583 The exceptional second action applies in all cases. If a message has been on
24584 the queue for longer than the cutoff time of any applicable retry rule for a
24585 given address, a delivery is attempted for that address, even if it is not yet
24586 time, and if this delivery fails, the address is timed out. A new retry time is
24587 not computed in this case, so that other messages for the same address are
24588 considered immediately.
24589 .ecindex IIDretconf1
24590 .ecindex IIDregconf2
24597 . ////////////////////////////////////////////////////////////////////////////
24598 . ////////////////////////////////////////////////////////////////////////////
24600 .chapter "SMTP authentication" "CHAPSMTPAUTH"
24601 .scindex IIDauthconf1 "SMTP" "authentication configuration"
24602 .scindex IIDauthconf2 "authentication"
24603 The &"authenticators"& section of Exim's run time configuration is concerned
24604 with SMTP authentication. This facility is an extension to the SMTP protocol,
24605 described in RFC 2554, which allows a client SMTP host to authenticate itself
24606 to a server. This is a common way for a server to recognize clients that are
24607 permitted to use it as a relay. SMTP authentication is not of relevance to the
24608 transfer of mail between servers that have no managerial connection with each
24611 .cindex "AUTH" "description of"
24612 Very briefly, the way SMTP authentication works is as follows:
24615 The server advertises a number of authentication &'mechanisms'& in response to
24616 the client's EHLO command.
24618 The client issues an AUTH command, naming a specific mechanism. The command
24619 may, optionally, contain some authentication data.
24621 The server may issue one or more &'challenges'&, to which the client must send
24622 appropriate responses. In simple authentication mechanisms, the challenges are
24623 just prompts for user names and passwords. The server does not have to issue
24624 any challenges &-- in some mechanisms the relevant data may all be transmitted
24625 with the AUTH command.
24627 The server either accepts or denies authentication.
24629 If authentication succeeds, the client may optionally make use of the AUTH
24630 option on the MAIL command to pass an authenticated sender in subsequent
24631 mail transactions. Authentication lasts for the remainder of the SMTP
24634 If authentication fails, the client may give up, or it may try a different
24635 authentication mechanism, or it may try transferring mail over the
24636 unauthenticated connection.
24639 If you are setting up a client, and want to know which authentication
24640 mechanisms the server supports, you can use Telnet to connect to port 25 (the
24641 SMTP port) on the server, and issue an EHLO command. The response to this
24642 includes the list of supported mechanisms. For example:
24644 &`$ `&&*&`telnet server.example 25`&*&
24645 &`Trying 192.168.34.25...`&
24646 &`Connected to server.example.`&
24647 &`Escape character is '^]'.`&
24648 &`220 server.example ESMTP Exim 4.20 ...`&
24649 &*&`ehlo client.example`&*&
24650 &`250-server.example Hello client.example [10.8.4.5]`&
24651 &`250-SIZE 52428800`&
24656 The second-last line of this example output shows that the server supports
24657 authentication using the PLAIN mechanism. In Exim, the different authentication
24658 mechanisms are configured by specifying &'authenticator'& drivers. Like the
24659 routers and transports, which authenticators are included in the binary is
24660 controlled by build-time definitions. The following are currently available,
24661 included by setting
24664 AUTH_CYRUS_SASL=yes
24667 AUTH_HEIMDAL_GSSAPI=yes
24671 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
24672 authentication mechanism (RFC 2195), and the second provides an interface to
24673 the Cyrus SASL authentication library.
24674 The third is an interface to Dovecot's authentication system, delegating the
24675 work via a socket interface.
24676 The fourth provides an interface to the GNU SASL authentication library, which
24677 provides mechanisms but typically not data sources.
24678 The fifth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
24679 supporting setting a server keytab.
24680 The sixth can be configured to support
24681 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
24682 not formally documented, but used by several MUAs. The seventh authenticator
24683 supports Microsoft's &'Secure Password Authentication'& mechanism.
24685 The authenticators are configured using the same syntax as other drivers (see
24686 section &<<SECTfordricon>>&). If no authenticators are required, no
24687 authentication section need be present in the configuration file. Each
24688 authenticator can in principle have both server and client functions. When Exim
24689 is receiving SMTP mail, it is acting as a server; when it is sending out
24690 messages over SMTP, it is acting as a client. Authenticator configuration
24691 options are provided for use in both these circumstances.
24693 To make it clear which options apply to which situation, the prefixes
24694 &%server_%& and &%client_%& are used on option names that are specific to
24695 either the server or the client function, respectively. Server and client
24696 functions are disabled if none of their options are set. If an authenticator is
24697 to be used for both server and client functions, a single definition, using
24698 both sets of options, is required. For example:
24702 public_name = CRAM-MD5
24703 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
24705 client_secret = secret2
24707 The &%server_%& option is used when Exim is acting as a server, and the
24708 &%client_%& options when it is acting as a client.
24710 Descriptions of the individual authenticators are given in subsequent chapters.
24711 The remainder of this chapter covers the generic options for the
24712 authenticators, followed by general discussion of the way authentication works
24715 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
24716 per-mechanism basis. Please read carefully to determine which variables hold
24717 account labels such as usercodes and which hold passwords or other
24718 authenticating data.
24720 Note that some mechanisms support two different identifiers for accounts: the
24721 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
24722 and &'authz'& are commonly encountered. The American spelling is standard here.
24723 Conceptually, authentication data such as passwords are tied to the identifier
24724 used to authenticate; servers may have rules to permit one user to act as a
24725 second user, so that after login the session is treated as though that second
24726 user had logged in. That second user is the &'authorization id'&. A robust
24727 configuration might confirm that the &'authz'& field is empty or matches the
24728 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
24729 as verified data, the &'authz'& as an unverified request which the server might
24732 A &'realm'& is a text string, typically a domain name, presented by a server
24733 to a client to help it select an account and credentials to use. In some
24734 mechanisms, the client and server provably agree on the realm, but clients
24735 typically can not treat the realm as secure data to be blindly trusted.
24739 .section "Generic options for authenticators" "SECID168"
24740 .cindex "authentication" "generic options"
24741 .cindex "options" "generic; for authenticators"
24743 .option client_condition authenticators string&!! unset
24744 When Exim is authenticating as a client, it skips any authenticator whose
24745 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
24746 used, for example, to skip plain text authenticators when the connection is not
24747 encrypted by a setting such as:
24749 client_condition = ${if !eq{$tls_out_cipher}{}}
24753 .option client_set_id authenticators string&!! unset
24754 When client authentication succeeds, this condition is expanded; the
24755 result is used in the log lines for outbound messasges.
24756 Typically it will be the user name used for authentication.
24759 .option driver authenticators string unset
24760 This option must always be set. It specifies which of the available
24761 authenticators is to be used.
24764 .option public_name authenticators string unset
24765 This option specifies the name of the authentication mechanism that the driver
24766 implements, and by which it is known to the outside world. These names should
24767 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
24768 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
24769 defaults to the driver's instance name.
24772 .option server_advertise_condition authenticators string&!! unset
24773 When a server is about to advertise an authentication mechanism, the condition
24774 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
24775 mechanism is not advertised.
24776 If the expansion fails, the mechanism is not advertised. If the failure was not
24777 forced, and was not caused by a lookup defer, the incident is logged.
24778 See section &<<SECTauthexiser>>& below for further discussion.
24781 .option server_condition authenticators string&!! unset
24782 This option must be set for a &%plaintext%& server authenticator, where it
24783 is used directly to control authentication. See section &<<SECTplainserver>>&
24786 For the &(gsasl)& authenticator, this option is required for various
24787 mechanisms; see chapter &<<CHAPgsasl>>& for details.
24789 For the other authenticators, &%server_condition%& can be used as an additional
24790 authentication or authorization mechanism that is applied after the other
24791 authenticator conditions succeed. If it is set, it is expanded when the
24792 authenticator would otherwise return a success code. If the expansion is forced
24793 to fail, authentication fails. Any other expansion failure causes a temporary
24794 error code to be returned. If the result of a successful expansion is an empty
24795 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
24796 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
24797 other result, a temporary error code is returned, with the expanded string as
24801 .option server_debug_print authenticators string&!! unset
24802 If this option is set and authentication debugging is enabled (see the &%-d%&
24803 command line option), the string is expanded and included in the debugging
24804 output when the authenticator is run as a server. This can help with checking
24805 out the values of variables.
24806 If expansion of the string fails, the error message is written to the debugging
24807 output, and Exim carries on processing.
24810 .option server_set_id authenticators string&!! unset
24811 .vindex "&$authenticated_id$&"
24812 When an Exim server successfully authenticates a client, this string is
24813 expanded using data from the authentication, and preserved for any incoming
24814 messages in the variable &$authenticated_id$&. It is also included in the log
24815 lines for incoming messages. For example, a user/password authenticator
24816 configuration might preserve the user name that was used to authenticate, and
24817 refer to it subsequently during delivery of the message.
24818 If expansion fails, the option is ignored.
24821 .option server_mail_auth_condition authenticators string&!! unset
24822 This option allows a server to discard authenticated sender addresses supplied
24823 as part of MAIL commands in SMTP connections that are authenticated by the
24824 driver on which &%server_mail_auth_condition%& is set. The option is not used
24825 as part of the authentication process; instead its (unexpanded) value is
24826 remembered for later use.
24827 How it is used is described in the following section.
24833 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
24834 .cindex "authentication" "sender; authenticated"
24835 .cindex "AUTH" "on MAIL command"
24836 When a client supplied an AUTH= item on a MAIL command, Exim applies
24837 the following checks before accepting it as the authenticated sender of the
24841 If the connection is not using extended SMTP (that is, HELO was used rather
24842 than EHLO), the use of AUTH= is a syntax error.
24844 If the value of the AUTH= parameter is &"<>"&, it is ignored.
24846 .vindex "&$authenticated_sender$&"
24847 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
24848 running, the value of &$authenticated_sender$& is set to the value obtained
24849 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
24850 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
24851 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
24852 given for the MAIL command.
24854 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
24855 is accepted and placed in &$authenticated_sender$& only if the client has
24858 If the AUTH= value was accepted by either of the two previous rules, and
24859 the client has authenticated, and the authenticator has a setting for the
24860 &%server_mail_auth_condition%&, the condition is checked at this point. The
24861 valued that was saved from the authenticator is expanded. If the expansion
24862 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
24863 &$authenticated_sender$& is deleted. If the expansion yields any other value,
24864 the value of &$authenticated_sender$& is retained and passed on with the
24869 When &$authenticated_sender$& is set for a message, it is passed on to other
24870 hosts to which Exim authenticates as a client. Do not confuse this value with
24871 &$authenticated_id$&, which is a string obtained from the authentication
24872 process, and which is not usually a complete email address.
24874 .vindex "&$sender_address$&"
24875 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
24876 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
24877 therefore make use of &$authenticated_sender$&. The converse is not true: the
24878 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
24883 .section "Authentication on an Exim server" "SECTauthexiser"
24884 .cindex "authentication" "on an Exim server"
24885 When Exim receives an EHLO command, it advertises the public names of those
24886 authenticators that are configured as servers, subject to the following
24890 The client host must match &%auth_advertise_hosts%& (default *).
24892 It the &%server_advertise_condition%& option is set, its expansion must not
24893 yield the empty string, &"0"&, &"no"&, or &"false"&.
24896 The order in which the authenticators are defined controls the order in which
24897 the mechanisms are advertised.
24899 Some mail clients (for example, some versions of Netscape) require the user to
24900 provide a name and password for authentication whenever AUTH is advertised,
24901 even though authentication may not in fact be needed (for example, Exim may be
24902 set up to allow unconditional relaying from the client by an IP address check).
24903 You can make such clients more friendly by not advertising AUTH to them.
24904 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
24905 that runs for RCPT) to relay without authentication, you should set
24907 auth_advertise_hosts = ! 10.9.8.0/24
24909 so that no authentication mechanisms are advertised to them.
24911 The &%server_advertise_condition%& controls the advertisement of individual
24912 authentication mechanisms. For example, it can be used to restrict the
24913 advertisement of a particular mechanism to encrypted connections, by a setting
24916 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
24918 .vindex "&$tls_in_cipher$&"
24919 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
24920 yields &"yes"&, which allows the advertisement to happen.
24922 When an Exim server receives an AUTH command from a client, it rejects it
24923 immediately if AUTH was not advertised in response to an earlier EHLO
24924 command. This is the case if
24927 The client host does not match &%auth_advertise_hosts%&; or
24929 No authenticators are configured with server options; or
24931 Expansion of &%server_advertise_condition%& blocked the advertising of all the
24932 server authenticators.
24936 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
24937 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
24938 AUTH is accepted from any client host.
24940 If AUTH is not rejected by the ACL, Exim searches its configuration for a
24941 server authentication mechanism that was advertised in response to EHLO and
24942 that matches the one named in the AUTH command. If it finds one, it runs
24943 the appropriate authentication protocol, and authentication either succeeds or
24944 fails. If there is no matching advertised mechanism, the AUTH command is
24945 rejected with a 504 error.
24947 .vindex "&$received_protocol$&"
24948 .vindex "&$sender_host_authenticated$&"
24949 When a message is received from an authenticated host, the value of
24950 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
24951 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
24952 public name) of the authenticator driver that successfully authenticated the
24953 client from which the message was received. This variable is empty if there was
24954 no successful authentication.
24959 .section "Testing server authentication" "SECID169"
24960 .cindex "authentication" "testing a server"
24961 .cindex "AUTH" "testing a server"
24962 .cindex "base64 encoding" "creating authentication test data"
24963 Exim's &%-bh%& option can be useful for testing server authentication
24964 configurations. The data for the AUTH command has to be sent using base64
24965 encoding. A quick way to produce such data for testing is the following Perl
24969 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
24971 .cindex "binary zero" "in authentication data"
24972 This interprets its argument as a Perl string, and then encodes it. The
24973 interpretation as a Perl string allows binary zeros, which are required for
24974 some kinds of authentication, to be included in the data. For example, a
24975 command line to run this script on such data might be
24977 encode '\0user\0password'
24979 Note the use of single quotes to prevent the shell interpreting the
24980 backslashes, so that they can be interpreted by Perl to specify characters
24981 whose code value is zero.
24983 &*Warning 1*&: If either of the user or password strings starts with an octal
24984 digit, you must use three zeros instead of one after the leading backslash. If
24985 you do not, the octal digit that starts your string will be incorrectly
24986 interpreted as part of the code for the first character.
24988 &*Warning 2*&: If there are characters in the strings that Perl interprets
24989 specially, you must use a Perl escape to prevent them being misinterpreted. For
24990 example, a command such as
24992 encode '\0user@domain.com\0pas$$word'
24994 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
24996 If you have the &%mimencode%& command installed, another way to do produce
24997 base64-encoded strings is to run the command
24999 echo -e -n `\0user\0password' | mimencode
25001 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
25002 in the argument, and the &%-n%& option specifies no newline at the end of its
25003 output. However, not all versions of &%echo%& recognize these options, so you
25004 should check your version before relying on this suggestion.
25008 .section "Authentication by an Exim client" "SECID170"
25009 .cindex "authentication" "on an Exim client"
25010 The &(smtp)& transport has two options called &%hosts_require_auth%& and
25011 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
25012 announces support for authentication, and the host matches an entry in either
25013 of these options, Exim (as a client) tries to authenticate as follows:
25016 For each authenticator that is configured as a client, in the order in which
25017 they are defined in the configuration, it searches the authentication
25018 mechanisms announced by the server for one whose name matches the public name
25019 of the authenticator.
25022 .vindex "&$host_address$&"
25023 When it finds one that matches, it runs the authenticator's client code. The
25024 variables &$host$& and &$host_address$& are available for any string expansions
25025 that the client might do. They are set to the server's name and IP address. If
25026 any expansion is forced to fail, the authentication attempt is abandoned, and
25027 Exim moves on to the next authenticator. Otherwise an expansion failure causes
25028 delivery to be deferred.
25030 If the result of the authentication attempt is a temporary error or a timeout,
25031 Exim abandons trying to send the message to the host for the moment. It will
25032 try again later. If there are any backup hosts available, they are tried in the
25035 If the response to authentication is a permanent error (5&'xx'& code), Exim
25036 carries on searching the list of authenticators and tries another one if
25037 possible. If all authentication attempts give permanent errors, or if there are
25038 no attempts because no mechanisms match (or option expansions force failure),
25039 what happens depends on whether the host matches &%hosts_require_auth%& or
25040 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
25041 delivery is deferred. The error can be detected in the retry rules, and thereby
25042 turned into a permanent error if you wish. In the second case, Exim tries to
25043 deliver the message unauthenticated.
25046 .cindex "AUTH" "on MAIL command"
25047 When Exim has authenticated itself to a remote server, it adds the AUTH
25048 parameter to the MAIL commands it sends, if it has an authenticated sender for
25049 the message. If the message came from a remote host, the authenticated sender
25050 is the one that was receiving on an incoming MAIL command, provided that the
25051 incoming connection was authenticated and the &%server_mail_auth%& condition
25052 allowed the authenticated sender to be retained. If a local process calls Exim
25053 to send a message, the sender address that is built from the login name and
25054 &%qualify_domain%& is treated as authenticated. However, if the
25055 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
25056 the authenticated sender that was received with the message.
25057 .ecindex IIDauthconf1
25058 .ecindex IIDauthconf2
25065 . ////////////////////////////////////////////////////////////////////////////
25066 . ////////////////////////////////////////////////////////////////////////////
25068 .chapter "The plaintext authenticator" "CHAPplaintext"
25069 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
25070 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
25071 The &(plaintext)& authenticator can be configured to support the PLAIN and
25072 LOGIN authentication mechanisms, both of which transfer authentication data as
25073 plain (unencrypted) text (though base64 encoded). The use of plain text is a
25074 security risk; you are strongly advised to insist on the use of SMTP encryption
25075 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
25076 use unencrypted plain text, you should not use the same passwords for SMTP
25077 connections as you do for login accounts.
25079 .section "Plaintext options" "SECID171"
25080 .cindex "options" "&(plaintext)& authenticator (server)"
25081 When configured as a server, &(plaintext)& uses the following options:
25083 .option server_condition authenticators string&!! unset
25084 This is actually a global authentication option, but it must be set in order to
25085 configure the &(plaintext)& driver as a server. Its use is described below.
25087 .option server_prompts plaintext string&!! unset
25088 The contents of this option, after expansion, must be a colon-separated list of
25089 prompt strings. If expansion fails, a temporary authentication rejection is
25092 .section "Using plaintext in a server" "SECTplainserver"
25093 .cindex "AUTH" "in &(plaintext)& authenticator"
25094 .cindex "binary zero" "in &(plaintext)& authenticator"
25095 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
25096 "in &(plaintext)& authenticator"
25097 .vindex "&$auth1$&, &$auth2$&, etc"
25098 .cindex "base64 encoding" "in &(plaintext)& authenticator"
25100 When running as a server, &(plaintext)& performs the authentication test by
25101 expanding a string. The data sent by the client with the AUTH command, or in
25102 response to subsequent prompts, is base64 encoded, and so may contain any byte
25103 values when decoded. If any data is supplied with the command, it is treated as
25104 a list of strings, separated by NULs (binary zeros), the first three of which
25105 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
25106 (neither LOGIN nor PLAIN uses more than three strings).
25108 For compatibility with previous releases of Exim, the values are also placed in
25109 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
25110 variables for this purpose is now deprecated, as it can lead to confusion in
25111 string expansions that also use them for other things.
25113 If there are more strings in &%server_prompts%& than the number of strings
25114 supplied with the AUTH command, the remaining prompts are used to obtain more
25115 data. Each response from the client may be a list of NUL-separated strings.
25117 .vindex "&$authenticated_id$&"
25118 Once a sufficient number of data strings have been received,
25119 &%server_condition%& is expanded. If the expansion is forced to fail,
25120 authentication fails. Any other expansion failure causes a temporary error code
25121 to be returned. If the result of a successful expansion is an empty string,
25122 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
25123 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
25124 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
25125 For any other result, a temporary error code is returned, with the expanded
25126 string as the error text
25128 &*Warning*&: If you use a lookup in the expansion to find the user's
25129 password, be sure to make the authentication fail if the user is unknown.
25130 There are good and bad examples at the end of the next section.
25134 .section "The PLAIN authentication mechanism" "SECID172"
25135 .cindex "PLAIN authentication mechanism"
25136 .cindex "authentication" "PLAIN mechanism"
25137 .cindex "binary zero" "in &(plaintext)& authenticator"
25138 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
25139 sent as one item of data (that is, one combined string containing two NUL
25140 separators). The data is sent either as part of the AUTH command, or
25141 subsequently in response to an empty prompt from the server.
25143 The second and third strings are a user name and a corresponding password.
25144 Using a single fixed user name and password as an example, this could be
25145 configured as follows:
25149 public_name = PLAIN
25151 server_condition = \
25152 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
25153 server_set_id = $auth2
25155 Note that the default result strings from &%if%& (&"true"& or an empty string)
25156 are exactly what we want here, so they need not be specified. Obviously, if the
25157 password contains expansion-significant characters such as dollar, backslash,
25158 or closing brace, they have to be escaped.
25160 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
25161 the end of a string list are ignored). If all the data comes as part of the
25162 AUTH command, as is commonly the case, the prompt is not used. This
25163 authenticator is advertised in the response to EHLO as
25167 and a client host can authenticate itself by sending the command
25169 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
25171 As this contains three strings (more than the number of prompts), no further
25172 data is required from the client. Alternatively, the client may just send
25176 to initiate authentication, in which case the server replies with an empty
25177 prompt. The client must respond with the combined data string.
25179 The data string is base64 encoded, as required by the RFC. This example,
25180 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
25181 represents a zero byte. This is split up into three strings, the first of which
25182 is empty. The &%server_condition%& option in the authenticator checks that the
25183 second two are &`username`& and &`mysecret`& respectively.
25185 Having just one fixed user name and password, as in this example, is not very
25186 realistic, though for a small organization with only a handful of
25187 authenticating clients it could make sense.
25189 A more sophisticated instance of this authenticator could use the user name in
25190 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
25191 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
25192 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
25193 This is an incorrect example:
25195 server_condition = \
25196 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
25198 The expansion uses the user name (&$auth2$&) as the key to look up a password,
25199 which it then compares to the supplied password (&$auth3$&). Why is this example
25200 incorrect? It works fine for existing users, but consider what happens if a
25201 non-existent user name is given. The lookup fails, but as no success/failure
25202 strings are given for the lookup, it yields an empty string. Thus, to defeat
25203 the authentication, all a client has to do is to supply a non-existent user
25204 name and an empty password. The correct way of writing this test is:
25206 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
25207 {${if eq{$value}{$auth3}}} {false}}
25209 In this case, if the lookup succeeds, the result is checked; if the lookup
25210 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
25211 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
25212 always fails if its second argument is empty. However, the second way of
25213 writing the test makes the logic clearer.
25216 .section "The LOGIN authentication mechanism" "SECID173"
25217 .cindex "LOGIN authentication mechanism"
25218 .cindex "authentication" "LOGIN mechanism"
25219 The LOGIN authentication mechanism is not documented in any RFC, but is in use
25220 in a number of programs. No data is sent with the AUTH command. Instead, a
25221 user name and password are supplied separately, in response to prompts. The
25222 plaintext authenticator can be configured to support this as in this example:
25226 public_name = LOGIN
25227 server_prompts = User Name : Password
25228 server_condition = \
25229 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
25230 server_set_id = $auth1
25232 Because of the way plaintext operates, this authenticator accepts data supplied
25233 with the AUTH command (in contravention of the specification of LOGIN), but
25234 if the client does not supply it (as is the case for LOGIN clients), the prompt
25235 strings are used to obtain two data items.
25237 Some clients are very particular about the precise text of the prompts. For
25238 example, Outlook Express is reported to recognize only &"Username:"& and
25239 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
25240 strings. It uses the &%ldapauth%& expansion condition to check the user
25241 name and password by binding to an LDAP server:
25245 public_name = LOGIN
25246 server_prompts = Username:: : Password::
25247 server_condition = ${if and{{ \
25250 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
25251 pass=${quote:$auth2} \
25252 ldap://ldap.example.org/} }} }
25253 server_set_id = uid=$auth1,ou=people,o=example.org
25255 We have to check that the username is not empty before using it, because LDAP
25256 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
25257 operator to correctly quote the DN for authentication. However, the basic
25258 &%quote%& operator, rather than any of the LDAP quoting operators, is the
25259 correct one to use for the password, because quoting is needed only to make
25260 the password conform to the Exim syntax. At the LDAP level, the password is an
25261 uninterpreted string.
25264 .section "Support for different kinds of authentication" "SECID174"
25265 A number of string expansion features are provided for the purpose of
25266 interfacing to different ways of user authentication. These include checking
25267 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
25268 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
25274 .section "Using plaintext in a client" "SECID175"
25275 .cindex "options" "&(plaintext)& authenticator (client)"
25276 The &(plaintext)& authenticator has two client options:
25278 .option client_ignore_invalid_base64 plaintext boolean false
25279 If the client receives a server prompt that is not a valid base64 string,
25280 authentication is abandoned by default. However, if this option is set true,
25281 the error in the challenge is ignored and the client sends the response as
25284 .option client_send plaintext string&!! unset
25285 The string is a colon-separated list of authentication data strings. Each
25286 string is independently expanded before being sent to the server. The first
25287 string is sent with the AUTH command; any more strings are sent in response
25288 to prompts from the server. Before each string is expanded, the value of the
25289 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
25290 with &$auth1$& for the first prompt. Up to three prompts are stored in this
25291 way. Thus, the prompt that is received in response to sending the first string
25292 (with the AUTH command) can be used in the expansion of the second string, and
25293 so on. If an invalid base64 string is received when
25294 &%client_ignore_invalid_base64%& is set, an empty string is put in the
25295 &$auth$&<&'n'&> variable.
25297 &*Note*&: You cannot use expansion to create multiple strings, because
25298 splitting takes priority and happens first.
25300 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
25301 the data, further processing is applied to each string before it is sent. If
25302 there are any single circumflex characters in the string, they are converted to
25303 NULs. Should an actual circumflex be required as data, it must be doubled in
25306 This is an example of a client configuration that implements the PLAIN
25307 authentication mechanism with a fixed user name and password:
25311 public_name = PLAIN
25312 client_send = ^username^mysecret
25314 The lack of colons means that the entire text is sent with the AUTH
25315 command, with the circumflex characters converted to NULs. A similar example
25316 that uses the LOGIN mechanism is:
25320 public_name = LOGIN
25321 client_send = : username : mysecret
25323 The initial colon means that the first string is empty, so no data is sent with
25324 the AUTH command itself. The remaining strings are sent in response to
25326 .ecindex IIDplaiauth1
25327 .ecindex IIDplaiauth2
25332 . ////////////////////////////////////////////////////////////////////////////
25333 . ////////////////////////////////////////////////////////////////////////////
25335 .chapter "The cram_md5 authenticator" "CHID9"
25336 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
25337 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
25338 .cindex "CRAM-MD5 authentication mechanism"
25339 .cindex "authentication" "CRAM-MD5 mechanism"
25340 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
25341 sends a challenge string to the client, and the response consists of a user
25342 name and the CRAM-MD5 digest of the challenge string combined with a secret
25343 string (password) which is known to both server and client. Thus, the secret
25344 is not sent over the network as plain text, which makes this authenticator more
25345 secure than &(plaintext)&. However, the downside is that the secret has to be
25346 available in plain text at either end.
25349 .section "Using cram_md5 as a server" "SECID176"
25350 .cindex "options" "&(cram_md5)& authenticator (server)"
25351 This authenticator has one server option, which must be set to configure the
25352 authenticator as a server:
25354 .option server_secret cram_md5 string&!! unset
25355 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
25356 When the server receives the client's response, the user name is placed in
25357 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
25358 obtain the password for that user. The server then computes the CRAM-MD5 digest
25359 that the client should have sent, and checks that it received the correct
25360 string. If the expansion of &%server_secret%& is forced to fail, authentication
25361 fails. If the expansion fails for some other reason, a temporary error code is
25362 returned to the client.
25364 For compatibility with previous releases of Exim, the user name is also placed
25365 in &$1$&. However, the use of this variables for this purpose is now
25366 deprecated, as it can lead to confusion in string expansions that also use
25367 numeric variables for other things.
25369 For example, the following authenticator checks that the user name given by the
25370 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
25371 user name, authentication fails.
25375 public_name = CRAM-MD5
25376 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
25377 server_set_id = $auth1
25379 .vindex "&$authenticated_id$&"
25380 If authentication succeeds, the setting of &%server_set_id%& preserves the user
25381 name in &$authenticated_id$&. A more typical configuration might look up the
25382 secret string in a file, using the user name as the key. For example:
25386 public_name = CRAM-MD5
25387 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
25389 server_set_id = $auth1
25391 Note that this expansion explicitly forces failure if the lookup fails
25392 because &$auth1$& contains an unknown user name.
25394 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
25395 using the relevant libraries, you need to know the realm to specify in the
25396 lookup and then ask for the &"userPassword"& attribute for that user in that
25401 public_name = CRAM-MD5
25402 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
25403 dbmjz{/etc/sasldb2}}
25404 server_set_id = $auth1
25407 .section "Using cram_md5 as a client" "SECID177"
25408 .cindex "options" "&(cram_md5)& authenticator (client)"
25409 When used as a client, the &(cram_md5)& authenticator has two options:
25413 .option client_name cram_md5 string&!! "the primary host name"
25414 This string is expanded, and the result used as the user name data when
25415 computing the response to the server's challenge.
25418 .option client_secret cram_md5 string&!! unset
25419 This option must be set for the authenticator to work as a client. Its value is
25420 expanded and the result used as the secret string when computing the response.
25424 .vindex "&$host_address$&"
25425 Different user names and secrets can be used for different servers by referring
25426 to &$host$& or &$host_address$& in the options. Forced failure of either
25427 expansion string is treated as an indication that this authenticator is not
25428 prepared to handle this case. Exim moves on to the next configured client
25429 authenticator. Any other expansion failure causes Exim to give up trying to
25430 send the message to the current server.
25432 A simple example configuration of a &(cram_md5)& authenticator, using fixed
25437 public_name = CRAM-MD5
25439 client_secret = secret
25441 .ecindex IIDcramauth1
25442 .ecindex IIDcramauth2
25446 . ////////////////////////////////////////////////////////////////////////////
25447 . ////////////////////////////////////////////////////////////////////////////
25449 .chapter "The cyrus_sasl authenticator" "CHID10"
25450 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
25451 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
25452 .cindex "Cyrus" "SASL library"
25454 The code for this authenticator was provided by Matthew Byng-Maddick of A L
25455 Digital Ltd (&url(http://www.aldigital.co.uk)).
25457 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
25458 library implementation of the RFC 2222 (&"Simple Authentication and Security
25459 Layer"&). This library supports a number of authentication mechanisms,
25460 including PLAIN and LOGIN, but also several others that Exim does not support
25461 directly. In particular, there is support for Kerberos authentication.
25463 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
25464 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
25465 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
25466 name of the driver to determine which mechanism to support.
25468 Where access to some kind of secret file is required, for example in GSSAPI
25469 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
25470 user, and that the Cyrus SASL library has no way of escalating privileges
25471 by default. You may also find you need to set environment variables,
25472 depending on the driver you are using.
25474 The application name provided by Exim is &"exim"&, so various SASL options may
25475 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
25476 Kerberos, note that because of limitations in the GSSAPI interface,
25477 changing the server keytab might need to be communicated down to the Kerberos
25478 layer independently. The mechanism for doing so is dependent upon the Kerberos
25481 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
25482 may be set to point to an alternative keytab file. Exim will pass this
25483 variable through from its own inherited environment when started as root or the
25484 Exim user. The keytab file needs to be readable by the Exim user.
25485 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
25486 environment variable. In practice, for those releases, the Cyrus authenticator
25487 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
25488 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
25491 .section "Using cyrus_sasl as a server" "SECID178"
25492 The &(cyrus_sasl)& authenticator has four private options. It puts the username
25493 (on a successful authentication) into &$auth1$&. For compatibility with
25494 previous releases of Exim, the username is also placed in &$1$&. However, the
25495 use of this variable for this purpose is now deprecated, as it can lead to
25496 confusion in string expansions that also use numeric variables for other
25500 .option server_hostname cyrus_sasl string&!! "see below"
25501 This option selects the hostname that is used when communicating with the
25502 library. The default value is &`$primary_hostname`&. It is up to the underlying
25503 SASL plug-in what it does with this data.
25506 .option server_mech cyrus_sasl string "see below"
25507 This option selects the authentication mechanism this driver should use. The
25508 default is the value of the generic &%public_name%& option. This option allows
25509 you to use a different underlying mechanism from the advertised name. For
25513 driver = cyrus_sasl
25514 public_name = X-ANYTHING
25515 server_mech = CRAM-MD5
25516 server_set_id = $auth1
25519 .option server_realm cyrus_sasl string&!! unset
25520 This specifies the SASL realm that the server claims to be in.
25523 .option server_service cyrus_sasl string &`smtp`&
25524 This is the SASL service that the server claims to implement.
25527 For straightforward cases, you do not need to set any of the authenticator's
25528 private options. All you need to do is to specify an appropriate mechanism as
25529 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
25530 PLAIN, you could have two authenticators as follows:
25533 driver = cyrus_sasl
25534 public_name = CRAM-MD5
25535 server_set_id = $auth1
25538 driver = cyrus_sasl
25539 public_name = PLAIN
25540 server_set_id = $auth2
25542 Cyrus SASL does implement the LOGIN authentication method, even though it is
25543 not a standard method. It is disabled by default in the source distribution,
25544 but it is present in many binary distributions.
25545 .ecindex IIDcyrauth1
25546 .ecindex IIDcyrauth2
25551 . ////////////////////////////////////////////////////////////////////////////
25552 . ////////////////////////////////////////////////////////////////////////////
25553 .chapter "The dovecot authenticator" "CHAPdovecot"
25554 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
25555 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
25556 This authenticator is an interface to the authentication facility of the
25557 Dovecot POP/IMAP server, which can support a number of authentication methods.
25558 Note that Dovecot must be configured to use auth-client not auth-userdb.
25559 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
25560 to use the same mechanisms for SMTP authentication. This is a server
25561 authenticator only. There is only one option:
25563 .option server_socket dovecot string unset
25565 This option must specify the socket that is the interface to Dovecot
25566 authentication. The &%public_name%& option must specify an authentication
25567 mechanism that Dovecot is configured to support. You can have several
25568 authenticators for different mechanisms. For example:
25572 public_name = PLAIN
25573 server_socket = /var/run/dovecot/auth-client
25574 server_set_id = $auth1
25579 server_socket = /var/run/dovecot/auth-client
25580 server_set_id = $auth1
25582 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
25583 &$received_ip_address$& (that is, the connection is local), the &"secured"&
25584 option is passed in the Dovecot authentication command. If, for a TLS
25585 connection, a client certificate has been verified, the &"valid-client-cert"&
25586 option is passed. When authentication succeeds, the identity of the user
25587 who authenticated is placed in &$auth1$&.
25588 .ecindex IIDdcotauth1
25589 .ecindex IIDdcotauth2
25592 . ////////////////////////////////////////////////////////////////////////////
25593 . ////////////////////////////////////////////////////////////////////////////
25594 .chapter "The gsasl authenticator" "CHAPgsasl"
25595 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
25596 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
25597 .cindex "authentication" "GNU SASL"
25598 .cindex "authentication" "SASL"
25599 .cindex "authentication" "EXTERNAL"
25600 .cindex "authentication" "ANONYMOUS"
25601 .cindex "authentication" "PLAIN"
25602 .cindex "authentication" "LOGIN"
25603 .cindex "authentication" "DIGEST-MD5"
25604 .cindex "authentication" "CRAM-MD5"
25605 .cindex "authentication" "SCRAM-SHA-1"
25606 The &(gsasl)& authenticator provides server integration for the GNU SASL
25607 library and the mechanisms it provides. This is new as of the 4.80 release
25608 and there are a few areas where the library does not let Exim smoothly
25609 scale to handle future authentication mechanisms, so no guarantee can be
25610 made that any particular new authentication mechanism will be supported
25611 without code changes in Exim.
25614 .option server_channelbinding gsasl boolean false
25615 Some authentication mechanisms are able to use external context at both ends
25616 of the session to bind the authentication to that context, and fail the
25617 authentication process if that context differs. Specifically, some TLS
25618 ciphersuites can provide identifying information about the cryptographic
25621 This means that certificate identity and verification becomes a non-issue,
25622 as a man-in-the-middle attack will cause the correct client and server to
25623 see different identifiers and authentication will fail.
25625 This is currently only supported when using the GnuTLS library. This is
25626 only usable by mechanisms which support "channel binding"; at time of
25627 writing, that's the SCRAM family.
25629 This defaults off to ensure smooth upgrade across Exim releases, in case
25630 this option causes some clients to start failing. Some future release
25631 of Exim may switch the default to be true.
25634 .option server_hostname gsasl string&!! "see below"
25635 This option selects the hostname that is used when communicating with the
25636 library. The default value is &`$primary_hostname`&.
25637 Some mechanisms will use this data.
25640 .option server_mech gsasl string "see below"
25641 This option selects the authentication mechanism this driver should use. The
25642 default is the value of the generic &%public_name%& option. This option allows
25643 you to use a different underlying mechanism from the advertised name. For
25648 public_name = X-ANYTHING
25649 server_mech = CRAM-MD5
25650 server_set_id = $auth1
25654 .option server_password gsasl string&!! unset
25655 Various mechanisms need access to the cleartext password on the server, so
25656 that proof-of-possession can be demonstrated on the wire, without sending
25657 the password itself.
25659 The data available for lookup varies per mechanism.
25660 In all cases, &$auth1$& is set to the &'authentication id'&.
25661 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
25662 if available, else the empty string.
25663 The &$auth3$& variable will always be the &'realm'& if available,
25664 else the empty string.
25666 A forced failure will cause authentication to defer.
25668 If using this option, it may make sense to set the &%server_condition%&
25669 option to be simply "true".
25672 .option server_realm gsasl string&!! unset
25673 This specifies the SASL realm that the server claims to be in.
25674 Some mechanisms will use this data.
25677 .option server_scram_iter gsasl string&!! unset
25678 This option provides data for the SCRAM family of mechanisms.
25679 &$auth1$& is not available at evaluation time.
25680 (This may change, as we receive feedback on use)
25683 .option server_scram_salt gsasl string&!! unset
25684 This option provides data for the SCRAM family of mechanisms.
25685 &$auth1$& is not available at evaluation time.
25686 (This may change, as we receive feedback on use)
25689 .option server_service gsasl string &`smtp`&
25690 This is the SASL service that the server claims to implement.
25691 Some mechanisms will use this data.
25694 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
25695 .vindex "&$auth1$&, &$auth2$&, etc"
25696 These may be set when evaluating specific options, as detailed above.
25697 They will also be set when evaluating &%server_condition%&.
25699 Unless otherwise stated below, the &(gsasl)& integration will use the following
25700 meanings for these variables:
25703 .vindex "&$auth1$&"
25704 &$auth1$&: the &'authentication id'&
25706 .vindex "&$auth2$&"
25707 &$auth2$&: the &'authorization id'&
25709 .vindex "&$auth3$&"
25710 &$auth3$&: the &'realm'&
25713 On a per-mechanism basis:
25716 .cindex "authentication" "EXTERNAL"
25717 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
25718 the &%server_condition%& option must be present.
25720 .cindex "authentication" "ANONYMOUS"
25721 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
25722 the &%server_condition%& option must be present.
25724 .cindex "authentication" "GSSAPI"
25725 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
25726 &$auth2$& will be set to the &'authorization id'&,
25727 the &%server_condition%& option must be present.
25730 An &'anonymous token'& is something passed along as an unauthenticated
25731 identifier; this is analogous to FTP anonymous authentication passing an
25732 email address, or software-identifier@, as the "password".
25735 An example showing the password having the realm specified in the callback
25736 and demonstrating a Cyrus SASL to GSASL migration approach is:
25738 gsasl_cyrusless_crammd5:
25740 public_name = CRAM-MD5
25741 server_realm = imap.example.org
25742 server_password = ${lookup{$auth1:$auth3:userPassword}\
25743 dbmjz{/etc/sasldb2}{$value}fail}
25744 server_set_id = ${quote:$auth1}
25745 server_condition = yes
25749 . ////////////////////////////////////////////////////////////////////////////
25750 . ////////////////////////////////////////////////////////////////////////////
25752 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
25753 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
25754 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
25755 .cindex "authentication" "GSSAPI"
25756 .cindex "authentication" "Kerberos"
25757 The &(heimdal_gssapi)& authenticator provides server integration for the
25758 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
25761 .option server_hostname heimdal_gssapi string&!! "see below"
25762 This option selects the hostname that is used, with &%server_service%&,
25763 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
25764 identifier. The default value is &`$primary_hostname`&.
25766 .option server_keytab heimdal_gssapi string&!! unset
25767 If set, then Heimdal will not use the system default keytab (typically
25768 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
25769 The value should be a pathname, with no &"file:"& prefix.
25771 .option server_service heimdal_gssapi string&!! "smtp"
25772 This option specifies the service identifier used, in conjunction with
25773 &%server_hostname%&, for building the identifer for finding credentials
25777 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
25778 Beware that these variables will typically include a realm, thus will appear
25779 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
25780 not verified, so a malicious client can set it to anything.
25782 The &$auth1$& field should be safely trustable as a value from the Key
25783 Distribution Center. Note that these are not quite email addresses.
25784 Each identifier is for a role, and so the left-hand-side may include a
25785 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
25787 .vindex "&$auth1$&, &$auth2$&, etc"
25789 .vindex "&$auth1$&"
25790 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
25792 .vindex "&$auth2$&"
25793 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
25794 authentication. If that was empty, this will also be set to the
25799 . ////////////////////////////////////////////////////////////////////////////
25800 . ////////////////////////////////////////////////////////////////////////////
25802 .chapter "The spa authenticator" "CHAPspa"
25803 .scindex IIDspaauth1 "&(spa)& authenticator"
25804 .scindex IIDspaauth2 "authenticators" "&(spa)&"
25805 .cindex "authentication" "Microsoft Secure Password"
25806 .cindex "authentication" "NTLM"
25807 .cindex "Microsoft Secure Password Authentication"
25808 .cindex "NTLM authentication"
25809 The &(spa)& authenticator provides client support for Microsoft's &'Secure
25810 Password Authentication'& mechanism,
25811 which is also sometimes known as NTLM (NT LanMan). The code for client side of
25812 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
25813 taken from the Samba project (&url(http://www.samba.org)). The code for the
25814 server side was subsequently contributed by Tom Kistner. The mechanism works as
25818 After the AUTH command has been accepted, the client sends an SPA
25819 authentication request based on the user name and optional domain.
25821 The server sends back a challenge.
25823 The client builds a challenge response which makes use of the user's password
25824 and sends it to the server, which then accepts or rejects it.
25827 Encryption is used to protect the password in transit.
25831 .section "Using spa as a server" "SECID179"
25832 .cindex "options" "&(spa)& authenticator (server)"
25833 The &(spa)& authenticator has just one server option:
25835 .option server_password spa string&!! unset
25836 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
25837 This option is expanded, and the result must be the cleartext password for the
25838 authenticating user, whose name is at this point in &$auth1$&. For
25839 compatibility with previous releases of Exim, the user name is also placed in
25840 &$1$&. However, the use of this variable for this purpose is now deprecated, as
25841 it can lead to confusion in string expansions that also use numeric variables
25842 for other things. For example:
25847 server_password = \
25848 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
25850 If the expansion is forced to fail, authentication fails. Any other expansion
25851 failure causes a temporary error code to be returned.
25857 .section "Using spa as a client" "SECID180"
25858 .cindex "options" "&(spa)& authenticator (client)"
25859 The &(spa)& authenticator has the following client options:
25863 .option client_domain spa string&!! unset
25864 This option specifies an optional domain for the authentication.
25867 .option client_password spa string&!! unset
25868 This option specifies the user's password, and must be set.
25871 .option client_username spa string&!! unset
25872 This option specifies the user name, and must be set. Here is an example of a
25873 configuration of this authenticator for use with the mail servers at
25879 client_username = msn/msn_username
25880 client_password = msn_plaintext_password
25881 client_domain = DOMAIN_OR_UNSET
25883 .ecindex IIDspaauth1
25884 .ecindex IIDspaauth2
25890 . ////////////////////////////////////////////////////////////////////////////
25891 . ////////////////////////////////////////////////////////////////////////////
25893 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
25894 "Encrypted SMTP connections"
25895 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
25896 .scindex IIDencsmtp2 "SMTP" "encryption"
25897 .cindex "TLS" "on SMTP connection"
25900 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
25901 Sockets Layer), is implemented by making use of the OpenSSL library or the
25902 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
25903 cryptographic code in the Exim distribution itself for implementing TLS. In
25904 order to use this feature you must install OpenSSL or GnuTLS, and then build a
25905 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
25906 You also need to understand the basic concepts of encryption at a managerial
25907 level, and in particular, the way that public keys, private keys, and
25908 certificates are used.
25910 RFC 3207 defines how SMTP connections can make use of encryption. Once a
25911 connection is established, the client issues a STARTTLS command. If the
25912 server accepts this, the client and the server negotiate an encryption
25913 mechanism. If the negotiation succeeds, the data that subsequently passes
25914 between them is encrypted.
25916 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
25917 and if so, what cipher suite is in use, whether the client supplied a
25918 certificate, and whether or not that certificate was verified. This makes it
25919 possible for an Exim server to deny or accept certain commands based on the
25922 &*Warning*&: Certain types of firewall and certain anti-virus products can
25923 disrupt TLS connections. You need to turn off SMTP scanning for these products
25924 in order to get TLS to work.
25928 .section "Support for the legacy &""ssmtp""& (aka &""smtps""&) protocol" &&&
25930 .cindex "ssmtp protocol"
25931 .cindex "smtps protocol"
25932 .cindex "SMTP" "ssmtp protocol"
25933 .cindex "SMTP" "smtps protocol"
25934 Early implementations of encrypted SMTP used a different TCP port from normal
25935 SMTP, and expected an encryption negotiation to start immediately, instead of
25936 waiting for a STARTTLS command from the client using the standard SMTP
25937 port. The protocol was called &"ssmtp"& or &"smtps"&, and port 465 was
25938 allocated for this purpose.
25940 This approach was abandoned when encrypted SMTP was standardized, but there are
25941 still some legacy clients that use it. Exim supports these clients by means of
25942 the &%tls_on_connect_ports%& global option. Its value must be a list of port
25943 numbers; the most common use is expected to be:
25945 tls_on_connect_ports = 465
25947 The port numbers specified by this option apply to all SMTP connections, both
25948 via the daemon and via &'inetd'&. You still need to specify all the ports that
25949 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
25950 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
25951 an extra port &-- rather, it specifies different behaviour on a port that is
25954 There is also a &%-tls-on-connect%& command line option. This overrides
25955 &%tls_on_connect_ports%&; it forces the legacy behaviour for all ports.
25962 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
25963 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
25964 The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
25965 followed later, when the first versions of GnuTLS were released. To build Exim
25966 to use GnuTLS, you need to set
25970 in Local/Makefile, in addition to
25974 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
25975 include files and libraries for GnuTLS can be found.
25977 There are some differences in usage when using GnuTLS instead of OpenSSL:
25980 The &%tls_verify_certificates%& option
25981 cannot be the path of a directory
25982 for GnuTLS versions before 3.3.6
25983 (for later versions, or OpenSSL, it can be either).
25985 The default value for &%tls_dhparam%& differs for historical reasons.
25987 .vindex "&$tls_in_peerdn$&"
25988 .vindex "&$tls_out_peerdn$&"
25989 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
25990 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
25991 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
25993 OpenSSL identifies cipher suites using hyphens as separators, for example:
25994 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
25995 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
25996 in a cipher list. To make life simpler, Exim changes underscores to hyphens
25997 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
25998 to handle its own older variants) when processing lists of cipher suites in the
25999 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
26002 The &%tls_require_ciphers%& options operate differently, as described in the
26003 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
26005 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
26006 When using OpenSSL, this option is ignored.
26007 (If an API is found to let OpenSSL be configured in this way,
26008 let the Exim Maintainers know and we'll likely use it).
26010 Some other recently added features may only be available in one or the other.
26011 This should be documented with the feature. If the documentation does not
26012 explicitly state that the feature is infeasible in the other TLS
26013 implementation, then patches are welcome.
26017 .section "GnuTLS parameter computation" "SECTgnutlsparam"
26018 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
26019 an explicit path; if the latter, then the text about generation still applies,
26020 but not the chosen filename.
26021 By default, as of Exim 4.80 a hard-coded D-H prime is used.
26022 See the documentation of &%tls_dhparam%& for more information.
26024 GnuTLS uses D-H parameters that may take a substantial amount of time
26025 to compute. It is unreasonable to re-compute them for every TLS session.
26026 Therefore, Exim keeps this data in a file in its spool directory, called
26027 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
26029 The file is owned by the Exim user and is readable only by
26030 its owner. Every Exim process that start up GnuTLS reads the D-H
26031 parameters from this file. If the file does not exist, the first Exim process
26032 that needs it computes the data and writes it to a temporary file which is
26033 renamed once it is complete. It does not matter if several Exim processes do
26034 this simultaneously (apart from wasting a few resources). Once a file is in
26035 place, new Exim processes immediately start using it.
26037 For maximum security, the parameters that are stored in this file should be
26038 recalculated periodically, the frequency depending on your paranoia level.
26039 If you are avoiding using the fixed D-H primes published in RFCs, then you
26040 are concerned about some advanced attacks and will wish to do this; if you do
26041 not regenerate then you might as well stick to the standard primes.
26043 Arranging this is easy in principle; just delete the file when you want new
26044 values to be computed. However, there may be a problem. The calculation of new
26045 parameters needs random numbers, and these are obtained from &_/dev/random_&.
26046 If the system is not very active, &_/dev/random_& may delay returning data
26047 until enough randomness (entropy) is available. This may cause Exim to hang for
26048 a substantial amount of time, causing timeouts on incoming connections.
26050 The solution is to generate the parameters externally to Exim. They are stored
26051 in &_gnutls-params-N_& in PEM format, which means that they can be
26052 generated externally using the &(certtool)& command that is part of GnuTLS.
26054 To replace the parameters with new ones, instead of deleting the file
26055 and letting Exim re-create it, you can generate new parameters using
26056 &(certtool)& and, when this has been done, replace Exim's cache file by
26057 renaming. The relevant commands are something like this:
26060 [ look for file; assume gnutls-params-2236 is the most recent ]
26063 # chown exim:exim new-params
26064 # chmod 0600 new-params
26065 # certtool --generate-dh-params --bits 2236 >>new-params
26066 # openssl dhparam -noout -text -in new-params | head
26067 [ check the first line, make sure it's not more than 2236;
26068 if it is, then go back to the start ("rm") and repeat
26069 until the size generated is at most the size requested ]
26070 # chmod 0400 new-params
26071 # mv new-params gnutls-params-2236
26073 If Exim never has to generate the parameters itself, the possibility of
26074 stalling is removed.
26076 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
26077 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
26078 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
26079 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
26080 and Exim does so. This attempt to remove Exim from TLS policy decisions
26081 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
26082 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
26083 which applies to all D-H usage, client or server. If the value returned by
26084 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
26085 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
26086 limit, which is still much higher than Exim historically used.
26088 The filename and bits used will change as the GnuTLS maintainers change the
26089 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
26090 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
26091 2432 bits, while NSS is limited to 2236 bits.
26093 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
26094 increase the chance of the generated prime actually being within acceptable
26095 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
26096 procedure above. There is no sane procedure available to Exim to double-check
26097 the size of the generated prime, so it might still be too large.
26100 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
26101 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
26102 .oindex "&%tls_require_ciphers%&" "OpenSSL"
26103 There is a function in the OpenSSL library that can be passed a list of cipher
26104 suites before the cipher negotiation takes place. This specifies which ciphers
26105 are acceptable. The list is colon separated and may contain names like
26106 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
26107 directly to this function call.
26108 Many systems will install the OpenSSL manual-pages, so you may have
26109 &'ciphers(1)'& available to you.
26110 The following quotation from the OpenSSL
26111 documentation specifies what forms of item are allowed in the cipher string:
26114 It can consist of a single cipher suite such as RC4-SHA.
26116 It can represent a list of cipher suites containing a certain algorithm,
26117 or cipher suites of a certain type. For example SHA1 represents all
26118 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
26121 Lists of cipher suites can be combined in a single cipher string using
26122 the + character. This is used as a logical and operation. For example
26123 SHA1+DES represents all cipher suites containing the SHA1 and the DES
26127 Each cipher string can be optionally preceded by one of the characters &`!`&,
26130 If &`!`& is used, the ciphers are permanently deleted from the list. The
26131 ciphers deleted can never reappear in the list even if they are explicitly
26134 If &`-`& is used, the ciphers are deleted from the list, but some or all
26135 of the ciphers can be added again by later options.
26137 If &`+`& is used, the ciphers are moved to the end of the list. This
26138 option does not add any new ciphers; it just moves matching existing ones.
26141 If none of these characters is present, the string is interpreted as
26142 a list of ciphers to be appended to the current preference list. If the list
26143 includes any ciphers already present they will be ignored: that is, they will
26144 not be moved to the end of the list.
26147 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
26150 # note single-quotes to get ! past any shell history expansion
26151 $ openssl ciphers 'HIGH:!MD5:!SHA1'
26154 This example will let the library defaults be permitted on the MX port, where
26155 there's probably no identity verification anyway, but ups the ante on the
26156 submission ports where the administrator might have some influence on the
26157 choice of clients used:
26159 # OpenSSL variant; see man ciphers(1)
26160 tls_require_ciphers = ${if =={$received_port}{25}\
26167 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
26169 .cindex "GnuTLS" "specifying parameters for"
26170 .cindex "TLS" "specifying ciphers (GnuTLS)"
26171 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
26172 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
26173 .cindex "TLS" "specifying protocols (GnuTLS)"
26174 .cindex "TLS" "specifying priority string (GnuTLS)"
26175 .oindex "&%tls_require_ciphers%&" "GnuTLS"
26176 The GnuTLS library allows the caller to provide a "priority string", documented
26177 as part of the &[gnutls_priority_init]& function. This is very similar to the
26178 ciphersuite specification in OpenSSL.
26180 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
26181 and controls both protocols and ciphers.
26183 The &%tls_require_ciphers%& option is available both as an global option,
26184 controlling how Exim behaves as a server, and also as an option of the
26185 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
26186 the value is string expanded. The resulting string is not an Exim list and
26187 the string is given to the GnuTLS library, so that Exim does not need to be
26188 aware of future feature enhancements of GnuTLS.
26190 Documentation of the strings accepted may be found in the GnuTLS manual, under
26191 "Priority strings". This is online as
26192 &url(http://www.gnutls.org/manual/html_node/Priority-Strings.html),
26193 but beware that this relates to GnuTLS 3, which may be newer than the version
26194 installed on your system. If you are using GnuTLS 3,
26195 &url(http://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string, then the example code)
26196 on that site can be used to test a given string.
26200 # Disable older versions of protocols
26201 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
26204 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
26205 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
26206 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
26208 This example will let the library defaults be permitted on the MX port, where
26209 there's probably no identity verification anyway, and lowers security further
26210 by increasing compatibility; but this ups the ante on the submission ports
26211 where the administrator might have some influence on the choice of clients
26215 tls_require_ciphers = ${if =={$received_port}{25}\
26221 .section "Configuring an Exim server to use TLS" "SECID182"
26222 .cindex "TLS" "configuring an Exim server"
26223 When Exim has been built with TLS support, it advertises the availability of
26224 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
26225 but not to any others. The default value of this option is unset, which means
26226 that STARTTLS is not advertised at all. This default is chosen because you
26227 need to set some other options in order to make TLS available, and also it is
26228 sensible for systems that want to use TLS only as a client.
26230 If a client issues a STARTTLS command and there is some configuration
26231 problem in the server, the command is rejected with a 454 error. If the client
26232 persists in trying to issue SMTP commands, all except QUIT are rejected
26235 554 Security failure
26237 If a STARTTLS command is issued within an existing TLS session, it is
26238 rejected with a 554 error code.
26240 To enable TLS operations on a server, you must set &%tls_advertise_hosts%& to
26241 match some hosts. You can, of course, set it to * to match all hosts.
26242 However, this is not all you need to do. TLS sessions to a server won't work
26243 without some further configuration at the server end.
26245 It is rumoured that all existing clients that support TLS/SSL use RSA
26246 encryption. To make this work you need to set, in the server,
26248 tls_certificate = /some/file/name
26249 tls_privatekey = /some/file/name
26251 These options are, in fact, expanded strings, so you can make them depend on
26252 the identity of the client that is connected if you wish. The first file
26253 contains the server's X509 certificate, and the second contains the private key
26254 that goes with it. These files need to be
26255 PEM format and readable by the Exim user, and must
26256 always be given as full path names.
26257 The key must not be password-protected.
26258 They can be the same file if both the
26259 certificate and the key are contained within it. If &%tls_privatekey%& is not
26260 set, or if its expansion is forced to fail or results in an empty string, this
26261 is assumed to be the case. The certificate file may also contain intermediate
26262 certificates that need to be sent to the client to enable it to authenticate
26263 the server's certificate.
26265 If you do not understand about certificates and keys, please try to find a
26266 source of this background information, which is not Exim-specific. (There are a
26267 few comments below in section &<<SECTcerandall>>&.)
