. /////////////////////////////////////////////////////////////////////////////
. This is the primary source of the Exim Manual. It is an xfpt document that is
-. converted into DocBook XML for subsequent conversion into printing and online
+. converted into DocBook XML for subsequent conversion into printable and online
. formats. The markup used herein is "standard" xfpt markup, with some extras.
. The markup is summarized in a file called Markup.txt.
.
.literal off
. /////////////////////////////////////////////////////////////////////////////
-. This generate the outermost <book> element that wraps then entire document.
+. This generates the outermost <book> element that wraps the entire document.
. /////////////////////////////////////////////////////////////////////////////
.book
. Update the Copyright year (only) when changing content.
. /////////////////////////////////////////////////////////////////////////////
-.set previousversion "4.86"
+.set previousversion "4.92"
.include ./local_params
.set ACL "access control lists (ACLs)"
.set I " "
.macro copyyear
-2015
+2018, 2019
.endmacro
. /////////////////////////////////////////////////////////////////////////////
. provided in the xfpt library.
. /////////////////////////////////////////////////////////////////////////////
-. --- Override the &$ flag to automatically insert a $ with the variable name
+. --- Override the &$ flag to automatically insert a $ with the variable name.
.flag &$ $& "<varname>$" "</varname>"
. --- Short flags for daggers in option headings. They will always be inside
-. --- an italic string, but we want the daggers to be roman.
+. --- an italic string, but we want the daggers to be in Roman.
.flag &!! "</emphasis>†<emphasis>"
.flag &!? "</emphasis>‡<emphasis>"
. --- A macro for the common 2-column tables. The width of the first column
. --- is suitable for the many tables at the start of the main options chapter;
-. --- the small number of other 2-column tables override it.
+. --- a small number of other 2-column tables override it.
.macro table2 196pt 254pt
.itable none 0 0 2 $1 left $2 left
. ////////////////////////////////////////////////////////////////////////////
-. The <bookinfo> element is removed from the XML before processing for Ascii
+. The <bookinfo> element is removed from the XML before processing for ASCII
. output formats.
. ////////////////////////////////////////////////////////////////////////////
BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd,
GNU/Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD,
OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4,
-Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and Unixware.
+Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and UnixWare.
Some of these operating systems are no longer current and cannot easily be
tested, so the configuration files may no longer work in practice.
the file &_NOTICE_&. Exim is distributed under the terms of the GNU General
Public Licence, a copy of which may be found in the file &_LICENCE_&.
-The use, supply or promotion of Exim for the purpose of sending bulk,
-unsolicited electronic mail is incompatible with the basic aims of the program,
+The use, supply, or promotion of Exim for the purpose of sending bulk,
+unsolicited electronic mail is incompatible with the basic aims of Exim,
which revolve around the free provision of a service that enhances the quality
of personal communications. The author of Exim regards indiscriminate
mass-mailing as an antisocial, irresponsible abuse of the Internet.
.section "Exim documentation" "SECID1"
. Keep this example change bar when updating the documentation!
-.new
.cindex "documentation"
This edition of the Exim specification applies to version &version() of Exim.
Substantive changes from the &previousversion; edition are marked in some
-renditions of the document; this paragraph is so marked if the rendition is
+renditions of this document; this paragraph is so marked if the rendition is
capable of showing a change indicator.
-.wen
This document is very much a reference manual; it is not a tutorial. The reader
is expected to have some familiarity with the SMTP mail transfer protocol and
with general Unix system administration. Although there are some discussions
and examples in places, the information is mostly organized in a way that makes
it easy to look up, rather than in a natural order for sequential reading.
-Furthermore, the manual aims to cover every aspect of Exim in detail, including
+Furthermore, this manual aims to cover every aspect of Exim in detail, including
a number of rarely-used, special-purpose features that are unlikely to be of
very wide interest.
An &"easier"& discussion of Exim which provides more in-depth explanatory,
introductory, and tutorial material can be found in a book entitled &'The Exim
SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge
-(&url(http://www.uit.co.uk/exim-book/)).
+(&url(https://www.uit.co.uk/exim-book/)).
-This book also contains a chapter that gives a general introduction to SMTP and
+The book also contains a chapter that gives a general introduction to SMTP and
Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
with the latest release of Exim. (Note that the earlier book about Exim,
published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
.cindex "&_doc/NewStuff_&"
.cindex "&_doc/ChangeLog_&"
.cindex "change log"
-As the program develops, there may be features in newer versions that have not
+As Exim develops, there may be features in newer versions that have not
yet made it into this document, which is updated only when the most significant
digit of the fractional part of the version number changes. Specifications of
new features that are not yet in this manual are placed in the file
they are not documented in this manual. Information about experimental features
can be found in the file &_doc/experimental.txt_&.
-All changes to the program (whether new features, bug fixes, or other kinds of
+All changes to Exim (whether new features, bug fixes, or other kinds of
change) are noted briefly in the file called &_doc/ChangeLog_&.
.cindex "&_doc/spec.txt_&"
.row &_filter.txt_& "specification of the filter language"
.row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3"
.row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4"
+.row &_openssl.txt_& "installing a current OpenSSL release"
.endtable
The main specification and the specification of the filtering language are also
-.section "FTP and web sites" "SECID2"
-.cindex "web site"
+.section "FTP site and websites" "SECID2"
+.cindex "website"
.cindex "FTP site"
-The primary site for Exim source distributions is currently the University of
-Cambridge's FTP site, whose contents are described in &'Where to find the Exim
-distribution'& below. In addition, there is a web site and an FTP site at
-&%exim.org%&. These are now also hosted at the University of Cambridge. The
-&%exim.org%& site was previously hosted for a number of years by Energis
-Squared, formerly Planet Online Ltd, whose support I gratefully acknowledge.
+The primary site for Exim source distributions is the &%exim.org%& FTP site,
+available over HTTPS, HTTP and FTP. These services, and the &%exim.org%&
+website, are hosted at the University of Cambridge.
.cindex "wiki"
.cindex "FAQ"
-As well as Exim distribution tar files, the Exim web site contains a number of
+As well as Exim distribution tar files, the Exim website contains a number of
differently formatted versions of the documentation. A recent addition to the
-online information is the Exim wiki (&url(http://wiki.exim.org)),
+online information is the Exim wiki (&url(https://wiki.exim.org)),
which contains what used to be a separate FAQ, as well as various other
examples, tips, and know-how that have been contributed by Exim users.
+The wiki site should always redirect to the correct place, which is currently
+provided by GitHub, and is open to editing by anyone with a GitHub account.
.cindex Bugzilla
-An Exim Bugzilla exists at &url(http://bugs.exim.org). You can use
+An Exim Bugzilla exists at &url(https://bugs.exim.org). You can use
this to report bugs, and also to add items to the wish list. Please search
first to check that you are not duplicating a previous entry.
-
+Please do not ask for configuration help in the bug-tracker.
.section "Mailing lists" "SECID3"
the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
via this web page:
.display
-&url(http://lists.alioth.debian.org/mailman/listinfo/pkg-exim4-users)
+&url(https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/pkg-exim4-users)
.endd
-Please ask Debian-specific questions on this list and not on the general Exim
+Please ask Debian-specific questions on that list and not on the general Exim
lists.
-.section "Exim training" "SECID4"
-.cindex "training courses"
-Training courses in Cambridge (UK) used to be run annually by the author of
-Exim, before he retired. At the time of writing, there are no plans to run
-further Exim courses in Cambridge. However, if that changes, relevant
-information will be posted at &url(http://www-tus.csx.cam.ac.uk/courses/exim/).
-
.section "Bug reports" "SECID5"
.cindex "bug reports"
.cindex "reporting bugs"
Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
-via the Bugzilla (&url(http://bugs.exim.org)). However, if you are unsure
+via the Bugzilla (&url(https://bugs.exim.org)). However, if you are unsure
whether some behaviour is a bug or not, the best thing to do is to post a
message to the &'exim-dev'& mailing list and have it discussed.
.section "Where to find the Exim distribution" "SECTavail"
.cindex "FTP site"
-.cindex "distribution" "ftp site"
-The master ftp site for the Exim distribution is
+.cindex "HTTPS download site"
+.cindex "distribution" "FTP site"
+.cindex "distribution" "https site"
+The master distribution site for the Exim distribution is
.display
-&*ftp://ftp.csx.cam.ac.uk/pub/software/email/exim*&
+&url(https://downloads.exim.org/)
.endd
-This is mirrored by
-.display
-&*ftp://ftp.exim.org/pub/exim*&
-.endd
-The file references that follow are relative to the &_exim_& directories at
-these sites. There are now quite a number of independent mirror sites around
+The service is available over HTTPS, HTTP and FTP.
+We encourage people to migrate to HTTPS.
+
+The content served at &url(https://downloads.exim.org/) is identical to the
+content served at &url(https://ftp.exim.org/pub/exim) and
+&url(ftp://ftp.exim.org/pub/exim).
+
+If accessing via a hostname containing &'ftp'&, then the file references that
+follow are relative to the &_exim_& directories at these sites.
+If accessing via the hostname &'downloads'& then the subdirectories described
+here are top-level directories.
+
+There are now quite a number of independent mirror sites around
the world. Those that I know about are listed in the file called &_Mirrors_&.
-Within the &_exim_& directory there are subdirectories called &_exim3_& (for
+Within the top exim directory there are subdirectories called &_exim3_& (for
previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
distributions), and &_Testing_& for testing versions. In the &_exim4_&
subdirectory, the current release can always be found in files called
.display
+&_exim-n.nn.tar.xz_&
&_exim-n.nn.tar.gz_&
&_exim-n.nn.tar.bz2_&
.endd
-where &'n.nn'& is the highest such version number in the directory. The two
+where &'n.nn'& is the highest such version number in the directory. The three
files contain identical data; the only difference is the type of compression.
-The &_.bz2_& file is usually a lot smaller than the &_.gz_& file.
+The &_.xz_& file is usually the smallest, while the &_.gz_& file is the
+most portable to old systems.
.cindex "distribution" "signing details"
.cindex "distribution" "public key"
Coordinator. This key will have a uid containing an email address in the
&'exim.org'& domain and will have signatures from other people, including
other Exim maintainers. We expect that the key will be in the "strong set" of
-PGP keys. There should be a trust path to that key from Nigel Metheringham's
-PGP key, a version of which can be found in the release directory in the file
-&_nigel-pubkey.asc_&. All keys used will be available in public keyserver pools,
+PGP keys. There should be a trust path to that key from the Exim Maintainer's
+PGP keys, a version of which can be found in the release directory in the file
+&_Exim-Maintainers-Keyring.asc_&. All keys used will be available in public keyserver pools,
such as &'pool.sks-keyservers.net'&.
-At time of last update, releases were being made by Phil Pennock and signed with
-key &'0x403043153903637F'&, although that key is expected to be replaced in 2013.
-A trust path from Nigel's key to Phil's can be observed at
-&url(https://www.security.spodhuis.org/exim-trustpath).
-
-Releases have also been authorized to be performed by Todd Lyons who signs with
-key &'0xC4F4F94804D29EBA'&. A direct trust path exists between previous RE Phil
-Pennock and Todd Lyons through a common associate.
+At the time of the last update, releases were being made by Jeremy Harris and signed
+with key &'0xBCE58C8CE41F32DF'&. Other recent keys used for signing are those
+of Heiko Schlittermann, &'0x26101B62F69376CE'&,
+and of Phil Pennock, &'0x4D1E900E14C1CC04'&.
The signatures for the tar bundles are in:
.display
+&_exim-n.nn.tar.xz.asc_&
&_exim-n.nn.tar.gz.asc_&
&_exim-n.nn.tar.bz2.asc_&
.endd
-For each released version, the log of changes is made separately available in a
+For each released version, the log of changes is made available in a
separate file in the directory &_ChangeLogs_& so that it is possible to
find out what has changed without having to download the entire distribution.
&_exim-texinfo-n.nn.tar.gz_&
.endd
These tar files contain only the &_doc_& directory, not the complete
-distribution, and are also available in &_.bz2_& as well as &_.gz_& forms.
+distribution, and are also available in &_.bz2_& and &_.xz_& forms.
.section "Limitations" "SECID6"
.endlist
-.section "Run time configuration" "SECID7"
-Exim's run time configuration is held in a single text file that is divided
+.section "Runtime configuration" "SECID7"
+Exim's runtime configuration is held in a single text file that is divided
into a number of sections. The entries in this file consist of keywords and
values, in the style of Smail 3 configuration files. A default configuration
file which is suitable for simple online installations is provided in the
&_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
about Sendmail in order to run Exim. For actions other than sending messages,
Sendmail-compatible options also exist, but those that produce output (for
-example, &%-bp%&, which lists the messages on the queue) do so in Exim's own
+example, &%-bp%&, which lists the messages in the queue) do so in Exim's own
format. There are also some additional options that are compatible with Smail
3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
documents all Exim's command line options. This information is automatically
made into the man page that forms part of the Exim distribution.
-Control of messages on the queue can be done via certain privileged command
+Control of messages in the queue can be done via certain privileged command
line options. There is also an optional monitor program called &'eximon'&,
which displays current information in an X window, and which contains a menu
interface to Exim's command line administration options.
.cindex "terminology definitions"
.cindex "body of message" "definition of"
The &'body'& of a message is the actual data that the sender wants to transmit.
-It is the last part of a message, and is separated from the &'header'& (see
+It is the last part of a message and is separated from the &'header'& (see
below) by a blank line.
.cindex "bounce message" "definition of"
.cindex "local part" "definition of"
.cindex "domain" "definition of"
-The term &'local part'&, which is taken from RFC 2822, is used to refer to that
+The term &'local part'&, which is taken from RFC 2822, is used to refer to the
part of an email address that precedes the @ sign. The part that follows the
@ sign is called the &'domain'& or &'mail domain'&.
message's envelope.
.cindex "queue" "definition of"
-The term &'queue'& is used to refer to the set of messages awaiting delivery,
+The term &'queue'& is used to refer to the set of messages awaiting delivery
because this term is in widespread use in the context of MTAs. However, in
-Exim's case the reality is more like a pool than a queue, because there is
+Exim's case, the reality is more like a pool than a queue, because there is
normally no ordering of waiting messages.
.cindex "queue runner" "definition of"
The term &'queue runner'& is used to describe a process that scans the queue
and attempts to deliver those messages whose retry times have come. This term
-is used by other MTAs, and also relates to the command &%runq%&, but in Exim
+is used by other MTAs and also relates to the command &%runq%&, but in Exim
the waiting messages are normally processed in an unpredictable order.
.cindex "spool directory" "definition of"
The term &'spool directory'& is used for a directory in which Exim keeps the
-messages on its queue &-- that is, those that it is in the process of
+messages in its queue &-- that is, those that it is in the process of
delivering. This should not be confused with the directory in which local
mailboxes are stored, which is called a &"spool directory"& by some people. In
the Exim documentation, &"spool"& is always used in the first sense.
version.
This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
the spec and sample code for cdb can be obtained from
-&url(http://www.pobox.com/~djb/cdb.html). This implementation borrows
+&url(https://cr.yp.to/cdb.html). This implementation borrows
some code from Dan Bernstein's implementation (which has no license
restrictions applied to it).
.endblockquote
acknowledgment:
&"This product includes software developed by Computing Services
-at Carnegie Mellon University (&url(http://www.cmu.edu/computing/)."&
+at Carnegie Mellon University (&url(https://www.cmu.edu/computing/)."&
CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
.next
Many people have contributed code fragments, some large, some small, that were
-not covered by any specific licence requirements. It is assumed that the
+not covered by any specific license requirements. It is assumed that the
contributors are happy to see their code incorporated into Exim under the GPL.
.endlist
.section "Policy control" "SECID11"
.cindex "policy control" "overview"
Policy controls are now an important feature of MTAs that are connected to the
-Internet. Perhaps their most important job is to stop MTAs being abused as
+Internet. Perhaps their most important job is to stop MTAs from being abused as
&"open relays"& by misguided individuals who send out vast amounts of
-unsolicited junk, and want to disguise its source. Exim provides flexible
+unsolicited junk and want to disguise its source. Exim provides flexible
facilities for specifying policy controls on incoming mail:
.ilist
normally encoding numbers in base 62. However, in the Darwin operating
system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
(avoiding the use of lower case letters) is used instead, because the message
-id is used to construct file names, and the names of files in those systems are
+id is used to construct filenames, and the names of files in those systems are
not always case-sensitive.
.cindex "pid (process id)" "re-use of"
If the process runs Exim with the &%-bS%& option, the message is also read
non-interactively, but in this case the recipients are listed at the start of
the message in a series of SMTP RCPT commands, terminated by a DATA
-command. This is so-called &"batch SMTP"& format,
+command. This is called &"batch SMTP"& format,
but it isn't really SMTP. The SMTP commands are just another way of passing
envelope addresses in a non-interactive submission.
.next
qualification domain (which can be set by the &%qualify_domain%& configuration
option). For local or batch SMTP, a sender address that is passed using the
SMTP MAIL command is ignored. However, the system administrator may allow
-certain users (&"trusted users"&) to specify a different sender address
+certain users (&"trusted users"&) to specify a different sender addresses
unconditionally, or all users to specify certain forms of different sender
address. The &%-f%& option or the SMTP MAIL command is used to specify these
different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
users to change sender addresses.
Messages received by either of the non-interactive mechanisms are subject to
-checking by the non-SMTP ACL, if one is defined. Messages received using SMTP
-(either over TCP/IP, or interacting with a local process) can be checked by a
+checking by the non-SMTP ACL if one is defined. Messages received using SMTP
+(either over TCP/IP or interacting with a local process) can be checked by a
number of ACLs that operate at different times during the SMTP session. Either
-individual recipients, or the entire message, can be rejected if local policy
+individual recipients or the entire message can be rejected if local policy
requirements are not met. The &[local_scan()]& function (see chapter
&<<CHAPlocalscan>>&) is run for all incoming messages.
file containing the envelope and header, and &`-D`& for the data file.
.cindex "spool directory" "&_input_& sub-directory"
-By default all these message files are held in a single directory called
+By default, all these message files are held in a single directory called
&_input_& inside the general Exim spool directory. Some operating systems do
not perform very well if the number of files in a directory gets large; to
improve performance in such cases, the &%split_spool_directory%& option can be
A message remains in the spool directory until it is completely delivered to
its recipients or to an error address, or until it is deleted by an
administrator or by the user who originally created it. In cases when delivery
-cannot proceed &-- for example, when a message can neither be delivered to its
+cannot proceed &-- for example when a message can neither be delivered to its
recipients nor returned to its sender, the message is marked &"frozen"& on the
spool, and no more deliveries are attempted.
.oindex "&%ignore_bounce_errors_after%&"
There are options called &%ignore_bounce_errors_after%& and
&%timeout_frozen_after%&, which discard frozen messages after a certain time.
-The first applies only to frozen bounces, the second to any frozen messages.
+The first applies only to frozen bounces, the second to all frozen messages.
.cindex "message" "log file for"
.cindex "log" "file for each message"
attempt to its main log file. This includes successful, unsuccessful, and
delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
lines are also written to a separate &'message log'& file for each message.
-These logs are solely for the benefit of the administrator, and are normally
+These logs are solely for the benefit of the administrator and are normally
deleted along with the spool files when processing of a message is complete.
The use of individual message logs can be disabled by setting
&%no_message_logs%&; this might give an improvement in performance on very busy
Updating the spool file is done by writing a new file and renaming it, to
minimize the possibility of data loss.
-Should the system or the program crash after a successful delivery but before
+Should the system or Exim crash after a successful delivery but before
the spool file has been updated, the journal is left lying around. The next
time Exim attempts to deliver the message, it reads the journal file and
updates the spool file before proceeding. This minimizes the chances of double
The main delivery processing elements of Exim are called &'routers'& and
&'transports'&, and collectively these are known as &'drivers'&. Code for a
number of them is provided in the source distribution, and compile-time options
-specify which ones are included in the binary. Run time options specify which
+specify which ones are included in the binary. Runtime options specify which
ones are actually used for delivering messages.
.cindex "drivers" "instance definition"
-Each driver that is specified in the run time configuration is an &'instance'&
+Each driver that is specified in the runtime configuration is an &'instance'&
of that particular driver type. Multiple instances are allowed; for example,
you can set up several different &(smtp)& transports, each with different
option values that might specify different ports or different timeouts. Each
configuration.
The first router that is specified in a configuration is often one that handles
-addresses in domains that are not recognized specially by the local host. These
-are typically addresses for arbitrary domains on the Internet. A precondition
+addresses in domains that are not recognized specifically by the local host.
+Typically these are addresses for arbitrary domains on the Internet. A precondition
is set up which looks for the special domains known to the host (for example,
its own domain name), and the router is run for addresses that do &'not'&
match. Typically, this is a router that looks up domains in the DNS in order to
does not affect the way the routers work, but it is a state that can be
detected. By this means, a router can be skipped or made to behave differently
when verifying. A common example is a configuration in which the first router
-sends all messages to a message-scanning program, unless they have been
+sends all messages to a message-scanning program unless they have been
previously scanned. Thus, the first router accepts all addresses without any
checking, making it useless for verifying. Normally, the &%no_verify%& option
would be set for such a router, causing it to be skipped in verify mode.
.ilist
&'accept'&: The router accepts the address, and either assigns it to a
-transport, or generates one or more &"child"& addresses. Processing the
-original address ceases,
+transport or generates one or more &"child"& addresses. Processing the
+original address ceases
.oindex "&%unseen%&"
unless the &%unseen%& option is set on the router. This option
can be used to set up multiple deliveries with different routing (for example,
&%redirect_router%& may be anywhere in the router configuration.
.next
&'pass'&: The router recognizes the address, but cannot handle it itself. It
-requests that the address be passed to another router. By default the address
+requests that the address be passed to another router. By default, the address
is passed to the next router, but this can be changed by setting the
&%pass_router%& option. However, (unlike &%redirect_router%&) the named router
must be below the current router (to avoid loops).
.cindex "address duplicate, discarding"
.cindex "duplicate addresses"
Once routing is complete, Exim scans the addresses that are assigned to local
-and remote transports, and discards any duplicates that it finds. During this
-check, local parts are treated as case-sensitive. This happens only when
+and remote transports and discards any duplicates that it finds. During this
+check, local parts are treated case-sensitively. This happens only when
actually delivering a message; when testing routers with &%-bt%&, all the
routed addresses are shown.
described in more detail in chapter &<<CHAProutergeneric>>&.
.ilist
+.cindex affix "router precondition"
The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
the local parts handled by the router may or must have certain prefixes and/or
suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
.vindex "&$local_part_prefix$&"
.vindex "&$local_part$&"
.vindex "&$local_part_suffix$&"
+.cindex affix "router precondition"
If the &%local_parts%& option is set, the local part of the address must be in
the set of local parts that it defines. If &%local_part_prefix%& or
&%local_part_suffix%& is in use, the prefix or suffix is removed from the local
condition &%first_delivery%& can be used to detect the first run of the system
filter.
.next
-Each recipient address is offered to each configured router in turn, subject to
+Each recipient address is offered to each configured router, in turn, subject to
its preconditions, until one is able to handle it. If no router can handle the
address, that is, if they all decline, the address is failed. Because routers
can be targeted at particular domains, several locally handled domains can be
Exim's mechanism for retrying messages that fail to get delivered at the first
attempt is the queue runner process. You must either run an Exim daemon that
uses the &%-q%& option with a time interval to start queue runners at regular
-intervals, or use some other means (such as &'cron'&) to start them. If you do
+intervals or use some other means (such as &'cron'&) to start them. If you do
not arrange for queue runners to be run, messages that fail temporarily at the
-first attempt will remain on your queue for ever. A queue runner process works
+first attempt will remain in your queue forever. A queue runner process works
its way through the queue, one message at a time, trying each delivery that has
passed its retry time.
You can run several queue runners at once.
.section "Failures to deliver bounce messages" "SECID22"
.cindex "bounce message" "failure to deliver"
If a bounce message (either locally generated or received from a remote host)
-itself suffers a permanent delivery failure, the message is left on the queue,
+itself suffers a permanent delivery failure, the message is left in the queue,
but it is frozen, awaiting the attention of an administrator. There are options
that can be used to make Exim discard such failed messages, or to keep them
for only a short time (see &%timeout_frozen_after%& and
.irow &_util_& "independent utilities"
.endtable
-The main utility programs are contained in the &_src_& directory, and are built
+The main utility programs are contained in the &_src_& directory and are built
with the Exim binary. The &_util_& directory contains a few optional scripts
that may be useful to some sites.
the actual building takes place. In most cases, Exim can discover the machine
architecture and operating system for itself, but the defaults can be
overridden if necessary.
+.cindex compiler requirements
+.cindex compiler version
+A C99-capable compiler will be required for the build.
.section "PCRE library" "SECTpcre"
.cindex "PCRE library"
Exim no longer has an embedded PCRE library as the vast majority of
-modern systems include PCRE as a system library, although you may need
-to install the PCRE or PCRE development package for your operating
+modern systems include PCRE as a system library, although you may need to
+install the PCRE package or the PCRE development package for your operating
system. If your system has a normal PCRE installation the Exim build
process will need no further configuration. If the library or the
headers are in an unusual location you will need to either set the PCRE_LIBS
If your operating system has no
PCRE support then you will need to obtain and build the current PCRE
from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
-More information on PCRE is available at &url(http://www.pcre.org/).
+More information on PCRE is available at &url(https://www.pcre.org/).
.section "DBM libraries" "SECTdb"
.cindex "DBM libraries" "discussion of"
The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
compatibility interface it makes two different hard links to it with names
&_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
-file name is used unmodified.
+filename is used unmodified.
.next
.cindex "Berkeley DB library"
The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
.next
To complicate things further, there are several very different versions of the
Berkeley DB package. Version 1.85 was stable for a very long time, releases
-2.&'x'& and 3.&'x'& were current for a while, but the latest versions are now
-numbered 4.&'x'&. Maintenance of some of the earlier releases has ceased. All
-versions of Berkeley DB can be obtained from
-&url(http://www.sleepycat.com/).
+2.&'x'& and 3.&'x'& were current for a while, but the latest versions when Exim last revamped support were numbered 4.&'x'&.
+Maintenance of some of the earlier releases has ceased. All versions of
+Berkeley DB could be obtained from
+&url(http://www.sleepycat.com/), which is now a redirect to their new owner's
+page with far newer versions listed.
+It is probably wise to plan to move your storage configurations away from
+Berkeley DB format, as today there are smaller and simpler alternatives more
+suited to Exim's usage model.
.next
.cindex "&'tdb'& DBM library"
Yet another DBM library, called &'tdb'&, is available from
-&url(http://download.sourceforge.net/tdb). It has its own interface, and also
+&url(https://sourceforge.net/projects/tdb/files/). It has its own interface, and also
operates on a single file.
.endlist
&_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
There are three settings that you must supply, because Exim will not build
-without them. They are the location of the run time configuration file
+without them. They are the location of the runtime configuration file
(CONFIGURE_FILE), the directory in which Exim binaries will be installed
(BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
-a colon-separated list of file names; Exim uses the first of them that exists.
+a colon-separated list of filenames; Exim uses the first of them that exists.
There are a few other parameters that can be specified either at build time or
-at run time, to enable the same binary to be used on a number of different
+at runtime, to enable the same binary to be used on a number of different
machines. However, if the locations of Exim's spool directory and log file
directory (if not within the spool directory) are fixed, it is recommended that
-you specify them in &_Local/Makefile_& instead of at run time, so that errors
+you specify them in &_Local/Makefile_& instead of at runtime, so that errors
detected early in Exim's execution (such as a malformed configuration file) can
be logged.
This is all the configuration that is needed in straightforward cases for known
operating systems. However, the building process is set up so that it is easy
to override options that are set by default or by operating-system-specific
-configuration files, for example to change the name of the C compiler, which
+configuration files, for example, to change the C compiler, which
defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
do this.
However, some of the operating systems that supply &[iconv()]& do not support
very many conversions. The GNU &%libiconv%& library (available from
-&url(http://www.gnu.org/software/libiconv/)) can be installed on such
+&url(https://www.gnu.org/software/libiconv/)) can be installed on such
systems to remedy this deficiency, as well as on systems that do not supply
&[iconv()]& at all. After installing &%libiconv%&, you should add
.code
.section "Including TLS/SSL encryption support" "SECTinctlsssl"
.cindex "TLS" "including support for TLS"
.cindex "encryption" "including support for"
-.cindex "SUPPORT_TLS"
.cindex "OpenSSL" "building Exim with"
.cindex "GnuTLS" "building Exim with"
-Exim can be built to support encrypted SMTP connections, using the STARTTLS
-command as per RFC 2487. It can also support legacy clients that expect to
+Exim is usually built to support encrypted SMTP connections, using the STARTTLS
+command as per RFC 2487. It can also support clients that expect to
start a TLS session immediately on connection to a non-standard port (see the
&%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
line option).
OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
implementing SSL.
+.new
+If you do not want TLS support you should set
+.code
+DISABLE_TLS=yes
+.endd
+in &_Local/Makefile_&.
+.wen
+
If OpenSSL is installed, you should set
.code
-SUPPORT_TLS=yes
+USE_OPENSL=yes
TLS_LIBS=-lssl -lcrypto
.endd
in &_Local/Makefile_&. You may also need to specify the locations of the
OpenSSL library and include files. For example:
.code
-SUPPORT_TLS=yes
+USE_OPENSL=yes
TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
TLS_INCLUDE=-I/usr/local/openssl/include/
.endd
.cindex "pkg-config" "OpenSSL"
If you have &'pkg-config'& available, then instead you can just use:
.code
-SUPPORT_TLS=yes
+USE_OPENSL=yes
USE_OPENSSL_PC=openssl
.endd
.cindex "USE_GNUTLS"
If GnuTLS is installed, you should set
.code
-SUPPORT_TLS=yes
USE_GNUTLS=yes
TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
.endd
in &_Local/Makefile_&, and again you may need to specify the locations of the
library and include files. For example:
.code
-SUPPORT_TLS=yes
USE_GNUTLS=yes
TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
TLS_INCLUDE=-I/usr/gnu/include
.cindex "pkg-config" "GnuTLS"
If you have &'pkg-config'& available, then instead you can just use:
.code
-SUPPORT_TLS=yes
USE_GNUTLS=yes
USE_GNUTLS_PC=gnutls
.endd
However, there are some optional lookup types (such as cdb) for which
the code is entirely contained within Exim, and no external include
files or libraries are required. When a lookup type is not included in the
-binary, attempts to configure Exim to use it cause run time configuration
+binary, attempts to configure Exim to use it cause runtime configuration
errors.
.cindex "pkg-config" "lookups"
&_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
variables of the same name, preceded by EXIMON_. For example, setting
EXIMON_LOG_DEPTH in the environment overrides the value of
-LOG_DEPTH at run time.
+LOG_DEPTH at runtime.
.ecindex IIDbuex
chapter &<<CHAPsecurity>>& for details).
.cindex "CONFIGURE_FILE"
-Exim's run time configuration file is named by the CONFIGURE_FILE setting
+Exim's runtime configuration file is named by the CONFIGURE_FILE setting
in &_Local/Makefile_&. If this names a single file, and the file does not
exist, the default configuration file &_src/configure.default_& is copied there
-by the installation script. If a run time configuration file already exists, it
+by the installation script. If a runtime configuration file already exists, it
is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
alternative files, no default is installed.
For the utility programs, old versions are renamed by adding the suffix &_.O_&
to their names. The Exim binary itself, however, is handled differently. It is
installed under a name that includes the version number and the compile number,
-for example &_exim-&version()-1_&. The script then arranges for a symbolic link
+for example, &_exim-&version()-1_&. The script then arranges for a symbolic link
called &_exim_& to point to the binary. If you are updating a previous version
of Exim, the script takes care to ensure that the name &_exim_& is never absent
from the directory (as seen by other processes).
.cindex "installing Exim" "&'info'& documentation"
Not all systems use the GNU &'info'& system for documentation, and for this
reason, the Texinfo source of Exim's documentation is not included in the main
-distribution. Instead it is available separately from the ftp site (see section
+distribution. Instead it is available separately from the FTP site (see section
&<<SECTavail>>&).
If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
.section "Testing" "SECID34"
.cindex "testing" "installation"
-Having installed Exim, you can check that the run time configuration file is
+Having installed Exim, you can check that the runtime configuration file is
syntactically valid by running the following command, which assumes that the
Exim binary directory is within your PATH environment variable:
.code
Testing a new version on a system that is already running Exim can most easily
be done by building a binary with a different CONFIGURE_FILE setting. From
-within the run time configuration, all other file and directory names
+within the runtime configuration, all other file and directory names
that Exim uses can be altered, in order to keep it entirely clear of the
production version.
If you are already running Exim on your host, building and installing a new
version automatically makes it available to MUAs, or any other programs that
call the MTA directly. However, if you are running an Exim daemon, you do need
+.cindex restart "on HUP signal"
+.cindex signal "HUP, to restart"
to send it a HUP signal, to make it re-execute itself, and thereby pick up the
new binary. You do not need to stop processing mail in order to install a new
version of Exim. The install script does not modify an existing runtime
configuration option. Note that the Exim group is not automatically trusted.
.cindex '&"From"& line'
+.cindex "envelope from"
.cindex "envelope sender"
Trusted users are always permitted to use the &%-f%& option or a leading
&"From&~"& line to specify the envelope sender of a message that is passed to
.cindex "&'From:'& header line"
.cindex "&'Sender:'& header line"
+.cindex "header lines" "From:"
+.cindex "header lines" "Sender:"
For a trusted user, there is never any check on the contents of the &'From:'&
header line, and a &'Sender:'& line is never added. Furthermore, any existing
&'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
The SIGHUP signal
.cindex "SIGHUP"
+.cindex restart "on HUP signal"
+.cindex signal "HUP, to restart"
.cindex "daemon" "restarting"
+.cindex signal "to reload configuration"
+.cindex daemon "reload configuration"
+.cindex reload configuration
can be used to cause the daemon to re-execute itself. This should be done
whenever Exim's configuration file, or any file that is incorporated into it by
means of the &%.include%& facility, is changed, and also whenever a new version
test data. A line history is supported.
Long expansion expressions can be split over several lines by using backslash
-continuations. As in Exim's run time configuration, white space at the start of
+continuations. As in Exim's runtime configuration, white space at the start of
continuation lines is ignored. Each argument or data line is passed through the
string expansion mechanism, and the result is output. Variable values from the
configuration file (for example, &$qualify_domain$&) are available, but no
-message-specific values (such as &$sender_domain$&) are set, because no message
+message-specific values (such as &$message_exim_id$&) are set, because no message
is being processed (but see &%-bem%& and &%-Mset%&).
&*Note*&: If you use this mechanism to test lookups, and you change the data
the same lookup again. Otherwise, because each Exim process caches the results
of lookups, you will just get the same result as before.
+Macro processing is done on lines before string-expansion: new macros can be
+defined and macros will be expanded.
+Because macros in the config file are often used for secrets, those are only
+available to admin users.
+
.vitem &%-bem%&&~<&'filename'&>
.oindex "&%-bem%&"
.cindex "testing" "string expansion"
When testing a filter file,
.cindex "&""From""& line"
+.cindex "envelope from"
.cindex "envelope sender"
.oindex "&%-f%&" "for filter testing"
the envelope sender can be set by the &%-f%& option,
.vitem &%-bfp%&&~<&'prefix'&>
.oindex "&%-bfp%&"
+.cindex affix "filter testing"
This sets the prefix of the local part of the recipient address when a filter
file is being tested by means of the &%-bf%& option. The default is an empty
prefix.
.vitem &%-bfs%&&~<&'suffix'&>
.oindex "&%-bfs%&"
+.cindex affix "filter testing"
This sets the suffix of the local part of the recipient address when a filter
file is being tested by means of the &%-bf%& option. The default is an empty
suffix.
Features such as authentication and encryption, where the client input is not
plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
specialized SMTP test program such as
-&url(http://jetmore.org/john/code/#swaks,swaks).
+&url(https://www.jetmore.org/john/code/swaks/,swaks).
.vitem &%-bhc%&&~<&'IP&~address'&>
.oindex "&%-bhc%&"
.oindex "&%-bmalware%&"
.cindex "testing", "malware"
.cindex "malware scan test"
-This debugging option causes Exim to scan the given file,
+This debugging option causes Exim to scan the given file or directory
+(depending on the used scanner interface),
using the malware scanning framework. The option of &%av_scanner%& influences
this option, so if &%av_scanner%&'s value is dependent upon an expansion then
the expansion should have defaults which apply to this invocation. ACLs are
If &%config%& is given as an argument, the config is
output, as it was parsed, any include file resolved, any comment removed.
-If &%config_file%& is given as an argument, the name of the run time
+If &%config_file%& is given as an argument, the name of the runtime
configuration file is output. (&%configure_file%& works too, for
backward compatibility.)
If a list of configuration files was supplied, the value that is output here
settings can be obtained by using &%routers%&, &%transports%&, or
&%authenticators%&.
+.cindex "environment"
+If &%environment%& is given as an argument, the set of environment
+variables is output, line by line. Using the &%-n%& flag suppresses the value of the
+variables.
+
.cindex "options" "macro &-- extracting"
If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
are available, similarly to the drivers. Because macros are sometimes used
for storing passwords, this option is restricted.
The output format is one item per line.
+For the "-bP macro <name>" form, if no such macro is found
+the exit status will be nonzero.
.vitem &%-bp%&
.oindex "&%-bp%&"
-.cindex "queue" "listing messages on"
-.cindex "listing" "messages on the queue"
+.cindex "queue" "listing messages in"
+.cindex "listing" "messages in the queue"
This option requests a listing of the contents of the mail queue on the
standard output. If the &%-bp%& option is followed by a list of message ids,
just those messages are listed. By default, this option can be used only by an
admin user. However, the &%queue_list_requires_admin%& option can be set false
to allow any user to see the queue.
-Each message on the queue is displayed as in the following example:
+Each message in the queue is displayed as in the following example:
.code
25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
red.king@looking-glass.fict.example
.endd
.cindex "message" "size in queue listing"
.cindex "size" "of message"
-The first line contains the length of time the message has been on the queue
+The first line contains the length of time the message has been in the queue
(in this case 25 minutes), the size of the message (2.9K), the unique local
identifier for the message, and the message sender, as contained in the
envelope. For bounce messages, the sender address is empty, and appears as
.vitem &%-bpc%&
.oindex "&%-bpc%&"
.cindex "queue" "count of messages on"
-This option counts the number of messages on the queue, and writes the total
+This option counts the number of messages in the queue, and writes the total
to the standard output. It is restricted to admin users, unless
&%queue_list_requires_admin%& is set false.
.oindex "&%-bpr%&"
This option operates like &%-bp%&, but the output is not sorted into
chronological order of message arrival. This can speed it up when there are
-lots of messages on the queue, and is particularly useful if the output is
+lots of messages in the queue, and is particularly useful if the output is
going to be post-processed in a way that doesn't need the sorting.
.vitem &%-bpra%&
number, and compilation date of the &'exim'& binary to the standard output.
It also lists the DBM library that is being used, the optional modules (such as
specific lookup types), the drivers that are included in the binary, and the
-name of the run time configuration file that is in use.
+name of the runtime configuration file that is in use.
As part of its operation, &%-bV%& causes Exim to read and syntax check its
configuration file. However, this is a static check only. It cannot check
.cindex "configuration file" "alternate"
.cindex "CONFIGURE_FILE"
.cindex "alternate configuration file"
-This option causes Exim to find the run time configuration file from the given
+This option causes Exim to find the runtime configuration file from the given
list instead of from the list specified by the CONFIGURE_FILE
-compile-time setting. Usually, the list will consist of just a single file
-name, but it can be a colon-separated list of names. In this case, the first
+compile-time setting. Usually, the list will consist of just a single filename,
+but it can be a colon-separated list of names. In this case, the first
file that exists is used. Failure to open an existing file stops Exim from
proceeding any further along the list, and an error is generated.
running as the Exim user, so when it re-executes to regain privilege for the
delivery, the use of &%-C%& causes privilege to be lost. However, root can
test reception and delivery using two separate commands (one to put a message
-on the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
+in the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
prefix string with which any file named in a &%-C%& command line option
-must start. In addition, the file name must not contain the sequence &`/../`&.
+must start. In addition, the filename must not contain the sequence &`/../`&.
However, if the value of the &%-C%& option is identical to the value of
CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
-unset, any file name can be used with &%-C%&.
+unset, any filename can be used with &%-C%&.
ALT_CONFIG_PREFIX can be used to confine alternative configuration files
to a directory to which only root has access. This prevents someone who has
exim '-D ABC = something' ...
.endd
&%-D%& may be repeated up to 10 times on a command line.
-.new
Only macro names up to 22 letters long can be set.
-.wen
.vitem &%-d%&<&'debug&~options'&>
&<<CHAPlocalscan>>&)
&`lookup `& general lookup code and all lookups
&`memory `& memory handling
-&`pid `& add pid to debug output lines
+&`noutf8 `& modifier: avoid UTF-8 line-drawing
+&`pid `& modifier: add pid to debug output lines
&`process_info `& setting info for the process log
&`queue_run `& queue runs
&`receive `& general message reception logic
&`retry `& retry handling
&`rewrite `& address rewriting
&`route `& address routing
-&`timestamp `& add timestamp to debug output lines
+&`timestamp `& modifier: add timestamp to debug output lines
&`tls `& TLS logic
&`transport `& transports
&`uid `& changes of uid/gid and looking up uid/gid
of all debug output lines. This can be useful when trying to track down delays
in processing.
+.cindex debugging "UTF-8 in"
+.cindex UTF-8 "in debug output"
+The &`noutf8`& selector disables the use of
+UTF-8 line-drawing characters to group related information.
+When disabled. ascii-art is used instead.
+Using the &`+all`& option does not set this modifier,
+
If the &%debug_print%& option is set in any driver, it produces output whenever
any debugging is selected, or if &%-v%& is used.
.cindex "sender" "address"
.cindex "address" "sender"
.cindex "trusted users"
+.cindex "envelope from"
.cindex "envelope sender"
.cindex "user" "trusted"
This option sets the address of the envelope sender of a locally-generated
by Exim in conjunction with the &%-MC%& option. It signifies that the
remote host supports the ESMTP &_DSN_& extension.
+.vitem &%-MCG%&&~<&'queue&~name'&>
+.oindex "&%-MCG%&"
+This option is not intended for use by external callers. It is used internally
+by Exim in conjunction with the &%-MC%& option. It signifies that an
+alternate queue is used, named by the following argument.
+
+.vitem &%-MCK%&
+.oindex "&%-MCK%&"
+This option is not intended for use by external callers. It is used internally
+by Exim in conjunction with the &%-MC%& option. It signifies that a
+remote host supports the ESMTP &_CHUNKING_& extension.
+
.vitem &%-MCP%&
.oindex "&%-MCP%&"
This option is not intended for use by external callers. It is used internally
by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
host to which Exim is connected supports TLS encryption.
+.vitem &%-MCt%&&~<&'IP&~address'&>&~<&'port'&>&~<&'cipher'&>
+.oindex "&%-MCt%&"
+This option is not intended for use by external callers. It is used internally
+by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
+connection is being proxied by a parent process for handling TLS encryption.
+The arguments give the local address and port being proxied, and the TLS cipher.
+
.vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
.oindex "&%-Mc%&"
.cindex "hints database" "not overridden by &%-Mc%&"
.cindex "delivery" "manually started &-- not forced"
-This option requests Exim to run a delivery attempt on each message in turn,
+This option requests Exim to run a delivery attempt on each message, in turn,
but unlike the &%-M%& option, it does check for retry hints, and respects any
that are found. This option is not very useful to external callers. It is
provided mainly for internal use by Exim when it needs to re-invoke itself in
Bounce messages are just discarded. This option can be used only by an admin
user.
+.new
+.vitem &%-MG%&&~<&'queue&~name'&&~<&'message&~id'&>&~<&'message&~id'&>&~...
+.oindex "&%-MG%&"
+.cindex queue named
+.cindex "named queues"
+.cindex "queue" "moving messages"
+This option requests that each listed message be moved from its current
+queue to the given named queue.
+The destination queue name argument is required, but can be an empty
+string to define the default queue.
+If the messages are not currently located in the default queue,
+a &%-qG<name>%& option will be required to define the source queue.
+.wen
+
.vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
.oindex "&%-Mmad%&"
.cindex "delivery" "cancelling all"
bounce messages are sent; each message is simply forgotten. However, if any of
the messages are active, their status is not altered. This option can be used
only by an admin user or by the user who originally caused the message to be
-placed on the queue.
+placed in the queue.
+
+. .new
+. .vitem &%-MS%&
+. .oindex "&%-MS%&"
+. .cindex REQUIRETLS
+. This option is used to request REQUIRETLS processing on the message.
+. It is used internally by Exim in conjunction with -E when generating
+. a bounce message.
+. .wen
.vitem &%-Mset%&&~<&'message&~id'&>
-.oindex "&%-Mset%&
+.oindex "&%-Mset%&"
.cindex "testing" "string expansion"
.cindex "expansion" "testing"
This option is useful only in conjunction with &%-be%& (that is, when testing
.oindex "&%-n%&"
This option is interpreted by Sendmail to mean &"no aliasing"&.
For normal modes of operation, it is ignored by Exim.
-When combined with &%-bP%& it suppresses the name of an option from being output.
+When combined with &%-bP%& it makes the output more terse (suppresses
+option names, environment values and config pretty printing).
.vitem &%-O%&&~<&'data'&>
.oindex "&%-O%&"
.oindex "&%-oA%&"
.cindex "Sendmail compatibility" "&%-oA%& option"
This option is used by Sendmail in conjunction with &%-bi%& to specify an
-alternative alias file name. Exim handles &%-bi%& differently; see the
+alternative alias filename. Exim handles &%-bi%& differently; see the
description above.
.vitem &%-oB%&&~<&'n'&>
false and one of the queueing options in the configuration file is in effect.
If there is a temporary delivery error during foreground delivery, the
-message is left on the queue for later delivery, and the original reception
+message is left in the queue for later delivery, and the original reception
process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
restricted configuration that never queues messages.
This option applies to all modes in which Exim accepts incoming messages,
including the listening daemon. It specifies that the accepting process should
not automatically start a delivery process for each message received. Messages
-are placed on the queue, and remain there until a subsequent queue runner
+are placed in the queue, and remain there until a subsequent queue runner
process encounters them. There are several configuration options (such as
&%queue_only%&) that can be used to queue incoming messages under certain
conditions. This option overrides all of them and also &%-odqs%&. It always
message, in the background by default, but in the foreground if &%-odi%& is
also present. The recipient addresses are routed, and local deliveries are done
in the normal way. However, if any SMTP deliveries are required, they are not
-done at this time, so the message remains on the queue until a subsequent queue
+done at this time, so the message remains in the queue until a subsequent queue
runner process encounters it. Because routing was done, Exim knows which
messages are waiting for which hosts, and so a number of messages for the same
host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
SMTP protocol names (see the description of &$received_protocol$& in section
&<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
-be set by &%-oMr%&.
+be set by &%-oMr%&. Repeated use of this option is not supported.
.vitem &%-oMs%&&~<&'host&~name'&>
.oindex "&%-oMs%&"
is also given. It controls which ports and interfaces the daemon uses. Details
of the syntax, and how it interacts with configuration file options, are given
in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
-file is written unless &%-oP%& is also present to specify a pid file name.
+file is written unless &%-oP%& is also present to specify a pid filename.
.vitem &%-pd%&
.oindex "&%-pd%&"
Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
or &`s`& using this option (but that does not seem a real limitation).
+Repeated use of this option is not supported.
.vitem &%-q%&
.oindex "&%-q%&"
and &%-S%& options).
.cindex "queue runner" "description of operation"
-The &%-q%& option starts one queue runner process. This scans the queue of
+If other commandline options do not specify an action,
+the &%-q%& option starts one queue runner process. This scans the queue of
waiting messages, and runs a delivery process for each one in turn. It waits
for each delivery process to finish before starting the next one. A delivery
process may not actually do any deliveries if the retry times for the addresses
.cindex "queue" "initial delivery"
If the &'i'& flag is present, the queue runner runs delivery processes only for
those messages that haven't previously been tried. (&'i'& stands for &"initial
-delivery"&.) This can be helpful if you are putting messages on the queue using
+delivery"&.) This can be helpful if you are putting messages in the queue using
&%-odq%& and want a queue runner just to process the new messages.
.vitem &%-q[q][i]f...%&
.oindex "&%-ql%&"
.cindex "queue" "local deliveries only"
The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
-be done. If a message requires any remote deliveries, it remains on the queue
+be done. If a message requires any remote deliveries, it remains in the queue
for later delivery.
-.vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
+.vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
+.oindex "&%-qG%&"
+.cindex queue named
+.cindex "named queues"
.cindex "queue" "delivering specific messages"
+If the &'G'& flag and a name is present, the queue runner operates on the
+queue with the given name rather than the default queue.
+The name should not contain a &'/'& character.
+For a periodic queue run (see below)
+append to the name a slash and a time value.
+
+If other commandline options specify an action, a &'-qG<name>'& option
+will specify a queue to operate on.
+For example:
+.code
+exim -bp -qGquarantine
+mailq -qGquarantine
+exim -qGoffpeak -Rf @special.domain.example
+.endd
+
+.vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
When scanning the queue, Exim can be made to skip over messages whose ids are
lexically less than a given value by following the &%-q%& option with a
starting message id. For example:
. ////////////////////////////////////////////////////////////////////////////
-.chapter "The Exim run time configuration file" "CHAPconf" &&&
+.chapter "The Exim runtime configuration file" "CHAPconf" &&&
"The runtime configuration file"
-.cindex "run time configuration"
+.cindex "runtime configuration"
.cindex "configuration file" "general description"
.cindex "CONFIGURE_FILE"
.cindex "configuration file" "errors in"
.cindex "error" "in configuration file"
.cindex "return code" "for bad configuration"
-Exim uses a single run time configuration file that is read whenever an Exim
+Exim uses a single runtime configuration file that is read whenever an Exim
binary is executed. Note that in normal operation, this happens frequently,
because Exim is designed to operate in a distributed manner, without central
control.
The name of the configuration file is compiled into the binary for security
reasons, and is specified by the CONFIGURE_FILE compilation option. In
most configurations, this specifies a single file. However, it is permitted to
-give a colon-separated list of file names, in which case Exim uses the first
+give a colon-separated list of filenames, in which case Exim uses the first
existing file in the list.
.cindex "EXIM_USER"
.cindex "CONFIGURE_GROUP"
.cindex "configuration file" "ownership"
.cindex "ownership" "configuration file"
-The run time configuration file must be owned by root or by the user that is
+The runtime configuration file must be owned by root or by the user that is
specified at compile time by the CONFIGURE_OWNER option (if set). The
configuration file must not be world-writeable, or group-writeable unless its
group is the root group or the one specified at compile time by the
CONFIGURE_GROUP option.
&*Warning*&: In a conventional configuration, where the Exim binary is setuid
-to root, anybody who is able to edit the run time configuration file has an
+to root, anybody who is able to edit the runtime configuration file has an
easy way to run commands as root. If you specify a user or group in the
CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
who are members of that group will trivially be able to obtain root privileges.
-Up to Exim version 4.72, the run time configuration file was also permitted to
+Up to Exim version 4.72, the runtime configuration file was also permitted to
be writeable by the Exim user and/or group. That has been changed in Exim 4.73
since it offered a simple privilege escalation for any attacker who managed to
compromise the Exim user account.
A default configuration file, which will work correctly in simple situations,
is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
-defines just one file name, the installation process copies the default
+defines just one filename, the installation process copies the default
configuration to a new file of that name if it did not previously exist. If
CONFIGURE_FILE is a list, no default is automatically installed. Chapter
&<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
Exim is running as the Exim user, so when it re-execs to regain privilege for
the delivery, the use of &%-C%& causes privilege to be lost. However, root
can test reception and delivery using two separate commands (one to put a
-message on the queue, using &%-odq%&, and another to do the delivery, using
+message in the queue, using &%-odq%&, and another to do the delivery, using
&%-M%&).
If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
prefix string with which any file named in a &%-C%& command line option must
-start. In addition, the file name must not contain the sequence &"&`/../`&"&.
-There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any file
-name can be used with &%-C%&.
+start. In addition, the filename must not contain the sequence &"&`/../`&"&.
+There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any
+filename can be used with &%-C%&.
One-off changes to a configuration can be specified by the &%-D%& command line
option, which defines and overrides values for macros used inside the
Some sites may wish to use the same Exim binary on different machines that
share a file system, but to use different configuration files on each machine.
If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
-looks for a file whose name is the configuration file name followed by a dot
+looks for a file whose name is the configuration filename followed by a dot
and the machine's node name, as obtained from the &[uname()]& function. If this
file does not exist, the standard name is tried. This processing occurs for
-each file name in the list given by CONFIGURE_FILE or &%-C%&.
+each filename in the list given by CONFIGURE_FILE or &%-C%&.
In some esoteric situations different versions of Exim may be run under
different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
.cindex "configuration file" "including other files"
.cindex "&`.include`& in configuration file"
.cindex "&`.include_if_exists`& in configuration file"
-You can include other files inside Exim's run time configuration file by
+You can include other files inside Exim's runtime configuration file by
using this syntax:
.display
-&`.include`& <&'file name'&>
-&`.include_if_exists`& <&'file name'&>
+&`.include`& <&'filename'&>
+&`.include_if_exists`& <&'filename'&>
.endd
-on a line by itself. Double quotes round the file name are optional. If you use
+on a line by itself. Double quotes round the filename are optional. If you use
the first form, a configuration error occurs if the file does not exist; the
-second form does nothing for non-existent files. In all cases, an absolute file
-name is required.
+second form does nothing for non-existent files.
+The first form allows a relative name. It is resolved relative to
+the directory of the including file. For the second form an absolute filename
+is required.
Includes may be nested to any depth, but remember that Exim reads its
configuration file often, so it is a good idea to keep them to a minimum.
.section "Macro substitution" "SECID42"
Once a macro is defined, all subsequent lines in the file (and any included
files) are scanned for the macro name; if there are several macros, the line is
-scanned for each in turn, in the order in which the macros are defined. The
+scanned for each, in turn, in the order in which the macros are defined. The
replacement text is not re-scanned for the current macro, though it is scanned
for subsequently defined macros. For this reason, a macro name may not contain
the name of a previously defined macro as a substring. You could, for example,
section &<<SECTnamedlists>>&.
+.section "Builtin macros" "SECTbuiltinmacros"
+Exim defines some macros depending on facilities available, which may
+differ due to build-time definitions and from one release to another.
+All of these macros start with an underscore.
+They can be used to conditionally include parts of a configuration
+(see below).
+
+The following classes of macros are defined:
+.display
+&` _HAVE_* `& build-time defines
+&` _DRIVER_ROUTER_* `& router drivers
+&` _DRIVER_TRANSPORT_* `& transport drivers
+&` _DRIVER_AUTHENTICATOR_* `& authenticator drivers
+&` _LOG_* `& log_selector values
+&` _OPT_MAIN_* `& main config options
+&` _OPT_ROUTERS_* `& generic router options
+&` _OPT_TRANSPORTS_* `& generic transport options
+&` _OPT_AUTHENTICATORS_* `& generic authenticator options
+&` _OPT_ROUTER_*_* `& private router options
+&` _OPT_TRANSPORT_*_* `& private transport options
+&` _OPT_AUTHENTICATOR_*_* `& private authenticator options
+.endd
+
+Use an &"exim -bP macros"& command to get the list of macros.
+
+
.section "Conditional skips in the configuration file" "SECID46"
.cindex "configuration file" "conditional skips"
.cindex "&`.ifdef`&"
hexadecimal number.
If an integer value is followed by the letter K, it is multiplied by 1024; if
-it is followed by the letter M, it is multiplied by 1024x1024. When the values
+it is followed by the letter M, it is multiplied by 1024x1024;
+if by the letter G, 1024x1024x1024.
+When the values
of integer option settings are output, values which are an exact multiple of
1024 or 1024x1024 are sometimes, but not always, printed using the letters K
and M. The printing style is independent of the actual input format that was
+.section "Macros" "SECTdefconfmacros"
+All macros should be defined before any options.
+
+One macro is specified, but commented out, in the default configuration:
+.code
+# ROUTER_SMARTHOST=MAIL.HOSTNAME.FOR.CENTRAL.SERVER.EXAMPLE
+.endd
+If all off-site mail is expected to be delivered to a "smarthost", then set the
+hostname here and uncomment the macro. This will affect which router is used
+later on. If this is left commented out, then Exim will perform direct-to-MX
+deliveries using a &(dnslookup)& router.
+
+In addition to macros defined here, Exim includes a number of built-in macros
+to enable configuration to be guarded by a binary built with support for a
+given feature. See section &<<SECTbuiltinmacros>>& for more details.
+
+
.section "Main configuration settings" "SECTdefconfmain"
-The main (global) configuration option settings must always come first in the
-file. The first thing you'll see in the file, after some initial comments, is
-the line
+The main (global) configuration option settings section must always come first
+in the file, after the macros.
+The first thing you'll see in the file, after some initial comments, is the line
.code
# primary_hostname =
.endd
These are example settings that can be used when Exim is compiled with
support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
first one specifies the list of clients that are allowed to use TLS when
-connecting to this server; in this case the wildcard means all clients. The
+connecting to this server; in this case, the wildcard means all clients. The
other options specify where Exim should find its TLS certificate and private
key, which together prove the server's identity to any clients that connect.
More details are given in chapter &<<CHAPTLS>>&.
.cindex "port" "465 and 587"
.cindex "port" "for message submission"
.cindex "message" "submission, ports for"
-.cindex "ssmtp protocol"
+.cindex "submissions protocol"
.cindex "smtps protocol"
+.cindex "ssmtp protocol"
+.cindex "SMTP" "submissions protocol"
.cindex "SMTP" "ssmtp protocol"
.cindex "SMTP" "smtps protocol"
These options provide better support for roaming users who wish to use this
server for message submission. They are not much use unless you have turned on
TLS (as described in the previous paragraph) and authentication (about which
-more in section &<<SECTdefconfauth>>&). The usual SMTP port 25 is often blocked
-on end-user networks, so RFC 4409 specifies that message submission should use
-port 587 instead. However some software (notably Microsoft Outlook) cannot be
-configured to use port 587 correctly, so these settings also enable the
-non-standard &"smtps"& (aka &"ssmtp"&) port 465 (see section
-&<<SECTsupobssmt>>&).
+more in section &<<SECTdefconfauth>>&).
+Mail submission from mail clients (MUAs) should be separate from inbound mail
+to your domain (MX delivery) for various good reasons (eg, ability to impose
+much saner TLS protocol and ciphersuite requirements without unintended
+consequences).
+RFC 6409 (previously 4409) specifies use of port 587 for SMTP Submission,
+which uses STARTTLS, so this is the &"submission"& port.
+RFC 8314 specifies use of port 465 as the &"submissions"& protocol,
+which should be used in preference to 587.
+You should also consider deploying SRV records to help clients find
+these ports.
+Older names for &"submissions"& are &"smtps"& and &"ssmtp"&.
Two more commented-out options settings follow:
.code
This is an almost obsolete form of explicit email routing. If you do not know
anything about it, you can safely ignore this topic.
-The last two settings in the main part of the default configuration are
+The next two settings in the main part of the default configuration are
concerned with messages that have been &"frozen"& on Exim's queue. When a
message is frozen, Exim no longer continues to try to deliver it. Freezing
occurs when a bounce message encounters a permanent failure because the sender
timeout_frozen_after = 7d
.endd
The first of these options specifies that failing bounce messages are to be
-discarded after 2 days on the queue. The second specifies that any frozen
+discarded after 2 days in the queue. The second specifies that any frozen
message (whether a bounce message or not) is to be timed out (and discarded)
after a week. In this configuration, the first setting ensures that no failing
bounce message ever lasts a week.
+Exim queues it's messages in a spool directory. If you expect to have
+large queues, you may consider using this option. It splits the spool
+directory into subdirectories to avoid file system degradation from
+many files in a single directory, resulting in better performance.
+Manual manipulation of queued messages becomes more complex (though fortunately
+not often needed).
+.code
+# split_spool_directory = true
+.endd
+
+In an ideal world everybody follows the standards. For non-ASCII
+messages RFC 2047 is a standard, allowing a maximum line length of 76
+characters. Exim adheres that standard and won't process messages which
+violate this standard. (Even ${rfc2047:...} expansions will fail.)
+In particular, the Exim maintainers have had multiple reports of
+problems from Russian administrators of issues until they disable this
+check, because of some popular, yet buggy, mail composition software.
+.code
+# check_rfc2047_length = false
+.endd
+
+If you need to be strictly RFC compliant you may wish to disable the
+8BITMIME advertisement. Use this, if you exchange mails with systems
+that are not 8-bit clean.
+.code
+# accept_8bitmime = false
+.endd
+
+Libraries you use may depend on specific environment settings. This
+imposes a security risk (e.g. PATH). There are two lists:
+&%keep_environment%& for the variables to import as they are, and
+&%add_environment%& for variables we want to set to a fixed value.
+Note that TZ is handled separately, by the $%timezone%$ runtime
+option and by the TIMEZONE_DEFAULT buildtime option.
+.code
+# keep_environment = ^LDAP
+# add_environment = PATH=/usr/bin::/bin
+.endd
.section "ACL configuration" "SECID54"
&"&'first-initial.second-initial.family-name'&"& when applied to someone like
the author of Exim, who has no second initial.) However, a local part starting
with a dot or containing &"/../"& can cause trouble if it is used as part of a
-file name (for example, for a mailing list). This is also true for local parts
+filename (for example, for a mailing list). This is also true for local parts
that contain slashes. A pipe symbol can also be troublesome if the local part
is incorporated unthinkingly into a shell command line.
begin routers
.endd
Routers are the modules in Exim that make decisions about where to send
-messages. An address is passed to each router in turn, until it is either
+messages. An address is passed to each router, in turn, until it is either
accepted, or failed. This means that the order in which you define the routers
matters. Each router is fully described in its own chapter later in this
manual. Here we give only brief overviews.
support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
you uncomment this router, you also need to uncomment the setting of
&%allow_domain_literals%& in the main part of the configuration.
+
+Which router is used next depends upon whether or not the ROUTER_SMARTHOST
+macro has been defined, per
.code
+.ifdef ROUTER_SMARTHOST
+smarthost:
+#...
+.else
dnslookup:
- driver = dnslookup
+#...
+.endif
+.endd
+
+If ROUTER_SMARTHOST has been defined, either at the top of the file or on the
+command-line, then we route all non-local mail to that smarthost; otherwise, we'll
+perform DNS lookups for direct-to-MX lookup. Any mail which is to a local domain will
+skip these routers because of the &%domains%& option.
+
+.code
+smarthost:
+ driver = manualroute
domains = ! +local_domains
- transport = remote_smtp
- ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
+ transport = smarthost_smtp
+ route_data = ROUTER_SMARTHOST
+ ignore_target_hosts = <; 0.0.0.0 ; 127.0.0.0/8 ; ::1
no_more
.endd
-The first uncommented router handles addresses that do not involve any local
-domains. This is specified by the line
+This router only handles mail which is not to any local domains; this is
+specified by the line
.code
domains = ! +local_domains
.endd
indicates that it is referring to a named list. Addresses in other domains are
passed on to the following routers.
+The name of the router driver is &(manualroute)& because we are manually
+specifying how mail should be routed onwards, instead of using DNS MX.
+While the name of this router instance is arbitrary, the &%driver%& option must
+be one of the driver modules that is in the Exim binary.
+
+With no pre-conditions other than &%domains%&, all mail for non-local domains
+will be handled by this router, and the &%no_more%& setting will ensure that no
+other routers will be used for messages matching the pre-conditions. See
+&<<SECTrouprecon>>& for more on how the pre-conditions apply. For messages which
+are handled by this router, we provide a hostname to deliver to in &%route_data%&
+and the macro supplies the value; the address is then queued for the
+&(smarthost_smtp)& transport.
+
+.code
+dnslookup:
+ driver = dnslookup
+ domains = ! +local_domains
+ transport = remote_smtp
+ ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
+ no_more
+.endd
+The &%domains%& option behaves as per smarthost, above.
+
The name of the router driver is &(dnslookup)&,
and is specified by the &%driver%& option. Do not be confused by the fact that
the name of this router instance is the same as the name of the driver. The
.code
begin transports
.endd
-One remote transport and four local transports are defined.
+Two remote transports and four local transports are defined.
.code
remote_smtp:
driver = smtp
+ message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
+.ifdef _HAVE_PRDR
hosts_try_prdr = *
+.endif
.endd
This transport is used for delivering messages over SMTP connections.
The list of remote hosts comes from the router.
-The &%hosts_try_prdr%& option enables an efficiency SMTP option.
-It is negotiated between client and server
-and not expected to cause problems but can be disabled if needed.
+The &%message_size_limit%& usage is a hack to avoid sending on messages
+with over-long lines. The built-in macro _HAVE_DANE guards configuration
+to use DANE for delivery;
+see section &<<SECDANE>>& for more details.
+
+The &%hosts_try_prdr%& option enables an efficiency SMTP option. It is
+negotiated between client and server and not expected to cause problems
+but can be disabled if needed. The built-in macro _HAVE_PRDR guards the
+use of the &%hosts_try_prdr%& configuration option.
+
+The other remote transport is used when delivering to a specific smarthost
+with whom there must be some kind of existing relationship, instead of the
+usual federated system.
+
+.code
+smarthost_smtp:
+ driver = smtp
+ message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
+ multi_domain
+ #
+.ifdef _HAVE_TLS
+ # Comment out any of these which you have to, then file a Support
+ # request with your smarthost provider to get things fixed:
+ hosts_require_tls = *
+ tls_verify_hosts = *
+ # As long as tls_verify_hosts is enabled, this won't matter, but if you
+ # have to comment it out then this will at least log whether you succeed
+ # or not:
+ tls_try_verify_hosts = *
+ #
+ # The SNI name should match the name which we'll expect to verify;
+ # many mail systems don't use SNI and this doesn't matter, but if it does,
+ # we need to send a name which the remote site will recognize.
+ # This _should_ be the name which the smarthost operators specified as
+ # the hostname for sending your mail to.
+ tls_sni = ROUTER_SMARTHOST
+ #
+.ifdef _HAVE_OPENSSL
+ tls_require_ciphers = HIGH:!aNULL:@STRENGTH
+.endif
+.ifdef _HAVE_GNUTLS
+ tls_require_ciphers = SECURE192:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1
+.endif
+.endif
+.ifdef _HAVE_PRDR
+ hosts_try_prdr = *
+.endif
+.endd
+After the same &%message_size_limit%& hack, we then specify that this Transport
+can handle messages to multiple domains in one run. The assumption here is
+that you're routing all non-local mail to the same place and that place is
+happy to take all messages from you as quickly as possible.
+All other options depend upon built-in macros; if Exim was built without TLS support
+then no other options are defined.
+If TLS is available, then we configure "stronger than default" TLS ciphersuites
+and versions using the &%tls_require_ciphers%& option, where the value to be
+used depends upon the library providing TLS.
+Beyond that, the options adopt the stance that you should have TLS support available
+from your smarthost on today's Internet, so we turn on requiring TLS for the
+mail to be delivered, and requiring that the certificate be valid, and match
+the expected hostname. The &%tls_sni%& option can be used by service providers
+to select an appropriate certificate to present to you and here we re-use the
+ROUTER_SMARTHOST macro, because that is unaffected by CNAMEs present in DNS.
+You want to specify the hostname which you'll expect to validate for, and that
+should not be subject to insecure tampering via DNS results.
+
+For the &%hosts_try_prdr%& option see the previous transport.
+
All other options are defaulted.
.code
local_delivery:
This causes any temporarily failing address to be retried every 15 minutes for
2 hours, then at intervals starting at one hour and increasing by a factor of
1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
-is not delivered after 4 days of temporary failure, it is bounced.
+is not delivered after 4 days of temporary failure, it is bounced. The time is
+measured from first failure, not from the time the message was received.
If the retry section is removed from the configuration, or is empty (that is,
if no retry rules are defined), Exim will not retry deliveries. This turns
Exim supports the use of regular expressions in many of its options. It
uses the PCRE regular expression library; this provides regular expression
matching that is compatible with Perl 5. The syntax and semantics of
-regular expressions is discussed in many Perl reference books, and also in
+regular expressions is discussed in
+online Perl manpages, in
+many Perl reference books, and also in
Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
+. --- the http: URL here redirects to another page with the ISBN in the URL
+. --- where trying to use https: just redirects back to http:, so sticking
+. --- to the old URL for now. 2018-09-07.
The documentation for the syntax and semantics of the regular expressions that
are supported by PCRE is included in the PCRE distribution, and no further
string without a terminating binary zero. The cdb format is designed for
indexed files that are read frequently and never updated, except by total
re-creation. As such, it is particularly suitable for large files containing
-aliases or other indexed data referenced by an MTA. Information about cdb can
-be found in several places:
+aliases or other indexed data referenced by an MTA. Information about cdb and
+tools for building the files can be found in several places:
.display
-&url(http://www.pobox.com/~djb/cdb.html)
-&url(ftp://ftp.corpit.ru/pub/tinycdb/)
-&url(http://packages.debian.org/stable/utils/freecdb.html)
+&url(https://cr.yp.to/cdb.html)
+&url(https://www.corpit.ru/mjt/tinycdb.html)
+&url(https://packages.debian.org/stable/utils/freecdb)
+&url(https://github.com/philpennock/cdbtools) (in Go)
.endd
A cdb distribution is not needed in order to build Exim with cdb support,
because the code for reading cdb files is included directly in Exim itself.
&*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
the implicit key is the host's IP address rather than its name (see section
&<<SECThoslispatsikey>>&).
+
+.new
+&*Warning 3*&: Do not use an IPv4-mapped IPv6 address for a key; use the
+IPv4, in dotted-quad form. (Exim converts IPv4-mapped IPv6 addresses to this
+notation before executing the lookup.)
+.wen
+.next
+.new
+.cindex lookup json
+.cindex json "lookup type"
+.cindex JSON expansions
+&(json)&: The given file is a text file with a JSON structure.
+An element of the structure is extracted, defined by the search key.
+The key is a list of subelement selectors
+(colon-separated by default but changeable in the usual way)
+which are applied in turn to select smaller and smaller portions
+of the JSON structure.
+If a selector is numeric, it must apply to a JSON array; the (zero-based)
+nunbered array element is selected.
+Otherwise it must apply to a JSON object; the named element is selected.
+The final resulting element can be a simple JSON type or a JSON object
+or array; for the latter two a string-representation os the JSON
+is returned.
+For elements of type string, the returned value is de-quoted.
+.wen
.next
.cindex "linear search"
.cindex "lookup" "lsearch"
&*Warning*&: Unlike most other single-key lookup types, a file of data for
&((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
lookup types support only literal keys.
+
+.next
+.cindex "lookup" "spf"
+If Exim is built with SPF support, manual lookups can be done
+(as opposed to the standard ACL condition method.
+For details see section &<<SECSPF>>&.
.endlist ilist
-.section "Query-style lookup types" "SECID62"
+.section "Query-style lookup types" "SECTquerystylelookups"
.cindex "lookup" "query-style types"
.cindex "query-style lookup" "list of types"
The supported query-style lookup types are listed below. Further details about
PostgreSQL database. See section &<<SECTsql>>&.
.next
-.new
.cindex "Redis lookup type"
.cindex lookup Redis
-&(redis)&: The format of the query is an SQL statement that is passed to a
-Redis database. See section &<<SECTsql>>&.
-.wen
+&(redis)&: The format of the query is either a simple get or simple set,
+passed to a Redis database. See section &<<SECTsql>>&.
.next
.cindex "sqlite lookup type"
.cindex "lookup" "sqlite"
-&(sqlite)&: The format of the query is a file name followed by an SQL statement
+&(sqlite)&: The format of the query is a filename followed by an SQL statement
that is passed to an SQLite database. See section &<<SECTsqlite>>&.