26269 &*Note*&: These options do not apply when Exim is operating as a client &--
26270 they apply only in the case of a server. If you need to use a certificate in an
26271 Exim client, you must set the options of the same names in an &(smtp)&
26274 With just these options, an Exim server will be able to use TLS. It does not
26275 require the client to have a certificate (but see below for how to insist on
26276 this). There is one other option that may be needed in other situations. If
26278 tls_dhparam = /some/file/name
26280 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
26281 with the parameters contained in the file.
26282 Set this to &`none`& to disable use of DH entirely, by making no prime
26287 This may also be set to a string identifying a standard prime to be used for
26288 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
26289 used is &`ike23`&. There are a few standard primes available, see the
26290 documentation for &%tls_dhparam%& for the complete list.
26296 for a way of generating file data.
26298 The strings supplied for these three options are expanded every time a client
26299 host connects. It is therefore possible to use different certificates and keys
26300 for different hosts, if you so wish, by making use of the client's IP address
26301 in &$sender_host_address$& to control the expansion. If a string expansion is
26302 forced to fail, Exim behaves as if the option is not set.
26304 .cindex "cipher" "logging"
26305 .cindex "log" "TLS cipher"
26306 .vindex "&$tls_in_cipher$&"
26307 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
26308 an incoming TLS connection. It is included in the &'Received:'& header of an
26309 incoming message (by default &-- you can, of course, change this), and it is
26310 also included in the log line that records a message's arrival, keyed by
26311 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
26312 condition can be used to test for specific cipher suites in ACLs.
26314 Once TLS has been established, the ACLs that run for subsequent SMTP commands
26315 can check the name of the cipher suite and vary their actions accordingly. The
26316 cipher suite names vary, depending on which TLS library is being used. For
26317 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
26318 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
26319 documentation for more details.
26321 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
26322 (again depending on the &%tls_cipher%& log selector).
26325 .section "Requesting and verifying client certificates" "SECID183"
26326 .cindex "certificate" "verification of client"
26327 .cindex "TLS" "client certificate verification"
26328 If you want an Exim server to request a certificate when negotiating a TLS
26329 session with a client, you must set either &%tls_verify_hosts%& or
26330 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
26331 apply to all TLS connections. For any host that matches one of these options,
26332 Exim requests a certificate as part of the setup of the TLS session. The
26333 contents of the certificate are verified by comparing it with a list of
26334 expected certificates.
26335 These may be the system default set (depending on library version),
26336 an explicit file or,
26337 depending on library version, a directory, identified by
26338 &%tls_verify_certificates%&.
26340 A file can contain multiple certificates, concatenated end to end. If a
26343 each certificate must be in a separate file, with a name (or a symbolic link)
26344 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
26345 certificate. You can compute the relevant hash by running the command
26347 openssl x509 -hash -noout -in /cert/file
26349 where &_/cert/file_& contains a single certificate.
26351 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
26352 what happens if the client does not supply a certificate, or if the certificate
26353 does not match any of the certificates in the collection named by
26354 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
26355 attempt to set up a TLS session is aborted, and the incoming connection is
26356 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
26357 session continues. ACLs that run for subsequent SMTP commands can detect the
26358 fact that no certificate was verified, and vary their actions accordingly. For
26359 example, you can insist on a certificate before accepting a message for
26360 relaying, but not when the message is destined for local delivery.
26362 .vindex "&$tls_in_peerdn$&"
26363 When a client supplies a certificate (whether it verifies or not), the value of
26364 the Distinguished Name of the certificate is made available in the variable
26365 &$tls_in_peerdn$& during subsequent processing of the message.
26367 .cindex "log" "distinguished name"
26368 Because it is often a long text string, it is not included in the log line or
26369 &'Received:'& header by default. You can arrange for it to be logged, keyed by
26370 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
26371 &%received_header_text%& to change the &'Received:'& header. When no
26372 certificate is supplied, &$tls_in_peerdn$& is empty.
26375 .section "Revoked certificates" "SECID184"
26376 .cindex "TLS" "revoked certificates"
26377 .cindex "revocation list"
26378 .cindex "certificate" "revocation list"
26379 .cindex "OCSP" "stapling"
26380 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
26381 certificates are revoked. If you have such a list, you can pass it to an Exim
26382 server using the global option called &%tls_crl%& and to an Exim client using
26383 an identically named option for the &(smtp)& transport. In each case, the value
26384 of the option is expanded and must then be the name of a file that contains a
26386 The downside is that clients have to periodically re-download a potentially huge
26387 file from every certificate authority they know of.
26389 The way with most moving parts at query time is Online Certificate
26390 Status Protocol (OCSP), where the client verifies the certificate
26391 against an OCSP server run by the CA. This lets the CA track all
26392 usage of the certs. It requires running software with access to the
26393 private key of the CA, to sign the responses to the OCSP queries. OCSP
26394 is based on HTTP and can be proxied accordingly.
26396 The only widespread OCSP server implementation (known to this writer)
26397 comes as part of OpenSSL and aborts on an invalid request, such as
26398 connecting to the port and then disconnecting. This requires
26399 re-entering the passphrase each time some random client does this.
26401 The third way is OCSP Stapling; in this, the server using a certificate
26402 issued by the CA periodically requests an OCSP proof of validity from
26403 the OCSP server, then serves it up inline as part of the TLS
26404 negotiation. This approach adds no extra round trips, does not let the
26405 CA track users, scales well with number of certs issued by the CA and is
26406 resilient to temporary OCSP server failures, as long as the server
26407 starts retrying to fetch an OCSP proof some time before its current
26408 proof expires. The downside is that it requires server support.
26410 Unless Exim is built with the support disabled,
26411 or with GnuTLS earlier than version 3.1.3,
26412 support for OCSP stapling is included.
26414 There is a global option called &%tls_ocsp_file%&.
26415 The file specified therein is expected to be in DER format, and contain
26416 an OCSP proof. Exim will serve it as part of the TLS handshake. This
26417 option will be re-expanded for SNI, if the &%tls_certificate%& option
26418 contains &`tls_in_sni`&, as per other TLS options.
26420 Exim does not at this time implement any support for fetching a new OCSP
26421 proof. The burden is on the administrator to handle this, outside of
26422 Exim. The file specified should be replaced atomically, so that the
26423 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
26424 on each connection, so a new file will be handled transparently on the
26427 When built with OpenSSL Exim will check for a valid next update timestamp
26428 in the OCSP proof; if not present, or if the proof has expired, it will be
26431 For the client to be able to verify the stapled OCSP the server must
26432 also supply, in its stapled information, any intermediate
26433 certificates for the chain leading to the OCSP proof from the signer
26434 of the server certificate. There may be zero or one such. These
26435 intermediate certificates should be added to the server OCSP stapling
26436 file named by &%tls_ocsp_file%&.
26438 Note that the proof only covers the terminal server certificate,
26439 not any of the chain from CA to it.
26441 There is no current way to staple a proof for a client certificate.
26444 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
26445 OCSP server is supplied. The server URL may be included in the
26446 server certificate, if the CA is helpful.
26448 One failure mode seen was the OCSP Signer cert expiring before the end
26449 of validity of the OCSP proof. The checking done by Exim/OpenSSL
26450 noted this as invalid overall, but the re-fetch script did not.
26456 .section "Configuring an Exim client to use TLS" "SECID185"
26457 .cindex "cipher" "logging"
26458 .cindex "log" "TLS cipher"
26459 .cindex "log" "distinguished name"
26460 .cindex "TLS" "configuring an Exim client"
26461 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
26462 deliveries as well as to incoming, the latter one causing logging of the
26463 server certificate's DN. The remaining client configuration for TLS is all
26464 within the &(smtp)& transport.
26466 It is not necessary to set any options to have TLS work in the &(smtp)&
26467 transport. If Exim is built with TLS support, and TLS is advertised by a
26468 server, the &(smtp)& transport always tries to start a TLS session. However,
26469 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
26470 transport) to a list of server hosts for which TLS should not be used.
26472 If you do not want Exim to attempt to send messages unencrypted when an attempt
26473 to set up an encrypted connection fails in any way, you can set
26474 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
26475 those hosts, delivery is always deferred if an encrypted connection cannot be
26476 set up. If there are any other hosts for the address, they are tried in the
26479 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
26480 the message unencrypted. It always does this if the response to STARTTLS is
26481 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
26482 session after a success response code, what happens is controlled by the
26483 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
26484 delivery to this host is deferred, and other hosts (if available) are tried. If
26485 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
26486 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
26487 negotiation fails, Exim closes the current connection (because it is in an
26488 unknown state), opens a new one to the same host, and then tries the delivery
26491 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
26492 transport provide the client with a certificate, which is passed to the server
26493 if it requests it. If the server is Exim, it will request a certificate only if
26494 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
26496 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
26497 specifies a collection of expected server certificates.
26498 These may be the system default set (depeding on library version),
26500 depnding on liibrary version, a directory,
26501 must name a file or,
26502 for OpenSSL only (not GnuTLS), a directory.
26503 The client verifies the server's certificate
26504 against this collection, taking into account any revoked certificates that are
26505 in the list defined by &%tls_crl%&.
26506 Failure to verify fails the TLS connection unless either of the
26507 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
26509 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
26510 certificate verification to the listed servers. Verification either must
26511 or need not succeed respectively.
26513 The &(smtp)& transport has two OCSP-related options:
26514 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
26515 is requested and required for the connection to proceed. The default
26517 &%hosts_request_ocsp%&; a host-list for which (additionally)
26518 a Certificate Status is requested (but not necessarily verified). The default
26519 value is "*" meaning that requests are made unless configured
26522 The host(s) should also be in &%hosts_require_tls%&, and
26523 &%tls_verify_certificates%& configured for the transport,
26524 for OCSP to be relevant.
26527 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
26528 list of permitted cipher suites. If either of these checks fails, delivery to
26529 the current host is abandoned, and the &(smtp)& transport tries to deliver to
26530 alternative hosts, if any.
26533 These options must be set in the &(smtp)& transport for Exim to use TLS when it
26534 is operating as a client. Exim does not assume that a server certificate (set
26535 by the global options of the same name) should also be used when operating as a
26539 .vindex "&$host_address$&"
26540 All the TLS options in the &(smtp)& transport are expanded before use, with
26541 &$host$& and &$host_address$& containing the name and address of the server to
26542 which the client is connected. Forced failure of an expansion causes Exim to
26543 behave as if the relevant option were unset.
26545 .vindex &$tls_out_bits$&
26546 .vindex &$tls_out_cipher$&
26547 .vindex &$tls_out_peerdn$&
26548 .vindex &$tls_out_sni$&
26549 Before an SMTP connection is established, the
26550 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
26551 variables are emptied. (Until the first connection, they contain the values
26552 that were set when the message was received.) If STARTTLS is subsequently
26553 successfully obeyed, these variables are set to the relevant values for the
26554 outgoing connection.
26558 .section "Use of TLS Server Name Indication" "SECTtlssni"
26559 .cindex "TLS" "Server Name Indication"
26560 .vindex "&$tls_in_sni$&"
26561 .oindex "&%tls_in_sni%&"
26562 With TLS1.0 or above, there is an extension mechanism by which extra
26563 information can be included at various points in the protocol. One of these
26564 extensions, documented in RFC 6066 (and before that RFC 4366) is
26565 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
26566 client in the initial handshake, so that the server can examine the servername
26567 within and possibly choose to use different certificates and keys (and more)
26570 This is analagous to HTTP's &"Host:"& header, and is the main mechanism by
26571 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
26574 With SMTP to MX, there are the same problems here as in choosing the identity
26575 against which to validate a certificate: you can't rely on insecure DNS to
26576 provide the identity which you then cryptographically verify. So this will
26577 be of limited use in that environment.
26579 With SMTP to Submission, there is a well-defined hostname which clients are
26580 connecting to and can validate certificates against. Thus clients &*can*&
26581 choose to include this information in the TLS negotiation. If this becomes
26582 wide-spread, then hosters can choose to present different certificates to
26583 different clients. Or even negotiate different cipher suites.
26585 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
26586 if not empty, will be sent on a TLS session as part of the handshake. There's
26587 nothing more to it. Choosing a sensible value not derived insecurely is the
26588 only point of caution. The &$tls_out_sni$& variable will be set to this string
26589 for the lifetime of the client connection (including during authentication).
26591 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
26592 received from a client.
26593 It can be logged with the &%log_selector%& item &`+tls_sni`&.
26595 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
26596 option (prior to expansion) then the following options will be re-expanded
26597 during TLS session handshake, to permit alternative values to be chosen:
26600 .vindex "&%tls_certificate%&"
26601 &%tls_certificate%&
26603 .vindex "&%tls_crl%&"
26606 .vindex "&%tls_privatekey%&"
26609 .vindex "&%tls_verify_certificates%&"
26610 &%tls_verify_certificates%&
26612 .vindex "&%tls_ocsp_file%&"
26613 &%tls_verify_certificates%&
26616 Great care should be taken to deal with matters of case, various injection
26617 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
26618 can always be referenced; it is important to remember that &$tls_sni$& is
26619 arbitrary unverified data provided prior to authentication.
26621 The Exim developers are proceeding cautiously and so far no other TLS options
26624 When Exim is built againt OpenSSL, OpenSSL must have been built with support
26625 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
26626 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
26627 see &`-servername`& in the output, then OpenSSL has support.
26629 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
26630 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
26631 built, then you have SNI support).
26635 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
26637 .cindex "multiple SMTP deliveries with TLS"
26638 .cindex "TLS" "multiple message deliveries"
26639 Exim sends multiple messages down the same TCP/IP connection by starting up
26640 an entirely new delivery process for each message, passing the socket from
26641 one process to the next. This implementation does not fit well with the use
26642 of TLS, because there is quite a lot of state information associated with a TLS
26643 connection, not just a socket identification. Passing all the state information
26644 to a new process is not feasible. Consequently, Exim shuts down an existing TLS
26645 session before passing the socket to a new process. The new process may then
26646 try to start a new TLS session, and if successful, may try to re-authenticate
26647 if AUTH is in use, before sending the next message.
26649 The RFC is not clear as to whether or not an SMTP session continues in clear
26650 after TLS has been shut down, or whether TLS may be restarted again later, as
26651 just described. However, if the server is Exim, this shutdown and
26652 reinitialization works. It is not known which (if any) other servers operate
26653 successfully if the client closes a TLS session and continues with unencrypted
26654 SMTP, but there are certainly some that do not work. For such servers, Exim
26655 should not pass the socket to another process, because the failure of the
26656 subsequent attempt to use it would cause Exim to record a temporary host error,
26657 and delay other deliveries to that host.
26659 To test for this case, Exim sends an EHLO command to the server after
26660 closing down the TLS session. If this fails in any way, the connection is
26661 closed instead of being passed to a new delivery process, but no retry
26662 information is recorded.
26664 There is also a manual override; you can set &%hosts_nopass_tls%& on the
26665 &(smtp)& transport to match those hosts for which Exim should not pass
26666 connections to new processes if TLS has been used.
26671 .section "Certificates and all that" "SECTcerandall"
26672 .cindex "certificate" "references to discussion"
26673 In order to understand fully how TLS works, you need to know about
26674 certificates, certificate signing, and certificate authorities. This is not the
26675 place to give a tutorial, especially as I do not know very much about it
26676 myself. Some helpful introduction can be found in the FAQ for the SSL addition
26677 to Apache, currently at
26679 &url(http://www.modssl.org/docs/2.7/ssl_faq.html#ToC24)
26681 Other parts of the &'modssl'& documentation are also helpful, and have
26682 links to further files.
26683 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
26684 0-201-61598-3), contains both introductory and more in-depth descriptions.
26685 Some sample programs taken from the book are available from
26687 &url(http://www.rtfm.com/openssl-examples/)
26691 .section "Certificate chains" "SECID186"
26692 The file named by &%tls_certificate%& may contain more than one
26693 certificate. This is useful in the case where the certificate that is being
26694 sent is validated by an intermediate certificate which the other end does
26695 not have. Multiple certificates must be in the correct order in the file.
26696 First the host's certificate itself, then the first intermediate
26697 certificate to validate the issuer of the host certificate, then the next
26698 intermediate certificate to validate the issuer of the first intermediate
26699 certificate, and so on, until finally (optionally) the root certificate.
26700 The root certificate must already be trusted by the recipient for
26701 validation to succeed, of course, but if it's not preinstalled, sending the
26702 root certificate along with the rest makes it available for the user to
26703 install if the receiving end is a client MUA that can interact with a user.
26705 Note that certificates using MD5 are unlikely to work on today's Internet;
26706 even if your libraries allow loading them for use in Exim when acting as a
26707 server, increasingly clients will not accept such certificates. The error
26708 diagnostics in such a case can be frustratingly vague.
26712 .section "Self-signed certificates" "SECID187"
26713 .cindex "certificate" "self-signed"
26714 You can create a self-signed certificate using the &'req'& command provided
26715 with OpenSSL, like this:
26716 . ==== Do not shorten the duration here without reading and considering
26717 . ==== the text below. Please leave it at 9999 days.
26719 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
26722 &_file1_& and &_file2_& can be the same file; the key and the certificate are
26723 delimited and so can be identified independently. The &%-days%& option
26724 specifies a period for which the certificate is valid. The &%-nodes%& option is
26725 important: if you do not set it, the key is encrypted with a passphrase
26726 that you are prompted for, and any use that is made of the key causes more
26727 prompting for the passphrase. This is not helpful if you are going to use
26728 this certificate and key in an MTA, where prompting is not possible.
26730 . ==== I expect to still be working 26 years from now. The less technical
26731 . ==== debt I create, in terms of storing up trouble for my later years, the
26732 . ==== happier I will be then. We really have reached the point where we
26733 . ==== should start, at the very least, provoking thought and making folks
26734 . ==== pause before proceeding, instead of leaving all the fixes until two
26735 . ==== years before 2^31 seconds after the 1970 Unix epoch.
26737 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
26738 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
26739 the above command might produce a date in the past. Think carefully about
26740 the lifetime of the systems you're deploying, and either reduce the duration
26741 of the certificate or reconsider your platform deployment. (At time of
26742 writing, reducing the duration is the most likely choice, but the inexorable
26743 progression of time takes us steadily towards an era where this will not
26744 be a sensible resolution).
26746 A self-signed certificate made in this way is sufficient for testing, and
26747 may be adequate for all your requirements if you are mainly interested in
26748 encrypting transfers, and not in secure identification.
26750 However, many clients require that the certificate presented by the server be a
26751 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
26752 certificate. In this situation, the self-signed certificate described above
26753 must be installed on the client host as a trusted root &'certification
26754 authority'& (CA), and the certificate used by Exim must be a user certificate
26755 signed with that self-signed certificate.
26757 For information on creating self-signed CA certificates and using them to sign
26758 user certificates, see the &'General implementation overview'& chapter of the
26759 Open-source PKI book, available online at
26760 &url(http://ospkibook.sourceforge.net/).
26761 .ecindex IIDencsmtp1
26762 .ecindex IIDencsmtp2
26766 . ////////////////////////////////////////////////////////////////////////////
26767 . ////////////////////////////////////////////////////////////////////////////
26769 .chapter "Access control lists" "CHAPACL"
26770 .scindex IIDacl "&ACL;" "description"
26771 .cindex "control of incoming mail"
26772 .cindex "message" "controlling incoming"
26773 .cindex "policy control" "access control lists"
26774 Access Control Lists (ACLs) are defined in a separate section of the run time
26775 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
26776 name, terminated by a colon. Here is a complete ACL section that contains just
26777 one very small ACL:
26781 accept hosts = one.host.only
26783 You can have as many lists as you like in the ACL section, and the order in
26784 which they appear does not matter. The lists are self-terminating.
26786 The majority of ACLs are used to control Exim's behaviour when it receives
26787 certain SMTP commands. This applies both to incoming TCP/IP connections, and
26788 when a local process submits a message using SMTP by specifying the &%-bs%&
26789 option. The most common use is for controlling which recipients are accepted
26790 in incoming messages. In addition, you can define an ACL that is used to check
26791 local non-SMTP messages. The default configuration file contains an example of
26792 a realistic ACL for checking RCPT commands. This is discussed in chapter
26793 &<<CHAPdefconfil>>&.
26796 .section "Testing ACLs" "SECID188"
26797 The &%-bh%& command line option provides a way of testing your ACL
26798 configuration locally by running a fake SMTP session with which you interact.
26799 The host &'relay-test.mail-abuse.org'& provides a service for checking your
26800 relaying configuration (see section &<<SECTcheralcon>>& for more details).
26804 .section "Specifying when ACLs are used" "SECID189"
26805 .cindex "&ACL;" "options for specifying"
26806 In order to cause an ACL to be used, you have to name it in one of the relevant
26807 options in the main part of the configuration. These options are:
26808 .cindex "AUTH" "ACL for"
26809 .cindex "DATA" "ACLs for"
26810 .cindex "ETRN" "ACL for"
26811 .cindex "EXPN" "ACL for"
26812 .cindex "HELO" "ACL for"
26813 .cindex "EHLO" "ACL for"
26814 .cindex "MAIL" "ACL for"
26815 .cindex "QUIT, ACL for"
26816 .cindex "RCPT" "ACL for"
26817 .cindex "STARTTLS, ACL for"
26818 .cindex "VRFY" "ACL for"
26819 .cindex "SMTP" "connection, ACL for"
26820 .cindex "non-SMTP messages" "ACLs for"
26821 .cindex "MIME content scanning" "ACL for"
26822 .cindex "PRDR" "ACL for"
26825 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
26826 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
26827 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
26828 .irow &%acl_smtp_auth%& "ACL for AUTH"
26829 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
26830 .irow &%acl_smtp_data%& "ACL after DATA is complete"
26831 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
26832 .irow &%acl_smtp_etrn%& "ACL for ETRN"
26833 .irow &%acl_smtp_expn%& "ACL for EXPN"
26834 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
26835 .irow &%acl_smtp_mail%& "ACL for MAIL"
26836 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
26837 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
26838 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
26839 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
26840 .irow &%acl_smtp_quit%& "ACL for QUIT"
26841 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
26842 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
26843 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
26846 For example, if you set
26848 acl_smtp_rcpt = small_acl
26850 the little ACL defined above is used whenever Exim receives a RCPT command
26851 in an SMTP dialogue. The majority of policy tests on incoming messages can be
26852 done when RCPT commands arrive. A rejection of RCPT should cause the
26853 sending MTA to give up on the recipient address contained in the RCPT
26854 command, whereas rejection at other times may cause the client MTA to keep on
26855 trying to deliver the message. It is therefore recommended that you do as much
26856 testing as possible at RCPT time.
26859 .section "The non-SMTP ACLs" "SECID190"
26860 .cindex "non-SMTP messages" "ACLs for"
26861 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
26862 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
26863 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
26864 the state of the SMTP connection such as encryption and authentication) are not
26865 relevant and are forbidden in these ACLs. However, the sender and recipients
26866 are known, so the &%senders%& and &%sender_domains%& conditions and the
26867 &$sender_address$& and &$recipients$& variables can be used. Variables such as
26868 &$authenticated_sender$& are also available. You can specify added header lines
26869 in any of these ACLs.
26871 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
26872 non-SMTP message, before any of the message has been read. (This is the
26873 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
26874 batched SMTP input, it runs after the DATA command has been reached. The
26875 result of this ACL is ignored; it cannot be used to reject a message. If you
26876 really need to, you could set a value in an ACL variable here and reject based
26877 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
26878 controls, and in particular, it can be used to set
26880 control = suppress_local_fixups
26882 This cannot be used in the other non-SMTP ACLs because by the time they are
26883 run, it is too late.
26885 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
26886 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
26888 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
26889 kind of rejection is treated as permanent, because there is no way of sending a
26890 temporary error for these kinds of message.
26893 .section "The SMTP connect ACL" "SECID191"
26894 .cindex "SMTP" "connection, ACL for"
26895 .oindex &%smtp_banner%&
26896 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
26897 session, after the test specified by &%host_reject_connection%& (which is now
26898 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
26899 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
26900 the message override the banner message that is otherwise specified by the
26901 &%smtp_banner%& option.
26904 .section "The EHLO/HELO ACL" "SECID192"
26905 .cindex "EHLO" "ACL for"
26906 .cindex "HELO" "ACL for"
26907 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
26908 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
26909 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
26910 Note that a client may issue more than one EHLO or HELO command in an SMTP
26911 session, and indeed is required to issue a new EHLO or HELO after successfully
26912 setting up encryption following a STARTTLS command.
26914 If the command is accepted by an &%accept%& verb that has a &%message%&
26915 modifier, the message may not contain more than one line (it will be truncated
26916 at the first newline and a panic logged if it does). Such a message cannot
26917 affect the EHLO options that are listed on the second and subsequent lines of
26921 .section "The DATA ACLs" "SECID193"
26922 .cindex "DATA" "ACLs for"
26923 Two ACLs are associated with the DATA command, because it is two-stage
26924 command, with two responses being sent to the client.
26925 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
26926 is obeyed. This gives you control after all the RCPT commands, but before
26927 the message itself is received. It offers the opportunity to give a negative
26928 response to the DATA command before the data is transmitted. Header lines
26929 added by MAIL or RCPT ACLs are not visible at this time, but any that
26930 are defined here are visible when the &%acl_smtp_data%& ACL is run.
26932 You cannot test the contents of the message, for example, to verify addresses
26933 in the headers, at RCPT time or when the DATA command is received. Such
26934 tests have to appear in the ACL that is run after the message itself has been
26935 received, before the final response to the DATA command is sent. This is
26936 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
26937 associated with the DATA command.
26939 For both of these ACLs, it is not possible to reject individual recipients. An
26940 error response rejects the entire message. Unfortunately, it is known that some
26941 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
26942 before or after the data) correctly &-- they keep the message on their queues
26943 and try again later, but that is their problem, though it does waste some of
26946 The &%acl_smtp_data%& ACL is run after
26947 the &%acl_smtp_data_prdr%&,
26948 the &%acl_smtp_dkim%&
26949 and the &%acl_smtp_mime%& ACLs.
26951 .section "The SMTP DKIM ACL" "SECTDKIMACL"
26952 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
26953 enabled (which is the default).
26955 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
26956 received, and is executed for each DKIM signature found in a message. If not
26957 otherwise specified, the default action is to accept.
26959 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
26961 For details on the operation of DKIM, see chapter &<<CHAPdkim>>&.
26964 .section "The SMTP MIME ACL" "SECID194"
26965 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
26966 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
26968 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
26971 .section "The SMTP PRDR ACL" "SECTPRDRACL"
26972 .cindex "PRDR" "ACL for"
26973 .oindex "&%prdr_enable%&"
26974 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
26975 with PRDR support enabled (which is the default).
26976 It becomes active only when the PRDR feature is negotiated between
26977 client and server for a message, and more than one recipient
26980 The ACL test specfied by &%acl_smtp_data_prdr%& happens after a message
26981 has been recieved, and is executed once for each recipient of the message
26982 with &$local_part$& and &$domain$& valid.
26983 The test may accept, defer or deny for inividual recipients.
26984 The &%acl_smtp_data%& will still be called after this ACL and
26985 can reject the message overall, even if this ACL has accepted it
26986 for some or all recipients.
26988 PRDR may be used to support per-user content filtering. Without it
26989 one must defer any recipient after the first that has a different
26990 content-filter configuration. With PRDR, the RCPT-time check
26991 for this can be disabled when the MAIL-time $smtp_command included
26992 "PRDR". Any required difference in behaviour of the main DATA-time
26993 ACL should however depend on the PRDR-time ACL having run, as Exim
26994 will avoid doing so in some situations (eg. single-recipient mails).
26996 See also the &%prdr_enable%& global option
26997 and the &%hosts_try_prdr%& smtp transport option.
26999 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
27000 If the ACL is not defined, processing completes as if
27001 the feature was not requested by the client.
27003 .section "The QUIT ACL" "SECTQUITACL"
27004 .cindex "QUIT, ACL for"
27005 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
27006 does not affect the response code to QUIT, which is always 221. Thus, the ACL
27007 does not in fact control any access. For this reason, the only verbs that are
27008 permitted are &%accept%& and &%warn%&.
27010 This ACL can be used for tasks such as custom logging at the end of an SMTP
27011 session. For example, you can use ACL variables in other ACLs to count
27012 messages, recipients, etc., and log the totals at QUIT time using one or
27013 more &%logwrite%& modifiers on a &%warn%& verb.
27015 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
27016 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
27018 You do not need to have a final &%accept%&, but if you do, you can use a
27019 &%message%& modifier to specify custom text that is sent as part of the 221
27022 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
27023 failure (for example, failure to open a log file, or when Exim is bombing out
27024 because it has detected an unrecoverable error), all SMTP commands from the
27025 client are given temporary error responses until QUIT is received or the
27026 connection is closed. In these special cases, the QUIT ACL does not run.
27029 .section "The not-QUIT ACL" "SECTNOTQUITACL"
27030 .vindex &$acl_smtp_notquit$&
27031 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
27032 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
27033 trouble, such as being unable to write to its log files, this ACL is not run,
27034 because it might try to do things (such as write to log files) that make the
27035 situation even worse.
27037 Like the QUIT ACL, this ACL is provided to make it possible to do customized
27038 logging or to gather statistics, and its outcome is ignored. The &%delay%&
27039 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
27042 .vindex &$smtp_notquit_reason$&
27043 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
27044 to a string that indicates the reason for the termination of the SMTP
27045 connection. The possible values are:
27047 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
27048 .irow &`bad-commands`& "Too many unknown or non-mail commands"
27049 .irow &`command-timeout`& "Timeout while reading SMTP commands"
27050 .irow &`connection-lost`& "The SMTP connection has been lost"
27051 .irow &`data-timeout`& "Timeout while reading message data"
27052 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
27053 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
27054 .irow &`signal-exit`& "SIGTERM or SIGINT"
27055 .irow &`synchronization-error`& "SMTP synchronization error"
27056 .irow &`tls-failed`& "TLS failed to start"
27058 In most cases when an SMTP connection is closed without having received QUIT,
27059 Exim sends an SMTP response message before actually closing the connection.
27060 With the exception of the &`acl-drop`& case, the default message can be
27061 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
27062 &%drop%& verb in another ACL, it is the message from the other ACL that is
27066 .section "Finding an ACL to use" "SECID195"
27067 .cindex "&ACL;" "finding which to use"
27068 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
27069 you can use different ACLs in different circumstances. For example,
27071 acl_smtp_rcpt = ${if ={25}{$interface_port} \
27072 {acl_check_rcpt} {acl_check_rcpt_submit} }
27074 In the default configuration file there are some example settings for
27075 providing an RFC 4409 message submission service on port 587 and a
27076 non-standard &"smtps"& service on port 465. You can use a string
27077 expansion like this to choose an ACL for MUAs on these ports which is
27078 more appropriate for this purpose than the default ACL on port 25.
27080 The expanded string does not have to be the name of an ACL in the
27081 configuration file; there are other possibilities. Having expanded the
27082 string, Exim searches for an ACL as follows:
27085 If the string begins with a slash, Exim uses it as a file name, and reads its
27086 contents as an ACL. The lines are processed in the same way as lines in the
27087 Exim configuration file. In particular, continuation lines are supported, blank
27088 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
27089 If the file does not exist or cannot be read, an error occurs (typically
27090 causing a temporary failure of whatever caused the ACL to be run). For example:
27092 acl_smtp_data = /etc/acls/\
27093 ${lookup{$sender_host_address}lsearch\
27094 {/etc/acllist}{$value}{default}}
27096 This looks up an ACL file to use on the basis of the host's IP address, falling
27097 back to a default if the lookup fails. If an ACL is successfully read from a
27098 file, it is retained in memory for the duration of the Exim process, so that it
27099 can be re-used without having to re-read the file.
27101 If the string does not start with a slash, and does not contain any spaces,
27102 Exim searches the ACL section of the configuration for an ACL whose name
27103 matches the string.
27105 If no named ACL is found, or if the string contains spaces, Exim parses
27106 the string as an inline ACL. This can save typing in cases where you just
27107 want to have something like
27109 acl_smtp_vrfy = accept
27111 in order to allow free use of the VRFY command. Such a string may contain
27112 newlines; it is processed in the same way as an ACL that is read from a file.
27118 .section "ACL return codes" "SECID196"
27119 .cindex "&ACL;" "return codes"
27120 Except for the QUIT ACL, which does not affect the SMTP return code (see
27121 section &<<SECTQUITACL>>& above), the result of running an ACL is either
27122 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
27123 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
27124 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
27125 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
27126 This also causes a 4&'xx'& return code.
27128 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
27129 &"deny"&, because there is no mechanism for passing temporary errors to the
27130 submitters of non-SMTP messages.
27133 ACLs that are relevant to message reception may also return &"discard"&. This
27134 has the effect of &"accept"&, but causes either the entire message or an
27135 individual recipient address to be discarded. In other words, it is a
27136 blackholing facility. Use it with care.
27138 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
27139 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
27140 RCPT ACL is to discard just the one recipient address. If there are no
27141 recipients left when the message's data is received, the DATA ACL is not
27142 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
27143 remaining recipients. The &"discard"& return is not permitted for the
27144 &%acl_smtp_predata%& ACL.
27147 .cindex "&[local_scan()]& function" "when all recipients discarded"
27148 The &[local_scan()]& function is always run, even if there are no remaining
27149 recipients; it may create new recipients.
27153 .section "Unset ACL options" "SECID197"
27154 .cindex "&ACL;" "unset options"
27155 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
27156 all the same. &*Note*&: These defaults apply only when the relevant ACL is
27157 not defined at all. For any defined ACL, the default action when control
27158 reaches the end of the ACL statements is &"deny"&.
27160 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
27161 these two are ACLs that are used only for their side effects. They cannot be
27162 used to accept or reject anything.
27164 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
27165 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
27166 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
27167 when the ACL is not defined is &"accept"&.
27169 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
27170 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
27171 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
27172 messages over an SMTP connection. For an example, see the ACL in the default
27173 configuration file.
27178 .section "Data for message ACLs" "SECID198"
27179 .cindex "&ACL;" "data for message ACL"
27181 .vindex &$local_part$&
27182 .vindex &$sender_address$&
27183 .vindex &$sender_host_address$&
27184 .vindex &$smtp_command$&
27185 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
27186 that contain information about the host and the message's sender (for example,
27187 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
27188 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
27189 &$local_part$& are set from the argument address. The entire SMTP command
27190 is available in &$smtp_command$&.
27192 When an ACL for the AUTH parameter of MAIL is running, the variables that
27193 contain information about the host are set, but &$sender_address$& is not yet
27194 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
27197 .vindex "&$message_size$&"
27198 The &$message_size$& variable is set to the value of the SIZE parameter on
27199 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
27200 that parameter is not given. The value is updated to the true message size by
27201 the time the final DATA ACL is run (after the message data has been
27204 .vindex "&$rcpt_count$&"
27205 .vindex "&$recipients_count$&"
27206 The &$rcpt_count$& variable increases by one for each RCPT command received.
27207 The &$recipients_count$& variable increases by one each time a RCPT command is
27208 accepted, so while an ACL for RCPT is being processed, it contains the number
27209 of previously accepted recipients. At DATA time (for both the DATA ACLs),
27210 &$rcpt_count$& contains the total number of RCPT commands, and
27211 &$recipients_count$& contains the total number of accepted recipients.
27217 .section "Data for non-message ACLs" "SECTdatfornon"
27218 .cindex "&ACL;" "data for non-message ACL"
27219 .vindex &$smtp_command_argument$&
27220 .vindex &$smtp_command$&
27221 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
27222 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
27223 and the entire SMTP command is available in &$smtp_command$&.
27224 These variables can be tested using a &%condition%& condition. For example,
27225 here is an ACL for use with AUTH, which insists that either the session is
27226 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
27227 does not permit authentication methods that use cleartext passwords on
27228 unencrypted connections.
27231 accept encrypted = *
27232 accept condition = ${if eq{${uc:$smtp_command_argument}}\
27234 deny message = TLS encryption or CRAM-MD5 required
27236 (Another way of applying this restriction is to arrange for the authenticators
27237 that use cleartext passwords not to be advertised when the connection is not
27238 encrypted. You can use the generic &%server_advertise_condition%& authenticator
27239 option to do this.)
27243 .section "Format of an ACL" "SECID199"
27244 .cindex "&ACL;" "format of"
27245 .cindex "&ACL;" "verbs, definition of"
27246 An individual ACL consists of a number of statements. Each statement starts
27247 with a verb, optionally followed by a number of conditions and &"modifiers"&.
27248 Modifiers can change the way the verb operates, define error and log messages,
27249 set variables, insert delays, and vary the processing of accepted messages.
27251 If all the conditions are met, the verb is obeyed. The same condition may be
27252 used (with different arguments) more than once in the same statement. This
27253 provides a means of specifying an &"and"& conjunction between conditions. For
27256 deny dnslists = list1.example
27257 dnslists = list2.example
27259 If there are no conditions, the verb is always obeyed. Exim stops evaluating
27260 the conditions and modifiers when it reaches a condition that fails. What
27261 happens then depends on the verb (and in one case, on a special modifier). Not
27262 all the conditions make sense at every testing point. For example, you cannot
27263 test a sender address in the ACL that is run for a VRFY command.
27266 .section "ACL verbs" "SECID200"
27267 The ACL verbs are as follows:
27270 .cindex "&%accept%& ACL verb"
27271 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
27272 of the conditions are not met, what happens depends on whether &%endpass%&
27273 appears among the conditions (for syntax see below). If the failing condition
27274 is before &%endpass%&, control is passed to the next ACL statement; if it is
27275 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
27276 check a RCPT command:
27278 accept domains = +local_domains
27282 If the recipient domain does not match the &%domains%& condition, control
27283 passes to the next statement. If it does match, the recipient is verified, and
27284 the command is accepted if verification succeeds. However, if verification
27285 fails, the ACL yields &"deny"&, because the failing condition is after
27288 The &%endpass%& feature has turned out to be confusing to many people, so its
27289 use is not recommended nowadays. It is always possible to rewrite an ACL so
27290 that &%endpass%& is not needed, and it is no longer used in the default
27293 .cindex "&%message%& ACL modifier" "with &%accept%&"
27294 If a &%message%& modifier appears on an &%accept%& statement, its action
27295 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
27296 (when an &%accept%& verb either accepts or passes control to the next
27297 statement), &%message%& can be used to vary the message that is sent when an
27298 SMTP command is accepted. For example, in a RCPT ACL you could have:
27300 &`accept `&<&'some conditions'&>
27301 &` message = OK, I will allow you through today`&
27303 You can specify an SMTP response code, optionally followed by an &"extended
27304 response code"& at the start of the message, but the first digit must be the
27305 same as would be sent by default, which is 2 for an &%accept%& verb.
27307 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
27308 an error message that is used when access is denied. This behaviour is retained
27309 for backward compatibility, but current &"best practice"& is to avoid the use
27314 .cindex "&%defer%& ACL verb"
27315 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
27316 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
27317 &%defer%& is the same as &%deny%&, because there is no way of sending a
27318 temporary error. For a RCPT command, &%defer%& is much the same as using a
27319 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
27320 be used in any ACL, and even for a recipient it might be a simpler approach.
27324 .cindex "&%deny%& ACL verb"
27325 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
27326 the conditions are not met, control is passed to the next ACL statement. For
27329 deny dnslists = blackholes.mail-abuse.org
27331 rejects commands from hosts that are on a DNS black list.
27335 .cindex "&%discard%& ACL verb"
27336 &%discard%&: This verb behaves like &%accept%&, except that it returns
27337 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
27338 that are concerned with receiving messages. When all the conditions are true,
27339 the sending entity receives a &"success"& response. However, &%discard%& causes
27340 recipients to be discarded. If it is used in an ACL for RCPT, just the one
27341 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
27342 message's recipients are discarded. Recipients that are discarded before DATA
27343 do not appear in the log line when the &%received_recipients%& log selector is set.
27345 If the &%log_message%& modifier is set when &%discard%& operates,
27346 its contents are added to the line that is automatically written to the log.
27347 The &%message%& modifier operates exactly as it does for &%accept%&.
27351 .cindex "&%drop%& ACL verb"
27352 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
27353 forcibly closed after the 5&'xx'& error message has been sent. For example:
27355 drop message = I don't take more than 20 RCPTs
27356 condition = ${if > {$rcpt_count}{20}}
27358 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
27359 The connection is always dropped after sending a 550 response.
27362 .cindex "&%require%& ACL verb"
27363 &%require%&: If all the conditions are met, control is passed to the next ACL
27364 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
27365 example, when checking a RCPT command,
27367 require message = Sender did not verify
27370 passes control to subsequent statements only if the message's sender can be
27371 verified. Otherwise, it rejects the command. Note the positioning of the
27372 &%message%& modifier, before the &%verify%& condition. The reason for this is
27373 discussed in section &<<SECTcondmodproc>>&.
27376 .cindex "&%warn%& ACL verb"
27377 &%warn%&: If all the conditions are true, a line specified by the
27378 &%log_message%& modifier is written to Exim's main log. Control always passes
27379 to the next ACL statement. If any condition is false, the log line is not
27380 written. If an identical log line is requested several times in the same
27381 message, only one copy is actually written to the log. If you want to force
27382 duplicates to be written, use the &%logwrite%& modifier instead.
27384 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
27385 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
27386 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
27387 first failing condition. There is more about adding header lines in section
27388 &<<SECTaddheadacl>>&.
27390 If any condition on a &%warn%& statement cannot be completed (that is, there is
27391 some sort of defer), the log line specified by &%log_message%& is not written.
27392 This does not include the case of a forced failure from a lookup, which
27393 is considered to be a successful completion. After a defer, no further
27394 conditions or modifiers in the &%warn%& statement are processed. The incident
27395 is logged, and the ACL continues to be processed, from the next statement
27399 .vindex "&$acl_verify_message$&"
27400 When one of the &%warn%& conditions is an address verification that fails, the
27401 text of the verification failure message is in &$acl_verify_message$&. If you
27402 want this logged, you must set it up explicitly. For example:
27404 warn !verify = sender
27405 log_message = sender verify failed: $acl_verify_message
27409 At the end of each ACL there is an implicit unconditional &%deny%&.
27411 As you can see from the examples above, the conditions and modifiers are
27412 written one to a line, with the first one on the same line as the verb, and
27413 subsequent ones on following lines. If you have a very long condition, you can
27414 continue it onto several physical lines by the usual backslash continuation
27415 mechanism. It is conventional to align the conditions vertically.
27419 .section "ACL variables" "SECTaclvariables"
27420 .cindex "&ACL;" "variables"
27421 There are some special variables that can be set during ACL processing. They
27422 can be used to pass information between different ACLs, different invocations
27423 of the same ACL in the same SMTP connection, and between ACLs and the routers,
27424 transports, and filters that are used to deliver a message. The names of these
27425 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
27426 an underscore, but the remainder of the name can be any sequence of
27427 alphanumeric characters and underscores that you choose. There is no limit on
27428 the number of ACL variables. The two sets act as follows:
27430 The values of those variables whose names begin with &$acl_c$& persist
27431 throughout an SMTP connection. They are never reset. Thus, a value that is set
27432 while receiving one message is still available when receiving the next message
27433 on the same SMTP connection.
27435 The values of those variables whose names begin with &$acl_m$& persist only
27436 while a message is being received. They are reset afterwards. They are also
27437 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
27440 When a message is accepted, the current values of all the ACL variables are
27441 preserved with the message and are subsequently made available at delivery
27442 time. The ACL variables are set by a modifier called &%set%&. For example:
27444 accept hosts = whatever
27445 set acl_m4 = some value
27446 accept authenticated = *
27447 set acl_c_auth = yes
27449 &*Note*&: A leading dollar sign is not used when naming a variable that is to
27450 be set. If you want to set a variable without taking any action, you can use a
27451 &%warn%& verb without any other modifiers or conditions.
27453 .oindex &%strict_acl_vars%&
27454 What happens if a syntactically valid but undefined ACL variable is
27455 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
27456 false (the default), an empty string is substituted; if it is true, an
27457 error is generated.
27459 Versions of Exim before 4.64 have a limited set of numbered variables, but
27460 their names are compatible, so there is no problem with upgrading.
27463 .section "Condition and modifier processing" "SECTcondmodproc"
27464 .cindex "&ACL;" "conditions; processing"
27465 .cindex "&ACL;" "modifiers; processing"
27466 An exclamation mark preceding a condition negates its result. For example:
27468 deny domains = *.dom.example
27469 !verify = recipient
27471 causes the ACL to return &"deny"& if the recipient domain ends in
27472 &'dom.example'& and the recipient address cannot be verified. Sometimes
27473 negation can be used on the right-hand side of a condition. For example, these
27474 two statements are equivalent:
27476 deny hosts = !192.168.3.4
27477 deny !hosts = 192.168.3.4
27479 However, for many conditions (&%verify%& being a good example), only left-hand
27480 side negation of the whole condition is possible.
27482 The arguments of conditions and modifiers are expanded. A forced failure
27483 of an expansion causes a condition to be ignored, that is, it behaves as if the
27484 condition is true. Consider these two statements:
27486 accept senders = ${lookup{$host_name}lsearch\
27487 {/some/file}{$value}fail}
27488 accept senders = ${lookup{$host_name}lsearch\
27489 {/some/file}{$value}{}}
27491 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
27492 the returned list is searched, but if the lookup fails the behaviour is
27493 different in the two cases. The &%fail%& in the first statement causes the
27494 condition to be ignored, leaving no further conditions. The &%accept%& verb
27495 therefore succeeds. The second statement, however, generates an empty list when
27496 the lookup fails. No sender can match an empty list, so the condition fails,
27497 and therefore the &%accept%& also fails.
27499 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
27500 specify actions that are taken as the conditions for a statement are checked;
27501 others specify text for messages that are used when access is denied or a
27502 warning is generated. The &%control%& modifier affects the way an incoming
27503 message is handled.
27505 The positioning of the modifiers in an ACL statement is important, because the
27506 processing of a verb ceases as soon as its outcome is known. Only those
27507 modifiers that have already been encountered will take effect. For example,
27508 consider this use of the &%message%& modifier:
27510 require message = Can't verify sender
27512 message = Can't verify recipient
27514 message = This message cannot be used
27516 If sender verification fails, Exim knows that the result of the statement is
27517 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
27518 so its text is used as the error message. If sender verification succeeds, but
27519 recipient verification fails, the second message is used. If recipient
27520 verification succeeds, the third message becomes &"current"&, but is never used
27521 because there are no more conditions to cause failure.
27523 For the &%deny%& verb, on the other hand, it is always the last &%message%&
27524 modifier that is used, because all the conditions must be true for rejection to
27525 happen. Specifying more than one &%message%& modifier does not make sense, and
27526 the message can even be specified after all the conditions. For example:
27529 !senders = *@my.domain.example
27530 message = Invalid sender from client host
27532 The &"deny"& result does not happen until the end of the statement is reached,
27533 by which time Exim has set up the message.
27537 .section "ACL modifiers" "SECTACLmodi"
27538 .cindex "&ACL;" "modifiers; list of"
27539 The ACL modifiers are as follows:
27542 .vitem &*add_header*&&~=&~<&'text'&>
27543 This modifier specifies one or more header lines that are to be added to an
27544 incoming message, assuming, of course, that the message is ultimately
27545 accepted. For details, see section &<<SECTaddheadacl>>&.
27547 .vitem &*continue*&&~=&~<&'text'&>
27548 .cindex "&%continue%& ACL modifier"
27549 .cindex "database" "updating in ACL"
27550 This modifier does nothing of itself, and processing of the ACL always
27551 continues with the next condition or modifier. The value of &%continue%& is in
27552 the side effects of expanding its argument. Typically this could be used to
27553 update a database. It is really just a syntactic tidiness, to avoid having to
27554 write rather ugly lines like this:
27556 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
27558 Instead, all you need is
27560 &`continue = `&<&'some expansion'&>
27563 .vitem &*control*&&~=&~<&'text'&>
27564 .cindex "&%control%& ACL modifier"
27565 This modifier affects the subsequent processing of the SMTP connection or of an
27566 incoming message that is accepted. The effect of the first type of control
27567 lasts for the duration of the connection, whereas the effect of the second type
27568 lasts only until the current message has been received. The message-specific
27569 controls always apply to the whole message, not to individual recipients,
27570 even if the &%control%& modifier appears in a RCPT ACL.
27572 As there are now quite a few controls that can be applied, they are described
27573 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
27574 in several different ways. For example:
27576 . ==== As this is a nested list, any displays it contains must be indented
27577 . ==== as otherwise they are too far to the left. That comment applies only
27578 . ==== when xmlto and fop are used; formatting with sdop gets it right either
27582 It can be at the end of an &%accept%& statement:
27584 accept ...some conditions
27585 control = queue_only
27587 In this case, the control is applied when this statement yields &"accept"&, in
27588 other words, when the conditions are all true.
27591 It can be in the middle of an &%accept%& statement:
27593 accept ...some conditions...
27594 control = queue_only
27595 ...some more conditions...
27597 If the first set of conditions are true, the control is applied, even if the
27598 statement does not accept because one of the second set of conditions is false.
27599 In this case, some subsequent statement must yield &"accept"& for the control
27603 It can be used with &%warn%& to apply the control, leaving the
27604 decision about accepting or denying to a subsequent verb. For
27607 warn ...some conditions...
27611 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
27612 &%logwrite%&, so it does not add anything to the message and does not write a
27616 If you want to apply a control unconditionally, you can use it with a
27617 &%require%& verb. For example:
27619 require control = no_multiline_responses
27623 .vitem &*delay*&&~=&~<&'time'&>
27624 .cindex "&%delay%& ACL modifier"
27626 This modifier may appear in any ACL except notquit. It causes Exim to wait for
27627 the time interval before proceeding. However, when testing Exim using the
27628 &%-bh%& option, the delay is not actually imposed (an appropriate message is
27629 output instead). The time is given in the usual Exim notation, and the delay
27630 happens as soon as the modifier is processed. In an SMTP session, pending
27631 output is flushed before the delay is imposed.
27633 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
27636 deny ...some conditions...
27639 The delay happens if all the conditions are true, before the statement returns
27640 &"deny"&. Compare this with:
27643 ...some conditions...
27645 which waits for 30s before processing the conditions. The &%delay%& modifier
27646 can also be used with &%warn%& and together with &%control%&:
27648 warn ...some conditions...
27654 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
27655 responses to several commands are no longer buffered and sent in one packet (as
27656 they would normally be) because all output is flushed before imposing the
27657 delay. This optimization is disabled so that a number of small delays do not
27658 appear to the client as one large aggregated delay that might provoke an
27659 unwanted timeout. You can, however, disable output flushing for &%delay%& by
27660 using a &%control%& modifier to set &%no_delay_flush%&.
27664 .cindex "&%endpass%& ACL modifier"
27665 This modifier, which has no argument, is recognized only in &%accept%& and
27666 &%discard%& statements. It marks the boundary between the conditions whose
27667 failure causes control to pass to the next statement, and the conditions whose
27668 failure causes the ACL to return &"deny"&. This concept has proved to be
27669 confusing to some people, so the use of &%endpass%& is no longer recommended as
27670 &"best practice"&. See the description of &%accept%& above for more details.
27673 .vitem &*log_message*&&~=&~<&'text'&>
27674 .cindex "&%log_message%& ACL modifier"
27675 This modifier sets up a message that is used as part of the log message if the
27676 ACL denies access or a &%warn%& statement's conditions are true. For example:
27678 require log_message = wrong cipher suite $tls_in_cipher
27679 encrypted = DES-CBC3-SHA
27681 &%log_message%& is also used when recipients are discarded by &%discard%&. For
27684 &`discard `&<&'some conditions'&>
27685 &` log_message = Discarded $local_part@$domain because...`&
27687 When access is denied, &%log_message%& adds to any underlying error message
27688 that may exist because of a condition failure. For example, while verifying a
27689 recipient address, a &':fail:'& redirection might have already set up a
27692 The message may be defined before the conditions to which it applies, because
27693 the string expansion does not happen until Exim decides that access is to be
27694 denied. This means that any variables that are set by the condition are
27695 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
27696 variables are set after a DNS black list lookup succeeds. If the expansion of
27697 &%log_message%& fails, or if the result is an empty string, the modifier is
27700 .vindex "&$acl_verify_message$&"
27701 If you want to use a &%warn%& statement to log the result of an address
27702 verification, you can use &$acl_verify_message$& to include the verification
27705 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
27706 the start of the logged message. If the same warning log message is requested
27707 more than once while receiving a single email message, only one copy is
27708 actually logged. If you want to log multiple copies, use &%logwrite%& instead
27709 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
27710 is logged for a successful &%warn%& statement.
27712 If &%log_message%& is not present and there is no underlying error message (for
27713 example, from the failure of address verification), but &%message%& is present,
27714 the &%message%& text is used for logging rejections. However, if any text for
27715 logging contains newlines, only the first line is logged. In the absence of
27716 both &%log_message%& and &%message%&, a default built-in message is used for
27717 logging rejections.
27720 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
27721 .cindex "&%log_reject_target%& ACL modifier"
27722 .cindex "logging in ACL" "specifying which log"
27723 This modifier makes it possible to specify which logs are used for messages
27724 about ACL rejections. Its argument is a colon-separated list of words that can
27725 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
27726 may be empty, in which case a rejection is not logged at all. For example, this
27727 ACL fragment writes no logging information when access is denied:
27729 &`deny `&<&'some conditions'&>
27730 &` log_reject_target =`&
27732 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
27733 permanent and temporary rejections. Its effect lasts for the rest of the
27737 .vitem &*logwrite*&&~=&~<&'text'&>
27738 .cindex "&%logwrite%& ACL modifier"
27739 .cindex "logging in ACL" "immediate"
27740 This modifier writes a message to a log file as soon as it is encountered when
27741 processing an ACL. (Compare &%log_message%&, which, except in the case of
27742 &%warn%& and &%discard%&, is used only if the ACL statement denies
27743 access.) The &%logwrite%& modifier can be used to log special incidents in
27746 &`accept `&<&'some special conditions'&>
27747 &` control = freeze`&
27748 &` logwrite = froze message because ...`&
27750 By default, the message is written to the main log. However, it may begin
27751 with a colon, followed by a comma-separated list of log names, and then
27752 another colon, to specify exactly which logs are to be written. For
27755 logwrite = :main,reject: text for main and reject logs
27756 logwrite = :panic: text for panic log only
27760 .vitem &*message*&&~=&~<&'text'&>
27761 .cindex "&%message%& ACL modifier"
27762 This modifier sets up a text string that is expanded and used as a response
27763 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
27764 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
27765 there is some complication if &%endpass%& is involved; see the description of
27766 &%accept%& for details.)
27768 The expansion of the message happens at the time Exim decides that the ACL is
27769 to end, not at the time it processes &%message%&. If the expansion fails, or
27770 generates an empty string, the modifier is ignored. Here is an example where
27771 &%message%& must be specified first, because the ACL ends with a rejection if
27772 the &%hosts%& condition fails:
27774 require message = Host not recognized
27777 (Once a condition has failed, no further conditions or modifiers are
27780 .cindex "SMTP" "error codes"
27781 .oindex "&%smtp_banner%&
27782 For ACLs that are triggered by SMTP commands, the message is returned as part
27783 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
27784 is meaningful only for SMTP, as no message is returned when a non-SMTP message
27785 is accepted. In the case of the connect ACL, accepting with a message modifier
27786 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
27787 accept message may not contain more than one line (otherwise it will be
27788 truncated at the first newline and a panic logged), and it cannot affect the
27791 When SMTP is involved, the message may begin with an overriding response code,
27792 consisting of three digits optionally followed by an &"extended response code"&
27793 of the form &'n.n.n'&, each code being followed by a space. For example:
27795 deny message = 599 1.2.3 Host not welcome
27796 hosts = 192.168.34.0/24
27798 The first digit of the supplied response code must be the same as would be sent
27799 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
27800 access, but for the predata ACL, note that the default success code is 354, not
27803 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
27804 the message modifier cannot override the 221 response code.
27806 The text in a &%message%& modifier is literal; any quotes are taken as
27807 literals, but because the string is expanded, backslash escapes are processed
27808 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
27811 .vindex "&$acl_verify_message$&"
27813 For ACLs that are called by an &%acl =%& ACL condition, the message is
27814 stored in &$acl_verify_message$&, from which the calling ACL may use it.
27817 If &%message%& is used on a statement that verifies an address, the message
27818 specified overrides any message that is generated by the verification process.
27819 However, the original message is available in the variable
27820 &$acl_verify_message$&, so you can incorporate it into your message if you
27821 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
27822 routers to be passed back as part of the SMTP response, you should either not
27823 use a &%message%& modifier, or make use of &$acl_verify_message$&.
27825 For compatibility with previous releases of Exim, a &%message%& modifier that
27826 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
27827 modifier, but this usage is now deprecated. However, &%message%& acts only when
27828 all the conditions are true, wherever it appears in an ACL command, whereas
27829 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
27830 &%warn%& in an ACL that is not concerned with receiving a message, it has no
27834 .vitem &*remove_header*&&~=&~<&'text'&>
27835 This modifier specifies one or more header names in a colon-separated list
27836 that are to be removed from an incoming message, assuming, of course, that
27837 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
27840 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
27841 .cindex "&%set%& ACL modifier"
27842 This modifier puts a value into one of the ACL variables (see section
27843 &<<SECTaclvariables>>&).