.next
.next
.cindex "whoson lookup type"
.cindex "lookup" "whoson"
+. --- still http:-only, 2018-09-07
&(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
allows a server to check whether a particular (dynamically allocated) IP
address is currently allocated to a known (trusted) user and, optionally, to
With &"strict"& a response from the DNS resolver that
is not labelled as authenticated data
is treated as equivalent to a temporary DNS error.
-The default is &"never"&.
+The default is &"lax"&.
See also the &$lookup_dnssec_authenticated$& variable.
The form if &"retry_VAL"& where VAL is an integer.
The default count is set by the main configuration option &%dns_retry%&.
-.new
-.cindex cacheing "of dns lookup"
+.cindex caching "of dns lookup"
.cindex TTL "of dns lookup"
.cindex DNS TTL
Dnsdb lookup results are cached within a single process (and its children).
The cache entry lifetime is limited to the smallest time-to-live (TTL)
value of the set of returned DNS records.
-.wen
.section "Pseudo dnsdb record types" "SECID66"
found, but that is still a successful query. In other words, the list of
servers provides a backup facility, not a list of different places to look.
-.new
For Redis the global option need not be specified if all queries contain their
own server information &-- see section &<<SECTspeserque>>&.
If specified, the option must be set to a colon-separated list of server
.next
The password is optional; if present it is used to authenticate to the backend
.endlist
-.wen
-.new
The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
respectively, and the characters single-quote, double-quote, and backslash
The &%quote_redis%& expansion operator
escapes whitespace and backslash characters with a backslash.
-.wen
.section "Specifying the server in the query" "SECTspeserque"
For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
causes a connection to the server on the local host by means of a Unix domain
socket. An alternate socket can be specified in parentheses.
-.new
An option group name for MySQL option files can be specified in square brackets;
the default value is &"exim"&.
-.wen
The full syntax of each item in &%mysql_servers%& is:
.display
<&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
.section "More about SQLite" "SECTsqlite"
.cindex "lookup" "SQLite"
.cindex "sqlite lookup type"
-SQLite is different to the other SQL lookups because a file name is required in
+SQLite is different to the other SQL lookups because a filename is required in
addition to the SQL query. An SQLite database is a single file, and there is no
daemon as in the other SQL databases. The interface to Exim requires the name
of the file, as an absolute path, to be given at the start of the query. It is
waits for the lock to be released. In Exim, the default timeout is set
to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
option.
+
+.section "More about Redis" "SECTredis"
+.cindex "lookup" "Redis"
+.cindex "redis lookup type"
+Redis is a non-SQL database. Commands are simple get and set.
+Examples:
+.code
+${lookup redis{set keyname ${quote_redis:objvalue plus}}}
+${lookup redis{get keyname}}
+.endd
+
+As of release 4.91, "lightweight" support for Redis Cluster is available.
+Requires &%redis_servers%& list to contain all the servers in the cluster, all
+of which must be reachable from the running exim instance. If the cluster has
+master/slave replication, the list must contain all the master and slave
+servers.
+
+When the Redis Cluster returns a "MOVED" response to a query, Exim does not
+immediately follow the redirection but treats the response as a DEFER, moving on
+to the next server in the &%redis_servers%& list until the correct server is
+reached.
+
.ecindex IIDfidalo1
.ecindex IIDfidalo2
-.section "Expansion of lists" "SECID75"
+.section "Expansion of lists" "SECTlistexpand"
.cindex "expansion" "of lists"
-Each list is expanded as a single string before it is used. The result of
+Each list is expanded as a single string before it is used.
+
+&'Exception: the router headers_remove option, where list-item
+splitting is done before string-expansion.'&
+
+The result of
expansion must be a list, possibly containing empty items, which is split up
into separate items for matching. By default, colon is the separator character,
but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
.section "File names in lists" "SECTfilnamlis"
-.cindex "list" "file name in"
-If an item in a domain, host, address, or local part list is an absolute file
-name (beginning with a slash character), each line of the file is read and
+.cindex "list" "filename in"
+If an item in a domain, host, address, or local part list is an absolute
+filename (beginning with a slash character), each line of the file is read and
processed as if it were an independent item in the list, except that further
-file names are not allowed,
+filenames are not allowed,
and no expansion of the data from the file takes place.
Empty lines in the file are ignored, and the file may also contain comment
lines:
.endd
.endlist
-Putting a file name in a list has the same effect as inserting each line of the
+Putting a filename in a list has the same effect as inserting each line of the
file as an item in the list (blank lines and comments excepted). However, there
is one important difference: the file is read each time the list is processed,
so if its contents vary over time, Exim's behaviour changes.
-If a file name is preceded by an exclamation mark, the sense of any match
+If a filename is preceded by an exclamation mark, the sense of any match
within the file is inverted. For example, if
.code
hold_domains = !/etc/nohold-domains
always fixed strings, just as for any other single-key lookup type.
If you want to use a file to contain wild-card patterns that form part of a
-list, just give the file name on its own, without a search type, as described
+list, just give the filename on its own, without a search type, as described
in the previous section. You could also use the &(wildlsearch)& or
&(nwildlsearch)&, but there is no advantage in doing this.
.cindex "domain list" "matching by lookup"
If a pattern starts with the name of a single-key lookup type followed by a
semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
-must be a file name in a suitable format for the lookup type. For example, for
+must be a filename in a suitable format for the lookup type. For example, for
&"cdb;"& it must be an absolute path:
.code
domains = cdb;/etc/mail/local_domains.cdb
recently implemented &(iplsearch)& files do require colons in IPv6 keys
(notated using the quoting facility) so as to distinguish them from IPv4 keys.
For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
-converted using colons and not dots. In all cases, full, unabbreviated IPv6
+converted using colons and not dots.
+.new
+In all cases except IPv4-mapped IPv6, full, unabbreviated IPv6
addresses are always used.
+The latter are converted to IPv4 addresses, in dotted-quad form.
+.wen
Ideally, it would be nice to tidy up this anomalous situation by changing to
colons in all cases, given that quoting is now available for &(lsearch)&.
The domain portion of an address is always lowercased before matching it to an
address list. The local part is lowercased by default, and any string
comparisons that take place are done caselessly. This means that the data in
-the address list itself, in files included as plain file names, and in any file
+the address list itself, in files included as plain filenames, and in any file
that is looked up using the &"@@"& mechanism, can be in any case. However, the
keys in files that are looked up by a search type other than &(lsearch)& (which
works caselessly) must be in lower case, because these lookups are not
.chapter "String expansions" "CHAPexpand"
.scindex IIDstrexp "expansion" "of strings"
-Many strings in Exim's run time configuration are expanded before use. Some of
+Many strings in Exim's runtime configuration are expanded before use. Some of
them are expanded every time they are used; others are expanded only once.
When a string is being expanded it is copied verbatim from left to right except
+.cindex expansion "string concatenation"
when a dollar or backslash character is encountered. A dollar specifies the
start of a portion of the string that is interpreted and replaced as described
below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
options for which string expansion is performed are marked with † after
the data type. ACL rules always expand strings. A couple of expansion
conditions do not expand some of the brace-delimited branches, for security
-reasons.
+reasons,
+.new
+.cindex "tainted data" expansion
+.cindex expansion "tainted data"
+and expansion of data deriving from the sender (&"tainted data"&)
+is not permitted.
+.wen
.oindex "&%-bem%&"
If you want to test expansions that include variables whose values are taken
from a message, there are two other options that can be used. The &%-bem%&
-option is like &%-be%& except that it is followed by a file name. The file is
+option is like &%-be%& except that it is followed by a filename. The file is
read as a message before doing the test expansions. For example:
.code
exim -bem /tmp/test.message '$h_subject:'
If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
+.vitem "&*${authresults{*&<&'authserv-id'&>&*}}*&"
+.cindex authentication "results header"
+.cindex headers "authentication-results:"
+.cindex authentication "expansion item"
+This item returns a string suitable for insertion as an
+&'Authentication-Results:'&
+header line.
+The given <&'authserv-id'&> is included in the result; typically this
+will be a domain name identifying the system performing the authentications.
+Methods that might be present in the result include:
+.code
+none
+iprev
+auth
+spf
+dkim
+.endd
+
+Example use (as an ACL modifier):
+.code
+ add_header = :at_start:${authresults {$primary_hostname}}
+.endd
+This is safe even if no authentication results are available.
+
+
.vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
-.cindex "expansion" "extracting cerificate fields"
+.cindex "expansion" "extracting certificate fields"
.cindex "&%certextract%&" "certificate fields"
.cindex "certificate" "extracting fields"
The <&'certificate'&> must be a variable of type certificate.
.vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
.cindex "expansion" "extracting value from environment"
-.cindex "environment" "value from"
+.cindex "environment" "values from"
The key is first expanded separately, and leading and trailing white space
removed.
This is then searched for as a name in the environment.
If {<&'string1'&>} is omitted the search result is substituted on
search success.
+The environment is adjusted by the &%keep_environment%& and
+&%add_environment%& main section options.
+
.vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
{*&<&'string3'&>&*}}*&"
.cindex "&%extract%&" "substrings by key"
The key and <&'string1'&> are first expanded separately. Leading and trailing
white space is removed from the key (but not from any of the strings). The key
-must not consist entirely of digits. The expanded <&'string1'&> must be of the
-form:
+must not be empty and must not consist entirely of digits.
+The expanded <&'string1'&> must be of the form:
.display
<&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
.endd
This forces an expansion failure (see section &<<SECTforexpfai>>&);
{<&'string2'&>} must be present for &"fail"& to be recognized.
+.vitem "&*${extract json{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
+ {*&<&'string3'&>&*}}*&" &&&
+ "&*${extract jsons{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
+ {*&<&'string3'&>&*}}*&"
+.cindex "expansion" "extracting from JSON object"
+.cindex JSON expansions
+The key and <&'string1'&> are first expanded separately. Leading and trailing
+white space is removed from the key (but not from any of the strings). The key
+must not be empty and must not consist entirely of digits.
+The expanded <&'string1'&> must be of the form:
+.display
+{ <&'"key1"'&> : <&'value1'&> , <&'"key2"'&> , <&'value2'&> ... }
+.endd
+.vindex "&$value$&"
+The braces, commas and colons, and the quoting of the member name are required;
+the spaces are optional.
+Matching of the key against the member names is done case-sensitively.
+For the &"json"& variant,
+if a returned value is a JSON string, it retains its leading and
+trailing quotes.
+.new
+For the &"jsons"& variant, which is intended for use with JSON strings, the
+leading and trailing quotes are removed from the returned value.
+.wen
+. XXX should be a UTF-8 compare
+
+The results of matching are handled as above.
+
.vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
empty (for example, the fifth field above).
+.vitem "&*${extract json {*&<&'number'&>&*}}&&&
+ {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&" &&&
+ "&*${extract jsons{*&<&'number'&>&*}}&&&
+ {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
+.cindex "expansion" "extracting from JSON array"
+.cindex JSON expansions
+The <&'number'&> argument must consist entirely of decimal digits,
+apart from leading and trailing white space, which is ignored.
+
+Field selection and result handling is as above;
+there is no choice of field separator.
+For the &"json"& variant,
+if a returned value is a JSON string, it retains its leading and
+trailing quotes.
+.new
+For the &"jsons"& variant, which is intended for use with JSON strings, the
+leading and trailing quotes are removed from the returned value.
+.wen
+
+
.vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
.cindex "list" "selecting by condition"
.cindex "expansion" "selecting from list by condition"
.vindex "&$item$&"
After expansion, <&'string'&> is interpreted as a list, colon-separated by
-default, but the separator can be changed in the usual way. For each item
+default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
+For each item
in this list, its value is place in &$item$&, and then the condition is
evaluated. If the condition is true, &$item$& is added to the output as an
item in a new list; if the condition is false, the item is discarded. The
separator used for the output list is the same as the one used for the
input, but a separator setting is not included in the output. For example:
.code
-${filter{a:b:c}{!eq{$item}{b}}
+${filter{a:b:c}{!eq{$item}{b}}}
.endd
yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
-to what it was before. See also the &*map*& and &*reduce*& expansion items.
+to what it was before. See also the &%map%& and &%reduce%& expansion items.
.vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
&*$h_*&<&'header&~name'&>&*:*&" &&&
"&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
&*$bh_*&<&'header&~name'&>&*:*&" &&&
+ "&*$lheader_*&<&'header&~name'&>&*:*&&~or&~&&&
+ &*$lh_*&<&'header&~name'&>&*:*&"
"&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
&*$rh_*&<&'header&~name'&>&*:*&"
.cindex "expansion" "header insertion"
.vindex "&$header_$&"
.vindex "&$bheader_$&"
+.vindex "&$lheader_$&"
.vindex "&$rheader_$&"
.cindex "header lines" "in expansion strings"
.cindex "header lines" "character sets"
internal newlines (caused by splitting the header line over several physical
lines) may be present.
-The difference between &%rheader%&, &%bheader%&, and &%header%& is in the way
+The difference between the four pairs of expansions is in the way
the data in the header line is interpreted.
.ilist
&%rheader%& gives the original &"raw"& content of the header line, with no
processing at all, and without the removal of leading and trailing white space.
+.next
+.cindex "list" "of header lines"
+&%lheader%& gives a colon-separated list, one element per header when there
+are multiple headers with a given name.
+Any embedded colon characters within an element are doubled, so normal Exim
+list-processing facilities can be used.
+The terminating newline of each element is removed; in other respects
+the content is &"raw"&.
+
.next
.cindex "base64 encoding" "in header lines"
&%bheader%& removes leading and trailing white space, and then decodes base64
filter. Header lines that are added to a particular copy of a message by a
router or transport are not accessible.
-For incoming SMTP messages, no header lines are visible in ACLs that are obeyed
-before the DATA ACL, because the header structure is not set up until the
-message is received. Header lines that are added in a RCPT ACL (for example)
+For incoming SMTP messages, no header lines are visible in
+ACLs that are obeyed before the data phase completes,
+because the header structure is not set up until the message is received.
+They are visible in DKIM, PRDR and DATA ACLs.
+Header lines that are added in a RCPT ACL (for example)
are saved until the message's incoming header lines are available, at which
-point they are added. When a DATA ACL is running, however, header lines added
-by earlier ACLs are visible.
+point they are added.
+When any of the above ACLs ar
+running, however, header lines added by earlier ACLs are visible.
Upper case and lower case letters are synonymous in header names. If the
following character is white space, the terminating colon may be omitted, but
&'X-Spam-Scanned:'& header line. If you know the secret, you can check that
this header line is authentic by recomputing the authentication code from the
host name, message ID and the &'Message-id:'& header line. This can be done
-using Exim's &%-be%& option, or by other means, for example by using the
+using Exim's &%-be%& option, or by other means, for example, by using the
&'hmac_md5_hex()'& function in Perl.
-.new
.vitem &*${imapfolder{*&<&'foldername'&>&*}}*&
.cindex expansion "imap folder"
.cindex "&%imapfolder%& expansion item"
This item converts a (possibly multilevel, or with non-ASCII characters)
folder specification to a Maildir name for filesystem use.
For information on internationalisation support see &<<SECTi18nMDA>>&.
-.wen
.code
${length_<n>:<string>}
.endd
-The result of this item is either the first <&'n'&> characters or the whole
+The result of this item is either the first <&'n'&> bytes or the whole
of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
&%strlen%&, which gives the length of a string.
+All measurement is done in bytes and is not UTF-8 aware.
.vitem "&*${listextract{*&<&'number'&>&*}&&&
and leading and trailing white space (which is ignored).
After expansion, <&'string1'&> is interpreted as a list, colon-separated by
-default, but the separator can be changed in the usual way.
+default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
The first field of the list is numbered one.
If the number is negative, the fields are
.cindex "expansion" "list creation"
.vindex "&$item$&"
After expansion, <&'string1'&> is interpreted as a list, colon-separated by
-default, but the separator can be changed in the usual way. For each item
+default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
+For each item
in this list, its value is place in &$item$&, and then <&'string2'&> is
expanded and added to the output as an item in a new list. The separator used
for the output list is the same as the one used for the input, but a separator
${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
.endd
expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
-value of &$item$& is restored to what it was before. See also the &*filter*&
-and &*reduce*& expansion items.
+value of &$item$& is restored to what it was before. See also the &%filter%&
+and &%reduce%& expansion items.
.vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
.cindex "expansion" "numeric hash"
.cindex "expansion" "inserting an entire file"
.cindex "file" "inserting into expansion"
.cindex "&%readfile%& expansion item"
-The file name and end-of-line string are first expanded separately. The file is
+The filename and end-of-line string are first expanded separately. The file is
then read, and its contents replace the entire item. All newline characters in
the file are replaced by the end-of-line string if it is present. Otherwise,
newlines are left in the string.
.vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
- {*&<&'timeout'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
+ {*&<&'options'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
.cindex "expansion" "inserting from a socket"
.cindex "socket, use of in expansion"
.cindex "&%readsocket%& expansion item"
Only a single host name may be given, but if looking it up yields more than
one IP address, they are each tried in turn until a connection is made. For
both kinds of socket, Exim makes a connection, writes the request string
-(unless it is an empty string) and reads from the socket until an end-of-file
+unless it is an empty string; and no terminating NUL is ever sent)
+and reads from the socket until an end-of-file
is read. A timeout of 5 seconds is applied. Additional, optional arguments
extend what can be done. Firstly, you can vary the timeout. For example:
.code
${readsocket{/socket/name}{request string}{3s}}
.endd
+
+The third argument is a list of options, of which the first element is the timeout
+and must be present if the argument is given.
+Further elements are options of form &'name=value'&.
+Two option types is currently recognised: shutdown and tls.
+The first defines whether (the default)
+or not a shutdown is done on the connection after sending the request.
+Example, to not do so (preferred, eg. by some webservers):
+.code
+${readsocket{/socket/name}{request string}{3s:shutdown=no}}
+.endd
+The second, tls, controls the use of TLS on the connection. Example:
+.code
+${readsocket{/socket/name}{request string}{3s:tls=yes}}
+.endd
+The default is to not use TLS.
+If it is enabled, a shutdown as descripbed above is never done.
+
A fourth argument allows you to change any newlines that are in the data
that is read, in the same way as for &%readfile%& (see above). This example
turns them into spaces:
.vindex "&$item$&"
This operation reduces a list to a single, scalar string. After expansion,
<&'string1'&> is interpreted as a list, colon-separated by default, but the
-separator can be changed in the usual way. Then <&'string2'&> is expanded and
+separator can be changed in the usual way (&<<SECTlistsepchange>>&).
+Then <&'string2'&> is expanded and
assigned to the &$value$& variable. After this, each item in the <&'string1'&>
-list is assigned to &$item$& in turn, and <&'string3'&> is expanded for each of
+list is assigned to &$item$&, in turn, and <&'string3'&> is expanded for each of
them. The result of that expansion is assigned to &$value$& before the next
iteration. When the end of the list is reached, the final value of &$value$& is
-added to the expansion output. The &*reduce*& expansion item can be used in a
+added to the expansion output. The &%reduce%& expansion item can be used in a
number of ways. For example, to add up a list of numbers:
.code
${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
.endd
At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
-restored to what they were before. See also the &*filter*& and &*map*&
+restored to what they were before. See also the &%filter%& and &%map%&
expansion items.
.vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
This item inserts &"raw"& header lines. It is described with the &%header%&
-expansion item above.
+expansion item in section &<<SECTexpansionitems>>& above.
.vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
{*&<&'string2'&>&*}}*&"
${sg{abcdefabcdef}{abc}{xyz}}
.endd
yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
-if any $ or \ characters are required in the regular expression or in the
+if any $, } or \ characters are required in the regular expression or in the
substitution string, they have to be escaped. For example:
.code
${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
the regular expression from string expansion.
+The regular expression is compiled in 8-bit mode, working against bytes
+rather than any Unicode-aware character handling.
.vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
.cindex list sorting
.cindex expansion "list sorting"
After expansion, <&'string'&> is interpreted as a list, colon-separated by
-default, but the separator can be changed in the usual way.
+default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
The <&'comparator'&> argument is interpreted as the operator
of a two-argument expansion condition.
The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
If the starting offset is greater than the string length the result is the
null string; if the length plus starting offset is greater than the string
length, the result is the right-hand part of the string, starting from the
-given offset. The first character in the string has offset zero.
+given offset. The first byte (character) in the string has offset zero.
The &%substr%& expansion item can take negative offset values to count
-from the right-hand end of its operand. The last character is offset -1, the
-second-last is offset -2, and so on. Thus, for example,
+from the right-hand end of its operand. The last byte (character) is offset -1,
+the second-last is offset -2, and so on. Thus, for example,
.code
${substr{-5}{2}{1234567}}
.endd
yields &"1"&.
When the second number is omitted from &%substr%&, the remainder of the string
-is taken if the offset is positive. If it is negative, all characters in the
+is taken if the offset is positive. If it is negative, all bytes (characters) in the
string preceding the offset point are taken. For example, an offset of -1 and
no length, as in these semantically identical examples:
.code
.endd
yields all but the last character of the string, that is, &"abcd"&.
+All measurement is done in bytes and is not UTF-8 aware.
+
.vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
{*&<&'replacements'&>&*}}*&"
.cindex "expansion" "character translation"
.cindex "&%tr%& expansion item"
-This item does single-character translation on its subject string. The second
+This item does single-character (in bytes) translation on its subject string. The second
argument is a list of characters to be translated in the subject string. Each
matching character is replaced by the corresponding character from the
replacement list. For example
last occurrence is used. If the third string is shorter than the second, its
last character is replicated. However, if it is empty, no translation takes
place.
+
+All character handling is done in bytes and is not UTF-8 aware.
+
.endlist
header line, and the effective address is extracted from it. If the string does
not parse successfully, the result is empty.
+The parsing correctly handles SMTPUTF8 Unicode in the string.
+
.vitem &*${addresses:*&<&'string'&>&*}*&
.cindex "expansion" "RFC 2822 address handling"
.code
${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
.endd
-expands to &`ceo@up.stairs&&sec@base.ment`&. Compare the &*address*& (singular)
+expands to &`ceo@up.stairs&&sec@base.ment`&. The string is expanded
+first, so if the expanded string starts with >, it may change the output
+separator unintentionally. This can be avoided by setting the output
+separator explicitly:
+.code
+${addresses:>:$h_from:}
+.endd
+
+Compare the &%address%& (singular)
expansion item, which extracts the working address from a single RFC2822
-address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
+address. See the &%filter%&, &%map%&, and &%reduce%& items for ways of
processing lists.
To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
example below is passed the contents of &`$header_from:`&, meaning it gets
de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
The third example shows that the presence of a comma is skipped when it is
-quoted.
+quoted. The fourth example shows SMTPUTF8 handling.
.code
# exim -be '${addresses:From: \
=?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
Last:user@example.com
# exim -be '${addresses:From: "Last, First" <user@example.com>}'
user@example.com
+# exim -be '${addresses:フィル <フィリップ@example.jp>}'
+フィリップ@example.jp
.endd
+.vitem &*${base32:*&<&'digits'&>&*}*&
+.cindex "&%base32%& expansion item"
+.cindex "expansion" "conversion to base 32"
+The string must consist entirely of decimal digits. The number is converted to
+base 32 and output as a (empty, for zero) string of characters.
+Only lowercase letters are used.
+
+.vitem &*${base32d:*&<&'base-32&~digits'&>&*}*&
+.cindex "&%base32d%& expansion item"
+.cindex "expansion" "conversion to base 32"
+The string must consist entirely of base-32 digits.
+The number is converted to decimal and output as a string.
+
.vitem &*${base62:*&<&'digits'&>&*}*&
.cindex "&%base62%& expansion item"
.cindex "expansion" "conversion to base 62"
The string must consist entirely of decimal digits. The number is converted to
base 62 and output as a string of six characters, including leading zeros. In
the few operating environments where Exim uses base 36 instead of base 62 for
-its message identifiers (because those systems do not have case-sensitive file
-names), base 36 is used by this operator, despite its name. &*Note*&: Just to
-be absolutely clear: this is &'not'& base64 encoding.
+its message identifiers (because those systems do not have case-sensitive
+filenames), base 36 is used by this operator, despite its name. &*Note*&: Just
+to be absolutely clear: this is &'not'& base64 encoding.
.vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
.cindex "&%base62d%& expansion item"
identifiers, base-36 digits. The number is converted to decimal and output as a
string.
-.new
.vitem &*${base64:*&<&'string'&>&*}*&
.cindex "expansion" "base64 encoding"
.cindex "base64 encoding" "in string expansion"
.cindex "base64 decoding" "in string expansion"
.cindex "&%base64d%& expansion item"
This operator converts a base64-encoded string into the un-coded form.
-.wen
.vitem &*${domain:*&<&'string'&>&*}*&
significant bit set (so-called &"8-bit characters"&) count as printing or not
is controlled by the &%print_topbitchars%& option.
+.vitem &*${escape8bit:*&<&'string'&>&*}*&
+.cindex "expansion" "escaping 8-bit characters"
+.cindex "&%escape8bit%& expansion item"
+If the string contains and characters with the most significant bit set,
+they are converted to escape sequences starting with a backslash.
+Backslashes and DEL characters are also converted.
+
.vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
.cindex "expansion" "expression evaluation"
.cindex "expansion" "hex to base64"
.cindex "&%hex2b64%& expansion item"
This operator converts a hex string into one that is base64 encoded. This can
-be useful for processing the output of the MD5 and SHA-1 hashing functions.
+be useful for processing the output of the various hashing functions.
.cindex "&%hexquote%& expansion item"
This operator converts non-printable characters in a string into a hex
escape form. Byte values between 33 (!) and 126 (~) inclusive are left
-as is, and other byte values are converted to &`\xNN`&, for example a
+as is, and other byte values are converted to &`\xNN`&, for example, a
byte value 127 is converted to &`\x7f`&.
-.new
.vitem &*${ipv6denorm:*&<&'string'&>&*}*&
.cindex "&%ipv6denorm%& expansion item"
.cindex "IP address" normalisation
set of zero-valued groups is replaced with a double colon.
A trailing ipv4-style dotted-decimal set is converted to hex.
Pure IPv4 addresses are converted to IPv4-mapped IPv6.
-.wen
.vitem &*${lc:*&<&'string'&>&*}*&
.code
${lc:$local_part}
.endd
+Case is defined per the system C locale.
.vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
.cindex "expansion" "string truncation"
See the description of the general &%length%& item above for details. Note that
&%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
when &%length%& is used as an operator.
+All measurement is done in bytes and is not UTF-8 aware.
.vitem &*${listcount:*&<&'string'&>&*}*&
The string is interpreted as an RFC 2822 address and the local part is
extracted from it. If the string does not parse successfully, the result is
empty.
+The parsing correctly handles SMTPUTF8 Unicode in the string.
.vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
If you are creating a new email address from the contents of &$local_part$&
(or any other unknown data), you should always use this operator.
+This quoting determination is not SMTPUTF8-aware, thus quoting non-ASCII data
+will likely use the quoting form.
+Thus &'${quote_local_part:フィル}'& will always become &'"フィル"'&.
+
.vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
.cindex "quoting" "lookup-specific"
.cindex "SHA-1 hash"
.cindex "expansion" "SHA-1 hashing"
.cindex certificate fingerprint
-.cindex "&%sha2%& expansion item"
+.cindex "&%sha1%& expansion item"
The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
it as a 40-digit hexadecimal number, in which any letters are in upper case.
returns the SHA-1 hash fingerprint of the certificate.
-.vitem &*${sha256:*&<&'certificate'&>&*}*&
+.vitem &*${sha256:*&<&'string'&>&*}*& &&&
+ &*${sha2:*&<&'string'&>&*}*& &&&
+ &*${sha2_<n>:*&<&'string'&>&*}*&
.cindex "SHA-256 hash"
+.cindex "SHA-2 hash"
.cindex certificate fingerprint
.cindex "expansion" "SHA-256 hashing"
.cindex "&%sha256%& expansion item"
-The &%sha256%& operator computes the SHA-256 hash fingerprint of the
-certificate,
+.cindex "&%sha2%& expansion item"
+The &%sha256%& operator computes the SHA-256 hash value of the string
and returns
it as a 64-digit hexadecimal number, in which any letters are in upper case.
-Only arguments which are a single variable of certificate type are supported.
+
+If the string is a single variable of type certificate,
+returns the SHA-256 hash fingerprint of the certificate.
+
+.new
+The operator can also be spelled &%sha2%& and does the same as &%sha256%&
+(except for certificates, which are not supported).
+Finally, if an underbar
+and a number is appended it specifies the output length, selecting a
+member of the SHA-2 family of hash functions.
+Values of 256, 384 and 512 are accepted, with 256 being the default.
+.wen
+
+
+.vitem &*${sha3:*&<&'string'&>&*}*& &&&
+ &*${sha3_<n>:*&<&'string'&>&*}*&
+.cindex "SHA3 hash"
+.cindex "expansion" "SHA3 hashing"
+.cindex "&%sha3%& expansion item"
+The &%sha3%& operator computes the SHA3-256 hash value of the string
+and returns
+it as a 64-digit hexadecimal number, in which any letters are in upper case.
+
+If a number is appended, separated by an underbar, it specifies
+the output length. Values of 224, 256, 384 and 512 are accepted;
+with 256 being the default.
+
+The &%sha3%& expansion item is only supported if Exim has been
+compiled with GnuTLS 3.5.0 or later,
+or OpenSSL 1.1.1 or later.
+The macro "_CRYPTO_HASH_SHA3" will be defined if it is supported.
.vitem &*${stat:*&<&'string'&>&*}*&
.vitem &*${str2b64:*&<&'string'&>&*}*&
.cindex "&%str2b64%& expansion item"
-.new
Now deprecated, a synonym for the &%base64%& expansion operator.
-.wen
.cindex "&%strlen%& expansion item"
The item is replace by the length of the expanded string, expressed as a
decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
+All measurement is done in bytes and is not UTF-8 aware.
.vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
.endd
See the description of the general &%substr%& item above for details. The
abbreviation &%s%& can be used when &%substr%& is used as an operator.
+All measurement is done in bytes and is not UTF-8 aware.
.vitem &*${time_eval:*&<&'string'&>&*}*&
.cindex "&%time_eval%& expansion item"
.cindex "expansion" "case forcing"
.cindex "&%uc%& expansion item"
This forces the letters in the string into upper-case.
+Case is defined per the system C locale.
.vitem &*${utf8clean:*&<&'string'&>&*}*&
.cindex "correction of invalid utf-8 sequences in strings"
.cindex "expansion" "utf-8 forcing"
.cindex "&%utf8clean%& expansion item"
This replaces any invalid utf-8 sequence in the string by the character &`?`&.
+In versions of Exim before 4.92, this did not correctly do so for a truncated
+final codepoint's encoding, and the character would be silently dropped.
+If you must handle detection of this scenario across both sets of Exim behavior,
+the complexity will depend upon the task.
+For instance, to detect if the first character is multibyte and a 1-byte
+extraction can be successfully used as a path component (as is common for
+dividing up delivery folders), you might use:
+.code
+condition = ${if inlist{${utf8clean:${length_1:$local_part}}}{:?}{yes}{no}}
+.endd
+(which will false-positive if the first character of the local part is a
+literal question mark).
-.new
.vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
"&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
"&*${utf8_localpart_to_alabel:*&<&'string'&>&*}*&" &&&
.cindex "&%utf8_localpart_from_alabel%& expansion item"
These convert EAI mail name components between UTF-8 and a-label forms.
For information on internationalisation support see &<<SECTi18nMTA>>&.
-.wen
.endlist
.cindex "&%eqi%& expansion condition"
The two substrings are first expanded. The condition is true if the two
resulting strings are identical. For &%eq%& the comparison includes the case of
-letters, whereas for &%eqi%& the comparison is case-independent.
+letters, whereas for &%eqi%& the comparison is case-independent, where
+case is defined per the system C locale.
.vitem &*exists&~{*&<&'file&~name'&>&*}*&
.cindex "expansion" "file existence test"
.vindex "&$item$&"
These conditions iterate over a list. The first argument is expanded to form
the list. By default, the list separator is a colon, but it can be changed by
-the normal method. The second argument is interpreted as a condition that is to
+the normal method (&<<SECTlistsepchange>>&).
+The second argument is interpreted as a condition that is to
be applied to each item in the list in turn. During the interpretation of the
condition, the current list item is placed in a variable called &$item$&.
.ilist
.code
${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
.endd
-The value of &$item$& is saved and restored while &*forany*& or &*forall*& is
+The value of &$item$& is saved and restored while &%forany%& or &%forall%& is
being processed, to enable these expansion items to be nested.
To scan a named list, expand it with the &*listnamed*& operator.
+.new
+.vitem "&*forall_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
+ "&*forany_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
+ "&*forall_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
+ "&*forany_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&"
+.cindex JSON "iterative conditions"
+.cindex JSON expansions
+.cindex expansion "&*forall_json*& condition"
+.cindex expansion "&*forany_json*& condition"
+.cindex expansion "&*forall_jsons*& condition"
+.cindex expansion "&*forany_jsons*& condition"
+As for the above, except that the first argument must, after expansion,
+be a JSON array.
+The array separator is not changeable.
+For the &"jsons"& variants the elements are expected to be JSON strings
+and have their quotes removed before the evaluation of the condition.
+.wen
+
+
.vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
&*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
string is lexically greater than or equal to the second string. For &%ge%& the
comparison includes the case of letters, whereas for &%gei%& the comparison is
case-independent.
+Case and collation order are defined per the system C locale.
.vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
&*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
string is lexically greater than the second string. For &%gt%& the comparison
includes the case of letters, whereas for &%gti%& the comparison is
case-independent.
+Case and collation order are defined per the system C locale.
.vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
&*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
Both strings are expanded; the second string is treated as a list of simple
strings; if the first string is a member of the second, then the condition
is true.
+For the case-independent &%inlisti%& condition, case is defined per the system C locale.
These are simpler to use versions of the more powerful &*forany*& condition.
Examples, and the &*forany*& equivalents:
hexadecimal digits. There may be fewer than eight components if an empty
component (adjacent colons) is present. Only one empty component is permitted.
-&*Note*&: The checks are just on the form of the address; actual numerical
-values are not considered. Thus, for example, 999.999.999.999 passes the IPv4
-check. The main use of these tests is to distinguish between IP addresses and
+&*Note*&: The checks used to be just on the form of the address; actual numerical
+values were not considered. Thus, for example, 999.999.999.999 passed the IPv4
+check.
+This is no longer the case.
+
+The main use of these tests is to distinguish between IP addresses and
host names, or between IPv4 and IPv6 addresses. For example, you could use
.code
${if isip4{$sender_host_address}...
string is lexically less than or equal to the second string. For &%le%& the
comparison includes the case of letters, whereas for &%lei%& the comparison is
case-independent.
+Case and collation order are defined per the system C locale.
.vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
&*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
string is lexically less than the second string. For &%lt%& the comparison
includes the case of letters, whereas for &%lti%& the comparison is
case-independent.
+Case and collation order are defined per the system C locale.
.vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
and it may match anywhere in the subject, not just at the start. If you want
the pattern to match at the end of the subject, you must include the &`$`&
metacharacter at an appropriate point.
+All character handling is done in bytes and is not UTF-8 aware,
+but we might change this in a future Exim release.
.cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
At the start of an &%if%& expansion the values of the numeric variable
${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
.endd
In each case, the second argument may contain any of the allowable items for a
-list of the appropriate type. Also, because the second argument (after
-expansion) is a standard form of list, it is possible to refer to a named list.
+list of the appropriate type. Also, because the second argument
+is a standard form of list, it is possible to refer to a named list.
Thus, you can use conditions like this:
.code
${if match_domain{$domain}{+local_domains}{...
.cindex "expansion" "PAM authentication test"
.cindex "&%pam%& expansion condition"
&'Pluggable Authentication Modules'&
-(&url(http://www.kernel.org/pub/linux/libs/pam/)) are a facility that is
+(&url(https://mirrors.edge.kernel.org/pub/linux/libs/pam/)) are a facility that is
available in the latest releases of Solaris and in some GNU/Linux
distributions. The Exim support, which is intended for use in conjunction with
the SMTP AUTH command, is available only if Exim is compiled with
In some operating systems, PAM authentication can be done only from a process
running as root. Since Exim is running as the Exim user when receiving
messages, this means that PAM cannot be used directly in those systems.