27846 .vitem &*udpsend*&&~=&~<&'parameters'&>
27847 This modifier sends a UDP packet, for purposes such as statistics
27848 collection or behaviour monitoring. The parameters are expanded, and
27849 the result of the expansion must be a colon-separated list consisting
27850 of a destination server, port number, and the packet contents. The
27851 server can be specified as a host name or IPv4 or IPv6 address. The
27852 separator can be changed with the usual angle bracket syntax. For
27853 example, you might want to collect information on which hosts connect
27856 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
27857 $tod_zulu $sender_host_address
27864 .section "Use of the control modifier" "SECTcontrols"
27865 .cindex "&%control%& ACL modifier"
27866 The &%control%& modifier supports the following settings:
27869 .vitem &*control&~=&~allow_auth_unadvertised*&
27870 This modifier allows a client host to use the SMTP AUTH command even when it
27871 has not been advertised in response to EHLO. Furthermore, because there are
27872 apparently some really broken clients that do this, Exim will accept AUTH after
27873 HELO (rather than EHLO) when this control is set. It should be used only if you
27874 really need it, and you should limit its use to those broken clients that do
27875 not work without it. For example:
27877 warn hosts = 192.168.34.25
27878 control = allow_auth_unadvertised
27880 Normally, when an Exim server receives an AUTH command, it checks the name of
27881 the authentication mechanism that is given in the command to ensure that it
27882 matches an advertised mechanism. When this control is set, the check that a
27883 mechanism has been advertised is bypassed. Any configured mechanism can be used
27884 by the client. This control is permitted only in the connection and HELO ACLs.
27887 .vitem &*control&~=&~caseful_local_part*& &&&
27888 &*control&~=&~caselower_local_part*&
27889 .cindex "&ACL;" "case of local part in"
27890 .cindex "case of local parts"
27891 .vindex "&$local_part$&"
27892 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
27893 (that is, during RCPT processing). By default, the contents of &$local_part$&
27894 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
27895 any uppercase letters in the original local part are restored in &$local_part$&
27896 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
27899 These controls affect only the current recipient. Moreover, they apply only to
27900 local part handling that takes place directly in the ACL (for example, as a key
27901 in lookups). If a test to verify the recipient is obeyed, the case-related
27902 handling of the local part during the verification is controlled by the router
27903 configuration (see the &%caseful_local_part%& generic router option).
27905 This facility could be used, for example, to add a spam score to local parts
27906 containing upper case letters. For example, using &$acl_m4$& to accumulate the
27909 warn control = caseful_local_part
27910 set acl_m4 = ${eval:\
27912 ${if match{$local_part}{[A-Z]}{1}{0}}\
27914 control = caselower_local_part
27916 Notice that we put back the lower cased version afterwards, assuming that
27917 is what is wanted for subsequent tests.
27920 .vitem &*control&~=&~cutthrough_delivery*&
27921 .cindex "&ACL;" "cutthrough routing"
27922 .cindex "cutthrough" "requesting"
27923 This option requests delivery be attempted while the item is being received.
27924 It is usable in the RCPT ACL and valid only for single-recipient mails forwarded
27925 from one SMTP connection to another. If a recipient-verify callout connection is
27926 requested in the same ACL it is held open and used for the data, otherwise one is made
27927 after the ACL completes.
27929 Note that routers are used in verify mode,
27930 and cannot depend on content of received headers.
27931 Note also that headers cannot be
27932 modified by any of the post-data ACLs (DATA, MIME and DKIM).
27933 Headers may be modified by routers (subject to the above) and transports.
27935 Cutthrough delivery is not supported via transport-filters or when DKIM signing
27936 of outgoing messages is done, because it sends data to the ultimate destination
27937 before the entire message has been received from the source.
27939 Should the ultimate destination system positively accept or reject the mail,
27940 a corresponding indication is given to the source system and nothing is queued.
27941 If there is a temporary error the item is queued for later delivery in the
27942 usual fashion. If the item is successfully delivered in cutthrough mode the log line
27943 is tagged with ">>" rather than "=>" and appears before the acceptance "<="
27946 Delivery in this mode avoids the generation of a bounce mail to a (possibly faked)
27947 sender when the destination system is doing content-scan based rejection.
27950 .vitem &*control&~=&~debug/*&<&'options'&>
27951 .cindex "&ACL;" "enabling debug logging"
27952 .cindex "debugging" "enabling from an ACL"
27953 This control turns on debug logging, almost as though Exim had been invoked
27954 with &`-d`&, with the output going to a new logfile, by default called
27955 &'debuglog'&. The filename can be adjusted with the &'tag'& option, which
27956 may access any variables already defined. The logging may be adjusted with
27957 the &'opts'& option, which takes the same values as the &`-d`& command-line
27958 option. Some examples (which depend on variables that don't exist in all
27962 control = debug/tag=.$sender_host_address
27963 control = debug/opts=+expand+acl
27964 control = debug/tag=.$message_exim_id/opts=+expand
27968 .vitem &*control&~=&~dkim_disable_verify*&
27969 .cindex "disable DKIM verify"
27970 .cindex "DKIM" "disable verify"
27971 This control turns off DKIM verification processing entirely. For details on
27972 the operation and configuration of DKIM, see chapter &<<CHAPdkim>>&.
27975 .vitem &*control&~=&~dscp/*&<&'value'&>
27976 .cindex "&ACL;" "setting DSCP value"
27977 .cindex "DSCP" "inbound"
27978 This option causes the DSCP value associated with the socket for the inbound
27979 connection to be adjusted to a given value, given as one of a number of fixed
27980 strings or to numeric value.
27981 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
27982 Common values include &`throughput`&, &`mincost`&, and on newer systems
27983 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
27985 The outbound packets from Exim will be marked with this value in the header
27986 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
27987 that these values will have any effect, not be stripped by networking
27988 equipment, or do much of anything without cooperation with your Network
27989 Engineer and those of all network operators between the source and destination.
27992 .vitem &*control&~=&~enforce_sync*& &&&
27993 &*control&~=&~no_enforce_sync*&
27994 .cindex "SMTP" "synchronization checking"
27995 .cindex "synchronization checking in SMTP"
27996 These controls make it possible to be selective about when SMTP synchronization
27997 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
27998 state of the switch (it is true by default). See the description of this option
27999 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
28001 The effect of these two controls lasts for the remainder of the SMTP
28002 connection. They can appear in any ACL except the one for the non-SMTP
28003 messages. The most straightforward place to put them is in the ACL defined by
28004 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
28005 before the first synchronization check. The expected use is to turn off the
28006 synchronization checks for badly-behaved hosts that you nevertheless need to
28010 .vitem &*control&~=&~fakedefer/*&<&'message'&>
28011 .cindex "fake defer"
28012 .cindex "defer, fake"
28013 This control works in exactly the same way as &%fakereject%& (described below)
28014 except that it causes an SMTP 450 response after the message data instead of a
28015 550 response. You must take care when using &%fakedefer%& because it causes the
28016 messages to be duplicated when the sender retries. Therefore, you should not
28017 use &%fakedefer%& if the message is to be delivered normally.
28019 .vitem &*control&~=&~fakereject/*&<&'message'&>
28020 .cindex "fake rejection"
28021 .cindex "rejection, fake"
28022 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
28023 words, only when an SMTP message is being received. If Exim accepts the
28024 message, instead the final 250 response, a 550 rejection message is sent.
28025 However, Exim proceeds to deliver the message as normal. The control applies
28026 only to the current message, not to any subsequent ones that may be received in
28027 the same SMTP connection.
28029 The text for the 550 response is taken from the &%control%& modifier. If no
28030 message is supplied, the following is used:
28032 550-Your message has been rejected but is being
28033 550-kept for evaluation.
28034 550-If it was a legitimate message, it may still be
28035 550 delivered to the target recipient(s).
28037 This facility should be used with extreme caution.
28039 .vitem &*control&~=&~freeze*&
28040 .cindex "frozen messages" "forcing in ACL"
28041 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
28042 other words, only when a message is being received. If the message is accepted,
28043 it is placed on Exim's queue and frozen. The control applies only to the
28044 current message, not to any subsequent ones that may be received in the same
28047 This modifier can optionally be followed by &`/no_tell`&. If the global option
28048 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
28049 is told about the freezing), provided all the &*control=freeze*& modifiers that
28050 are obeyed for the current message have the &`/no_tell`& option.
28052 .vitem &*control&~=&~no_delay_flush*&
28053 .cindex "SMTP" "output flushing, disabling for delay"
28054 Exim normally flushes SMTP output before implementing a delay in an ACL, to
28055 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
28056 use. This control, as long as it is encountered before the &%delay%& modifier,
28057 disables such output flushing.
28059 .vitem &*control&~=&~no_callout_flush*&
28060 .cindex "SMTP" "output flushing, disabling for callout"
28061 Exim normally flushes SMTP output before performing a callout in an ACL, to
28062 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
28063 use. This control, as long as it is encountered before the &%verify%& condition
28064 that causes the callout, disables such output flushing.
28066 .vitem &*control&~=&~no_mbox_unspool*&
28067 This control is available when Exim is compiled with the content scanning
28068 extension. Content scanning may require a copy of the current message, or parts
28069 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
28070 or spam scanner. Normally, such copies are deleted when they are no longer
28071 needed. If this control is set, the copies are not deleted. The control applies
28072 only to the current message, not to any subsequent ones that may be received in
28073 the same SMTP connection. It is provided for debugging purposes and is unlikely
28074 to be useful in production.
28076 .vitem &*control&~=&~no_multiline_responses*&
28077 .cindex "multiline responses, suppressing"
28078 This control is permitted for any ACL except the one for non-SMTP messages.
28079 It seems that there are broken clients in use that cannot handle multiline
28080 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
28082 If this control is set, multiline SMTP responses from ACL rejections are
28083 suppressed. One way of doing this would have been to put out these responses as
28084 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
28085 (&"use multiline responses for more"& it says &-- ha!), and some of the
28086 responses might get close to that. So this facility, which is after all only a
28087 sop to broken clients, is implemented by doing two very easy things:
28090 Extra information that is normally output as part of a rejection caused by
28091 sender verification failure is omitted. Only the final line (typically &"sender
28092 verification failed"&) is sent.
28094 If a &%message%& modifier supplies a multiline response, only the first
28098 The setting of the switch can, of course, be made conditional on the
28099 calling host. Its effect lasts until the end of the SMTP connection.
28101 .vitem &*control&~=&~no_pipelining*&
28102 .cindex "PIPELINING" "suppressing advertising"
28103 This control turns off the advertising of the PIPELINING extension to SMTP in
28104 the current session. To be useful, it must be obeyed before Exim sends its
28105 response to an EHLO command. Therefore, it should normally appear in an ACL
28106 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
28107 &%pipelining_advertise_hosts%&.
28109 .vitem &*control&~=&~queue_only*&
28110 .oindex "&%queue_only%&"
28111 .cindex "queueing incoming messages"
28112 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
28113 other words, only when a message is being received. If the message is accepted,
28114 it is placed on Exim's queue and left there for delivery by a subsequent queue
28115 runner. No immediate delivery process is started. In other words, it has the
28116 effect as the &%queue_only%& global option. However, the control applies only
28117 to the current message, not to any subsequent ones that may be received in the
28118 same SMTP connection.
28120 .vitem &*control&~=&~submission/*&<&'options'&>
28121 .cindex "message" "submission"
28122 .cindex "submission mode"
28123 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
28124 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
28125 the current message is a submission from a local MUA. In this case, Exim
28126 operates in &"submission mode"&, and applies certain fixups to the message if
28127 necessary. For example, it adds a &'Date:'& header line if one is not present.
28128 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
28129 late (the message has already been created).
28131 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
28132 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
28133 submission mode; the available options for this control are described there.
28134 The control applies only to the current message, not to any subsequent ones
28135 that may be received in the same SMTP connection.
28137 .vitem &*control&~=&~suppress_local_fixups*&
28138 .cindex "submission fixups, suppressing"
28139 This control applies to locally submitted (non TCP/IP) messages, and is the
28140 complement of &`control = submission`&. It disables the fixups that are
28141 normally applied to locally-submitted messages. Specifically:
28144 Any &'Sender:'& header line is left alone (in this respect, it is a
28145 dynamic version of &%local_sender_retain%&).
28147 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
28149 There is no check that &'From:'& corresponds to the actual sender.
28152 This control may be useful when a remotely-originated message is accepted,
28153 passed to some scanning program, and then re-submitted for delivery. It can be
28154 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
28155 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
28158 &*Note:*& This control applies only to the current message, not to any others
28159 that are being submitted at the same time using &%-bs%& or &%-bS%&.
28163 .section "Summary of message fixup control" "SECTsummesfix"
28164 All four possibilities for message fixups can be specified:
28167 Locally submitted, fixups applied: the default.
28169 Locally submitted, no fixups applied: use
28170 &`control = suppress_local_fixups`&.
28172 Remotely submitted, no fixups applied: the default.
28174 Remotely submitted, fixups applied: use &`control = submission`&.
28179 .section "Adding header lines in ACLs" "SECTaddheadacl"
28180 .cindex "header lines" "adding in an ACL"
28181 .cindex "header lines" "position of added lines"
28182 .cindex "&%add_header%& ACL modifier"
28183 The &%add_header%& modifier can be used to add one or more extra header lines
28184 to an incoming message, as in this example:
28186 warn dnslists = sbl.spamhaus.org : \
28187 dialup.mail-abuse.org
28188 add_header = X-blacklisted-at: $dnslist_domain
28190 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
28191 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
28192 receiving a message). The message must ultimately be accepted for
28193 &%add_header%& to have any significant effect. You can use &%add_header%& with
28194 any ACL verb, including &%deny%& (though this is potentially useful only in a
28197 Headers will not be added to the message if the modifier is used in
28198 DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing.
28200 Leading and trailing newlines are removed from
28201 the data for the &%add_header%& modifier; if it then
28202 contains one or more newlines that
28203 are not followed by a space or a tab, it is assumed to contain multiple header
28204 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
28205 front of any line that is not a valid header line.
28207 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
28208 They are added to the message before processing the DATA and MIME ACLs.
28209 However, if an identical header line is requested more than once, only one copy
28210 is actually added to the message. Further header lines may be accumulated
28211 during the DATA and MIME ACLs, after which they are added to the message, again
28212 with duplicates suppressed. Thus, it is possible to add two identical header
28213 lines to an SMTP message, but only if one is added before DATA and one after.
28214 In the case of non-SMTP messages, new headers are accumulated during the
28215 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
28216 message is rejected after DATA or by the non-SMTP ACL, all added header lines
28217 are included in the entry that is written to the reject log.
28219 .cindex "header lines" "added; visibility of"
28220 Header lines are not visible in string expansions
28222 until they are added to the
28223 message. It follows that header lines defined in the MAIL, RCPT, and predata
28224 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
28225 header lines that are added by the DATA or MIME ACLs are not visible in those
28226 ACLs. Because of this restriction, you cannot use header lines as a way of
28227 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
28228 this, you can use ACL variables, as described in section
28229 &<<SECTaclvariables>>&.
28231 The list of headers yet to be added is given by the &%$headers_added%& variable.
28233 The &%add_header%& modifier acts immediately as it is encountered during the
28234 processing of an ACL. Notice the difference between these two cases:
28236 &`accept add_header = ADDED: some text`&
28237 &` `&<&'some condition'&>
28239 &`accept `&<&'some condition'&>
28240 &` add_header = ADDED: some text`&
28242 In the first case, the header line is always added, whether or not the
28243 condition is true. In the second case, the header line is added only if the
28244 condition is true. Multiple occurrences of &%add_header%& may occur in the same
28245 ACL statement. All those that are encountered before a condition fails are
28248 .cindex "&%warn%& ACL verb"
28249 For compatibility with previous versions of Exim, a &%message%& modifier for a
28250 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
28251 effect only if all the conditions are true, even if it appears before some of
28252 them. Furthermore, only the last occurrence of &%message%& is honoured. This
28253 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
28254 are present on a &%warn%& verb, both are processed according to their
28257 By default, new header lines are added to a message at the end of the existing
28258 header lines. However, you can specify that any particular header line should
28259 be added right at the start (before all the &'Received:'& lines), immediately
28260 after the first block of &'Received:'& lines, or immediately before any line
28261 that is not a &'Received:'& or &'Resent-something:'& header.
28263 This is done by specifying &":at_start:"&, &":after_received:"&, or
28264 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
28265 header line, respectively. (Header text cannot start with a colon, as there has
28266 to be a header name first.) For example:
28268 warn add_header = \
28269 :after_received:X-My-Header: something or other...
28271 If more than one header line is supplied in a single &%add_header%& modifier,
28272 each one is treated independently and can therefore be placed differently. If
28273 you add more than one line at the start, or after the Received: block, they end
28274 up in reverse order.
28276 &*Warning*&: This facility currently applies only to header lines that are
28277 added in an ACL. It does NOT work for header lines that are added in a
28278 system filter or in a router or transport.
28282 .section "Removing header lines in ACLs" "SECTremoveheadacl"
28283 .cindex "header lines" "removing in an ACL"
28284 .cindex "header lines" "position of removed lines"
28285 .cindex "&%remove_header%& ACL modifier"
28286 The &%remove_header%& modifier can be used to remove one or more header lines
28287 from an incoming message, as in this example:
28289 warn message = Remove internal headers
28290 remove_header = x-route-mail1 : x-route-mail2
28292 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
28293 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
28294 receiving a message). The message must ultimately be accepted for
28295 &%remove_header%& to have any significant effect. You can use &%remove_header%&
28296 with any ACL verb, including &%deny%&, though this is really not useful for
28297 any verb that doesn't result in a delivered message.
28299 Headers will not be removed to the message if the modifier is used in
28300 DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing.
28302 More than one header can be removed at the same time by using a colon separated
28303 list of header names. The header matching is case insensitive. Wildcards are
28304 not permitted, nor is list expansion performed, so you cannot use hostlists to
28305 create a list of headers, however both connection and message variable expansion
28306 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
28308 warn hosts = +internal_hosts
28309 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
28310 warn message = Remove internal headers
28311 remove_header = $acl_c_ihdrs
28313 Removed header lines are accumulated during the MAIL, RCPT, and predata ACLs.
28314 They are removed from the message before processing the DATA and MIME ACLs.
28315 There is no harm in attempting to remove the same header twice nor is removing
28316 a non-existent header. Further header lines to be removed may be accumulated
28317 during the DATA and MIME ACLs, after which they are removed from the message,
28318 if present. In the case of non-SMTP messages, headers to be removed are
28319 accumulated during the non-SMTP ACLs, and are removed from the message after
28320 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
28321 ACL, there really is no effect because there is no logging of what headers
28322 would have been removed.
28324 .cindex "header lines" "removed; visibility of"
28325 Header lines are not visible in string expansions until the DATA phase when it
28326 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
28327 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
28328 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
28329 this restriction, you cannot use header lines as a way of controlling data
28330 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
28331 you should instead use ACL variables, as described in section
28332 &<<SECTaclvariables>>&.
28334 The &%remove_header%& modifier acts immediately as it is encountered during the
28335 processing of an ACL. Notice the difference between these two cases:
28337 &`accept remove_header = X-Internal`&
28338 &` `&<&'some condition'&>
28340 &`accept `&<&'some condition'&>
28341 &` remove_header = X-Internal`&
28343 In the first case, the header line is always removed, whether or not the
28344 condition is true. In the second case, the header line is removed only if the
28345 condition is true. Multiple occurrences of &%remove_header%& may occur in the
28346 same ACL statement. All those that are encountered before a condition fails
28349 &*Warning*&: This facility currently applies only to header lines that are
28350 present during ACL processing. It does NOT remove header lines that are added
28351 in a system filter or in a router or transport.
28356 .section "ACL conditions" "SECTaclconditions"
28357 .cindex "&ACL;" "conditions; list of"
28358 Some of the conditions listed in this section are available only when Exim is
28359 compiled with the content-scanning extension. They are included here briefly
28360 for completeness. More detailed descriptions can be found in the discussion on
28361 content scanning in chapter &<<CHAPexiscan>>&.
28363 Not all conditions are relevant in all circumstances. For example, testing
28364 senders and recipients does not make sense in an ACL that is being run as the
28365 result of the arrival of an ETRN command, and checks on message headers can be
28366 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
28367 can use the same condition (with different parameters) more than once in the
28368 same ACL statement. This provides a way of specifying an &"and"& conjunction.
28369 The conditions are as follows:
28373 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
28374 .cindex "&ACL;" "nested"
28375 .cindex "&ACL;" "indirect"
28376 .cindex "&ACL;" "arguments"
28377 .cindex "&%acl%& ACL condition"
28378 The possible values of the argument are the same as for the
28379 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
28380 &"accept"& the condition is true; if it returns &"deny"& the condition is
28381 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
28382 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
28383 condition false. This means that further processing of the &%warn%& verb
28384 ceases, but processing of the ACL continues.
28386 If the argument is a named ACL, up to nine space-separated optional values
28387 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
28388 and $acl_narg is set to the count of values.
28389 Previous values of these variables are restored after the call returns.
28390 The name and values are expanded separately.
28391 Note that spaces in complex expansions which are used as arguments
28392 will act as argument separators.
28394 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
28395 the connection is dropped. If it returns &"discard"&, the verb must be
28396 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
28397 conditions are tested.
28399 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
28400 loops. This condition allows you to use different ACLs in different
28401 circumstances. For example, different ACLs can be used to handle RCPT commands
28402 for different local users or different local domains.
28404 .vitem &*authenticated&~=&~*&<&'string&~list'&>
28405 .cindex "&%authenticated%& ACL condition"
28406 .cindex "authentication" "ACL checking"
28407 .cindex "&ACL;" "testing for authentication"
28408 If the SMTP connection is not authenticated, the condition is false. Otherwise,
28409 the name of the authenticator is tested against the list. To test for
28410 authentication by any authenticator, you can set
28415 .vitem &*condition&~=&~*&<&'string'&>
28416 .cindex "&%condition%& ACL condition"
28417 .cindex "customizing" "ACL condition"
28418 .cindex "&ACL;" "customized test"
28419 .cindex "&ACL;" "testing, customized"
28420 This feature allows you to make up custom conditions. If the result of
28421 expanding the string is an empty string, the number zero, or one of the strings
28422 &"no"& or &"false"&, the condition is false. If the result is any non-zero
28423 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
28424 any other value, some error is assumed to have occurred, and the ACL returns
28425 &"defer"&. However, if the expansion is forced to fail, the condition is
28426 ignored. The effect is to treat it as true, whether it is positive or
28429 .vitem &*decode&~=&~*&<&'location'&>
28430 .cindex "&%decode%& ACL condition"
28431 This condition is available only when Exim is compiled with the
28432 content-scanning extension, and it is allowed only in the ACL defined by
28433 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
28434 If all goes well, the condition is true. It is false only if there are
28435 problems such as a syntax error or a memory shortage. For more details, see
28436 chapter &<<CHAPexiscan>>&.
28438 .vitem &*demime&~=&~*&<&'extension&~list'&>
28439 .cindex "&%demime%& ACL condition"
28440 This condition is available only when Exim is compiled with the
28441 content-scanning extension. Its use is described in section
28442 &<<SECTdemimecond>>&.
28444 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
28445 .cindex "&%dnslists%& ACL condition"
28446 .cindex "DNS list" "in ACL"
28447 .cindex "black list (DNS)"
28448 .cindex "&ACL;" "testing a DNS list"
28449 This condition checks for entries in DNS black lists. These are also known as
28450 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
28451 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
28452 different variants of this condition to describe briefly here. See sections
28453 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
28455 .vitem &*domains&~=&~*&<&'domain&~list'&>
28456 .cindex "&%domains%& ACL condition"
28457 .cindex "domain" "ACL checking"
28458 .cindex "&ACL;" "testing a recipient domain"
28459 .vindex "&$domain_data$&"
28460 This condition is relevant only after a RCPT command. It checks that the domain
28461 of the recipient address is in the domain list. If percent-hack processing is
28462 enabled, it is done before this test is done. If the check succeeds with a
28463 lookup, the result of the lookup is placed in &$domain_data$& until the next
28466 &*Note carefully*& (because many people seem to fall foul of this): you cannot
28467 use &%domains%& in a DATA ACL.
28470 .vitem &*encrypted&~=&~*&<&'string&~list'&>
28471 .cindex "&%encrypted%& ACL condition"
28472 .cindex "encryption" "checking in an ACL"
28473 .cindex "&ACL;" "testing for encryption"
28474 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
28475 name of the cipher suite in use is tested against the list. To test for
28476 encryption without testing for any specific cipher suite(s), set
28482 .vitem &*hosts&~=&~*&<&'host&~list'&>
28483 .cindex "&%hosts%& ACL condition"
28484 .cindex "host" "ACL checking"
28485 .cindex "&ACL;" "testing the client host"
28486 This condition tests that the calling host matches the host list. If you have
28487 name lookups or wildcarded host names and IP addresses in the same host list,
28488 you should normally put the IP addresses first. For example, you could have:
28490 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
28492 The lookup in this example uses the host name for its key. This is implied by
28493 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
28494 and it wouldn't matter which way round you had these two items.)
28496 The reason for the problem with host names lies in the left-to-right way that
28497 Exim processes lists. It can test IP addresses without doing any DNS lookups,
28498 but when it reaches an item that requires a host name, it fails if it cannot
28499 find a host name to compare with the pattern. If the above list is given in the
28500 opposite order, the &%accept%& statement fails for a host whose name cannot be
28501 found, even if its IP address is 10.9.8.7.
28503 If you really do want to do the name check first, and still recognize the IP
28504 address even if the name lookup fails, you can rewrite the ACL like this:
28506 accept hosts = dbm;/etc/friendly/hosts
28507 accept hosts = 10.9.8.7
28509 The default action on failing to find the host name is to assume that the host
28510 is not in the list, so the first &%accept%& statement fails. The second
28511 statement can then check the IP address.
28513 .vindex "&$host_data$&"
28514 If a &%hosts%& condition is satisfied by means of a lookup, the result
28515 of the lookup is made available in the &$host_data$& variable. This
28516 allows you, for example, to set up a statement like this:
28518 deny hosts = net-lsearch;/some/file
28519 message = $host_data
28521 which gives a custom error message for each denied host.
28523 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
28524 .cindex "&%local_parts%& ACL condition"
28525 .cindex "local part" "ACL checking"
28526 .cindex "&ACL;" "testing a local part"
28527 .vindex "&$local_part_data$&"
28528 This condition is relevant only after a RCPT command. It checks that the local
28529 part of the recipient address is in the list. If percent-hack processing is
28530 enabled, it is done before this test. If the check succeeds with a lookup, the
28531 result of the lookup is placed in &$local_part_data$&, which remains set until
28532 the next &%local_parts%& test.
28534 .vitem &*malware&~=&~*&<&'option'&>
28535 .cindex "&%malware%& ACL condition"
28536 .cindex "&ACL;" "virus scanning"
28537 .cindex "&ACL;" "scanning for viruses"
28538 This condition is available only when Exim is compiled with the
28539 content-scanning extension. It causes the incoming message to be scanned for
28540 viruses. For details, see chapter &<<CHAPexiscan>>&.
28542 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
28543 .cindex "&%mime_regex%& ACL condition"
28544 .cindex "&ACL;" "testing by regex matching"
28545 This condition is available only when Exim is compiled with the
28546 content-scanning extension, and it is allowed only in the ACL defined by
28547 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
28548 with any of the regular expressions. For details, see chapter
28551 .vitem &*ratelimit&~=&~*&<&'parameters'&>
28552 .cindex "rate limiting"
28553 This condition can be used to limit the rate at which a user or host submits
28554 messages. Details are given in section &<<SECTratelimiting>>&.
28556 .vitem &*recipients&~=&~*&<&'address&~list'&>
28557 .cindex "&%recipients%& ACL condition"
28558 .cindex "recipient" "ACL checking"
28559 .cindex "&ACL;" "testing a recipient"
28560 This condition is relevant only after a RCPT command. It checks the entire
28561 recipient address against a list of recipients.
28563 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
28564 .cindex "&%regex%& ACL condition"
28565 .cindex "&ACL;" "testing by regex matching"
28566 This condition is available only when Exim is compiled with the
28567 content-scanning extension, and is available only in the DATA, MIME, and
28568 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
28569 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
28571 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
28572 .cindex "&%sender_domains%& ACL condition"
28573 .cindex "sender" "ACL checking"
28574 .cindex "&ACL;" "testing a sender domain"
28575 .vindex "&$domain$&"
28576 .vindex "&$sender_address_domain$&"
28577 This condition tests the domain of the sender of the message against the given
28578 domain list. &*Note*&: The domain of the sender address is in
28579 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
28580 of this condition. This is an exception to the general rule for testing domain
28581 lists. It is done this way so that, if this condition is used in an ACL for a
28582 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
28583 influence the sender checking.
28585 &*Warning*&: It is a bad idea to use this condition on its own as a control on
28586 relaying, because sender addresses are easily, and commonly, forged.
28588 .vitem &*senders&~=&~*&<&'address&~list'&>
28589 .cindex "&%senders%& ACL condition"
28590 .cindex "sender" "ACL checking"
28591 .cindex "&ACL;" "testing a sender"
28592 This condition tests the sender of the message against the given list. To test
28593 for a bounce message, which has an empty sender, set
28597 &*Warning*&: It is a bad idea to use this condition on its own as a control on
28598 relaying, because sender addresses are easily, and commonly, forged.
28600 .vitem &*spam&~=&~*&<&'username'&>
28601 .cindex "&%spam%& ACL condition"
28602 .cindex "&ACL;" "scanning for spam"
28603 This condition is available only when Exim is compiled with the
28604 content-scanning extension. It causes the incoming message to be scanned by
28605 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
28607 .vitem &*verify&~=&~certificate*&
28608 .cindex "&%verify%& ACL condition"
28609 .cindex "TLS" "client certificate verification"
28610 .cindex "certificate" "verification of client"
28611 .cindex "&ACL;" "certificate verification"
28612 .cindex "&ACL;" "testing a TLS certificate"
28613 This condition is true in an SMTP session if the session is encrypted, and a
28614 certificate was received from the client, and the certificate was verified. The
28615 server requests a certificate only if the client matches &%tls_verify_hosts%&
28616 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
28618 .vitem &*verify&~=&~csa*&
28619 .cindex "CSA verification"
28620 This condition checks whether the sending host (the client) is authorized to
28621 send email. Details of how this works are given in section
28622 &<<SECTverifyCSA>>&.
28624 .vitem &*verify&~=&~header_names_ascii*&
28625 .cindex "&%verify%& ACL condition"
28626 .cindex "&ACL;" "verifying header names only ASCII"
28627 .cindex "header lines" "verifying header names only ASCII"
28628 .cindex "verifying" "header names only ASCII"
28629 This condition is relevant only in an ACL that is run after a message has been
28630 received, that is, in an ACL specified by &%acl_smtp_data%& or
28631 &%acl_not_smtp%&. It checks all header names (not the content) to make sure
28632 there are no non-ASCII characters, also excluding control characters. The
28633 allowable characters are decimal ASCII values 33 through 126.
28635 Exim itself will handle headers with non-ASCII characters, but it can cause
28636 problems for downstream applications, so this option will allow their
28637 detection and rejection in the DATA ACL's.
28639 .vitem &*verify&~=&~header_sender/*&<&'options'&>
28640 .cindex "&%verify%& ACL condition"
28641 .cindex "&ACL;" "verifying sender in the header"
28642 .cindex "header lines" "verifying the sender in"
28643 .cindex "sender" "verifying in header"
28644 .cindex "verifying" "sender in header"
28645 This condition is relevant only in an ACL that is run after a message has been
28646 received, that is, in an ACL specified by &%acl_smtp_data%& or
28647 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
28648 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
28649 is loosely thought of as a &"sender"& address (hence the name of the test).
28650 However, an address that appears in one of these headers need not be an address
28651 that accepts bounce messages; only sender addresses in envelopes are required
28652 to accept bounces. Therefore, if you use the callout option on this check, you
28653 might want to arrange for a non-empty address in the MAIL command.
28655 Details of address verification and the options are given later, starting at
28656 section &<<SECTaddressverification>>& (callouts are described in section
28657 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
28658 condition to restrict it to bounce messages only:
28661 message = A valid sender header is required for bounces
28662 !verify = header_sender
28665 .vitem &*verify&~=&~header_syntax*&
28666 .cindex "&%verify%& ACL condition"
28667 .cindex "&ACL;" "verifying header syntax"
28668 .cindex "header lines" "verifying syntax"
28669 .cindex "verifying" "header syntax"
28670 This condition is relevant only in an ACL that is run after a message has been
28671 received, that is, in an ACL specified by &%acl_smtp_data%& or
28672 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
28673 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
28674 and &'Bcc:'&). Unqualified addresses (local parts without domains) are
28675 permitted only in locally generated messages and from hosts that match
28676 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
28679 Note that this condition is a syntax check only. However, a common spamming
28680 ploy used to be to send syntactically invalid headers such as
28684 and this condition can be used to reject such messages, though they are not as
28685 common as they used to be.
28687 .vitem &*verify&~=&~helo*&
28688 .cindex "&%verify%& ACL condition"
28689 .cindex "&ACL;" "verifying HELO/EHLO"
28690 .cindex "HELO" "verifying"
28691 .cindex "EHLO" "verifying"
28692 .cindex "verifying" "EHLO"
28693 .cindex "verifying" "HELO"
28694 This condition is true if a HELO or EHLO command has been received from the
28695 client host, and its contents have been verified. If there has been no previous
28696 attempt to verify the HELO/EHLO contents, it is carried out when this
28697 condition is encountered. See the description of the &%helo_verify_hosts%& and
28698 &%helo_try_verify_hosts%& options for details of how to request verification
28699 independently of this condition.
28701 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
28702 option), this condition is always true.
28705 .vitem &*verify&~=&~not_blind*&
28706 .cindex "verifying" "not blind"
28707 .cindex "bcc recipients, verifying none"
28708 This condition checks that there are no blind (bcc) recipients in the message.
28709 Every envelope recipient must appear either in a &'To:'& header line or in a
28710 &'Cc:'& header line for this condition to be true. Local parts are checked
28711 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
28712 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
28713 used only in a DATA or non-SMTP ACL.
28715 There are, of course, many legitimate messages that make use of blind (bcc)
28716 recipients. This check should not be used on its own for blocking messages.
28719 .vitem &*verify&~=&~recipient/*&<&'options'&>
28720 .cindex "&%verify%& ACL condition"
28721 .cindex "&ACL;" "verifying recipient"
28722 .cindex "recipient" "verifying"
28723 .cindex "verifying" "recipient"
28724 .vindex "&$address_data$&"
28725 This condition is relevant only after a RCPT command. It verifies the current
28726 recipient. Details of address verification are given later, starting at section
28727 &<<SECTaddressverification>>&. After a recipient has been verified, the value
28728 of &$address_data$& is the last value that was set while routing the address.
28729 This applies even if the verification fails. When an address that is being
28730 verified is redirected to a single address, verification continues with the new
28731 address, and in that case, the subsequent value of &$address_data$& is the
28732 value for the child address.
28734 .vitem &*verify&~=&~reverse_host_lookup*&
28735 .cindex "&%verify%& ACL condition"
28736 .cindex "&ACL;" "verifying host reverse lookup"
28737 .cindex "host" "verifying reverse lookup"
28738 This condition ensures that a verified host name has been looked up from the IP
28739 address of the client host. (This may have happened already if the host name
28740 was needed for checking a host list, or if the host matched &%host_lookup%&.)
28741 Verification ensures that the host name obtained from a reverse DNS lookup, or
28742 one of its aliases, does, when it is itself looked up in the DNS, yield the
28743 original IP address.
28745 If this condition is used for a locally generated message (that is, when there
28746 is no client host involved), it always succeeds.
28748 .vitem &*verify&~=&~sender/*&<&'options'&>
28749 .cindex "&%verify%& ACL condition"
28750 .cindex "&ACL;" "verifying sender"
28751 .cindex "sender" "verifying"
28752 .cindex "verifying" "sender"
28753 This condition is relevant only after a MAIL or RCPT command, or after a
28754 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
28755 the message's sender is empty (that is, this is a bounce message), the
28756 condition is true. Otherwise, the sender address is verified.
28758 .vindex "&$address_data$&"
28759 .vindex "&$sender_address_data$&"
28760 If there is data in the &$address_data$& variable at the end of routing, its
28761 value is placed in &$sender_address_data$& at the end of verification. This
28762 value can be used in subsequent conditions and modifiers in the same ACL
28763 statement. It does not persist after the end of the current statement. If you
28764 want to preserve the value for longer, you can save it in an ACL variable.
28766 Details of verification are given later, starting at section
28767 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
28768 to avoid doing it more than once per message.
28770 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
28771 .cindex "&%verify%& ACL condition"
28772 This is a variation of the previous option, in which a modified address is
28773 verified as a sender.
28778 .section "Using DNS lists" "SECTmorednslists"
28779 .cindex "DNS list" "in ACL"
28780 .cindex "black list (DNS)"
28781 .cindex "&ACL;" "testing a DNS list"
28782 In its simplest form, the &%dnslists%& condition tests whether the calling host
28783 is on at least one of a number of DNS lists by looking up the inverted IP
28784 address in one or more DNS domains. (Note that DNS list domains are not mail
28785 domains, so the &`+`& syntax for named lists doesn't work - it is used for
28786 special options instead.) For example, if the calling host's IP
28787 address is 192.168.62.43, and the ACL statement is
28789 deny dnslists = blackholes.mail-abuse.org : \
28790 dialups.mail-abuse.org
28792 the following records are looked up:
28794 43.62.168.192.blackholes.mail-abuse.org
28795 43.62.168.192.dialups.mail-abuse.org
28797 As soon as Exim finds an existing DNS record, processing of the list stops.
28798 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
28799 to test that a host is on more than one list (an &"and"& conjunction), you can
28800 use two separate conditions:
28802 deny dnslists = blackholes.mail-abuse.org
28803 dnslists = dialups.mail-abuse.org
28805 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
28806 behaves as if the host does not match the list item, that is, as if the DNS
28807 record does not exist. If there are further items in the DNS list, they are
28810 This is usually the required action when &%dnslists%& is used with &%deny%&
28811 (which is the most common usage), because it prevents a DNS failure from
28812 blocking mail. However, you can change this behaviour by putting one of the
28813 following special items in the list:
28815 &`+include_unknown `& behave as if the item is on the list
28816 &`+exclude_unknown `& behave as if the item is not on the list (default)
28817 &`+defer_unknown `& give a temporary error
28819 .cindex "&`+include_unknown`&"
28820 .cindex "&`+exclude_unknown`&"
28821 .cindex "&`+defer_unknown`&"
28822 Each of these applies to any subsequent items on the list. For example:
28824 deny dnslists = +defer_unknown : foo.bar.example
28826 Testing the list of domains stops as soon as a match is found. If you want to
28827 warn for one list and block for another, you can use two different statements:
28829 deny dnslists = blackholes.mail-abuse.org
28830 warn message = X-Warn: sending host is on dialups list
28831 dnslists = dialups.mail-abuse.org
28833 DNS list lookups are cached by Exim for the duration of the SMTP session,
28834 so a lookup based on the IP address is done at most once for any incoming
28835 connection. Exim does not share information between multiple incoming
28836 connections (but your local name server cache should be active).
28840 .section "Specifying the IP address for a DNS list lookup" "SECID201"
28841 .cindex "DNS list" "keyed by explicit IP address"
28842 By default, the IP address that is used in a DNS list lookup is the IP address
28843 of the calling host. However, you can specify another IP address by listing it
28844 after the domain name, introduced by a slash. For example:
28846 deny dnslists = black.list.tld/192.168.1.2
28848 This feature is not very helpful with explicit IP addresses; it is intended for
28849 use with IP addresses that are looked up, for example, the IP addresses of the
28850 MX hosts or nameservers of an email sender address. For an example, see section
28851 &<<SECTmulkeyfor>>& below.
28856 .section "DNS lists keyed on domain names" "SECID202"
28857 .cindex "DNS list" "keyed by domain name"
28858 There are some lists that are keyed on domain names rather than inverted IP
28859 addresses (see for example the &'domain based zones'& link at
28860 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
28861 with these lists. You can change the name that is looked up in a DNS list by
28862 listing it after the domain name, introduced by a slash. For example,
28864 deny message = Sender's domain is listed at $dnslist_domain
28865 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
28867 This particular example is useful only in ACLs that are obeyed after the
28868 RCPT or DATA commands, when a sender address is available. If (for
28869 example) the message's sender is &'user@tld.example'& the name that is looked
28870 up by this example is
28872 tld.example.dsn.rfc-ignorant.org
28874 A single &%dnslists%& condition can contain entries for both names and IP
28875 addresses. For example:
28877 deny dnslists = sbl.spamhaus.org : \
28878 dsn.rfc-ignorant.org/$sender_address_domain
28880 The first item checks the sending host's IP address; the second checks a domain
28881 name. The whole condition is true if either of the DNS lookups succeeds.
28886 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
28887 .cindex "DNS list" "multiple keys for"
28888 The syntax described above for looking up explicitly-defined values (either
28889 names or IP addresses) in a DNS blacklist is a simplification. After the domain
28890 name for the DNS list, what follows the slash can in fact be a list of items.
28891 As with all lists in Exim, the default separator is a colon. However, because
28892 this is a sublist within the list of DNS blacklist domains, it is necessary
28893 either to double the separators like this:
28895 dnslists = black.list.tld/name.1::name.2
28897 or to change the separator character, like this:
28899 dnslists = black.list.tld/<;name.1;name.2
28901 If an item in the list is an IP address, it is inverted before the DNS
28902 blacklist domain is appended. If it is not an IP address, no inversion
28903 occurs. Consider this condition:
28905 dnslists = black.list.tld/<;192.168.1.2;a.domain
28907 The DNS lookups that occur are:
28909 2.1.168.192.black.list.tld
28910 a.domain.black.list.tld
28912 Once a DNS record has been found (that matches a specific IP return
28913 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
28914 are done. If there is a temporary DNS error, the rest of the sublist of domains
28915 or IP addresses is tried. A temporary error for the whole dnslists item occurs
28916 only if no other DNS lookup in this sublist succeeds. In other words, a
28917 successful lookup for any of the items in the sublist overrides a temporary
28918 error for a previous item.
28920 The ability to supply a list of items after the slash is in some sense just a
28921 syntactic convenience. These two examples have the same effect:
28923 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
28924 dnslists = black.list.tld/a.domain::b.domain
28926 However, when the data for the list is obtained from a lookup, the second form
28927 is usually much more convenient. Consider this example:
28929 deny message = The mail servers for the domain \
28930 $sender_address_domain \
28931 are listed at $dnslist_domain ($dnslist_value); \
28933 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
28934 ${lookup dnsdb {>|mxh=\
28935 $sender_address_domain} }} }
28937 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
28938 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
28939 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
28940 of expanding the condition might be something like this:
28942 dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|...
28944 Thus, this example checks whether or not the IP addresses of the sender
28945 domain's mail servers are on the Spamhaus black list.
28947 The key that was used for a successful DNS list lookup is put into the variable
28948 &$dnslist_matched$& (see section &<<SECID204>>&).
28953 .section "Data returned by DNS lists" "SECID203"
28954 .cindex "DNS list" "data returned from"
28955 DNS lists are constructed using address records in the DNS. The original RBL
28956 just used the address 127.0.0.1 on the right hand side of each record, but the
28957 RBL+ list and some other lists use a number of values with different meanings.
28958 The values used on the RBL+ list are:
28962 127.1.0.3 DUL and RBL
28964 127.1.0.5 RSS and RBL
28965 127.1.0.6 RSS and DUL
28966 127.1.0.7 RSS and DUL and RBL
28968 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
28969 different values. Some DNS lists may return more than one address record;
28970 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
28973 .section "Variables set from DNS lists" "SECID204"
28974 .cindex "expansion" "variables, set from DNS list"
28975 .cindex "DNS list" "variables set from"
28976 .vindex "&$dnslist_domain$&"
28977 .vindex "&$dnslist_matched$&"
28978 .vindex "&$dnslist_text$&"
28979 .vindex "&$dnslist_value$&"
28980 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
28981 the name of the overall domain that matched (for example,
28982 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
28983 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
28984 the DNS record. When the key is an IP address, it is not reversed in
28985 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
28986 cases, for example:
28988 deny dnslists = spamhaus.example
28990 the key is also available in another variable (in this case,
28991 &$sender_host_address$&). In more complicated cases, however, this is not true.
28992 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
28993 might generate a dnslists lookup like this:
28995 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
28997 If this condition succeeds, the value in &$dnslist_matched$& might be
28998 &`192.168.6.7`& (for example).
29000 If more than one address record is returned by the DNS lookup, all the IP
29001 addresses are included in &$dnslist_value$&, separated by commas and spaces.
29002 The variable &$dnslist_text$& contains the contents of any associated TXT
29003 record. For lists such as RBL+ the TXT record for a merged entry is often not
29004 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
29007 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
29008 &-- although these appear before the condition in the ACL, they are not
29009 expanded until after it has failed. For example:
29011 deny hosts = !+local_networks
29012 message = $sender_host_address is listed \
29014 dnslists = rbl-plus.mail-abuse.example
29019 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
29020 .cindex "DNS list" "matching specific returned data"
29021 You can add an equals sign and an IP address after a &%dnslists%& domain name
29022 in order to restrict its action to DNS records with a matching right hand side.
29025 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
29027 rejects only those hosts that yield 127.0.0.2. Without this additional data,
29028 any address record is considered to be a match. For the moment, we assume
29029 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
29030 describes how multiple records are handled.
29032 More than one IP address may be given for checking, using a comma as a
29033 separator. These are alternatives &-- if any one of them matches, the
29034 &%dnslists%& condition is true. For example:
29036 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
29038 If you want to specify a constraining address list and also specify names or IP
29039 addresses to be looked up, the constraining address list must be specified
29040 first. For example:
29042 deny dnslists = dsn.rfc-ignorant.org\
29043 =127.0.0.2/$sender_address_domain
29046 If the character &`&&`& is used instead of &`=`&, the comparison for each
29047 listed IP address is done by a bitwise &"and"& instead of by an equality test.
29048 In other words, the listed addresses are used as bit masks. The comparison is
29049 true if all the bits in the mask are present in the address that is being
29050 tested. For example:
29052 dnslists = a.b.c&0.0.0.3
29054 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
29055 want to test whether one bit or another bit is present (as opposed to both
29056 being present), you must use multiple values. For example:
29058 dnslists = a.b.c&0.0.0.1,0.0.0.2
29060 matches if the final component of the address is an odd number or two times
29065 .section "Negated DNS matching conditions" "SECID205"
29066 You can supply a negative list of IP addresses as part of a &%dnslists%&
29069 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
29071 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
29072 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
29074 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
29076 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
29077 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
29078 words, the result of the test is inverted if an exclamation mark appears before
29079 the &`=`& (or the &`&&`&) sign.
29081 &*Note*&: This kind of negation is not the same as negation in a domain,
29082 host, or address list (which is why the syntax is different).
29084 If you are using just one list, the negation syntax does not gain you much. The
29085 previous example is precisely equivalent to
29087 deny dnslists = a.b.c
29088 !dnslists = a.b.c=127.0.0.2,127.0.0.3
29090 However, if you are using multiple lists, the negation syntax is clearer.
29091 Consider this example:
29093 deny dnslists = sbl.spamhaus.org : \
29095 dnsbl.njabl.org!=127.0.0.3 : \
29098 Using only positive lists, this would have to be:
29100 deny dnslists = sbl.spamhaus.org : \
29102 deny dnslists = dnsbl.njabl.org
29103 !dnslists = dnsbl.njabl.org=127.0.0.3
29104 deny dnslists = relays.ordb.org
29106 which is less clear, and harder to maintain.
29111 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
29112 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
29113 thereby providing more than one IP address. When an item in a &%dnslists%& list
29114 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
29115 the match to specific results from the DNS lookup, there are two ways in which
29116 the checking can be handled. For example, consider the condition:
29118 dnslists = a.b.c=127.0.0.1
29120 What happens if the DNS lookup for the incoming IP address yields both
29121 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
29122 condition true because at least one given value was found, or is it false
29123 because at least one of the found values was not listed? And how does this
29124 affect negated conditions? Both possibilities are provided for with the help of
29125 additional separators &`==`& and &`=&&`&.
29128 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
29129 IP addresses matches one of the listed addresses. For the example above, the
29130 condition is true because 127.0.0.1 matches.
29132 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
29133 looked up IP addresses matches one of the listed addresses. If the condition is
29136 dnslists = a.b.c==127.0.0.1
29138 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
29139 false because 127.0.0.2 is not listed. You would need to have:
29141 dnslists = a.b.c==127.0.0.1,127.0.0.2
29143 for the condition to be true.
29146 When &`!`& is used to negate IP address matching, it inverts the result, giving
29147 the precise opposite of the behaviour above. Thus:
29149 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
29150 addresses matches one of the listed addresses. Consider:
29152 dnslists = a.b.c!&0.0.0.1
29154 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
29155 false because 127.0.0.1 matches.
29157 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
29158 looked up IP address that does not match. Consider:
29160 dnslists = a.b.c!=&0.0.0.1
29162 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
29163 true, because 127.0.0.2 does not match. You would need to have:
29165 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
29167 for the condition to be false.
29169 When the DNS lookup yields only a single IP address, there is no difference
29170 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
29175 .section "Detailed information from merged DNS lists" "SECTmordetinf"
29176 .cindex "DNS list" "information from merged"
29177 When the facility for restricting the matching IP values in a DNS list is used,
29178 the text from the TXT record that is set in &$dnslist_text$& may not reflect
29179 the true reason for rejection. This happens when lists are merged and the IP
29180 address in the A record is used to distinguish them; unfortunately there is
29181 only one TXT record. One way round this is not to use merged lists, but that
29182 can be inefficient because it requires multiple DNS lookups where one would do
29183 in the vast majority of cases when the host of interest is not on any of the
29186 A less inefficient way of solving this problem is available. If
29187 two domain names, comma-separated, are given, the second is used first to
29188 do an initial check, making use of any IP value restrictions that are set.
29189 If there is a match, the first domain is used, without any IP value
29190 restrictions, to get the TXT record. As a byproduct of this, there is also
29191 a check that the IP being tested is indeed on the first list. The first
29192 domain is the one that is put in &$dnslist_domain$&. For example:
29195 rejected because $sender_host_address is blacklisted \
29196 at $dnslist_domain\n$dnslist_text
29198 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
29199 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
29201 For the first blacklist item, this starts by doing a lookup in
29202 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
29203 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
29204 value, and as long as something is found, it looks for the corresponding TXT
29205 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
29206 The second blacklist item is processed similarly.
29208 If you are interested in more than one merged list, the same list must be
29209 given several times, but because the results of the DNS lookups are cached,
29210 the DNS calls themselves are not repeated. For example:
29212 reject dnslists = \
29213 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
29214 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
29215 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
29216 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
29218 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
29219 values matches (or if no record is found), this is the only lookup that is
29220 done. Only if there is a match is one of the more specific lists consulted.
29224 .section "DNS lists and IPv6" "SECTmorednslistslast"
29225 .cindex "IPv6" "DNS black lists"
29226 .cindex "DNS list" "IPv6 usage"
29227 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
29228 nibble by nibble. For example, if the calling host's IP address is
29229 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
29231 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
29232 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
29234 (split over two lines here to fit on the page). Unfortunately, some of the DNS
29235 lists contain wildcard records, intended for IPv4, that interact badly with
29236 IPv6. For example, the DNS entry
29238 *.3.some.list.example. A 127.0.0.1
29240 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
29241 Unfortunately, it also matches the entire 3::/4 IPv6 network.
29243 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
29244 &%condition%& condition, as in this example:
29246 deny condition = ${if isip4{$sender_host_address}}
29247 dnslists = some.list.example
29250 If an explicit key is being used for a DNS lookup and it may be an IPv6
29251 address you should specify alternate list separators for both the outer
29252 (DNS list name) list and inner (lookup keys) list:
29254 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
29257 .section "Rate limiting incoming messages" "SECTratelimiting"
29258 .cindex "rate limiting" "client sending"
29259 .cindex "limiting client sending rates"
29260 .oindex "&%smtp_ratelimit_*%&"
29261 The &%ratelimit%& ACL condition can be used to measure and control the rate at
29262 which clients can send email. This is more powerful than the
29263 &%smtp_ratelimit_*%& options, because those options control the rate of
29264 commands in a single SMTP session only, whereas the &%ratelimit%& condition
29265 works across all connections (concurrent and sequential) from the same client
29266 host. The syntax of the &%ratelimit%& condition is:
29268 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
29270 If the average client sending rate is less than &'m'& messages per time
29271 period &'p'& then the condition is false; otherwise it is true.
29273 As a side-effect, the &%ratelimit%& condition sets the expansion variable
29274 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
29275 configured value of &'m'&, and &$sender_rate_period$& to the configured value
29278 The parameter &'p'& is the smoothing time constant, in the form of an Exim
29279 time interval, for example, &`8h`& for eight hours. A larger time constant
29280 means that it takes Exim longer to forget a client's past behaviour. The
29281 parameter &'m'& is the maximum number of messages that a client is permitted to
29282 send in each time interval. It also specifies the number of messages permitted
29283 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
29284 constant, you can allow a client to send more messages in a burst without
29285 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
29286 both small, messages must be sent at an even rate.
29288 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
29289 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
29290 when deploying the &%ratelimit%& ACL condition. The script prints usage
29291 instructions when it is run with no arguments.
29293 The key is used to look up the data for calculating the client's average
29294 sending rate. This data is stored in Exim's spool directory, alongside the
29295 retry and other hints databases. The default key is &$sender_host_address$&,
29296 which means Exim computes the sending rate of each client host IP address.
29297 By changing the key you can change how Exim identifies clients for the purpose
29298 of ratelimiting. For example, to limit the sending rate of each authenticated
29299 user, independent of the computer they are sending from, set the key to
29300 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
29301 example, &$authenticated_id$& is only meaningful if the client has
29302 authenticated (which you can check with the &%authenticated%& ACL condition).
29304 The lookup key does not have to identify clients: If you want to limit the
29305 rate at which a recipient receives messages, you can use the key
29306 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
29309 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
29310 specifies what Exim measures the rate of, for example messages or recipients
29311 or bytes. You can adjust the measurement using the &%unique=%& and/or
29312 &%count=%& options. You can also control when Exim updates the recorded rate
29313 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
29314 separated by a slash, like the other parameters. They may appear in any order.
29316 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
29317 any options that alter the meaning of the stored data. The limit &'m'& is not
29318 stored, so you can alter the configured maximum rate and Exim will still
29319 remember clients' past behaviour. If you change the &%per_*%& mode or add or
29320 remove the &%unique=%& option, the lookup key changes so Exim will forget past
29321 behaviour. The lookup key is not affected by changes to the update mode and
29322 the &%count=%& option.
29325 .section "Ratelimit options for what is being measured" "ratoptmea"
29326 .cindex "rate limiting" "per_* options"
29327 The &%per_conn%& option limits the client's connection rate. It is not
29328 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
29329 &%acl_not_smtp_start%& ACLs.
29331 The &%per_mail%& option limits the client's rate of sending messages. This is
29332 the default if none of the &%per_*%& options is specified. It can be used in
29333 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
29334 &%acl_smtp_data%&, or &%acl_not_smtp%&.
29336 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
29337 the same ACLs as the &%per_mail%& option, though it is best to use this option
29338 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
29339 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
29340 in its MAIL command, which may be inaccurate or completely missing. You can
29341 follow the limit &'m'& in the configuration with K, M, or G to specify limits
29342 in kilobytes, megabytes, or gigabytes, respectively.
29344 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
29345 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
29346 &%acl_smtp_mime%&, &%acl_smtp_data%&, or &%acl_smtp_rcpt%& ACLs. In
29347 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
29348 ACLs the rate is updated with the total recipient count in one go. Note that
29349 in either case the rate limiting engine will see a message with many
29350 recipients as a large high-speed burst.
29352 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
29353 number of different recipients that the client has sent messages to in the
29354 last time period. That is, if the client repeatedly sends messages to the same
29355 recipient, its measured rate is not increased. This option can only be used in
29358 The &%per_cmd%& option causes Exim to recompute the rate every time the
29359 condition is processed. This can be used to limit the rate of any SMTP
29360 command. If it is used in multiple ACLs it can limit the aggregate rate of
29361 multiple different commands.
29363 The &%count=%& option can be used to alter how much Exim adds to the client's
29364 measured rate. For example, the &%per_byte%& option is equivalent to
29365 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
29366 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
29367 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
29369 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
29372 .section "Ratelimit update modes" "ratoptupd"
29373 .cindex "rate limiting" "reading data without updating"
29374 You can specify one of three options with the &%ratelimit%& condition to
29375 control when its database is updated. This section describes the &%readonly%&
29376 mode, and the next section describes the &%strict%& and &%leaky%& modes.
29378 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
29379 previously-computed rate to check against the limit.
29381 For example, you can test the client's sending rate and deny it access (when
29382 it is too fast) in the connect ACL. If the client passes this check then it
29383 can go on to send a message, in which case its recorded rate will be updated
29384 in the MAIL ACL. Subsequent connections from the same client will check this
29388 deny ratelimit = 100 / 5m / readonly
29389 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
29390 (max $sender_rate_limit)
29393 warn ratelimit = 100 / 5m / strict
29394 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
29395 (max $sender_rate_limit)
29398 If Exim encounters multiple &%ratelimit%& conditions with the same key when
29399 processing a message then it may increase the client's measured rate more than
29400 it should. For example, this will happen if you check the &%per_rcpt%& option
29401 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
29402 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
29403 multiple update problems by using the &%readonly%& option on later ratelimit
29406 The &%per_*%& options described above do not make sense in some ACLs. If you
29407 use a &%per_*%& option in an ACL where it is not normally permitted then the
29408 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
29409 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
29410 next section) so you must specify the &%readonly%& option explicitly.