-A patched version of the &'pam_unix'& module that comes with the
-Linux PAM package is available from &url(http://www.e-admin.de/pam_exim/).
-The patched module allows one special uid/gid combination, in addition to root,
-to authenticate. If you build the patched module to allow the Exim user and
-group, PAM can then be used from an Exim authenticator.
+. --- 2018-09-07: the pam_exim modified variant has gone, removed claims re using Exim via that
.vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
user/password authenticator configuration might preserve the user name for use
in the routers. Note that this is not the same information that is saved in
&$sender_host_authenticated$&.
+
When a message is submitted locally (that is, not over a TCP connection)
the value of &$authenticated_id$& is normally the login name of the calling
process. However, a trusted user can override this by means of the &%-oMai%&
command line option.
+This second case also sets up information used by the
+&$authresults$& expansion item.
.vitem &$authenticated_fail_id$&
.cindex "authentication" "fail" "id"
.vindex "&$compile_number$&"
The building process for Exim keeps a count of the number
of times it has been compiled. This serves to distinguish different
-compilations of the same version of the program.
+compilations of the same version of Exim.
.vitem &$config_dir$&
.vindex "&$config_dir$&"
.vindex "&$config_file$&"
The name of the main configuration file Exim is using.
-.vitem &$demime_errorlevel$&
-.vindex "&$demime_errorlevel$&"
-This variable is available when Exim is compiled with
-the content-scanning extension and the obsolete &%demime%& condition. For
-details, see section &<<SECTdemimecond>>&.
+.new
+.vitem &$dmarc_domain_policy$& &&&
+ &$dmarc_status$& &&&
+ &$dmarc_status_text$& &&&
+ &$dmarc_used_domains$&
+Results of DMARC verification.
+For details see section &<<SECDMARC>>&.
+.wen
-.vitem &$demime_reason$&
-.vindex "&$demime_reason$&"
-This variable is available when Exim is compiled with the
-content-scanning extension and the obsolete &%demime%& condition. For details,
-see section &<<SECTdemimecond>>&.
+.vitem &$dkim_verify_status$&
+Results of DKIM verification.
+For details see section &<<SECDKIMVFY>>&.
.vitem &$dkim_cur_signer$& &&&
- &$dkim_verify_status$& &&&
&$dkim_verify_reason$& &&&
&$dkim_domain$& &&&
&$dkim_identity$& &&&
&$dkim_key_notes$& &&&
&$dkim_key_length$&
These variables are only available within the DKIM ACL.
-For details see chapter &<<CHAPdkim>>&.
+For details see section &<<SECDKIMVFY>>&.
.vitem &$dkim_signers$&
.vindex &$dkim_signers$&
When a message has been received this variable contains
a colon-separated list of signer domains and identities for the message.
-For details see chapter &<<CHAPdkim>>&.
+For details see section &<<SECDKIMVFY>>&.
.vitem &$dnslist_domain$& &&&
&$dnslist_matched$& &&&
The first character is a major version number, currently 4.
Then after a dot, the next group of digits is a minor version number.
There may be other characters following the minor version.
-
-.vitem &$found_extension$&
-.vindex "&$found_extension$&"
-This variable is available when Exim is compiled with the
-content-scanning extension and the obsolete &%demime%& condition. For details,
-see section &<<SECTdemimecond>>&.
+This value may be overridden by the &%exim_version%& main config option.
.vitem &$header_$&<&'name'&>
This is not strictly an expansion variable. It is expansion syntax for
inserting the message header line with the given name. Note that the name must
be terminated by colon or white space, because it may contain a wide variety of
characters. Note also that braces must &'not'& be used.
+See the full description in section &<<SECTexpansionitems>>& above.
.vitem &$headers_added$&
.vindex "&$headers_added$&"
by a setting on the transport itself.
When running a filter test via the &%-bf%& option, &$home$& is set to the value
-of the environment variable HOME.
+of the environment variable HOME, which is subject to the
+&%keep_environment%& and &%add_environment%& main config options.
.vitem &$host$&
.vindex "&$host$&"
the result, the name is not accepted, and &$host_lookup_deferred$& is set to
&"1"&. See also &$sender_host_name$&.
+.cindex authentication "expansion item"
+Performing these checks sets up information used by the
+&%authresults%& expansion item.
+
+
.vitem &$host_lookup_failed$&
.vindex "&$host_lookup_failed$&"
See &$host_lookup_deferred$&.
This variable is set to the remote host's TCP port whenever &$host$& is set
for an outbound connection.
+.vitem &$initial_cwd$&
+.vindex "&$initial_cwd$&
+This variable contains the full path name of the initial working
+directory of the current Exim process. This may differ from the current
+working directory, as Exim changes this to "/" during early startup, and
+to &$spool_directory$& later.
.vitem &$inode$&
.vindex "&$inode$&"
.vindex "&$local_part_prefix$&"
.vindex "&$local_part_suffix$&"
+.cindex affix variables
If a local part prefix or suffix has been recognized, it is not included in the
value of &$local_part$& during routing and subsequent delivery. The values of
any prefix or suffix are in &$local_part_prefix$& and
When a message is being delivered to a file, pipe, or autoreply transport as a
result of aliasing or forwarding, &$local_part$& is set to the local part of
-the parent address, not to the file name or command (see &$address_file$& and
+the parent address, not to the filename or command (see &$address_file$& and
&$address_pipe$&).
When an ACL is running for a RCPT command, &$local_part$& contains the
.vitem &$local_part_prefix$&
.vindex "&$local_part_prefix$&"
+.cindex affix variables
When an address is being routed or delivered, and a
specific prefix for the local part was recognized, it is available in this
variable, having been removed from &$local_part$&.
This variable contains the number of bytes in the longest line that was
received as part of the message, not counting the line termination
character(s).
+It is not valid if the &%spool_files_wireformat%& option is used.
.vitem &$message_age$&
.cindex "message" "age of"
separates the body from the header. Newlines are included in the count. See
also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
+If the spool file is wireformat
+(see the &%spool_files_wireformat%& main option)
+the CRLF line-terminators are included in the count.
+
.vitem &$message_exim_id$&
.vindex "&$message_exim_id$&"
When a message is being received or delivered, this variable contains the
In the MAIL and RCPT ACLs, the value is zero because at that stage the
message has not yet been received.
+This variable is not valid if the &%spool_files_wireformat%& option is used.
+
.vitem &$message_size$&
.cindex "size" "of message"
.cindex "message" "size"
.cindex "uid (user id)" "of originating user"
.cindex "sender" "uid"
.vindex "&$caller_uid$&"
-.vindex "&$originaltor_uid$&"
+.vindex "&$originator_uid$&"
The value of &$caller_uid$& that was set when the message was received. For
messages received via the command line, this is the uid of the sending user.
For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
qualified host name. See also &$smtp_active_hostname$&.
-.new
-.vitem &$proxy_host_address$& &&&
- &$proxy_host_port$& &&&
- &$proxy_target_address$& &&&
- &$proxy_target_port$& &&&
+.vitem &$proxy_external_address$& &&&
+ &$proxy_external_port$& &&&
+ &$proxy_local_address$& &&&
+ &$proxy_local_port$& &&&
&$proxy_session$&
These variables are only available when built with Proxy Protocol
-or Socks5 support
+or SOCKS5 support.
For details see chapter &<<SECTproxyInbound>>&.
-.wen
-.new
.vitem &$prdr_requested$&
.cindex "PRDR" "variable for"
This variable is set to &"yes"& if PRDR was requested by the client for the
current message, otherwise &"no"&.
-.wen
.vitem &$prvscheck_address$&
This variable is used in conjunction with the &%prvscheck%& expansion item,
The value set for the &%qualify_recipient%& option in the configuration file,
or if not set, the value of &$qualify_domain$&.
+.vitem &$queue_name$&
+.vindex &$queue_name$&
+.cindex "named queues"
+.cindex queues named
+The name of the spool queue in use; empty for the default queue.
+
+.new
+.vitem &$r_...$&
+.vindex &$r_...$&
+.cindex router variables
+Values can be placed in these variables by the &%set%& option of a router.
+They can be given any name that starts with &$r_$&.
+The values persist for the address being handled through subsequent routers
+and the eventual transport.
+.wen
+
.vitem &$rcpt_count$&
.vindex "&$rcpt_count$&"
When a message is being received by SMTP, this variable contains the number of
option.
As well as being useful in ACLs (including the &"connect"& ACL), these variable
-could be used, for example, to make the file name for a TLS certificate depend
+could be used, for example, to make the filename for a TLS certificate depend
on which interface and/or port is being used for the incoming connection. The
values of &$received_ip_address$& and &$received_port$& are saved with any
messages that are received, thus making these variables available at delivery
If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
mechanism in the list, then this variable will be false.
+This requires that your system resolver library support EDNS0 (and that
+DNSSEC flags exist in the system headers). If the resolver silently drops
+all EDNS0 options, then this will have no effect. OpenBSD's asr resolver
+is known to currently ignore EDNS0, documented in CAVEATS of asr_run(3).
+
.vitem &$sender_host_name$&
.vindex "&$sender_host_name$&"
space removed. Following the introduction of &$smtp_command$&, this variable is
somewhat redundant, but is retained for backwards compatibility.
+.vitem &$smtp_command_history$&
+.cindex SMTP "command history"
+.vindex "&$smtp_command_history$&"
+A comma-separated list (with no whitespace) of the most-recent SMTP commands
+received, in time-order left to right. Only a limited number of commands
+are remembered.
+
.vitem &$smtp_count_at_connection_start$&
.vindex "&$smtp_count_at_connection_start$&"
This variable is set greater than zero only in processes spawned by the Exim
is compiled with the content-scanning extension. For details, see section
&<<SECTscanspamass>>&.
+.vitem &$spf_header_comment$& &&&
+ &$spf_received$& &&&
+ &$spf_result$& &&&
+ &$spf_result_guessed$& &&&
+ &$spf_smtp_comment$&
+These variables are only available if Exim is built with SPF support.
+For details see section &<<SECSPF>>&.
.vitem &$spool_directory$&
.vindex "&$spool_directory$&"
.vitem &$tls_in_ourcert$&
.vindex "&$tls_in_ourcert$&"
-.cindex certificate veriables
+.cindex certificate variables
This variable refers to the certificate presented to the peer of an
inbound connection when the message was received.
It is only useful as the argument of a
&%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
or a &%def%& condition.
+&*Note*&: Under versions of OpenSSL preceding 1.1.1,
+when a list of more than one
+file is used for &%tls_certificate%&, this variable is not reliable.
+.new
+The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
+.wen
+
.vitem &$tls_in_peercert$&
.vindex "&$tls_in_peercert$&"
This variable refers to the certificate presented by the peer of an
connection, this variable is set to the cipher suite that was negotiated, for
example DES-CBC3-SHA. In other circumstances, in particular, for message
received over unencrypted connections, the variable is empty. Testing
-&$tls_cipher$& for emptiness is one way of distinguishing between encrypted and
+&$tls_in_cipher$& for emptiness is one way of distinguishing between encrypted and
non-encrypted connections during ACL processing.
The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
becomes the same as &$tls_out_cipher$&.
+.new
+.vitem &$tls_in_cipher_std$&
+.vindex "&$tls_in_cipher_std$&"
+As above, but returning the RFC standard name for the cipher suite.
+.wen
+
.vitem &$tls_out_cipher$&
.vindex "&$tls_out_cipher$&"
This variable is
&<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
details of the &(smtp)& transport.
+,new
+.vitem &$tls_out_cipher_std$&
+.vindex "&$tls_out_cipher_std$&"
+As above, but returning the RFC standard name for the cipher suite.
+.wen
+
+.vitem &$tls_out_dane$&
+.vindex &$tls_out_dane$&
+DANE active status. See section &<<SECDANE>>&.
+
.vitem &$tls_in_ocsp$&
.vindex "&$tls_in_ocsp$&"
When a message is received from a remote client connection
SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
the transport.
+.vitem &$tls_out_tlsa_usage$&
+.vindex &$tls_out_tlsa_usage$&
+Bitfield of TLSA record types found. See section &<<SECDANE>>&.
+
.vitem &$tod_bsdinbox$&
.vindex "&$tod_bsdinbox$&"
The time of day and the date, in the format required for BSD-style mailbox
.vitem &$verify_mode$&
.vindex "&$verify_mode$&"
-While a router or transport is being run in verify mode
-or for cutthrough delivery,
+While a router or transport is being run in verify mode or for cutthrough delivery,
contains "S" for sender-verification or "R" for recipient-verification.
Otherwise, empty.
.vitem &$version_number$&
.vindex "&$version_number$&"
-The version number of Exim.
+The version number of Exim. Same as &$exim_version$&, may be overridden
+by the &%exim_version%& main config option.
.vitem &$warn_message_delay$&
.vindex "&$warn_message_delay$&"
There is also a command line option &%-pd%& (for delay) which suppresses the
initial startup, even if &%perl_at_start%& is set.
+.ilist
+.oindex "&%perl_taintmode%&"
+.cindex "Perl" "taintmode"
+To provide more security executing Perl code via the embedded Perl
+interpreter, the &%perl_taintmode%& option can be set. This enables the
+taint mode of the Perl interpreter. You are encouraged to set this
+option to a true value. To avoid breaking existing installations, it
+defaults to false.
+
.section "Calling Perl subroutines" "SECID86"
When the configuration file includes a &%perl_startup%& option you can make use
.endlist
The default list separator in both cases is a colon, but this can be changed as
-described in section &<<SECTlistconstruct>>&. When IPv6 addresses are involved,
+described in section &<<SECTlistsepchange>>&. When IPv6 addresses are involved,
it is usually best to change the separator to avoid having to double all the
colons. For example:
.code
exim.
The value of &%-oX%& is a list of items. The default colon separator can be
-changed in the usual way if required. If there are any items that do not
+changed in the usual way (&<<SECTlistsepchange>>&) if required.
+If there are any items that do not
contain dots or colons (that is, are not IP addresses), the value of
&%daemon_smtp_ports%& is replaced by the list of those items. If there are any
items that do contain dots or colons, the value of &%local_interfaces%& is
-.section "Support for the obsolete SSMTP (or SMTPS) protocol" "SECTsupobssmt"
+.section "Support for the submissions (aka SSMTP or SMTPS) protocol" "SECTsupobssmt"
+.cindex "submissions protocol"
.cindex "ssmtp protocol"
.cindex "smtps protocol"
.cindex "SMTP" "ssmtp protocol"
.cindex "SMTP" "smtps protocol"
-Exim supports the obsolete SSMTP protocol (also known as SMTPS) that was used
-before the STARTTLS command was standardized for SMTP. Some legacy clients
-still use this protocol. If the &%tls_on_connect_ports%& option is set to a
-list of port numbers or service names,
-connections to those ports must use SSMTP. The most
-common use of this option is expected to be
+Exim supports the use of TLS-on-connect, used by mail clients in the
+&"submissions"& protocol, historically also known as SMTPS or SSMTP.
+For some years, IETF Standards Track documents only blessed the
+STARTTLS-based Submission service (port 587) while common practice was to support
+the same feature set on port 465, but using TLS-on-connect.
+If your installation needs to provide service to mail clients
+(Mail User Agents, MUAs) then you should provide service on both the 587 and
+the 465 TCP ports.
+
+If the &%tls_on_connect_ports%& option is set to a list of port numbers or
+service names, connections to those ports must first establish TLS, before
+proceeding to the application layer use of the SMTP protocol.
+
+The common use of this option is expected to be
.code
tls_on_connect_ports = 465
.endd
-because 465 is the usual port number used by the legacy clients. There is also
-a command line option &%-tls-on-connect%&, which forces all ports to behave in
-this way when a daemon is started.
+per RFC 8314.
+There is also a command line option &%-tls-on-connect%&, which forces all ports
+to behave in this way when a daemon is started.
&*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
daemon to listen on those ports. You must still specify them in
.chapter "Main configuration" "CHAPmainconfig"
.scindex IIDconfima "configuration file" "main section"
.scindex IIDmaiconf "main configuration"
-The first part of the run time configuration file contains three types of item:
+The first part of the runtime configuration file contains three types of item:
.ilist
Macro definitions: These lines start with an upper case letter. See section
.section "Miscellaneous" "SECID96"
.table2
.row &%bi_command%& "to run for &%-bi%& command line option"
+.row &%debug_store%& "do extra internal checks"
.row &%disable_ipv6%& "do no IPv6 processing"
.row &%keep_malformed%& "for broken files &-- should not happen"
.row &%localhost_number%& "for unique message ids in clusters"
.row &%message_body_visible%& "how much to show in &$message_body$&"
.row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
.row &%print_topbitchars%& "top-bit characters are printing"
+.row &%spool_wireformat%& "use wire-format spool data files when possible"
.row &%timezone%& "force time zone"
.endtable
.section "Privilege controls" "SECID98"
.table2
.row &%admin_groups%& "groups that are Exim admin users"
+.row &%commandline_checks_require_admin%& "require admin for various checks"
.row &%deliver_drop_privilege%& "drop root for delivery processes"
.row &%local_from_check%& "insert &'Sender:'& if necessary"
.row &%local_from_prefix%& "for testing &'From:'& for local sender"
.row &%slow_lookup_log%& "control logging of slow DNS lookups"
.row &%syslog_duplication%& "controls duplicate log lines on syslog"
.row &%syslog_facility%& "set syslog &""facility""& field"
+.row &%syslog_pid%& "pid in syslog lines"
.row &%syslog_processname%& "set syslog &""ident""& field"
.row &%syslog_timestamp%& "timestamp syslog lines"
.row &%write_rejectlog%& "control use of message log"
.table2
.row &%perl_at_start%& "always start the interpreter"
.row &%perl_startup%& "code to obey when starting Perl"
+.row &%perl_taintmode%& "enable taint mode in Perl"
.endtable
.row &%av_scanner%& "specify virus scanner"
.row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
words""&"
+.row &%dns_cname_loops%& "follow CNAMEs returned by resolver"
.row &%dns_csa_search_limit%& "control CSA parent search depth"
.row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
.row &%header_maxsize%& "total size of message header"
See also the &'Policy controls'& section above.
.table2
-.row &%dkim_verify_signers%& "DKIM domain for which DKIM ACL is run"
+.row &%dkim_verify_hashes%& "DKIM hash methods accepted for signatures"
+.row &%dkim_verify_keytypes%& "DKIM key types accepted for signatures"
+.row &%dkim_verify_signers%& "DKIM domains for which DKIM ACL is run"
.row &%host_lookup%& "host name looked up for these hosts"
.row &%host_lookup_order%& "order of DNS and local name lookups"
.row &%recipient_unqualified_hosts%& "may send unqualified recipients"
.table2
.row &%accept_8bitmime%& "advertise 8BITMIME"
.row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
+.row &%chunking_advertise_hosts%& "advertise CHUNKING to these hosts"
.row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
.row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
.row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
.row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
+.row &%pipelining_connect_advertise_hosts%& "advertise pipelining to these hosts"
.row &%prdr_enable%& "advertise PRDR to all hosts"
.row &%smtputf8_advertise_hosts%& "advertise SMTPUTF8 to these hosts"
.row &%tls_advertise_hosts%& "advertise TLS to these hosts"
.row &%bounce_message_file%& "content of bounce"
.row &%bounce_message_text%& "content of bounce"
.row &%bounce_return_body%& "include body if returning message"
+.row &%bounce_return_linesize_limit%& "limit on returned message line length"
.row &%bounce_return_message%& "include original message in bounce"
.row &%bounce_return_size_limit%& "limit on returned message"
.row &%bounce_sender_authentication%& "send authenticated sender with bounce"
It now defaults to true.
A more detailed analysis of the issues is provided by Dan Bernstein:
.display
-&url(http://cr.yp.to/smtp/8bitmime.html)
+&url(https://cr.yp.to/smtp/8bitmime.html)
.endd
To log received 8BITMIME status use
.option acl_smtp_dkim main string&!! unset
.cindex DKIM "ACL for"
This option defines the ACL that is run for each DKIM signature
+(by default, or as specified in the dkim_verify_signers option)
of a received message.
-See chapter &<<CHAPdkim>>& for further details.
+See section &<<SECDKIMVFY>>& for further details.
.option acl_smtp_etrn main string&!! unset
.cindex "ETRN" "ACL for"
This option defines the ACL that is run when an SMTP VRFY command is
received. See chapter &<<CHAPACL>>& for further details.
+.option add_environment main "string list" empty
+.cindex "environment" "set values"
+This option allows to set individual environment variables that the
+currently linked libraries and programs in child processes use.
+See &<<SECTpipeenv>>& for the environment of &(pipe)& transports.
+
.option admin_groups main "string list&!!" unset
.cindex "admin user"
This option is expanded just once, at the start of Exim's processing. If the
.cindex "UTF-8" "in domain name"
Lots of discussion is going on about internationalized domain names. One
camp is strongly in favour of just using UTF-8 characters, and it seems
-that at least two other MTAs permit this. This option allows Exim users to
-experiment if they wish.
+that at least two other MTAs permit this.
+This option allows Exim users to experiment if they wish.
If it is set true, Exim's domain parsing function allows valid
UTF-8 multicharacters to appear in domain name components, in addition to
-letters, digits, and hyphens. However, just setting this option is not
-enough; if you want to look up these domain names in the DNS, you must also
+letters, digits, and hyphens.
+
+.new
+If Exim is built with internationalization support
+and the SMTPUTF8 ESMTP option is in use (see chapter &<<CHAPi18n>>&)
+this option can be left as default.
+.wen
+Without that,
+if you want to look up such domain names in the DNS, you must also
adjust the value of &%dns_check_names_pattern%& to match the extended form. A
suitable setting is:
.code
point at which the error was detected are returned.
.cindex "bounce message" "including original"
+.option bounce_return_linesize_limit main integer 998
+.cindex "size" "of bounce lines, limit"
+.cindex "bounce message" "line length limit"
+.cindex "limit" "bounce message line length"
+This option sets a limit in bytes on the line length of messages
+that are returned to senders due to delivery problems,
+when &%bounce_return_message%& is true.
+The default value corresponds to RFC limits.
+If the message being returned has lines longer than this value it is
+treated as if the &%bounce_return_size_limit%& (below) restriction was exceeded.
+
+The option also applies to bounces returned when an error is detected
+during reception of a message.
+In this case lines from the original are truncated.
+
+The option does not apply to messages generated by an &(autoreply)& transport.
+
+
.option bounce_return_message main boolean true
If this option is set false, none of the original message is included in
bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
See section &<<CALLaddparcall>>& for details of how this value is used.
-.option check_log_inodes main integer 0
+.option check_log_inodes main integer 100
See &%check_spool_space%& below.
-.option check_log_space main integer 0
+.option check_log_space main integer 10M
See &%check_spool_space%& below.
.oindex "&%check_rfc2047_length%&"
set false, Exim recognizes encoded words of any length.
-.option check_spool_inodes main integer 0
+.option check_spool_inodes main integer 100
See &%check_spool_space%& below.
-.option check_spool_space main integer 0
+.option check_spool_space main integer 10M
.cindex "checking disk space"
.cindex "disk space, checking"
.cindex "spool directory" "checking space"
.vindex "&$log_space$&"
.vindex "&$spool_inodes$&"
.vindex "&$spool_space$&"
-When any of these options are set, they apply to all incoming messages. If you
+When any of these options are nonzero, they apply to all incoming messages. If you
want to apply different checks to different kinds of message, you can do so by
testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
&$spool_space$& in an ACL with appropriate additional conditions.
&%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
either value is greater than zero, for example:
.code
-check_spool_space = 10M
+check_spool_space = 100M
check_spool_inodes = 100
.endd
The spool partition is the one that contains the directory defined by
&%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
The values for &%check_spool_space%& and &%check_log_space%& are held as a
-number of kilobytes. If a non-multiple of 1024 is specified, it is rounded up.
+number of kilobytes (though specified in bytes).
+If a non-multiple of 1024 is specified, it is rounded up.
For non-SMTP input and for batched SMTP input, the test is done at start-up; on
failure a message is written to stderr and Exim exits with a non-zero code, as
it obviously cannot send an error message of any kind.
+There is a slight performance penalty for these checks.
+Versions of Exim preceding 4.88 had these disabled by default;
+high-rate installations confident they will never run out of resources
+may wish to deliberately disable them.
+
+.option chunking_advertise_hosts main "host list&!!" *
+.cindex CHUNKING advertisement
+.cindex "RFC 3030" "CHUNKING"
+The CHUNKING extension (RFC3030) will be advertised in the EHLO message to
+these hosts.
+Hosts may use the BDAT command as an alternate to DATA.
+
+.option commandline_checks_require_admin main boolean &`false`&
+.cindex "restricting access to features"
+This option restricts various basic checking features to require an
+administrative user.
+This affects most of the &%-b*%& options, such as &%-be%&.
+
+.option debug_store main boolean &`false`&
+.cindex debugging "memory corruption"
+.cindex memory debugging
+This option, when true, enables extra checking in Exim's internal memory
+management. For use when a memory corruption issue is being investigated,
+it should normally be left as default.
+
.option daemon_smtp_ports main string &`smtp`&
.cindex "port" "for daemon"
.cindex "TCP/IP" "setting listening ports"
.option delay_warning main "time list" 24h
.cindex "warning of delay"
.cindex "delay warning, specifying"
+.cindex "queue" "delay warning"
When a message is delayed, Exim sends a warning message to the sender at
intervals specified by this option. The data is a colon-separated list of times
after which to send warning messages. If the value of the option is an empty
string or a zero time, no warnings are sent. Up to 10 times may be given. If a
-message has been on the queue for longer than the last time, the last interval
+message has been in the queue for longer than the last time, the last interval
between the times is used to compute subsequent warning times. For example,
with
.code
to handle IPv6 literal addresses.
+.new
+.option dkim_verify_hashes main "string list" "sha256 : sha512 : sha1"
+.cindex DKIM "selecting signature algorithms"
+This option gives a list of hash types which are acceptable in signatures,
+and an order of processing.
+Signatures with algorithms not in the list will be ignored.
+
+Note that the presence of sha1 violates RFC 8301.
+Signatures using the rsa-sha1 are however (as of writing) still common.
+The default inclusion of sha1 may be dropped in a future release.
+
+.option dkim_verify_keytypes main "string list" "ed25519 : rsa"
+This option gives a list of key types which are acceptable in signatures,
+and an order of processing.
+Signatures with algorithms not in the list will be ignored.
+
+.option dkim_verify_minimal main boolean false
+If set to true, verification of signatures will terminate after the
+first success.
+.wen
+
.option dkim_verify_signers main "domain list&!!" $dkim_signers
.cindex DKIM "controlling calls to the ACL"
This option gives a list of DKIM domains for which the DKIM ACL is run.
It is expanded after the message is received; by default it runs
the ACL once for each signature in the message.
-See chapter &<<CHAPdkim>>&.
+See section &<<SECDKIMVFY>>&.
.option dns_again_means_nonexist main "domain list&!!" unset
reversed and looked up in the reverse DNS, as described in more detail in
section &<<SECTverifyCSA>>&.
+.option dns_cname_loops main integer 1
+.cindex DNS "CNAME following"
+This option controls the following of CNAME chains, needed if the resolver does
+not do it internally.
+As of 2018 most should, and the default can be left.
+If you have an ancient one, a value of 10 is likely needed.
+
+The default value of one CNAME-follow is needed
+thanks to the observed return for an MX request,
+given no MX presence but a CNAME to an A, of the CNAME.
+
.option dns_dnssec_ok main integer -1
.cindex "DNS" "resolver options"
.option dns_ipv4_lookup main "domain list&!!" unset
.cindex "IPv6" "DNS lookup for AAAA records"
.cindex "DNS" "IPv6 lookup for AAAA records"
+.cindex DNS "IPv6 disabling"
When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
looks for IPv6 address records (AAAA records) as well as IPv4 address records
(A records) when trying to find IP addresses for hosts, unless the host's
This is a fudge to help with name servers that give big delays or otherwise do
not work for the AAAA record type. In due course, when the world's name
servers have all been upgraded, there should be no need for this option.
+.new
+Note that all lookups, including those done for verification, are affected;
+this will result in verify failure for IPv6 connections or ones using names
+only valid for IPv6 addresses.
+.wen
.option dns_retrans main time 0s
.option dns_use_edns0 main integer -1
.cindex "DNS" "resolver options"
.cindex "DNS" "EDNS0"
+.cindex "DNS" "OpenBSD
If this option is set to a non-negative number then Exim will initialise the
DNS resolver library to either use or not use EDNS0 extensions, overriding
the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
If the resolver library does not support EDNS0 then this option has no effect.
+OpenBSD's asr resolver routines are known to ignore the EDNS0 option; this
+means that DNSSEC will not work with Exim on that platform either, unless Exim
+is linked against an alternative DNS client library.
+
.option drop_cr main boolean false
This is an obsolete option that is now a no-op. It used to affect the way Exim
not used.
-.new
.option event_action main string&!! unset
.cindex events
This option declares a string to be expanded for Exim's events mechanism.
-For details see &<<CHAPevents>>&.
-.wen
+For details see chapter &<<CHAPevents>>&.
.option exim_group main string "compile-time configured"
used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
+.option exim_version main string "current version"
+.cindex "Exim version"
+.cindex customizing "version number"
+.cindex "version number of Exim" override
+This option allows to override the &$version_number$&/&$exim_version$& Exim reports in
+various places. Use with care, this may fool stupid security scanners.
+
+
.option extra_local_interfaces main "string list" unset
This option defines network interfaces that are to be considered local when
routing, but which are not used for listening by the daemon. See section
implementations of TLS.
-option gnutls_allow_auto_pkcs11 main boolean unset
+.option gnutls_allow_auto_pkcs11 main boolean unset
This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
See
-&url(http://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
+&url(https://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
for documentation.
.option hold_domains main "domain list&!!" unset
.cindex "domain" "delaying delivery"
.cindex "delivery" "delaying certain domains"
-This option allows mail for particular domains to be held on the queue
+This option allows mail for particular domains to be held in the queue
manually. The option is overridden if a message delivery is forced with the
&%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
-.new
.option hosts_proxy main "host list&!!" unset
.cindex proxy "proxy protocol"
This option enables use of Proxy Protocol proxies for incoming
-connections. For details see &<<SECTproxyInbound>>&.
-.wen
+connections. For details see section &<<SECTproxyInbound>>&.
.option hosts_treat_as_local main "domain list&!!" unset
After a permanent delivery failure, bounce messages are frozen,
because there is no sender to whom they can be returned. When a frozen bounce
-message has been on the queue for more than the given time, it is unfrozen at
+message has been in the queue for more than the given time, it is unfrozen at
the next queue run, and a further delivery is attempted. If delivery fails
again, the bounce message is discarded. This makes it possible to keep failed
bounce messages around for a shorter time than the normal maximum retry time
.option ignore_fromline_local main boolean false
See &%ignore_fromline_hosts%& above.
+.option keep_environment main "string list" unset
+.cindex "environment" "values from"
+This option contains a string list of environment variables to keep.
+You have to trust these variables or you have to be sure that
+these variables do not impose any security risk. Keep in mind that
+during the startup phase Exim is running with an effective UID 0 in most
+installations. As the default value is an empty list, the default
+environment for using libraries, running embedded Perl code, or running
+external binaries is empty, and does not not even contain PATH or HOME.
+
+Actually the list is interpreted as a list of patterns
+(&<<SECTlistexpand>>&), except that it is not expanded first.
+
+WARNING: Macro substitution is still done first, so having a macro
+FOO and having FOO_HOME in your &%keep_environment%& option may have
+unexpected results. You may work around this using a regular expression
+that does not match the macro name: ^[F]OO_HOME$.
+
+Current versions of Exim issue a warning during startup if you do not mention
+&%keep_environment%& in your runtime configuration file and if your
+current environment is not empty. Future versions may not issue that warning
+anymore.
+
+See the &%add_environment%& main config option for a way to set
+environment variables to a fixed value. The environment for &(pipe)&
+transports is handled separately, see section &<<SECTpipeenv>>& for
+details.
+
.option keep_malformed main time 4d
This option specifies the length of time to keep messages whose spool files
of SSL-on-connect.
In the event of failure to negotiate TLS, the action taken is controlled
by &%ldap_require_cert%&.
+This option is ignored for &`ldapi`& connections.
.option ldap_version main integer unset
&'Sender:'& header lines supplied by untrusted users, you must also set
&%local_sender_retain%& to be true.
+.cindex "envelope from"
.cindex "envelope sender"
These options affect only the header lines in the message. The envelope sender
is still forced to be the login id at the qualify domain unless
This option sets the path which is used to determine the names of Exim's log
files, or indicates that logging is to be to syslog, or both. It is expanded
when Exim is entered, so it can, for example, contain a reference to the host
-name. If no specific path is set for the log files at compile or run time,
-or if the option is unset at run time (i.e. &`log_file_path = `&)
+name. If no specific path is set for the log files at compile or runtime,
+or if the option is unset at runtime (i.e. &`log_file_path = `&)
they are written in a sub-directory called &_log_& in Exim's spool directory.
+.new
+A path must start with a slash.
+To send to syslog, use the word &"syslog"&.
+.wen
Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
used. If this string is fixed at your installation (contains no expansion
transport driver.
-.option openssl_options main "string list" "+no_sslv2 +single_dh_use"
+.option openssl_options main "string list" "+no_sslv2 +no_sslv3 +single_dh_use +no_ticket"
.cindex "OpenSSL "compatibility options"
This option allows an administrator to adjust the SSL options applied
by OpenSSL to connections. It is given as a space-separated list of items,
.option perl_at_start main boolean false
+.cindex "Perl"
This option is available only when Exim is built with an embedded Perl
interpreter. See chapter &<<CHAPperl>>& for details of its use.
.option perl_startup main string unset
+.cindex "Perl"
This option is available only when Exim is built with an embedded Perl
interpreter. See chapter &<<CHAPperl>>& for details of its use.
+.option perl_startup main boolean false
+.cindex "Perl"
+This Option enables the taint mode of the embedded Perl interpreter.
+
.option pgsql_servers main "string list" unset
.cindex "PostgreSQL lookup type" "server list"
that clients will use it; &"out of order"& commands that are &"expected"& do
not count as protocol errors (see &%smtp_max_synprot_errors%&).
+.new
+.option pipelining_connect_advertise_hosts main "host list&!!" *
+.cindex "pipelining" "early connection"
+.cindex "pipelining" PIPE_CONNECT
+If Exim is built with the SUPPORT_PIPE_CONNECT build option
+this option controls which hosts the facility is advertised to
+and from which pipeline early-connection (before MAIL) SMTP
+commands are acceptable.
+When used, the pipelining saves on roundtrip times.
+
+See also the &%hosts_pipe_connect%& smtp transport option.
+
+Currently the option name &"X_PIPE_CONNECT"& is used.
+.wen
+
.option prdr_enable main boolean false
.cindex "PRDR" "enabling on server"
.option prod_requires_admin main boolean true
+.cindex "restricting access to features"
.oindex "&%-M%&"
.oindex "&%-R%&"
.oindex "&%-q%&"
The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
admin user unless &%prod_requires_admin%& is set false. See also
-&%queue_list_requires_admin%&.
+&%queue_list_requires_admin%& and &%commandline_checks_require_admin%&.
.option qualify_domain main string "see below"
.option queue_list_requires_admin main boolean true
+.cindex "restricting access to features"
.oindex "&%-bp%&"
The &%-bp%& command-line option, which lists the messages that are on the
queue, requires the caller to be an admin user unless
-&%queue_list_requires_admin%& is set false. See also &%prod_requires_admin%&.
+&%queue_list_requires_admin%& is set false.
+See also &%prod_requires_admin%& and &%commandline_checks_require_admin%&.
.option queue_only main boolean false
.cindex "queueing incoming messages"
.cindex "message" "queueing unconditionally"
If &%queue_only%& is set, a delivery process is not automatically started
-whenever a message is received. Instead, the message waits on the queue for the
+whenever a message is received. Instead, the message waits in the queue for the
next queue run. Even if &%queue_only%& is false, incoming messages may not get
delivered immediately when certain conditions (such as heavy load) occur.
-.option queue_run_max main integer 5
+.option queue_run_max main integer&!! 5
.cindex "queue runner" "maximum number of"
This controls the maximum number of queue runner processes that an Exim daemon
can run simultaneously. This does not mean that it starts them all at once,
run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
the daemon's command line.
+.cindex queues named
+.cindex "named queues"
+To set limits for different named queues use
+an expansion depending on the &$queue_name$& variable.
+
.option queue_smtp_domains main "domain list&!!" unset
.cindex "queueing incoming messages"
.cindex "message" "queueing remote deliveries"
received, routing is performed, and local deliveries take place.
However, if any SMTP deliveries are required for domains that match
&%queue_smtp_domains%&, they are not immediately delivered, but instead the
-message waits on the queue for the next queue run. Since routing of the message
+message waits in the queue for the next queue run. Since routing of the message
has taken place, Exim knows to which remote hosts it must be delivered, and so
when the queue run happens, multiple messages for the same host are delivered
over a single SMTP connection. The &%-odqs%& command line option causes all
.cindex "timeout" "for non-SMTP input"
This option sets the timeout for accepting a non-SMTP message, that is, the
maximum time that Exim waits when reading a message on the standard input. If
-the value is zero, it will wait for ever. This setting is overridden by the
+the value is zero, it will wait forever. This setting is overridden by the
&%-or%& command line option. The timeout for incoming SMTP messages is
controlled by &%smtp_receive_timeout%&.
used. If the expansion yields an empty string, no &'Received:'& header line is
added to the message. Otherwise, the string should start with the text
&"Received:"& and conform to the RFC 2822 specification for &'Received:'&
-header lines. The default setting is:
+header lines.
+.new
+The default setting is:
.code
received_header_text = Received: \
${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
- {${if def:sender_ident \
- {from ${quote_local_part:$sender_ident} }}\
- ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
+ {${if def:sender_ident \
+ {from ${quote_local_part:$sender_ident} }}\
+ ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
by $primary_hostname \
- ${if def:received_protocol {with $received_protocol}} \
- ${if def:tls_in_cipher {($tls_in_cipher)\n\t}}\
+ ${if def:received_protocol {with $received_protocol }}\
+ ${if def:tls_in_cipher_std { tls $tls_in_cipher_std\n\t}}\
(Exim $version_number)\n\t\
${if def:sender_address \
{(envelope-from <$sender_address>)\n\t}}\
id $message_exim_id\
${if def:received_for {\n\tfor $received_for}}
.endd
+.wen
The reference to the TLS cipher is omitted when Exim is built without TLS
support. The use of conditional expansions ensures that this works for both
&%sender_unqualified_hosts%&, or if the message was submitted locally (not
using TCP/IP), and the &%-bnq%& option was not set.
+.option add_environment main "string list" empty
+.cindex "environment"
+This option allows to add individual environment variables that the
+currently linked libraries and programs in child processes use. The
+default list is empty.
+
.option slow_lookup_log main integer 0
.cindex "logging" "slow lookups"
.cindex "message" "queueing by SMTP connection count"
If the number of simultaneous incoming SMTP connections being handled via the
listening daemon exceeds this value, messages received by SMTP are just placed
-on the queue; no delivery processes are started automatically. The count is
+in the queue; no delivery processes are started automatically. The count is
fixed at the start of an SMTP connection. It cannot be updated in the
subprocess that receives messages, and so the queueing or not queueing applies
to all messages received in the same connection.
automatically when receiving messages via SMTP, whether via the daemon or by
the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
and the number of messages received in a single SMTP session exceeds this
-number, subsequent messages are placed on the queue, but no delivery processes
+number, subsequent messages are placed in the queue, but no delivery processes
are started. This helps to limit the number of Exim processes when a server
restarts after downtime and there is a lot of mail waiting for it on other
systems. On large systems, the default should probably be increased, and on
.endd
-.new
.option smtputf8_advertise_hosts main "host list&!!" *
.cindex "SMTPUTF8" "advertising"
When Exim is built with support for internationalised mail names,
-the availability therof is advertised in
+the availability thereof is advertised in
response to EHLO only to those client hosts that match this option. See
chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
-.wen
-.option spamd_address main string "see below"
+.option spamd_address main string "127.0.0.1 783"
This option is available when Exim is compiled with the content-scanning
extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
-The default value is
-.code
-127.0.0.1 783
-.endd
See section &<<SECTscanspamass>>& for more details.
+.option spf_guess main string "v=spf1 a/24 mx/24 ptr ?all"
+This option is available when Exim is compiled with SPF support.
+See section &<<SECSPF>>& for more details.
+
+
+
.option split_spool_directory main boolean false
.cindex "multiple spool directories"
.cindex "spool directory" "split"
When &%split_spool_directory%& is set, the behaviour of queue runner processes
changes. Instead of creating a list of all messages in the queue, and then
-trying to deliver each one in turn, it constructs a list of those in one
+trying to deliver each one, in turn, it constructs a list of those in one
sub-directory and tries to deliver them, before moving on to the next
sub-directory. The sub-directories are processed in a random order. This
spreads out the scanning of the input directories, and uses less memory. It is
-particularly beneficial when there are lots of messages on the queue. However,
+particularly beneficial when there are lots of messages in the queue. However,
if &%queue_run_in_order%& is set, none of this new processing happens. The
entire queue has to be scanned and sorted before any deliveries can start.
By using this option to override the compiled-in path, it is possible to run
tests of Exim without using the standard spool.
+.option spool_wireformat main boolean false
+.cindex "spool directory" "file formats"
+If this option is set, Exim may for some messages use an alternative format
+for data-files in the spool which matches the wire format.
+Doing this permits more efficient message reception and transmission.
+Currently it is only done for messages received using the ESMTP CHUNKING
+option.
+
+The following variables will not have useful values:
+.code
+$max_received_linelength
+$body_linecount
+$body_zerocount
+.endd
+
+Users of the local_scan() API (see &<<CHAPlocalscan>>&),
+and any external programs which are passed a reference to a message data file
+(except via the &"regex"&, &"malware"& or &"spam"&) ACL conditions)
+will need to be aware of the different formats potentially available.
+
+Using any of the ACL conditions noted will negate the reception benefit
+(as a Unix-mbox-format file is constructed for them).
+The transmission benefit is maintained.
+
.option sqlite_lock_timeout main time 5s
.cindex "sqlite lookup type" "lock timeout"
This option controls the timeout that the &(sqlite)& lookup uses when trying to
details of Exim's logging.
+.option syslog_pid main boolean true
+.cindex "syslog" "pid"
+If &%syslog_pid%& is set false, the PID on Exim's log lines are
+omitted when these lines are sent to syslog. (Syslog normally prefixes
+the log lines with the PID of the logging process automatically.) You need
+to enable the &`+pid`& log selector item, if you want Exim to write it's PID
+into the logs.) See chapter &<<CHAPlog>>& for details of Exim's logging.
+
+
.option syslog_processname main string &`exim`&
.cindex "syslog" "process name; setting"
appropriate &%system_filter_..._transport%& option(s) must be set, to define
which transports are to be used. Details of this facility are given in chapter
&<<CHAPsystemfilter>>&.
+A forced expansion failure results in no filter operation.
.option system_filter_directory_transport main string&!! unset
.cindex "frozen messages" "timing out"
.cindex "timeout" "frozen messages"
If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
-message of any kind that has been on the queue for longer than the given time
+message of any kind that has been in the queue for longer than the given time
is automatically cancelled at the next queue run. If the frozen message is a
bounce message, it is just discarded; otherwise, a bounce is sent to the
sender, in a similar manner to cancellation by the &%-Mg%& command line option.
frozen message, see &%ignore_bounce_errors_after%&.
&*Note:*& the default value of zero means no timeouts; with this setting,
-frozen messages remain on the queue forever (except for any frozen bounce
+frozen messages remain in the queue forever (except for any frozen bounce
messages that are released by &%ignore_bounce_errors_after%&).
.option timezone main string unset
.cindex "timezone, setting"
+.cindex "environment" "values from"
The value of &%timezone%& is used to set the environment variable TZ while
running Exim (if it is different on entry). This ensures that all timestamps
created by Exim are in the required timezone. If you want all your timestamps
unfortunately not all, operating systems.
-.new
.option tls_advertise_hosts main "host list&!!" *
-.wen
.cindex "TLS" "advertising"
.cindex "encryption" "on SMTP connection"
.cindex "SMTP" "encrypted connection"
of the STARTTLS command to set up an encrypted session is advertised in
response to EHLO only to those client hosts that match this option. See
chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
-.new
Note that the default value requires that a certificate be supplied
-using the &%tls_certificate%& option. If no certificate is available then
-the &%tls_advertise_hosts%& option should be set empty.
-.wen
+using the &%tls_certificate%& option. If TLS support for incoming connections
+is not required the &%tls_advertise_hosts%& option should be set empty.
-.option tls_certificate main string&!! unset
+.option tls_certificate main string list&!! unset
.cindex "TLS" "server certificate; location of"
.cindex "certificate" "server, location of"
-The value of this option is expanded, and must then be the absolute path to a
-file which contains the server's certificates. The server's private key is also
+The value of this option is expanded, and must then be a list of absolute paths to
+files which contain the server's certificates (in PEM format).
+Commonly only one file is needed.
+The server's private key is also
assumed to be in this file if &%tls_privatekey%& is unset. See chapter
&<<CHAPTLS>>& for further details.
use when sending messages as a client, you must set the &%tls_certificate%&
option in the relevant &(smtp)& transport.
+&*Note*&: If you use filenames based on IP addresses, change the list
+separator in the usual way (&<<SECTlistsepchange>>&) to avoid confusion under IPv6.
+
+&*Note*&: Under versions of OpenSSL preceding 1.1.1,
+when a list of more than one
+file is used, the &$tls_in_ourcert$& variable is unreliable.
+.new
+The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
+.wen
+
If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
if the OpenSSL build supports TLS extensions and the TLS client sends the
Server Name Indication extension, then this option and others documented in
&<<SECTtlssni>>& will be re-expanded.
+If this option is unset or empty a fresh self-signed certificate will be
+generated for every connection.
+
.option tls_crl main string&!! unset
.cindex "TLS" "server certificate revocation list"
.cindex "certificate" "revocation list for server"
This option specifies a certificate revocation list. The expanded value must
-be the name of a file that contains a CRL in PEM format.
+be the name of a file that contains CRLs in PEM format.
+
+Under OpenSSL the option can specify a directory with CRL files.
+
+&*Note:*& Under OpenSSL the option must, if given, supply a CRL
+for each signing element of the certificate chain (i.e. all but the leaf).
+For the file variant this can be multiple PEM blocks in the one file.
See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
The value of this option is expanded and indicates the source of DH parameters
to be used by Exim.
-If it is a filename starting with a &`/`&, then it names a file from which DH
+.new
+This option is ignored for GnuTLS version 3.6.0 and later.
+The library manages parameter negotiation internally.
+.wen
+
+&*Note: The Exim Maintainers strongly recommend,
+for other TLS library versions,
+using a filename with site-generated
+local DH parameters*&, which has been supported across all versions of Exim. The
+other specific constants available are a fallback so that even when
+"unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
+
+If &%tls_dhparam%& is a filename starting with a &`/`&,
+then it names a file from which DH
parameters should be loaded. If the file exists, it should hold a PEM-encoded
PKCS#3 representation of the DH prime. If the file does not exist, for
OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
See section &<<SECTgnutlsparam>>& for further details.
If Exim is using OpenSSL and this option is empty or unset, then Exim will load
-a default DH prime; the default is the 2048 bit prime described in section
+a default DH prime; the default is Exim-specific but lacks verifiable provenance.
+
+In older versions of Exim the default was the 2048 bit prime described in section
2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
in IKE is assigned number 23.
Otherwise, the option must expand to the name used by Exim for any of a number
-of DH primes specified in RFC 2409, RFC 3526 and RFC 5114. As names, Exim uses
-"ike" followed by the number used by IKE, of "default" which corresponds to
-"ike23".
+of DH primes specified in RFC 2409, RFC 3526, RFC 5114, RFC 7919, or from other
+sources. As names, Exim uses a standard specified name, else "ike" followed by
+the number used by IKE, or "default" which corresponds to
+&`exim.dev.20160529.3`&.
-The available primes are:
+The available standard primes are:
+&`ffdhe2048`&, &`ffdhe3072`&, &`ffdhe4096`&, &`ffdhe6144`&, &`ffdhe8192`&,
&`ike1`&, &`ike2`&, &`ike5`&,
&`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
-&`ike22`&, &`ike23`& (aka &`default`&) and &`ike24`&.
+&`ike22`&, &`ike23`& and &`ike24`&.
+
+The available additional primes are:
+&`exim.dev.20160529.1`&, &`exim.dev.20160529.2`& and &`exim.dev.20160529.3`&.
Some of these will be too small to be accepted by clients.
Some may be too large to be accepted by clients.
+The open cryptographic community has suspicions about the integrity of some
+of the later IKE values, which led into RFC7919 providing new fixed constants
+(the "ffdhe" identifiers).
+
+At this point, all of the "ike" values should be considered obsolete;
+they're still in Exim to avoid breaking unusual configurations, but are
+candidates for removal the next time we have backwards-incompatible changes.
The TLS protocol does not negotiate an acceptable size for this; clients tend
to hard-drop connections if what is offered by the server is unacceptable,
acceptable bound from 1024 to 2048.
-.option tls_eccurve main string&!! prime256v1
+.option tls_eccurve main string&!! &`auto`&
.cindex TLS "EC cryptography"
-If built with a recent-enough version of OpenSSL,
-this option selects a EC curve for use by Exim.
+This option selects a EC curve for use by Exim when used with OpenSSL.
+It has no effect when Exim is used with GnuTLS.
-Curve names of the form &'prime256v1'& are accepted.
-For even more-recent library versions, names of the form &'P-512'&
-are also accepted, plus the special value &'auto'&
-which tell the library to choose.
+After expansion it must contain a valid EC curve parameter, such as
+&`prime256v1`&, &`secp384r1`&, or &`P-512`&. Consult your OpenSSL manual
+for valid selections.
-If the option is set to an empty string, no EC curves will be enabled.
+For OpenSSL versions before (and not including) 1.0.2, the string
+&`auto`& selects &`prime256v1`&. For more recent OpenSSL versions
+&`auto`& tells the library to choose.
+
+If the option expands to an empty string, no EC curves will be enabled.
.option tls_ocsp_file main string&!! unset
status proof for the server's certificate, as obtained from the
Certificate Authority.
-.new
Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
+.new
+The macro "_HAVE_TLS_OCSP" will be defined for those versions.
.wen
+.new
+For OpenSSL 1.1.0 or later, and
+.wen
+for GnuTLS 3.5.6 or later the expanded value of this option can be a list
+of files, to match a list given for the &%tls_certificate%& option.
+The ordering of the two lists must match.
+.new
+The macro "_HAVE_TLS_OCSP_LIST" will be defined for those versions.
+.wen
+
+.new
+The file(s) should be in DER format,
+except for GnuTLS 3.6.3 or later
+or for OpenSSL,
+when an optional filetype prefix can be used.
+The prefix must be one of "DER" or "PEM", followed by
+a single space. If one is used it sets the format for subsequent
+files in the list; the initial format is DER.
+If multiple proofs are wanted, for multiple chain elements
+(this only works under TLS1.3)
+they must be coded as a combined OCSP response.
+
+Although GnuTLS will accept PEM files with multiple separate
+PEM blobs (ie. separate OCSP responses), it sends them in the
+TLS Certificate record interleaved with the certificates of the chain;
+although a GnuTLS client is happy with that, an OpenSSL client is not.
+.wen
.option tls_on_connect_ports main "string list" unset
.cindex SSMTP
.cindex SMTPS
This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
-operate the obsolete SSMTP (SMTPS) protocol, where a TLS session is immediately
+operate the SSMTP (SMTPS) protocol, where a TLS session is immediately
set up without waiting for the client to issue a STARTTLS command. For
further details, see section &<<SECTsupobssmt>>&.
-.option tls_privatekey main string&!! unset
+.option tls_privatekey main string list&!! unset
.cindex "TLS" "server private key; location of"
-The value of this option is expanded, and must then be the absolute path to a
-file which contains the server's private key. If this option is unset, or if
+The value of this option is expanded, and must then be a list of absolute paths to
+files which contains the server's private keys.
+If this option is unset, or if
the expansion is forced to fail, or the result is an empty string, the private
key is assumed to be in the same file as the server's certificates. See chapter
&<<CHAPTLS>>& for further details.
.cindex "sender" "setting by untrusted user"
.cindex "untrusted user setting sender"
.cindex "user" "untrusted setting sender"
+.cindex "envelope from"
.cindex "envelope sender"
When an untrusted user submits a message to Exim using the standard input, Exim
normally creates an envelope sender address from the user's login and the
.cindex "customizing" "warning message"
This option defines a template file containing paragraphs of text to be used
for constructing the warning message which is sent by Exim when a message has
-been on the queue for a specified amount of time, as specified by
+been in the queue for a specified amount of time, as specified by
&%delay_warning%&. Details of the file's contents are given in chapter
&<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
This makes the configuration file less messy, and also reduces the number of
lookups (though Exim does cache lookups).
+.new
+See also the &%set%& option below.
+.wen
+
.vindex "&$sender_address_data$&"
.vindex "&$address_data$&"
The &%address_data%& facility is also useful as a means of passing information
unless you really, really know what you are doing. See also the generic
transport option of the same name.
-.option dnssec_request_domains routers "domain list&!!" unset
+.option dnssec_request_domains routers "domain list&!!" *
.cindex "MX record" "security"
.cindex "DNSSEC" "MX lookup"
.cindex "security" "MX lookup"
.cindex "DNSSEC" "MX lookup"
.cindex "security" "MX lookup"
.cindex "DNS" "DNSSEC"
-DNS lookups for domains matching &%dnssec_request_domains%& will be done with
+DNS lookups for domains matching &%dnssec_require_domains%& will be done with
the dnssec request bit set. Any returns not having the Authenticated Data bit
(AD bit) set will be ignored and logged as a host-lookup failure.
This applies to all of the SRV, MX, AAAA, A lookup sequence.
.option errors_to routers string&!! unset
+.cindex "envelope from"
.cindex "envelope sender"
.cindex "router" "changing address for errors"
If a router successfully handles an address, it may assign the address to a
.cindex "fallback" "hosts specified on router"
String expansion is not applied to this option. The argument must be a
colon-separated list of host names or IP addresses. The list separator can be
-changed (see section &<<SECTlistconstruct>>&), and a port can be specified with
+changed (see section &<<SECTlistsepchange>>&), and a port can be specified with
each name or address. In fact, the format of each item is exactly the same as
defined for the list of hosts in a &(manualroute)& router (see section
&<<SECTformatonehostitem>>&).
.cindex "header lines" "adding"
.cindex "router" "adding header lines"
This option specifies a list of text headers,
-newline-separated (by default, changeable in the usual way),
+newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
that is associated with any addresses that are accepted by the router.
Each item is separately expanded, at routing time. However, this
option has no effect when an address is just being verified. The way in which
.cindex "header lines" "removing"
.cindex "router" "removing header lines"
This option specifies a list of text headers,
-colon-separated (by default, changeable in the usual way),
+colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
that is associated with any addresses that are accepted by the router.
Each item is separately expanded, at routing time. However, this
option has no effect when an address is just being verified. The way in which
.option local_part_prefix routers&!? "string list" unset
+.cindex affix "router precondition"
.cindex "router" "prefix for local part"
.cindex "prefix" "for local part, used in router"
If this option is set, the router is skipped unless the local part starts with
through the &%require_files%& list, expanding each item separately.
Because the list is split before expansion, any colons in expansion items must
-be doubled, or the facility for using a different list separator must be used.
+be doubled, or the facility for using a different list separator must be used
+(&<<SECTlistsepchange>>&).
If any expansion is forced to fail, the item is ignored. Other expansion
failures cause routing of the address to be deferred.
these options are all expanded, you can use the &%exists%& expansion condition
to make such tests. The &%require_files%& option is intended for checking files
that the router may be going to use internally, or which are needed by a
-transport (for example &_.procmailrc_&).
+transport (e.g., &_.procmailrc_&).
During delivery, the &[stat()]& function is run as root, but there is a
facility for some checking of the accessibility of a file by another user.
be caused by a configuration error, and routing is deferred because the
existence or non-existence of the file cannot be determined. However, in some
circumstances it may be desirable to treat this condition as if the file did
-not exist. If the file name (or the exclamation mark that precedes the file
-name for non-existence) is preceded by a plus sign, the EACCES error is treated
+not exist. If the filename (or the exclamation mark that precedes the filename
+for non-existence) is preceded by a plus sign, the EACCES error is treated
as if the file did not exist. For example:
.code
require_files = +/some/file
This option controls whether the local part is used to form the key for retry
hints for addresses that suffer temporary errors while being handled by this
-router. The default value is true for any router that has &%check_local_user%&
+.new
+router. The default value is true for any router that has any of
+&%check_local_user%&,
+&%local_parts%&,
+&%condition%&,
+&%local_part_prefix%&,
+&%local_part_suffix%&,
+&%senders%& or
+&%require_files%&
+.wen
set, and false otherwise. Note that this option does not apply to hints keys
for transport delays; they are controlled by a generic transport option of the
same name.
+Failing to set this option when it is needed
+(because a remote router handles only some of the local-parts for a domain)
+can result in incorrect error messages being generated.
+
The setting of &%retry_use_local_part%& applies only to the router on which it
appears. If the router generates child addresses, they are routed
independently; this setting does not become attached to them.
matters.
+.new
+.option set routers "string list" unset
+.cindex router variables
+This option may be used multiple times on a router;
+because of this the list aspect is mostly irrelevant.
+The list separator is a semicolon but can be changed in the
+usual way.
+
+Each list-element given must be of the form $"name = value"$
+and the names used must start with the string &"r_"&.
+Values containing a list-separator should have them doubled.
+When a router runs, the strings are evaluated in order,
+to create variables which are added to the set associated with
+the address.
+The variable is set with the expansion of the value.
+The variables can be used by the router options
+(not including any preconditions)
+and by the transport.
+Later definitions of a given named variable will override former ones.
+Varible use is via the usual &$r_...$& syntax.
+
+This is similar to the &%address_data%& option, except that
+many independent variables can be used, with choice of naming.
+.wen
+
+
.option translate_ip_address routers string&!! unset
.cindex "IP address" "translating"
.cindex "packet radio"
MX records of equal priority are sorted by Exim into a random order. Exim then
looks for address records for the host names obtained from MX or SRV records.
When a host has more than one IP address, they are sorted into a random order,
-except that IPv6 addresses are always sorted before IPv4 addresses. If all the
+except that IPv6 addresses are sorted before IPv4 addresses. If all the
IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
generic option, the router declines.
also being queued.
+.option ipv4_only "string&!!" unset
+.cindex IPv6 disabling
+.cindex DNS "IPv6 disabling"
+The string is expanded, and if the result is anything but a forced failure,
+or an empty string, or one of the strings “0” or “no” or “false”
+(checked without regard to the case of the letters),
+only A records are used.
+
+.option ipv4_prefer "string&!!" unset
+.cindex IPv4 preference
+.cindex DNS "IPv4 preference"
+The string is expanded, and if the result is anything but a forced failure,
+or an empty string, or one of the strings “0” or “no” or “false”
+(checked without regard to the case of the letters),
+A records are sorted before AAAA records (inverting the default).
+
.option mx_domains dnslookup "domain list&!!" unset
.cindex "MX record" "required to exist"
.cindex "SRV record" "required to exist"
A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
always separately expanded before use. If the expansion fails, the router
declines. The result of the expansion must be a colon-separated list of names
-and/or IP addresses, optionally also including ports. The format of each item
+and/or IP addresses, optionally also including ports.
+If the list is written with spaces, it must be protected with quotes.
+The format of each item
in the list is described in the next section. The list separator can be changed
-as described in section &<<SECTlistconstruct>>&.
+as described in section &<<SECTlistsepchange>>&.
If the list of hosts was obtained from a &%route_list%& item, the following
variables are set during its expansion:
.section "How the options are used" "SECThowoptused"
-The options are a sequence of words; in practice no more than three are ever
-present. One of the words can be the name of a transport; this overrides the
+The options are a sequence of words, space-separated.
+One of the words can be the name of a transport; this overrides the
&%transport%& option on the router for this particular routing rule only. The
other words (if present) control randomization of the list of hosts on a
per-rule basis, and how the IP addresses of the hosts are to be found when
&%bydns%&: look up address records for the hosts directly in the DNS; fail if
no address records are found. If there is a temporary DNS error (such as a
timeout), delivery is deferred.
+.next
+&%ipv4_only%&: in direct DNS lookups, look up only A records.
+.next
+&%ipv4_prefer%&: in direct DNS lookups, sort A records before AAAA records.
.endlist
For example:
lookup first. Only if that gives a definite &"no such host"& is the local
function called.
+&*Compatibility*&: From Exim 4.85 until fixed for 4.90, there was an
+inadvertent constraint that a transport name as an option had to be the last
+option specified.
+
If no IP address for a host can be found, what happens is controlled by the
described in the next section.
.endlist
-When a message is redirected to a file (a &"mail folder"&), the file name given
+When a message is redirected to a file (a &"mail folder"&), the filename given
in a non-filter redirection list must always be an absolute path. A filter may
generate a relative path &-- how this is handled depends on the transport's
configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
.cindex "address redirection" "non-filter list items"
When the redirection data is not an Exim or Sieve filter, for example, if it
comes from a conventional alias or forward file, it consists of a list of
-addresses, file names, pipe commands, or certain special items (see section
+addresses, filenames, pipe commands, or certain special items (see section
&<<SECTspecitredli>>& below). The special items can be individually enabled or
disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
depending on their default values. The items in the list are separated by
.code
/home/world/minbari
.endd
-is treated as a file name, but
+is treated as a filename, but
.code
/s=molari/o=babylon/@x400gate.way
.endd
-is treated as an address. For a file name, a transport must be specified using
+is treated as an address. For a filename, a transport must be specified using
the &%file_transport%& option. However, if the generated path name ends with a
forward slash character, it is interpreted as a directory name rather than a
-file name, and &%directory_transport%& is used instead.
+filename, and &%directory_transport%& is used instead.
Normally, either the router or the transport specifies a user and a group under
which to run the delivery. The default is to use the Exim user and group.
.endd
.next
.cindex "address redirection" "to black hole"
-Sometimes you want to throw away mail to a particular local part. Making the
-&%data%& option expand to an empty string does not work, because that causes
-the router to decline. Instead, the alias item
+.cindex "delivery" "discard"
+.cindex "delivery" "blackhole"
.cindex "black hole"
.cindex "abandoning mail"
-&':blackhole:'& can be used. It does what its name implies. No delivery is
+Sometimes you want to throw away mail to a particular local part. Making the
+&%data%& option expand to an empty string does not work, because that causes
+the router to decline. Instead, the alias item
+.code
+:blackhole:
+.endd
+can be used. It does what its name implies. No delivery is
done, and no error message is generated. This has the same effect as specifying
&_/dev/null_& as a destination, but it can be independently disabled.
During routing for message delivery (as opposed to verification), a redirection
containing &':fail:'& causes an immediate failure of the incoming address,
-whereas &':defer:'& causes the message to remain on the queue so that a
+whereas &':defer:'& causes the message to remain in the queue so that a
subsequent delivery attempt can happen at a later time. If an address is
deferred for too long, it will ultimately fail, because the normal retry
rules still apply.
ending in a slash is specified as a new &"address"&. The transport used is
specified by this option, which, after expansion, must be the name of a
configured transport. This should normally be an &(appendfile)& transport. When
-it is running, the file name is in &$address_file$&.
+it is running, the filename is in &$address_file$&.
.option filter_prepend_home redirect boolean true
.option forbid_blackhole redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
If this option is true, the &':blackhole:'& item may not appear in a
redirection list.
.option forbid_exim_filter redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
If this option is set true, only Sieve filters are permitted when
&%allow_filter%& is true.
.option forbid_file redirect boolean false
+.cindex "restricting access to features"
.cindex "delivery" "to file; forbidding"
+.cindex "filter" "locking out certain features"
.cindex "Sieve filter" "forbidding delivery to a file"
.cindex "Sieve filter" "&""keep""& facility; disabling"
If this option is true, this router may not generate a new address that
.option forbid_filter_dlfunc redirect boolean false
+.cindex "restricting access to features"
.cindex "filter" "locking out certain features"
If this option is true, string expansions in Exim filters are not allowed to
make use of the &%dlfunc%& expansion facility to run dynamically loaded
functions.
.option forbid_filter_existstest redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
.cindex "expansion" "statting a file"
If this option is true, string expansions in Exim filters are not allowed to
make use of the &%exists%& condition or the &%stat%& expansion item.
.option forbid_filter_logwrite redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
If this option is true, use of the logging facility in Exim filters is not
permitted. Logging is in any case available only if the filter is being run
under some unprivileged uid (which is normally the case for ordinary users'
.option forbid_filter_lookup redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
If this option is true, string expansions in Exim filter files are not allowed
to make use of &%lookup%& items.
.option forbid_filter_perl redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
This option has an effect only if Exim is built with embedded Perl support. If
it is true, string expansions in Exim filter files are not allowed to make use
of the embedded Perl support.
.option forbid_filter_readfile redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
If this option is true, string expansions in Exim filter files are not allowed
to make use of &%readfile%& items.
.option forbid_filter_readsocket redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
If this option is true, string expansions in Exim filter files are not allowed
to make use of &%readsocket%& items.
.option forbid_filter_reply redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
If this option is true, this router may not generate an automatic reply
message. Automatic replies can be generated only from Exim or Sieve filter
files, not from traditional forward files. This option is forced to be true if
.option forbid_filter_run redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
If this option is true, string expansions in Exim filter files are not allowed
to make use of &%run%& items.
.option forbid_include redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
If this option is true, items of the form
.code
:include:<path name>
.option forbid_pipe redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
.cindex "delivery" "to pipe; forbidding"
If this option is true, this router may not generate a new address which
specifies delivery to a pipe, either from an Exim filter or from a conventional
.option forbid_sieve_filter redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
If this option is set true, only Exim filters are permitted when
&%allow_filter%& is true.
.chapter "Environment for running local transports" "CHAPenvironment" &&&
"Environment for local transports"
.scindex IIDenvlotra1 "local transports" "environment for"
-.scindex IIDenvlotra2 "environment for local transports"
+.scindex IIDenvlotra2 "environment" "local transports"
.scindex IIDenvlotra3 "transport" "local; environment for"
Local transports handle deliveries to files and pipes. (The &(autoreply)&
transport can be thought of as similar to a pipe.) Exim always runs transports
.option event_action transports string&!! unset
.cindex events
This option declares a string to be expanded for Exim's events mechanism.
-For details see &<<CHAPevents>>&.
-.wen
+For details see chapter &<<CHAPevents>>&.
.option group transports string&!! "Exim group"
.cindex "header lines" "adding in transport"
.cindex "transport" "header lines; adding"
This option specifies a list of text headers,
-newline-separated (by default, changeable in the usual way),
+newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
which are (separately) expanded and added to the header
portion of a message as it is transported, as described in section
&<<SECTheadersaddrem>>&. Additional header lines can also be specified by
.cindex "header lines" "removing"
.cindex "transport" "header lines; removing"
This option specifies a list of header names,
-colon-separated (by default, changeable in the usual way);
+colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&);
these headers are omitted from the message as it is transported, as described
in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
routers.
errors and cause the delivery to be deferred.
Unlike most options, &%headers_remove%& can be specified multiple times
-for a router; all listed headers are removed.
+for a transport; all listed headers are removed.
&*Warning*&: Because of the separate expansion of the list items,
items that contain a list separator must have it doubled.
to ensure that any additional groups associated with the uid are set up.
-.new
.option max_parallel transports integer&!! unset
.cindex limit "transport parallelism"
.cindex transport "parallel processes"
.cindex "hints database" "transport concurrency control"
Exim implements this control by means of a hints database in which a record is
-incremented whenever a transport process is beaing created. The record
+incremented whenever a transport process is being created. The record
is decremented and possibly removed when the process terminates.
Obviously there is scope for
records to get left lying around if there is a system or program crash. To
start with &_misc_& and they are kept in the &_spool/db_& directory. There
may be one or two files, depending on the type of DBM in use. The same files
are used for ETRN and smtp transport serialization.
-.wen
.option message_size_limit transports string&!! 0
.option return_path transports string&!! unset
.cindex "envelope sender"
+.cindex "envelope from"
.cindex "transport" "return path; changing"
.cindex "return path" "changing in transport"
If this option is set, the string is expanded at transport time and replaces
This option sets up a filtering (in the Unix shell sense) process for messages
at transport time. It should not be confused with mail filtering as set up by
individual users or via a system filter.
-.new
If unset, or expanding to an empty string, no filtering is done.
-.wen
When the message is about to be written out, the command specified by
&%transport_filter%& is started up in a separate, parallel process, and
fileinto "folder23";
.endd
In this situation, the expansion of &%file%& or &%directory%& in the transport
-must transform the relative path into an appropriate absolute file name. In the
+must transform the relative path into an appropriate absolute filename. In the
case of Sieve filters, the name &'inbox'& must be handled. It is the name that
is used as a result of a &"keep"& action in the filter. This example shows one
way of handling this requirement:
The option must be set to one of the words &"anywhere"&, &"inhome"&, or
&"belowhome"&. In the second and third cases, a home directory must have been
-set for the transport. This option is not useful when an explicit file name is
-given for normal mailbox deliveries. It is intended for the case when file
-names are generated from users' &_.forward_& files. These are usually handled
+set for the transport. This option is not useful when an explicit filename is
+given for normal mailbox deliveries. It is intended for the case when filenames
+are generated from users' &_.forward_& files. These are usually handled
by an &(appendfile)& transport called &%address_file%&. See also
&%file_must_exist%&.
The value of the option is expanded, and must then be a numerical value
(decimal point allowed), optionally followed by one of the letters K, M, or G,
-for kilobytes, megabytes, or gigabytes. If Exim is running on a system with
+for kilobytes, megabytes, or gigabytes, optionally followed by a slash
+and further option modifiers. If Exim is running on a system with
large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
be handled.
+The option modifier &%no_check%& can be used to force delivery even if the over
+quota condition is met. The quota gets updated as usual.
+
&*Note*&: A value of zero is interpreted as &"no quota"&.
The expansion happens while Exim is running as root, before it changes uid for
failure causes delivery to be deferred. A value of zero is interpreted as
&"no quota"&.
+The option modifier &%no_check%& can be used to force delivery even if the over
+quota condition is met. The quota gets updated as usual.
.option quota_is_inclusive appendfile boolean true
See &%quota%& above.
This option applies when one of the delivery modes that writes a separate file
for each message is being used. When Exim wants to find the size of one of
these files in order to test the quota, it first checks &%quota_size_regex%&.
-If this is set to a regular expression that matches the file name, and it
+If this is set to a regular expression that matches the filename, and it
captures one string, that string is interpreted as a representation of the
file's size. The value of &%quota_size_regex%& is not expanded.
This feature is useful only when users have no shell access to their mailboxes
&-- otherwise they could defeat the quota simply by renaming the files. This
facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
-the file length to the file name. For example:
+the file length to the filename. For example:
.code
maildir_tag = ,S=$message_size
quota_size_regex = ,S=(\d+)
number of lines in the message.
The regular expression should not assume that the length is at the end of the
-file name (even though &%maildir_tag%& puts it there) because maildir MUAs
-sometimes add other information onto the ends of message file names.
+filename (even though &%maildir_tag%& puts it there) because maildir MUAs
+sometimes add other information onto the ends of message filenames.
Section &<<SECID136>>& contains further information.
+.new
+This option should not be used when other message-handling software
+may duplicate messages by making hardlinks to the files. When that is done Exim
+will count the message size once for each filename, in contrast with the actual
+disk usage. When the option is not set, calculating total usage requires
+a system-call per file to get the size; the number of links is then available also
+as is used to adjust the effective size.
+.wen
+
.option quota_warn_message appendfile string&!! "see below"
See below for the use of this option. If it is not set when
.option use_bsmtp appendfile boolean false
+.cindex "envelope from"
.cindex "envelope sender"
If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
format, with the envelope sender and recipient(s) included as SMTP commands. If
current time, primary host name, and process id added, by opening for writing
as a new file. If this fails with an access error, delivery is deferred.