29413 .section "Ratelimit options for handling fast clients" "ratoptfast"
29414 .cindex "rate limiting" "strict and leaky modes"
29415 If a client's average rate is greater than the maximum, the rate limiting
29416 engine can react in two possible ways, depending on the presence of the
29417 &%strict%& or &%leaky%& update modes. This is independent of the other
29418 counter-measures (such as rejecting the message) that may be specified by the
29421 The &%leaky%& (default) option means that the client's recorded rate is not
29422 updated if it is above the limit. The effect of this is that Exim measures the
29423 client's average rate of successfully sent email, which cannot be greater than
29424 the maximum allowed. If the client is over the limit it may suffer some
29425 counter-measures (as specified in the ACL), but it will still be able to send
29426 email at the configured maximum rate, whatever the rate of its attempts. This
29427 is generally the better choice if you have clients that retry automatically.
29428 For example, it does not prevent a sender with an over-aggressive retry rate
29429 from getting any email through.
29431 The &%strict%& option means that the client's recorded rate is always
29432 updated. The effect of this is that Exim measures the client's average rate
29433 of attempts to send email, which can be much higher than the maximum it is
29434 actually allowed. If the client is over the limit it may be subjected to
29435 counter-measures by the ACL. It must slow down and allow sufficient time to
29436 pass that its computed rate falls below the maximum before it can send email
29437 again. The time (the number of smoothing periods) it must wait and not
29438 attempt to send mail can be calculated with this formula:
29440 ln(peakrate/maxrate)
29444 .section "Limiting the rate of different events" "ratoptuniq"
29445 .cindex "rate limiting" "counting unique events"
29446 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
29447 rate of different events. For example, the &%per_addr%& option uses this
29448 mechanism to count the number of different recipients that the client has
29449 sent messages to in the last time period; it is equivalent to
29450 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
29451 measure the rate that a client uses different sender addresses with the
29452 options &`per_mail/unique=$sender_address`&.
29454 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
29455 has seen for that key. The whole set is thrown away when it is older than the
29456 rate smoothing period &'p'&, so each different event is counted at most once
29457 per period. In the &%leaky%& update mode, an event that causes the client to
29458 go over the limit is not added to the set, in the same way that the client's
29459 recorded rate is not updated in the same situation.
29461 When you combine the &%unique=%& and &%readonly%& options, the specific
29462 &%unique=%& value is ignored, and Exim just retrieves the client's stored
29465 The &%unique=%& mechanism needs more space in the ratelimit database than the
29466 other &%ratelimit%& options in order to store the event set. The number of
29467 unique values is potentially as large as the rate limit, so the extra space
29468 required increases with larger limits.
29470 The uniqueification is not perfect: there is a small probability that Exim
29471 will think a new event has happened before. If the sender's rate is less than
29472 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
29473 the measured rate can go above the limit, in which case Exim may under-count
29474 events by a significant margin. Fortunately, if the rate is high enough (2.7
29475 times the limit) that the false positive rate goes above 9%, then Exim will
29476 throw away the over-full event set before the measured rate falls below the
29477 limit. Therefore the only harm should be that exceptionally high sending rates
29478 are logged incorrectly; any countermeasures you configure will be as effective
29482 .section "Using rate limiting" "useratlim"
29483 Exim's other ACL facilities are used to define what counter-measures are taken
29484 when the rate limit is exceeded. This might be anything from logging a warning
29485 (for example, while measuring existing sending rates in order to define
29486 policy), through time delays to slow down fast senders, up to rejecting the
29487 message. For example:
29489 # Log all senders' rates
29490 warn ratelimit = 0 / 1h / strict
29491 log_message = Sender rate $sender_rate / $sender_rate_period
29493 # Slow down fast senders; note the need to truncate $sender_rate
29494 # at the decimal point.
29495 warn ratelimit = 100 / 1h / per_rcpt / strict
29496 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
29497 $sender_rate_limit }s
29499 # Keep authenticated users under control
29500 deny authenticated = *
29501 ratelimit = 100 / 1d / strict / $authenticated_id
29503 # System-wide rate limit
29504 defer message = Sorry, too busy. Try again later.
29505 ratelimit = 10 / 1s / $primary_hostname
29507 # Restrict incoming rate from each host, with a default
29508 # set using a macro and special cases looked up in a table.
29509 defer message = Sender rate exceeds $sender_rate_limit \
29510 messages per $sender_rate_period
29511 ratelimit = ${lookup {$sender_host_address} \
29512 cdb {DB/ratelimits.cdb} \
29513 {$value} {RATELIMIT} }
29515 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
29516 especially with the &%per_rcpt%& option, you may suffer from a performance
29517 bottleneck caused by locking on the ratelimit hints database. Apart from
29518 making your ACLs less complicated, you can reduce the problem by using a
29519 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
29520 this means that Exim will lose its hints data after a reboot (including retry
29521 hints, the callout cache, and ratelimit data).
29525 .section "Address verification" "SECTaddressverification"
29526 .cindex "verifying address" "options for"
29527 .cindex "policy control" "address verification"
29528 Several of the &%verify%& conditions described in section
29529 &<<SECTaclconditions>>& cause addresses to be verified. Section
29530 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
29531 The verification conditions can be followed by options that modify the
29532 verification process. The options are separated from the keyword and from each
29533 other by slashes, and some of them contain parameters. For example:
29535 verify = sender/callout
29536 verify = recipient/defer_ok/callout=10s,defer_ok
29538 The first stage of address verification, which always happens, is to run the
29539 address through the routers, in &"verify mode"&. Routers can detect the
29540 difference between verification and routing for delivery, and their actions can
29541 be varied by a number of generic options such as &%verify%& and &%verify_only%&
29542 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
29543 The available options are as follows:
29546 If the &%callout%& option is specified, successful routing to one or more
29547 remote hosts is followed by a &"callout"& to those hosts as an additional
29548 check. Callouts and their sub-options are discussed in the next section.
29550 If there is a defer error while doing verification routing, the ACL
29551 normally returns &"defer"&. However, if you include &%defer_ok%& in the
29552 options, the condition is forced to be true instead. Note that this is a main
29553 verification option as well as a suboption for callouts.
29555 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
29556 discusses the reporting of sender address verification failures.
29558 The &%success_on_redirect%& option causes verification always to succeed
29559 immediately after a successful redirection. By default, if a redirection
29560 generates just one address, that address is also verified. See further
29561 discussion in section &<<SECTredirwhilveri>>&.
29564 .cindex "verifying address" "differentiating failures"
29565 .vindex "&$recipient_verify_failure$&"
29566 .vindex "&$sender_verify_failure$&"
29567 .vindex "&$acl_verify_message$&"
29568 After an address verification failure, &$acl_verify_message$& contains the
29569 error message that is associated with the failure. It can be preserved by
29572 warn !verify = sender
29573 set acl_m0 = $acl_verify_message
29575 If you are writing your own custom rejection message or log message when
29576 denying access, you can use this variable to include information about the
29577 verification failure.
29579 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
29580 appropriate) contains one of the following words:
29583 &%qualify%&: The address was unqualified (no domain), and the message
29584 was neither local nor came from an exempted host.
29586 &%route%&: Routing failed.
29588 &%mail%&: Routing succeeded, and a callout was attempted; rejection
29589 occurred at or before the MAIL command (that is, on initial
29590 connection, HELO, or MAIL).
29592 &%recipient%&: The RCPT command in a callout was rejected.
29594 &%postmaster%&: The postmaster check in a callout was rejected.
29597 The main use of these variables is expected to be to distinguish between
29598 rejections of MAIL and rejections of RCPT in callouts.
29603 .section "Callout verification" "SECTcallver"
29604 .cindex "verifying address" "by callout"
29605 .cindex "callout" "verification"
29606 .cindex "SMTP" "callout verification"
29607 For non-local addresses, routing verifies the domain, but is unable to do any
29608 checking of the local part. There are situations where some means of verifying
29609 the local part is desirable. One way this can be done is to make an SMTP
29610 &'callback'& to a delivery host for the sender address or a &'callforward'& to
29611 a subsequent host for a recipient address, to see if the host accepts the
29612 address. We use the term &'callout'& to cover both cases. Note that for a
29613 sender address, the callback is not to the client host that is trying to
29614 deliver the message, but to one of the hosts that accepts incoming mail for the
29617 Exim does not do callouts by default. If you want them to happen, you must
29618 request them by setting appropriate options on the &%verify%& condition, as
29619 described below. This facility should be used with care, because it can add a
29620 lot of resource usage to the cost of verifying an address. However, Exim does
29621 cache the results of callouts, which helps to reduce the cost. Details of
29622 caching are in section &<<SECTcallvercache>>&.
29624 Recipient callouts are usually used only between hosts that are controlled by
29625 the same administration. For example, a corporate gateway host could use
29626 callouts to check for valid recipients on an internal mailserver. A successful
29627 callout does not guarantee that a real delivery to the address would succeed;
29628 on the other hand, a failing callout does guarantee that a delivery would fail.
29630 If the &%callout%& option is present on a condition that verifies an address, a
29631 second stage of verification occurs if the address is successfully routed to
29632 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
29633 &(manualroute)& router, where the router specifies the hosts. However, if a
29634 router that does not set up hosts routes to an &(smtp)& transport with a
29635 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
29636 &%hosts_override%& set, its hosts are always used, whether or not the router
29637 supplies a host list.
29638 Callouts are only supported on &(smtp)& transports.
29640 The port that is used is taken from the transport, if it is specified and is a
29641 remote transport. (For routers that do verification only, no transport need be
29642 specified.) Otherwise, the default SMTP port is used. If a remote transport
29643 specifies an outgoing interface, this is used; otherwise the interface is not
29644 specified. Likewise, the text that is used for the HELO command is taken from
29645 the transport's &%helo_data%& option; if there is no transport, the value of
29646 &$smtp_active_hostname$& is used.
29648 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
29649 test whether a bounce message could be delivered to the sender address. The
29650 following SMTP commands are sent:
29652 &`HELO `&<&'local host name'&>
29654 &`RCPT TO:`&<&'the address to be tested'&>
29657 LHLO is used instead of HELO if the transport's &%protocol%& option is
29660 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
29663 A recipient callout check is similar. By default, it also uses an empty address
29664 for the sender. This default is chosen because most hosts do not make use of
29665 the sender address when verifying a recipient. Using the same address means
29666 that a single cache entry can be used for each recipient. Some sites, however,
29667 do make use of the sender address when verifying. These are catered for by the
29668 &%use_sender%& and &%use_postmaster%& options, described in the next section.
29670 If the response to the RCPT command is a 2&'xx'& code, the verification
29671 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
29672 Exim tries the next host, if any. If there is a problem with all the remote
29673 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
29674 &%callout%& option is given, in which case the condition is forced to succeed.
29676 .cindex "SMTP" "output flushing, disabling for callout"
29677 A callout may take a little time. For this reason, Exim normally flushes SMTP
29678 output before performing a callout in an ACL, to avoid unexpected timeouts in
29679 clients when the SMTP PIPELINING extension is in use. The flushing can be
29680 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
29685 .section "Additional parameters for callouts" "CALLaddparcall"
29686 .cindex "callout" "additional parameters for"
29687 The &%callout%& option can be followed by an equals sign and a number of
29688 optional parameters, separated by commas. For example:
29690 verify = recipient/callout=10s,defer_ok
29692 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
29693 separate verify options, is retained for backwards compatibility, but is now
29694 deprecated. The additional parameters for &%callout%& are as follows:
29698 .vitem <&'a&~time&~interval'&>
29699 .cindex "callout" "timeout, specifying"
29700 This specifies the timeout that applies for the callout attempt to each host.
29703 verify = sender/callout=5s
29705 The default is 30 seconds. The timeout is used for each response from the
29706 remote host. It is also used for the initial connection, unless overridden by
29707 the &%connect%& parameter.
29710 .vitem &*connect&~=&~*&<&'time&~interval'&>
29711 .cindex "callout" "connection timeout, specifying"
29712 This parameter makes it possible to set a different (usually smaller) timeout
29713 for making the SMTP connection. For example:
29715 verify = sender/callout=5s,connect=1s
29717 If not specified, this timeout defaults to the general timeout value.
29719 .vitem &*defer_ok*&
29720 .cindex "callout" "defer, action on"
29721 When this parameter is present, failure to contact any host, or any other kind
29722 of temporary error, is treated as success by the ACL. However, the cache is not
29723 updated in this circumstance.
29725 .vitem &*fullpostmaster*&
29726 .cindex "callout" "full postmaster check"
29727 This operates like the &%postmaster%& option (see below), but if the check for
29728 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
29729 accordance with the specification in RFC 2821. The RFC states that the
29730 unqualified address &'postmaster'& should be accepted.
29733 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
29734 .cindex "callout" "sender when verifying header"
29735 When verifying addresses in header lines using the &%header_sender%&
29736 verification option, Exim behaves by default as if the addresses are envelope
29737 sender addresses from a message. Callout verification therefore tests to see
29738 whether a bounce message could be delivered, by using an empty address in the
29739 MAIL command. However, it is arguable that these addresses might never be used
29740 as envelope senders, and could therefore justifiably reject bounce messages
29741 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
29742 address to use in the MAIL command. For example:
29744 require verify = header_sender/callout=mailfrom=abcd@x.y.z
29746 This parameter is available only for the &%header_sender%& verification option.
29749 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
29750 .cindex "callout" "overall timeout, specifying"
29751 This parameter sets an overall timeout for performing a callout verification.
29754 verify = sender/callout=5s,maxwait=30s
29756 This timeout defaults to four times the callout timeout for individual SMTP
29757 commands. The overall timeout applies when there is more than one host that can
29758 be tried. The timeout is checked before trying the next host. This prevents
29759 very long delays if there are a large number of hosts and all are timing out
29760 (for example, when network connections are timing out).
29763 .vitem &*no_cache*&
29764 .cindex "callout" "cache, suppressing"
29765 .cindex "caching callout, suppressing"
29766 When this parameter is given, the callout cache is neither read nor updated.
29768 .vitem &*postmaster*&
29769 .cindex "callout" "postmaster; checking"
29770 When this parameter is set, a successful callout check is followed by a similar
29771 check for the local part &'postmaster'& at the same domain. If this address is
29772 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
29773 the postmaster check is recorded in a cache record; if it is a failure, this is
29774 used to fail subsequent callouts for the domain without a connection being
29775 made, until the cache record expires.
29777 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
29778 The postmaster check uses an empty sender in the MAIL command by default.
29779 You can use this parameter to do a postmaster check using a different address.
29782 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
29784 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
29785 one overrides. The &%postmaster%& parameter is equivalent to this example:
29787 require verify = sender/callout=postmaster_mailfrom=
29789 &*Warning*&: The caching arrangements for postmaster checking do not take
29790 account of the sender address. It is assumed that either the empty address or
29791 a fixed non-empty address will be used. All that Exim remembers is that the
29792 postmaster check for the domain succeeded or failed.
29796 .cindex "callout" "&""random""& check"
29797 When this parameter is set, before doing the normal callout check, Exim does a
29798 check for a &"random"& local part at the same domain. The local part is not
29799 really random &-- it is defined by the expansion of the option
29800 &%callout_random_local_part%&, which defaults to
29802 $primary_hostname-$tod_epoch-testing
29804 The idea here is to try to determine whether the remote host accepts all local
29805 parts without checking. If it does, there is no point in doing callouts for
29806 specific local parts. If the &"random"& check succeeds, the result is saved in
29807 a cache record, and used to force the current and subsequent callout checks to
29808 succeed without a connection being made, until the cache record expires.
29810 .vitem &*use_postmaster*&
29811 .cindex "callout" "sender for recipient check"
29812 This parameter applies to recipient callouts only. For example:
29814 deny !verify = recipient/callout=use_postmaster
29816 .vindex "&$qualify_domain$&"
29817 It causes a non-empty postmaster address to be used in the MAIL command when
29818 performing the callout for the recipient, and also for a &"random"& check if
29819 that is configured. The local part of the address is &`postmaster`& and the
29820 domain is the contents of &$qualify_domain$&.
29822 .vitem &*use_sender*&
29823 This option applies to recipient callouts only. For example:
29825 require verify = recipient/callout=use_sender
29827 It causes the message's actual sender address to be used in the MAIL
29828 command when performing the callout, instead of an empty address. There is no
29829 need to use this option unless you know that the called hosts make use of the
29830 sender when checking recipients. If used indiscriminately, it reduces the
29831 usefulness of callout caching.
29834 If you use any of the parameters that set a non-empty sender for the MAIL
29835 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
29836 &%use_sender%&), you should think about possible loops. Recipient checking is
29837 usually done between two hosts that are under the same management, and the host
29838 that receives the callouts is not normally configured to do callouts itself.
29839 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
29840 these circumstances.
29842 However, if you use a non-empty sender address for a callout to an arbitrary
29843 host, there is the likelihood that the remote host will itself initiate a
29844 callout check back to your host. As it is checking what appears to be a message
29845 sender, it is likely to use an empty address in MAIL, thus avoiding a
29846 callout loop. However, to be on the safe side it would be best to set up your
29847 own ACLs so that they do not do sender verification checks when the recipient
29848 is the address you use for header sender or postmaster callout checking.
29850 Another issue to think about when using non-empty senders for callouts is
29851 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
29852 by the sender/recipient combination; thus, for any given recipient, many more
29853 actual callouts are performed than when an empty sender or postmaster is used.
29858 .section "Callout caching" "SECTcallvercache"
29859 .cindex "hints database" "callout cache"
29860 .cindex "callout" "cache, description of"
29861 .cindex "caching" "callout"
29862 Exim caches the results of callouts in order to reduce the amount of resources
29863 used, unless you specify the &%no_cache%& parameter with the &%callout%&
29864 option. A hints database called &"callout"& is used for the cache. Two
29865 different record types are used: one records the result of a callout check for
29866 a specific address, and the other records information that applies to the
29867 entire domain (for example, that it accepts the local part &'postmaster'&).
29869 When an original callout fails, a detailed SMTP error message is given about
29870 the failure. However, for subsequent failures use the cache data, this message
29873 The expiry times for negative and positive address cache records are
29874 independent, and can be set by the global options &%callout_negative_expire%&
29875 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
29877 If a host gives a negative response to an SMTP connection, or rejects any
29878 commands up to and including
29882 (but not including the MAIL command with a non-empty address),
29883 any callout attempt is bound to fail. Exim remembers such failures in a
29884 domain cache record, which it uses to fail callouts for the domain without
29885 making new connections, until the domain record times out. There are two
29886 separate expiry times for domain cache records:
29887 &%callout_domain_negative_expire%& (default 3h) and
29888 &%callout_domain_positive_expire%& (default 7d).
29890 Domain records expire when the negative expiry time is reached if callouts
29891 cannot be made for the domain, or if the postmaster check failed.
29892 Otherwise, they expire when the positive expiry time is reached. This
29893 ensures that, for example, a host that stops accepting &"random"& local parts
29894 will eventually be noticed.
29896 The callout caching mechanism is based on the domain of the address that is
29897 being tested. If the domain routes to several hosts, it is assumed that their
29898 behaviour will be the same.
29902 .section "Sender address verification reporting" "SECTsenaddver"
29903 .cindex "verifying" "suppressing error details"
29904 See section &<<SECTaddressverification>>& for a general discussion of
29905 verification. When sender verification fails in an ACL, the details of the
29906 failure are given as additional output lines before the 550 response to the
29907 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
29910 MAIL FROM:<xyz@abc.example>
29912 RCPT TO:<pqr@def.example>
29913 550-Verification failed for <xyz@abc.example>
29914 550-Called: 192.168.34.43
29915 550-Sent: RCPT TO:<xyz@abc.example>
29916 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
29917 550 Sender verification failed
29919 If more than one RCPT command fails in the same way, the details are given
29920 only for the first of them. However, some administrators do not want to send
29921 out this much information. You can suppress the details by adding
29922 &`/no_details`& to the ACL statement that requests sender verification. For
29925 verify = sender/no_details
29928 .section "Redirection while verifying" "SECTredirwhilveri"
29929 .cindex "verifying" "redirection while"
29930 .cindex "address redirection" "while verifying"
29931 A dilemma arises when a local address is redirected by aliasing or forwarding
29932 during verification: should the generated addresses themselves be verified,
29933 or should the successful expansion of the original address be enough to verify
29934 it? By default, Exim takes the following pragmatic approach:
29937 When an incoming address is redirected to just one child address, verification
29938 continues with the child address, and if that fails to verify, the original
29939 verification also fails.
29941 When an incoming address is redirected to more than one child address,
29942 verification does not continue. A success result is returned.
29945 This seems the most reasonable behaviour for the common use of aliasing as a
29946 way of redirecting different local parts to the same mailbox. It means, for
29947 example, that a pair of alias entries of the form
29950 aw123: :fail: Gone away, no forwarding address
29952 work as expected, with both local parts causing verification failure. When a
29953 redirection generates more than one address, the behaviour is more like a
29954 mailing list, where the existence of the alias itself is sufficient for
29955 verification to succeed.
29957 It is possible, however, to change the default behaviour so that all successful
29958 redirections count as successful verifications, however many new addresses are
29959 generated. This is specified by the &%success_on_redirect%& verification
29960 option. For example:
29962 require verify = recipient/success_on_redirect/callout=10s
29964 In this example, verification succeeds if a router generates a new address, and
29965 the callout does not occur, because no address was routed to a remote host.
29967 When verification is being tested via the &%-bv%& option, the treatment of
29968 redirections is as just described, unless the &%-v%& or any debugging option is
29969 also specified. In that case, full verification is done for every generated
29970 address and a report is output for each of them.
29974 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
29975 .cindex "CSA" "verifying"
29976 Client SMTP Authorization is a system that allows a site to advertise
29977 which machines are and are not permitted to send email. This is done by placing
29978 special SRV records in the DNS; these are looked up using the client's HELO
29979 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
29980 Authorization checks in Exim are performed by the ACL condition:
29984 This fails if the client is not authorized. If there is a DNS problem, or if no
29985 valid CSA SRV record is found, or if the client is authorized, the condition
29986 succeeds. These three cases can be distinguished using the expansion variable
29987 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
29988 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
29989 be likely to cause problems for legitimate email.
29991 The error messages produced by the CSA code include slightly more
29992 detail. If &$csa_status$& is &"defer"&, this may be because of problems
29993 looking up the CSA SRV record, or problems looking up the CSA target
29994 address record. There are four reasons for &$csa_status$& being &"fail"&:
29997 The client's host name is explicitly not authorized.
29999 The client's IP address does not match any of the CSA target IP addresses.
30001 The client's host name is authorized but it has no valid target IP addresses
30002 (for example, the target's addresses are IPv6 and the client is using IPv4).
30004 The client's host name has no CSA SRV record but a parent domain has asserted
30005 that all subdomains must be explicitly authorized.
30008 The &%csa%& verification condition can take an argument which is the domain to
30009 use for the DNS query. The default is:
30011 verify = csa/$sender_helo_name
30013 This implementation includes an extension to CSA. If the query domain
30014 is an address literal such as [192.0.2.95], or if it is a bare IP
30015 address, Exim searches for CSA SRV records in the reverse DNS as if
30016 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
30019 verify = csa/$sender_host_address
30021 In fact, this is the check that Exim performs if the client does not say HELO.
30022 This extension can be turned off by setting the main configuration option
30023 &%dns_csa_use_reverse%& to be false.
30025 If a CSA SRV record is not found for the domain itself, a search
30026 is performed through its parent domains for a record which might be
30027 making assertions about subdomains. The maximum depth of this search is limited
30028 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
30029 default. Exim does not look for CSA SRV records in a top level domain, so the
30030 default settings handle HELO domains as long as seven
30031 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
30032 of legitimate HELO domains.
30034 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
30035 direct SRV lookups, this is not sufficient because of the extra parent domain
30036 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
30037 addresses into lookups in the reverse DNS space. The result of a successful
30040 ${lookup dnsdb {csa=$sender_helo_name}}
30042 has two space-separated fields: an authorization code and a target host name.
30043 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
30044 authorization required but absent, or &"?"& for unknown.
30049 .section "Bounce address tag validation" "SECTverifyPRVS"
30050 .cindex "BATV, verifying"
30051 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
30052 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
30053 Genuine incoming bounce messages should therefore always be addressed to
30054 recipients that have a valid tag. This scheme is a way of detecting unwanted
30055 bounce messages caused by sender address forgeries (often called &"collateral
30056 spam"&), because the recipients of such messages do not include valid tags.
30058 There are two expansion items to help with the implementation of the BATV
30059 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
30060 the original envelope sender address by using a simple key to add a hash of the
30061 address and some time-based randomizing information. The &%prvs%& expansion
30062 item creates a signed address, and the &%prvscheck%& expansion item checks one.
30063 The syntax of these expansion items is described in section
30064 &<<SECTexpansionitems>>&.
30066 As an example, suppose the secret per-address keys are stored in an MySQL
30067 database. A query to look up the key for an address could be defined as a macro
30070 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
30071 WHERE sender='${quote_mysql:$prvscheck_address}'\
30074 Suppose also that the senders who make use of BATV are defined by an address
30075 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
30078 # Bounces: drop unsigned addresses for BATV senders
30079 deny message = This address does not send an unsigned reverse path
30081 recipients = +batv_senders
30083 # Bounces: In case of prvs-signed address, check signature.
30084 deny message = Invalid reverse path signature.
30086 condition = ${prvscheck {$local_part@$domain}\
30087 {PRVSCHECK_SQL}{1}}
30088 !condition = $prvscheck_result
30090 The first statement rejects recipients for bounce messages that are addressed
30091 to plain BATV sender addresses, because it is known that BATV senders do not
30092 send out messages with plain sender addresses. The second statement rejects
30093 recipients that are prvs-signed, but with invalid signatures (either because
30094 the key is wrong, or the signature has timed out).
30096 A non-prvs-signed address is not rejected by the second statement, because the
30097 &%prvscheck%& expansion yields an empty string if its first argument is not a
30098 prvs-signed address, thus causing the &%condition%& condition to be false. If
30099 the first argument is a syntactically valid prvs-signed address, the yield is
30100 the third string (in this case &"1"&), whether or not the cryptographic and
30101 timeout checks succeed. The &$prvscheck_result$& variable contains the result
30102 of the checks (empty for failure, &"1"& for success).
30104 There is one more issue you must consider when implementing prvs-signing:
30105 you have to ensure that the routers accept prvs-signed addresses and
30106 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
30107 router to remove the signature with a configuration along these lines:
30111 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
30113 This works because, if the third argument of &%prvscheck%& is empty, the result
30114 of the expansion of a prvs-signed address is the decoded value of the original
30115 address. This router should probably be the first of your routers that handles
30118 To create BATV-signed addresses in the first place, a transport of this form
30121 external_smtp_batv:
30123 return_path = ${prvs {$return_path} \
30124 {${lookup mysql{SELECT \
30125 secret FROM batv_prvs WHERE \
30126 sender='${quote_mysql:$sender_address}'} \
30129 If no key can be found for the existing return path, no signing takes place.
30133 .section "Using an ACL to control relaying" "SECTrelaycontrol"
30134 .cindex "&ACL;" "relay control"
30135 .cindex "relaying" "control by ACL"
30136 .cindex "policy control" "relay control"
30137 An MTA is said to &'relay'& a message if it receives it from some host and
30138 delivers it directly to another host as a result of a remote address contained
30139 within it. Redirecting a local address via an alias or forward file and then
30140 passing the message on to another host is not relaying,
30141 .cindex "&""percent hack""&"
30142 but a redirection as a result of the &"percent hack"& is.
30144 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
30145 A host which is acting as a gateway or an MX backup is concerned with incoming
30146 relaying from arbitrary hosts to a specific set of domains. On the other hand,
30147 a host which is acting as a smart host for a number of clients is concerned
30148 with outgoing relaying from those clients to the Internet at large. Often the
30149 same host is fulfilling both functions,
30151 . as illustrated in the diagram below,
30153 but in principle these two kinds of relaying are entirely independent. What is
30154 not wanted is the transmission of mail from arbitrary remote hosts through your
30155 system to arbitrary domains.
30158 You can implement relay control by means of suitable statements in the ACL that
30159 runs for each RCPT command. For convenience, it is often easiest to use
30160 Exim's named list facility to define the domains and hosts involved. For
30161 example, suppose you want to do the following:
30164 Deliver a number of domains to mailboxes on the local host (or process them
30165 locally in some other way). Let's say these are &'my.dom1.example'& and
30166 &'my.dom2.example'&.
30168 Relay mail for a number of other domains for which you are the secondary MX.
30169 These might be &'friend1.example'& and &'friend2.example'&.
30171 Relay mail from the hosts on your local LAN, to whatever domains are involved.
30172 Suppose your LAN is 192.168.45.0/24.
30176 In the main part of the configuration, you put the following definitions:
30178 domainlist local_domains = my.dom1.example : my.dom2.example
30179 domainlist relay_to_domains = friend1.example : friend2.example
30180 hostlist relay_from_hosts = 192.168.45.0/24
30182 Now you can use these definitions in the ACL that is run for every RCPT
30186 accept domains = +local_domains : +relay_to_domains
30187 accept hosts = +relay_from_hosts
30189 The first statement accepts any RCPT command that contains an address in
30190 the local or relay domains. For any other domain, control passes to the second
30191 statement, which accepts the command only if it comes from one of the relay
30192 hosts. In practice, you will probably want to make your ACL more sophisticated
30193 than this, for example, by including sender and recipient verification. The
30194 default configuration includes a more comprehensive example, which is described
30195 in chapter &<<CHAPdefconfil>>&.
30199 .section "Checking a relay configuration" "SECTcheralcon"
30200 .cindex "relaying" "checking control of"
30201 You can check the relay characteristics of your configuration in the same way
30202 that you can test any ACL behaviour for an incoming SMTP connection, by using
30203 the &%-bh%& option to run a fake SMTP session with which you interact.
30205 For specifically testing for unwanted relaying, the host
30206 &'relay-test.mail-abuse.org'& provides a useful service. If you telnet to this
30207 host from the host on which Exim is running, using the normal telnet port, you
30208 will see a normal telnet connection message and then quite a long delay. Be
30209 patient. The remote host is making an SMTP connection back to your host, and
30210 trying a number of common probes to test for open relay vulnerability. The
30211 results of the tests will eventually appear on your terminal.
30216 . ////////////////////////////////////////////////////////////////////////////
30217 . ////////////////////////////////////////////////////////////////////////////
30219 .chapter "Content scanning at ACL time" "CHAPexiscan"
30220 .scindex IIDcosca "content scanning" "at ACL time"
30221 The extension of Exim to include content scanning at ACL time, formerly known
30222 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
30223 was integrated into the main source for Exim release 4.50, and Tom continues to
30224 maintain it. Most of the wording of this chapter is taken from Tom's
30227 It is also possible to scan the content of messages at other times. The
30228 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
30229 scanning after all the ACLs have run. A transport filter can be used to scan
30230 messages at delivery time (see the &%transport_filter%& option, described in
30231 chapter &<<CHAPtransportgeneric>>&).
30233 If you want to include the ACL-time content-scanning features when you compile
30234 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
30235 &_Local/Makefile_&. When you do that, the Exim binary is built with:
30238 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
30239 for all MIME parts for SMTP and non-SMTP messages, respectively.
30241 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
30242 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
30243 run at the end of message reception (the &%acl_smtp_data%& ACL).
30245 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
30246 of messages, or parts of messages, for debugging purposes.
30248 Additional expansion variables that are set in the new ACL and by the new
30251 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
30254 There is another content-scanning configuration option for &_Local/Makefile_&,
30255 called WITH_OLD_DEMIME. If this is set, the old, deprecated &%demime%& ACL
30256 condition is compiled, in addition to all the other content-scanning features.
30258 Content-scanning is continually evolving, and new features are still being
30259 added. While such features are still unstable and liable to incompatible
30260 changes, they are made available in Exim by setting options whose names begin
30261 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
30262 this manual. You can find out about them by reading the file called
30263 &_doc/experimental.txt_&.
30265 All the content-scanning facilities work on a MBOX copy of the message that is
30266 temporarily created in a file called:
30268 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
30270 The &_.eml_& extension is a friendly hint to virus scanners that they can
30271 expect an MBOX-like structure inside that file. The file is created when the
30272 first content scanning facility is called. Subsequent calls to content
30273 scanning conditions open the same file again. The directory is recursively
30274 removed when the &%acl_smtp_data%& ACL has finished running, unless
30276 control = no_mbox_unspool
30278 has been encountered. When the MIME ACL decodes files, they are put into the
30279 same directory by default.
30283 .section "Scanning for viruses" "SECTscanvirus"
30284 .cindex "virus scanning"
30285 .cindex "content scanning" "for viruses"
30286 .cindex "content scanning" "the &%malware%& condition"
30287 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
30288 It supports a &"generic"& interface to scanners called via the shell, and
30289 specialized interfaces for &"daemon"& type virus scanners, which are resident
30290 in memory and thus are much faster.
30293 .oindex "&%av_scanner%&"
30294 You can set the &%av_scanner%& option in first part of the Exim configuration
30295 file to specify which scanner to use, together with any additional options that
30296 are needed. The basic syntax is as follows:
30298 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
30300 If you do not set &%av_scanner%&, it defaults to
30302 av_scanner = sophie:/var/run/sophie
30304 If the value of &%av_scanner%& starts with a dollar character, it is expanded
30306 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
30307 The following scanner types are supported in this release:
30310 .vitem &%aveserver%&
30311 .cindex "virus scanners" "Kaspersky"
30312 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
30313 at &url(http://www.kaspersky.com). This scanner type takes one option,
30314 which is the path to the daemon's UNIX socket. The default is shown in this
30317 av_scanner = aveserver:/var/run/aveserver
30322 .cindex "virus scanners" "clamd"
30323 This daemon-type scanner is GPL and free. You can get it at
30324 &url(http://www.clamav.net/). Some older versions of clamd do not seem to
30325 unpack MIME containers, so it used to be recommended to unpack MIME attachments
30326 in the MIME ACL. This no longer believed to be necessary. One option is
30327 required: either the path and name of a UNIX socket file, or a hostname or IP
30328 number, and a port, separated by space, as in the second of these examples:
30330 av_scanner = clamd:/opt/clamd/socket
30331 av_scanner = clamd:192.0.2.3 1234
30332 av_scanner = clamd:192.0.2.3 1234:local
30333 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
30335 If the value of av_scanner points to a UNIX socket file or contains the local
30336 keyword, then the ClamAV interface will pass a filename containing the data
30337 to be scanned, which will should normally result in less I/O happening and be
30338 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
30339 Exim does not assume that there is a common filesystem with the remote host.
30340 There is an option WITH_OLD_CLAMAV_STREAM in &_src/EDITME_& available, should
30341 you be running a version of ClamAV prior to 0.95.
30343 The final example shows that multiple TCP targets can be specified. Exim will
30344 randomly use one for each incoming email (i.e. it load balances them). Note
30345 that only TCP targets may be used if specifying a list of scanners; a UNIX
30346 socket cannot be mixed in with TCP targets. If one of the servers becomes
30347 unavailable, Exim will try the remaining one(s) until it finds one that works.
30348 When a clamd server becomes unreachable, Exim will log a message. Exim does
30349 not keep track of scanner state between multiple messages, and the scanner
30350 selection is random, so the message will get logged in the mainlog for each
30351 email that the down scanner gets chosen first (message wrapped to be readable):
30353 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
30354 clamd: connection to localhost, port 3310 failed
30355 (Connection refused)
30358 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
30359 contributing the code for this scanner.
30362 .cindex "virus scanners" "command line interface"
30363 This is the keyword for the generic command line scanner interface. It can be
30364 used to attach virus scanners that are invoked from the shell. This scanner
30365 type takes 3 mandatory options:
30368 The full path and name of the scanner binary, with all command line options,
30369 and a placeholder (&`%s`&) for the directory to scan.
30372 A regular expression to match against the STDOUT and STDERR output of the
30373 virus scanner. If the expression matches, a virus was found. You must make
30374 absolutely sure that this expression matches on &"virus found"&. This is called
30375 the &"trigger"& expression.
30378 Another regular expression, containing exactly one pair of parentheses, to
30379 match the name of the virus found in the scanners output. This is called the
30380 &"name"& expression.
30383 For example, Sophos Sweep reports a virus on a line like this:
30385 Virus 'W32/Magistr-B' found in file ./those.bat
30387 For the trigger expression, we can match the phrase &"found in file"&. For the
30388 name expression, we want to extract the W32/Magistr-B string, so we can match
30389 for the single quotes left and right of it. Altogether, this makes the
30390 configuration setting:
30392 av_scanner = cmdline:\
30393 /path/to/sweep -ss -all -rec -archive %s:\
30394 found in file:'(.+)'
30397 .cindex "virus scanners" "DrWeb"
30398 The DrWeb daemon scanner (&url(http://www.sald.com/)) interface takes one
30399 argument, either a full path to a UNIX socket, or an IP address and port
30400 separated by white space, as in these examples:
30402 av_scanner = drweb:/var/run/drwebd.sock
30403 av_scanner = drweb:192.168.2.20 31337
30405 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
30406 is used. Thanks to Alex Miller for contributing the code for this scanner.
30409 .cindex "virus scanners" "F-Secure"
30410 The F-Secure daemon scanner (&url(http://www.f-secure.com)) takes one
30411 argument which is the path to a UNIX socket. For example:
30413 av_scanner = fsecure:/path/to/.fsav
30415 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
30416 Thelmen for contributing the code for this scanner.
30418 .vitem &%kavdaemon%&
30419 .cindex "virus scanners" "Kaspersky"
30420 This is the scanner daemon of Kaspersky Version 4. This version of the
30421 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
30422 scanner type takes one option, which is the path to the daemon's UNIX socket.
30425 av_scanner = kavdaemon:/opt/AVP/AvpCtl
30427 The default path is &_/var/run/AvpCtl_&.
30430 .cindex "virus scanners" "mksd"
30431 This is a daemon type scanner that is aimed mainly at Polish users, though some
30432 parts of documentation are now available in English. You can get it at
30433 &url(http://linux.mks.com.pl/). The only option for this scanner type is
30434 the maximum number of processes used simultaneously to scan the attachments,
30435 provided that the demime facility is employed and also provided that mksd has
30436 been run with at least the same number of child processes. For example:
30438 av_scanner = mksd:2
30440 You can safely omit this option (the default value is 1).
30443 .cindex "virus scanners" "simple socket-connected"
30444 This is a general-purpose way of talking to simple scanner daemons
30445 running on the local machine.
30446 There are four options:
30447 an address (which may be an IP addres and port, or the path of a Unix socket),
30448 a commandline to send (may include a single %s which will be replaced with
30449 the path to the mail file to be scanned),
30450 an RE to trigger on from the returned data,
30451 an RE to extract malware_name from the returned data.
30454 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)\$
30456 Default for the socket specifier is &_/tmp/malware.sock_&.
30457 Default for the commandline is &_%s\n_&.
30458 Both regular-expressions are required.
30461 .cindex "virus scanners" "Sophos and Sophie"
30462 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
30463 You can get Sophie at &url(http://www.clanfield.info/sophie/). The only option
30464 for this scanner type is the path to the UNIX socket that Sophie uses for
30465 client communication. For example:
30467 av_scanner = sophie:/tmp/sophie
30469 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
30473 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
30474 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
30477 The &%av_scanner%& option is expanded each time &%malware%& is called. This
30478 makes it possible to use different scanners. See further below for an example.
30479 The &%malware%& condition caches its results, so when you use it multiple times
30480 for the same message, the actual scanning process is only carried out once.
30481 However, using expandable items in &%av_scanner%& disables this caching, in
30482 which case each use of the &%malware%& condition causes a new scan of the
30485 The &%malware%& condition takes a right-hand argument that is expanded before
30486 use. It can then be one of
30489 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
30490 The condition succeeds if a virus was found, and fail otherwise. This is the
30493 &"false"& or &"0"& or an empty string, in which case no scanning is done and
30494 the condition fails immediately.
30496 A regular expression, in which case the message is scanned for viruses. The
30497 condition succeeds if a virus is found and its name matches the regular
30498 expression. This allows you to take special actions on certain types of virus.
30501 You can append &`/defer_ok`& to the &%malware%& condition to accept messages
30502 even if there is a problem with the virus scanner. Otherwise, such a problem
30503 causes the ACL to defer.
30505 .vindex "&$malware_name$&"
30506 When a virus is found, the condition sets up an expansion variable called
30507 &$malware_name$& that contains the name of the virus. You can use it in a
30508 &%message%& modifier that specifies the error returned to the sender, and/or in
30511 If your virus scanner cannot unpack MIME and TNEF containers itself, you should
30512 use the &%demime%& condition (see section &<<SECTdemimecond>>&) before the
30513 &%malware%& condition.
30515 Beware the interaction of Exim's &%message_size_limit%& with any size limits
30516 imposed by your anti-virus scanner.
30518 Here is a very simple scanning example:
30520 deny message = This message contains malware ($malware_name)
30524 The next example accepts messages when there is a problem with the scanner:
30526 deny message = This message contains malware ($malware_name)
30528 malware = */defer_ok
30530 The next example shows how to use an ACL variable to scan with both sophie and
30531 aveserver. It assumes you have set:
30533 av_scanner = $acl_m0
30535 in the main Exim configuration.
30537 deny message = This message contains malware ($malware_name)
30538 set acl_m0 = sophie
30541 deny message = This message contains malware ($malware_name)
30542 set acl_m0 = aveserver
30547 .section "Scanning with SpamAssassin" "SECTscanspamass"
30548 .cindex "content scanning" "for spam"
30549 .cindex "spam scanning"
30550 .cindex "SpamAssassin"
30551 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
30552 score and a report for the message. You can get SpamAssassin at
30553 &url(http://www.spamassassin.org), or, if you have a working Perl
30554 installation, you can use CPAN by running:
30556 perl -MCPAN -e 'install Mail::SpamAssassin'
30558 SpamAssassin has its own set of configuration files. Please review its
30559 documentation to see how you can tweak it. The default installation should work
30562 .oindex "&%spamd_address%&"
30563 After having installed and configured SpamAssassin, start the &%spamd%& daemon.
30564 By default, it listens on 127.0.0.1, TCP port 783. If you use another host or
30565 port for &%spamd%&, you must set the &%spamd_address%& option in the global
30566 part of the Exim configuration as follows (example):
30568 spamd_address = 192.168.99.45 387
30570 You do not need to set this option if you use the default. As of version 2.60,
30571 &%spamd%& also supports communication over UNIX sockets. If you want to use
30572 these, supply &%spamd_address%& with an absolute file name instead of a
30575 spamd_address = /var/run/spamd_socket
30577 You can have multiple &%spamd%& servers to improve scalability. These can
30578 reside on other hardware reachable over the network. To specify multiple
30579 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
30580 option, separated with colons:
30582 spamd_address = 192.168.2.10 783 : \
30583 192.168.2.11 783 : \
30586 Up to 32 &%spamd%& servers are supported. The servers are queried in a random
30587 fashion. When a server fails to respond to the connection attempt, all other
30588 servers are tried until one succeeds. If no server responds, the &%spam%&
30591 &*Warning*&: It is not possible to use the UNIX socket connection method with
30592 multiple &%spamd%& servers.
30594 The &%spamd_address%& variable is expanded before use if it starts with
30595 a dollar sign. In this case, the expansion may return a string that is
30596 used as the list so that multiple spamd servers can be the result of an
30599 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
30600 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
30602 deny message = This message was classified as SPAM
30605 The right-hand side of the &%spam%& condition specifies a name. This is
30606 relevant if you have set up multiple SpamAssassin profiles. If you do not want
30607 to scan using a specific profile, but rather use the SpamAssassin system-wide
30608 default profile, you can scan for an unknown name, or simply use &"nobody"&.
30609 However, you must put something on the right-hand side.
30611 The name allows you to use per-domain or per-user antispam profiles in
30612 principle, but this is not straightforward in practice, because a message may
30613 have multiple recipients, not necessarily all in the same domain. Because the
30614 &%spam%& condition has to be called from a DATA ACL in order to be able to
30615 read the contents of the message, the variables &$local_part$& and &$domain$&
30618 The right-hand side of the &%spam%& condition is expanded before being used, so
30619 you can put lookups or conditions there. When the right-hand side evaluates to
30620 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
30623 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
30624 large ones may cause significant performance degradation. As most spam messages
30625 are quite small, it is recommended that you do not scan the big ones. For
30628 deny message = This message was classified as SPAM
30629 condition = ${if < {$message_size}{10K}}
30633 The &%spam%& condition returns true if the threshold specified in the user's
30634 SpamAssassin profile has been matched or exceeded. If you want to use the
30635 &%spam%& condition for its side effects (see the variables below), you can make
30636 it always return &"true"& by appending &`:true`& to the username.
30638 .cindex "spam scanning" "returned variables"
30639 When the &%spam%& condition is run, it sets up a number of expansion
30640 variables. These variables are saved with the received message, thus they are
30641 available for use at delivery time.
30644 .vitem &$spam_score$&
30645 The spam score of the message, for example &"3.4"& or &"30.5"&. This is useful
30646 for inclusion in log or reject messages.
30648 .vitem &$spam_score_int$&
30649 The spam score of the message, multiplied by ten, as an integer value. For
30650 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
30651 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
30652 The integer value is useful for numeric comparisons in conditions.
30654 .vitem &$spam_bar$&
30655 A string consisting of a number of &"+"& or &"-"& characters, representing the
30656 integer part of the spam score value. A spam score of 4.4 would have a
30657 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
30658 headers, since MUAs can match on such strings.
30660 .vitem &$spam_report$&
30661 A multiline text table, containing the full SpamAssassin report for the
30662 message. Useful for inclusion in headers or reject messages.
30665 The &%spam%& condition caches its results unless expansion in
30666 spamd_address was used. If you call it again with the same user name, it
30667 does not scan again, but rather returns the same values as before.
30669 The &%spam%& condition returns DEFER if there is any error while running
30670 the message through SpamAssassin or if the expansion of spamd_address
30671 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
30672 statement block), append &`/defer_ok`& to the right-hand side of the
30673 spam condition, like this:
30675 deny message = This message was classified as SPAM
30676 spam = joe/defer_ok
30678 This causes messages to be accepted even if there is a problem with &%spamd%&.
30680 Here is a longer, commented example of the use of the &%spam%&
30683 # put headers in all messages (no matter if spam or not)
30684 warn spam = nobody:true
30685 add_header = X-Spam-Score: $spam_score ($spam_bar)
30686 add_header = X-Spam-Report: $spam_report
30688 # add second subject line with *SPAM* marker when message
30689 # is over threshold
30691 add_header = Subject: *SPAM* $h_Subject:
30693 # reject spam at high scores (> 12)
30694 deny message = This message scored $spam_score spam points.
30696 condition = ${if >{$spam_score_int}{120}{1}{0}}
30701 .section "Scanning MIME parts" "SECTscanmimepart"
30702 .cindex "content scanning" "MIME parts"
30703 .cindex "MIME content scanning"
30704 .oindex "&%acl_smtp_mime%&"
30705 .oindex "&%acl_not_smtp_mime%&"
30706 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
30707 each MIME part of an SMTP message, including multipart types, in the sequence
30708 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
30709 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
30710 options may both refer to the same ACL if you want the same processing in both
30713 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
30714 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
30715 the case of a non-SMTP message. However, a MIME ACL is called only if the
30716 message contains a &'Content-Type:'& header line. When a call to a MIME
30717 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
30718 result code is sent to the client. In the case of an SMTP message, the
30719 &%acl_smtp_data%& ACL is not called when this happens.
30721 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
30722 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
30723 condition to match against the raw MIME part. You can also use the
30724 &%mime_regex%& condition to match against the decoded MIME part (see section
30725 &<<SECTscanregex>>&).
30727 At the start of a MIME ACL, a number of variables are set from the header
30728 information for the relevant MIME part. These are described below. The contents
30729 of the MIME part are not by default decoded into a disk file except for MIME
30730 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
30731 part into a disk file, you can use the &%decode%& condition. The general
30734 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
30736 The right hand side is expanded before use. After expansion,
30740 &"0"& or &"false"&, in which case no decoding is done.
30742 The string &"default"&. In that case, the file is put in the temporary
30743 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
30744 a sequential file name consisting of the message id and a sequence number. The
30745 full path and name is available in &$mime_decoded_filename$& after decoding.
30747 A full path name starting with a slash. If the full name is an existing
30748 directory, it is used as a replacement for the default directory. The filename
30749 is then sequentially assigned. If the path does not exist, it is used as
30750 the full path and file name.
30752 If the string does not start with a slash, it is used as the
30753 filename, and the default path is then used.
30755 The &%decode%& condition normally succeeds. It is only false for syntax
30756 errors or unusual circumstances such as memory shortages. You can easily decode
30757 a file with its original, proposed filename using
30759 decode = $mime_filename
30761 However, you should keep in mind that &$mime_filename$& might contain
30762 anything. If you place files outside of the default path, they are not
30763 automatically unlinked.
30765 For RFC822 attachments (these are messages attached to messages, with a
30766 content-type of &"message/rfc822"&), the ACL is called again in the same manner
30767 as for the primary message, only that the &$mime_is_rfc822$& expansion
30768 variable is set (see below). Attached messages are always decoded to disk
30769 before being checked, and the files are unlinked once the check is done.
30771 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
30772 used to match regular expressions against raw and decoded MIME parts,
30773 respectively. They are described in section &<<SECTscanregex>>&.
30775 .cindex "MIME content scanning" "returned variables"
30776 The following list describes all expansion variables that are
30777 available in the MIME ACL:
30780 .vitem &$mime_boundary$&
30781 If the current part is a multipart (see &$mime_is_multipart$&) below, it should
30782 have a boundary string, which is stored in this variable. If the current part
30783 has no boundary parameter in the &'Content-Type:'& header, this variable
30784 contains the empty string.
30786 .vitem &$mime_charset$&
30787 This variable contains the character set identifier, if one was found in the
30788 &'Content-Type:'& header. Examples for charset identifiers are:
30794 Please note that this value is not normalized, so you should do matches
30795 case-insensitively.
30797 .vitem &$mime_content_description$&
30798 This variable contains the normalized content of the &'Content-Description:'&
30799 header. It can contain a human-readable description of the parts content. Some
30800 implementations repeat the filename for attachments here, but they are usually
30801 only used for display purposes.
30803 .vitem &$mime_content_disposition$&
30804 This variable contains the normalized content of the &'Content-Disposition:'&
30805 header. You can expect strings like &"attachment"& or &"inline"& here.
30807 .vitem &$mime_content_id$&
30808 This variable contains the normalized content of the &'Content-ID:'& header.
30809 This is a unique ID that can be used to reference a part from another part.
30811 .vitem &$mime_content_size$&
30812 This variable is set only after the &%decode%& modifier (see above) has been
30813 successfully run. It contains the size of the decoded part in kilobytes. The
30814 size is always rounded up to full kilobytes, so only a completely empty part
30815 has a &$mime_content_size$& of zero.
30817 .vitem &$mime_content_transfer_encoding$&
30818 This variable contains the normalized content of the
30819 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
30820 type. Typical values are &"base64"& and &"quoted-printable"&.
30822 .vitem &$mime_content_type$&
30823 If the MIME part has a &'Content-Type:'& header, this variable contains its
30824 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
30825 are some examples of popular MIME types, as they may appear in this variable:
30829 application/octet-stream
30833 If the MIME part has no &'Content-Type:'& header, this variable contains the
30836 .vitem &$mime_decoded_filename$&
30837 This variable is set only after the &%decode%& modifier (see above) has been
30838 successfully run. It contains the full path and file name of the file
30839 containing the decoded data.
30844 .vitem &$mime_filename$&
30845 This is perhaps the most important of the MIME variables. It contains a
30846 proposed filename for an attachment, if one was found in either the
30847 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
30848 RFC2047 decoded, but no additional sanity checks are done. If no filename was
30849 found, this variable contains the empty string.
30851 .vitem &$mime_is_coverletter$&
30852 This variable attempts to differentiate the &"cover letter"& of an e-mail from
30853 attached data. It can be used to clamp down on flashy or unnecessarily encoded
30854 content in the cover letter, while not restricting attachments at all.
30856 The variable contains 1 (true) for a MIME part believed to be part of the
30857 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
30861 The outermost MIME part of a message is always a cover letter.
30864 If a multipart/alternative or multipart/related MIME part is a cover letter,
30865 so are all MIME subparts within that multipart.
30868 If any other multipart is a cover letter, the first subpart is a cover letter,
30869 and the rest are attachments.
30872 All parts contained within an attachment multipart are attachments.
30875 As an example, the following will ban &"HTML mail"& (including that sent with
30876 alternative plain text), while allowing HTML files to be attached. HTML
30877 coverletter mail attached to non-HMTL coverletter mail will also be allowed:
30879 deny message = HTML mail is not accepted here
30880 !condition = $mime_is_rfc822
30881 condition = $mime_is_coverletter
30882 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
30884 .vitem &$mime_is_multipart$&
30885 This variable has the value 1 (true) when the current part has the main type
30886 &"multipart"&, for example &"multipart/alternative"& or &"multipart/mixed"&.
30887 Since multipart entities only serve as containers for other parts, you may not
30888 want to carry out specific actions on them.
30890 .vitem &$mime_is_rfc822$&
30891 This variable has the value 1 (true) if the current part is not a part of the
30892 checked message itself, but part of an attached message. Attached message
30893 decoding is fully recursive.
30895 .vitem &$mime_part_count$&
30896 This variable is a counter that is raised for each processed MIME part. It
30897 starts at zero for the very first part (which is usually a multipart). The
30898 counter is per-message, so it is reset when processing RFC822 attachments (see
30899 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
30900 complete, so you can use it in the DATA ACL to determine the number of MIME
30901 parts of a message. For non-MIME messages, this variable contains the value -1.
30906 .section "Scanning with regular expressions" "SECTscanregex"
30907 .cindex "content scanning" "with regular expressions"
30908 .cindex "regular expressions" "content scanning with"
30909 You can specify your own custom regular expression matches on the full body of
30910 the message, or on individual MIME parts.
30912 The &%regex%& condition takes one or more regular expressions as arguments and
30913 matches them against the full message (when called in the DATA ACL) or a raw
30914 MIME part (when called in the MIME ACL). The &%regex%& condition matches
30915 linewise, with a maximum line length of 32K characters. That means you cannot
30916 have multiline matches with the &%regex%& condition.
30918 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
30919 to 32K of decoded content (the whole content at once, not linewise). If the
30920 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
30921 is decoded automatically when &%mime_regex%& is executed (using default path
30922 and filename values). If the decoded data is larger than 32K, only the first
30923 32K characters are checked.
30925 The regular expressions are passed as a colon-separated list. To include a
30926 literal colon, you must double it. Since the whole right-hand side string is
30927 expanded before being used, you must also escape dollar signs and backslashes
30928 with more backslashes, or use the &`\N`& facility to disable expansion.
30929 Here is a simple example that contains two regular expressions:
30931 deny message = contains blacklisted regex ($regex_match_string)
30932 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
30934 The conditions returns true if any one of the regular expressions matches. The
30935 &$regex_match_string$& expansion variable is then set up and contains the
30936 matching regular expression.
30938 &*Warning*&: With large messages, these conditions can be fairly
30944 .section "The demime condition" "SECTdemimecond"
30945 .cindex "content scanning" "MIME checking"
30946 .cindex "MIME content scanning"
30947 The &%demime%& ACL condition provides MIME unpacking, sanity checking and file
30948 extension blocking. It is usable only in the DATA and non-SMTP ACLs. The
30949 &%demime%& condition uses a simpler interface to MIME decoding than the MIME
30950 ACL functionality, but provides no additional facilities. Please note that this
30951 condition is deprecated and kept only for backward compatibility. You must set
30952 the WITH_OLD_DEMIME option in &_Local/Makefile_& at build time to be able to
30953 use the &%demime%& condition.
30955 The &%demime%& condition unpacks MIME containers in the message. It detects
30956 errors in MIME containers and can match file extensions found in the message
30957 against a list. Using this facility produces files containing the unpacked MIME
30958 parts of the message in the temporary scan directory. If you do antivirus
30959 scanning, it is recommended that you use the &%demime%& condition before the
30960 antivirus (&%malware%&) condition.
30962 On the right-hand side of the &%demime%& condition you can pass a
30963 colon-separated list of file extensions that it should match against. For
30966 deny message = Found blacklisted file attachment
30967 demime = vbs:com:bat:pif:prf:lnk
30969 If one of the file extensions is found, the condition is true, otherwise it is
30970 false. If there is a temporary error while demimeing (for example, &"disk
30971 full"&), the condition defers, and the message is temporarily rejected (unless
30972 the condition is on a &%warn%& verb).
30974 The right-hand side is expanded before being treated as a list, so you can have
30975 conditions and lookups there. If it expands to an empty string, &"false"&, or
30976 zero (&"0"&), no demimeing is done and the condition is false.
30978 The &%demime%& condition set the following variables:
30981 .vitem &$demime_errorlevel$&
30982 .vindex "&$demime_errorlevel$&"
30983 When an error is detected in a MIME container, this variable contains the
30984 severity of the error, as an integer number. The higher the value, the more
30985 severe the error (the current maximum value is 3). If this variable is unset or
30986 zero, no error occurred.
30988 .vitem &$demime_reason$&
30989 .vindex "&$demime_reason$&"
30990 When &$demime_errorlevel$& is greater than zero, this variable contains a
30991 human-readable text string describing the MIME error that occurred.
30995 .vitem &$found_extension$&
30996 .vindex "&$found_extension$&"
30997 When the &%demime%& condition is true, this variable contains the file
30998 extension it found.
31001 Both &$demime_errorlevel$& and &$demime_reason$& are set by the first call of
31002 the &%demime%& condition, and are not changed on subsequent calls.
31004 If you do not want to check for file extensions, but rather use the &%demime%&
31005 condition for unpacking or error checking purposes, pass &"*"& as the
31006 right-hand side value. Here is a more elaborate example of how to use this
31009 # Reject messages with serious MIME container errors
31010 deny message = Found MIME error ($demime_reason).
31012 condition = ${if >{$demime_errorlevel}{2}{1}{0}}
31014 # Reject known virus spreading file extensions.
31015 # Accepting these is pretty much braindead.
31016 deny message = contains $found_extension file (blacklisted).
31017 demime = com:vbs:bat:pif:scr
31019 # Freeze .exe and .doc files. Postmaster can
31020 # examine them and eventually thaw them.
31021 deny log_message = Another $found_extension file.
31030 . ////////////////////////////////////////////////////////////////////////////
31031 . ////////////////////////////////////////////////////////////////////////////
31033 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
31034 "Local scan function"
31035 .scindex IIDlosca "&[local_scan()]& function" "description of"
31036 .cindex "customizing" "input scan using C function"
31037 .cindex "policy control" "by local scan function"
31038 In these days of email worms, viruses, and ever-increasing spam, some sites
31039 want to apply a lot of checking to messages before accepting them.
31041 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
31042 passing messages to external virus and spam scanning software. You can also do
31043 a certain amount in Exim itself through string expansions and the &%condition%&
31044 condition in the ACL that runs after the SMTP DATA command or the ACL for
31045 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
31047 To allow for further customization to a site's own requirements, there is the
31048 possibility of linking Exim with a private message scanning function, written
31049 in C. If you want to run code that is written in something other than C, you
31050 can of course use a little C stub to call it.
31052 The local scan function is run once for every incoming message, at the point
31053 when Exim is just about to accept the message.
31054 It can therefore be used to control non-SMTP messages from local processes as
31055 well as messages arriving via SMTP.
31057 Exim applies a timeout to calls of the local scan function, and there is an
31058 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
31059 Zero means &"no timeout"&.
31060 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
31061 before calling the local scan function, so that the most common types of crash
31062 are caught. If the timeout is exceeded or one of those signals is caught, the
31063 incoming message is rejected with a temporary error if it is an SMTP message.
31064 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
31065 code. The incident is logged on the main and reject logs.
31069 .section "Building Exim to use a local scan function" "SECID207"
31070 .cindex "&[local_scan()]& function" "building Exim to use"
31071 To make use of the local scan function feature, you must tell Exim where your
31072 function is before building Exim, by setting LOCAL_SCAN_SOURCE in your
31073 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
31074 directory, so you might set
31076 LOCAL_SCAN_SOURCE=Local/local_scan.c
31078 for example. The function must be called &[local_scan()]&. It is called by
31079 Exim after it has received a message, when the success return code is about to
31080 be sent. This is after all the ACLs have been run. The return code from your
31081 function controls whether the message is actually accepted or not. There is a
31082 commented template function (that just accepts the message) in the file
31083 _src/local_scan.c_.
31085 If you want to make use of Exim's run time configuration file to set options
31086 for your &[local_scan()]& function, you must also set
31088 LOCAL_SCAN_HAS_OPTIONS=yes
31090 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
31095 .section "API for local_scan()" "SECTapiforloc"
31096 .cindex "&[local_scan()]& function" "API description"
31097 You must include this line near the start of your code:
31099 #include "local_scan.h"
31101 This header file defines a number of variables and other values, and the
31102 prototype for the function itself. Exim is coded to use unsigned char values
31103 almost exclusively, and one of the things this header defines is a shorthand
31104 for &`unsigned char`& called &`uschar`&.
31105 It also contains the following macro definitions, to simplify casting character
31106 strings and pointers to character strings:
31108 #define CS (char *)
31109 #define CCS (const char *)
31110 #define CSS (char **)
31111 #define US (unsigned char *)
31112 #define CUS (const unsigned char *)
31113 #define USS (unsigned char **)
31115 The function prototype for &[local_scan()]& is:
31117 extern int local_scan(int fd, uschar **return_text);
31119 The arguments are as follows:
31122 &%fd%& is a file descriptor for the file that contains the body of the message
31123 (the -D file). The file is open for reading and writing, but updating it is not
31124 recommended. &*Warning*&: You must &'not'& close this file descriptor.
31126 The descriptor is positioned at character 19 of the file, which is the first
31127 character of the body itself, because the first 19 characters are the message
31128 id followed by &`-D`& and a newline. If you rewind the file, you should use the
31129 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
31130 case this changes in some future version.
31132 &%return_text%& is an address which you can use to return a pointer to a text
31133 string at the end of the function. The value it points to on entry is NULL.
31136 The function must return an &%int%& value which is one of the following macros:
31139 .vitem &`LOCAL_SCAN_ACCEPT`&
31140 .vindex "&$local_scan_data$&"
31141 The message is accepted. If you pass back a string of text, it is saved with
31142 the message, and made available in the variable &$local_scan_data$&. No
31143 newlines are permitted (if there are any, they are turned into spaces) and the
31144 maximum length of text is 1000 characters.
31146 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
31147 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
31148 queued without immediate delivery, and is frozen.
31150 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
31151 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
31152 queued without immediate delivery.
31154 .vitem &`LOCAL_SCAN_REJECT`&
31155 The message is rejected; the returned text is used as an error message which is
31156 passed back to the sender and which is also logged. Newlines are permitted &--
31157 they cause a multiline response for SMTP rejections, but are converted to
31158 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
31161 .vitem &`LOCAL_SCAN_TEMPREJECT`&
31162 The message is temporarily rejected; the returned text is used as an error
31163 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
31166 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
31167 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
31168 message is not written to the reject log. It has the effect of unsetting the
31169 &%rejected_header%& log selector for just this rejection. If
31170 &%rejected_header%& is already unset (see the discussion of the
31171 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
31172 same as LOCAL_SCAN_REJECT.
31174 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
31175 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
31176 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
31179 If the message is not being received by interactive SMTP, rejections are
31180 reported by writing to &%stderr%& or by sending an email, as configured by the
31181 &%-oe%& command line options.
31185 .section "Configuration options for local_scan()" "SECTconoptloc"
31186 .cindex "&[local_scan()]& function" "configuration options"
31187 It is possible to have option settings in the main configuration file
31188 that set values in static variables in the &[local_scan()]& module. If you
31189 want to do this, you must have the line
31191 LOCAL_SCAN_HAS_OPTIONS=yes
31193 in your &_Local/Makefile_& when you build Exim. (This line is in
31194 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
31195 file, you must define static variables to hold the option values, and a table
31198 The table must be a vector called &%local_scan_options%&, of type
31199 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
31200 and a pointer to the variable that holds the value. The entries must appear in
31201 alphabetical order. Following &%local_scan_options%& you must also define a
31202 variable called &%local_scan_options_count%& that contains the number of
31203 entries in the table. Here is a short example, showing two kinds of option:
31205 static int my_integer_option = 42;
31206 static uschar *my_string_option = US"a default string";
31208 optionlist local_scan_options[] = {
31209 { "my_integer", opt_int, &my_integer_option },
31210 { "my_string", opt_stringptr, &my_string_option }
31213 int local_scan_options_count =
31214 sizeof(local_scan_options)/sizeof(optionlist);
31216 The values of the variables can now be changed from Exim's runtime
31217 configuration file by including a local scan section as in this example:
31221 my_string = some string of text...
31223 The available types of option data are as follows:
31226 .vitem &*opt_bool*&
31227 This specifies a boolean (true/false) option. The address should point to a
31228 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
31229 that are defined as &"1"& and &"0"&, respectively. If you want to detect
31230 whether such a variable has been set at all, you can initialize it to
31231 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
31234 .vitem &*opt_fixed*&
31235 This specifies a fixed point number, such as is used for load averages.
31236 The address should point to a variable of type &`int`&. The value is stored
31237 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
31240 This specifies an integer; the address should point to a variable of type
31241 &`int`&. The value may be specified in any of the integer formats accepted by
31244 .vitem &*opt_mkint*&
31245 This is the same as &%opt_int%&, except that when such a value is output in a
31246 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
31247 printed with the suffix K or M.
31249 .vitem &*opt_octint*&
31250 This also specifies an integer, but the value is always interpreted as an
31251 octal integer, whether or not it starts with the digit zero, and it is
31252 always output in octal.
31254 .vitem &*opt_stringptr*&
31255 This specifies a string value; the address must be a pointer to a
31256 variable that points to a string (for example, of type &`uschar *`&).
31258 .vitem &*opt_time*&
31259 This specifies a time interval value. The address must point to a variable of
31260 type &`int`&. The value that is placed there is a number of seconds.
31263 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
31264 out the values of all the &[local_scan()]& options.
31268 .section "Available Exim variables" "SECID208"
31269 .cindex "&[local_scan()]& function" "available Exim variables"
31270 The header &_local_scan.h_& gives you access to a number of C variables. These
31271 are the only ones that are guaranteed to be maintained from release to release.
31272 Note, however, that you can obtain the value of any Exim expansion variable,
31273 including &$recipients$&, by calling &'expand_string()'&. The exported
31274 C variables are as follows:
31277 .vitem &*int&~body_linecount*&
31278 This variable contains the number of lines in the message's body.
31280 .vitem &*int&~body_zerocount*&
31281 This variable contains the number of binary zero bytes in the message's body.
31283 .vitem &*unsigned&~int&~debug_selector*&
31284 This variable is set to zero when no debugging is taking place. Otherwise, it
31285 is a bitmap of debugging selectors. Two bits are identified for use in
31286 &[local_scan()]&; they are defined as macros:
31289 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
31290 testing option that is not privileged &-- any caller may set it. All the
31291 other selector bits can be set only by admin users.
31294 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
31295 by the &`+local_scan`& debug selector. It is not included in the default set
31299 Thus, to write to the debugging output only when &`+local_scan`& has been
31300 selected, you should use code like this:
31302 if ((debug_selector & D_local_scan) != 0)
31303 debug_printf("xxx", ...);
31305 .vitem &*uschar&~*expand_string_message*&
31306 After a failing call to &'expand_string()'& (returned value NULL), the
31307 variable &%expand_string_message%& contains the error message, zero-terminated.
31309 .vitem &*header_line&~*header_list*&
31310 A pointer to a chain of header lines. The &%header_line%& structure is
31313 .vitem &*header_line&~*header_last*&
31314 A pointer to the last of the header lines.
31316 .vitem &*uschar&~*headers_charset*&
31317 The value of the &%headers_charset%& configuration option.
31319 .vitem &*BOOL&~host_checking*&
31320 This variable is TRUE during a host checking session that is initiated by the
31321 &%-bh%& command line option.
31323 .vitem &*uschar&~*interface_address*&
31324 The IP address of the interface that received the message, as a string. This
31325 is NULL for locally submitted messages.
31327 .vitem &*int&~interface_port*&
31328 The port on which this message was received. When testing with the &%-bh%&
31329 command line option, the value of this variable is -1 unless a port has been
31330 specified via the &%-oMi%& option.
31332 .vitem &*uschar&~*message_id*&
31333 This variable contains Exim's message id for the incoming message (the value of
31334 &$message_exim_id$&) as a zero-terminated string.
31336 .vitem &*uschar&~*received_protocol*&
31337 The name of the protocol by which the message was received.
31339 .vitem &*int&~recipients_count*&
31340 The number of accepted recipients.
31342 .vitem &*recipient_item&~*recipients_list*&
31343 .cindex "recipient" "adding in local scan"
31344 .cindex "recipient" "removing in local scan"
31345 The list of accepted recipients, held in a vector of length
31346 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
31347 can add additional recipients by calling &'receive_add_recipient()'& (see
31348 below). You can delete recipients by removing them from the vector and
31349 adjusting the value in &%recipients_count%&. In particular, by setting
31350 &%recipients_count%& to zero you remove all recipients. If you then return the
31351 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
31352 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
31353 and then call &'receive_add_recipient()'& as often as needed.
31355 .vitem &*uschar&~*sender_address*&
31356 The envelope sender address. For bounce messages this is the empty string.
31358 .vitem &*uschar&~*sender_host_address*&
31359 The IP address of the sending host, as a string. This is NULL for
31360 locally-submitted messages.
31362 .vitem &*uschar&~*sender_host_authenticated*&
31363 The name of the authentication mechanism that was used, or NULL if the message
31364 was not received over an authenticated SMTP connection.
31366 .vitem &*uschar&~*sender_host_name*&
31367 The name of the sending host, if known.
31369 .vitem &*int&~sender_host_port*&
31370 The port on the sending host.
31372 .vitem &*BOOL&~smtp_input*&
31373 This variable is TRUE for all SMTP input, including BSMTP.
31375 .vitem &*BOOL&~smtp_batched_input*&
31376 This variable is TRUE for BSMTP input.
31378 .vitem &*int&~store_pool*&
31379 The contents of this variable control which pool of memory is used for new
31380 requests. See section &<<SECTmemhanloc>>& for details.
31384 .section "Structure of header lines" "SECID209"
31385 The &%header_line%& structure contains the members listed below.
31386 You can add additional header lines by calling the &'header_add()'& function
31387 (see below). You can cause header lines to be ignored (deleted) by setting
31392 .vitem &*struct&~header_line&~*next*&
31393 A pointer to the next header line, or NULL for the last line.
31395 .vitem &*int&~type*&
31396 A code identifying certain headers that Exim recognizes. The codes are printing
31397 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
31398 Notice in particular that any header line whose type is * is not transmitted
31399 with the message. This flagging is used for header lines that have been
31400 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
31401 lines.) Effectively, * means &"deleted"&.
31403 .vitem &*int&~slen*&
31404 The number of characters in the header line, including the terminating and any
31407 .vitem &*uschar&~*text*&
31408 A pointer to the text of the header. It always ends with a newline, followed by
31409 a zero byte. Internal newlines are preserved.
31414 .section "Structure of recipient items" "SECID210"
31415 The &%recipient_item%& structure contains these members:
31418 .vitem &*uschar&~*address*&
31419 This is a pointer to the recipient address as it was received.
31421 .vitem &*int&~pno*&
31422 This is used in later Exim processing when top level addresses are created by
31423 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
31424 and must always contain -1 at this stage.
31426 .vitem &*uschar&~*errors_to*&
31427 If this value is not NULL, bounce messages caused by failing to deliver to the
31428 recipient are sent to the address it contains. In other words, it overrides the
31429 envelope sender for this one recipient. (Compare the &%errors_to%& generic
31430 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
31431 an unqualified address, Exim qualifies it using the domain from
31432 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
31433 is NULL for all recipients.
31438 .section "Available Exim functions" "SECID211"
31439 .cindex "&[local_scan()]& function" "available Exim functions"
31440 The header &_local_scan.h_& gives you access to a number of Exim functions.
31441 These are the only ones that are guaranteed to be maintained from release to
31445 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
31446 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
31448 This function creates a child process that runs the command specified by
31449 &%argv%&. The environment for the process is specified by &%envp%&, which can
31450 be NULL if no environment variables are to be passed. A new umask is supplied
31451 for the process in &%newumask%&.
31453 Pipes to the standard input and output of the new process are set up
31454 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
31455 standard error is cloned to the standard output. If there are any file
31456 descriptors &"in the way"& in the new process, they are closed. If the final
31457 argument is TRUE, the new process is made into a process group leader.
31459 The function returns the pid of the new process, or -1 if things go wrong.
31461 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
31462 This function waits for a child process to terminate, or for a timeout (in
31463 seconds) to expire. A timeout value of zero means wait as long as it takes. The
31464 return value is as follows:
31469 The process terminated by a normal exit and the value is the process
31475 The process was terminated by a signal and the value is the negation of the
31481 The process timed out.
31485 The was some other error in wait(); &%errno%& is still set.
31488 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
31489 This function provide you with a means of submitting a new message to
31490 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
31491 want, but this packages it all up for you.) The function creates a pipe,
31492 forks a subprocess that is running
31494 exim -t -oem -oi -f <>
31496 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
31497 that is connected to the standard input. The yield of the function is the PID
31498 of the subprocess. You can then write a message to the file descriptor, with
31499 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
31501 When you have finished, call &'child_close()'& to wait for the process to
31502 finish and to collect its ending status. A timeout value of zero is usually
31503 fine in this circumstance. Unless you have made a mistake with the recipient
31504 addresses, you should get a return code of zero.
31507 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
31508 *sender_authentication)*&
31509 This function is a more sophisticated version of &'child_open()'&. The command
31512 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
31514 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
31517 .vitem &*void&~debug_printf(char&~*,&~...)*&
31518 This is Exim's debugging function, with arguments as for &'(printf()'&. The
31519 output is written to the standard error stream. If no debugging is selected,
31520 calls to &'debug_printf()'& have no effect. Normally, you should make calls
31521 conditional on the &`local_scan`& debug selector by coding like this:
31523 if ((debug_selector & D_local_scan) != 0)
31524 debug_printf("xxx", ...);
31527 .vitem &*uschar&~*expand_string(uschar&~*string)*&
31528 This is an interface to Exim's string expansion code. The return value is the
31529 expanded string, or NULL if there was an expansion failure.
31530 The C variable &%expand_string_message%& contains an error message after an
31531 expansion failure. If expansion does not change the string, the return value is
31532 the pointer to the input string. Otherwise, the return value points to a new
31533 block of memory that was obtained by a call to &'store_get()'&. See section
31534 &<<SECTmemhanloc>>& below for a discussion of memory handling.
31536 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
31537 This function allows you to an add additional header line at the end of the
31538 existing ones. The first argument is the type, and should normally be a space
31539 character. The second argument is a format string and any number of
31540 substitution arguments as for &[sprintf()]&. You may include internal newlines
31541 if you want, and you must ensure that the string ends with a newline.
31543 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
31544 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
31545 This function adds a new header line at a specified point in the header
31546 chain. The header itself is specified as for &'header_add()'&.
31548 If &%name%& is NULL, the new header is added at the end of the chain if
31549 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
31550 NULL, the header lines are searched for the first non-deleted header that
31551 matches the name. If one is found, the new header is added before it if
31552 &%after%& is false. If &%after%& is true, the new header is added after the
31553 found header and any adjacent subsequent ones with the same name (even if
31554 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
31555 option controls where the header is added. If it is true, addition is at the
31556 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
31557 headers, or at the top if there are no &'Received:'& headers, you could use
31559 header_add_at_position(TRUE, US"Received", TRUE,
31560 ' ', "X-xxx: ...");
31562 Normally, there is always at least one non-deleted &'Received:'& header, but
31563 there may not be if &%received_header_text%& expands to an empty string.
31566 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
31567 This function removes header lines. If &%occurrence%& is zero or negative, all
31568 occurrences of the header are removed. If occurrence is greater than zero, that
31569 particular instance of the header is removed. If no header(s) can be found that
31570 match the specification, the function does nothing.
31573 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
31574 int&~length,&~BOOL&~notdel)*&"
31575 This function tests whether the given header has the given name. It is not just
31576 a string comparison, because white space is permitted between the name and the
31577 colon. If the &%notdel%& argument is true, a false return is forced for all
31578 &"deleted"& headers; otherwise they are not treated specially. For example:
31580 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
31582 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
31583 .cindex "base64 encoding" "functions for &[local_scan()]& use"
31584 This function base64-encodes a string, which is passed by address and length.
31585 The text may contain bytes of any value, including zero. The result is passed
31586 back in dynamic memory that is obtained by calling &'store_get()'&. It is
31589 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
31590 This function decodes a base64-encoded string. Its arguments are a
31591 zero-terminated base64-encoded string and the address of a variable that is set
31592 to point to the result, which is in dynamic memory. The length of the decoded
31593 string is the yield of the function. If the input is invalid base64 data, the
31594 yield is -1. A zero byte is added to the end of the output string to make it
31595 easy to interpret as a C string (assuming it contains no zeros of its own). The
31596 added zero byte is not included in the returned count.
31598 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
31599 This function checks for a match in a domain list. Domains are always
31600 matched caselessly. The return value is one of the following:
31602 &`OK `& match succeeded
31603 &`FAIL `& match failed
31604 &`DEFER `& match deferred
31606 DEFER is usually caused by some kind of lookup defer, such as the
31607 inability to contact a database.
31609 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
31611 This function checks for a match in a local part list. The third argument
31612 controls case-sensitivity. The return values are as for
31613 &'lss_match_domain()'&.
31615 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
31617 This function checks for a match in an address list. The third argument
31618 controls the case-sensitivity of the local part match. The domain is always
31619 matched caselessly. The return values are as for &'lss_match_domain()'&.
31621 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
31623 This function checks for a match in a host list. The most common usage is
31626 lss_match_host(sender_host_name, sender_host_address, ...)
31628 .vindex "&$sender_host_address$&"
31629 An empty address field matches an empty item in the host list. If the host name
31630 is NULL, the name corresponding to &$sender_host_address$& is automatically
31631 looked up if a host name is required to match an item in the list. The return
31632 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
31633 returns ERROR in the case when it had to look up a host name, but the lookup
31636 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
31638 This function writes to Exim's log files. The first argument should be zero (it
31639 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
31640 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
31641 them. It specifies to which log or logs the message is written. The remaining
31642 arguments are a format and relevant insertion arguments. The string should not
31643 contain any newlines, not even at the end.
31646 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
31647 This function adds an additional recipient to the message. The first argument
31648 is the recipient address. If it is unqualified (has no domain), it is qualified
31649 with the &%qualify_recipient%& domain. The second argument must always be -1.
31651 This function does not allow you to specify a private &%errors_to%& address (as
31652 described with the structure of &%recipient_item%& above), because it pre-dates
31653 the addition of that field to the structure. However, it is easy to add such a
31654 value afterwards. For example:
31656 receive_add_recipient(US"monitor@mydom.example", -1);
31657 recipients_list[recipients_count-1].errors_to =
31658 US"postmaster@mydom.example";
31661 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
31662 This is a convenience function to remove a named recipient from the list of
31663 recipients. It returns true if a recipient was removed, and false if no
31664 matching recipient could be found. The argument must be a complete email
31671 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
31672 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
31673 This function decodes strings that are encoded according to RFC 2047. Typically
31674 these are the contents of header lines. First, each &"encoded word"& is decoded
31675 from the Q or B encoding into a byte-string. Then, if provided with the name of
31676 a charset encoding, and if the &[iconv()]& function is available, an attempt is
31677 made to translate the result to the named character set. If this fails, the
31678 binary string is returned with an error message.
31680 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
31681 maximum MIME word length is enforced. The third argument is the target
31682 encoding, or NULL if no translation is wanted.
31684 .cindex "binary zero" "in RFC 2047 decoding"
31685 .cindex "RFC 2047" "binary zero in"
31686 If a binary zero is encountered in the decoded string, it is replaced by the
31687 contents of the &%zeroval%& argument. For use with Exim headers, the value must
31688 not be 0 because header lines are handled as zero-terminated strings.
31690 The function returns the result of processing the string, zero-terminated; if
31691 &%lenptr%& is not NULL, the length of the result is set in the variable to
31692 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
31694 If an error is encountered, the function returns NULL and uses the &%error%&
31695 argument to return an error message. The variable pointed to by &%error%& is
31696 set to NULL if there is no error; it may be set non-NULL even when the function
31697 returns a non-NULL value if decoding was successful, but there was a problem
31701 .vitem &*int&~smtp_fflush(void)*&
31702 This function is used in conjunction with &'smtp_printf()'&, as described
31705 .vitem &*void&~smtp_printf(char&~*,&~...)*&
31706 The arguments of this function are like &[printf()]&; it writes to the SMTP
31707 output stream. You should use this function only when there is an SMTP output
31708 stream, that is, when the incoming message is being received via interactive
31709 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
31710 is FALSE. If you want to test for an incoming message from another host (as
31711 opposed to a local process that used the &%-bs%& command line option), you can
31712 test the value of &%sender_host_address%&, which is non-NULL when a remote host
31715 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
31716 output function, so it can be used for all forms of SMTP connection.
31718 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
31719 must start with an appropriate response code: 550 if you are going to return
31720 LOCAL_SCAN_REJECT, 451 if you are going to return
31721 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
31722 initial lines of a multi-line response, the code must be followed by a hyphen
31723 to indicate that the line is not the final response line. You must also ensure
31724 that the lines you write terminate with CRLF. For example:
31726 smtp_printf("550-this is some extra info\r\n");
31727 return LOCAL_SCAN_REJECT;
31729 Note that you can also create multi-line responses by including newlines in
31730 the data returned via the &%return_text%& argument. The added value of using
31731 &'smtp_printf()'& is that, for instance, you could introduce delays between
31732 multiple output lines.
31734 The &'smtp_printf()'& function does not return any error indication, because it
31735 does not automatically flush pending output, and therefore does not test
31736 the state of the stream. (In the main code of Exim, flushing and error
31737 detection is done when Exim is ready for the next SMTP input command.) If
31738 you want to flush the output and check for an error (for example, the
31739 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
31740 arguments. It flushes the output stream, and returns a non-zero value if there
31743 .vitem &*void&~*store_get(int)*&
31744 This function accesses Exim's internal store (memory) manager. It gets a new
31745 chunk of memory whose size is given by the argument. Exim bombs out if it ever
31746 runs out of memory. See the next section for a discussion of memory handling.
31748 .vitem &*void&~*store_get_perm(int)*&
31749 This function is like &'store_get()'&, but it always gets memory from the
31750 permanent pool. See the next section for a discussion of memory handling.
31752 .vitem &*uschar&~*string_copy(uschar&~*string)*&
31755 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
31758 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
31759 These three functions create strings using Exim's dynamic memory facilities.
31760 The first makes a copy of an entire string. The second copies up to a maximum
31761 number of characters, indicated by the second argument. The third uses a format
31762 and insertion arguments to create a new string. In each case, the result is a
31763 pointer to a new string in the current memory pool. See the next section for
31769 .section "More about Exim's memory handling" "SECTmemhanloc"
31770 .cindex "&[local_scan()]& function" "memory handling"
31771 No function is provided for freeing memory, because that is never needed.
31772 The dynamic memory that Exim uses when receiving a message is automatically
31773 recycled if another message is received by the same process (this applies only
31774 to incoming SMTP connections &-- other input methods can supply only one
31775 message at a time). After receiving the last message, a reception process
31778 Because it is recycled, the normal dynamic memory cannot be used for holding
31779 data that must be preserved over a number of incoming messages on the same SMTP
31780 connection. However, Exim in fact uses two pools of dynamic memory; the second
31781 one is not recycled, and can be used for this purpose.
31783 If you want to allocate memory that remains available for subsequent messages
31784 in the same SMTP connection, you should set
31786 store_pool = POOL_PERM
31788 before calling the function that does the allocation. There is no need to
31789 restore the value if you do not need to; however, if you do want to revert to
31790 the normal pool, you can either restore the previous value of &%store_pool%& or
31791 set it explicitly to POOL_MAIN.
31793 The pool setting applies to all functions that get dynamic memory, including
31794 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
31795 There is also a convenience function called &'store_get_perm()'& that gets a
31796 block of memory from the permanent pool while preserving the value of
31803 . ////////////////////////////////////////////////////////////////////////////
31804 . ////////////////////////////////////////////////////////////////////////////
31806 .chapter "System-wide message filtering" "CHAPsystemfilter"
31807 .scindex IIDsysfil1 "filter" "system filter"
31808 .scindex IIDsysfil2 "filtering all mail"
31809 .scindex IIDsysfil3 "system filter"
31810 The previous chapters (on ACLs and the local scan function) describe checks
31811 that can be applied to messages before they are accepted by a host. There is
31812 also a mechanism for checking messages once they have been received, but before
31813 they are delivered. This is called the &'system filter'&.
31815 The system filter operates in a similar manner to users' filter files, but it
31816 is run just once per message (however many recipients the message has).
31817 It should not normally be used as a substitute for routing, because &%deliver%&
31818 commands in a system router provide new envelope recipient addresses.
31819 The system filter must be an Exim filter. It cannot be a Sieve filter.
31821 The system filter is run at the start of a delivery attempt, before any routing
31822 is done. If a message fails to be completely delivered at the first attempt,
31823 the system filter is run again at the start of every retry.
31824 If you want your filter to do something only once per message, you can make use
31825 of the &%first_delivery%& condition in an &%if%& command in the filter to
31826 prevent it happening on retries.
31828 .vindex "&$domain$&"
31829 .vindex "&$local_part$&"
31830 &*Warning*&: Because the system filter runs just once, variables that are
31831 specific to individual recipient addresses, such as &$local_part$& and
31832 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
31833 you want to run a centrally-specified filter for each recipient address
31834 independently, you can do so by setting up a suitable &(redirect)& router, as
31835 described in section &<<SECTperaddfil>>& below.
31838 .section "Specifying a system filter" "SECID212"
31839 .cindex "uid (user id)" "system filter"
31840 .cindex "gid (group id)" "system filter"
31841 The name of the file that contains the system filter must be specified by
31842 setting &%system_filter%&. If you want the filter to run under a uid and gid
31843 other than root, you must also set &%system_filter_user%& and
31844 &%system_filter_group%& as appropriate. For example:
31846 system_filter = /etc/mail/exim.filter
31847 system_filter_user = exim
31849 If a system filter generates any deliveries directly to files or pipes (via the
31850 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
31851 specified by setting &%system_filter_file_transport%& and
31852 &%system_filter_pipe_transport%&, respectively. Similarly,
31853 &%system_filter_reply_transport%& must be set to handle any messages generated
31854 by the &%reply%& command.
31857 .section "Testing a system filter" "SECID213"
31858 You can run simple tests of a system filter in the same way as for a user
31859 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
31860 are permitted only in system filters are recognized.
31862 If you want to test the combined effect of a system filter and a user filter,
31863 you can use both &%-bF%& and &%-bf%& on the same command line.
31867 .section "Contents of a system filter" "SECID214"
31868 The language used to specify system filters is the same as for users' filter
31869 files. It is described in the separate end-user document &'Exim's interface to
31870 mail filtering'&. However, there are some additional features that are
31871 available only in system filters; these are described in subsequent sections.
31872 If they are encountered in a user's filter file or when testing with &%-bf%&,
31875 .cindex "frozen messages" "manual thaw; testing in filter"
31876 There are two special conditions which, though available in users' filter
31877 files, are designed for use in system filters. The condition &%first_delivery%&
31878 is true only for the first attempt at delivering a message, and
31879 &%manually_thawed%& is true only if the message has been frozen, and
31880 subsequently thawed by an admin user. An explicit forced delivery counts as a
31881 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
31883 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
31884 specify an &"unseen"& (non-significant) delivery, and that delivery does not
31885 succeed, it will not be tried again.
31886 If you want Exim to retry an unseen delivery until it succeeds, you should
31887 arrange to set it up every time the filter runs.
31889 When a system filter finishes running, the values of the variables &$n0$& &--
31890 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
31891 users' filter files. Thus a system filter can, for example, set up &"scores"&
31892 to which users' filter files can refer.
31896 .section "Additional variable for system filters" "SECID215"
31897 .vindex "&$recipients$&"
31898 The expansion variable &$recipients$&, containing a list of all the recipients
31899 of the message (separated by commas and white space), is available in system
31900 filters. It is not available in users' filters for privacy reasons.
31904 .section "Defer, freeze, and fail commands for system filters" "SECID216"
31905 .cindex "freezing messages"
31906 .cindex "message" "freezing"
31907 .cindex "message" "forced failure"
31908 .cindex "&%fail%&" "in system filter"
31909 .cindex "&%freeze%& in system filter"
31910 .cindex "&%defer%& in system filter"
31911 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
31912 always available in system filters, but are not normally enabled in users'
31913 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
31914 for the &(redirect)& router.) These commands can optionally be followed by the
31915 word &%text%& and a string containing an error message, for example:
31917 fail text "this message looks like spam to me"
31919 The keyword &%text%& is optional if the next character is a double quote.
31921 The &%defer%& command defers delivery of the original recipients of the
31922 message. The &%fail%& command causes all the original recipients to be failed,
31923 and a bounce message to be created. The &%freeze%& command suspends all
31924 delivery attempts for the original recipients. In all cases, any new deliveries
31925 that are specified by the filter are attempted as normal after the filter has
31928 The &%freeze%& command is ignored if the message has been manually unfrozen and
31929 not manually frozen since. This means that automatic freezing by a system
31930 filter can be used as a way of checking out suspicious messages. If a message
31931 is found to be all right, manually unfreezing it allows it to be delivered.
31933 .cindex "log" "&%fail%& command log line"
31934 .cindex "&%fail%&" "log line; reducing"
31935 The text given with a fail command is used as part of the bounce message as
31936 well as being written to the log. If the message is quite long, this can fill
31937 up a lot of log space when such failures are common. To reduce the size of the
31938 log message, Exim interprets the text in a special way if it starts with the
31939 two characters &`<<`& and contains &`>>`& later. The text between these two
31940 strings is written to the log, and the rest of the text is used in the bounce
31941 message. For example:
31943 fail "<<filter test 1>>Your message is rejected \
31944 because it contains attachments that we are \
31945 not prepared to receive."
31948 .cindex "loop" "caused by &%fail%&"
31949 Take great care with the &%fail%& command when basing the decision to fail on
31950 the contents of the message, because the bounce message will of course include
31951 the contents of the original message and will therefore trigger the &%fail%&
31952 command again (causing a mail loop) unless steps are taken to prevent this.
31953 Testing the &%error_message%& condition is one way to prevent this. You could
31956 if $message_body contains "this is spam" and not error_message
31957 then fail text "spam is not wanted here" endif
31959 though of course that might let through unwanted bounce messages. The
31960 alternative is clever checking of the body and/or headers to detect bounces
31961 generated by the filter.
31963 The interpretation of a system filter file ceases after a
31965 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
31966 set up earlier in the filter file are honoured, so you can use a sequence such
31972 to send a specified message when the system filter is freezing (or deferring or
31973 failing) a message. The normal deliveries for the message do not, of course,
31978 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
31979 .cindex "header lines" "adding; in system filter"
31980 .cindex "header lines" "removing; in system filter"
31981 .cindex "filter" "header lines; adding/removing"
31982 Two filter commands that are available only in system filters are:
31984 headers add <string>
31985 headers remove <string>
31987 The argument for the &%headers add%& is a string that is expanded and then
31988 added to the end of the message's headers. It is the responsibility of the
31989 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
31990 space is ignored, and if the string is otherwise empty, or if the expansion is
31991 forced to fail, the command has no effect.
31993 You can use &"\n"& within the string, followed by white space, to specify
31994 continued header lines. More than one header may be added in one command by
31995 including &"\n"& within the string without any following white space. For
31998 headers add "X-header-1: ....\n \
31999 continuation of X-header-1 ...\n\
32002 Note that the header line continuation white space after the first newline must
32003 be placed before the backslash that continues the input string, because white
32004 space after input continuations is ignored.
32006 The argument for &%headers remove%& is a colon-separated list of header names.
32007 This command applies only to those headers that are stored with the message;
32008 those that are added at delivery time (such as &'Envelope-To:'& and
32009 &'Return-Path:'&) cannot be removed by this means. If there is more than one
32010 header with the same name, they are all removed.
32012 The &%headers%& command in a system filter makes an immediate change to the set
32013 of header lines that was received with the message (with possible additions
32014 from ACL processing). Subsequent commands in the system filter operate on the
32015 modified set, which also forms the basis for subsequent message delivery.
32016 Unless further modified during routing or transporting, this set of headers is
32017 used for all recipients of the message.
32019 During routing and transporting, the variables that refer to the contents of
32020 header lines refer only to those lines that are in this set. Thus, header lines
32021 that are added by a system filter are visible to users' filter files and to all
32022 routers and transports. This contrasts with the manipulation of header lines by
32023 routers and transports, which is not immediate, but which instead is saved up
32024 until the message is actually being written (see section
32025 &<<SECTheadersaddrem>>&).
32027 If the message is not delivered at the first attempt, header lines that were
32028 added by the system filter are stored with the message, and so are still
32029 present at the next delivery attempt. Header lines that were removed are still
32030 present, but marked &"deleted"& so that they are not transported with the
32031 message. For this reason, it is usual to make the &%headers%& command
32032 conditional on &%first_delivery%& so that the set of header lines is not
32033 modified more than once.
32035 Because header modification in a system filter acts immediately, you have to
32036 use an indirect approach if you want to modify the contents of a header line.
32039 headers add "Old-Subject: $h_subject:"
32040 headers remove "Subject"
32041 headers add "Subject: new subject (was: $h_old-subject:)"
32042 headers remove "Old-Subject"
32047 .section "Setting an errors address in a system filter" "SECID217"
32048 .cindex "envelope sender"
32049 In a system filter, if a &%deliver%& command is followed by
32051 errors_to <some address>
32053 in order to change the envelope sender (and hence the error reporting) for that
32054 delivery, any address may be specified. (In a user filter, only the current
32055 user's address can be set.) For example, if some mail is being monitored, you
32058 unseen deliver monitor@spying.example errors_to root@local.example
32060 to take a copy which would not be sent back to the normal error reporting
32061 address if its delivery failed.
32065 .section "Per-address filtering" "SECTperaddfil"
32066 .vindex "&$domain$&"
32067 .vindex "&$local_part$&"
32068 In contrast to the system filter, which is run just once per message for each
32069 delivery attempt, it is also possible to set up a system-wide filtering
32070 operation that runs once for each recipient address. In this case, variables
32071 such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
32072 filter file could be made dependent on them. This is an example of a router
32073 which implements such a filter:
32078 domains = +local_domains
32079 file = /central/filters/$local_part
32084 The filter is run in a separate process under its own uid. Therefore, either
32085 &%check_local_user%& must be set (as above), in which case the filter is run as
32086 the local user, or the &%user%& option must be used to specify which user to
32087 use. If both are set, &%user%& overrides.
32089 Care should be taken to ensure that none of the commands in the filter file
32090 specify a significant delivery if the message is to go on to be delivered to
32091 its intended recipient. The router will not then claim to have dealt with the
32092 address, so it will be passed on to subsequent routers to be delivered in the
32094 .ecindex IIDsysfil1
32095 .ecindex IIDsysfil2
32096 .ecindex IIDsysfil3
32103 . ////////////////////////////////////////////////////////////////////////////
32104 . ////////////////////////////////////////////////////////////////////////////
32106 .chapter "Message processing" "CHAPmsgproc"
32107 .scindex IIDmesproc "message" "general processing"
32108 Exim performs various transformations on the sender and recipient addresses of
32109 all messages that it handles, and also on the messages' header lines. Some of
32110 these are optional and configurable, while others always take place. All of
32111 this processing, except rewriting as a result of routing, and the addition or
32112 removal of header lines while delivering, happens when a message is received,
32113 before it is placed on Exim's queue.
32115 Some of the automatic processing takes place by default only for
32116 &"locally-originated"& messages. This adjective is used to describe messages
32117 that are not received over TCP/IP, but instead are passed to an Exim process on
32118 its standard input. This includes the interactive &"local SMTP"& case that is
32119 set up by the &%-bs%& command line option.
32121 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
32122 or ::1) are not considered to be locally-originated. Exim does not treat the
32123 loopback interface specially in any way.
32125 If you want the loopback interface to be treated specially, you must ensure
32126 that there are appropriate entries in your ACLs.
32131 .section "Submission mode for non-local messages" "SECTsubmodnon"
32132 .cindex "message" "submission"
32133 .cindex "submission mode"
32134 Processing that happens automatically for locally-originated messages (unless
32135 &%suppress_local_fixups%& is set) can also be requested for messages that are
32136 received over TCP/IP. The term &"submission mode"& is used to describe this
32137 state. Submission mode is set by the modifier
32139 control = submission
32141 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
32142 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
32143 a local submission, and is normally used when the source of the message is
32144 known to be an MUA running on a client host (as opposed to an MTA). For
32145 example, to set submission mode for messages originating on the IPv4 loopback
32146 interface, you could include the following in the MAIL ACL:
32148 warn hosts = 127.0.0.1
32149 control = submission
32151 .cindex "&%sender_retain%& submission option"
32152 There are some options that can be used when setting submission mode. A slash
32153 is used to separate options. For example:
32155 control = submission/sender_retain
32157 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
32158 true and &%local_from_check%& false for the current incoming message. The first
32159 of these allows an existing &'Sender:'& header in the message to remain, and
32160 the second suppresses the check to ensure that &'From:'& matches the
32161 authenticated sender. With this setting, Exim still fixes up messages by adding
32162 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
32163 attempt to check sender authenticity in header lines.
32165 When &%sender_retain%& is not set, a submission mode setting may specify a
32166 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
32169 control = submission/domain=some.domain
32171 The domain may be empty. How this value is used is described in sections
32172 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
32173 that allows you to specify the user's full name for inclusion in a created
32174 &'Sender:'& or &'From:'& header line. For example:
32176 accept authenticated = *
32177 control = submission/domain=wonderland.example/\
32178 name=${lookup {$authenticated_id} \
32179 lsearch {/etc/exim/namelist}}
32181 Because the name may contain any characters, including slashes, the &%name%&
32182 option must be given last. The remainder of the string is used as the name. For
32183 the example above, if &_/etc/exim/namelist_& contains:
32185 bigegg: Humpty Dumpty
32187 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
32190 Sender: Humpty Dumpty <bigegg@wonderland.example>
32192 .cindex "return path" "in submission mode"
32193 By default, submission mode forces the return path to the same address as is
32194 used to create the &'Sender:'& header. However, if &%sender_retain%& is
32195 specified, the return path is also left unchanged.
32197 &*Note*&: The changes caused by submission mode take effect after the predata
32198 ACL. This means that any sender checks performed before the fix-ups use the
32199 untrusted sender address specified by the user, not the trusted sender address
32200 specified by submission mode. Although this might be slightly unexpected, it
32201 does mean that you can configure ACL checks to spot that a user is trying to
32202 spoof another's address.
32204 .section "Line endings" "SECTlineendings"
32205 .cindex "line endings"
32206 .cindex "carriage return"
32208 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
32209 linefeed) is the line ending for messages transmitted over the Internet using
32210 SMTP over TCP/IP. However, within individual operating systems, different
32211 conventions are used. For example, Unix-like systems use just LF, but others
32212 use CRLF or just CR.
32214 Exim was designed for Unix-like systems, and internally, it stores messages
32215 using the system's convention of a single LF as a line terminator. When
32216 receiving a message, all line endings are translated to this standard format.
32217 Originally, it was thought that programs that passed messages directly to an
32218 MTA within an operating system would use that system's convention. Experience
32219 has shown that this is not the case; for example, there are Unix applications
32220 that use CRLF in this circumstance. For this reason, and for compatibility with
32221 other MTAs, the way Exim handles line endings for all messages is now as
32225 LF not preceded by CR is treated as a line ending.
32227 CR is treated as a line ending; if it is immediately followed by LF, the LF
32230 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
32231 nor a local message in the state where a line containing only a dot is a
32234 If a bare CR is encountered within a header line, an extra space is added after
32235 the line terminator so as not to end the header line. The reasoning behind this
32236 is that bare CRs in header lines are most likely either to be mistakes, or
32237 people trying to play silly games.
32239 If the first header line received in a message ends with CRLF, a subsequent
32240 bare LF in a header line is treated in the same way as a bare CR in a header
32248 .section "Unqualified addresses" "SECID218"
32249 .cindex "unqualified addresses"
32250 .cindex "address" "qualification"
32251 By default, Exim expects every envelope address it receives from an external
32252 host to be fully qualified. Unqualified addresses cause negative responses to
32253 SMTP commands. However, because SMTP is used as a means of transporting
32254 messages from MUAs running on personal workstations, there is sometimes a
32255 requirement to accept unqualified addresses from specific hosts or IP networks.
32257 Exim has two options that separately control which hosts may send unqualified
32258 sender or recipient addresses in SMTP commands, namely
32259 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
32260 cases, if an unqualified address is accepted, it is qualified by adding the
32261 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
32263 .oindex "&%qualify_domain%&"
32264 .oindex "&%qualify_recipient%&"
32265 Unqualified addresses in header lines are automatically qualified for messages
32266 that are locally originated, unless the &%-bnq%& option is given on the command
32267 line. For messages received over SMTP, unqualified addresses in header lines
32268 are qualified only if unqualified addresses are permitted in SMTP commands. In
32269 other words, such qualification is also controlled by
32270 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
32275 .section "The UUCP From line" "SECID219"
32276 .cindex "&""From""& line"
32277 .cindex "UUCP" "&""From""& line"
32278 .cindex "sender" "address"
32279 .oindex "&%uucp_from_pattern%&"
32280 .oindex "&%uucp_from_sender%&"
32281 .cindex "envelope sender"
32282 .cindex "Sendmail compatibility" "&""From""& line"
32283 Messages that have come from UUCP (and some other applications) often begin
32284 with a line containing the envelope sender and a timestamp, following the word
32285 &"From"&. Examples of two common formats are:
32287 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
32288 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
32290 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
32291 Exim recognizes such lines at the start of messages that are submitted to it
32292 via the command line (that is, on the standard input). It does not recognize
32293 such lines in incoming SMTP messages, unless the sending host matches
32294 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
32295 and &%ignore_fromline_local%& is set. The recognition is controlled by a
32296 regular expression that is defined by the &%uucp_from_pattern%& option, whose
32297 default value matches the two common cases shown above and puts the address
32298 that follows &"From"& into &$1$&.
32300 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
32301 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
32302 a trusted user, the message's sender address is constructed by expanding the
32303 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
32304 then parsed as an RFC 2822 address. If there is no domain, the local part is
32305 qualified with &%qualify_domain%& unless it is the empty string. However, if
32306 the command line &%-f%& option is used, it overrides the &"From"& line.
32308 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
32309 sender address is not changed. This is also the case for incoming SMTP messages
32310 that are permitted to contain &"From"& lines.
32312 Only one &"From"& line is recognized. If there is more than one, the second is
32313 treated as a data line that starts the body of the message, as it is not valid
32314 as a header line. This also happens if a &"From"& line is present in an
32315 incoming SMTP message from a source that is not permitted to send them.
32319 .section "Resent- header lines" "SECID220"
32320 .cindex "&%Resent-%& header lines"
32321 RFC 2822 makes provision for sets of header lines starting with the string
32322 &`Resent-`& to be added to a message when it is resent by the original
32323 recipient to somebody else. These headers are &'Resent-Date:'&,
32324 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
32325 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
32328 &'Resent fields are strictly informational. They MUST NOT be used in the normal
32329 processing of replies or other such automatic actions on messages.'&
32332 This leaves things a bit vague as far as other processing actions such as
32333 address rewriting are concerned. Exim treats &%Resent-%& header lines as
32337 A &'Resent-From:'& line that just contains the login id of the submitting user
32338 is automatically rewritten in the same way as &'From:'& (see below).
32340 If there's a rewriting rule for a particular header line, it is also applied to
32341 &%Resent-%& header lines of the same type. For example, a rule that rewrites
32342 &'From:'& also rewrites &'Resent-From:'&.
32344 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
32347 For a locally-submitted message,
32348 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
32349 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
32350 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
32351 included in log lines in this case.
32353 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
32354 &%Resent-%& header lines are present.
32360 .section "The Auto-Submitted: header line" "SECID221"
32361 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
32362 includes the header line:
32364 Auto-Submitted: auto-replied
32367 .section "The Bcc: header line" "SECID222"
32368 .cindex "&'Bcc:'& header line"
32369 If Exim is called with the &%-t%& option, to take recipient addresses from a
32370 message's header, it removes any &'Bcc:'& header line that may exist (after
32371 extracting its addresses). If &%-t%& is not present on the command line, any
32372 existing &'Bcc:'& is not removed.
32375 .section "The Date: header line" "SECID223"
32376 .cindex "&'Date:'& header line"
32377 If a locally-generated or submission-mode message has no &'Date:'& header line,
32378 Exim adds one, using the current date and time, unless the
32379 &%suppress_local_fixups%& control has been specified.
32381 .section "The Delivery-date: header line" "SECID224"
32382 .cindex "&'Delivery-date:'& header line"
32383 .oindex "&%delivery_date_remove%&"
32384 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
32385 set. Exim can be configured to add them to the final delivery of messages. (See
32386 the generic &%delivery_date_add%& transport option.) They should not be present
32387 in messages in transit. If the &%delivery_date_remove%& configuration option is
32388 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
32392 .section "The Envelope-to: header line" "SECID225"
32393 .cindex "&'Envelope-to:'& header line"
32394 .oindex "&%envelope_to_remove%&"
32395 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
32396 Exim can be configured to add them to the final delivery of messages. (See the
32397 generic &%envelope_to_add%& transport option.) They should not be present in
32398 messages in transit. If the &%envelope_to_remove%& configuration option is set
32399 (the default), Exim removes &'Envelope-to:'& header lines from incoming
32403 .section "The From: header line" "SECTthefrohea"
32404 .cindex "&'From:'& header line"
32405 .cindex "Sendmail compatibility" "&""From""& line"
32406 .cindex "message" "submission"
32407 .cindex "submission mode"
32408 If a submission-mode message does not contain a &'From:'& header line, Exim
32409 adds one if either of the following conditions is true:
32412 The envelope sender address is not empty (that is, this is not a bounce
32413 message). The added header line copies the envelope sender address.
32415 .vindex "&$authenticated_id$&"
32416 The SMTP session is authenticated and &$authenticated_id$& is not empty.
32418 .vindex "&$qualify_domain$&"
32419 If no domain is specified by the submission control, the local part is
32420 &$authenticated_id$& and the domain is &$qualify_domain$&.
32422 If a non-empty domain is specified by the submission control, the local
32423 part is &$authenticated_id$&, and the domain is the specified domain.
32425 If an empty domain is specified by the submission control,
32426 &$authenticated_id$& is assumed to be the complete address.
32430 A non-empty envelope sender takes precedence.
32432 If a locally-generated incoming message does not contain a &'From:'& header
32433 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
32434 containing the sender's address. The calling user's login name and full name
32435 are used to construct the address, as described in section &<<SECTconstr>>&.
32436 They are obtained from the password data by calling &[getpwuid()]& (but see the
32437 &%unknown_login%& configuration option). The address is qualified with
32438 &%qualify_domain%&.
32440 For compatibility with Sendmail, if an incoming, non-SMTP message has a
32441 &'From:'& header line containing just the unqualified login name of the calling
32442 user, this is replaced by an address containing the user's login name and full
32443 name as described in section &<<SECTconstr>>&.
32446 .section "The Message-ID: header line" "SECID226"
32447 .cindex "&'Message-ID:'& header line"
32448 .cindex "message" "submission"
32449 .oindex "&%message_id_header_text%&"
32450 If a locally-generated or submission-mode incoming message does not contain a
32451 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
32452 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
32453 to the message. If there are any &'Resent-:'& headers in the message, it
32454 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
32455 message id, preceded by the letter E to ensure it starts with a letter, and
32456 followed by @ and the primary host name. Additional information can be included
32457 in this header line by setting the &%message_id_header_text%& and/or
32458 &%message_id_header_domain%& options.
32461 .section "The Received: header line" "SECID227"
32462 .cindex "&'Received:'& header line"
32463 A &'Received:'& header line is added at the start of every message. The
32464 contents are defined by the &%received_header_text%& configuration option, and
32465 Exim automatically adds a semicolon and a timestamp to the configured string.
32467 The &'Received:'& header is generated as soon as the message's header lines
32468 have been received. At this stage, the timestamp in the &'Received:'& header
32469 line is the time that the message started to be received. This is the value
32470 that is seen by the DATA ACL and by the &[local_scan()]& function.
32472 Once a message is accepted, the timestamp in the &'Received:'& header line is
32473 changed to the time of acceptance, which is (apart from a small delay while the
32474 -H spool file is written) the earliest time at which delivery could start.
32477 .section "The References: header line" "SECID228"
32478 .cindex "&'References:'& header line"
32479 Messages created by the &(autoreply)& transport include a &'References:'&
32480 header line. This is constructed according to the rules that are described in
32481 section 3.64 of RFC 2822 (which states that replies should contain such a
32482 header line), and section 3.14 of RFC 3834 (which states that automatic
32483 responses are not different in this respect). However, because some mail
32484 processing software does not cope well with very long header lines, no more
32485 than 12 message IDs are copied from the &'References:'& header line in the
32486 incoming message. If there are more than 12, the first one and then the final
32487 11 are copied, before adding the message ID of the incoming message.
32491 .section "The Return-path: header line" "SECID229"
32492 .cindex "&'Return-path:'& header line"
32493 .oindex "&%return_path_remove%&"
32494 &'Return-path:'& header lines are defined as something an MTA may insert when
32495 it does the final delivery of messages. (See the generic &%return_path_add%&
32496 transport option.) Therefore, they should not be present in messages in
32497 transit. If the &%return_path_remove%& configuration option is set (the
32498 default), Exim removes &'Return-path:'& header lines from incoming messages.
32502 .section "The Sender: header line" "SECTthesenhea"
32503 .cindex "&'Sender:'& header line"
32504 .cindex "message" "submission"
32505 For a locally-originated message from an untrusted user, Exim may remove an
32506 existing &'Sender:'& header line, and it may add a new one. You can modify
32507 these actions by setting the &%local_sender_retain%& option true, the
32508 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
32511 When a local message is received from an untrusted user and
32512 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
32513 control has not been set, a check is made to see if the address given in the
32514 &'From:'& header line is the correct (local) sender of the message. The address
32515 that is expected has the login name as the local part and the value of
32516 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
32517 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
32518 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
32519 line is added to the message.
32521 If you set &%local_from_check%& false, this checking does not occur. However,
32522 the removal of an existing &'Sender:'& line still happens, unless you also set
32523 &%local_sender_retain%& to be true. It is not possible to set both of these
32524 options true at the same time.
32526 .cindex "submission mode"
32527 By default, no processing of &'Sender:'& header lines is done for messages
32528 received over TCP/IP or for messages submitted by trusted users. However, when
32529 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
32530 not specified on the submission control, the following processing takes place:
32532 .vindex "&$authenticated_id$&"
32533 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
32534 authenticated, and &$authenticated_id$& is not empty, a sender address is
32535 created as follows:
32538 .vindex "&$qualify_domain$&"
32539 If no domain is specified by the submission control, the local part is
32540 &$authenticated_id$& and the domain is &$qualify_domain$&.
32542 If a non-empty domain is specified by the submission control, the local part
32543 is &$authenticated_id$&, and the domain is the specified domain.
32545 If an empty domain is specified by the submission control,
32546 &$authenticated_id$& is assumed to be the complete address.
32549 This address is compared with the address in the &'From:'& header line. If they
32550 are different, a &'Sender:'& header line containing the created address is
32551 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
32552 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
32554 .cindex "return path" "created from &'Sender:'&"
32555 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
32556 the message (the envelope sender address) is changed to be the same address,
32557 except in the case of submission mode when &%sender_retain%& is specified.
32561 .section "Adding and removing header lines in routers and transports" &&&
32562 "SECTheadersaddrem"
32563 .cindex "header lines" "adding; in router or transport"
32564 .cindex "header lines" "removing; in router or transport"
32565 When a message is delivered, the addition and removal of header lines can be
32566 specified in a system filter, or on any of the routers and transports that
32567 process the message. Section &<<SECTaddremheasys>>& contains details about
32568 modifying headers in a system filter. Header lines can also be added in an ACL
32569 as a message is received (see section &<<SECTaddheadacl>>&).
32571 In contrast to what happens in a system filter, header modifications that are
32572 specified on routers and transports apply only to the particular recipient
32573 addresses that are being processed by those routers and transports. These
32574 changes do not actually take place until a copy of the message is being
32575 transported. Therefore, they do not affect the basic set of header lines, and
32576 they do not affect the values of the variables that refer to header lines.
32578 &*Note*&: In particular, this means that any expansions in the configuration of
32579 the transport cannot refer to the modified header lines, because such
32580 expansions all occur before the message is actually transported.
32582 For both routers and transports, the argument of a &%headers_add%&
32583 option must be in the form of one or more RFC 2822 header lines, separated by
32584 newlines (coded as &"\n"&). For example:
32586 headers_add = X-added-header: added by $primary_hostname\n\
32587 X-added-second: another added header line
32589 Exim does not check the syntax of these added header lines.
32591 Multiple &%headers_add%& options for a single router or transport can be
32592 specified; the values will append to a single list of header lines.
32593 Each header-line is separately expanded.
32595 The argument of a &%headers_remove%& option must consist of a colon-separated
32596 list of header names. This is confusing, because header names themselves are
32597 often terminated by colons. In this case, the colons are the list separators,
32598 not part of the names. For example:
32600 headers_remove = return-receipt-to:acknowledge-to
32603 Multiple &%headers_remove%& options for a single router or transport can be
32604 specified; the arguments will append to a single header-names list.
32605 Each item is separately expanded.
32606 Note that colons in complex expansions which are used to
32607 form all or part of a &%headers_remove%& list
32608 will act as list separators.
32610 When &%headers_add%& or &%headers_remove%& is specified on a router,
32611 items are expanded at routing time,
32612 and then associated with all addresses that are
32613 accepted by that router, and also with any new addresses that it generates. If
32614 an address passes through several routers as a result of aliasing or
32615 forwarding, the changes are cumulative.