.next
-Close the hitching post file, and hard link it to the lock file name.
+Close the hitching post file, and hard link it to the lock filename.
.next
If the call to &[link()]& succeeds, creation of the lock file has succeeded.
Unlink the hitching post name.
directory"&). If the delivery is successful, the file is renamed into the
&_new_& subdirectory.
-In the file name, <&'stime'&> is the current time of day in seconds, and
+In the filename, <&'stime'&> is the current time of day in seconds, and
<&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
Exim checks that the time-of-day clock has moved on by at least one microsecond
before terminating the delivery process. This guarantees uniqueness for the
-file name. However, as a precaution, Exim calls &[stat()]& for the file before
+filename. However, as a precaution, Exim calls &[stat()]& for the file before
opening it. If any response other than ENOENT (does not exist) is given,
Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
This does not apply to &'Cc:'& or &'Bcc:'& recipients.
If &%once%& is unset, or is set to an empty string, the message is always sent.
-By default, if &%once%& is set to a non-empty file name, the message
+By default, if &%once%& is set to a non-empty filename, the message
is not sent if a potential recipient is already listed in the database.
However, if the &%once_repeat%& option specifies a time greater than zero, the
message is sent if that much time has elapsed since a message was last sent to
delivery, the two pipe transports may be run concurrently. You must ensure that
any pipe commands you set up are robust against this happening. If the commands
write to a file, the &%exim_lock%& utility might be of use.
-.new
Alternatively the &%max_parallel%& option could be used with a value
of "1" to enforce serialization.
-.wen
.cindex "filter" "transport filter"
.vindex "&$pipe_addresses$&"
Special handling takes place when an argument consists of precisely the text
-&`$pipe_addresses`&. This is not a general expansion variable; the only
+&`$pipe_addresses`& (no quotes).
+This is not a general expansion variable; the only
place this string is recognized is when it appears as an argument for a pipe or
transport filter command. It causes each address that is being handled to be
inserted in the argument list at that point &'as a separate argument'&. This
avoids any problems with spaces or shell metacharacters, and is of use when a
&(pipe)& transport is handling groups of addresses in a batch.
-If &%force_command%& is enabled on the transport, Special handling takes place
+If &%force_command%& is enabled on the transport, special handling takes place
for an argument that consists of precisely the text &`$address_pipe`&. It
is handled similarly to &$pipe_addresses$& above. It is expanded and each
argument is inserted in the argument list at that point
.section "Environment variables" "SECTpipeenv"
.cindex "&(pipe)& transport" "environment for command"
-.cindex "environment for pipe transport"
+.cindex "environment" "&(pipe)& transport"
The environment variables listed below are set up when the command is invoked.
This list is a compromise for maximum compatibility with other MTAs. Note that
the &%environment%& option can be used to add additional variables to this
-environment.
+environment. The environment for the &(pipe)& transport is not subject
+to the &%add_environment%& and &%keep_environment%& main config options.
.display
&`DOMAIN `& the domain of the address
&`HOME `& the home directory, if set
.option environment pipe string&!! unset
.cindex "&(pipe)& transport" "environment for command"
-.cindex "environment for &(pipe)& transport"
+.cindex "environment" "&(pipe)& transport"
This option is used to add additional variables to the environment in which the
command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
a string which is expanded, and then interpreted as a colon-separated list of
&`\n`& to &`\r\n`& in &%message_suffix%&.
-.option path pipe string "see below"
-This option specifies the string that is set up in the PATH environment
-variable of the subprocess. The default is:
-.code
-/bin:/usr/bin
-.endd
+.option path pipe string&!! "/bin:/usr/bin"
+This option is expanded and
+specifies the string that is set up in the PATH environment
+variable of the subprocess.
If the &%command%& option does not yield an absolute path name, the command is
sought in the PATH directories, in the usual way. &*Warning*&: This does not
apply to a command specified as a transport filter.
option.
+.option dane_require_tls_ciphers smtp string&!! unset
+.cindex "TLS" "requiring specific ciphers for DANE"
+.cindex "cipher" "requiring specific"
+.cindex DANE "TLS ciphers"
+This option may be used to override &%tls_require_ciphers%& for connections
+where DANE has been determined to be in effect.
+If not set, then &%tls_require_ciphers%& will be used.
+Normal SMTP delivery is not able to make strong demands of TLS cipher
+configuration, because delivery will fall back to plaintext. Once DANE has
+been determined to be in effect, there is no plaintext fallback and making the
+TLS cipherlist configuration stronger will increase security, rather than
+counter-intuitively decreasing it.
+If the option expands to be empty or is forced to fail, then it will
+be treated as unset and &%tls_require_ciphers%& will be used instead.
+
+
.option data_timeout smtp time 5m
This sets a timeout for the transmission of each block in the data portion of
the message. As a result, the overall timeout for a message depends on the size
of the message. Its value must not be zero. See also &%final_timeout%&.
+.option dkim_canon smtp string&!! unset
+DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
+.option dkim_domain smtp string list&!! unset
+DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
+.option dkim_hash smtp string&!! sha256
+DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
+.option dkim_identity smtp string&!! unset
+DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
+.option dkim_private_key smtp string&!! unset
+DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
+.option dkim_selector smtp string&!! unset
+DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
+.option dkim_strict smtp string&!! unset
+DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
+.option dkim_sign_headers smtp string&!! "per RFC"
+DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
+.option dkim_timestamps smtp string&!! unset
+DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
+
+
.option delay_after_cutoff smtp boolean true
+.cindex "final cutoff" "retries, controlling"
+.cindex retry "final cutoff"
This option controls what happens when all remote IP addresses for a given
domain have been inaccessible for so long that they have passed their retry
cutoff times.
details.
-.option dnssec_request_domains smtp "domain list&!!" unset
+.option dnssec_request_domains smtp "domain list&!!" *
.cindex "MX record" "security"
.cindex "DNSSEC" "MX lookup"
.cindex "security" "MX lookup"
.cindex "DNS" "DNSSEC"
DNS lookups for domains matching &%dnssec_request_domains%& will be done with
-the dnssec request bit set.
-This applies to all of the SRV, MX, AAAA, A lookup sequence.
+the dnssec request bit set. Setting this transport option is only useful if the
+transport overrides or sets the host names. See the &%dnssec_request_domains%&
+router option.
.cindex "DNSSEC" "MX lookup"
.cindex "security" "MX lookup"
.cindex "DNS" "DNSSEC"
-DNS lookups for domains matching &%dnssec_request_domains%& will be done with
-the dnssec request bit set. Any returns not having the Authenticated Data bit
-(AD bit) set will be ignored and logged as a host-lookup failure.
-This applies to all of the SRV, MX, AAAA, A lookup sequence.
+DNS lookups for domains matching &%dnssec_require_domains%& will be done with
+the dnssec request bit set. Setting this transport option is only
+useful if the transport overrides or sets the host names. See the
+&%dnssec_require_domains%& router option.
Exim will not use the SMTP PIPELINING extension when delivering to any host
that matches this list, even if the server host advertises PIPELINING support.
+.new
+.option hosts_pipe_connect smtp "host list&!!" unset
+.cindex "pipelining" "early connection"
+.cindex "pipelining" PIPE_CONNECT
+If Exim is built with the SUPPORT_PIPE_CONNECT build option
+this option controls which to hosts the facility watched for
+and recorded, and used for subsequent connections.
+
+The retry hints database is used for the record,
+and records are subject to the &%retry_data_expire%& option.
+When used, the pipelining saves on roundtrip times.
+It also turns SMTP into a client-first protocol
+so combines well with TCP Fast Open.
+
+See also the &%pipelining_connect_advertise_hosts%& main option.
+
+Note:
+When the facility is used, the transport &%helo_data%& option
+will be expanded before the &$sending_ip_address$& variable
+is filled in.
+A check is made for the use of that variable, without the
+presence of a &"def:"& test on it, but suitably complex coding
+can avoid the check and produce unexpected results.
+You have been warned.
+.wen
+
.option hosts_avoid_tls smtp "host list&!!" unset
.cindex "TLS" "avoiding for certain hosts"
message on the same connection. See section &<<SECTmulmessam>>& for an
explanation of when this might be needed.
+.new
+.option hosts_noproxy_tls smtp "host list&!!" unset
+.cindex "TLS" "passing connection"
+.cindex "multiple SMTP deliveries"
+.cindex "TLS" "multiple message deliveries"
+For any host that matches this list, a TLS session which has
+been started will not be passed to a new delivery process for sending another
+message on the same session.
+.wen
+
+The traditional implementation closes down TLS and re-starts it in the new
+process, on the same open TCP connection, for each successive message
+sent. If permitted by this option a pipe to to the new process is set up
+instead, and the original process maintains the TLS connection and proxies
+the SMTP connection from and to the new process and any subsequents.
+The new process has no access to TLS information, so cannot include it in
+logging.
+
+
.option hosts_override smtp boolean false
If this option is set and the &%hosts%& option is also set, any hosts that are
TLS session for any host that matches this list.
&%tls_verify_certificates%& should also be set for the transport.
+.option hosts_require_dane smtp "host list&!!" unset
+.cindex DANE "transport options"
+.cindex DANE "requiring for certain servers"
+If built with DANE support, Exim will require that a DNSSEC-validated
+TLSA record is present for any host matching the list,
+and that a DANE-verified TLS connection is made. See
+the &%dnssec_request_domains%& router and transport options.
+There will be no fallback to in-clear communication.
+See section &<<SECDANE>>&.
+
.option hosts_require_ocsp smtp "host list&!!" unset
.cindex "TLS" "requiring for certain servers"
Exim will request, and check for a valid Certificate Status being given, on a
unauthenticated. See also &%hosts_require_auth%&, and chapter
&<<CHAPSMTPAUTH>>& for details of authentication.
+.option hosts_try_chunking smtp "host list&!!" *
+.cindex CHUNKING "enabling, in client"
+.cindex BDAT "SMTP command"
+.cindex "RFC 3030" "CHUNKING"
+This option provides a list of servers to which, provided they announce
+CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
+BDAT will not be used in conjunction with a transport filter.
+
+.option hosts_try_dane smtp "host list&!!" *
+.cindex DANE "transport options"
+.cindex DANE "attempting for certain servers"
+If built with DANE support, Exim will require that a DNSSEC-validated
+TLSA record is present for any host matching the list,
+and that a DANE-verified TLS connection is made. See
+the &%dnssec_request_domains%& router and transport options.
+There will be no fallback to in-clear communication.
+See section &<<SECDANE>>&.
+
+.option hosts_try_fastopen smtp "host list&!!" *
+.cindex "fast open, TCP" "enabling, in client"
+.cindex "TCP Fast Open" "enabling, in client"
+.cindex "RFC 7413" "TCP Fast Open"
+This option provides a list of servers to which, provided
+the facility is supported by this system, Exim will attempt to
+perform a TCP Fast Open.
+No data is sent on the SYN segment but, if the remote server also
+supports the facility, it can send its SMTP banner immediately after
+the SYN,ACK segment. This can save up to one round-trip time.
+
+The facility is only active for previously-contacted servers,
+as the initiator must present a cookie in the SYN segment.
+
+On (at least some) current Linux distributions the facility must be enabled
+in the kernel by the sysadmin before the support is usable.
+There is no option for control of the server side; if the system supports
+it it is always enabled. Note that lengthy operations in the connect ACL,
+such as DNSBL lookups, will still delay the emission of the SMTP banner.
+
.option hosts_try_prdr smtp "host list&!!" *
.cindex "PRDR" "enabling, optional in client"
This option provides a list of servers to which, provided they announce
during the expansion of the string. Forced expansion failure, or an empty
string result causes the option to be ignored. Otherwise, after expansion, the
string must be a list of IP addresses, colon-separated by default, but the
-separator can be changed in the usual way. For example:
+separator can be changed in the usual way (&<<SECTlistsepchange>>&).
+For example:
.code
interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
.endd
If the value of this option begins with a digit it is taken as a port number;
otherwise it is looked up using &[getservbyname()]&. The default value is
-normally &"smtp"&, but if &%protocol%& is set to &"lmtp"&, the default is
-&"lmtp"&. If the expansion fails, or if a port number cannot be found, delivery
+normally &"smtp"&,
+but if &%protocol%& is set to &"lmtp"& the default is &"lmtp"&
+and if &%protocol%& is set to &"smtps"& the default is &"smtps"&.
+If the expansion fails, or if a port number cannot be found, delivery
is deferred.
+Note that at least one Linux distribution has been seen failing
+to put &"smtps"& in its &"/etc/services"& file, resulting is such deferrals.
+
.option protocol smtp string smtp
If this option is set to &"smtps"&, the default value for the &%port%& option
changes to &"smtps"&, and the transport initiates TLS immediately after
connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
-The Internet standards bodies strongly discourage use of this mode.
+The Internet standards bodies used to strongly discourage use of this mode,
+but as of RFC 8314 it is perferred over STARTTLS for message submission
+(as distinct from MTA-MTA communication).
.option retry_include_ip_address smtp boolean&!! true
may be one or two files, depending on the type of DBM in use. The same files
are used for ETRN serialization.
-.new
See also the &%max_parallel%& generic transport option.
-.wen
.option size_addition smtp integer 1024
the use of the SIZE option altogether.
-.new
.option socks_proxy smtp string&!! unset
.cindex proxy SOCKS
This option enables use of SOCKS proxies for connections made by the
-transport. For details see &<<SECTproxySOCKS>>&.
-.wen
+transport. For details see section &<<SECTproxySOCKS>>&.
.option tls_certificate smtp string&!! unset
.option tls_verify_hosts smtp "host list&!!" unset
.cindex "TLS" "server certificate verification"
.cindex "certificate" "verification of server"
-This option gives a list of hosts for which. on encrypted connections,
+This option gives a list of hosts for which, on encrypted connections,
certificate verification must succeed.
The &%tls_verify_certificates%& option must also be set.
If both this option and &%tls_try_verify_hosts%& are unset
operation is as if this option selected all hosts.
+.option utf8_downconvert smtp integer!! unset
+.cindex utf8 "address downconversion"
+.cindex i18n "utf8 address downconversion"
+If built with internationalization support,
+this option controls conversion of UTF-8 in message addresses
+to a-label form.
+For details see section &<<SECTi18nMTA>>&.
+
rewriting is applied immediately to child addresses that are generated by
redirection, unless &%no_rewrite%& is set on the router.
+.cindex "envelope from"
.cindex "envelope sender" "rewriting at transport time"
.cindex "rewriting" "at transport time"
.cindex "header lines" "rewriting at transport time"
.section "Testing the rewriting rules that apply on input" "SECID149"
.cindex "rewriting" "testing"
.cindex "testing" "rewriting"
-Exim's input rewriting configuration appears in a part of the run time
+Exim's input rewriting configuration appears in a part of the runtime
configuration file headed by &"begin rewrite"&. It can be tested by the
&%-brw%& command line option. This takes an address (which can be a full RFC
2822 address) as its argument. The output is a list of how the address would be
messages. If this delivery fails, the address fails immediately. The
post-cutoff retry time is not used.
+.cindex "final cutoff" "retries, controlling"
+.cindex retry "final cutoff"
If the delivery is remote, there are two possibilities, controlled by the
.oindex "&%delay_after_cutoff%&"
&%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
-default. Until the post-cutoff retry time for one of the IP addresses is
+default. Until the post-cutoff retry time for one of the IP addresses,
+as set by the &%retry_data_expire%& option, is
reached, the failing email address is bounced immediately, without a delivery
attempt taking place. After that time, one new delivery attempt is made to
those IP addresses that are past their retry times, and if that still fails,
its delivery when others to the same address get through. In this situation,
because some messages are successfully delivered, the &"retry clock"& for the
host or address keeps getting reset by the successful deliveries, and so
-failing messages remain on the queue for ever because the cutoff time is never
+failing messages remain in the queue for ever because the cutoff time is never
reached.
Two exceptional actions are applied to prevent this happening. The first
.chapter "SMTP authentication" "CHAPSMTPAUTH"
.scindex IIDauthconf1 "SMTP" "authentication configuration"
.scindex IIDauthconf2 "authentication"
-The &"authenticators"& section of Exim's run time configuration is concerned
+The &"authenticators"& section of Exim's runtime configuration is concerned
with SMTP authentication. This facility is an extension to the SMTP protocol,
described in RFC 2554, which allows a client SMTP host to authenticate itself
to a server. This is a common way for a server to recognize clients that are
AUTH_CRAM_MD5=yes
AUTH_CYRUS_SASL=yes
AUTH_DOVECOT=yes
+AUTH_EXTERNAL=yes
AUTH_GSASL=yes
AUTH_HEIMDAL_GSSAPI=yes
AUTH_PLAINTEXT=yes
the Cyrus SASL authentication library.
The third is an interface to Dovecot's authentication system, delegating the
work via a socket interface.
-The fourth provides an interface to the GNU SASL authentication library, which
+.new
+The fourth provides for negotiation of authentication done via non-SMTP means,
+as defined by RFC 4422 Appendix A.
+.wen
+The fifth provides an interface to the GNU SASL authentication library, which
provides mechanisms but typically not data sources.
-The fifth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
+The sixth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
supporting setting a server keytab.
-The sixth can be configured to support
+The seventh can be configured to support
the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
-not formally documented, but used by several MUAs. The seventh authenticator
+not formally documented, but used by several MUAs.
+The eighth authenticator
supports Microsoft's &'Secure Password Authentication'& mechanism.
-The eighth is an Exim authenticator but not an SMTP one;
+The last is an Exim authenticator but not an SMTP one;
instead it can use information from a TLS negotiation.
The authenticators are configured using the same syntax as other drivers (see
.option server_set_id authenticators string&!! unset
.vindex "&$authenticated_id$&"
+.vindex "&$authenticated_fail_id$&"
When an Exim server successfully authenticates a client, this string is
expanded using data from the authentication, and preserved for any incoming
messages in the variable &$authenticated_id$&. It is also included in the log
lines for incoming messages. For example, a user/password authenticator
configuration might preserve the user name that was used to authenticate, and
refer to it subsequently during delivery of the message.
+On a failing authentication the expansion result is instead saved in
+the &$authenticated_fail_id$& variable.
If expansion fails, the option is ignored.
client from which the message was received. This variable is empty if there was
no successful authentication.
+.cindex authentication "expansion item"
+Successful authentication sets up information used by the
+&%authresults%& expansion item.
+
deliver the message unauthenticated.
.endlist
+Note that the hostlist test for whether to do authentication can be
+confused if name-IP lookups change between the time the peer is decided
+upon and the time that the transport runs. For example, with a manualroute
+router given a host name, and with DNS "round-robin" used by that name: if
+the local resolver cache times out between the router and the transport
+running, the transport may get an IP for the name for its authentication
+check which does not match the connection peer IP.
+No authentication will then be done, despite the names being identical.
+
+For such cases use a separate transport which always authenticates.
+
.cindex "AUTH" "on MAIL command"
When Exim has authenticated itself to a remote server, it adds the AUTH
parameter to the MAIL commands it sends, if it has an authenticated sender for
expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
For any other result, a temporary error code is returned, with the expanded
-string as the error text
+string as the error text.
&*Warning*&: If you use a lookup in the expansion to find the user's
password, be sure to make the authentication fail if the user is unknown.
.scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
.cindex "Cyrus" "SASL library"
.cindex "Kerberos"
-The code for this authenticator was provided by Matthew Byng-Maddick of A L
-Digital Ltd (&url(http://www.aldigital.co.uk)).
+The code for this authenticator was provided by Matthew Byng-Maddick while
+at A L Digital Ltd.
The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
library implementation of the RFC 2222 (&"Simple Authentication and Security
then so can the &(cyrus_sasl)& authenticator. By default it uses the public
name of the driver to determine which mechanism to support.
-Where access to some kind of secret file is required, for example in GSSAPI
+Where access to some kind of secret file is required, for example, in GSSAPI
or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
user, and that the Cyrus SASL library has no way of escalating privileges
by default. You may also find you need to set environment variables,
.option server_socket dovecot string unset
-This option must specify the socket that is the interface to Dovecot
+This option must specify the UNIX socket that is the interface to Dovecot
authentication. The &%public_name%& option must specify an authentication
mechanism that Dovecot is configured to support. You can have several
authenticators for different mechanisms. For example:
made that any particular new authentication mechanism will be supported
without code changes in Exim.
+Exim's &(gsasl)& authenticator does not have client-side support at this
+time; only the server-side support is implemented. Patches welcome.
+
.option server_channelbinding gsasl boolean false
+Do not set this true without consulting a cryptographic engineer.
+
Some authentication mechanisms are able to use external context at both ends
of the session to bind the authentication to that context, and fail the
authentication process if that context differs. Specifically, some TLS
ciphersuites can provide identifying information about the cryptographic
context.
-This means that certificate identity and verification becomes a non-issue,
-as a man-in-the-middle attack will cause the correct client and server to
-see different identifiers and authentication will fail.
+This should have meant that certificate identity and verification becomes a
+non-issue, as a man-in-the-middle attack will cause the correct client and
+server to see different identifiers and authentication will fail.
This is currently only supported when using the GnuTLS library. This is
only usable by mechanisms which support "channel binding"; at time of
This defaults off to ensure smooth upgrade across Exim releases, in case
this option causes some clients to start failing. Some future release
-of Exim may switch the default to be true.
+of Exim might have switched the default to be true.
+
+However, Channel Binding in TLS has proven to be broken in current versions.
+Do not plan to rely upon this feature for security, ever, without consulting
+with a subject matter expert (a cryptographic engineer).
.option server_hostname gsasl string&!! "see below"
Password Authentication'& mechanism,
which is also sometimes known as NTLM (NT LanMan). The code for client side of
this authenticator was contributed by Marc Prud'hommeaux, and much of it is
-taken from the Samba project (&url(http://www.samba.org)). The code for the
+taken from the Samba project (&url(https://www.samba.org/)). The code for the
server side was subsequently contributed by Tom Kistner. The mechanism works as
follows:
+. ////////////////////////////////////////////////////////////////////////////
+. ////////////////////////////////////////////////////////////////////////////
+
+.chapter "The external authenticator" "CHAPexternauth"
+.scindex IIDexternauth1 "&(external)& authenticator"
+.scindex IIDexternauth2 "authenticators" "&(external)&"
+.cindex "authentication" "Client Certificate"
+.cindex "authentication" "X509"
+.cindex "Certificate-based authentication"
+The &(external)& authenticator provides support for
+authentication based on non-SMTP information.
+The specification is in RFC 4422 Appendix A
+(&url(https://tools.ietf.org/html/rfc4422)).
+It is only a transport and negotiation mechanism;
+the process of authentication is entirely controlled
+by the server configuration.
+
+The client presents an identity in-clear.
+It is probably wise for a server to only advertise,
+and for clients to only attempt,
+this authentication method on a secure (eg. under TLS) connection.
+
+One possible use, compatible with the
+K-9 Mail Andoid client (&url(https://k9mail.github.io/)),
+is for using X509 client certificates.
+
+It thus overlaps in function with the TLS authenticator
+(see &<<CHAPtlsauth>>&)
+but is a full SMTP SASL authenticator
+rather than being implicit for TLS-connection carried
+client certificates only.
+
+The examples and discussion in this chapter assume that
+client-certificate authentication is being done.
+
+The client must present a certificate,
+for which it must have been requested via the
+&%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
+(see &<<CHAPTLS>>&).
+For authentication to be effective the certificate should be
+verifiable against a trust-anchor certificate known to the server.
+
+.section "External options" "SECTexternsoptions"
+.cindex "options" "&(external)& authenticator (server)"
+The &(external)& authenticator has two server options:
+
+.option server_param2 external string&!! unset
+.option server_param3 external string&!! unset
+.cindex "variables (&$auth1$& &$auth2$& etc)" "in &(external)& authenticator"
+These options are expanded before the &%server_condition%& option
+and the result are placed in &$auth2$& and &$auth3$& resectively.
+If the expansion is forced to fail, authentication fails. Any other expansion
+failure causes a temporary error code to be returned.
+
+They can be used to clarify the coding of a complex &%server_condition%&.
+
+.section "Using external in a server" "SECTexternserver"
+.cindex "AUTH" "in &(external)& authenticator"
+.cindex "numerical variables (&$1$& &$2$& etc)" &&&
+ "in &(external)& authenticator"
+.vindex "&$auth1$&, &$auth2$&, etc"
+.cindex "base64 encoding" "in &(external)& authenticator"
+
+When running as a server, &(external)& performs the authentication test by
+expanding a string. The data sent by the client with the AUTH command, or in
+response to subsequent prompts, is base64 encoded, and so may contain any byte
+values when decoded. The decoded value is treated as
+an identity for authentication and
+placed in the expansion variable &$auth1$&.
+
+For compatibility with previous releases of Exim, the value is also placed in
+the expansion variable &$1$&. However, the use of this
+variable for this purpose is now deprecated, as it can lead to confusion in
+string expansions that also use them for other things.
+
+.vindex "&$authenticated_id$&"
+Once an identity has been received,
+&%server_condition%& is expanded. If the expansion is forced to fail,
+authentication fails. Any other expansion failure causes a temporary error code
+to be returned. If the result of a successful expansion is an empty string,
+&"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
+expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
+generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
+For any other result, a temporary error code is returned, with the expanded
+string as the error text.
+
+Example:
+.code
+ext_ccert_san_mail:
+ driver = external
+ public_name = EXTERNAL
+
+ server_advertise_condition = $tls_in_certificate_verified
+ server_param2 = ${certextract {subj_altname,mail,>:} \
+ {$tls_in_peercert}}
+ server_condition = ${if forany {$auth2} \
+ {eq {$item}{$auth1}}}
+ server_set_id = $auth1
+.endd
+This accepts a client certificate that is verifiable against any
+of your configured trust-anchors
+(which usually means the full set of public CAs)
+and which has a mail-SAN matching the claimed identity sent by the client.
+
+Note that, up to TLS1.2, the client cert is on the wire in-clear, including the SAN,
+The account name is therefore guessable by an opponent.
+TLS 1.3 protects both server and client certificates, and is not vulnerable
+in this way.
+Likewise, a traditional plaintext SMTP AUTH done inside TLS is not.
+
+
+.section "Using external in a client" "SECTexternclient"
+.cindex "options" "&(external)& authenticator (client)"
+The &(external)& authenticator has one client option:
+
+.option client_send external string&!! unset
+This option is expanded and sent with the AUTH command as the
+identity being asserted.
+
+Example:
+.code
+ext_ccert:
+ driver = external
+ public_name = EXTERNAL
+
+ client_condition = ${if !eq{$tls_out_cipher}{}}
+ client_send = myaccount@smarthost.example.net
+.endd
+
+
+.ecindex IIDexternauth1
+.ecindex IIDexternauth2
+
+
+
+
+
. ////////////////////////////////////////////////////////////////////////////
. ////////////////////////////////////////////////////////////////////////////
driver = tls
server_param1 = ${certextract {subj_altname,mail,>:} \
{$tls_in_peercert}}
- server_condition = ${if forany {$auth1} \
+ server_condition = ${if and { {eq{$tls_in_certificate_verified}{1}} \
+ {forany {$auth1} \
{!= {0} \
{${lookup ldap{ldap:///\
mailname=${quote_ldap_dn:${lc:$item}},\
ou=users,LDAP_DC?mailid} {$value}{0} \
- } } } }
+ } } } }}}
server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
.endd
This accepts a client certificate that is verifiable against any
of your configured trust-anchors
-which usually means the full set of public CAs)
+(which usually means the full set of public CAs)
and which has a SAN with a good account name.
-Note that the client cert is on the wire in-clear, including the SAN,
-whereas a plaintext SMTP AUTH done inside TLS is not.
+
+Note that, up to TLS1.2, the client cert is on the wire in-clear, including the SAN,
+The account name is therefore guessable by an opponent.
+TLS 1.3 protects both server and client certificates, and is not vulnerable
+in this way.
+Likewise, a traditional plaintext SMTP AUTH done inside TLS is not.
. An alternative might use
. .code
. to require one of a set of specific certs that define a given account
. (the verification is still required, but mostly irrelevant).
. This would help for per-device use.
-.
+.
. However, for the future we really need support for checking a
. user cert in LDAP - which probably wants a base-64 DER.
-.section "Support for the legacy &""ssmtp""& (aka &""smtps""&) protocol" &&&
+.section "Support for the &""submissions""& (aka &""ssmtp""& and &""smtps""&) protocol" &&&
"SECID284"
+.cindex "submissions protocol"
.cindex "ssmtp protocol"
.cindex "smtps protocol"
+.cindex "SMTP" "submissions protocol"
.cindex "SMTP" "ssmtp protocol"
.cindex "SMTP" "smtps protocol"
-Early implementations of encrypted SMTP used a different TCP port from normal
-SMTP, and expected an encryption negotiation to start immediately, instead of
-waiting for a STARTTLS command from the client using the standard SMTP
-port. The protocol was called &"ssmtp"& or &"smtps"&, and port 465 was
-allocated for this purpose.
-
-This approach was abandoned when encrypted SMTP was standardized, but there are
-still some legacy clients that use it. Exim supports these clients by means of
-the &%tls_on_connect_ports%& global option. Its value must be a list of port
-numbers; the most common use is expected to be:
+The history of port numbers for TLS in SMTP is a little messy and has been
+contentious. As of RFC 8314, the common practice of using the historically
+allocated port 465 for "email submission but with TLS immediately upon connect
+instead of using STARTTLS" is officially blessed by the IETF, and recommended
+by them in preference to STARTTLS.
+
+The name originally assigned to the port was &"ssmtp"& or &"smtps"&, but as
+clarity emerged over the dual roles of SMTP, for MX delivery and Email
+Submission, nomenclature has shifted. The modern name is now &"submissions"&.
+
+This approach was, for a while, officially abandoned when encrypted SMTP was
+standardized, but many clients kept using it, even as the TCP port number was
+reassigned for other use.
+Thus you may encounter guidance claiming that you shouldn't enable use of
+this port.
+In practice, a number of mail-clients have only ever supported submissions,
+not submission with STARTTLS upgrade.
+Ideally, offer both submission (587) and submissions (465) service.
+
+Exim supports TLS-on-connect by means of the &%tls_on_connect_ports%&
+global option. Its value must be a list of port numbers;
+the most common use is expected to be:
.code
tls_on_connect_ports = 465
.endd
defined elsewhere.
There is also a &%-tls-on-connect%& command line option. This overrides
-&%tls_on_connect_ports%&; it forces the legacy behaviour for all ports.
+&%tls_on_connect_ports%&; it forces the TLS-only behaviour for all ports.
.code
USE_GNUTLS=yes
.endd
-in Local/Makefile, in addition to
-.code
-SUPPORT_TLS=yes
-.endd
-You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
+in Local/Makefile
+you must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
include files and libraries for GnuTLS can be found.
There are some differences in usage when using GnuTLS instead of OpenSSL:
(If an API is found to let OpenSSL be configured in this way,
let the Exim Maintainers know and we'll likely use it).
.next
+With GnuTLS, if an explicit list is used for the &%tls_privatekey%& main option
+main option, it must be ordered to match the &%tls_certificate%& list.
+.next
Some other recently added features may only be available in one or the other.
This should be documented with the feature. If the documentation does not
explicitly state that the feature is infeasible in the other TLS
.oindex "&%tls_require_ciphers%&" "OpenSSL"
There is a function in the OpenSSL library that can be passed a list of cipher
suites before the cipher negotiation takes place. This specifies which ciphers
-are acceptable. The list is colon separated and may contain names like
+are acceptable for TLS versions prior to 1.3.
+The list is colon separated and may contain names like
DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
directly to this function call.
Many systems will install the OpenSSL manual-pages, so you may have
{HIGH:!MD5:!SHA1}}
.endd
+This example will prefer ECDSA-authenticated ciphers over RSA ones:
+.code
+tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT
+.endd
+
+For TLS version 1.3 the control available is less fine-grained
+and Exim does not provide access to it at present.
+The value of the &%tls_require_ciphers%& option is ignored when
+TLS version 1.3 is negotiated.
+
+As of writing the library default cipher suite list for TLSv1.3 is
+.code
+TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
+.endd
.section "Requiring specific ciphers or other parameters in GnuTLS" &&&
Documentation of the strings accepted may be found in the GnuTLS manual, under
"Priority strings". This is online as
-&url(http://www.gnutls.org/manual/html_node/Priority-Strings.html),
+&url(https://www.gnutls.org/manual/html_node/Priority-Strings.html),
but beware that this relates to GnuTLS 3, which may be newer than the version
installed on your system. If you are using GnuTLS 3,
-&url(http://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string, then the example code)
+then the example code
+&url(https://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string)
on that site can be used to test a given string.
For example:
.cindex "TLS" "configuring an Exim server"
When Exim has been built with TLS support, it advertises the availability of
the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
-but not to any others. The default value of this option is unset, which means
-that STARTTLS is not advertised at all. This default is chosen because you
-need to set some other options in order to make TLS available, and also it is
-sensible for systems that want to use TLS only as a client.
+but not to any others. The default value of this option is *, which means
+that STARTTLS is always advertised. Set it to blank to never advertise;
+this is reasonable for systems that want to use TLS only as a client.
+
+If STARTTLS is to be used you
+need to set some other options in order to make TLS available.
If a client issues a STARTTLS command and there is some configuration
problem in the server, the command is rejected with a 454 error. If the client
If a STARTTLS command is issued within an existing TLS session, it is
rejected with a 554 error code.
-To enable TLS operations on a server, you must set &%tls_advertise_hosts%& to
-match some hosts. You can, of course, set it to * to match all hosts.
-However, this is not all you need to do. TLS sessions to a server won't work
-without some further configuration at the server end.
+To enable TLS operations on a server, the &%tls_advertise_hosts%& option
+must be set to match some hosts. The default is * which matches all hosts.
+
+If this is all you do, TLS encryption will be enabled but not authentication -
+meaning that the peer has no assurance it is actually you he is talking to.
+You gain protection from a passive sniffer listening on the wire but not
+from someone able to intercept the communication.
-It is rumoured that all existing clients that support TLS/SSL use RSA
-encryption. To make this work you need to set, in the server,
+Further protection requires some further configuration at the server end.
+
+To make TLS work you need to set, in the server,
.code
tls_certificate = /some/file/name
tls_privatekey = /some/file/name
certificates that need to be sent to the client to enable it to authenticate
the server's certificate.
+For dual-stack (eg. RSA and ECDSA) configurations, these options can be
+colon-separated lists of file paths. Ciphers using given authentication
+algorithms require the presence of a suitable certificate to supply the
+public-key. The server selects among the certificates to present to the
+client depending on the selected cipher, hence the priority ordering for
+ciphers will affect which certificate is used.
+
If you do not understand about certificates and keys, please try to find a
source of this background information, which is not Exim-specific. (There are a
few comments below in section &<<SECTcerandall>>&.)
apply to all TLS connections. For any host that matches one of these options,
Exim requests a certificate as part of the setup of the TLS session. The
contents of the certificate are verified by comparing it with a list of
-expected certificates.
+expected trust-anchors or certificates.
These may be the system default set (depending on library version),
an explicit file or,
depending on library version, a directory, identified by
.endd
where &_/cert/file_& contains a single certificate.
+There is no checking of names of the client against the certificate
+Subject Name or Subject Alternate Names.
+
The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
what happens if the client does not supply a certificate, or if the certificate
does not match any of the certificates in the collection named by
proof expires. The downside is that it requires server support.
Unless Exim is built with the support disabled,
-.new
or with GnuTLS earlier than version 3.3.16 / 3.4.8
-.wen
support for OCSP stapling is included.
There is a global option called &%tls_ocsp_file%&.
-.section "Configuring an Exim client to use TLS" "SECID185"
+.section "Configuring an Exim client to use TLS" "SECTclientTLS"
.cindex "cipher" "logging"
.cindex "log" "TLS cipher"
.cindex "log" "distinguished name"
if it requests it. If the server is Exim, it will request a certificate only if
&%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
+.new
+Do not use a certificate which has the OCSP-must-staple extension,
+for client use (they are usable for server use).