32617 .oindex "&%unseen%&"
32618 However, this does not apply to multiple routers that result from the use of
32619 the &%unseen%& option. Any header modifications that were specified by the
32620 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
32622 Addresses that end up with different &%headers_add%& or &%headers_remove%&
32623 settings cannot be delivered together in a batch, so a transport is always
32624 dealing with a set of addresses that have the same header-processing
32627 The transport starts by writing the original set of header lines that arrived
32628 with the message, possibly modified by the system filter. As it writes out
32629 these lines, it consults the list of header names that were attached to the
32630 recipient address(es) by &%headers_remove%& options in routers, and it also
32631 consults the transport's own &%headers_remove%& option. Header lines whose
32632 names are on either of these lists are not written out. If there are multiple
32633 instances of any listed header, they are all skipped.
32635 After the remaining original header lines have been written, new header
32636 lines that were specified by routers' &%headers_add%& options are written, in
32637 the order in which they were attached to the address. These are followed by any
32638 header lines specified by the transport's &%headers_add%& option.
32640 This way of handling header line modifications in routers and transports has
32641 the following consequences:
32644 The original set of header lines, possibly modified by the system filter,
32645 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
32646 to it, at all times.
32648 Header lines that are added by a router's
32649 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
32650 expansion syntax in subsequent routers or the transport.
32652 Conversely, header lines that are specified for removal by &%headers_remove%&
32653 in a router remain visible to subsequent routers and the transport.
32655 Headers added to an address by &%headers_add%& in a router cannot be removed by
32656 a later router or by a transport.
32658 An added header can refer to the contents of an original header that is to be
32659 removed, even it has the same name as the added header. For example:
32661 headers_remove = subject
32662 headers_add = Subject: new subject (was: $h_subject:)
32666 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
32667 for a &(redirect)& router that has the &%one_time%& option set.
32673 .section "Constructed addresses" "SECTconstr"
32674 .cindex "address" "constructed"
32675 .cindex "constructed address"
32676 When Exim constructs a sender address for a locally-generated message, it uses
32679 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
32683 Zaphod Beeblebrox <zaphod@end.univ.example>
32685 The user name is obtained from the &%-F%& command line option if set, or
32686 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
32687 &"gecos"& field from the password entry. If the &"gecos"& field contains an
32688 ampersand character, this is replaced by the login name with the first letter
32689 upper cased, as is conventional in a number of operating systems. See the
32690 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
32691 The &%unknown_username%& option can be used to specify user names in cases when
32692 there is no password file entry.
32695 In all cases, the user name is made to conform to RFC 2822 by quoting all or
32696 parts of it if necessary. In addition, if it contains any non-printing
32697 characters, it is encoded as described in RFC 2047, which defines a way of
32698 including non-ASCII characters in header lines. The value of the
32699 &%headers_charset%& option specifies the name of the encoding that is used (the
32700 characters are assumed to be in this encoding). The setting of
32701 &%print_topbitchars%& controls whether characters with the top bit set (that
32702 is, with codes greater than 127) count as printing characters or not.
32706 .section "Case of local parts" "SECID230"
32707 .cindex "case of local parts"
32708 .cindex "local part" "case of"
32709 RFC 2822 states that the case of letters in the local parts of addresses cannot
32710 be assumed to be non-significant. Exim preserves the case of local parts of
32711 addresses, but by default it uses a lower-cased form when it is routing,
32712 because on most Unix systems, usernames are in lower case and case-insensitive
32713 routing is required. However, any particular router can be made to use the
32714 original case for local parts by setting the &%caseful_local_part%& generic
32717 .cindex "mixed-case login names"
32718 If you must have mixed-case user names on your system, the best way to proceed,
32719 assuming you want case-independent handling of incoming email, is to set up
32720 your first router to convert incoming local parts in your domains to the
32721 correct case by means of a file lookup. For example:
32725 domains = +local_domains
32726 data = ${lookup{$local_part}cdb\
32727 {/etc/usercased.cdb}{$value}fail}\
32730 For this router, the local part is forced to lower case by the default action
32731 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
32732 up a new local part in the correct case. If you then set &%caseful_local_part%&
32733 on any subsequent routers which process your domains, they will operate on
32734 local parts with the correct case in a case-sensitive manner.
32738 .section "Dots in local parts" "SECID231"
32739 .cindex "dot" "in local part"
32740 .cindex "local part" "dots in"
32741 RFC 2822 forbids empty components in local parts. That is, an unquoted local
32742 part may not begin or end with a dot, nor have two consecutive dots in the
32743 middle. However, it seems that many MTAs do not enforce this, so Exim permits
32744 empty components for compatibility.
32748 .section "Rewriting addresses" "SECID232"
32749 .cindex "rewriting" "addresses"
32750 Rewriting of sender and recipient addresses, and addresses in headers, can
32751 happen automatically, or as the result of configuration options, as described
32752 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
32753 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
32755 Automatic rewriting includes qualification, as mentioned above. The other case
32756 in which it can happen is when an incomplete non-local domain is given. The
32757 routing process may cause this to be expanded into the full domain name. For
32758 example, a header such as
32762 might get rewritten as
32764 To: hare@teaparty.wonderland.fict.example
32766 Rewriting as a result of routing is the one kind of message processing that
32767 does not happen at input time, as it cannot be done until the address has
32770 Strictly, one should not do &'any'& deliveries of a message until all its
32771 addresses have been routed, in case any of the headers get changed as a
32772 result of routing. However, doing this in practice would hold up many
32773 deliveries for unreasonable amounts of time, just because one address could not
32774 immediately be routed. Exim therefore does not delay other deliveries when
32775 routing of one or more addresses is deferred.
32776 .ecindex IIDmesproc
32780 . ////////////////////////////////////////////////////////////////////////////
32781 . ////////////////////////////////////////////////////////////////////////////
32783 .chapter "SMTP processing" "CHAPSMTP"
32784 .scindex IIDsmtpproc1 "SMTP" "processing details"
32785 .scindex IIDsmtpproc2 "LMTP" "processing details"
32786 Exim supports a number of different ways of using the SMTP protocol, and its
32787 LMTP variant, which is an interactive protocol for transferring messages into a
32788 closed mail store application. This chapter contains details of how SMTP is
32789 processed. For incoming mail, the following are available:
32792 SMTP over TCP/IP (Exim daemon or &'inetd'&);
32794 SMTP over the standard input and output (the &%-bs%& option);
32796 Batched SMTP on the standard input (the &%-bS%& option).
32799 For mail delivery, the following are available:
32802 SMTP over TCP/IP (the &(smtp)& transport);
32804 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
32807 LMTP over a pipe to a process running in the local host (the &(lmtp)&
32810 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
32811 the &%use_bsmtp%& option set).
32814 &'Batched SMTP'& is the name for a process in which batches of messages are
32815 stored in or read from files (or pipes), in a format in which SMTP commands are
32816 used to contain the envelope information.
32820 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
32821 .cindex "SMTP" "outgoing over TCP/IP"
32822 .cindex "outgoing SMTP over TCP/IP"
32823 .cindex "LMTP" "over TCP/IP"
32824 .cindex "outgoing LMTP over TCP/IP"
32827 .cindex "SIZE option on MAIL command"
32828 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
32829 The &%protocol%& option selects which protocol is to be used, but the actual
32830 processing is the same in both cases.
32832 If, in response to its EHLO command, Exim is told that the SIZE
32833 parameter is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
32834 command. The value of <&'n'&> is the message size plus the value of the
32835 &%size_addition%& option (default 1024) to allow for additions to the message
32836 such as per-transport header lines, or changes made in a
32837 .cindex "transport" "filter"
32838 .cindex "filter" "transport filter"
32839 transport filter. If &%size_addition%& is set negative, the use of SIZE is
32842 If the remote server advertises support for PIPELINING, Exim uses the
32843 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
32844 required for the transaction.
32846 If the remote server advertises support for the STARTTLS command, and Exim
32847 was built to support TLS encryption, it tries to start a TLS session unless the
32848 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
32849 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
32850 is called for verification.
32852 If the remote server advertises support for the AUTH command, Exim scans
32853 the authenticators configuration for any suitable client settings, as described
32854 in chapter &<<CHAPSMTPAUTH>>&.
32856 .cindex "carriage return"
32858 Responses from the remote host are supposed to be terminated by CR followed by
32859 LF. However, there are known to be hosts that do not send CR characters, so in
32860 order to be able to interwork with such hosts, Exim treats LF on its own as a
32863 If a message contains a number of different addresses, all those with the same
32864 characteristics (for example, the same envelope sender) that resolve to the
32865 same set of hosts, in the same order, are sent in a single SMTP transaction,
32866 even if they are for different domains, unless there are more than the setting
32867 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
32868 they are split into groups containing no more than &%max_rcpt%&s addresses
32869 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
32870 in parallel sessions. The order of hosts with identical MX values is not
32871 significant when checking whether addresses can be batched in this way.
32873 When the &(smtp)& transport suffers a temporary failure that is not
32874 message-related, Exim updates its transport-specific database, which contains
32875 records indexed by host name that remember which messages are waiting for each
32876 particular host. It also updates the retry database with new retry times.
32878 .cindex "hints database" "retry keys"
32879 Exim's retry hints are based on host name plus IP address, so if one address of
32880 a multi-homed host is broken, it will soon be skipped most of the time.
32881 See the next section for more detail about error handling.
32883 .cindex "SMTP" "passed connection"
32884 .cindex "SMTP" "batching over TCP/IP"
32885 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
32886 looks in the hints database for the transport to see if there are any queued
32887 messages waiting for the host to which it is connected. If it finds one, it
32888 creates a new Exim process using the &%-MC%& option (which can only be used by
32889 a process running as root or the Exim user) and passes the TCP/IP socket to it
32890 so that it can deliver another message using the same socket. The new process
32891 does only those deliveries that are routed to the connected host, and may in
32892 turn pass the socket on to a third process, and so on.
32894 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
32895 limit the number of messages sent down a single TCP/IP connection.
32897 .cindex "asterisk" "after IP address"
32898 The second and subsequent messages delivered down an existing connection are
32899 identified in the main log by the addition of an asterisk after the closing
32900 square bracket of the IP address.
32905 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
32906 .cindex "error" "in outgoing SMTP"
32907 .cindex "SMTP" "errors in outgoing"
32908 .cindex "host" "error"
32909 Three different kinds of error are recognized for outgoing SMTP: host errors,
32910 message errors, and recipient errors.
32913 .vitem "&*Host errors*&"
32914 A host error is not associated with a particular message or with a
32915 particular recipient of a message. The host errors are:
32918 Connection refused or timed out,
32920 Any error response code on connection,
32922 Any error response code to EHLO or HELO,
32924 Loss of connection at any time, except after &"."&,
32926 I/O errors at any time,
32928 Timeouts during the session, other than in response to MAIL, RCPT or
32929 the &"."& at the end of the data.
32932 For a host error, a permanent error response on connection, or in response to
32933 EHLO, causes all addresses routed to the host to be failed. Any other host
32934 error causes all addresses to be deferred, and retry data to be created for the
32935 host. It is not tried again, for any message, until its retry time arrives. If
32936 the current set of addresses are not all delivered in this run (to some
32937 alternative host), the message is added to the list of those waiting for this
32938 host, so if it is still undelivered when a subsequent successful delivery is
32939 made to the host, it will be sent down the same SMTP connection.
32941 .vitem "&*Message errors*&"
32942 .cindex "message" "error"
32943 A message error is associated with a particular message when sent to a
32944 particular host, but not with a particular recipient of the message. The
32945 message errors are:
32948 Any error response code to MAIL, DATA, or the &"."& that terminates
32951 Timeout after MAIL,
32953 Timeout or loss of connection after the &"."& that terminates the data. A
32954 timeout after the DATA command itself is treated as a host error, as is loss of
32955 connection at any other time.
32958 For a message error, a permanent error response (5&'xx'&) causes all addresses
32959 to be failed, and a delivery error report to be returned to the sender. A
32960 temporary error response (4&'xx'&), or one of the timeouts, causes all
32961 addresses to be deferred. Retry data is not created for the host, but instead,
32962 a retry record for the combination of host plus message id is created. The
32963 message is not added to the list of those waiting for this host. This ensures
32964 that the failing message will not be sent to this host again until the retry
32965 time arrives. However, other messages that are routed to the host are not
32966 affected, so if it is some property of the message that is causing the error,
32967 it will not stop the delivery of other mail.
32969 If the remote host specified support for the SIZE parameter in its response
32970 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
32971 over-large message will cause a message error because the error arrives as a
32974 .vitem "&*Recipient errors*&"
32975 .cindex "recipient" "error"
32976 A recipient error is associated with a particular recipient of a message. The
32977 recipient errors are:
32980 Any error response to RCPT,
32982 Timeout after RCPT.
32985 For a recipient error, a permanent error response (5&'xx'&) causes the
32986 recipient address to be failed, and a bounce message to be returned to the
32987 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
32988 address to be deferred, and routing retry data to be created for it. This is
32989 used to delay processing of the address in subsequent queue runs, until its
32990 routing retry time arrives. This applies to all messages, but because it
32991 operates only in queue runs, one attempt will be made to deliver a new message
32992 to the failing address before the delay starts to operate. This ensures that,
32993 if the failure is really related to the message rather than the recipient
32994 (&"message too big for this recipient"& is a possible example), other messages
32995 have a chance of getting delivered. If a delivery to the address does succeed,
32996 the retry information gets cleared, so all stuck messages get tried again, and
32997 the retry clock is reset.
32999 The message is not added to the list of those waiting for this host. Use of the
33000 host for other messages is unaffected, and except in the case of a timeout,
33001 other recipients are processed independently, and may be successfully delivered
33002 in the current SMTP session. After a timeout it is of course impossible to
33003 proceed with the session, so all addresses get deferred. However, those other
33004 than the one that failed do not suffer any subsequent retry delays. Therefore,
33005 if one recipient is causing trouble, the others have a chance of getting
33006 through when a subsequent delivery attempt occurs before the failing
33007 recipient's retry time.
33010 In all cases, if there are other hosts (or IP addresses) available for the
33011 current set of addresses (for example, from multiple MX records), they are
33012 tried in this run for any undelivered addresses, subject of course to their
33013 own retry data. In other words, recipient error retry data does not take effect
33014 until the next delivery attempt.
33016 Some hosts have been observed to give temporary error responses to every
33017 MAIL command at certain times (&"insufficient space"& has been seen). It
33018 would be nice if such circumstances could be recognized, and defer data for the
33019 host itself created, but this is not possible within the current Exim design.
33020 What actually happens is that retry data for every (host, message) combination
33023 The reason that timeouts after MAIL and RCPT are treated specially is that
33024 these can sometimes arise as a result of the remote host's verification
33025 procedures. Exim makes this assumption, and treats them as if a temporary error
33026 response had been received. A timeout after &"."& is treated specially because
33027 it is known that some broken implementations fail to recognize the end of the
33028 message if the last character of the last line is a binary zero. Thus, it is
33029 helpful to treat this case as a message error.
33031 Timeouts at other times are treated as host errors, assuming a problem with the
33032 host, or the connection to it. If a timeout after MAIL, RCPT,
33033 or &"."& is really a connection problem, the assumption is that at the next try
33034 the timeout is likely to occur at some other point in the dialogue, causing it
33035 then to be treated as a host error.
33037 There is experimental evidence that some MTAs drop the connection after the
33038 terminating &"."& if they do not like the contents of the message for some
33039 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
33040 should be given. That is why Exim treats this case as a message rather than a
33041 host error, in order not to delay other messages to the same host.
33046 .section "Incoming SMTP messages over TCP/IP" "SECID233"
33047 .cindex "SMTP" "incoming over TCP/IP"
33048 .cindex "incoming SMTP over TCP/IP"
33051 Incoming SMTP messages can be accepted in one of two ways: by running a
33052 listening daemon, or by using &'inetd'&. In the latter case, the entry in
33053 &_/etc/inetd.conf_& should be like this:
33055 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
33057 Exim distinguishes between this case and the case of a locally running user
33058 agent using the &%-bs%& option by checking whether or not the standard input is
33059 a socket. When it is, either the port must be privileged (less than 1024), or
33060 the caller must be root or the Exim user. If any other user passes a socket
33061 with an unprivileged port number, Exim prints a message on the standard error
33062 stream and exits with an error code.
33064 By default, Exim does not make a log entry when a remote host connects or
33065 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
33066 unexpected. It can be made to write such log entries by setting the
33067 &%smtp_connection%& log selector.
33069 .cindex "carriage return"
33071 Commands from the remote host are supposed to be terminated by CR followed by
33072 LF. However, there are known to be hosts that do not send CR characters. In
33073 order to be able to interwork with such hosts, Exim treats LF on its own as a
33075 Furthermore, because common code is used for receiving messages from all
33076 sources, a CR on its own is also interpreted as a line terminator. However, the
33077 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
33079 .cindex "EHLO" "invalid data"
33080 .cindex "HELO" "invalid data"
33081 One area that sometimes gives rise to problems concerns the EHLO or
33082 HELO commands. Some clients send syntactically invalid versions of these
33083 commands, which Exim rejects by default. (This is nothing to do with verifying
33084 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
33085 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
33086 match the broken hosts that send invalid commands.
33088 .cindex "SIZE option on MAIL command"
33089 .cindex "MAIL" "SIZE option"
33090 The amount of disk space available is checked whenever SIZE is received on
33091 a MAIL command, independently of whether &%message_size_limit%& or
33092 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
33093 false. A temporary error is given if there is not enough space. If
33094 &%check_spool_space%& is set, the check is for that amount of space plus the
33095 value given with SIZE, that is, it checks that the addition of the incoming
33096 message will not reduce the space below the threshold.
33098 When a message is successfully received, Exim includes the local message id in
33099 its response to the final &"."& that terminates the data. If the remote host
33100 logs this text it can help with tracing what has happened to a message.
33102 The Exim daemon can limit the number of simultaneous incoming connections it is
33103 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
33104 number of simultaneous incoming connections from a single remote host (see the
33105 &%smtp_accept_max_per_host%& option). Additional connection attempts are
33106 rejected using the SMTP temporary error code 421.
33108 The Exim daemon does not rely on the SIGCHLD signal to detect when a
33109 subprocess has finished, as this can get lost at busy times. Instead, it looks
33110 for completed subprocesses every time it wakes up. Provided there are other
33111 things happening (new incoming calls, starts of queue runs), completed
33112 processes will be noticed and tidied away. On very quiet systems you may
33113 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
33114 it will be noticed when the daemon next wakes up.
33116 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
33117 and can also be set up to reject SMTP calls from non-reserved hosts at times of
33118 high system load &-- for details see the &%smtp_accept_reserve%&,
33119 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
33120 applies in both the daemon and &'inetd'& cases.
33122 Exim normally starts a delivery process for each message received, though this
33123 can be varied by means of the &%-odq%& command line option and the
33124 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
33125 number of simultaneously running delivery processes started in this way from
33126 SMTP input can be limited by the &%smtp_accept_queue%& and
33127 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
33128 subsequently received messages are just put on the input queue without starting
33129 a delivery process.
33131 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
33132 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
33133 started up from the &'inetd'& daemon, because in that case each connection is
33134 handled by an entirely independent Exim process. Control by load average is,
33135 however, available with &'inetd'&.
33137 Exim can be configured to verify addresses in incoming SMTP commands as they
33138 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
33139 to rewrite addresses at this time &-- before any syntax checking is done. See
33140 section &<<SECTrewriteS>>&.
33142 Exim can also be configured to limit the rate at which a client host submits
33143 MAIL and RCPT commands in a single SMTP session. See the
33144 &%smtp_ratelimit_hosts%& option.
33148 .section "Unrecognized SMTP commands" "SECID234"
33149 .cindex "SMTP" "unrecognized commands"
33150 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
33151 commands during a single SMTP connection, it drops the connection after sending
33152 the error response to the last command. The default value for
33153 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
33154 abuse that subvert web servers into making connections to SMTP ports; in these
33155 circumstances, a number of non-SMTP lines are sent first.
33158 .section "Syntax and protocol errors in SMTP commands" "SECID235"
33159 .cindex "SMTP" "syntax errors"
33160 .cindex "SMTP" "protocol errors"
33161 A syntax error is detected if an SMTP command is recognized, but there is
33162 something syntactically wrong with its data, for example, a malformed email
33163 address in a RCPT command. Protocol errors include invalid command
33164 sequencing such as RCPT before MAIL. If Exim receives more than
33165 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
33166 drops the connection after sending the error response to the last command. The
33167 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
33168 broken clients that loop sending bad commands (yes, it has been seen).
33172 .section "Use of non-mail SMTP commands" "SECID236"
33173 .cindex "SMTP" "non-mail commands"
33174 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
33175 DATA. Exim counts such commands, and drops the connection if there are too
33176 many of them in a single SMTP session. This action catches some
33177 denial-of-service attempts and things like repeated failing AUTHs, or a mad
33178 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
33179 defines what &"too many"& means. Its default value is 10.
33181 When a new message is expected, one occurrence of RSET is not counted. This
33182 allows a client to send one RSET between messages (this is not necessary,
33183 but some clients do it). Exim also allows one uncounted occurrence of HELO
33184 or EHLO, and one occurrence of STARTTLS between messages. After
33185 starting up a TLS session, another EHLO is expected, and so it too is not
33188 The first occurrence of AUTH in a connection, or immediately following
33189 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
33190 RCPT, DATA, and QUIT are counted.
33192 You can control which hosts are subject to the limit set by
33193 &%smtp_accept_max_nonmail%& by setting
33194 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
33195 the limit apply to all hosts. This option means that you can exclude any
33196 specific badly-behaved hosts that you have to live with.
33201 .section "The VRFY and EXPN commands" "SECID237"
33202 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
33203 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
33204 appropriate) in order to decide whether the command should be accepted or not.
33205 If no ACL is defined, the command is rejected.
33207 .cindex "VRFY" "processing"
33208 When VRFY is accepted, it runs exactly the same code as when Exim is
33209 called with the &%-bv%& option.
33211 .cindex "EXPN" "processing"
33212 When EXPN is accepted, a single-level expansion of the address is done.
33213 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
33214 than a verification (the &%-bv%& option). If an unqualified local part is given
33215 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
33216 of VRFY and EXPN commands are logged on the main and reject logs, and
33217 VRFY verification failures are logged on the main log for consistency with
33222 .section "The ETRN command" "SECTETRN"
33223 .cindex "ETRN" "processing"
33224 RFC 1985 describes an SMTP command called ETRN that is designed to
33225 overcome the security problems of the TURN command (which has fallen into
33226 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
33227 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
33228 should be accepted or not. If no ACL is defined, the command is rejected.
33230 The ETRN command is concerned with &"releasing"& messages that are awaiting
33231 delivery to certain hosts. As Exim does not organize its message queue by host,
33232 the only form of ETRN that is supported by default is the one where the
33233 text starts with the &"#"& prefix, in which case the remainder of the text is
33234 specific to the SMTP server. A valid ETRN command causes a run of Exim with
33235 the &%-R%& option to happen, with the remainder of the ETRN text as its
33236 argument. For example,
33244 which causes a delivery attempt on all messages with undelivered addresses
33245 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
33246 default), Exim prevents the simultaneous execution of more than one queue run
33247 for the same argument string as a result of an ETRN command. This stops
33248 a misbehaving client from starting more than one queue runner at once.
33250 .cindex "hints database" "ETRN serialization"
33251 Exim implements the serialization by means of a hints database in which a
33252 record is written whenever a process is started by ETRN, and deleted when
33253 the process completes. However, Exim does not keep the SMTP session waiting for
33254 the ETRN process to complete. Once ETRN is accepted, the client is sent
33255 a &"success"& return code. Obviously there is scope for hints records to get
33256 left lying around if there is a system or program crash. To guard against this,
33257 Exim ignores any records that are more than six hours old.
33259 .oindex "&%smtp_etrn_command%&"
33260 For more control over what ETRN does, the &%smtp_etrn_command%& option can
33261 used. This specifies a command that is run whenever ETRN is received,
33262 whatever the form of its argument. For
33265 smtp_etrn_command = /etc/etrn_command $domain \
33266 $sender_host_address
33268 .vindex "&$domain$&"
33269 The string is split up into arguments which are independently expanded. The
33270 expansion variable &$domain$& is set to the argument of the ETRN command,
33271 and no syntax checking is done on the contents of this argument. Exim does not
33272 wait for the command to complete, so its status code is not checked. Exim runs
33273 under its own uid and gid when receiving incoming SMTP, so it is not possible
33274 for it to change them before running the command.
33278 .section "Incoming local SMTP" "SECID238"
33279 .cindex "SMTP" "local incoming"
33280 Some user agents use SMTP to pass messages to their local MTA using the
33281 standard input and output, as opposed to passing the envelope on the command
33282 line and writing the message to the standard input. This is supported by the
33283 &%-bs%& option. This form of SMTP is handled in the same way as incoming
33284 messages over TCP/IP (including the use of ACLs), except that the envelope
33285 sender given in a MAIL command is ignored unless the caller is trusted. In
33286 an ACL you can detect this form of SMTP input by testing for an empty host
33287 identification. It is common to have this as the first line in the ACL that
33288 runs for RCPT commands:
33292 This accepts SMTP messages from local processes without doing any other tests.
33296 .section "Outgoing batched SMTP" "SECTbatchSMTP"
33297 .cindex "SMTP" "batched outgoing"
33298 .cindex "batched SMTP output"
33299 Both the &(appendfile)& and &(pipe)& transports can be used for handling
33300 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
33301 be output in BSMTP format. No SMTP responses are possible for this form of
33302 delivery. All it is doing is using SMTP commands as a way of transmitting the
33303 envelope along with the message.
33305 The message is written to the file or pipe preceded by the SMTP commands
33306 MAIL and RCPT, and followed by a line containing a single dot. Lines in
33307 the message that start with a dot have an extra dot added. The SMTP command
33308 HELO is not normally used. If it is required, the &%message_prefix%& option
33309 can be used to specify it.
33311 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
33312 one recipient address at a time by default. However, you can arrange for them
33313 to handle several addresses at once by setting the &%batch_max%& option. When
33314 this is done for BSMTP, messages may contain multiple RCPT commands. See
33315 chapter &<<CHAPbatching>>& for more details.
33318 When one or more addresses are routed to a BSMTP transport by a router that
33319 sets up a host list, the name of the first host on the list is available to the
33320 transport in the variable &$host$&. Here is an example of such a transport and
33325 driver = manualroute
33326 transport = smtp_appendfile
33327 route_list = domain.example batch.host.example
33331 driver = appendfile
33332 directory = /var/bsmtp/$host
33337 This causes messages addressed to &'domain.example'& to be written in BSMTP
33338 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
33339 message (unless there are more than 1000 recipients).
33343 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
33344 .cindex "SMTP" "batched incoming"
33345 .cindex "batched SMTP input"
33346 The &%-bS%& command line option causes Exim to accept one or more messages by
33347 reading SMTP on the standard input, but to generate no responses. If the caller
33348 is trusted, the senders in the MAIL commands are believed; otherwise the
33349 sender is always the caller of Exim. Unqualified senders and receivers are not
33350 rejected (there seems little point) but instead just get qualified. HELO
33351 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
33352 as NOOP; QUIT quits.
33354 Minimal policy checking is done for BSMTP input. Only the non-SMTP
33355 ACL is run in the same way as for non-SMTP local input.
33357 If an error is detected while reading a message, including a missing &"."& at
33358 the end, Exim gives up immediately. It writes details of the error to the
33359 standard output in a stylized way that the calling program should be able to
33360 make some use of automatically, for example:
33362 554 Unexpected end of file
33363 Transaction started in line 10
33364 Error detected in line 14
33366 It writes a more verbose version, for human consumption, to the standard error
33369 An error was detected while processing a file of BSMTP input.
33370 The error message was:
33372 501 '>' missing at end of address
33374 The SMTP transaction started in line 10.
33375 The error was detected in line 12.
33376 The SMTP command at fault was:
33378 rcpt to:<malformed@in.com.plete
33380 1 previous message was successfully processed.
33381 The rest of the batch was abandoned.
33383 The return code from Exim is zero only if there were no errors. It is 1 if some
33384 messages were accepted before an error was detected, and 2 if no messages were
33386 .ecindex IIDsmtpproc1
33387 .ecindex IIDsmtpproc2
33391 . ////////////////////////////////////////////////////////////////////////////
33392 . ////////////////////////////////////////////////////////////////////////////
33394 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
33395 "Customizing messages"
33396 When a message fails to be delivered, or remains on the queue for more than a
33397 configured amount of time, Exim sends a message to the original sender, or
33398 to an alternative configured address. The text of these messages is built into
33399 the code of Exim, but it is possible to change it, either by adding a single
33400 string, or by replacing each of the paragraphs by text supplied in a file.
33402 The &'From:'& and &'To:'& header lines are automatically generated; you can
33403 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
33404 option. Exim also adds the line
33406 Auto-Submitted: auto-generated
33408 to all warning and bounce messages,
33411 .section "Customizing bounce messages" "SECID239"
33412 .cindex "customizing" "bounce message"
33413 .cindex "bounce message" "customizing"
33414 If &%bounce_message_text%& is set, its contents are included in the default
33415 message immediately after &"This message was created automatically by mail
33416 delivery software."& The string is not expanded. It is not used if
33417 &%bounce_message_file%& is set.
33419 When &%bounce_message_file%& is set, it must point to a template file for
33420 constructing error messages. The file consists of a series of text items,
33421 separated by lines consisting of exactly four asterisks. If the file cannot be
33422 opened, default text is used and a message is written to the main and panic
33423 logs. If any text item in the file is empty, default text is used for that
33426 .vindex "&$bounce_recipient$&"
33427 .vindex "&$bounce_return_size_limit$&"
33428 Each item of text that is read from the file is expanded, and there are two
33429 expansion variables which can be of use here: &$bounce_recipient$& is set to
33430 the recipient of an error message while it is being created, and
33431 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
33432 option, rounded to a whole number.
33434 The items must appear in the file in the following order:
33437 The first item is included in the headers, and should include at least a
33438 &'Subject:'& header. Exim does not check the syntax of these headers.
33440 The second item forms the start of the error message. After it, Exim lists the
33441 failing addresses with their error messages.
33443 The third item is used to introduce any text from pipe transports that is to be
33444 returned to the sender. It is omitted if there is no such text.
33446 The fourth item is used to introduce the copy of the message that is returned
33447 as part of the error report.
33449 The fifth item is added after the fourth one if the returned message is
33450 truncated because it is bigger than &%return_size_limit%&.
33452 The sixth item is added after the copy of the original message.
33455 The default state (&%bounce_message_file%& unset) is equivalent to the
33456 following file, in which the sixth item is empty. The &'Subject:'& and some
33457 other lines have been split in order to fit them on the page:
33459 Subject: Mail delivery failed
33460 ${if eq{$sender_address}{$bounce_recipient}
33461 {: returning message to sender}}
33463 This message was created automatically by mail delivery software.
33465 A message ${if eq{$sender_address}{$bounce_recipient}
33466 {that you sent }{sent by
33470 }}could not be delivered to all of its recipients.
33471 This is a permanent error. The following address(es) failed:
33473 The following text was generated during the delivery attempt(s):
33475 ------ This is a copy of the message, including all the headers.
33478 ------ The body of the message is $message_size characters long;
33480 ------ $bounce_return_size_limit or so are included here.
33483 .section "Customizing warning messages" "SECTcustwarn"
33484 .cindex "customizing" "warning message"
33485 .cindex "warning of delay" "customizing the message"
33486 The option &%warn_message_file%& can be pointed at a template file for use when
33487 warnings about message delays are created. In this case there are only three
33491 The first item is included in the headers, and should include at least a
33492 &'Subject:'& header. Exim does not check the syntax of these headers.
33494 The second item forms the start of the warning message. After it, Exim lists
33495 the delayed addresses.
33497 The third item then ends the message.
33500 The default state is equivalent to the following file, except that some lines
33501 have been split here, in order to fit them on the page:
33503 Subject: Warning: message $message_exim_id delayed
33504 $warn_message_delay
33506 This message was created automatically by mail delivery software.
33508 A message ${if eq{$sender_address}{$warn_message_recipients}
33509 {that you sent }{sent by
33513 }}has not been delivered to all of its recipients after
33514 more than $warn_message_delay on the queue on $primary_hostname.
33516 The message identifier is: $message_exim_id
33517 The subject of the message is: $h_subject
33518 The date of the message is: $h_date
33520 The following address(es) have not yet been delivered:
33522 No action is required on your part. Delivery attempts will
33523 continue for some time, and this warning may be repeated at
33524 intervals if the message remains undelivered. Eventually the
33525 mail delivery software will give up, and when that happens,
33526 the message will be returned to you.
33528 .vindex "&$warn_message_delay$&"
33529 .vindex "&$warn_message_recipients$&"
33530 However, in the default state the subject and date lines are omitted if no
33531 appropriate headers exist. During the expansion of this file,
33532 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
33533 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
33534 of recipients for the warning message. There may be more than one if there are
33535 multiple addresses with different &%errors_to%& settings on the routers that
33541 . ////////////////////////////////////////////////////////////////////////////
33542 . ////////////////////////////////////////////////////////////////////////////
33544 .chapter "Some common configuration settings" "CHAPcomconreq"
33545 This chapter discusses some configuration settings that seem to be fairly
33546 common. More examples and discussion can be found in the Exim book.
33550 .section "Sending mail to a smart host" "SECID240"
33551 .cindex "smart host" "example router"
33552 If you want to send all mail for non-local domains to a &"smart host"&, you
33553 should replace the default &(dnslookup)& router with a router which does the
33554 routing explicitly:
33556 send_to_smart_host:
33557 driver = manualroute
33558 route_list = !+local_domains smart.host.name
33559 transport = remote_smtp
33561 You can use the smart host's IP address instead of the name if you wish.
33562 If you are using Exim only to submit messages to a smart host, and not for
33563 receiving incoming messages, you can arrange for it to do the submission
33564 synchronously by setting the &%mua_wrapper%& option (see chapter
33565 &<<CHAPnonqueueing>>&).
33570 .section "Using Exim to handle mailing lists" "SECTmailinglists"
33571 .cindex "mailing lists"
33572 Exim can be used to run simple mailing lists, but for large and/or complicated
33573 requirements, the use of additional specialized mailing list software such as
33574 Majordomo or Mailman is recommended.
33576 The &(redirect)& router can be used to handle mailing lists where each list
33577 is maintained in a separate file, which can therefore be managed by an
33578 independent manager. The &%domains%& router option can be used to run these
33579 lists in a separate domain from normal mail. For example:
33583 domains = lists.example
33584 file = /usr/lists/$local_part
33587 errors_to = $local_part-request@lists.example
33590 This router is skipped for domains other than &'lists.example'&. For addresses
33591 in that domain, it looks for a file that matches the local part. If there is no
33592 such file, the router declines, but because &%no_more%& is set, no subsequent
33593 routers are tried, and so the whole delivery fails.
33595 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
33596 expanded into a file name or a pipe delivery, which is usually inappropriate in
33599 .oindex "&%errors_to%&"
33600 The &%errors_to%& option specifies that any delivery errors caused by addresses
33601 taken from a mailing list are to be sent to the given address rather than the
33602 original sender of the message. However, before acting on this, Exim verifies
33603 the error address, and ignores it if verification fails.
33605 For example, using the configuration above, mail sent to
33606 &'dicts@lists.example'& is passed on to those addresses contained in
33607 &_/usr/lists/dicts_&, with error reports directed to
33608 &'dicts-request@lists.example'&, provided that this address can be verified.
33609 There could be a file called &_/usr/lists/dicts-request_& containing
33610 the address(es) of this particular list's manager(s), but other approaches,
33611 such as setting up an earlier router (possibly using the &%local_part_prefix%&
33612 or &%local_part_suffix%& options) to handle addresses of the form
33613 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
33617 .section "Syntax errors in mailing lists" "SECID241"
33618 .cindex "mailing lists" "syntax errors in"
33619 If an entry in redirection data contains a syntax error, Exim normally defers
33620 delivery of the original address. That means that a syntax error in a mailing
33621 list holds up all deliveries to the list. This may not be appropriate when a
33622 list is being maintained automatically from data supplied by users, and the
33623 addresses are not rigorously checked.
33625 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
33626 entries that fail to parse, noting the incident in the log. If in addition
33627 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
33628 whenever a broken address is skipped. It is usually appropriate to set
33629 &%syntax_errors_to%& to the same address as &%errors_to%&.
33633 .section "Re-expansion of mailing lists" "SECID242"
33634 .cindex "mailing lists" "re-expansion of"
33635 Exim remembers every individual address to which a message has been delivered,
33636 in order to avoid duplication, but it normally stores only the original
33637 recipient addresses with a message. If all the deliveries to a mailing list
33638 cannot be done at the first attempt, the mailing list is re-expanded when the
33639 delivery is next tried. This means that alterations to the list are taken into
33640 account at each delivery attempt, so addresses that have been added to
33641 the list since the message arrived will therefore receive a copy of the
33642 message, even though it pre-dates their subscription.
33644 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
33645 on the &(redirect)& router. If this is done, any addresses generated by the
33646 router that fail to deliver at the first attempt are added to the message as
33647 &"top level"& addresses, and the parent address that generated them is marked
33648 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
33649 subsequent delivery attempts. The disadvantage of this is that if any of the
33650 failing addresses are incorrect, correcting them in the file has no effect on
33651 pre-existing messages.
33653 The original top-level address is remembered with each of the generated
33654 addresses, and is output in any log messages. However, any intermediate parent
33655 addresses are not recorded. This makes a difference to the log only if the
33656 &%all_parents%& selector is set, but for mailing lists there is normally only
33657 one level of expansion anyway.
33661 .section "Closed mailing lists" "SECID243"
33662 .cindex "mailing lists" "closed"
33663 The examples so far have assumed open mailing lists, to which anybody may
33664 send mail. It is also possible to set up closed lists, where mail is accepted
33665 from specified senders only. This is done by making use of the generic
33666 &%senders%& option to restrict the router that handles the list.
33668 The following example uses the same file as a list of recipients and as a list
33669 of permitted senders. It requires three routers:
33673 domains = lists.example
33674 local_part_suffix = -request
33675 file = /usr/lists/$local_part$local_part_suffix
33680 domains = lists.example
33681 senders = ${if exists {/usr/lists/$local_part}\
33682 {lsearch;/usr/lists/$local_part}{*}}
33683 file = /usr/lists/$local_part
33686 errors_to = $local_part-request@lists.example
33691 domains = lists.example
33693 data = :fail: $local_part@lists.example is a closed mailing list
33695 All three routers have the same &%domains%& setting, so for any other domains,
33696 they are all skipped. The first router runs only if the local part ends in
33697 &%-request%&. It handles messages to the list manager(s) by means of an open
33700 The second router runs only if the &%senders%& precondition is satisfied. It
33701 checks for the existence of a list that corresponds to the local part, and then
33702 checks that the sender is on the list by means of a linear search. It is
33703 necessary to check for the existence of the file before trying to search it,
33704 because otherwise Exim thinks there is a configuration error. If the file does
33705 not exist, the expansion of &%senders%& is *, which matches all senders. This
33706 means that the router runs, but because there is no list, declines, and
33707 &%no_more%& ensures that no further routers are run. The address fails with an
33708 &"unrouteable address"& error.
33710 The third router runs only if the second router is skipped, which happens when
33711 a mailing list exists, but the sender is not on it. This router forcibly fails
33712 the address, giving a suitable error message.
33717 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
33719 .cindex "Variable Envelope Return Paths"
33720 .cindex "envelope sender"
33721 Variable Envelope Return Paths &-- see &url(http://cr.yp.to/proto/verp.txt) &--
33722 are a way of helping mailing list administrators discover which subscription
33723 address is the cause of a particular delivery failure. The idea is to encode
33724 the original recipient address in the outgoing envelope sender address, so that
33725 if the message is forwarded by another host and then subsequently bounces, the
33726 original recipient can be extracted from the recipient address of the bounce.
33728 .oindex &%errors_to%&
33729 .oindex &%return_path%&
33730 Envelope sender addresses can be modified by Exim using two different
33731 facilities: the &%errors_to%& option on a router (as shown in previous mailing
33732 list examples), or the &%return_path%& option on a transport. The second of
33733 these is effective only if the message is successfully delivered to another
33734 host; it is not used for errors detected on the local host (see the description
33735 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
33736 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
33742 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
33743 {$1-request+$local_part=$domain@your.dom.example}fail}
33745 This has the effect of rewriting the return path (envelope sender) on outgoing
33746 SMTP messages, if the local part of the original return path ends in
33747 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
33748 local part and domain of the recipient into the return path. Suppose, for
33749 example, that a message whose return path has been set to
33750 &'somelist-request@your.dom.example'& is sent to
33751 &'subscriber@other.dom.example'&. In the transport, the return path is
33754 somelist-request+subscriber=other.dom.example@your.dom.example
33756 .vindex "&$local_part$&"
33757 For this to work, you must tell Exim to send multiple copies of messages that
33758 have more than one recipient, so that each copy has just one recipient. This is
33759 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
33760 might be sent to several different recipients in the same domain, in which case
33761 &$local_part$& is not available in the transport, because it is not unique.
33763 Unless your host is doing nothing but mailing list deliveries, you should
33764 probably use a separate transport for the VERP deliveries, so as not to use
33765 extra resources in making one-per-recipient copies for other deliveries. This
33766 can easily be done by expanding the &%transport%& option in the router:
33770 domains = ! +local_domains
33772 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
33773 {verp_smtp}{remote_smtp}}
33776 If you want to change the return path using &%errors_to%& in a router instead
33777 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
33778 routers that handle mailing list addresses. This will ensure that all delivery
33779 errors, including those detected on the local host, are sent to the VERP
33782 On a host that does no local deliveries and has no manual routing, only the
33783 &(dnslookup)& router needs to be changed. A special transport is not needed for
33784 SMTP deliveries. Every mailing list recipient has its own return path value,
33785 and so Exim must hand them to the transport one at a time. Here is an example
33786 of a &(dnslookup)& router that implements VERP:
33790 domains = ! +local_domains
33791 transport = remote_smtp
33793 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
33794 {$1-request+$local_part=$domain@your.dom.example}fail}
33797 Before you start sending out messages with VERPed return paths, you must also
33798 configure Exim to accept the bounce messages that come back to those paths.
33799 Typically this is done by setting a &%local_part_suffix%& option for a
33800 router, and using this to route the messages to wherever you want to handle
33803 The overhead incurred in using VERP depends very much on the size of the
33804 message, the number of recipient addresses that resolve to the same remote
33805 host, and the speed of the connection over which the message is being sent. If
33806 a lot of addresses resolve to the same host and the connection is slow, sending
33807 a separate copy of the message for each address may take substantially longer
33808 than sending a single copy with many recipients (for which VERP cannot be
33816 .section "Virtual domains" "SECTvirtualdomains"
33817 .cindex "virtual domains"
33818 .cindex "domain" "virtual"
33819 The phrase &'virtual domain'& is unfortunately used with two rather different
33823 A domain for which there are no real mailboxes; all valid local parts are
33824 aliases for other email addresses. Common examples are organizational
33825 top-level domains and &"vanity"& domains.
33827 One of a number of independent domains that are all handled by the same host,
33828 with mailboxes on that host, but where the mailbox owners do not necessarily
33829 have login accounts on that host.
33832 The first usage is probably more common, and does seem more &"virtual"& than
33833 the second. This kind of domain can be handled in Exim with a straightforward
33834 aliasing router. One approach is to create a separate alias file for each
33835 virtual domain. Exim can test for the existence of the alias file to determine
33836 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
33837 to a router of this form:
33841 domains = dsearch;/etc/mail/virtual
33842 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
33845 The &%domains%& option specifies that the router is to be skipped, unless there
33846 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
33847 domain that is being processed. When the router runs, it looks up the local
33848 part in the file to find a new address (or list of addresses). The &%no_more%&
33849 setting ensures that if the lookup fails (leading to &%data%& being an empty
33850 string), Exim gives up on the address without trying any subsequent routers.
33852 This one router can handle all the virtual domains because the alias file names
33853 follow a fixed pattern. Permissions can be arranged so that appropriate people
33854 can edit the different alias files. A successful aliasing operation results in
33855 a new envelope recipient address, which is then routed from scratch.
33857 The other kind of &"virtual"& domain can also be handled in a straightforward
33858 way. One approach is to create a file for each domain containing a list of
33859 valid local parts, and use it in a router like this:
33863 domains = dsearch;/etc/mail/domains
33864 local_parts = lsearch;/etc/mail/domains/$domain
33865 transport = my_mailboxes
33867 The address is accepted if there is a file for the domain, and the local part
33868 can be found in the file. The &%domains%& option is used to check for the
33869 file's existence because &%domains%& is tested before the &%local_parts%&
33870 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
33871 because that option is tested after &%local_parts%&. The transport is as
33875 driver = appendfile
33876 file = /var/mail/$domain/$local_part
33879 This uses a directory of mailboxes for each domain. The &%user%& setting is
33880 required, to specify which uid is to be used for writing to the mailboxes.
33882 The configuration shown here is just one example of how you might support this
33883 requirement. There are many other ways this kind of configuration can be set
33884 up, for example, by using a database instead of separate files to hold all the
33885 information about the domains.
33889 .section "Multiple user mailboxes" "SECTmulbox"
33890 .cindex "multiple mailboxes"
33891 .cindex "mailbox" "multiple"
33892 .cindex "local part" "prefix"
33893 .cindex "local part" "suffix"
33894 Heavy email users often want to operate with multiple mailboxes, into which
33895 incoming mail is automatically sorted. A popular way of handling this is to
33896 allow users to use multiple sender addresses, so that replies can easily be
33897 identified. Users are permitted to add prefixes or suffixes to their local
33898 parts for this purpose. The wildcard facility of the generic router options
33899 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
33900 example, consider this router:
33905 file = $home/.forward
33906 local_part_suffix = -*
33907 local_part_suffix_optional
33910 .vindex "&$local_part_suffix$&"
33911 It runs a user's &_.forward_& file for all local parts of the form
33912 &'username-*'&. Within the filter file the user can distinguish different
33913 cases by testing the variable &$local_part_suffix$&. For example:
33915 if $local_part_suffix contains -special then
33916 save /home/$local_part/Mail/special
33919 If the filter file does not exist, or does not deal with such addresses, they
33920 fall through to subsequent routers, and, assuming no subsequent use of the
33921 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
33922 control over which suffixes are valid.
33924 Alternatively, a suffix can be used to trigger the use of a different
33925 &_.forward_& file &-- which is the way a similar facility is implemented in
33931 file = $home/.forward$local_part_suffix
33932 local_part_suffix = -*
33933 local_part_suffix_optional
33936 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
33937 example, &_.forward-special_& is used. Once again, if the appropriate file
33938 does not exist, or does not deal with the address, it is passed on to
33939 subsequent routers, which could, if required, look for an unqualified
33940 &_.forward_& file to use as a default.
33944 .section "Simplified vacation processing" "SECID244"
33945 .cindex "vacation processing"
33946 The traditional way of running the &'vacation'& program is for a user to set up
33947 a pipe command in a &_.forward_& file
33948 (see section &<<SECTspecitredli>>& for syntax details).
33949 This is prone to error by inexperienced users. There are two features of Exim
33950 that can be used to make this process simpler for users:
33953 A local part prefix such as &"vacation-"& can be specified on a router which
33954 can cause the message to be delivered directly to the &'vacation'& program, or
33955 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
33956 &_.forward_& file are then much simpler. For example:
33958 spqr, vacation-spqr
33961 The &%require_files%& generic router option can be used to trigger a
33962 vacation delivery by checking for the existence of a certain file in the
33963 user's home directory. The &%unseen%& generic option should also be used, to
33964 ensure that the original delivery also proceeds. In this case, all the user has
33965 to do is to create a file called, say, &_.vacation_&, containing a vacation
33969 Another advantage of both these methods is that they both work even when the
33970 use of arbitrary pipes by users is locked out.
33974 .section "Taking copies of mail" "SECID245"
33975 .cindex "message" "copying every"
33976 Some installations have policies that require archive copies of all messages to
33977 be made. A single copy of each message can easily be taken by an appropriate
33978 command in a system filter, which could, for example, use a different file for
33979 each day's messages.
33981 There is also a shadow transport mechanism that can be used to take copies of
33982 messages that are successfully delivered by local transports, one copy per
33983 delivery. This could be used, &'inter alia'&, to implement automatic
33984 notification of delivery by sites that insist on doing such things.
33988 .section "Intermittently connected hosts" "SECID246"
33989 .cindex "intermittently connected hosts"
33990 It has become quite common (because it is cheaper) for hosts to connect to the
33991 Internet periodically rather than remain connected all the time. The normal
33992 arrangement is that mail for such hosts accumulates on a system that is
33993 permanently connected.
33995 Exim was designed for use on permanently connected hosts, and so it is not
33996 particularly well-suited to use in an intermittently connected environment.
33997 Nevertheless there are some features that can be used.
34000 .section "Exim on the upstream server host" "SECID247"
34001 It is tempting to arrange for incoming mail for the intermittently connected
34002 host to remain on Exim's queue until the client connects. However, this
34003 approach does not scale very well. Two different kinds of waiting message are
34004 being mixed up in the same queue &-- those that cannot be delivered because of
34005 some temporary problem, and those that are waiting for their destination host
34006 to connect. This makes it hard to manage the queue, as well as wasting
34007 resources, because each queue runner scans the entire queue.
34009 A better approach is to separate off those messages that are waiting for an
34010 intermittently connected host. This can be done by delivering these messages
34011 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
34012 format, from where they are transmitted by other software when their
34013 destination connects. This makes it easy to collect all the mail for one host
34014 in a single directory, and to apply local timeout rules on a per-message basis
34017 On a very small scale, leaving the mail on Exim's queue can be made to work. If
34018 you are doing this, you should configure Exim with a long retry period for the
34019 intermittent host. For example:
34021 cheshire.wonderland.fict.example * F,5d,24h
34023 This stops a lot of failed delivery attempts from occurring, but Exim remembers
34024 which messages it has queued up for that host. Once the intermittent host comes
34025 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
34026 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
34027 causes all the queued up messages to be delivered, often down a single SMTP
34028 connection. While the host remains connected, any new messages get delivered
34031 If the connecting hosts do not have fixed IP addresses, that is, if a host is
34032 issued with a different IP address each time it connects, Exim's retry
34033 mechanisms on the holding host get confused, because the IP address is normally
34034 used as part of the key string for holding retry information. This can be
34035 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
34036 Since this has disadvantages for permanently connected hosts, it is best to
34037 arrange a separate transport for the intermittently connected ones.
34041 .section "Exim on the intermittently connected client host" "SECID248"
34042 The value of &%smtp_accept_queue_per_connection%& should probably be
34043 increased, or even set to zero (that is, disabled) on the intermittently
34044 connected host, so that all incoming messages down a single connection get
34045 delivered immediately.
34047 .cindex "SMTP" "passed connection"
34048 .cindex "SMTP" "multiple deliveries"
34049 .cindex "multiple SMTP deliveries"
34050 Mail waiting to be sent from an intermittently connected host will probably
34051 not have been routed, because without a connection DNS lookups are not
34052 possible. This means that if a normal queue run is done at connection time,
34053 each message is likely to be sent in a separate SMTP session. This can be
34054 avoided by starting the queue run with a command line option beginning with
34055 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
34056 first pass, routing is done but no deliveries take place. The second pass is a
34057 normal queue run; since all the messages have been previously routed, those
34058 destined for the same host are likely to get sent as multiple deliveries in a
34059 single SMTP connection.
34063 . ////////////////////////////////////////////////////////////////////////////
34064 . ////////////////////////////////////////////////////////////////////////////
34066 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
34067 "Exim as a non-queueing client"
34068 .cindex "client, non-queueing"
34069 .cindex "smart host" "suppressing queueing"
34070 On a personal computer, it is a common requirement for all
34071 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
34072 configured to operate that way, for all the popular operating systems.
34073 However, there are some MUAs for Unix-like systems that cannot be so
34074 configured: they submit messages using the command line interface of
34075 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
34078 If the personal computer runs continuously, there is no problem, because it can
34079 run a conventional MTA that handles delivery to the smart host, and deal with
34080 any delays via its queueing mechanism. However, if the computer does not run
34081 continuously or runs different operating systems at different times, queueing
34082 email is not desirable.
34084 There is therefore a requirement for something that can provide the
34085 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
34086 any queueing or retrying facilities. Furthermore, the delivery to the smart
34087 host should be synchronous, so that if it fails, the sending MUA is immediately
34088 informed. In other words, we want something that extends an MUA that submits
34089 to a local MTA via the command line so that it behaves like one that submits
34090 to a remote smart host using TCP/SMTP.
34092 There are a number of applications (for example, there is one called &'ssmtp'&)
34093 that do this job. However, people have found them to be lacking in various
34094 ways. For instance, you might want to allow aliasing and forwarding to be done
34095 before sending a message to the smart host.
34097 Exim already had the necessary infrastructure for doing this job. Just a few
34098 tweaks were needed to make it behave as required, though it is somewhat of an
34099 overkill to use a fully-featured MTA for this purpose.
34101 .oindex "&%mua_wrapper%&"
34102 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
34103 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
34104 assumes that it is being used to &"wrap"& a command-line MUA in the manner
34105 just described. As well as setting &%mua_wrapper%&, you also need to provide a
34106 compatible router and transport configuration. Typically there will be just one
34107 router and one transport, sending everything to a smart host.
34109 When run in MUA wrapping mode, the behaviour of Exim changes in the
34113 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
34114 In other words, the only way to submit messages is via the command line.
34116 Each message is synchronously delivered as soon as it is received (&%-odi%& is
34117 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
34118 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
34119 does not finish until the delivery attempt is complete. If the delivery is
34120 successful, a zero return code is given.
34122 Address redirection is permitted, but the final routing for all addresses must
34123 be to the same remote transport, and to the same list of hosts. Furthermore,
34124 the return address (envelope sender) must be the same for all recipients, as
34125 must any added or deleted header lines. In other words, it must be possible to
34126 deliver the message in a single SMTP transaction, however many recipients there
34129 If these conditions are not met, or if routing any address results in a
34130 failure or defer status, or if Exim is unable to deliver all the recipients
34131 successfully to one of the smart hosts, delivery of the entire message fails.
34133 Because no queueing is allowed, all failures are treated as permanent; there
34134 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
34135 smart host. Furthermore, because only a single yes/no response can be given to
34136 the caller, it is not possible to deliver to some recipients and not others. If
34137 there is an error (temporary or permanent) for any recipient, all are failed.
34139 If more than one smart host is listed, Exim will try another host after a
34140 connection failure or a timeout, in the normal way. However, if this kind of
34141 failure happens for all the hosts, the delivery fails.
34143 When delivery fails, an error message is written to the standard error stream
34144 (as well as to Exim's log), and Exim exits to the caller with a return code
34145 value 1. The message is expunged from Exim's spool files. No bounce messages
34146 are ever generated.
34148 No retry data is maintained, and any retry rules are ignored.
34150 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
34151 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
34152 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
34155 The overall effect is that Exim makes a single synchronous attempt to deliver
34156 the message, failing if there is any kind of problem. Because no local
34157 deliveries are done and no daemon can be run, Exim does not need root
34158 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
34159 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
34160 the advantages and disadvantages of running without root privilege.
34165 . ////////////////////////////////////////////////////////////////////////////
34166 . ////////////////////////////////////////////////////////////////////////////
34168 .chapter "Log files" "CHAPlog"
34169 .scindex IIDloggen "log" "general description"
34170 .cindex "log" "types of"
34171 Exim writes three different logs, referred to as the main log, the reject log,
34176 The main log records the arrival of each message and each delivery in a single
34177 line in each case. The format is as compact as possible, in an attempt to keep
34178 down the size of log files. Two-character flag sequences make it easy to pick
34179 out these lines. A number of other events are recorded in the main log. Some of
34180 them are optional, in which case the &%log_selector%& option controls whether
34181 they are included or not. A Perl script called &'eximstats'&, which does simple
34182 analysis of main log files, is provided in the Exim distribution (see section
34183 &<<SECTmailstat>>&).
34185 .cindex "reject log"
34186 The reject log records information from messages that are rejected as a result
34187 of a configuration option (that is, for policy reasons).
34188 The first line of each rejection is a copy of the line that is also written to
34189 the main log. Then, if the message's header has been read at the time the log
34190 is written, its contents are written to this log. Only the original header
34191 lines are available; header lines added by ACLs are not logged. You can use the
34192 reject log to check that your policy controls are working correctly; on a busy
34193 host this may be easier than scanning the main log for rejection messages. You
34194 can suppress the writing of the reject log by setting &%write_rejectlog%&
34197 .cindex "panic log"
34198 .cindex "system log"
34199 When certain serious errors occur, Exim writes entries to its panic log. If the
34200 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
34201 are usually written to the main log as well, but can get lost amid the mass of
34202 other entries. The panic log should be empty under normal circumstances. It is
34203 therefore a good idea to check it (or to have a &'cron'& script check it)
34204 regularly, in order to become aware of any problems. When Exim cannot open its
34205 panic log, it tries as a last resort to write to the system log (syslog). This
34206 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
34207 message itself is written at priority LOG_CRIT.
34210 Every log line starts with a timestamp, in the format shown in the following
34211 example. Note that many of the examples shown in this chapter are line-wrapped.
34212 In the log file, this would be all on one line:
34214 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
34217 By default, the timestamps are in the local timezone. There are two
34218 ways of changing this:
34221 You can set the &%timezone%& option to a different time zone; in particular, if
34226 the timestamps will be in UTC (aka GMT).
34228 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
34231 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
34235 .cindex "log" "process ids in"
34236 .cindex "pid (process id)" "in log lines"
34237 Exim does not include its process id in log lines by default, but you can
34238 request that it does so by specifying the &`pid`& log selector (see section
34239 &<<SECTlogselector>>&). When this is set, the process id is output, in square
34240 brackets, immediately after the time and date.
34245 .section "Where the logs are written" "SECTwhelogwri"
34246 .cindex "log" "destination"
34247 .cindex "log" "to file"
34248 .cindex "log" "to syslog"
34250 The logs may be written to local files, or to syslog, or both. However, it
34251 should be noted that many syslog implementations use UDP as a transport, and
34252 are therefore unreliable in the sense that messages are not guaranteed to
34253 arrive at the loghost, nor is the ordering of messages necessarily maintained.
34254 It has also been reported that on large log files (tens of megabytes) you may
34255 need to tweak syslog to prevent it syncing the file with each write &-- on
34256 Linux this has been seen to make syslog take 90% plus of CPU time.
34258 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
34259 &_Local/Makefile_& or by setting &%log_file_path%& in the run time
34260 configuration. This latter string is expanded, so it can contain, for example,
34261 references to the host name:
34263 log_file_path = /var/log/$primary_hostname/exim_%slog
34265 It is generally advisable, however, to set the string in &_Local/Makefile_&
34266 rather than at run time, because then the setting is available right from the
34267 start of Exim's execution. Otherwise, if there's something it wants to log
34268 before it has read the configuration file (for example, an error in the
34269 configuration file) it will not use the path you want, and may not be able to
34272 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
34273 list, currently limited to at most two items. This is one option where the
34274 facility for changing a list separator may not be used. The list must always be
34275 colon-separated. If an item in the list is &"syslog"& then syslog is used;
34276 otherwise the item must either be an absolute path, containing &`%s`& at the
34277 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
34278 implying the use of a default path.
34280 When Exim encounters an empty item in the list, it searches the list defined by
34281 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
34282 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
34283 mean &"use the path specified at build time"&. It no such item exists, log
34284 files are written in the &_log_& subdirectory of the spool directory. This is
34285 equivalent to the setting:
34287 log_file_path = $spool_directory/log/%slog
34289 If you do not specify anything at build time or run time, that is where the
34292 A log file path may also contain &`%D`& or &`%M`& if datestamped log file names
34293 are in use &-- see section &<<SECTdatlogfil>>& below.
34295 Here are some examples of possible settings:
34297 &`LOG_FILE_PATH=syslog `& syslog only
34298 &`LOG_FILE_PATH=:syslog `& syslog and default path
34299 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
34300 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
34302 If there are more than two paths in the list, the first is used and a panic
34307 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
34308 .cindex "log" "cycling local files"
34309 .cindex "cycling logs"
34310 .cindex "&'exicyclog'&"
34311 .cindex "log" "local files; writing to"
34312 Some operating systems provide centralized and standardized methods for cycling
34313 log files. For those that do not, a utility script called &'exicyclog'& is
34314 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
34315 main and reject logs each time it is called. The maximum number of old logs to
34316 keep can be set. It is suggested this script is run as a daily &'cron'& job.
34318 An Exim delivery process opens the main log when it first needs to write to it,
34319 and it keeps the file open in case subsequent entries are required &-- for
34320 example, if a number of different deliveries are being done for the same
34321 message. However, remote SMTP deliveries can take a long time, and this means
34322 that the file may be kept open long after it is renamed if &'exicyclog'& or
34323 something similar is being used to rename log files on a regular basis. To
34324 ensure that a switch of log files is noticed as soon as possible, Exim calls
34325 &[stat()]& on the main log's name before reusing an open file, and if the file
34326 does not exist, or its inode has changed, the old file is closed and Exim
34327 tries to open the main log from scratch. Thus, an old log file may remain open
34328 for quite some time, but no Exim processes should write to it once it has been
34333 .section "Datestamped log files" "SECTdatlogfil"
34334 .cindex "log" "datestamped files"
34335 Instead of cycling the main and reject log files by renaming them
34336 periodically, some sites like to use files whose names contain a datestamp,
34337 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
34338 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
34339 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
34340 point where the datestamp is required. For example:
34342 log_file_path = /var/spool/exim/log/%slog-%D
34343 log_file_path = /var/log/exim-%s-%D.log
34344 log_file_path = /var/spool/exim/log/%D-%slog
34345 log_file_path = /var/log/exim/%s.%M
34347 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
34348 examples of names generated by the above examples:
34350 /var/spool/exim/log/mainlog-20021225
34351 /var/log/exim-reject-20021225.log
34352 /var/spool/exim/log/20021225-mainlog
34353 /var/log/exim/main.200212
34355 When this form of log file is specified, Exim automatically switches to new
34356 files at midnight. It does not make any attempt to compress old logs; you
34357 will need to write your own script if you require this. You should not
34358 run &'exicyclog'& with this form of logging.
34360 The location of the panic log is also determined by &%log_file_path%&, but it
34361 is not datestamped, because rotation of the panic log does not make sense.
34362 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
34363 the string. In addition, if it immediately follows a slash, a following
34364 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
34365 character is removed. Thus, the four examples above would give these panic
34368 /var/spool/exim/log/paniclog
34369 /var/log/exim-panic.log
34370 /var/spool/exim/log/paniclog
34371 /var/log/exim/panic
34375 .section "Logging to syslog" "SECID249"
34376 .cindex "log" "syslog; writing to"
34377 The use of syslog does not change what Exim logs or the format of its messages,
34378 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
34379 Exim's log lines are omitted when these lines are sent to syslog. Apart from
34380 that, the same strings are written to syslog as to log files. The syslog
34381 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
34382 by default, but you can change these by setting the &%syslog_facility%& and
34383 &%syslog_processname%& options, respectively. If Exim was compiled with
34384 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
34385 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
34386 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
34387 the time and host name to each line.
34388 The three log streams are mapped onto syslog priorities as follows:
34391 &'mainlog'& is mapped to LOG_INFO
34393 &'rejectlog'& is mapped to LOG_NOTICE
34395 &'paniclog'& is mapped to LOG_ALERT
34398 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
34399 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
34400 these are routed by syslog to the same place. You can suppress this duplication
34401 by setting &%syslog_duplication%& false.
34403 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
34404 entries contain multiple lines when headers are included. To cope with both
34405 these cases, entries written to syslog are split into separate &[syslog()]&
34406 calls at each internal newline, and also after a maximum of
34407 870 data characters. (This allows for a total syslog line length of 1024, when
34408 additions such as timestamps are added.) If you are running a syslog
34409 replacement that can handle lines longer than the 1024 characters allowed by
34410 RFC 3164, you should set
34412 SYSLOG_LONG_LINES=yes
34414 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
34415 lines, but it still splits at internal newlines in &'reject'& log entries.
34417 To make it easy to re-assemble split lines later, each component of a split
34418 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
34419 where <&'n'&> is the component number and <&'m'&> is the total number of
34420 components in the entry. The / delimiter is used when the line was split
34421 because it was too long; if it was split because of an internal newline, the \
34422 delimiter is used. For example, supposing the length limit to be 50 instead of
34423 870, the following would be the result of a typical rejection message to
34424 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
34425 name, and pid as added by syslog:
34427 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
34428 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
34429 [3/5] when scanning for sender: missing or malformed lo
34430 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
34433 The same error might cause the following lines to be written to &"rejectlog"&
34436 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
34437 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
34438 [3/18] er when scanning for sender: missing or malformed
34439 [4/18] local part in "<>" (envelope sender is <ph10@cam
34441 [6\18] Recipients: ph10@some.domain.cam.example
34442 [7\18] P Received: from [127.0.0.1] (ident=ph10)
34443 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
34444 [9\18] id 16RdAL-0006pc-00
34445 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
34446 [11\18] 09:43 +0100
34448 [13\18] Subject: this is a test header
34449 [18\18] X-something: this is another header
34450 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
34453 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
34455 Log lines that are neither too long nor contain newlines are written to syslog
34456 without modification.
34458 If only syslog is being used, the Exim monitor is unable to provide a log tail
34459 display, unless syslog is routing &'mainlog'& to a file on the local host and
34460 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
34465 .section "Log line flags" "SECID250"
34466 One line is written to the main log for each message received, and for each
34467 successful, unsuccessful, and delayed delivery. These lines can readily be
34468 picked out by the distinctive two-character flags that immediately follow the
34469 timestamp. The flags are:
34471 &`<=`& message arrival
34472 &`=>`& normal message delivery
34473 &`->`& additional address in same delivery
34474 &`>>`& cutthrough message delivery
34475 &`*>`& delivery suppressed by &%-N%&
34476 &`**`& delivery failed; address bounced
34477 &`==`& delivery deferred; temporary problem
34481 .section "Logging message reception" "SECID251"
34482 .cindex "log" "reception line"
34483 The format of the single-line entry in the main log that is written for every
34484 message received is shown in the basic example below, which is split over
34485 several lines in order to fit it on the page:
34487 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
34488 H=mailer.fict.example [192.168.123.123] U=exim
34489 P=smtp S=5678 id=<incoming message id>
34491 The address immediately following &"<="& is the envelope sender address. A
34492 bounce message is shown with the sender address &"<>"&, and if it is locally
34493 generated, this is followed by an item of the form
34497 which is a reference to the message that caused the bounce to be sent.
34501 For messages from other hosts, the H and U fields identify the remote host and
34502 record the RFC 1413 identity of the user that sent the message, if one was
34503 received. The number given in square brackets is the IP address of the sending
34504 host. If there is a single, unparenthesized host name in the H field, as
34505 above, it has been verified to correspond to the IP address (see the
34506 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
34507 by the remote host in the SMTP HELO or EHLO command, and has not been
34508 verified. If verification yields a different name to that given for HELO or
34509 EHLO, the verified name appears first, followed by the HELO or EHLO
34510 name in parentheses.
34512 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
34513 without brackets, in the HELO or EHLO command, leading to entries in
34514 the log containing text like these examples:
34516 H=(10.21.32.43) [192.168.8.34]
34517 H=([10.21.32.43]) [192.168.8.34]
34519 This can be confusing. Only the final address in square brackets can be relied
34522 For locally generated messages (that is, messages not received over TCP/IP),
34523 the H field is omitted, and the U field contains the login name of the caller
34526 .cindex "authentication" "logging"
34527 .cindex "AUTH" "logging"
34528 For all messages, the P field specifies the protocol used to receive the
34529 message. This is the value that is stored in &$received_protocol$&. In the case
34530 of incoming SMTP messages, the value indicates whether or not any SMTP
34531 extensions (ESMTP), encryption, or authentication were used. If the SMTP
34532 session was encrypted, there is an additional X field that records the cipher
34533 suite that was used.
34535 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
34536 hosts that have authenticated themselves using the SMTP AUTH command. The first
34537 value is used when the SMTP connection was encrypted (&"secure"&). In this case
34538 there is an additional item A= followed by the name of the authenticator that
34539 was used. If an authenticated identification was set up by the authenticator's
34540 &%server_set_id%& option, this is logged too, separated by a colon from the
34541 authenticator name.
34543 .cindex "size" "of message"
34544 The id field records the existing message id, if present. The size of the
34545 received message is given by the S field. When the message is delivered,
34546 headers may be removed or added, so that the size of delivered copies of the
34547 message may not correspond with this value (and indeed may be different to each
34550 The &%log_selector%& option can be used to request the logging of additional
34551 data when a message is received. See section &<<SECTlogselector>>& below.
34555 .section "Logging deliveries" "SECID252"
34556 .cindex "log" "delivery line"
34557 The format of the single-line entry in the main log that is written for every
34558 delivery is shown in one of the examples below, for local and remote
34559 deliveries, respectively. Each example has been split into two lines in order
34560 to fit it on the page:
34562 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
34563 <marv@hitch.fict.example> R=localuser T=local_delivery
34564 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
34565 monk@holistic.fict.example R=dnslookup T=remote_smtp
34566 H=holistic.fict.example [192.168.234.234]
34568 For ordinary local deliveries, the original address is given in angle brackets
34569 after the final delivery address, which might be a pipe or a file. If
34570 intermediate address(es) exist between the original and the final address, the
34571 last of these is given in parentheses after the final address. The R and T
34572 fields record the router and transport that were used to process the address.
34574 If SMTP AUTH was used for the delivery there is an additional item A=
34575 followed by the name of the authenticator that was used.
34576 If an authenticated identification was set up by the authenticator's &%client_set_id%&
34577 option, this is logged too, separated by a colon from the authenticator name.
34579 If a shadow transport was run after a successful local delivery, the log line
34580 for the successful delivery has an item added on the end, of the form
34582 &`ST=<`&&'shadow transport name'&&`>`&
34584 If the shadow transport did not succeed, the error message is put in
34585 parentheses afterwards.
34587 .cindex "asterisk" "after IP address"
34588 When more than one address is included in a single delivery (for example, two
34589 SMTP RCPT commands in one transaction) the second and subsequent addresses are
34590 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
34591 down a single SMTP connection, an asterisk follows the IP address in the log
34592 lines for the second and subsequent messages.
34594 .cindex "delivery" "cutthrough; logging"
34595 .cindex "cutthrough" "logging"
34596 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
34597 line precedes the reception line, since cutthrough waits for a possible
34598 rejection from the destination in case it can reject the sourced item.
34600 The generation of a reply message by a filter file gets logged as a
34601 &"delivery"& to the addressee, preceded by &">"&.
34603 The &%log_selector%& option can be used to request the logging of additional
34604 data when a message is delivered. See section &<<SECTlogselector>>& below.
34607 .section "Discarded deliveries" "SECID253"
34608 .cindex "discarded messages"
34609 .cindex "message" "discarded"
34610 .cindex "delivery" "discarded; logging"
34611 When a message is discarded as a result of the command &"seen finish"& being
34612 obeyed in a filter file which generates no deliveries, a log entry of the form
34614 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
34615 <low.club@bridge.example> R=userforward
34617 is written, to record why no deliveries are logged. When a message is discarded
34618 because it is aliased to &":blackhole:"& the log line is like this:
34620 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
34621 <hole@nowhere.example> R=blackhole_router
34625 .section "Deferred deliveries" "SECID254"
34626 When a delivery is deferred, a line of the following form is logged:
34628 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
34629 R=dnslookup T=smtp defer (146): Connection refused
34631 In the case of remote deliveries, the error is the one that was given for the
34632 last IP address that was tried. Details of individual SMTP failures are also
34633 written to the log, so the above line would be preceded by something like
34635 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
34636 mail1.endrest.example [192.168.239.239]: Connection refused
34638 When a deferred address is skipped because its retry time has not been reached,
34639 a message is written to the log, but this can be suppressed by setting an
34640 appropriate value in &%log_selector%&.
34644 .section "Delivery failures" "SECID255"
34645 .cindex "delivery" "failure; logging"
34646 If a delivery fails because an address cannot be routed, a line of the
34647 following form is logged:
34649 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
34650 <jim@trek99.example>: unknown mail domain
34652 If a delivery fails at transport time, the router and transport are shown, and
34653 the response from the remote host is included, as in this example:
34655 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
34656 R=dnslookup T=remote_smtp: SMTP error from remote mailer
34657 after pipelined RCPT TO:<ace400@pb.example>: host
34658 pbmail3.py.example [192.168.63.111]: 553 5.3.0
34659 <ace400@pb.example>...Addressee unknown
34661 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
34662 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
34663 disabling PIPELINING. The log lines for all forms of delivery failure are
34664 flagged with &`**`&.
34668 .section "Fake deliveries" "SECID256"
34669 .cindex "delivery" "fake; logging"
34670 If a delivery does not actually take place because the &%-N%& option has been
34671 used to suppress it, a normal delivery line is written to the log, except that
34672 &"=>"& is replaced by &"*>"&.
34676 .section "Completion" "SECID257"
34679 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
34681 is written to the main log when a message is about to be removed from the spool
34682 at the end of its processing.
34687 .section "Summary of Fields in Log Lines" "SECID258"
34688 .cindex "log" "summary of fields"
34689 A summary of the field identifiers that are used in log lines is shown in
34690 the following table:
34692 &`A `& authenticator name (and optional id and sender)
34693 &`C `& SMTP confirmation on delivery
34694 &` `& command list for &"no mail in SMTP session"&
34695 &`CV `& certificate verification status
34696 &`D `& duration of &"no mail in SMTP session"&
34697 &`DN `& distinguished name from peer certificate
34698 &`DT `& on &`=>`& lines: time taken for a delivery
34699 &`F `& sender address (on delivery lines)
34700 &`H `& host name and IP address
34701 &`I `& local interface used
34702 &`id `& message id for incoming message
34703 &`P `& on &`<=`& lines: protocol used
34704 &` `& on &`=>`& and &`**`& lines: return path
34705 &`QT `& on &`=>`& lines: time spent on queue so far
34706 &` `& on &"Completed"& lines: time spent on queue
34707 &`R `& on &`<=`& lines: reference for local bounce
34708 &` `& on &`=>`& &`**`& and &`==`& lines: router name
34709 &`S `& size of message
34710 &`SNI `& server name indication from TLS client hello
34711 &`ST `& shadow transport name
34712 &`T `& on &`<=`& lines: message subject (topic)
34713 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
34714 &`U `& local user or RFC 1413 identity
34715 &`X `& TLS cipher suite
34719 .section "Other log entries" "SECID259"
34720 Various other types of log entry are written from time to time. Most should be
34721 self-explanatory. Among the more common are:
34724 .cindex "retry" "time not reached"
34725 &'retry time not reached'&&~&~An address previously suffered a temporary error
34726 during routing or local delivery, and the time to retry has not yet arrived.
34727 This message is not written to an individual message log file unless it happens
34728 during the first delivery attempt.
34730 &'retry time not reached for any host'&&~&~An address previously suffered
34731 temporary errors during remote delivery, and the retry time has not yet arrived
34732 for any of the hosts to which it is routed.
34734 .cindex "spool directory" "file locked"
34735 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
34736 some other Exim process is already working on the message. This can be quite
34737 common if queue running processes are started at frequent intervals. The
34738 &'exiwhat'& utility script can be used to find out what Exim processes are
34741 .cindex "error" "ignored"
34742 &'error ignored'&&~&~There are several circumstances that give rise to this
34745 Exim failed to deliver a bounce message whose age was greater than
34746 &%ignore_bounce_errors_after%&. The bounce was discarded.
34748 A filter file set up a delivery using the &"noerror"& option, and the delivery
34749 failed. The delivery was discarded.
34751 A delivery set up by a router configured with
34752 . ==== As this is a nested list, any displays it contains must be indented
34753 . ==== as otherwise they are too far to the left.
34757 failed. The delivery was discarded.
34765 .section "Reducing or increasing what is logged" "SECTlogselector"
34766 .cindex "log" "selectors"
34767 By setting the &%log_selector%& global option, you can disable some of Exim's
34768 default logging, or you can request additional logging. The value of
34769 &%log_selector%& is made up of names preceded by plus or minus characters. For
34772 log_selector = +arguments -retry_defer
34774 The list of optional log items is in the following table, with the default
34775 selection marked by asterisks:
34777 &` 8bitmime `& received 8BITMIME status
34778 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
34779 &` address_rewrite `& address rewriting
34780 &` all_parents `& all parents in => lines
34781 &` arguments `& command line arguments
34782 &`*connection_reject `& connection rejections
34783 &`*delay_delivery `& immediate delivery delayed
34784 &` deliver_time `& time taken to perform delivery
34785 &` delivery_size `& add &`S=`&&'nnn'& to => lines
34786 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
34787 &`*etrn `& ETRN commands
34788 &`*host_lookup_failed `& as it says
34789 &` ident_timeout `& timeout for ident connection
34790 &` incoming_interface `& incoming interface on <= lines
34791 &` incoming_port `& incoming port on <= lines
34792 &`*lost_incoming_connection `& as it says (includes timeouts)
34793 &` outgoing_port `& add remote port to => lines
34794 &`*queue_run `& start and end queue runs
34795 &` queue_time `& time on queue for one recipient
34796 &` queue_time_overall `& time on queue for whole message
34797 &` pid `& Exim process id
34798 &` received_recipients `& recipients on <= lines
34799 &` received_sender `& sender on <= lines
34800 &`*rejected_header `& header contents on reject log
34801 &`*retry_defer `& &"retry time not reached"&
34802 &` return_path_on_delivery `& put return path on => and ** lines
34803 &` sender_on_delivery `& add sender to => lines
34804 &`*sender_verify_fail `& sender verification failures
34805 &`*size_reject `& rejection because too big
34806 &`*skip_delivery `& delivery skipped in a queue run
34807 &`*smtp_confirmation `& SMTP confirmation on => lines
34808 &` smtp_connection `& SMTP connections
34809 &` smtp_incomplete_transaction`& incomplete SMTP transactions
34810 &` smtp_mailauth `& AUTH argument to MAIL commands
34811 &` smtp_no_mail `& session with no MAIL commands
34812 &` smtp_protocol_error `& SMTP protocol errors
34813 &` smtp_syntax_error `& SMTP syntax errors
34814 &` subject `& contents of &'Subject:'& on <= lines
34815 &` tls_certificate_verified `& certificate verification status
34816 &`*tls_cipher `& TLS cipher suite on <= and => lines
34817 &` tls_peerdn `& TLS peer DN on <= and => lines
34818 &` tls_sni `& TLS SNI on <= lines
34819 &` unknown_in_list `& DNS lookup failed in list match
34821 &` all `& all of the above
34823 More details on each of these items follows:
34827 .cindex "log" "8BITMIME"
34828 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
34829 which may help in tracking down interoperability issues with ancient MTAs
34830 that are not 8bit clean. This is added to the &"<="& line, tagged with
34831 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
34832 &`7BIT`& and &`8BITMIME`& respectively.
34834 .cindex "&%warn%& ACL verb" "log when skipping"
34835 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
34836 its conditions cannot be evaluated, a log line to this effect is written if
34837 this log selector is set.
34839 .cindex "log" "rewriting"
34840 .cindex "rewriting" "logging"
34841 &%address_rewrite%&: This applies both to global rewrites and per-transport
34842 rewrites, but not to rewrites in filters run as an unprivileged user (because
34843 such users cannot access the log).
34845 .cindex "log" "full parentage"
34846 &%all_parents%&: Normally only the original and final addresses are logged on
34847 delivery lines; with this selector, intermediate parents are given in
34848 parentheses between them.
34850 .cindex "log" "Exim arguments"
34851 .cindex "Exim arguments, logging"
34852 &%arguments%&: This causes Exim to write the arguments with which it was called
34853 to the main log, preceded by the current working directory. This is a debugging
34854 feature, added to make it easier to find out how certain MUAs call
34855 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
34856 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
34857 that are empty or that contain white space are quoted. Non-printing characters
34858 are shown as escape sequences. This facility cannot log unrecognized arguments,
34859 because the arguments are checked before the configuration file is read. The
34860 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
34861 between the caller and Exim.
34863 .cindex "log" "connection rejections"
34864 &%connection_reject%&: A log entry is written whenever an incoming SMTP
34865 connection is rejected, for whatever reason.
34867 .cindex "log" "delayed delivery"
34868 .cindex "delayed delivery, logging"
34869 &%delay_delivery%&: A log entry is written whenever a delivery process is not
34870 started for an incoming message because the load is too high or too many
34871 messages were received on one connection. Logging does not occur if no delivery
34872 process is started because &%queue_only%& is set or &%-odq%& was used.
34874 .cindex "log" "delivery duration"
34875 &%deliver_time%&: For each delivery, the amount of real time it has taken to
34876 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
34878 .cindex "log" "message size on delivery"
34879 .cindex "size" "of message"
34880 &%delivery_size%&: For each delivery, the size of message delivered is added to
34881 the &"=>"& line, tagged with S=.
34883 .cindex "log" "dnslist defer"
34884 .cindex "DNS list" "logging defer"
34885 .cindex "black list (DNS)"
34886 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
34887 DNS black list suffers a temporary error.
34889 .cindex "log" "ETRN commands"
34890 .cindex "ETRN" "logging"
34891 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
34892 is run to determine whether or not it is actually accepted. An invalid ETRN
34893 command, or one received within a message transaction is not logged by this
34894 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
34896 .cindex "log" "host lookup failure"
34897 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
34898 any addresses, or when a lookup of an IP address fails to find a host name, a
34899 log line is written. This logging does not apply to direct DNS lookups when
34900 routing email addresses, but it does apply to &"byname"& lookups.
34902 .cindex "log" "ident timeout"
34903 .cindex "RFC 1413" "logging timeout"
34904 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
34905 client's ident port times out.
34907 .cindex "log" "incoming interface"
34908 .cindex "interface" "logging"
34909 &%incoming_interface%&: The interface on which a message was received is added
34910 to the &"<="& line as an IP address in square brackets, tagged by I= and
34911 followed by a colon and the port number. The local interface and port are also
34912 added to other SMTP log lines, for example &"SMTP connection from"&, and to
34915 .cindex "log" "incoming remote port"
34916 .cindex "port" "logging remote"
34917 .cindex "TCP/IP" "logging incoming remote port"
34918 .vindex "&$sender_fullhost$&"
34919 .vindex "&$sender_rcvhost$&"
34920 &%incoming_port%&: The remote port number from which a message was received is
34921 added to log entries and &'Received:'& header lines, following the IP address
34922 in square brackets, and separated from it by a colon. This is implemented by
34923 changing the value that is put in the &$sender_fullhost$& and
34924 &$sender_rcvhost$& variables. Recording the remote port number has become more
34925 important with the widening use of NAT (see RFC 2505).
34927 .cindex "log" "dropped connection"
34928 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
34929 connection is unexpectedly dropped.
34931 .cindex "log" "outgoing remote port"
34932 .cindex "port" "logging outgoint remote"
34933 .cindex "TCP/IP" "logging ougtoing remote port"
34934 &%outgoing_port%&: The remote port number is added to delivery log lines (those
34935 containing => tags) following the IP address. This option is not included in
34936 the default setting, because for most ordinary configurations, the remote port
34937 number is always 25 (the SMTP port).
34939 .cindex "log" "process ids in"
34940 .cindex "pid (process id)" "in log lines"
34941 &%pid%&: The current process id is added to every log line, in square brackets,
34942 immediately after the time and date.
34944 .cindex "log" "queue run"
34945 .cindex "queue runner" "logging"
34946 &%queue_run%&: The start and end of every queue run are logged.
34948 .cindex "log" "queue time"
34949 &%queue_time%&: The amount of time the message has been in the queue on the
34950 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
34951 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
34952 includes reception time as well as the delivery time for the current address.
34953 This means that it may be longer than the difference between the arrival and
34954 delivery log line times, because the arrival log line is not written until the
34955 message has been successfully received.
34957 &%queue_time_overall%&: The amount of time the message has been in the queue on
34958 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
34959 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
34960 message, so it includes reception time as well as the total delivery time.
34962 .cindex "log" "recipients"
34963 &%received_recipients%&: The recipients of a message are listed in the main log
34964 as soon as the message is received. The list appears at the end of the log line
34965 that is written when a message is received, preceded by the word &"for"&. The
34966 addresses are listed after they have been qualified, but before any rewriting
34968 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
34971 .cindex "log" "sender reception"
34972 &%received_sender%&: The unrewritten original sender of a message is added to
34973 the end of the log line that records the message's arrival, after the word
34974 &"from"& (before the recipients if &%received_recipients%& is also set).
34976 .cindex "log" "header lines for rejection"
34977 &%rejected_header%&: If a message's header has been received at the time a
34978 rejection is written to the reject log, the complete header is added to the
34979 log. Header logging can be turned off individually for messages that are
34980 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
34982 .cindex "log" "retry defer"
34983 &%retry_defer%&: A log line is written if a delivery is deferred because a
34984 retry time has not yet been reached. However, this &"retry time not reached"&
34985 message is always omitted from individual message logs after the first delivery
34988 .cindex "log" "return path"
34989 &%return_path_on_delivery%&: The return path that is being transmitted with
34990 the message is included in delivery and bounce lines, using the tag P=.
34991 This is omitted if no delivery actually happens, for example, if routing fails,
34992 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
34994 .cindex "log" "sender on delivery"
34995 &%sender_on_delivery%&: The message's sender address is added to every delivery
34996 and bounce line, tagged by F= (for &"from"&).
34997 This is the original sender that was received with the message; it is not
34998 necessarily the same as the outgoing return path.
35000 .cindex "log" "sender verify failure"
35001 &%sender_verify_fail%&: If this selector is unset, the separate log line that
35002 gives details of a sender verification failure is not written. Log lines for
35003 the rejection of SMTP commands contain just &"sender verify failed"&, so some
35006 .cindex "log" "size rejection"
35007 &%size_reject%&: A log line is written whenever a message is rejected because
35010 .cindex "log" "frozen messages; skipped"
35011 .cindex "frozen messages" "logging skipping"
35012 &%skip_delivery%&: A log line is written whenever a message is skipped during a
35013 queue run because it is frozen or because another process is already delivering
35015 .cindex "&""spool file is locked""&"
35016 The message that is written is &"spool file is locked"&.
35018 .cindex "log" "smtp confirmation"
35019 .cindex "SMTP" "logging confirmation"
35020 .cindex "LMTP" "logging confirmation"
35021 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
35022 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
35023 A number of MTAs (including Exim) return an identifying string in this
35026 .cindex "log" "SMTP connections"
35027 .cindex "SMTP" "logging connections"
35028 &%smtp_connection%&: A log line is written whenever an SMTP connection is
35029 established or closed, unless the connection is from a host that matches
35030 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
35031 only when the closure is unexpected.) This applies to connections from local
35032 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
35033 dropped in the middle of a message, a log line is always written, whether or
35034 not this selector is set, but otherwise nothing is written at the start and end
35035 of connections unless this selector is enabled.
35037 For TCP/IP connections to an Exim daemon, the current number of connections is
35038 included in the log message for each new connection, but note that the count is
35039 reset if the daemon is restarted.
35040 Also, because connections are closed (and the closure is logged) in
35041 subprocesses, the count may not include connections that have been closed but
35042 whose termination the daemon has not yet noticed. Thus, while it is possible to
35043 match up the opening and closing of connections in the log, the value of the
35044 logged counts may not be entirely accurate.
35046 .cindex "log" "SMTP transaction; incomplete"
35047 .cindex "SMTP" "logging incomplete transactions"
35048 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
35049 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
35050 and the message sender plus any accepted recipients are included in the log
35051 line. This can provide evidence of dictionary attacks.
35053 .cindex "log" "non-MAIL SMTP sessions"
35054 .cindex "MAIL" "logging session without"
35055 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
35056 connection terminates without having issued a MAIL command. This includes both
35057 the case when the connection is dropped, and the case when QUIT is used. It
35058 does not include cases where the connection is rejected right at the start (by
35059 an ACL, or because there are too many connections, or whatever). These cases
35060 already have their own log lines.
35062 The log line that is written contains the identity of the client in the usual
35063 way, followed by D= and a time, which records the duration of the connection.
35064 If the connection was authenticated, this fact is logged exactly as it is for
35065 an incoming message, with an A= item. If the connection was encrypted, CV=,
35066 DN=, and X= items may appear as they do for an incoming message, controlled by
35067 the same logging options.
35069 Finally, if any SMTP commands were issued during the connection, a C= item
35070 is added to the line, listing the commands that were used. For example,
35074 shows that the client issued QUIT straight after EHLO. If there were fewer
35075 than 20 commands, they are all listed. If there were more than 20 commands,
35076 the last 20 are listed, preceded by &"..."&. However, with the default
35077 setting of 10 for &%smtp_accep_max_nonmail%&, the connection will in any case
35078 have been aborted before 20 non-mail commands are processed.
35080 &%smtp_mailauth%&: A third subfield with the authenticated sender,
35081 colon-separated, is appended to the A= item for a message arrival or delivery
35082 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
35083 was accepted or used.
35085 .cindex "log" "SMTP protocol error"
35086 .cindex "SMTP" "logging protocol error"
35087 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
35088 encountered. Exim does not have perfect detection of all protocol errors
35089 because of transmission delays and the use of pipelining. If PIPELINING has
35090 been advertised to a client, an Exim server assumes that the client will use
35091 it, and therefore it does not count &"expected"& errors (for example, RCPT
35092 received after rejecting MAIL) as protocol errors.
35094 .cindex "SMTP" "logging syntax errors"
35095 .cindex "SMTP" "syntax errors; logging"
35096 .cindex "SMTP" "unknown command; logging"
35097 .cindex "log" "unknown SMTP command"
35098 .cindex "log" "SMTP syntax error"
35099 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
35100 encountered. An unrecognized command is treated as a syntax error. For an
35101 external connection, the host identity is given; for an internal connection
35102 using &%-bs%& the sender identification (normally the calling user) is given.
35104 .cindex "log" "subject"
35105 .cindex "subject, logging"
35106 &%subject%&: The subject of the message is added to the arrival log line,
35107 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
35108 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
35109 specifies whether characters with values greater than 127 should be logged
35110 unchanged, or whether they should be rendered as escape sequences.
35112 .cindex "log" "certificate verification"
35113 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
35114 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
35115 verified, and &`CV=no`& if not.
35117 .cindex "log" "TLS cipher"
35118 .cindex "TLS" "logging cipher"
35119 &%tls_cipher%&: When a message is sent or received over an encrypted
35120 connection, the cipher suite used is added to the log line, preceded by X=.
35122 .cindex "log" "TLS peer DN"
35123 .cindex "TLS" "logging peer DN"
35124 &%tls_peerdn%&: When a message is sent or received over an encrypted
35125 connection, and a certificate is supplied by the remote host, the peer DN is
35126 added to the log line, preceded by DN=.
35128 .cindex "log" "TLS SNI"
35129 .cindex "TLS" "logging SNI"
35130 &%tls_sni%&: When a message is received over an encrypted connection, and
35131 the remote host provided the Server Name Indication extension, the SNI is
35132 added to the log line, preceded by SNI=.
35134 .cindex "log" "DNS failure in list"
35135 &%unknown_in_list%&: This setting causes a log entry to be written when the
35136 result of a list match is failure because a DNS lookup failed.
35140 .section "Message log" "SECID260"
35141 .cindex "message" "log file for"
35142 .cindex "log" "message log; description of"
35143 .cindex "&_msglog_& directory"
35144 .oindex "&%preserve_message_logs%&"
35145 In addition to the general log files, Exim writes a log file for each message
35146 that it handles. The names of these per-message logs are the message ids, and
35147 they are kept in the &_msglog_& sub-directory of the spool directory. Each
35148 message log contains copies of the log lines that apply to the message. This
35149 makes it easier to inspect the status of an individual message without having
35150 to search the main log. A message log is deleted when processing of the message
35151 is complete, unless &%preserve_message_logs%& is set, but this should be used
35152 only with great care because they can fill up your disk very quickly.
35154 On a heavily loaded system, it may be desirable to disable the use of
35155 per-message logs, in order to reduce disk I/O. This can be done by setting the
35156 &%message_logs%& option false.
35162 . ////////////////////////////////////////////////////////////////////////////
35163 . ////////////////////////////////////////////////////////////////////////////
35165 .chapter "Exim utilities" "CHAPutils"
35166 .scindex IIDutils "utilities"
35167 A number of utility scripts and programs are supplied with Exim and are
35168 described in this chapter. There is also the Exim Monitor, which is covered in
35169 the next chapter. The utilities described here are:
35171 .itable none 0 0 3 7* left 15* left 40* left
35172 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
35173 "list what Exim processes are doing"
35174 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
35175 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
35176 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
35177 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
35179 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
35180 .irow &<<SECTmailstat>>& &'eximstats'& &&&
35181 "extract statistics from the log"
35182 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
35183 "check address acceptance from given IP"
35184 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
35185 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
35186 .irow &<<SECThindatmai>>& &'exim_dumpdb'& "dump a hints database"
35187 .irow &<<SECThindatmai>>& &'exim_tidydb'& "clean up a hints database"
35188 .irow &<<SECThindatmai>>& &'exim_fixdb'& "patch a hints database"
35189 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
35192 Another utility that might be of use to sites with many MTAs is Tom Kistner's
35193 &'exilog'&. It provides log visualizations across multiple Exim servers. See
35194 &url(http://duncanthrax.net/exilog/) for details.
35199 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
35200 .cindex "&'exiwhat'&"
35201 .cindex "process, querying"
35203 On operating systems that can restart a system call after receiving a signal
35204 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
35205 a line describing what it is doing to the file &_exim-process.info_& in the
35206 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
35207 processes it can find, having first emptied the file. It then waits for one
35208 second to allow the Exim processes to react before displaying the results. In
35209 order to run &'exiwhat'& successfully you have to have sufficient privilege to
35210 send the signal to the Exim processes, so it is normally run as root.
35212 &*Warning*&: This is not an efficient process. It is intended for occasional
35213 use by system administrators. It is not sensible, for example, to set up a
35214 script that sends SIGUSR1 signals to Exim processes at short intervals.
35217 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
35218 varies in different operating systems. Not only are different options used,
35219 but the format of the output is different. For this reason, there are some
35220 system configuration options that configure exactly how &'exiwhat'& works. If
35221 it doesn't seem to be working for you, check the following compile-time
35224 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
35225 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
35226 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
35227 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
35229 An example of typical output from &'exiwhat'& is
35231 164 daemon: -q1h, listening on port 25
35232 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
35233 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
35234 [10.19.42.42] (editor@ref.example)
35235 10592 handling incoming call from [192.168.243.242]
35236 10628 accepting a local non-SMTP message
35238 The first number in the output line is the process number. The third line has
35239 been split here, in order to fit it on the page.
35243 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
35244 .cindex "&'exiqgrep'&"
35245 .cindex "queue" "grepping"
35246 This utility is a Perl script contributed by Matt Hubbard. It runs
35250 or (in case &*-a*& switch is specified)
35254 The &*-C*& option is used to specify an alternate &_exim.conf_& which might
35255 contain alternate exim configuration the queue management might be using.
35257 to obtain a queue listing, and then greps the output to select messages
35258 that match given criteria. The following selection options are available:
35261 .vitem &*-f*&&~<&'regex'&>
35262 Match the sender address using a case-insensitive search. The field that is
35263 tested is enclosed in angle brackets, so you can test for bounce messages with
35267 .vitem &*-r*&&~<&'regex'&>
35268 Match a recipient address using a case-insensitve search. The field that is
35269 tested is not enclosed in angle brackets.
35271 .vitem &*-s*&&~<&'regex'&>
35272 Match against the size field.
35274 .vitem &*-y*&&~<&'seconds'&>
35275 Match messages that are younger than the given time.
35277 .vitem &*-o*&&~<&'seconds'&>
35278 Match messages that are older than the given time.
35281 Match only frozen messages.
35284 Match only non-frozen messages.
35287 The following options control the format of the output:
35291 Display only the count of matching messages.
35294 Long format &-- display the full message information as output by Exim. This is
35298 Display message ids only.
35301 Brief format &-- one line per message.
35304 Display messages in reverse order.
35307 Include delivered recipients in queue listing.
35310 There is one more option, &%-h%&, which outputs a list of options.
35314 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
35315 .cindex "&'exiqsumm'&"
35316 .cindex "queue" "summary"
35317 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
35318 -bp`& and produces a summary of the messages on the queue. Thus, you use it by
35319 running a command such as
35321 exim -bp | exiqsumm
35323 The output consists of one line for each domain that has messages waiting for
35324 it, as in the following example:
35326 3 2322 74m 66m msn.com.example
35328 Each line lists the number of pending deliveries for a domain, their total
35329 volume, and the length of time that the oldest and the newest messages have
35330 been waiting. Note that the number of pending deliveries is greater than the
35331 number of messages when messages have more than one recipient.
35333 A summary line is output at the end. By default the output is sorted on the
35334 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
35335 the output to be sorted by oldest message and by count of messages,
35336 respectively. There are also three options that split the messages for each
35337 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
35338 separates frozen messages, and &%-s%& separates messages according to their
35341 The output of &'exim -bp'& contains the original addresses in the message, so
35342 this also applies to the output from &'exiqsumm'&. No domains from addresses
35343 generated by aliasing or forwarding are included (unless the &%one_time%&
35344 option of the &(redirect)& router has been used to convert them into &"top
35345 level"& addresses).
35350 .section "Extracting specific information from the log (exigrep)" &&&
35352 .cindex "&'exigrep'&"
35353 .cindex "log" "extracts; grepping for"
35354 The &'exigrep'& utility is a Perl script that searches one or more main log
35355 files for entries that match a given pattern. When it finds a match, it
35356 extracts all the log entries for the relevant message, not just those that
35357 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
35358 given message, or all mail for a given user, or for a given host, for example.
35359 The input files can be in Exim log format or syslog format.
35360 If a matching log line is not associated with a specific message, it is
35361 included in &'exigrep'&'s output without any additional lines. The usage is:
35364 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
35367 If no log file names are given on the command line, the standard input is read.
35369 The &%-t%& argument specifies a number of seconds. It adds an additional
35370 condition for message selection. Messages that are complete are shown only if
35371 they spent more than <&'n'&> seconds on the queue.
35373 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
35374 makes it case-sensitive. This may give a performance improvement when searching
35375 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
35376 option; with &%-I%& they do not. In both cases it is possible to change the
35377 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
35379 The &%-l%& option means &"literal"&, that is, treat all characters in the
35380 pattern as standing for themselves. Otherwise the pattern must be a Perl
35381 regular expression.
35383 The &%-v%& option inverts the matching condition. That is, a line is selected
35384 if it does &'not'& match the pattern.
35387 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
35388 that are generated as a result/response to a message that &'exigrep'& matched
35392 user_a sends a message to user_b, which generates a bounce back to user_b. If
35393 &'exigrep'& is used to search for &"user_a"&, only the first message will be
35394 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
35395 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
35396 when searching for &"user_a"& will show both messages since the bounce is
35397 &"related"& to or a &"result"& of the first message that was found by the
35401 If the location of a &'zcat'& command is known from the definition of
35402 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
35403 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
35406 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
35407 .cindex "&'exipick'&"
35408 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
35409 lists messages from the queue according to a variety of criteria. For details
35410 of &'exipick'&'s facilities, visit the web page at
35411 &url(http://www.exim.org/eximwiki/ToolExipickManPage) or run &'exipick'& with
35412 the &%--help%& option.
35415 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
35416 .cindex "log" "cycling local files"
35417 .cindex "cycling logs"
35418 .cindex "&'exicyclog'&"
35419 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
35420 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
35421 you are using log files with datestamps in their names (see section
35422 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
35423 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
35424 There are two command line options for &'exicyclog'&:
35426 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
35427 default that is set when Exim is built. The default default is 10.
35429 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
35430 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
35431 overriding the script's default, which is to find the setting from Exim's
35435 Each time &'exicyclog'& is run the file names get &"shuffled down"& by one. If
35436 the main log file name is &_mainlog_& (the default) then when &'exicyclog'& is
35437 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
35438 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
35439 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
35440 logs are handled similarly.
35442 If the limit is greater than 99, the script uses 3-digit numbers such as
35443 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
35444 to one that is greater, or &'vice versa'&, you will have to fix the names of
35445 any existing log files.
35447 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
35448 the end are deleted. All files with numbers greater than 01 are compressed,
35449 using a compression command which is configured by the COMPRESS_COMMAND
35450 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
35451 root &%crontab%& entry of the form
35453 1 0 * * * su exim -c /usr/exim/bin/exicyclog
35455 assuming you have used the name &"exim"& for the Exim user. You can run
35456 &'exicyclog'& as root if you wish, but there is no need.
35460 .section "Mail statistics (eximstats)" "SECTmailstat"
35461 .cindex "statistics"
35462 .cindex "&'eximstats'&"
35463 A Perl script called &'eximstats'& is provided for extracting statistical
35464 information from log files. The output is either plain text, or HTML.
35465 Exim log files are also supported by the &'Lire'& system produced by the
35466 LogReport Foundation &url(http://www.logreport.org).
35468 The &'eximstats'& script has been hacked about quite a bit over time. The
35469 latest version is the result of some extensive revision by Steve Campbell. A
35470 lot of information is given by default, but there are options for suppressing
35471 various parts of it. Following any options, the arguments to the script are a
35472 list of files, which should be main log files. For example:
35474 eximstats -nr /var/spool/exim/log/mainlog.01
35476 By default, &'eximstats'& extracts information about the number and volume of
35477 messages received from or delivered to various hosts. The information is sorted
35478 both by message count and by volume, and the top fifty hosts in each category
35479 are listed on the standard output. Similar information, based on email
35480 addresses or domains instead of hosts can be requested by means of various
35481 options. For messages delivered and received locally, similar statistics are
35482 also produced per user.
35484 The output also includes total counts and statistics about delivery errors, and
35485 histograms showing the number of messages received and deliveries made in each
35486 hour of the day. A delivery with more than one address in its envelope (for
35487 example, an SMTP transaction with more than one RCPT command) is counted
35488 as a single delivery by &'eximstats'&.
35490 Though normally more deliveries than receipts are reported (as messages may
35491 have multiple recipients), it is possible for &'eximstats'& to report more
35492 messages received than delivered, even though the queue is empty at the start
35493 and end of the period in question. If an incoming message contains no valid
35494 recipients, no deliveries are recorded for it. A bounce message is handled as
35495 an entirely separate message.
35497 &'eximstats'& always outputs a grand total summary giving the volume and number
35498 of messages received and deliveries made, and the number of hosts involved in
35499 each case. It also outputs the number of messages that were delayed (that is,
35500 not completely delivered at the first attempt), and the number that had at
35501 least one address that failed.
35503 The remainder of the output is in sections that can be independently disabled
35504 or modified by various options. It consists of a summary of deliveries by
35505 transport, histograms of messages received and delivered per time interval
35506 (default per hour), information about the time messages spent on the queue,
35507 a list of relayed messages, lists of the top fifty sending hosts, local
35508 senders, destination hosts, and destination local users by count and by volume,
35509 and a list of delivery errors that occurred.
35511 The relay information lists messages that were actually relayed, that is, they
35512 came from a remote host and were directly delivered to some other remote host,
35513 without being processed (for example, for aliasing or forwarding) locally.
35515 There are quite a few options for &'eximstats'& to control exactly what it
35516 outputs. These are documented in the Perl script itself, and can be extracted
35517 by running the command &(perldoc)& on the script. For example:
35519 perldoc /usr/exim/bin/eximstats
35522 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
35523 .cindex "&'exim_checkaccess'&"
35524 .cindex "policy control" "checking access"
35525 .cindex "checking access"
35526 The &%-bh%& command line argument allows you to run a fake SMTP session with
35527 debugging output, in order to check what Exim is doing when it is applying
35528 policy controls to incoming SMTP mail. However, not everybody is sufficiently
35529 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
35530 sometimes you just want to answer the question &"Does this address have
35531 access?"& without bothering with any further details.
35533 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
35534 two arguments, an IP address and an email address:
35536 exim_checkaccess 10.9.8.7 A.User@a.domain.example
35538 The utility runs a call to Exim with the &%-bh%& option, to test whether the
35539 given email address would be accepted in a RCPT command in a TCP/IP
35540 connection from the host with the given IP address. The output of the utility
35541 is either the word &"accepted"&, or the SMTP error response, for example:
35544 550 Relay not permitted
35546 When running this test, the utility uses &`<>`& as the envelope sender address
35547 for the MAIL command, but you can change this by providing additional
35548 options. These are passed directly to the Exim command. For example, to specify
35549 that the test is to be run with the sender address &'himself@there.example'&
35552 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
35553 -f himself@there.example
35555 Note that these additional Exim command line items must be given after the two
35556 mandatory arguments.
35558 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
35559 while running its checks. You can run checks that include callouts by using
35560 &%-bhc%&, but this is not yet available in a &"packaged"& form.
35564 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
35565 .cindex "DBM" "building dbm files"
35566 .cindex "building DBM files"
35567 .cindex "&'exim_dbmbuild'&"
35568 .cindex "lower casing"
35569 .cindex "binary zero" "in lookup key"
35570 The &'exim_dbmbuild'& program reads an input file containing keys and data in
35571 the format used by the &(lsearch)& lookup (see section
35572 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
35573 names as keys and the remainder of the information as data. The lower-casing
35574 can be prevented by calling the program with the &%-nolc%& option.
35576 A terminating zero is included as part of the key string. This is expected by
35577 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
35578 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
35579 strings or the data strings. The &(dbmnz)& lookup type can be used with such
35582 The program requires two arguments: the name of the input file (which can be a
35583 single hyphen to indicate the standard input), and the name of the output file.
35584 It creates the output under a temporary name, and then renames it if all went
35588 If the native DB interface is in use (USE_DB is set in a compile-time
35589 configuration file &-- this is common in free versions of Unix) the two file
35590 names must be different, because in this mode the Berkeley DB functions create
35591 a single output file using exactly the name given. For example,
35593 exim_dbmbuild /etc/aliases /etc/aliases.db
35595 reads the system alias file and creates a DBM version of it in
35596 &_/etc/aliases.db_&.
35598 In systems that use the &'ndbm'& routines (mostly proprietary versions of
35599 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
35600 environment, the suffixes are added to the second argument of
35601 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
35602 when the Berkeley functions are used in compatibility mode (though this is not
35603 recommended), because in that case it adds a &_.db_& suffix to the file name.
35605 If a duplicate key is encountered, the program outputs a warning, and when it
35606 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
35607 option is used. By default, only the first of a set of duplicates is used &--
35608 this makes it compatible with &(lsearch)& lookups. There is an option
35609 &%-lastdup%& which causes it to use the data for the last duplicate instead.
35610 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
35611 &%stderr%&. For other errors, where it doesn't actually make a new file, the
35617 .section "Finding individual retry times (exinext)" "SECTfinindret"
35618 .cindex "retry" "times"
35619 .cindex "&'exinext'&"
35620 A utility called &'exinext'& (mostly a Perl script) provides the ability to
35621 fish specific information out of the retry database. Given a mail domain (or a
35622 complete address), it looks up the hosts for that domain, and outputs any retry
35623 information for the hosts or for the domain. At present, the retry information
35624 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
35625 output. For example:
35627 $ exinext piglet@milne.fict.example
35628 kanga.milne.example:192.168.8.1 error 146: Connection refused
35629 first failed: 21-Feb-1996 14:57:34
35630 last tried: 21-Feb-1996 14:57:34
35631 next try at: 21-Feb-1996 15:02:34
35632 roo.milne.example:192.168.8.3 error 146: Connection refused
35633 first failed: 20-Jan-1996 13:12:08
35634 last tried: 21-Feb-1996 11:42:03
35635 next try at: 21-Feb-1996 19:42:03
35636 past final cutoff time
35638 You can also give &'exinext'& a local part, without a domain, and it
35639 will give any retry information for that local part in your default domain.
35640 A message id can be used to obtain retry information pertaining to a specific
35641 message. This exists only when an attempt to deliver a message to a remote host
35642 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
35643 &'exinext'& is not particularly efficient, but then it is not expected to be
35646 The &'exinext'& utility calls Exim to find out information such as the location
35647 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
35648 passed on to the &'exim'& commands. The first specifies an alternate Exim
35649 configuration file, and the second sets macros for use within the configuration
35650 file. These features are mainly to help in testing, but might also be useful in
35651 environments where more than one configuration file is in use.
35655 .section "Hints database maintenance" "SECThindatmai"
35656 .cindex "hints database" "maintenance"
35657 .cindex "maintaining Exim's hints database"
35658 Three utility programs are provided for maintaining the DBM files that Exim
35659 uses to contain its delivery hint information. Each program requires two
35660 arguments. The first specifies the name of Exim's spool directory, and the
35661 second is the name of the database it is to operate on. These are as follows:
35664 &'retry'&: the database of retry information
35666 &'wait-'&<&'transport name'&>: databases of information about messages waiting
35669 &'callout'&: the callout cache
35671 &'ratelimit'&: the data for implementing the ratelimit ACL condition
35673 &'misc'&: other hints data
35676 The &'misc'& database is used for
35679 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
35681 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
35682 &(smtp)& transport)
35687 .section "exim_dumpdb" "SECID261"
35688 .cindex "&'exim_dumpdb'&"
35689 The entire contents of a database are written to the standard output by the
35690 &'exim_dumpdb'& program, which has no options or arguments other than the
35691 spool and database names. For example, to dump the retry database:
35693 exim_dumpdb /var/spool/exim retry
35695 Two lines of output are produced for each entry:
35697 T:mail.ref.example:192.168.242.242 146 77 Connection refused
35698 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
35700 The first item on the first line is the key of the record. It starts with one
35701 of the letters R, or T, depending on whether it refers to a routing or
35702 transport retry. For a local delivery, the next part is the local address; for
35703 a remote delivery it is the name of the remote host, followed by its failing IP
35704 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
35705 transport). If the remote port is not the standard one (port 25), it is added
35706 to the IP address. Then there follows an error code, an additional error code,
35707 and a textual description of the error.
35709 The three times on the second line are the time of first failure, the time of
35710 the last delivery attempt, and the computed time for the next attempt. The line
35711 ends with an asterisk if the cutoff time for the last retry rule has been
35714 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
35715 consists of a host name followed by a list of ids for messages that are or were
35716 waiting to be delivered to that host. If there are a very large number for any
35717 one host, continuation records, with a sequence number added to the host name,
35718 may be seen. The data in these records is often out of date, because a message
35719 may be routed to several alternative hosts, and Exim makes no effort to keep
35724 .section "exim_tidydb" "SECID262"
35725 .cindex "&'exim_tidydb'&"
35726 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
35727 database. If run with no options, it removes all records that are more than 30
35728 days old. The age is calculated from the date and time that the record was last
35729 updated. Note that, in the case of the retry database, it is &'not'& the time
35730 since the first delivery failure. Information about a host that has been down
35731 for more than 30 days will remain in the database, provided that the record is
35732 updated sufficiently often.
35734 The cutoff date can be altered by means of the &%-t%& option, which must be
35735 followed by a time. For example, to remove all records older than a week from
35736 the retry database:
35738 exim_tidydb -t 7d /var/spool/exim retry
35740 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
35741 message ids. In the former these appear as data in records keyed by host &--
35742 they were messages that were waiting for that host &-- and in the latter they
35743 are the keys for retry information for messages that have suffered certain
35744 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
35745 message ids in database records are those of messages that are still on the
35746 queue. Message ids for messages that no longer exist are removed from
35747 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
35748 For the &'retry'& database, records whose keys are non-existent message ids are
35749 removed. The &'exim_tidydb'& utility outputs comments on the standard output
35750 whenever it removes information from the database.
35752 Certain records are automatically removed by Exim when they are no longer
35753 needed, but others are not. For example, if all the MX hosts for a domain are
35754 down, a retry record is created for each one. If the primary MX host comes back
35755 first, its record is removed when Exim successfully delivers to it, but the
35756 records for the others remain because Exim has not tried to use those hosts.
35758 It is important, therefore, to run &'exim_tidydb'& periodically on all the
35759 hints databases. You should do this at a quiet time of day, because it requires
35760 a database to be locked (and therefore inaccessible to Exim) while it does its
35761 work. Removing records from a DBM file does not normally make the file smaller,
35762 but all the common DBM libraries are able to re-use the space that is released.
35763 After an initial phase of increasing in size, the databases normally reach a
35764 point at which they no longer get any bigger, as long as they are regularly
35767 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
35768 databases is likely to keep on increasing.
35773 .section "exim_fixdb" "SECID263"
35774 .cindex "&'exim_fixdb'&"
35775 The &'exim_fixdb'& program is a utility for interactively modifying databases.
35776 Its main use is for testing Exim, but it might also be occasionally useful for
35777 getting round problems in a live system. It has no options, and its interface
35778 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
35779 key of a database record can then be entered, and the data for that record is
35782 If &"d"& is typed at the next prompt, the entire record is deleted. For all
35783 except the &'retry'& database, that is the only operation that can be carried
35784 out. For the &'retry'& database, each field is output preceded by a number, and
35785 data for individual fields can be changed by typing the field number followed
35786 by new data, for example:
35790 resets the time of the next delivery attempt. Time values are given as a
35791 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
35792 used as optional separators.
35797 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
35798 .cindex "mailbox" "maintenance"
35799 .cindex "&'exim_lock'&"
35800 .cindex "locking mailboxes"
35801 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
35802 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
35803 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
35804 a user agent while investigating a problem. The utility requires the name of
35805 the file as its first argument. If the locking is successful, the second
35806 argument is run as a command (using C's &[system()]& function); if there is no
35807 second argument, the value of the SHELL environment variable is used; if this
35808 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
35809 is unlocked and the utility ends. The following options are available:
35813 Use &[fcntl()]& locking on the open mailbox.
35816 Use &[flock()]& locking on the open mailbox, provided the operating system
35819 .vitem &%-interval%&
35820 This must be followed by a number, which is a number of seconds; it sets the
35821 interval to sleep between retries (default 3).
35823 .vitem &%-lockfile%&
35824 Create a lock file before opening the mailbox.
35827 Lock the mailbox using MBX rules.
35830 Suppress verification output.
35832 .vitem &%-retries%&
35833 This must be followed by a number; it sets the number of times to try to get
35834 the lock (default 10).
35836 .vitem &%-restore_time%&
35837 This option causes &%exim_lock%& to restore the modified and read times to the
35838 locked file before exiting. This allows you to access a locked mailbox (for
35839 example, to take a backup copy) without disturbing the times that the user
35842 .vitem &%-timeout%&
35843 This must be followed by a number, which is a number of seconds; it sets a
35844 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
35845 default), a non-blocking call is used.