+As TLS has no means for the client to staple before TLS 1.3 it will result
+in failed connections.
+.wen
+
If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
specifies a collection of expected server certificates.
-These may be the system default set (depending on library version),
-a file or,
-depending on library version, a directory,
-must name a file or,
-for OpenSSL only (not GnuTLS), a directory.
+These may be
+the system default set (depending on library version),
+a file,
+or (depending on library version) a directory.
The client verifies the server's certificate
against this collection, taking into account any revoked certificates that are
in the list defined by &%tls_crl%&.
certificate verification to the listed servers. Verification either must
or need not succeed respectively.
+The &%tls_verify_cert_hostnames%& option lists hosts for which additional
+checks are made: that the host name (the one in the DNS A record)
+is valid for the certificate.
+The option defaults to always checking.
+
The &(smtp)& transport has two OCSP-related options:
&%hosts_require_ocsp%&; a host-list for which a Certificate Status
is requested and required for the connection to proceed. The default
during TLS session handshake, to permit alternative values to be chosen:
.ilist
-.vindex "&%tls_certificate%&"
&%tls_certificate%&
.next
-.vindex "&%tls_crl%&"
&%tls_crl%&
.next
-.vindex "&%tls_privatekey%&"
&%tls_privatekey%&
.next
-.vindex "&%tls_verify_certificates%&"
&%tls_verify_certificates%&
.next
-.vindex "&%tls_ocsp_file%&"
&%tls_ocsp_file%&
.endlist
Great care should be taken to deal with matters of case, various injection
attacks in the string (&`../`& or SQL), and ensuring that a valid filename
-can always be referenced; it is important to remember that &$tls_sni$& is
+can always be referenced; it is important to remember that &$tls_in_sni$& is
arbitrary unverified data provided prior to authentication.
+Further, the initial certificate is loaded before SNI has arrived, so
+an expansion for &%tls_certificate%& must have a default which is used
+when &$tls_in_sni$& is empty.
The Exim developers are proceeding cautiously and so far no other TLS options
are re-expanded.
one process to the next. This implementation does not fit well with the use
of TLS, because there is quite a lot of state information associated with a TLS
connection, not just a socket identification. Passing all the state information
-to a new process is not feasible. Consequently, Exim shuts down an existing TLS
-session before passing the socket to a new process. The new process may then
+to a new process is not feasible. Consequently, for sending using TLS Exim
+starts an additional proxy process for handling the encryption, piping the
+unencrypted data stream from and to the delivery processes.
+
+An older mode of operation can be enabled on a per-host basis by the
+&%hosts_noproxy_tls%& option on the &(smtp)& transport. If the host matches
+this list the proxy process described above is not used; instead Exim
+shuts down an existing TLS session being run by the delivery process
+before passing the socket to a new process. The new process may then
try to start a new TLS session, and if successful, may try to re-authenticate
if AUTH is in use, before sending the next message.
.section "Certificates and all that" "SECTcerandall"
.cindex "certificate" "references to discussion"
In order to understand fully how TLS works, you need to know about
-certificates, certificate signing, and certificate authorities. This is not the
-place to give a tutorial, especially as I do not know very much about it
-myself. Some helpful introduction can be found in the FAQ for the SSL addition
-to Apache, currently at
+certificates, certificate signing, and certificate authorities.
+This is a large topic and an introductory guide is unsuitable for the Exim
+reference manual, so instead we provide pointers to existing documentation.
+
+The Apache web-server was for a long time the canonical guide, so their
+documentation is a good place to start; their SSL module's Introduction
+document is currently at
.display
-&url(http://www.modssl.org/docs/2.7/ssl_faq.html#ToC24)
+&url(https://httpd.apache.org/docs/current/ssl/ssl_intro.html)
.endd
-Other parts of the &'modssl'& documentation are also helpful, and have
-links to further files.
-Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
-0-201-61598-3), contains both introductory and more in-depth descriptions.
-Some sample programs taken from the book are available from
+and their FAQ is at
.display
-&url(http://www.rtfm.com/openssl-examples/)
+&url(https://httpd.apache.org/docs/current/ssl/ssl_faq.html)
.endd
+Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
+0-201-61598-3) in 2001, contains both introductory and more in-depth
+descriptions.
+More recently Ivan Ristić's book &'Bulletproof SSL and TLS'&,
+published by Feisty Duck (ISBN 978-1907117046) in 2013 is good.
+Ivan is the author of the popular TLS testing tools at
+&url(https://www.ssllabs.com/).
+
.section "Certificate chains" "SECID186"
The file named by &%tls_certificate%& may contain more than one
For information on creating self-signed CA certificates and using them to sign
user certificates, see the &'General implementation overview'& chapter of the
Open-source PKI book, available online at
-&url(http://ospkibook.sourceforge.net/).
+&url(https://sourceforge.net/projects/ospkibook/).
.ecindex IIDencsmtp1
.ecindex IIDencsmtp2
+.section DANE "SECDANE"
+.cindex DANE
+DNS-based Authentication of Named Entities, as applied to SMTP over TLS, provides assurance to a client that
+it is actually talking to the server it wants to rather than some attacker operating a Man In The Middle (MITM)
+operation. The latter can terminate the TLS connection you make, and make another one to the server (so both
+you and the server still think you have an encrypted connection) and, if one of the "well known" set of
+Certificate Authorities has been suborned - something which *has* been seen already (2014), a verifiable
+certificate (if you're using normal root CAs, eg. the Mozilla set, as your trust anchors).
+
+What DANE does is replace the CAs with the DNS as the trust anchor. The assurance is limited to a) the possibility
+that the DNS has been suborned, b) mistakes made by the admins of the target server. The attack surface presented
+by (a) is thought to be smaller than that of the set of root CAs.
+
+It also allows the server to declare (implicitly) that connections to it should use TLS. An MITM could simply
+fail to pass on a server's STARTTLS.
+
+DANE scales better than having to maintain (and side-channel communicate) copies of server certificates
+for every possible target server. It also scales (slightly) better than having to maintain on an SMTP
+client a copy of the standard CAs bundle. It also means not having to pay a CA for certificates.
+
+DANE requires a server operator to do three things: 1) run DNSSEC. This provides assurance to clients
+that DNS lookups they do for the server have not been tampered with. The domain MX record applying
+to this server, its A record, its TLSA record and any associated CNAME records must all be covered by
+DNSSEC.
+2) add TLSA DNS records. These say what the server certificate for a TLS connection should be.
+3) offer a server certificate, or certificate chain, in TLS connections which is is anchored by one of the TLSA records.
+
+There are no changes to Exim specific to server-side operation of DANE.
+Support for client-side operation of DANE can be included at compile time by defining SUPPORT_DANE=yes
+in &_Local/Makefile_&.
+If it has been included, the macro "_HAVE_DANE" will be defined.
+
+A TLSA record consist of 4 fields, the "Certificate Usage", the
+"Selector", the "Matching type", and the "Certificate Association Data".
+For a detailed description of the TLSA record see
+&url(https://tools.ietf.org/html/rfc7671#page-5,RFC 7671).
+
+The TLSA record for the server may have "Certificate Usage" (1st) field of DANE-TA(2) or DANE-EE(3).
+These are the "Trust Anchor" and "End Entity" variants.
+The latter specifies the End Entity directly, i.e. the certificate involved is that of the server
+(and if only DANE-EE is used then it should be the sole one transmitted during the TLS handshake);
+this is appropriate for a single system, using a self-signed certificate.
+DANE-TA usage is effectively declaring a specific CA to be used; this might be a private CA or a public,
+well-known one.
+A private CA at simplest is just a self-signed certificate (with certain
+attributes) which is used to sign server certificates, but running one securely
+does require careful arrangement.
+With DANE-TA, as implemented in Exim and commonly in other MTAs,
+the server TLS handshake must transmit the entire certificate chain from CA to server-certificate.
+DANE-TA is commonly used for several services and/or servers, each having a TLSA query-domain CNAME record,
+all of which point to a single TLSA record.
+DANE-TA and DANE-EE can both be used together.
+
+Our recommendation is to use DANE with a certificate from a public CA,
+because this enables a variety of strategies for remote clients to verify
+your certificate.
+You can then publish information both via DANE and another technology,
+"MTA-STS", described below.
+
+When you use DANE-TA to publish trust anchor information, you ask entities
+outside your administrative control to trust the Certificate Authority for
+connections to you.
+If using a private CA then you should expect others to still apply the
+technical criteria they'd use for a public CA to your certificates.
+In particular, you should probably try to follow current best practices for CA
+operation around hash algorithms and key sizes.
+Do not expect other organizations to lower their security expectations just
+because a particular profile might be reasonable for your own internal use.
+
+When this text was last updated, this in practice means to avoid use of SHA-1
+and MD5; if using RSA to use key sizes of at least 2048 bits (and no larger
+than 4096, for interoperability); to use keyUsage fields correctly; to use
+random serial numbers.
+The list of requirements is subject to change as best practices evolve.
+If you're not already using a private CA, or it doesn't meet these
+requirements, then we encourage you to avoid all these issues and use a public
+CA such as &url(https://letsencrypt.org/,Let's Encrypt) instead.
+
+The TLSA record should have a "Selector" (2nd) field of SPKI(1) and
+a "Matching Type" (3rd) field of SHA2-512(2).
+
+For the "Certificate Authority Data" (4th) field, commands like
+
+.code
+ openssl x509 -pubkey -noout <certificate.pem \
+ | openssl rsa -outform der -pubin 2>/dev/null \
+ | openssl sha512 \
+ | awk '{print $2}'
+.endd
+
+are workable to create a hash of the certificate's public key.
+
+An example TLSA record for DANE-EE(3), SPKI(1), and SHA-512 (2) looks like
+
+.code
+ _25._tcp.mail.example.com. TLSA 3 1 2 8BA8A336E...
+.endd
+
+At the time of writing, &url(https://www.huque.com/bin/gen_tlsa)
+is useful for quickly generating TLSA records.
+
+
+For use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName).
+
+The Certificate issued by the CA published in the DANE-TA model should be
+issued using a strong hash algorithm.
+Exim, and importantly various other MTAs sending to you, will not
+re-enable hash algorithms which have been disabled by default in TLS
+libraries.
+This means no MD5 and no SHA-1. SHA2-256 is the minimum for reliable
+interoperability (and probably the maximum too, in 2018).
+
+The use of OCSP-stapling should be considered, allowing for fast revocation of certificates (which would otherwise
+be limited by the DNS TTL on the TLSA records). However, this is likely to only be usable with DANE-TA. NOTE: the
+default of requesting OCSP for all hosts is modified iff DANE is in use, to:
+
+.code
+ hosts_request_ocsp = ${if or { {= {0}{$tls_out_tlsa_usage}} \
+ {= {4}{$tls_out_tlsa_usage}} } \
+ {*}{}}
+.endd
+
+The (new) variable &$tls_out_tlsa_usage$& is a bitfield with numbered bits set for TLSA record usage codes.
+The zero above means DANE was not in use, the four means that only DANE-TA usage TLSA records were
+found. If the definition of &%hosts_request_ocsp%& includes the
+string "tls_out_tlsa_usage", they are re-expanded in time to
+control the OCSP request.
+
+This modification of hosts_request_ocsp is only done if it has the default value of "*". Admins who change it, and
+those who use &%hosts_require_ocsp%&, should consider the interaction with DANE in their OCSP settings.
+
+
+For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%&
+and &%dane_require_tls_ciphers%&.
+The require variant will result in failure if the target host is not
+DNSSEC-secured. To get DNSSEC-secured hostname resolution, use
+the &%dnssec_request_domains%& router or transport option.
+
+DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
+
+A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using dnssec.
+If a TLSA lookup is done and succeeds, a DANE-verified TLS connection
+will be required for the host. If it does not, the host will not
+be used; there is no fallback to non-DANE or non-TLS.
+
+If DANE is requested and usable, then the TLS cipher list configuration
+prefers to use the option &%dane_require_tls_ciphers%& and falls
+back to &%tls_require_ciphers%& only if that is unset.
+This lets you configure "decent crypto" for DANE and "better than nothing
+crypto" as the default. Note though that while GnuTLS lets the string control
+which versions of TLS/SSL will be negotiated, OpenSSL does not and you're
+limited to ciphersuite constraints.
+
+If DANE is requested and useable (see above) the following transport options are ignored:
+.code
+ hosts_require_tls
+ tls_verify_hosts
+ tls_try_verify_hosts
+ tls_verify_certificates
+ tls_crl
+ tls_verify_cert_hostnames
+.endd
+
+If DANE is not usable, whether requested or not, and CA-anchored
+verification evaluation is wanted, the above variables should be set appropriately.
+
+The router and transport option &%dnssec_request_domains%& must not be
+set to "never" and &%dnssec_require_domains%& is ignored.
+
+If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane".
+
+There is a new variable &$tls_out_dane$& which will have "yes" if
+verification succeeded using DANE and "no" otherwise (only useful
+in combination with events; see &<<CHAPevents>>&),
+and a new variable &$tls_out_tlsa_usage$& (detailed above).
+
+.cindex DANE reporting
+An event (see &<<CHAPevents>>&) of type "dane:fail" will be raised on failures
+to achieve DANE-verified connection, if one was either requested and offered, or
+required. This is intended to support TLS-reporting as defined in
+&url(https://tools.ietf.org/html/draft-ietf-uta-smtp-tlsrpt-17).
+The &$event_data$& will be one of the Result Types defined in
+Section 4.3 of that document.
+
+Under GnuTLS, DANE is only supported from version 3.0.0 onwards.
+
+DANE is specified in published RFCs and decouples certificate authority trust
+selection from a "race to the bottom" of "you must trust everything for mail
+to get through". There is an alternative technology called MTA-STS, which
+instead publishes MX trust anchor information on an HTTPS website. At the
+time this text was last updated, MTA-STS was still a draft, not yet an RFC.
+Exim has no support for MTA-STS as a client, but Exim mail server operators
+can choose to publish information describing their TLS configuration using
+MTA-STS to let those clients who do use that protocol derive trust
+information.
+
+The MTA-STS design requires a certificate from a public Certificate Authority
+which is recognized by clients sending to you.
+That selection of which CAs are trusted by others is outside your control.
+
+The most interoperable course of action is probably to use
+&url(https://letsencrypt.org/,Let's Encrypt), with automated certificate
+renewal; to publish the anchor information in DNSSEC-secured DNS via TLSA
+records for DANE clients (such as Exim and Postfix) and to publish anchor
+information for MTA-STS as well. This is what is done for the &'exim.org'&
+domain itself (with caveats around occasionally broken MTA-STS because of
+incompatible specification changes prior to reaching RFC status).
+
+
+
. ////////////////////////////////////////////////////////////////////////////
. ////////////////////////////////////////////////////////////////////////////
.cindex "control of incoming mail"
.cindex "message" "controlling incoming"
.cindex "policy control" "access control lists"
-Access Control Lists (ACLs) are defined in a separate section of the run time
+Access Control Lists (ACLs) are defined in a separate section of the runtime
configuration file, headed by &"begin acl"&. Each ACL definition starts with a
name, terminated by a colon. Here is a complete ACL section that contains just
one very small ACL:
.section "Testing ACLs" "SECID188"
The &%-bh%& command line option provides a way of testing your ACL
configuration locally by running a fake SMTP session with which you interact.
-The host &'relay-test.mail-abuse.org'& provides a service for checking your
-relaying configuration (see section &<<SECTcheralcon>>& for more details).
-
.section "Specifying when ACLs are used" "SECID189"
session, and indeed is required to issue a new EHLO or HELO after successfully
setting up encryption following a STARTTLS command.
-.new
Note also that a deny neither forces the client to go away nor means that
mail will be refused on the connection. Consider checking for
&$sender_helo_name$& being defined in a MAIL or RCPT ACL to do that.
-.wen
If the command is accepted by an &%accept%& verb that has a &%message%&
modifier, the message may not contain more than one line (it will be truncated
the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
associated with the DATA command.
+.cindex CHUNKING "BDAT command"
+.cindex BDAT "SMTP command"
+.cindex "RFC 3030" CHUNKING
+If CHUNKING was advertised and a BDAT command sequence is received,
+the &%acl_smtp_predata%& ACL is not run.
+. XXX why not? It should be possible, for the first BDAT.
+The &%acl_smtp_data%& is run after the last BDAT command and all of
+the data specified is received.
+
For both of these ACLs, it is not possible to reject individual recipients. An
error response rejects the entire message. Unfortunately, it is known that some
MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
-For details on the operation of DKIM, see chapter &<<CHAPdkim>>&.
+For details on the operation of DKIM, see section &<<SECDKIM>>&.
.section "The SMTP MIME ACL" "SECID194"
PRDR may be used to support per-user content filtering. Without it
one must defer any recipient after the first that has a different
content-filter configuration. With PRDR, the RCPT-time check
-.new
.cindex "PRDR" "variable for"
for this can be disabled when the variable &$prdr_requested$&
is &"yes"&.
-.wen
Any required difference in behaviour of the main DATA-time
ACL should however depend on the PRDR-time ACL having run, as Exim
-will avoid doing so in some situations (e.g. single-recipient mails).
+will avoid doing so in some situations (e.g. single-recipient mails).
See also the &%prdr_enable%& global option
and the &%hosts_try_prdr%& smtp transport option.
{acl_check_rcpt} {acl_check_rcpt_submit} }
.endd
In the default configuration file there are some example settings for
-providing an RFC 4409 message submission service on port 587 and a
-non-standard &"smtps"& service on port 465. You can use a string
+providing an RFC 4409 message &"submission"& service on port 587 and
+an RFC 8314 &"submissions"& service on port 465. You can use a string
expansion like this to choose an ACL for MUAs on these ports which is
more appropriate for this purpose than the default ACL on port 25.
string, Exim searches for an ACL as follows:
.ilist
-If the string begins with a slash, Exim uses it as a file name, and reads its
+If the string begins with a slash, Exim uses it as a filename, and reads its
contents as an ACL. The lines are processed in the same way as lines in the
Exim configuration file. In particular, continuation lines are supported, blank
lines are ignored, as are lines whose first non-whitespace character is &"#"&.
remaining recipients. The &"discard"& return is not permitted for the
&%acl_smtp_predata%& ACL.
+If the ACL for VRFY returns &"accept"&, a recipient verify (without callout)
+is done on the address and the result determines the SMTP response.
+
.cindex "&[local_scan()]& function" "when all recipients discarded"
The &[local_scan()]& function is always run, even if there are no remaining
example:
.code
deny dnslists = list1.example
-dnslists = list2.example
+ dnslists = list2.example
.endd
If there are no conditions, the verb is always obeyed. Exim stops evaluating
the conditions and modifiers when it reaches a condition that fails. What
check a RCPT command:
.code
accept domains = +local_domains
-endpass
-verify = recipient
+ endpass
+ verify = recipient
.endd
If the recipient domain does not match the &%domains%& condition, control
passes to the next statement. If it does match, the recipient is verified, and
effect.
+.vitem &*queue*&&~=&~<&'text'&>
+.cindex "&%queue%& ACL modifier"
+.cindex "named queues" "selecting in ACL"
+This modifier specifies the use of a named queue for spool files
+for the message.
+It can only be used before the message is received (i.e. not in
+the DATA ACL).
+This could be used, for example, for known high-volume burst sources
+of traffic, or for quarantine of messages.
+Separate queue-runner processes will be needed for named queues.
+If the text after expansion is empty, the default queue is used.
+
+
.vitem &*remove_header*&&~=&~<&'text'&>
This modifier specifies one or more header names in a colon-separated list
that are to be removed from an incoming message, assuming, of course, that
.vitem &*udpsend*&&~=&~<&'parameters'&>
+.cindex "UDP communications"
This modifier sends a UDP packet, for purposes such as statistics
collection or behaviour monitoring. The parameters are expanded, and
the result of the expansion must be a colon-separated list consisting
is what is wanted for subsequent tests.
-.vitem &*control&~=&~cutthrough_delivery*&
+.vitem &*control&~=&~cutthrough_delivery/*&<&'options'&>
.cindex "&ACL;" "cutthrough routing"
.cindex "cutthrough" "requesting"
This option requests delivery be attempted while the item is being received.
An attempt to set this option for any recipient but the first
for a mail will be quietly ignored.
-If a recipient-verify callout connection is subsequently
+If a recipient-verify callout
+(with use_sender)
+connection is subsequently
requested in the same ACL it is held open and used for
any subsequent recipients and the data,
otherwise one is made after the initial RCPT ACL completes.
Note also that headers cannot be
modified by any of the post-data ACLs (DATA, MIME and DKIM).
Headers may be modified by routers (subject to the above) and transports.
+The &'Received-By:'& header is generated as soon as the body reception starts,
+rather than the traditional time after the full message is received;
+this will affect the timestamp.
+
+All the usual ACLs are called; if one results in the message being
+rejected, all effort spent in delivery (including the costs on
+the ultimate destination) will be wasted.
+Note that in the case of data-time ACLs this includes the entire
+message body.
Cutthrough delivery is not supported via transport-filters or when DKIM signing
of outgoing messages is done, because it sends data to the ultimate destination
before the entire message has been received from the source.
-It is not supported for messages received with the SMTP PRDR option in use.
+It is not supported for messages received with the SMTP PRDR
+or CHUNKING
+options in use.
Should the ultimate destination system positively accept or reject the mail,
a corresponding indication is given to the source system and nothing is queued.
-If there is a temporary error the item is queued for later delivery in the
-usual fashion. If the item is successfully delivered in cutthrough mode
+If the item is successfully delivered in cutthrough mode
the delivery log lines are tagged with ">>" rather than "=>" and appear
before the acceptance "<=" line.
+If there is a temporary error the item is queued for later delivery in the
+usual fashion.
+This behaviour can be adjusted by appending the option &*defer=*&<&'value'&>
+to the control; the default value is &"spool"& and the alternate value
+&"pass"& copies an SMTP defer response from the target back to the initiator
+and does not queue the message.
+Note that this is independent of any recipient verify conditions in the ACL.
+
Delivery in this mode avoids the generation of a bounce mail to a
(possibly faked)
sender when the destination system is doing content-scan based rejection.
.cindex "&ACL;" "enabling debug logging"
.cindex "debugging" "enabling from an ACL"
This control turns on debug logging, almost as though Exim had been invoked
-with &`-d`&, with the output going to a new logfile, by default called
-&'debuglog'&. The filename can be adjusted with the &'tag'& option, which
+with &`-d`&, with the output going to a new logfile in the usual logs directory,
+by default called &'debuglog'&.
+The filename can be adjusted with the &'tag'& option, which
may access any variables already defined. The logging may be adjusted with
the &'opts'& option, which takes the same values as the &`-d`& command-line
-option. Some examples (which depend on variables that don't exist in all
+option.
+Logging started this way may be stopped, and the file removed,
+with the &'kill'& option.
+Some examples (which depend on variables that don't exist in all
contexts):
.code
control = debug
control = debug/tag=.$sender_host_address
control = debug/opts=+expand+acl
control = debug/tag=.$message_exim_id/opts=+expand
+ control = debug/kill
.endd
.cindex "disable DKIM verify"
.cindex "DKIM" "disable verify"
This control turns off DKIM verification processing entirely. For details on
-the operation and configuration of DKIM, see chapter &<<CHAPdkim>>&.
+the operation and configuration of DKIM, see section &<<SECDKIM>>&.
.vitem &*control&~=&~dscp/*&<&'value'&>
&*Note:*& This control applies only to the current message, not to any others
that are being submitted at the same time using &%-bs%& or &%-bS%&.
-.new
.vitem &*control&~=&~utf8_downconvert*&
This control enables conversion of UTF-8 in message addresses
to a-label form.
-For details see &<<SECTi18nMTA>>&.
-.wen
+For details see section &<<SECTi18nMTA>>&.
.endlist vlist
RCPT ACL).
Headers will not be added to the message if the modifier is used in
-DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing.
+DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
Leading and trailing newlines are removed from
the data for the &%add_header%& modifier; if it then
with any ACL verb, including &%deny%&, though this is really not useful for
any verb that doesn't result in a delivered message.
-Headers will not be removed to the message if the modifier is used in
-DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing.
+Headers will not be removed from the message if the modifier is used in
+DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
More than one header can be removed at the same time by using a colon separated
list of header names. The header matching is case insensitive. Wildcards are
warn message = Remove internal headers
remove_header = $acl_c_ihdrs
.endd
-Removed header lines are accumulated during the MAIL, RCPT, and predata ACLs.
-They are removed from the message before processing the DATA and MIME ACLs.
-There is no harm in attempting to remove the same header twice nor is removing
+Header names for removal are accumulated during the MAIL, RCPT, and predata ACLs.
+Matching header lines are removed from the message before processing the DATA and MIME ACLs.
+If multiple header lines match, all are removed.
+There is no harm in attempting to remove the same header twice nor in removing
a non-existent header. Further header lines to be removed may be accumulated
during the DATA and MIME ACLs, after which they are removed from the message,
if present. In the case of non-SMTP messages, headers to be removed are
problems such as a syntax error or a memory shortage. For more details, see
chapter &<<CHAPexiscan>>&.
-.vitem &*demime&~=&~*&<&'extension&~list'&>
-.cindex "&%demime%& ACL condition"
-This condition is available only when Exim is compiled with the
-content-scanning extension. Its use is described in section
-&<<SECTdemimecond>>&.
-
.vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
.cindex "&%dnslists%& ACL condition"
.cindex "DNS list" "in ACL"
.cindex "&ACL;" "virus scanning"
.cindex "&ACL;" "scanning for viruses"
This condition is available only when Exim is compiled with the
-content-scanning extension. It causes the incoming message to be scanned for
+content-scanning extension
+and only after a DATA command.
+It causes the incoming message to be scanned for
viruses. For details, see chapter &<<CHAPexiscan>>&.
.vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
attempt to verify the HELO/EHLO contents, it is carried out when this
condition is encountered. See the description of the &%helo_verify_hosts%& and
&%helo_try_verify_hosts%& options for details of how to request verification
-independently of this condition.
+independently of this condition, and for detail of the verification.
For SMTP input that does not come over TCP/IP (the &%-bs%& command line
option), this condition is always true.
-.vitem &*verify&~=&~not_blind*&
+.vitem &*verify&~=&~not_blind/*&<&'options'&>
.cindex "verifying" "not blind"
.cindex "bcc recipients, verifying none"
This condition checks that there are no blind (bcc) recipients in the message.
&'Resent-Cc:'& header lines exist, they are also checked. This condition can be
used only in a DATA or non-SMTP ACL.
+.new
+There is one possible option, &`case_insensitive`&. If this is present then
+local parts are checked case-insensitively.
+.wen
+
There are, of course, many legitimate messages that make use of blind (bcc)
recipients. This check should not be used on its own for blocking messages.
.cindex "&%verify%& ACL condition"
This is a variation of the previous option, in which a modified address is
verified as a sender.
+
+Note that '/' is legal in local-parts; if the address may have such
+(eg. is generated from the received message)
+they must be protected from the options parsing by doubling:
+.code
+verify = sender=${sg{${address:$h_sender:}}{/}{//}}
+.endd
.endlist
warn message = X-Warn: sending host is on dialups list
dnslists = dialups.mail-abuse.org
.endd
-.cindex cacheing "of dns lookup"
+.cindex caching "of dns lookup"
.cindex DNS TTL
DNS list lookups are cached by Exim for the duration of the SMTP session
-.new
(but limited by the DNS return TTL value),
-.wen
so a lookup based on the IP address is done at most once for any incoming
connection (assuming long-enough TTL).
Exim does not share information between multiple incoming
connections (but your local name server cache should be active).
+There are a number of DNS lists to choose from, some commercial, some free,
+or free for small deployments. An overview can be found at
+&url(https://en.wikipedia.org/wiki/Comparison_of_DNS_blacklists).
+
.section "Specifying the IP address for a DNS list lookup" "SECID201"
.section "DNS lists keyed on domain names" "SECID202"
.cindex "DNS list" "keyed by domain name"
There are some lists that are keyed on domain names rather than inverted IP
-addresses (see for example the &'domain based zones'& link at
+addresses (see, e.g., the &'domain based zones'& link at
&url(http://www.rfc-ignorant.org/)). No reversing of components is used
with these lists. You can change the name that is looked up in a DNS list by
listing it after the domain name, introduced by a slash. For example,
and the outer dnsdb lookup finds the IP addresses for these hosts. The result
of expanding the condition might be something like this:
.code
-dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|...
+dnslists = sbl.spamhaus.org/<|192.168.2.3|192.168.5.6|...
.endd
Thus, this example checks whether or not the IP addresses of the sender
domain's mail servers are on the Spamhaus black list.
a check that the IP being tested is indeed on the first list. The first
domain is the one that is put in &$dnslist_domain$&. For example:
.code
-reject message = \
+deny message = \
rejected because $sender_host_address is blacklisted \
at $dnslist_domain\n$dnslist_text
dnslists = \
given several times, but because the results of the DNS lookups are cached,
the DNS calls themselves are not repeated. For example:
.code
-reject dnslists = \
+deny dnslists = \
http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
ACL.
Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
-specifies what Exim measures the rate of, for example messages or recipients
+specifies what Exim measures the rate of, for example, messages or recipients
or bytes. You can adjust the measurement using the &%unique=%& and/or
&%count=%& options. You can also control when Exim updates the recorded rate
using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
The &%leaky%& (default) option means that the client's recorded rate is not
updated if it is above the limit. The effect of this is that Exim measures the
-client's average rate of successfully sent email, which cannot be greater than
-the maximum allowed. If the client is over the limit it may suffer some
-counter-measures (as specified in the ACL), but it will still be able to send
-email at the configured maximum rate, whatever the rate of its attempts. This
+client's average rate of successfully sent email,
+up to the given limit.
+This is appropriate if the countermeasure when the condition is true
+consists of refusing the message, and
is generally the better choice if you have clients that retry automatically.
-For example, it does not prevent a sender with an over-aggressive retry rate
-from getting any email through.
+If the action when true is anything more complex then this option is
+likely not what is wanted.
The &%strict%& option means that the client's recorded rate is always
updated. The effect of this is that Exim measures the client's average rate
The main use of these variables is expected to be to distinguish between
rejections of MAIL and rejections of RCPT in callouts.
+The above variables may also be set after a &*successful*&
+address verification to:
+
+.ilist
+&%random%&: A random local-part callout succeeded
+.endlist
+
need to use this option unless you know that the called hosts make use of the
sender when checking recipients. If used indiscriminately, it reduces the
usefulness of callout caching.
+
+.vitem &*hold*&
+This option applies to recipient callouts only. For example:
+.code
+require verify = recipient/callout=use_sender,hold
+.endd
+It causes the connection to be held open and used for any further recipients
+and for eventual delivery (should that be done quickly).
+Doing this saves on TCP and SMTP startup costs, and TLS costs also
+when that is used for the connections.
+The advantage is only gained if there are no callout cache hits
+(which could be enforced by the no_cache option),
+if the use_sender option is used,
+if neither the random nor the use_postmaster option is used,
+and if no other callouts intervene.
.endlist
If you use any of the parameters that set a non-empty sender for the MAIL
item creates a signed address, and the &%prvscheck%& expansion item checks one.
The syntax of these expansion items is described in section
&<<SECTexpansionitems>>&.
+The validity period on signed addresses is seven days.
As an example, suppose the secret per-address keys are stored in an MySQL
database. A query to look up the key for an address could be defined as a macro
You can check the relay characteristics of your configuration in the same way
that you can test any ACL behaviour for an incoming SMTP connection, by using
the &%-bh%& option to run a fake SMTP session with which you interact.
-
-For specifically testing for unwanted relaying, the host
-&'relay-test.mail-abuse.org'& provides a useful service. If you telnet to this
-host from the host on which Exim is running, using the normal telnet port, you
-will see a normal telnet connection message and then quite a long delay. Be
-patient. The remote host is making an SMTP connection back to your host, and
-trying a number of common probes to test for open relay vulnerability. The
-results of the tests will eventually appear on your terminal.
.ecindex IIDacl
Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
.endlist
-There is another content-scanning configuration option for &_Local/Makefile_&,
-called WITH_OLD_DEMIME. If this is set, the old, deprecated &%demime%& ACL
-condition is compiled, in addition to all the other content-scanning features.
-
Content-scanning is continually evolving, and new features are still being
added. While such features are still unstable and liable to incompatible
changes, they are made available in Exim by setting options whose names begin
specialized interfaces for &"daemon"& type virus scanners, which are resident
in memory and thus are much faster.
+.new
+Since message data needs to have arrived,
+the condition may be only called in ACL defined by
+&%acl_smtp_data%&,
+&%acl_smtp_data_prdr%&,
+&%acl_smtp_mime%& or
+&%acl_smtp_dkim%&
+.wen
+
A timeout of 2 minutes is applied to a scanner call (by default);
if it expires then a defer action is taken.
If the value of &%av_scanner%& starts with a dollar character, it is expanded
before use.
The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
-The following scanner types are supported in this release:
+The following scanner types are supported in this release,
+though individual ones can be included or not at build time:
.vlist
.vitem &%avast%&
.cindex "virus scanners" "avast"
This is the scanner daemon of Avast. It has been tested with Avast Core
-Security (currently at version 1.1.7).
-You can get a trial version at &url(http://www.avast.com) or for Linux
-at &url(http://www.avast.com/linux-server-antivirus).
+Security (currently at version 2.2.0).
+You can get a trial version at &url(https://www.avast.com) or for Linux
+at &url(https://www.avast.com/linux-server-antivirus).
This scanner type takes one option,
which can be either a full path to a UNIX socket,
or host and port specifiers separated by white space.
The host may be a name or an IP address; the port is either a
single number or a pair of numbers with a dash between.
-Any further options are given, on separate lines,
-to the daemon as options before the main scan command.
+A list of options may follow. These options are interpreted on the
+Exim's side of the malware scanner, or are given on separate lines to
+the daemon as options before the main scan command.
+
+.cindex &`pass_unscanned`& "avast"
+If &`pass_unscanned`&
+is set, any files the Avast scanner can't scan (e.g.
+decompression bombs, or invalid archives) are considered clean. Use with
+care.
+
For example:
.code
av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
+av_scanner = avast:/var/run/avast/scan.sock:pass_unscanned:FLAGS -fullfiles:SENSITIVITY -pup
av_scanner = avast:192.168.2.22 5036
.endd
If you omit the argument, the default path
PACK
.endd
+If the scanner returns a temporary failure (e.g. license issues, or
+permission problems), the message is deferred and a paniclog entry is
+written. The usual &`defer_ok`& option is available.
.vitem &%aveserver%&
.cindex "virus scanners" "Kaspersky"
This is the scanner daemon of Kaspersky Version 5. You can get a trial version
-at &url(http://www.kaspersky.com). This scanner type takes one option,
+at &url(https://www.kaspersky.com/). This scanner type takes one option,
which is the path to the daemon's UNIX socket. The default is shown in this
example:
.code
.vitem &%clamd%&
.cindex "virus scanners" "clamd"
This daemon-type scanner is GPL and free. You can get it at
-&url(http://www.clamav.net/). Some older versions of clamd do not seem to
+&url(https://www.clamav.net/). Some older versions of clamd do not seem to
unpack MIME containers, so it used to be recommended to unpack MIME attachments
in the MIME ACL. This is no longer believed to be necessary.
If the value of av_scanner points to a UNIX socket file or contains the
&`local`&
option, then the ClamAV interface will pass a filename containing the data
-to be scanned, which will should normally result in less I/O happening and be
+to be scanned, which should normally result in less I/O happening and be
more efficient. Normally in the TCP case, the data is streamed to ClamAV as
Exim does not assume that there is a common filesystem with the remote host.
-There is an option WITH_OLD_CLAMAV_STREAM in &_src/EDITME_& available, should
-you be running a version of ClamAV prior to 0.95.
The final example shows that multiple TCP targets can be specified. Exim will
randomly use one for each incoming email (i.e. it load balances them). Note
.endd
.vitem &%drweb%&
.cindex "virus scanners" "DrWeb"
-The DrWeb daemon scanner (&url(http://www.sald.com/)) interface
+The DrWeb daemon scanner (&url(https://www.sald.ru/)) interface
takes one option,
either a full path to a UNIX socket,
or host and port specifiers separated by white space.