35848 Generate verbose output.
35851 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
35852 default is to create a lock file and also to use &[fcntl()]& locking on the
35853 mailbox, which is the same as Exim's default. The use of &%-flock%& or
35854 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
35855 requires that the directory containing the file be writeable. Locking by lock
35856 file does not last for ever; Exim assumes that a lock file is expired if it is
35857 more than 30 minutes old.
35859 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
35860 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
35861 to be taken out on the open mailbox, and an exclusive lock on the file
35862 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
35863 number of the mailbox file. When the locking is released, if an exclusive lock
35864 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
35866 The default output contains verification of the locking that takes place. The
35867 &%-v%& option causes some additional information to be given. The &%-q%& option
35868 suppresses all output except error messages.
35872 exim_lock /var/spool/mail/spqr
35874 runs an interactive shell while the file is locked, whereas
35876 &`exim_lock -q /var/spool/mail/spqr <<End`&
35877 <&'some commands'&>
35880 runs a specific non-interactive sequence of commands while the file is locked,
35881 suppressing all verification output. A single command can be run by a command
35884 exim_lock -q /var/spool/mail/spqr \
35885 "cp /var/spool/mail/spqr /some/where"
35887 Note that if a command is supplied, it must be entirely contained within the
35888 second argument &-- hence the quotes.
35892 . ////////////////////////////////////////////////////////////////////////////
35893 . ////////////////////////////////////////////////////////////////////////////
35895 .chapter "The Exim monitor" "CHAPeximon"
35896 .scindex IIDeximon "Exim monitor" "description"
35897 .cindex "X-windows"
35898 .cindex "&'eximon'&"
35899 .cindex "Local/eximon.conf"
35900 .cindex "&_exim_monitor/EDITME_&"
35901 The Exim monitor is an application which displays in an X window information
35902 about the state of Exim's queue and what Exim is doing. An admin user can
35903 perform certain operations on messages from this GUI interface; however all
35904 such facilities are also available from the command line, and indeed, the
35905 monitor itself makes use of the command line to perform any actions requested.
35909 .section "Running the monitor" "SECID264"
35910 The monitor is started by running the script called &'eximon'&. This is a shell
35911 script that sets up a number of environment variables, and then runs the
35912 binary called &_eximon.bin_&. The default appearance of the monitor window can
35913 be changed by editing the &_Local/eximon.conf_& file created by editing
35914 &_exim_monitor/EDITME_&. Comments in that file describe what the various
35915 parameters are for.
35917 The parameters that get built into the &'eximon'& script can be overridden for
35918 a particular invocation by setting up environment variables of the same names,
35919 preceded by &`EXIMON_`&. For example, a shell command such as
35921 EXIMON_LOG_DEPTH=400 eximon
35923 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
35924 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
35925 overrides the Exim log file configuration. This makes it possible to have
35926 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
35927 syslog messages are routed to a file on the local host.
35929 X resources can be used to change the appearance of the window in the normal
35930 way. For example, a resource setting of the form
35932 Eximon*background: gray94
35934 changes the colour of the background to light grey rather than white. The
35935 stripcharts are drawn with both the data lines and the reference lines in
35936 black. This means that the reference lines are not visible when on top of the
35937 data. However, their colour can be changed by setting a resource called
35938 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
35939 For example, if your X server is running Unix, you could set up lighter
35940 reference lines in the stripcharts by obeying
35943 Eximon*highlight: gray
35946 .cindex "admin user"
35947 In order to see the contents of messages on the queue, and to operate on them,
35948 &'eximon'& must either be run as root or by an admin user.
35950 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
35951 contain X11 resource parameters interpreted by the X11 library. In addition,
35952 if the first parameter starts with the string "gdb" then it is removed and the
35953 binary is invoked under gdb (the parameter is used as the gdb command-name, so
35954 versioned variants of gdb can be invoked).
35956 The monitor's window is divided into three parts. The first contains one or
35957 more stripcharts and two action buttons, the second contains a &"tail"& of the
35958 main log file, and the third is a display of the queue of messages awaiting
35959 delivery, with two more action buttons. The following sections describe these
35960 different parts of the display.
35965 .section "The stripcharts" "SECID265"
35966 .cindex "stripchart"
35967 The first stripchart is always a count of messages on the queue. Its name can
35968 be configured by setting QUEUE_STRIPCHART_NAME in the
35969 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
35970 configuration script by regular expression matches on log file entries, making
35971 it possible to display, for example, counts of messages delivered to certain
35972 hosts or using certain transports. The supplied defaults display counts of
35973 received and delivered messages, and of local and SMTP deliveries. The default
35974 period between stripchart updates is one minute; this can be adjusted by a
35975 parameter in the &_Local/eximon.conf_& file.
35977 The stripchart displays rescale themselves automatically as the value they are
35978 displaying changes. There are always 10 horizontal lines in each chart; the
35979 title string indicates the value of each division when it is greater than one.
35980 For example, &"x2"& means that each division represents a value of 2.
35982 It is also possible to have a stripchart which shows the percentage fullness of
35983 a particular disk partition, which is useful when local deliveries are confined
35984 to a single partition.
35986 .cindex "&%statvfs%& function"
35987 This relies on the availability of the &[statvfs()]& function or equivalent in
35988 the operating system. Most, but not all versions of Unix that support Exim have
35989 this. For this particular stripchart, the top of the chart always represents
35990 100%, and the scale is given as &"x10%"&. This chart is configured by setting
35991 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
35992 &_Local/eximon.conf_& file.
35997 .section "Main action buttons" "SECID266"
35998 .cindex "size" "of monitor window"
35999 .cindex "Exim monitor" "window size"
36000 .cindex "window size"
36001 Below the stripcharts there is an action button for quitting the monitor. Next
36002 to this is another button marked &"Size"&. They are placed here so that
36003 shrinking the window to its default minimum size leaves just the queue count
36004 stripchart and these two buttons visible. Pressing the &"Size"& button causes
36005 the window to expand to its maximum size, unless it is already at the maximum,
36006 in which case it is reduced to its minimum.
36008 When expanding to the maximum, if the window cannot be fully seen where it
36009 currently is, it is moved back to where it was the last time it was at full
36010 size. When it is expanding from its minimum size, the old position is
36011 remembered, and next time it is reduced to the minimum it is moved back there.
36013 The idea is that you can keep a reduced window just showing one or two
36014 stripcharts at a convenient place on your screen, easily expand it to show
36015 the full window when required, and just as easily put it back to what it was.
36016 The idea is copied from what the &'twm'& window manager does for its
36017 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
36018 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
36020 Normally, the monitor starts up with the window at its full size, but it can be
36021 built so that it starts up with the window at its smallest size, by setting
36022 START_SMALL=yes in &_Local/eximon.conf_&.
36026 .section "The log display" "SECID267"
36027 .cindex "log" "tail of; in monitor"
36028 The second section of the window is an area in which a display of the tail of
36029 the main log is maintained.
36030 To save space on the screen, the timestamp on each log line is shortened by
36031 removing the date and, if &%log_timezone%& is set, the timezone.
36032 The log tail is not available when the only destination for logging data is
36033 syslog, unless the syslog lines are routed to a local file whose name is passed
36034 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
36036 The log sub-window has a scroll bar at its lefthand side which can be used to
36037 move back to look at earlier text, and the up and down arrow keys also have a
36038 scrolling effect. The amount of log that is kept depends on the setting of
36039 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
36040 to use. When this is full, the earlier 50% of data is discarded &-- this is
36041 much more efficient than throwing it away line by line. The sub-window also has
36042 a horizontal scroll bar for accessing the ends of long log lines. This is the
36043 only means of horizontal scrolling; the right and left arrow keys are not
36044 available. Text can be cut from this part of the window using the mouse in the
36045 normal way. The size of this subwindow is controlled by parameters in the
36046 configuration file &_Local/eximon.conf_&.
36048 Searches of the text in the log window can be carried out by means of the ^R
36049 and ^S keystrokes, which default to a reverse and a forward search,
36050 respectively. The search covers only the text that is displayed in the window.
36051 It cannot go further back up the log.
36053 The point from which the search starts is indicated by a caret marker. This is
36054 normally at the end of the text in the window, but can be positioned explicitly
36055 by pointing and clicking with the left mouse button, and is moved automatically
36056 by a successful search. If new text arrives in the window when it is scrolled
36057 back, the caret remains where it is, but if the window is not scrolled back,
36058 the caret is moved to the end of the new text.
36060 Pressing ^R or ^S pops up a window into which the search text can be typed.
36061 There are buttons for selecting forward or reverse searching, for carrying out
36062 the search, and for cancelling. If the &"Search"& button is pressed, the search
36063 happens and the window remains so that further searches can be done. If the
36064 &"Return"& key is pressed, a single search is done and the window is closed. If
36065 ^C is typed the search is cancelled.
36067 The searching facility is implemented using the facilities of the Athena text
36068 widget. By default this pops up a window containing both &"search"& and
36069 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
36070 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
36071 However, the linkers in BSDI and HP-UX seem unable to handle an externally
36072 provided version of &%TextPop%& when the remaining parts of the text widget
36073 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
36074 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
36075 on these systems, at the expense of having unwanted items in the search popup
36080 .section "The queue display" "SECID268"
36081 .cindex "queue" "display in monitor"
36082 The bottom section of the monitor window contains a list of all messages that
36083 are on the queue, which includes those currently being received or delivered,
36084 as well as those awaiting delivery. The size of this subwindow is controlled by
36085 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
36086 at which it is updated is controlled by another parameter in the same file &--
36087 the default is 5 minutes, since queue scans can be quite expensive. However,
36088 there is an &"Update"& action button just above the display which can be used
36089 to force an update of the queue display at any time.
36091 When a host is down for some time, a lot of pending mail can build up for it,
36092 and this can make it hard to deal with other messages on the queue. To help
36093 with this situation there is a button next to &"Update"& called &"Hide"&. If
36094 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
36095 type anything in here and press &"Return"&, the text is added to a chain of
36096 such texts, and if every undelivered address in a message matches at least one
36097 of the texts, the message is not displayed.
36099 If there is an address that does not match any of the texts, all the addresses
36100 are displayed as normal. The matching happens on the ends of addresses so, for
36101 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
36102 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
36103 has been set up, a button called &"Unhide"& is displayed. If pressed, it
36104 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
36105 a hide request is automatically cancelled after one hour.
36107 While the dialogue box is displayed, you can't press any buttons or do anything
36108 else to the monitor window. For this reason, if you want to cut text from the
36109 queue display to use in the dialogue box, you have to do the cutting before
36110 pressing the &"Hide"& button.
36112 The queue display contains, for each unhidden queued message, the length of
36113 time it has been on the queue, the size of the message, the message id, the
36114 message sender, and the first undelivered recipient, all on one line. If it is
36115 a bounce message, the sender is shown as &"<>"&. If there is more than one
36116 recipient to which the message has not yet been delivered, subsequent ones are
36117 listed on additional lines, up to a maximum configured number, following which
36118 an ellipsis is displayed. Recipients that have already received the message are
36121 .cindex "frozen messages" "display"
36122 If a message is frozen, an asterisk is displayed at the left-hand side.
36124 The queue display has a vertical scroll bar, and can also be scrolled by means
36125 of the arrow keys. Text can be cut from it using the mouse in the normal way.
36126 The text searching facilities, as described above for the log window, are also
36127 available, but the caret is always moved to the end of the text when the queue
36128 display is updated.
36132 .section "The queue menu" "SECID269"
36133 .cindex "queue" "menu in monitor"
36134 If the &%shift%& key is held down and the left button is clicked when the mouse
36135 pointer is over the text for any message, an action menu pops up, and the first
36136 line of the queue display for the message is highlighted. This does not affect
36139 If you want to use some other event for popping up the menu, you can set the
36140 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
36141 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
36142 value set in this parameter is a standard X event description. For example, to
36143 run eximon using &%ctrl%& rather than &%shift%& you could use
36145 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
36147 The title of the menu is the message id, and it contains entries which act as
36151 &'message log'&: The contents of the message log for the message are displayed
36152 in a new text window.
36154 &'headers'&: Information from the spool file that contains the envelope
36155 information and headers is displayed in a new text window. See chapter
36156 &<<CHAPspool>>& for a description of the format of spool files.
36158 &'body'&: The contents of the spool file containing the body of the message are
36159 displayed in a new text window. There is a default limit of 20,000 bytes to the
36160 amount of data displayed. This can be changed by setting the BODY_MAX
36161 option at compile time, or the EXIMON_BODY_MAX option at run time.
36163 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
36164 delivery of the message. This causes an automatic thaw if the message is
36165 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
36166 a new text window. The delivery is run in a separate process, to avoid holding
36167 up the monitor while the delivery proceeds.
36169 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
36170 that the message be frozen.
36172 .cindex "thawing messages"
36173 .cindex "unfreezing messages"
36174 .cindex "frozen messages" "thawing"
36175 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
36176 that the message be thawed.
36178 .cindex "delivery" "forcing failure"
36179 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
36180 that Exim gives up trying to deliver the message. A bounce message is generated
36181 for any remaining undelivered addresses.
36183 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
36184 that the message be deleted from the system without generating a bounce
36187 &'add recipient'&: A dialog box is displayed into which a recipient address can
36188 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
36189 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
36190 Otherwise it must be entered as a fully qualified address. Pressing RETURN
36191 causes a call to Exim to be made using the &%-Mar%& option to request that an
36192 additional recipient be added to the message, unless the entry box is empty, in
36193 which case no action is taken.
36195 &'mark delivered'&: A dialog box is displayed into which a recipient address
36196 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
36197 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
36198 Otherwise it must be entered as a fully qualified address. Pressing RETURN
36199 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
36200 recipient address as already delivered, unless the entry box is empty, in which
36201 case no action is taken.
36203 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
36204 mark all recipient addresses as already delivered.
36206 &'edit sender'&: A dialog box is displayed initialized with the current
36207 sender's address. Pressing RETURN causes a call to Exim to be made using the
36208 &%-Mes%& option to replace the sender address, unless the entry box is empty,
36209 in which case no action is taken. If you want to set an empty sender (as in
36210 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
36211 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
36212 the address is qualified with that domain.
36215 When a delivery is forced, a window showing the &%-v%& output is displayed. In
36216 other cases when a call to Exim is made, if there is any output from Exim (in
36217 particular, if the command fails) a window containing the command and the
36218 output is displayed. Otherwise, the results of the action are normally apparent
36219 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
36220 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
36221 if no output is generated.
36223 The queue display is automatically updated for actions such as freezing and
36224 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
36225 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
36226 force an update of the display after one of these actions.
36228 In any text window that is displayed as result of a menu action, the normal
36229 cut-and-paste facility is available, and searching can be carried out using ^R
36230 and ^S, as described above for the log tail window.
36237 . ////////////////////////////////////////////////////////////////////////////
36238 . ////////////////////////////////////////////////////////////////////////////
36240 .chapter "Security considerations" "CHAPsecurity"
36241 .scindex IIDsecurcon "security" "discussion of"
36242 This chapter discusses a number of issues concerned with security, some of
36243 which are also covered in other parts of this manual.
36245 For reasons that this author does not understand, some people have promoted
36246 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
36247 existence of this chapter in the documentation. However, the intent of the
36248 chapter is simply to describe the way Exim works in relation to certain
36249 security concerns, not to make any specific claims about the effectiveness of
36250 its security as compared with other MTAs.
36252 What follows is a description of the way Exim is supposed to be. Best efforts
36253 have been made to try to ensure that the code agrees with the theory, but an
36254 absence of bugs can never be guaranteed. Any that are reported will get fixed
36255 as soon as possible.
36258 .section "Building a more &""hardened""& Exim" "SECID286"
36259 .cindex "security" "build-time features"
36260 There are a number of build-time options that can be set in &_Local/Makefile_&
36261 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
36262 Exim administrator who does not have the root password, or by someone who has
36263 penetrated the Exim (but not the root) account. These options are as follows:
36266 ALT_CONFIG_PREFIX can be set to a string that is required to match the
36267 start of any file names used with the &%-C%& option. When it is set, these file
36268 names are also not allowed to contain the sequence &"/../"&. (However, if the
36269 value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
36270 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
36271 default setting for &%ALT_CONFIG_PREFIX%&.
36273 If the permitted configuration files are confined to a directory to
36274 which only root has access, this guards against someone who has broken
36275 into the Exim account from running a privileged Exim with an arbitrary
36276 configuration file, and using it to break into other accounts.
36279 If a non-trusted configuration file (i.e. not the default configuration file
36280 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
36281 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
36282 the next item), then root privilege is retained only if the caller of Exim is
36283 root. This locks out the possibility of testing a configuration using &%-C%&
36284 right through message reception and delivery, even if the caller is root. The
36285 reception works, but by that time, Exim is running as the Exim user, so when
36286 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
36287 privilege to be lost. However, root can test reception and delivery using two
36291 The WHITELIST_D_MACROS build option declares some macros to be safe to override
36292 with &%-D%& if the real uid is one of root, the Exim run-time user or the
36293 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
36294 requiring the run-time value supplied to &%-D%& to match a regex that errs on
36295 the restrictive side. Requiring build-time selection of safe macros is onerous
36296 but this option is intended solely as a transition mechanism to permit
36297 previously-working configurations to continue to work after release 4.73.
36299 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
36302 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
36303 never to be used for any deliveries. This is like the &%never_users%& runtime
36304 option, but it cannot be overridden; the runtime option adds additional users
36305 to the list. The default setting is &"root"&; this prevents a non-root user who
36306 is permitted to modify the runtime file from using Exim as a way to get root.
36311 .section "Root privilege" "SECID270"
36313 .cindex "root privilege"
36314 The Exim binary is normally setuid to root, which means that it gains root
36315 privilege (runs as root) when it starts execution. In some special cases (for
36316 example, when the daemon is not in use and there are no local deliveries), it
36317 may be possible to run Exim setuid to some user other than root. This is
36318 discussed in the next section. However, in most installations, root privilege
36319 is required for two things:
36322 To set up a socket connected to the standard SMTP port (25) when initialising
36323 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
36326 To be able to change uid and gid in order to read users' &_.forward_& files and
36327 perform local deliveries as the receiving user or as specified in the
36331 It is not necessary to be root to do any of the other things Exim does, such as
36332 receiving messages and delivering them externally over SMTP, and it is
36333 obviously more secure if Exim does not run as root except when necessary.
36334 For this reason, a user and group for Exim to use must be defined in
36335 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
36336 group"&. Their values can be changed by the run time configuration, though this
36337 is not recommended. Often a user called &'exim'& is used, but some sites use
36338 &'mail'& or another user name altogether.
36340 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
36341 abdication; the process cannot regain root afterwards. Prior to release 4.00,
36342 &[seteuid()]& was used in some circumstances, but this is no longer the case.
36344 After a new Exim process has interpreted its command line options, it changes
36345 uid and gid in the following cases:
36350 If the &%-C%& option is used to specify an alternate configuration file, or if
36351 the &%-D%& option is used to define macro values for the configuration, and the
36352 calling process is not running as root, the uid and gid are changed to those of
36353 the calling process.
36354 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
36355 option may not be used at all.
36356 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
36357 can be supplied if the calling process is running as root, the Exim run-time
36358 user or CONFIGURE_OWNER, if defined.
36363 If the expansion test option (&%-be%&) or one of the filter testing options
36364 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
36367 If the process is not a daemon process or a queue runner process or a delivery
36368 process or a process for testing address routing (started with &%-bt%&), the
36369 uid and gid are changed to the Exim user and group. This means that Exim always
36370 runs under its own uid and gid when receiving messages. This also applies when
36371 testing address verification
36374 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
36377 For a daemon, queue runner, delivery, or address testing process, the uid
36378 remains as root at this stage, but the gid is changed to the Exim group.
36381 The processes that initially retain root privilege behave as follows:
36384 A daemon process changes the gid to the Exim group and the uid to the Exim
36385 user after setting up one or more listening sockets. The &[initgroups()]&
36386 function is called, so that if the Exim user is in any additional groups, they
36387 will be used during message reception.
36389 A queue runner process retains root privilege throughout its execution. Its
36390 job is to fork a controlled sequence of delivery processes.
36392 A delivery process retains root privilege throughout most of its execution,
36393 but any actual deliveries (that is, the transports themselves) are run in
36394 subprocesses which always change to a non-root uid and gid. For local
36395 deliveries this is typically the uid and gid of the owner of the mailbox; for
36396 remote deliveries, the Exim uid and gid are used. Once all the delivery
36397 subprocesses have been run, a delivery process changes to the Exim uid and gid
36398 while doing post-delivery tidying up such as updating the retry database and
36399 generating bounce and warning messages.
36401 While the recipient addresses in a message are being routed, the delivery
36402 process runs as root. However, if a user's filter file has to be processed,
36403 this is done in a subprocess that runs under the individual user's uid and
36404 gid. A system filter is run as root unless &%system_filter_user%& is set.
36406 A process that is testing addresses (the &%-bt%& option) runs as root so that
36407 the routing is done in the same environment as a message delivery.
36413 .section "Running Exim without privilege" "SECTrunexiwitpri"
36414 .cindex "privilege, running without"
36415 .cindex "unprivileged running"
36416 .cindex "root privilege" "running without"
36417 Some installations like to run Exim in an unprivileged state for more of its
36418 operation, for added security. Support for this mode of operation is provided
36419 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
36420 gid are changed to the Exim user and group at the start of a delivery process
36421 (and also queue runner and address testing processes). This means that address
36422 routing is no longer run as root, and the deliveries themselves cannot change
36426 .cindex "daemon" "restarting"
36427 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
36428 that the daemon can still be started in the usual way, and it can respond
36429 correctly to SIGHUP because the re-invocation regains root privilege.
36431 An alternative approach is to make Exim setuid to the Exim user and also setgid
36432 to the Exim group. If you do this, the daemon must be started from a root
36433 process. (Calling Exim from a root process makes it behave in the way it does
36434 when it is setuid root.) However, the daemon cannot restart itself after a
36435 SIGHUP signal because it cannot regain privilege.
36437 It is still useful to set &%deliver_drop_privilege%& in this case, because it
36438 stops Exim from trying to re-invoke itself to do a delivery after a message has
36439 been received. Such a re-invocation is a waste of resources because it has no
36442 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
36443 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
36444 to the Exim user seems a clean approach, but there is one complication:
36446 In this style of operation, Exim is running with the real uid and gid set to
36447 those of the calling process, and the effective uid/gid set to Exim's values.
36448 Ideally, any association with the calling process' uid/gid should be dropped,
36449 that is, the real uid/gid should be reset to the effective values so as to
36450 discard any privileges that the caller may have. While some operating systems
36451 have a function that permits this action for a non-root effective uid, quite a
36452 number of them do not. Because of this lack of standardization, Exim does not
36453 address this problem at this time.
36455 For this reason, the recommended approach for &"mostly unprivileged"& running
36456 is to keep the Exim binary setuid to root, and to set
36457 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
36458 be used in the most straightforward way.
36460 If you configure Exim not to run delivery processes as root, there are a
36461 number of restrictions on what you can do:
36464 You can deliver only as the Exim user/group. You should explicitly use the
36465 &%user%& and &%group%& options to override routers or local transports that
36466 normally deliver as the recipient. This makes sure that configurations that
36467 work in this mode function the same way in normal mode. Any implicit or
36468 explicit specification of another user causes an error.
36470 Use of &_.forward_& files is severely restricted, such that it is usually
36471 not worthwhile to include them in the configuration.
36473 Users who wish to use &_.forward_& would have to make their home directory and
36474 the file itself accessible to the Exim user. Pipe and append-to-file entries,
36475 and their equivalents in Exim filters, cannot be used. While they could be
36476 enabled in the Exim user's name, that would be insecure and not very useful.
36478 Unless the local user mailboxes are all owned by the Exim user (possible in
36479 some POP3 or IMAP-only environments):
36482 They must be owned by the Exim group and be writeable by that group. This
36483 implies you must set &%mode%& in the appendfile configuration, as well as the
36484 mode of the mailbox files themselves.
36486 You must set &%no_check_owner%&, since most or all of the files will not be
36487 owned by the Exim user.
36489 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
36490 on a newly created mailbox when unprivileged. This also implies that new
36491 mailboxes need to be created manually.
36496 These restrictions severely restrict what can be done in local deliveries.
36497 However, there are no restrictions on remote deliveries. If you are running a
36498 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
36499 gives more security at essentially no cost.
36501 If you are using the &%mua_wrapper%& facility (see chapter
36502 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
36507 .section "Delivering to local files" "SECID271"
36508 Full details of the checks applied by &(appendfile)& before it writes to a file
36509 are given in chapter &<<CHAPappendfile>>&.
36513 .section "Running local commands" "SECTsecconslocalcmds"
36514 .cindex "security" "local commands"
36515 .cindex "security" "command injection attacks"
36516 There are a number of ways in which an administrator can configure Exim to run
36517 commands based upon received, untrustworthy, data. Further, in some
36518 configurations a user who can control a &_.forward_& file can also arrange to
36519 run commands. Configuration to check includes, but is not limited to:
36522 Use of &%use_shell%& in the pipe transport: various forms of shell command
36523 injection may be possible with this option present. It is dangerous and should
36524 be used only with considerable caution. Consider constraints which whitelist
36525 allowed characters in a variable which is to be used in a pipe transport that
36526 has &%use_shell%& enabled.
36528 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
36529 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
36530 &_.forward_& files in a redirect router. If Exim is running on a central mail
36531 hub to which ordinary users do not have shell access, but home directories are
36532 NFS mounted (for instance) then administrators should review the list of these
36533 forbid options available, and should bear in mind that the options that may
36534 need forbidding can change as new features are added between releases.
36536 The &%${run...}%& expansion item does not use a shell by default, but
36537 administrators can configure use of &_/bin/sh_& as part of the command.
36538 Such invocations should be viewed with prejudicial suspicion.
36540 Administrators who use embedded Perl are advised to explore how Perl's
36541 taint checking might apply to their usage.
36543 Use of &%${expand...}%& is somewhat analagous to shell's eval builtin and
36544 administrators are well advised to view its use with suspicion, in case (for
36545 instance) it allows a local-part to contain embedded Exim directives.
36547 Use of &%${match_local_part...}%& and friends becomes more dangerous if
36548 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
36549 each can reference arbitrary lists and files, rather than just being a list
36551 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
36552 real-world security vulnerabilities caused by its use with untrustworthy data
36553 injected in, for SQL injection attacks.
36554 Consider the use of the &%inlisti%& expansion condition instead.
36560 .section "Trust in configuration data" "SECTsecconfdata"
36561 .cindex "security" "data sources"
36562 .cindex "security" "regular expressions"
36563 .cindex "regular expressions" "security"
36564 .cindex "PCRE" "security"
36565 If configuration data for Exim can come from untrustworthy sources, there
36566 are some issues to be aware of:
36569 Use of &%${expand...}%& may provide a path for shell injection attacks.
36571 Letting untrusted data provide a regular expression is unwise.
36573 Using &%${match...}%& to apply a fixed regular expression against untrusted
36574 data may result in pathological behaviour within PCRE. Be aware of what
36575 "backtracking" means and consider options for being more strict with a regular
36576 expression. Avenues to explore include limiting what can match (avoiding &`.`&
36577 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
36578 possessive quantifiers or just not using regular expressions against untrusted
36581 It can be important to correctly use &%${quote:...}%&,
36582 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
36583 items to ensure that data is correctly constructed.
36585 Some lookups might return multiple results, even though normal usage is only
36586 expected to yield one result.
36592 .section "IPv4 source routing" "SECID272"
36593 .cindex "source routing" "in IP packets"
36594 .cindex "IP source routing"
36595 Many operating systems suppress IP source-routed packets in the kernel, but
36596 some cannot be made to do this, so Exim does its own check. It logs incoming
36597 IPv4 source-routed TCP calls, and then drops them. Things are all different in
36598 IPv6. No special checking is currently done.
36602 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
36603 Support for these SMTP commands is disabled by default. If required, they can
36604 be enabled by defining suitable ACLs.
36609 .section "Privileged users" "SECID274"
36610 .cindex "trusted users"
36611 .cindex "admin user"
36612 .cindex "privileged user"
36613 .cindex "user" "trusted"
36614 .cindex "user" "admin"
36615 Exim recognizes two sets of users with special privileges. Trusted users are
36616 able to submit new messages to Exim locally, but supply their own sender
36617 addresses and information about a sending host. For other users submitting
36618 local messages, Exim sets up the sender address from the uid, and doesn't
36619 permit a remote host to be specified.
36622 However, an untrusted user is permitted to use the &%-f%& command line option
36623 in the special form &%-f <>%& to indicate that a delivery failure for the
36624 message should not cause an error report. This affects the message's envelope,
36625 but it does not affect the &'Sender:'& header. Untrusted users may also be
36626 permitted to use specific forms of address with the &%-f%& option by setting
36627 the &%untrusted_set_sender%& option.
36629 Trusted users are used to run processes that receive mail messages from some
36630 other mail domain and pass them on to Exim for delivery either locally, or over
36631 the Internet. Exim trusts a caller that is running as root, as the Exim user,
36632 as any user listed in the &%trusted_users%& configuration option, or under any
36633 group listed in the &%trusted_groups%& option.
36635 Admin users are permitted to do things to the messages on Exim's queue. They
36636 can freeze or thaw messages, cause them to be returned to their senders, remove
36637 them entirely, or modify them in various ways. In addition, admin users can run
36638 the Exim monitor and see all the information it is capable of providing, which
36639 includes the contents of files on the spool.
36643 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
36644 delivery of messages on its queue is restricted to admin users. This
36645 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
36646 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
36647 queue is also restricted to admin users. This restriction can be relaxed by
36648 setting &%no_queue_list_requires_admin%&.
36650 Exim recognizes an admin user if the calling process is running as root or as
36651 the Exim user or if any of the groups associated with the calling process is
36652 the Exim group. It is not necessary actually to be running under the Exim
36653 group. However, if admin users who are not root or the Exim user are to access
36654 the contents of files on the spool via the Exim monitor (which runs
36655 unprivileged), Exim must be built to allow group read access to its spool
36660 .section "Spool files" "SECID275"
36661 .cindex "spool directory" "files"
36662 Exim's spool directory and everything it contains is owned by the Exim user and
36663 set to the Exim group. The mode for spool files is defined in the
36664 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
36665 any user who is a member of the Exim group can access these files.
36669 .section "Use of argv[0]" "SECID276"
36670 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
36671 of specific strings, Exim assumes certain options. For example, calling Exim
36672 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
36673 to calling it with the option &%-bS%&. There are no security implications in
36678 .section "Use of %f formatting" "SECID277"
36679 The only use made of &"%f"& by Exim is in formatting load average values. These
36680 are actually stored in integer variables as 1000 times the load average.
36681 Consequently, their range is limited and so therefore is the length of the
36686 .section "Embedded Exim path" "SECID278"
36687 Exim uses its own path name, which is embedded in the code, only when it needs
36688 to re-exec in order to regain root privilege. Therefore, it is not root when it
36689 does so. If some bug allowed the path to get overwritten, it would lead to an
36690 arbitrary program's being run as exim, not as root.
36694 .section "Dynamic module directory" "SECTdynmoddir"
36695 Any dynamically loadable modules must be installed into the directory
36696 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
36700 .section "Use of sprintf()" "SECID279"
36701 .cindex "&[sprintf()]&"
36702 A large number of occurrences of &"sprintf"& in the code are actually calls to
36703 &'string_sprintf()'&, a function that returns the result in malloc'd store.
36704 The intermediate formatting is done into a large fixed buffer by a function
36705 that runs through the format string itself, and checks the length of each
36706 conversion before performing it, thus preventing buffer overruns.
36708 The remaining uses of &[sprintf()]& happen in controlled circumstances where
36709 the output buffer is known to be sufficiently long to contain the converted
36714 .section "Use of debug_printf() and log_write()" "SECID280"
36715 Arbitrary strings are passed to both these functions, but they do their
36716 formatting by calling the function &'string_vformat()'&, which runs through
36717 the format string itself, and checks the length of each conversion.
36721 .section "Use of strcat() and strcpy()" "SECID281"
36722 These are used only in cases where the output buffer is known to be large
36723 enough to hold the result.
36724 .ecindex IIDsecurcon
36729 . ////////////////////////////////////////////////////////////////////////////
36730 . ////////////////////////////////////////////////////////////////////////////
36732 .chapter "Format of spool files" "CHAPspool"
36733 .scindex IIDforspo1 "format" "spool files"
36734 .scindex IIDforspo2 "spool directory" "format of files"
36735 .scindex IIDforspo3 "spool files" "format of"
36736 .cindex "spool files" "editing"
36737 A message on Exim's queue consists of two files, whose names are the message id
36738 followed by -D and -H, respectively. The data portion of the message is kept in
36739 the -D file on its own. The message's envelope, status, and headers are all
36740 kept in the -H file, whose format is described in this chapter. Each of these
36741 two files contains the final component of its own name as its first line. This
36742 is insurance against disk crashes where the directory is lost but the files
36743 themselves are recoverable.
36745 Some people are tempted into editing -D files in order to modify messages. You
36746 need to be extremely careful if you do this; it is not recommended and you are
36747 on your own if you do it. Here are some of the pitfalls:
36750 You must ensure that Exim does not try to deliver the message while you are
36751 fiddling with it. The safest way is to take out a write lock on the -D file,
36752 which is what Exim itself does, using &[fcntl()]&. If you update the file in
36753 place, the lock will be retained. If you write a new file and rename it, the
36754 lock will be lost at the instant of rename.
36756 .vindex "&$body_linecount$&"
36757 If you change the number of lines in the file, the value of
36758 &$body_linecount$&, which is stored in the -H file, will be incorrect. At
36759 present, this value is not used by Exim, but there is no guarantee that this
36760 will always be the case.
36762 If the message is in MIME format, you must take care not to break it.
36764 If the message is cryptographically signed, any change will invalidate the
36767 All in all, modifying -D files is fraught with danger.
36769 Files whose names end with -J may also be seen in the &_input_& directory (or
36770 its subdirectories when &%split_spool_directory%& is set). These are journal
36771 files, used to record addresses to which the message has been delivered during
36772 the course of a delivery attempt. If there are still undelivered recipients at
36773 the end, the -H file is updated, and the -J file is deleted. If, however, there
36774 is some kind of crash (for example, a power outage) before this happens, the -J
36775 file remains in existence. When Exim next processes the message, it notices the
36776 -J file and uses it to update the -H file before starting the next delivery
36779 .section "Format of the -H file" "SECID282"
36780 .cindex "uid (user id)" "in spool file"
36781 .cindex "gid (group id)" "in spool file"
36782 The second line of the -H file contains the login name for the uid of the
36783 process that called Exim to read the message, followed by the numerical uid and
36784 gid. For a locally generated message, this is normally the user who sent the
36785 message. For a message received over TCP/IP via the daemon, it is
36786 normally the Exim user.
36788 The third line of the file contains the address of the message's sender as
36789 transmitted in the envelope, contained in angle brackets. The sender address is
36790 empty for bounce messages. For incoming SMTP mail, the sender address is given
36791 in the MAIL command. For locally generated mail, the sender address is
36792 created by Exim from the login name of the current user and the configured
36793 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
36794 leading &"From&~"& line if the caller is trusted, or if the supplied address is
36795 &"<>"& or an address that matches &%untrusted_set_senders%&.
36797 The fourth line contains two numbers. The first is the time that the message
36798 was received, in the conventional Unix form &-- the number of seconds since the
36799 start of the epoch. The second number is a count of the number of messages
36800 warning of delayed delivery that have been sent to the sender.
36802 There follow a number of lines starting with a hyphen. These can appear in any
36803 order, and are omitted when not relevant:
36806 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
36807 This item is obsolete, and is not generated from Exim release 4.61 onwards;
36808 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
36809 recognized, to provide backward compatibility. In the old format, a line of
36810 this form is present for every ACL variable that is not empty. The number
36811 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
36812 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
36813 the data string for the variable. The string itself starts at the beginning of
36814 the next line, and is followed by a newline character. It may contain internal
36817 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
36818 A line of this form is present for every ACL connection variable that is
36819 defined. Note that there is a space between &%-aclc%& and the rest of the name.
36820 The length is the length of the data string for the variable. The string itself
36821 starts at the beginning of the next line, and is followed by a newline
36822 character. It may contain internal newlines.
36824 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
36825 A line of this form is present for every ACL message variable that is defined.
36826 Note that there is a space between &%-aclm%& and the rest of the name. The
36827 length is the length of the data string for the variable. The string itself
36828 starts at the beginning of the next line, and is followed by a newline
36829 character. It may contain internal newlines.
36831 .vitem "&%-active_hostname%&&~<&'hostname'&>"
36832 This is present if, when the message was received over SMTP, the value of
36833 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
36835 .vitem &%-allow_unqualified_recipient%&
36836 This is present if unqualified recipient addresses are permitted in header
36837 lines (to stop such addresses from being qualified if rewriting occurs at
36838 transport time). Local messages that were input using &%-bnq%& and remote
36839 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
36841 .vitem &%-allow_unqualified_sender%&
36842 This is present if unqualified sender addresses are permitted in header lines
36843 (to stop such addresses from being qualified if rewriting occurs at transport
36844 time). Local messages that were input using &%-bnq%& and remote messages from
36845 hosts that match &%sender_unqualified_hosts%& set this flag.
36847 .vitem "&%-auth_id%&&~<&'text'&>"
36848 The id information for a message received on an authenticated SMTP connection
36849 &-- the value of the &$authenticated_id$& variable.
36851 .vitem "&%-auth_sender%&&~<&'address'&>"
36852 The address of an authenticated sender &-- the value of the
36853 &$authenticated_sender$& variable.
36855 .vitem "&%-body_linecount%&&~<&'number'&>"
36856 This records the number of lines in the body of the message, and is always
36859 .vitem "&%-body_zerocount%&&~<&'number'&>"
36860 This records the number of binary zero bytes in the body of the message, and is
36861 present if the number is greater than zero.
36863 .vitem &%-deliver_firsttime%&
36864 This is written when a new message is first added to the spool. When the spool
36865 file is updated after a deferral, it is omitted.
36867 .vitem "&%-frozen%&&~<&'time'&>"
36868 .cindex "frozen messages" "spool data"
36869 The message is frozen, and the freezing happened at <&'time'&>.
36871 .vitem "&%-helo_name%&&~<&'text'&>"
36872 This records the host name as specified by a remote host in a HELO or EHLO
36875 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
36876 This records the IP address of the host from which the message was received and
36877 the remote port number that was used. It is omitted for locally generated
36880 .vitem "&%-host_auth%&&~<&'text'&>"
36881 If the message was received on an authenticated SMTP connection, this records
36882 the name of the authenticator &-- the value of the
36883 &$sender_host_authenticated$& variable.
36885 .vitem &%-host_lookup_failed%&
36886 This is present if an attempt to look up the sending host's name from its IP
36887 address failed. It corresponds to the &$host_lookup_failed$& variable.
36889 .vitem "&%-host_name%&&~<&'text'&>"
36890 .cindex "reverse DNS lookup"
36891 .cindex "DNS" "reverse lookup"
36892 This records the name of the remote host from which the message was received,
36893 if the host name was looked up from the IP address when the message was being
36894 received. It is not present if no reverse lookup was done.
36896 .vitem "&%-ident%&&~<&'text'&>"
36897 For locally submitted messages, this records the login of the originating user,
36898 unless it was a trusted user and the &%-oMt%& option was used to specify an
36899 ident value. For messages received over TCP/IP, this records the ident string
36900 supplied by the remote host, if any.
36902 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
36903 This records the IP address of the local interface and the port number through
36904 which a message was received from a remote host. It is omitted for locally
36905 generated messages.
36908 The message is from a local sender.
36910 .vitem &%-localerror%&
36911 The message is a locally-generated bounce message.
36913 .vitem "&%-local_scan%&&~<&'string'&>"
36914 This records the data string that was returned by the &[local_scan()]& function
36915 when the message was received &-- the value of the &$local_scan_data$&
36916 variable. It is omitted if no data was returned.
36918 .vitem &%-manual_thaw%&
36919 The message was frozen but has been thawed manually, that is, by an explicit
36920 Exim command rather than via the auto-thaw process.
36923 A testing delivery process was started using the &%-N%& option to suppress any
36924 actual deliveries, but delivery was deferred. At any further delivery attempts,
36927 .vitem &%-received_protocol%&
36928 This records the value of the &$received_protocol$& variable, which contains
36929 the name of the protocol by which the message was received.
36931 .vitem &%-sender_set_untrusted%&
36932 The envelope sender of this message was set by an untrusted local caller (used
36933 to ensure that the caller is displayed in queue listings).
36935 .vitem "&%-spam_score_int%&&~<&'number'&>"
36936 If a message was scanned by SpamAssassin, this is present. It records the value
36937 of &$spam_score_int$&.
36939 .vitem &%-tls_certificate_verified%&
36940 A TLS certificate was received from the client that sent this message, and the
36941 certificate was verified by the server.
36943 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
36944 When the message was received over an encrypted connection, this records the
36945 name of the cipher suite that was used.
36947 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
36948 When the message was received over an encrypted connection, and a certificate
36949 was received from the client, this records the Distinguished Name from that
36953 Following the options there is a list of those addresses to which the message
36954 is not to be delivered. This set of addresses is initialized from the command
36955 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
36956 is set; otherwise it starts out empty. Whenever a successful delivery is made,
36957 the address is added to this set. The addresses are kept internally as a
36958 balanced binary tree, and it is a representation of that tree which is written
36959 to the spool file. If an address is expanded via an alias or forward file, the
36960 original address is added to the tree when deliveries to all its child
36961 addresses are complete.
36963 If the tree is empty, there is a single line in the spool file containing just
36964 the text &"XX"&. Otherwise, each line consists of two letters, which are either
36965 Y or N, followed by an address. The address is the value for the node of the
36966 tree, and the letters indicate whether the node has a left branch and/or a
36967 right branch attached to it, respectively. If branches exist, they immediately
36968 follow. Here is an example of a three-node tree:
36970 YY darcy@austen.fict.example
36971 NN alice@wonderland.fict.example
36972 NN editor@thesaurus.ref.example
36974 After the non-recipients tree, there is a list of the message's recipients.
36975 This is a simple list, preceded by a count. It includes all the original
36976 recipients of the message, including those to whom the message has already been
36977 delivered. In the simplest case, the list contains one address per line. For
36981 editor@thesaurus.ref.example
36982 darcy@austen.fict.example
36984 alice@wonderland.fict.example
36986 However, when a child address has been added to the top-level addresses as a
36987 result of the use of the &%one_time%& option on a &(redirect)& router, each
36988 line is of the following form:
36990 <&'top-level address'&> <&'errors_to address'&> &&&
36991 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
36993 The 01 flag bit indicates the presence of the three other fields that follow
36994 the top-level address. Other bits may be used in future to support additional
36995 fields. The <&'parent number'&> is the offset in the recipients list of the
36996 original parent of the &"one time"& address. The first two fields are the
36997 envelope sender that is associated with this address and its length. If the
36998 length is zero, there is no special envelope sender (there are then two space
36999 characters in the line). A non-empty field can arise from a &(redirect)& router
37000 that has an &%errors_to%& setting.
37003 A blank line separates the envelope and status information from the headers
37004 which follow. A header may occupy several lines of the file, and to save effort
37005 when reading it in, each header is preceded by a number and an identifying
37006 character. The number is the number of characters in the header, including any
37007 embedded newlines and the terminating newline. The character is one of the
37011 .row <&'blank'&> "header in which Exim has no special interest"
37012 .row &`B`& "&'Bcc:'& header"
37013 .row &`C`& "&'Cc:'& header"
37014 .row &`F`& "&'From:'& header"
37015 .row &`I`& "&'Message-id:'& header"
37016 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
37017 .row &`R`& "&'Reply-To:'& header"
37018 .row &`S`& "&'Sender:'& header"
37019 .row &`T`& "&'To:'& header"
37020 .row &`*`& "replaced or deleted header"
37023 Deleted or replaced (rewritten) headers remain in the spool file for debugging
37024 purposes. They are not transmitted when the message is delivered. Here is a
37025 typical set of headers:
37027 111P Received: by hobbit.fict.example with local (Exim 4.00)
37028 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
37029 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
37030 038* X-rewrote-sender: bb@hobbit.fict.example
37031 042* From: Bilbo Baggins <bb@hobbit.fict.example>
37032 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
37033 099* To: alice@wonderland.fict.example, rdo@foundation,
37034 darcy@austen.fict.example, editor@thesaurus.ref.example
37035 104T To: alice@wonderland.fict.example, rdo@foundation.example,
37036 darcy@austen.fict.example, editor@thesaurus.ref.example
37037 038 Date: Fri, 11 May 2001 10:28:59 +0100
37039 The asterisked headers indicate that the envelope sender, &'From:'& header, and
37040 &'To:'& header have been rewritten, the last one because routing expanded the
37041 unqualified domain &'foundation'&.
37042 .ecindex IIDforspo1
37043 .ecindex IIDforspo2
37044 .ecindex IIDforspo3
37046 . ////////////////////////////////////////////////////////////////////////////
37047 . ////////////////////////////////////////////////////////////////////////////
37049 .chapter "Support for DKIM (DomainKeys Identified Mail)" "CHAPdkim" &&&
37053 DKIM is a mechanism by which messages sent by some entity can be provably
37054 linked to a domain which that entity controls. It permits reputation to
37055 be tracked on a per-domain basis, rather than merely upon source IP address.
37056 DKIM is documented in RFC 4871.
37058 Since version 4.70, DKIM support is compiled into Exim by default. It can be
37059 disabled by setting DISABLE_DKIM=yes in Local/Makefile.
37061 Exim's DKIM implementation allows to
37063 Sign outgoing messages: This function is implemented in the SMTP transport.
37064 It can co-exist with all other Exim features
37065 (including transport filters)
37066 except cutthrough delivery.
37068 Verify signatures in incoming messages: This is implemented by an additional
37069 ACL (acl_smtp_dkim), which can be called several times per message, with
37070 different signature contexts.
37073 In typical Exim style, the verification implementation does not include any
37074 default "policy". Instead it enables you to build your own policy using
37075 Exim's standard controls.
37077 Please note that verification of DKIM signatures in incoming mail is turned
37078 on by default for logging purposes. For each signature in incoming email,
37079 exim will log a line displaying the most important signature details, and the
37080 signature status. Here is an example (with line-breaks added for clarity):
37082 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
37083 d=facebookmail.com s=q1-2009b
37084 c=relaxed/relaxed a=rsa-sha1
37085 i=@facebookmail.com t=1252484542 [verification succeeded]
37087 You might want to turn off DKIM verification processing entirely for internal
37088 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
37089 control modifier. This should typically be done in the RCPT ACL, at points
37090 where you accept mail from relay sources (internal hosts or authenticated
37094 .section "Signing outgoing messages" "SECID513"
37095 .cindex "DKIM" "signing"
37097 Signing is implemented by setting private options on the SMTP transport.
37098 These options take (expandable) strings as arguments.
37100 .option dkim_domain smtp string&!! unset
37102 The domain you want to sign with. The result of this expanded
37103 option is put into the &%$dkim_domain%& expansion variable.
37105 .option dkim_selector smtp string&!! unset
37107 This sets the key selector string. You can use the &%$dkim_domain%& expansion
37108 variable to look up a matching selector. The result is put in the expansion
37109 variable &%$dkim_selector%& which should be used in the &%dkim_private_key%&
37110 option along with &%$dkim_domain%&.
37112 .option dkim_private_key smtp string&!! unset
37114 This sets the private key to use. You can use the &%$dkim_domain%& and
37115 &%$dkim_selector%& expansion variables to determine the private key to use.
37116 The result can either
37118 be a valid RSA private key in ASCII armor, including line breaks.
37120 start with a slash, in which case it is treated as a file that contains
37123 be "0", "false" or the empty string, in which case the message will not
37124 be signed. This case will not result in an error, even if &%dkim_strict%&
37128 .option dkim_canon smtp string&!! unset
37130 This option sets the canonicalization method used when signing a message.
37131 The DKIM RFC currently supports two methods: "simple" and "relaxed".
37132 The option defaults to "relaxed" when unset. Note: the current implementation
37133 only supports using the same canonicalization method for both headers and body.
37135 .option dkim_strict smtp string&!! unset
37137 This option defines how Exim behaves when signing a message that
37138 should be signed fails for some reason. When the expansion evaluates to
37139 either "1" or "true", Exim will defer. Otherwise Exim will send the message
37140 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
37143 .option dkim_sign_headers smtp string&!! unset
37145 When set, this option must expand to (or be specified as) a colon-separated
37146 list of header names. Headers with these names will be included in the message
37147 signature. When unspecified, the header names recommended in RFC4871 will be
37151 .section "Verifying DKIM signatures in incoming mail" "SECID514"
37152 .cindex "DKIM" "verification"
37154 Verification of DKIM signatures in incoming email is implemented via the
37155 &%acl_smtp_dkim%& ACL. By default, this ACL is called once for each
37156 syntactically(!) correct signature in the incoming message.
37157 A missing ACL definition defaults to accept.
37158 If any ACL call does not acccept, the message is not accepted.
37159 If a cutthrough delivery was in progress for the message it is
37160 summarily dropped (having wasted the transmission effort).
37162 To evaluate the signature in the ACL a large number of expansion variables
37163 containing the signature status and its details are set up during the
37164 runtime of the ACL.
37166 Calling the ACL only for existing signatures is not sufficient to build
37167 more advanced policies. For that reason, the global option
37168 &%dkim_verify_signers%&, and a global expansion variable
37169 &%$dkim_signers%& exist.
37171 The global option &%dkim_verify_signers%& can be set to a colon-separated
37172 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
37173 called. It is expanded when the message has been received. At this point,
37174 the expansion variable &%$dkim_signers%& already contains a colon-separated
37175 list of signer domains and identities for the message. When
37176 &%dkim_verify_signers%& is not specified in the main configuration,
37179 dkim_verify_signers = $dkim_signers
37181 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
37182 DKIM signature in the message. Current DKIM verifiers may want to explicitly
37183 call the ACL for known domains or identities. This would be achieved as follows:
37185 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
37187 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
37188 and "ebay.com", plus all domains and identities that have signatures in the message.
37189 You can also be more creative in constructing your policy. For example:
37191 dkim_verify_signers = $sender_address_domain:$dkim_signers
37194 If a domain or identity is listed several times in the (expanded) value of
37195 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
37198 Inside the &%acl_smtp_dkim%&, the following expansion variables are
37199 available (from most to least important):
37203 .vitem &%$dkim_cur_signer%&
37204 The signer that is being evaluated in this ACL run. This can be a domain or
37205 an identity. This is one of the list items from the expanded main option
37206 &%dkim_verify_signers%& (see above).
37207 .vitem &%$dkim_verify_status%&
37208 A string describing the general status of the signature. One of
37210 &%none%&: There is no signature in the message for the current domain or
37211 identity (as reflected by &%$dkim_cur_signer%&).
37213 &%invalid%&: The signature could not be verified due to a processing error.
37214 More detail is available in &%$dkim_verify_reason%&.
37216 &%fail%&: Verification of the signature failed. More detail is
37217 available in &%$dkim_verify_reason%&.
37219 &%pass%&: The signature passed verification. It is valid.
37221 .vitem &%$dkim_verify_reason%&
37222 A string giving a litte bit more detail when &%$dkim_verify_status%& is either
37223 "fail" or "invalid". One of
37225 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
37226 key for the domain could not be retrieved. This may be a temporary problem.
37228 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
37229 record for the domain is syntactically invalid.
37231 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
37232 body hash does not match the one specified in the signature header. This
37233 means that the message body was modified in transit.
37235 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
37236 could not be verified. This may mean that headers were modified,
37237 re-written or otherwise changed in a way which is incompatible with
37238 DKIM verification. It may of course also mean that the signature is forged.
37240 .vitem &%$dkim_domain%&
37241 The signing domain. IMPORTANT: This variable is only populated if there is
37242 an actual signature in the message for the current domain or identity (as
37243 reflected by &%$dkim_cur_signer%&).
37244 .vitem &%$dkim_identity%&
37245 The signing identity, if present. IMPORTANT: This variable is only populated
37246 if there is an actual signature in the message for the current domain or
37247 identity (as reflected by &%$dkim_cur_signer%&).
37248 .vitem &%$dkim_selector%&
37249 The key record selector string.
37250 .vitem &%$dkim_algo%&
37251 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
37252 .vitem &%$dkim_canon_body%&
37253 The body canonicalization method. One of 'relaxed' or 'simple'.
37254 .vitem &%dkim_canon_headers%&
37255 The header canonicalization method. One of 'relaxed' or 'simple'.
37256 .vitem &%$dkim_copiedheaders%&
37257 A transcript of headers and their values which are included in the signature
37258 (copied from the 'z=' tag of the signature).
37259 .vitem &%$dkim_bodylength%&
37260 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
37261 limit was set by the signer, "9999999999999" is returned. This makes sure
37262 that this variable always expands to an integer value.
37263 .vitem &%$dkim_created%&
37264 UNIX timestamp reflecting the date and time when the signature was created.
37265 When this was not specified by the signer, "0" is returned.
37266 .vitem &%$dkim_expires%&
37267 UNIX timestamp reflecting the date and time when the signer wants the
37268 signature to be treated as "expired". When this was not specified by the
37269 signer, "9999999999999" is returned. This makes it possible to do useful
37270 integer size comparisons against this value.
37271 .vitem &%$dkim_headernames%&
37272 A colon-separated list of names of headers included in the signature.
37273 .vitem &%$dkim_key_testing%&
37274 "1" if the key record has the "testing" flag set, "0" if not.
37275 .vitem &%$dkim_key_nosubdomains%&
37276 "1" if the key record forbids subdomaining, "0" otherwise.
37277 .vitem &%$dkim_key_srvtype%&
37278 Service type (tag s=) from the key record. Defaults to "*" if not specified
37280 .vitem &%$dkim_key_granularity%&
37281 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
37283 .vitem &%$dkim_key_notes%&
37284 Notes from the key record (tag n=).
37287 In addition, two ACL conditions are provided:
37290 .vitem &%dkim_signers%&
37291 ACL condition that checks a colon-separated list of domains or identities
37292 for a match against the domain or identity that the ACL is currently verifying
37293 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
37294 verb to a group of domains or identities. For example:
37297 # Warn when Mail purportedly from GMail has no signature at all
37298 warn log_message = GMail sender without DKIM signature
37299 sender_domains = gmail.com
37300 dkim_signers = gmail.com
37304 .vitem &%dkim_status%&
37305 ACL condition that checks a colon-separated list of possible DKIM verification
37306 results against the actual result of verification. This is typically used
37307 to restrict an ACL verb to a list of verification outcomes, for example:
37310 deny message = Mail from Paypal with invalid/missing signature
37311 sender_domains = paypal.com:paypal.de
37312 dkim_signers = paypal.com:paypal.de
37313 dkim_status = none:invalid:fail
37316 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
37317 see the documentation of the &%$dkim_verify_status%& expansion variable above
37318 for more information of what they mean.
37321 . ////////////////////////////////////////////////////////////////////////////
37322 . ////////////////////////////////////////////////////////////////////////////
37324 .chapter "Adding new drivers or lookup types" "CHID13" &&&
37325 "Adding drivers or lookups"
37326 .cindex "adding drivers"
37327 .cindex "new drivers, adding"
37328 .cindex "drivers" "adding new"
37329 The following actions have to be taken in order to add a new router, transport,
37330 authenticator, or lookup type to Exim:
37333 Choose a name for the driver or lookup type that does not conflict with any
37334 existing name; I will use &"newdriver"& in what follows.
37336 Add to &_src/EDITME_& the line:
37338 <&'type'&>&`_NEWDRIVER=yes`&
37340 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
37341 code is not to be included in the binary by default, comment this line out. You
37342 should also add any relevant comments about the driver or lookup type.
37344 Add to &_src/config.h.defaults_& the line:
37346 #define <type>_NEWDRIVER
37349 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
37350 and create a table entry as is done for all the other drivers and lookup types.
37352 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
37353 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
37354 Add your &`NEWDRIVER`& to that list.
37355 As long as the dynamic module would be named &_newdriver.so_&, you can use the
37356 simple form that most lookups have.
37358 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
37359 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
37360 driver or lookup type and add it to the definition of OBJ.
37362 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
37365 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
37366 as for other drivers and lookups.
37369 Then all you need to do is write the code! A good way to start is to make a
37370 proforma by copying an existing module of the same type, globally changing all
37371 occurrences of the name, and cutting out most of the code. Note that any
37372 options you create must be listed in alphabetical order, because the tables are
37373 searched using a binary chop procedure.
37375 There is a &_README_& file in each of the sub-directories of &_src_& describing
37376 the interface that is expected.
37381 . ////////////////////////////////////////////////////////////////////////////
37382 . ////////////////////////////////////////////////////////////////////////////
37384 . /////////////////////////////////////////////////////////////////////////////
37385 . These lines are processing instructions for the Simple DocBook Processor that
37386 . Philip Hazel has developed as a less cumbersome way of making PostScript and
37387 . PDFs than using xmlto and fop. They will be ignored by all other XML
37389 . /////////////////////////////////////////////////////////////////////////////
37394 foot_right_recto="&chaptertitle;"
37395 foot_right_verso="&chaptertitle;"
37399 .makeindex "Options index" "option"
37400 .makeindex "Variables index" "variable"
37401 .makeindex "Concept index" "concept"
37404 . /////////////////////////////////////////////////////////////////////////////
37405 . /////////////////////////////////////////////////////////////////////////////