.code
av_scanner = f-protd:localhost 10200-10204
.endd
+If you omit the argument, the default values shown above are used.
+
+.vitem &%f-prot6d%&
+.cindex "virus scanners" "f-prot6d"
+The f-prot6d scanner is accessed using the FPSCAND protocol over TCP.
+One argument is taken, being a space-separated hostname and port number.
+For example:
+.code
+av_scanner = f-prot6d:localhost 10200
+.endd
If you omit the argument, the default values show above are used.
.vitem &%fsecure%&
.cindex "virus scanners" "F-Secure"
-The F-Secure daemon scanner (&url(http://www.f-secure.com)) takes one
+The F-Secure daemon scanner (&url(https://www.f-secure.com/)) takes one
argument which is the path to a UNIX socket. For example:
.code
av_scanner = fsecure:/path/to/.fsav
.vitem &%mksd%&
.cindex "virus scanners" "mksd"
-This is a daemon type scanner that is aimed mainly at Polish users, though some
-parts of documentation are now available in English. You can get it at
-&url(http://linux.mks.com.pl/). The only option for this scanner type is
+This was a daemon type scanner that is aimed mainly at Polish users,
+though some documentation was available in English.
+The history can be shown at &url(https://en.wikipedia.org/wiki/Mks_vir)
+and this appears to be a candidate for removal from Exim, unless
+we are informed of other virus scanners which use the same protocol
+to integrate.
+The only option for this scanner type is
the maximum number of processes used simultaneously to scan the attachments,
-provided that the demime facility is employed and also provided that mksd has
+provided that mksd has
been run with at least the same number of child processes. For example:
.code
av_scanner = mksd:2
a commandline to send (may include a single %s which will be replaced with
the path to the mail file to be scanned),
an RE to trigger on from the returned data,
-an RE to extract malware_name from the returned data.
+and an RE to extract malware_name from the returned data.
For example:
.code
-av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)\$
+av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)$
.endd
-Default for the socket specifier is &_/tmp/malware.sock_&.
-Default for the commandline is &_%s\n_&.
-Both regular-expressions are required.
+Note that surrounding whitespace is stripped from each option, meaning
+there is no way to specify a trailing newline.
+The socket specifier and both regular-expressions are required.
+Default for the commandline is &_%s\n_& (note this does have a trailing newline);
+specify an empty element to get this.
.vitem &%sophie%&
.cindex "virus scanners" "Sophos and Sophie"
Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
-You can get Sophie at &url(http://www.clanfield.info/sophie/). The only option
+You can get Sophie at &url(http://sophie.sourceforge.net/). The only option
for this scanner type is the path to the UNIX socket that Sophie uses for
client communication. For example:
.code
condition succeeds if a virus is found and its name matches the regular
expression. This allows you to take special actions on certain types of virus.
Note that &"/"& characters in the RE must be doubled due to the list-processing,
-unless the separator is changed (in the usual way).
+unless the separator is changed (in the usual way &<<SECTlistsepchange>>&).
.endlist
You can append a &`defer_ok`& element to the &%malware%& argument list to accept
&%message%& modifier that specifies the error returned to the sender, and/or in
logging data.
-If your virus scanner cannot unpack MIME and TNEF containers itself, you should
-use the &%demime%& condition (see section &<<SECTdemimecond>>&) before the
-&%malware%& condition.
-
Beware the interaction of Exim's &%message_size_limit%& with any size limits
imposed by your anti-virus scanner.
Here is a very simple scanning example:
.code
deny message = This message contains malware ($malware_name)
- demime = *
malware = *
.endd
The next example accepts messages when there is a problem with the scanner:
.code
deny message = This message contains malware ($malware_name)
- demime = *
malware = */defer_ok
.endd
The next example shows how to use an ACL variable to scan with both sophie and
For more information about installation and configuration of SpamAssassin or
Rspamd refer to their respective websites at
-&url(http://spamassassin.apache.org) and &url(http://www.rspamd.com)
+&url(https://spamassassin.apache.org/) and &url(https://www.rspamd.com/)
SpamAssassin can be installed with CPAN by running:
.code
you must set the &%spamd_address%& option in the global part of the Exim
configuration as follows (example):
.code
-spamd_address = 192.168.99.45 387
+spamd_address = 192.168.99.45 783
.endd
+The SpamAssassin protocol relies on a TCP half-close from the client.
+If your SpamAssassin client side is running a Linux system with an
+iptables firewall, consider setting
+&%net.netfilter.nf_conntrack_tcp_timeout_close_wait%& to at least the
+timeout, Exim uses when waiting for a response from the SpamAssassin
+server (currently defaulting to 120s). With a lower value the Linux
+connection tracking may consider your half-closed connection as dead too
+soon.
+
To use Rspamd (which by default listens on all local addresses
on TCP port 11333)
As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
sockets. If you want to us these, supply &%spamd_address%& with an absolute
-file name instead of an address/port pair:
+filename instead of an address/port pair:
.code
spamd_address = /var/run/spamd_socket
.endd
You can have multiple &%spamd%& servers to improve scalability. These can
reside on other hardware reachable over the network. To specify multiple
&%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
-option, separated with colons (the separator can be changed in the usual way):
+option, separated with colons (the separator can be changed in the usual way &<<SECTlistsepchange>>&):
.code
spamd_address = 192.168.2.10 783 : \
192.168.2.11 783 : \
Unix and TCP socket specifications may be mixed in any order.
Each element of the list is a list itself, space-separated by default
-and changeable in the usual way.
+and changeable in the usual way (&<<SECTlistsepchange>>&);
+take care to not double the separator.
For TCP socket specifications a host name or IP (v4 or v6, but
subject to list-separator quoting rules) address can be used,
.vlist
.vitem &$spam_score$&
-The spam score of the message, for example &"3.4"& or &"30.5"&. This is useful
+The spam score of the message, for example, &"3.4"& or &"30.5"&. This is useful
for inclusion in log or reject messages.
.vitem &$spam_score_int$&
A multiline text table, containing the full SpamAssassin report for the
message. Useful for inclusion in headers or reject messages.
This variable is only usable in a DATA-time ACL.
+Beware that SpamAssassin may return non-ASCII characters, especially
+when running in country-specific locales, which are not legal
+unencoded in headers.
.vitem &$spam_action$&
For SpamAssassin either 'reject' or 'no action' depending on the
.next
The string &"default"&. In that case, the file is put in the temporary
&"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
-a sequential file name consisting of the message id and a sequence number. The
+a sequential filename consisting of the message id and a sequence number. The
full path and name is available in &$mime_decoded_filename$& after decoding.
.next
A full path name starting with a slash. If the full name is an existing
directory, it is used as a replacement for the default directory. The filename
is then sequentially assigned. If the path does not exist, it is used as
-the full path and file name.
+the full path and filename.
.next
If the string does not start with a slash, it is used as the
filename, and the default path is then used.
.vitem &$mime_decoded_filename$&
This variable is set only after the &%decode%& modifier (see above) has been
-successfully run. It contains the full path and file name of the file
+successfully run. It contains the full path and filename of the file
containing the decoded data.
.endlist
As an example, the following will ban &"HTML mail"& (including that sent with
alternative plain text), while allowing HTML files to be attached. HTML
-coverletter mail attached to non-HMTL coverletter mail will also be allowed:
+coverletter mail attached to non-HTML coverletter mail will also be allowed:
.code
deny message = HTML mail is not accepted here
!condition = $mime_is_rfc822
.endd
.vitem &$mime_is_multipart$&
This variable has the value 1 (true) when the current part has the main type
-&"multipart"&, for example &"multipart/alternative"& or &"multipart/mixed"&.
+&"multipart"&, for example, &"multipart/alternative"& or &"multipart/mixed"&.
Since multipart entities only serve as containers for other parts, you may not
want to carry out specific actions on them.
&*Warning*&: With large messages, these conditions can be fairly
CPU-intensive.
-
-
-
-.section "The demime condition" "SECTdemimecond"
-.cindex "content scanning" "MIME checking"
-.cindex "MIME content scanning"
-The &%demime%& ACL condition provides MIME unpacking, sanity checking and file
-extension blocking. It is usable only in the DATA and non-SMTP ACLs. The
-&%demime%& condition uses a simpler interface to MIME decoding than the MIME
-ACL functionality, but provides no additional facilities. Please note that this
-condition is deprecated and kept only for backward compatibility. You must set
-the WITH_OLD_DEMIME option in &_Local/Makefile_& at build time to be able to
-use the &%demime%& condition.
-
-The &%demime%& condition unpacks MIME containers in the message. It detects
-errors in MIME containers and can match file extensions found in the message
-against a list. Using this facility produces files containing the unpacked MIME
-parts of the message in the temporary scan directory. If you do antivirus
-scanning, it is recommended that you use the &%demime%& condition before the
-antivirus (&%malware%&) condition.
-
-On the right-hand side of the &%demime%& condition you can pass a
-colon-separated list of file extensions that it should match against. For
-example:
-.code
-deny message = Found blacklisted file attachment
- demime = vbs:com:bat:pif:prf:lnk
-.endd
-If one of the file extensions is found, the condition is true, otherwise it is
-false. If there is a temporary error while demimeing (for example, &"disk
-full"&), the condition defers, and the message is temporarily rejected (unless
-the condition is on a &%warn%& verb).
-
-The right-hand side is expanded before being treated as a list, so you can have
-conditions and lookups there. If it expands to an empty string, &"false"&, or
-zero (&"0"&), no demimeing is done and the condition is false.
-
-The &%demime%& condition set the following variables:
-
-.vlist
-.vitem &$demime_errorlevel$&
-.vindex "&$demime_errorlevel$&"
-When an error is detected in a MIME container, this variable contains the
-severity of the error, as an integer number. The higher the value, the more
-severe the error (the current maximum value is 3). If this variable is unset or
-zero, no error occurred.
-
-.vitem &$demime_reason$&
-.vindex "&$demime_reason$&"
-When &$demime_errorlevel$& is greater than zero, this variable contains a
-human-readable text string describing the MIME error that occurred.
-.endlist
-
-.vlist
-.vitem &$found_extension$&
-.vindex "&$found_extension$&"
-When the &%demime%& condition is true, this variable contains the file
-extension it found.
-.endlist
-
-Both &$demime_errorlevel$& and &$demime_reason$& are set by the first call of
-the &%demime%& condition, and are not changed on subsequent calls.
-
-If you do not want to check for file extensions, but rather use the &%demime%&
-condition for unpacking or error checking purposes, pass &"*"& as the
-right-hand side value. Here is a more elaborate example of how to use this
-facility:
-.code
-# Reject messages with serious MIME container errors
-deny message = Found MIME error ($demime_reason).
- demime = *
- condition = ${if >{$demime_errorlevel}{2}{1}{0}}
-
-# Reject known virus spreading file extensions.
-# Accepting these is pretty much braindead.
-deny message = contains $found_extension file (blacklisted).
- demime = com:vbs:bat:pif:scr
-
-# Freeze .exe and .doc files. Postmaster can
-# examine them and eventually thaw them.
-deny log_message = Another $found_extension file.
- demime = exe:doc
- control = freeze
-.endd
.ecindex IIDcosca
.section "Building Exim to use a local scan function" "SECID207"
.cindex "&[local_scan()]& function" "building Exim to use"
To make use of the local scan function feature, you must tell Exim where your
-function is before building Exim, by setting LOCAL_SCAN_SOURCE in your
+function is before building Exim, by setting
+both HAVE_LOCAL_SCAN and
+LOCAL_SCAN_SOURCE in your
&_Local/Makefile_&. A recommended place to put it is in the &_Local_&
directory, so you might set
.code
+HAVE_LOCAL_SCAN=yes
LOCAL_SCAN_SOURCE=Local/local_scan.c
.endd
for example. The function must be called &[local_scan()]&. It is called by
commented template function (that just accepts the message) in the file
_src/local_scan.c_.
-If you want to make use of Exim's run time configuration file to set options
+If you want to make use of Exim's runtime configuration file to set options
for your &[local_scan()]& function, you must also set
.code
LOCAL_SCAN_HAS_OPTIONS=yes
.section "API for local_scan()" "SECTapiforloc"
.cindex "&[local_scan()]& function" "API description"
+.cindex &%dlfunc%& "API description"
You must include this line near the start of your code:
.code
#include "local_scan.h"
.vlist
.vitem &*int&~body_linecount*&
This variable contains the number of lines in the message's body.
+It is not valid if the &%spool_files_wireformat%& option is used.
.vitem &*int&~body_zerocount*&
This variable contains the number of binary zero bytes in the message's body.
+It is not valid if the &%spool_files_wireformat%& option is used.
.vitem &*unsigned&~int&~debug_selector*&
This variable is set to zero when no debugging is taking place. Otherwise, it
.section "Setting an errors address in a system filter" "SECID217"
+.cindex "envelope from"
.cindex "envelope sender"
In a system filter, if a &%deliver%& command is followed by
.code
.cindex "sender" "address"
.oindex "&%uucp_from_pattern%&"
.oindex "&%uucp_from_sender%&"
+.cindex "envelope from"
.cindex "envelope sender"
.cindex "Sendmail compatibility" "&""From""& line"
Messages that have come from UUCP (and some other applications) often begin
.section "Resent- header lines" "SECID220"
.cindex "&%Resent-%& header lines"
+.cindex "header lines" "Resent-"
RFC 2822 makes provision for sets of header lines starting with the string
&`Resent-`& to be added to a message when it is resent by the original
recipient to somebody else. These headers are &'Resent-Date:'&,
.section "The Date: header line" "SECID223"
.cindex "&'Date:'& header line"
+.cindex "header lines" "Date:"
If a locally-generated or submission-mode message has no &'Date:'& header line,
Exim adds one, using the current date and time, unless the
&%suppress_local_fixups%& control has been specified.
.section "The Envelope-to: header line" "SECID225"
.cindex "&'Envelope-to:'& header line"
+.cindex "header lines" "Envelope-to:"
.oindex "&%envelope_to_remove%&"
&'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
Exim can be configured to add them to the final delivery of messages. (See the
.section "The From: header line" "SECTthefrohea"
.cindex "&'From:'& header line"
+.cindex "header lines" "From:"
.cindex "Sendmail compatibility" "&""From""& line"
.cindex "message" "submission"
.cindex "submission mode"
.section "The Message-ID: header line" "SECID226"
.cindex "&'Message-ID:'& header line"
+.cindex "header lines" "Message-ID:"
.cindex "message" "submission"
.oindex "&%message_id_header_text%&"
If a locally-generated or submission-mode incoming message does not contain a
.section "The Received: header line" "SECID227"
.cindex "&'Received:'& header line"
+.cindex "header lines" "Received:"
A &'Received:'& header line is added at the start of every message. The
contents are defined by the &%received_header_text%& configuration option, and
Exim automatically adds a semicolon and a timestamp to the configured string.
.section "The References: header line" "SECID228"
.cindex "&'References:'& header line"
+.cindex "header lines" "References:"
Messages created by the &(autoreply)& transport include a &'References:'&
header line. This is constructed according to the rules that are described in
section 3.64 of RFC 2822 (which states that replies should contain such a
.section "The Return-path: header line" "SECID229"
.cindex "&'Return-path:'& header line"
+.cindex "header lines" "Return-path:"
.oindex "&%return_path_remove%&"
&'Return-path:'& header lines are defined as something an MTA may insert when
it does the final delivery of messages. (See the generic &%return_path_add%&
.section "The Sender: header line" "SECTthesenhea"
.cindex "&'Sender:'& header line"
.cindex "message" "submission"
+.cindex "header lines" "Sender:"
For a locally-originated message from an untrusted user, Exim may remove an
existing &'Sender:'& header line, and it may add a new one. You can modify
these actions by setting the &%local_sender_retain%& option true, the
When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
appropriate) in order to decide whether the command should be accepted or not.
-If no ACL is defined, the command is rejected.
.cindex "VRFY" "processing"
+When no ACL is defined for VRFY, or if it rejects without
+setting an explicit response code, the command is accepted
+(with a 252 SMTP response code)
+in order to support awkward clients that do a VRFY before every RCPT.
When VRFY is accepted, it runs exactly the same code as when Exim is
-called with the &%-bv%& option.
+called with the &%-bv%& option, and returns 250/451/550
+SMTP response codes.
.cindex "EXPN" "processing"
+If no ACL for EXPN is defined, the command is rejected.
When EXPN is accepted, a single-level expansion of the address is done.
EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
than a verification (the &%-bv%& option). If an unqualified local part is given
.chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
"Customizing messages"
-When a message fails to be delivered, or remains on the queue for more than a
+When a message fails to be delivered, or remains in the queue for more than a
configured amount of time, Exim sends a message to the original sender, or
to an alternative configured address. The text of these messages is built into
the code of Exim, but it is possible to change it, either by adding a single
<$sender_address>
}}has not been delivered to all of its recipients after
-more than $warn_message_delay on the queue on $primary_hostname.
+more than $warn_message_delay in the queue on $primary_hostname.
The message identifier is: $message_exim_id
The subject of the message is: $h_subject
routers are tried, and so the whole delivery fails.
The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
-expanded into a file name or a pipe delivery, which is usually inappropriate in
+expanded into a filename or a pipe delivery, which is usually inappropriate in
a mailing list.
.oindex "&%errors_to%&"
.section "Variable Envelope Return Paths (VERP)" "SECTverp"
.cindex "VERP"
.cindex "Variable Envelope Return Paths"
+.cindex "envelope from"
.cindex "envelope sender"
-Variable Envelope Return Paths &-- see &url(http://cr.yp.to/proto/verp.txt) &--
+Variable Envelope Return Paths &-- see &url(https://cr.yp.to/proto/verp.txt) &--
are a way of helping mailing list administrators discover which subscription
address is the cause of a particular delivery failure. The idea is to encode
the original recipient address in the outgoing envelope sender address, so that
setting ensures that if the lookup fails (leading to &%data%& being an empty
string), Exim gives up on the address without trying any subsequent routers.
-This one router can handle all the virtual domains because the alias file names
+This one router can handle all the virtual domains because the alias filenames
follow a fixed pattern. Permissions can be arranged so that appropriate people
can edit the different alias files. A successful aliasing operation results in
a new envelope recipient address, which is then routed from scratch.
.section "Exim on the upstream server host" "SECID247"
It is tempting to arrange for incoming mail for the intermittently connected
-host to remain on Exim's queue until the client connects. However, this
+host to remain in Exim's queue until the client connects. However, this
approach does not scale very well. Two different kinds of waiting message are
being mixed up in the same queue &-- those that cannot be delivered because of
some temporary problem, and those that are waiting for their destination host
Linux this has been seen to make syslog take 90% plus of CPU time.
The destination for Exim's logs is configured by setting LOG_FILE_PATH in
-&_Local/Makefile_& or by setting &%log_file_path%& in the run time
+&_Local/Makefile_& or by setting &%log_file_path%& in the runtime
configuration. This latter string is expanded, so it can contain, for example,
references to the host name:
.code
log_file_path = /var/log/$primary_hostname/exim_%slog
.endd
It is generally advisable, however, to set the string in &_Local/Makefile_&
-rather than at run time, because then the setting is available right from the
+rather than at runtime, because then the setting is available right from the
start of Exim's execution. Otherwise, if there's something it wants to log
before it has read the configuration file (for example, an error in the
configuration file) it will not use the path you want, and may not be able to
.code
log_file_path = $spool_directory/log/%slog
.endd
-If you do not specify anything at build time or run time,
-or if you unset the option at run time (i.e. &`log_file_path = `&),
+If you do not specify anything at build time or runtime,
+or if you unset the option at runtime (i.e. &`log_file_path = `&),
that is where the logs are written.
-A log file path may also contain &`%D`& or &`%M`& if datestamped log file names
+A log file path may also contain &`%D`& or &`%M`& if datestamped log filenames
are in use &-- see section &<<SECTdatlogfil>>& below.
Here are some examples of possible settings:
timestamp. The flags are:
.display
&`<=`& message arrival
+&`(=`& message fakereject
&`=>`& normal message delivery
&`->`& additional address in same delivery
&`>>`& cutthrough message delivery
flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
down a single SMTP connection, an asterisk follows the IP address in the log
lines for the second and subsequent messages.
+When two or more messages are delivered down a single TLS connection, the
+DNS and some TLS-related information logged for the first message delivered
+will not be present in the log lines for the second and subsequent messages.
+TLS cipher information is still available.
.cindex "delivery" "cutthrough; logging"
.cindex "cutthrough" "logging"
&` `& command list for &"no mail in SMTP session"&
&`CV `& certificate verification status
&`D `& duration of &"no mail in SMTP session"&
+&`DKIM`& domain verified in incoming message
&`DN `& distinguished name from peer certificate
+&`DS `& DNSSEC secured lookups
&`DT `& on &`=>`& lines: time taken for a delivery
&`F `& sender address (on delivery lines)
&`H `& host name and IP address
&`I `& local interface used
-&`id `& message id for incoming message
+&`id `& message id (from header) for incoming message
+&`K `& CHUNKING extension used
+&`L `& on &`<=`& and &`=>`& lines: PIPELINING extension used
+&`M8S `& 8BITMIME status for incoming message
&`P `& on &`<=`& lines: protocol used
&` `& on &`=>`& and &`**`& lines: return path
-&`PRX `& on &'<='& and&`=>`& lines: proxy address
+&`PRDR`& PRDR extension used
+&`PRX `& on &`<=`& and &`=>`& lines: proxy address
+&`Q `& alternate queue name
&`QT `& on &`=>`& lines: time spent on queue so far
&` `& on &"Completed"& lines: time spent on queue
&`R `& on &`<=`& lines: reference for local bounce
-&` `& on &`=>`& &`**`& and &`==`& lines: router name
-&`S `& size of message
+&` `& on &`=>`& &`>>`& &`**`& and &`==`& lines: router name
+&`RT `& on &`<=`& lines: time taken for reception
+&`S `& size of message in bytes
&`SNI `& server name indication from TLS client hello
&`ST `& shadow transport name
&`T `& on &`<=`& lines: message subject (topic)
+&`TFO `& connection took advantage of TCP Fast Open
&` `& on &`=>`& &`**`& and &`==`& lines: transport name
&`U `& local user or RFC 1413 identity
&`X `& TLS cipher suite
.endd
failed. The delivery was discarded.
.endlist olist
+.next
+.cindex DKIM "log line"
+&'DKIM: d='&&~&~Verbose results of a DKIM verification attempt, if enabled for
+logging and the message has a DKIM signature header.
.endlist ilist
&`*delay_delivery `& immediate delivery delayed
&` deliver_time `& time taken to perform delivery
&` delivery_size `& add &`S=`&&'nnn'& to => lines
+&`*dkim `& DKIM verified domain on <= lines
+&` dkim_verbose `& separate full DKIM verification result line, per signature
&`*dnslist_defer `& defers of DNS list (aka RBL) lookups
+&` dnssec `& DNSSEC secured lookups
&`*etrn `& ETRN commands
&`*host_lookup_failed `& as it says
&` ident_timeout `& timeout for ident connection
&` incoming_interface `& local interface on <= and => lines
&` incoming_port `& remote port on <= lines
&`*lost_incoming_connection `& as it says (includes timeouts)
-.new
+&` millisec `& millisecond timestamps and RT,QT,DT,D times
+&`*msg_id `& on <= lines, Message-ID: header value
+&` msg_id_created `& on <= lines, Message-ID: header value when one had to be added
&` outgoing_interface `& local interface on => lines
-.wen
&` outgoing_port `& add remote port to => lines
&`*queue_run `& start and end queue runs
&` queue_time `& time on queue for one recipient
&` queue_time_overall `& time on queue for whole message
&` pid `& Exim process id
-.new
+&` pipelining `& PIPELINING use, on <= and => lines
&` proxy `& proxy address on <= and => lines
-.wen
+&` receive_time `& time taken to receive message
&` received_recipients `& recipients on <= lines
&` received_sender `& sender on <= lines
&`*rejected_header `& header contents on reject log
.cindex "log" "delivery duration"
&%deliver_time%&: For each delivery, the amount of real time it has taken to
perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
+If millisecond logging is enabled, short times will be shown with greater
+precision, eg. &`DT=0.304s`&.
.next
.cindex "log" "message size on delivery"
.cindex "size" "of message"
&%delivery_size%&: For each delivery, the size of message delivered is added to
the &"=>"& line, tagged with S=.
.next
+.cindex log "DKIM verification"
+.cindex DKIM "verification logging"
+&%dkim%&: For message acceptance log lines, when an DKIM signature in the header
+verifies successfully a tag of DKIM is added, with one of the verified domains.
+.next
+.cindex log "DKIM verification"
+.cindex DKIM "verification logging"
+&%dkim_verbose%&: A log entry is written for each attempted DKIM verification.
+.next
.cindex "log" "dnslist defer"
.cindex "DNS list" "logging defer"
.cindex "black list (DNS)"
&%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
DNS black list suffers a temporary error.
.next
+.cindex log dnssec
+.cindex dnssec logging
+&%dnssec%&: For message acceptance and (attempted) delivery log lines, when
+dns lookups gave secure results a tag of DS is added.
+For acceptance this covers the reverse and forward lookups for host name verification.
+It does not cover helo-name verification.
+For delivery this covers the SRV, MX, A and/or AAAA lookups.
+.next
.cindex "log" "ETRN commands"
.cindex "ETRN" "logging"
&%etrn%&: Every valid ETRN command that is received is logged, before the ACL
&%incoming_interface%&: The interface on which a message was received is added
to the &"<="& line as an IP address in square brackets, tagged by I= and
followed by a colon and the port number. The local interface and port are also
-added to other SMTP log lines, for example &"SMTP connection from"&, to
+added to other SMTP log lines, for example, &"SMTP connection from"&, to
rejection lines, and (despite the name) to outgoing &"=>"& and &"->"& lines.
-.new
The latter can be disabled by turning off the &%outgoing_interface%& option.
-.wen
.next
-.new
.cindex log "incoming proxy address"
.cindex proxy "logging proxy address"
.cindex "TCP/IP" "logging proxy address"
&%proxy%&: The internal (closest to the system running Exim) IP address
of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
on a proxied connection
-or the &"=>"& line for a message delivered on a proxied connection..
+or the &"=>"& line for a message delivered on a proxied connection.
See &<<SECTproxyInbound>>& for more information.
-.wen
.next
.cindex "log" "incoming remote port"
.cindex "port" "logging remote"
&%lost_incoming_connection%&: A log line is written when an incoming SMTP
connection is unexpectedly dropped.
.next
+.cindex "log" "millisecond timestamps"
+.cindex millisecond logging
+.cindex timestamps "millisecond, in logs"
+&%millisec%&: Timestamps have a period and three decimal places of finer granularity
+appended to the seconds value.
+.next
+.new
+.cindex "log" "message id"
+&%msg_id%&: The value of the Message-ID: header.
+.next
+&%msg_id_created%&: The value of the Message-ID: header, when one had to be created.
+This will be either because the message is a bounce, or was submitted locally
+(submission mode) without one.
+The field identifier will have an asterix appended: &"id*="&.
+.wen
+.next
.cindex "log" "outgoing interface"
.cindex "log" "local interface"
.cindex "log" "local address and port"
.cindex "TCP/IP" "logging local address and port"
.cindex "interface" "logging"
-.new
&%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
interface on which a message was sent is added to delivery lines as an I= tag
followed by IP address in square brackets. You can disable this by turning
off the &%outgoing_interface%& option.
-.wen
.next
.cindex "log" "outgoing remote port"
-.cindex "port" "logging outgoint remote"
-.cindex "TCP/IP" "logging ougtoing remote port"
+.cindex "port" "logging outgoing remote"
+.cindex "TCP/IP" "logging outgoing remote port"
&%outgoing_port%&: The remote port number is added to delivery log lines (those
containing => tags) following the IP address.
-.new
The local port is also added if &%incoming_interface%& and
&%outgoing_interface%& are both enabled.
-.wen
This option is not included in the default setting, because for most ordinary
configurations, the remote port number is always 25 (the SMTP port), and the
local port is a random ephemeral port.
.cindex "pid (process id)" "in log lines"
&%pid%&: The current process id is added to every log line, in square brackets,
immediately after the time and date.
+.next
+.cindex log pipelining
+.cindex pipelining "logging outgoing"
+&%pipelining%&: A field is added to delivery and accept
+log lines when the ESMTP PIPELINING extension was used.
+The field is a single "L".
+
+On accept lines, where PIPELINING was offered but not used by the client,
+the field has a minus appended.
+
+.new
+.cindex "pipelining" "early connection"
+If Exim is built with the SUPPORT_PIPE_CONNECT build option
+accept "L" fields have a period appended if the feature was
+offered but not used, or an asterisk appended if used.
+Delivery "L" fields have an asterisk appended if used.
+.wen
+
.next
.cindex "log" "queue run"
.cindex "queue runner" "logging"
This means that it may be longer than the difference between the arrival and
delivery log line times, because the arrival log line is not written until the
message has been successfully received.
+If millisecond logging is enabled, short times will be shown with greater
+precision, eg. &`QT=1.578s`&.
.next
&%queue_time_overall%&: The amount of time the message has been in the queue on
the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
message, so it includes reception time as well as the total delivery time.
.next
+.cindex "log" "receive duration"
+&%receive_time%&: For each message, the amount of real time it has taken to
+perform the reception is logged as RT=<&'time'&>, for example, &`RT=1s`&.
+If millisecond logging is enabled, short times will be shown with greater
+precision, eg. &`RT=0.204s`&.
+.next
.cindex "log" "recipients"
&%received_recipients%&: The recipients of a message are listed in the main log
as soon as the message is received. The list appears at the end of the log line
unchanged, or whether they should be rendered as escape sequences.
.next
.cindex "log" "certificate verification"
+.cindex log DANE
+.cindex DANE logging
&%tls_certificate_verified%&: An extra item is added to <= and => log lines
when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
-verified, and &`CV=no`& if not.
+verified
+using a CA trust anchor,
+&`CA=dane`& if using a DNS trust anchor,
+and &`CV=no`& if not.
.next
.cindex "log" "TLS cipher"
.cindex "TLS" "logging cipher"
Another utility that might be of use to sites with many MTAs is Tom Kistner's
&'exilog'&. It provides log visualizations across multiple Exim servers. See
-&url(http://duncanthrax.net/exilog/) for details.
+&url(https://duncanthrax.net/exilog/) for details.
.vitem &*-x*&
Match only non-frozen messages.
+
+.new
+.vitem &*-G*&&~<&'queuename'&>
+Match only messages in the given queue. Without this, the default queue is searched.
+.wen
.endlist
The following options control the format of the output:
.cindex "&'exiqsumm'&"
.cindex "queue" "summary"
The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
--bp`& and produces a summary of the messages on the queue. Thus, you use it by
+-bp`& and produces a summary of the messages in the queue. Thus, you use it by
running a command such as
.code
exim -bp | exiqsumm
.display
&`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
.endd
-If no log file names are given on the command line, the standard input is read.
+If no log filenames are given on the command line, the standard input is read.
The &%-t%& argument specifies a number of seconds. It adds an additional
condition for message selection. Messages that are complete are shown only if
-they spent more than <&'n'&> seconds on the queue.
+they spent more than <&'n'&> seconds in the queue.
By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
makes it case-sensitive. This may give a performance improvement when searching
.cindex "&'exipick'&"
John Jetmore's &'exipick'& utility is included in the Exim distribution. It
lists messages from the queue according to a variety of criteria. For details
-of &'exipick'&'s facilities, visit the web page at
-&url(http://www.exim.org/eximwiki/ToolExipickManPage) or run &'exipick'& with
+of &'exipick'&'s facilities, run &'exipick'& with
the &%--help%& option.
configuration.
.endlist
-Each time &'exicyclog'& is run the file names get &"shuffled down"& by one. If
-the main log file name is &_mainlog_& (the default) then when &'exicyclog'& is
+Each time &'exicyclog'& is run the filenames get &"shuffled down"& by one. If
+the main log filename is &_mainlog_& (the default) then when &'exicyclog'& is
run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
&_mainlog.02_& and so on, up to the limit that is set in the script or by the
&%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
.cindex "&'eximstats'&"
A Perl script called &'eximstats'& is provided for extracting statistical
information from log files. The output is either plain text, or HTML.
-Exim log files are also supported by the &'Lire'& system produced by the
-LogReport Foundation &url(http://www.logreport.org).
+. --- 2018-09-07: LogReport's Lire appears to be dead; website is a Yahoo Japan
+. --- 404 error and everything else points to that.
The &'eximstats'& script has been hacked about quite a bit over time. The
latest version is the result of some extensive revision by Steve Campbell. A
The remainder of the output is in sections that can be independently disabled
or modified by various options. It consists of a summary of deliveries by
transport, histograms of messages received and delivered per time interval
-(default per hour), information about the time messages spent on the queue,
+(default per hour), information about the time messages spent in the queue,
a list of relayed messages, lists of the top fifty sending hosts, local
senders, destination hosts, and destination local users by count and by volume,
and a list of delivery errors that occurred.
.cindex "USE_DB"
If the native DB interface is in use (USE_DB is set in a compile-time
-configuration file &-- this is common in free versions of Unix) the two file
-names must be different, because in this mode the Berkeley DB functions create
-a single output file using exactly the name given. For example,
+configuration file &-- this is common in free versions of Unix) the two
+filenames must be different, because in this mode the Berkeley DB functions
+create a single output file using exactly the name given. For example,
.code
exim_dbmbuild /etc/aliases /etc/aliases.db
.endd
environment, the suffixes are added to the second argument of
&'exim_dbmbuild'&, so it can be the same as the first. This is also the case
when the Berkeley functions are used in compatibility mode (though this is not
-recommended), because in that case it adds a &_.db_& suffix to the file name.
+recommended), because in that case it adds a &_.db_& suffix to the filename.
If a duplicate key is encountered, the program outputs a warning, and when it
finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
mailbox, which is the same as Exim's default. The use of &%-flock%& or
&%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
requires that the directory containing the file be writeable. Locking by lock
-file does not last for ever; Exim assumes that a lock file is expired if it is
+file does not last forever; Exim assumes that a lock file is expired if it is
more than 30 minutes old.
The &%-mbx%& option can be used with either or both of &%-fcntl%& or
End
.endd
.cindex "admin user"
-In order to see the contents of messages on the queue, and to operate on them,
+In order to see the contents of messages in the queue, and to operate on them,
&'eximon'& must either be run as root or by an admin user.
The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
.section "The stripcharts" "SECID265"
.cindex "stripchart"
-The first stripchart is always a count of messages on the queue. Its name can
+The first stripchart is always a count of messages in the queue. Its name can
be configured by setting QUEUE_STRIPCHART_NAME in the
&_Local/eximon.conf_& file. The remaining stripcharts are defined in the
configuration script by regular expression matches on log file entries, making
.section "The queue display" "SECID268"
.cindex "queue" "display in monitor"
The bottom section of the monitor window contains a list of all messages that
-are on the queue, which includes those currently being received or delivered,
+are in the queue, which includes those currently being received or delivered,
as well as those awaiting delivery. The size of this subwindow is controlled by
parameters in the configuration file &_Local/eximon.conf_&, and the frequency
at which it is updated is controlled by another parameter in the same file &--
to force an update of the queue display at any time.
When a host is down for some time, a lot of pending mail can build up for it,
-and this can make it hard to deal with other messages on the queue. To help
+and this can make it hard to deal with other messages in the queue. To help
with this situation there is a button next to &"Update"& called &"Hide"&. If
pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
type anything in here and press &"Return"&, the text is added to a chain of
pressing the &"Hide"& button.
The queue display contains, for each unhidden queued message, the length of
-time it has been on the queue, the size of the message, the message id, the
+time it has been in the queue, the size of the message, the message id, the
message sender, and the first undelivered recipient, all on one line. If it is
a bounce message, the sender is shown as &"<>"&. If there is more than one
recipient to which the message has not yet been delivered, subsequent ones are
&'body'&: The contents of the spool file containing the body of the message are
displayed in a new text window. There is a default limit of 20,000 bytes to the
amount of data displayed. This can be changed by setting the BODY_MAX
-option at compile time, or the EXIMON_BODY_MAX option at run time.
+option at compile time, or the EXIMON_BODY_MAX option at runtime.
.next
&'deliver message'&: A call to Exim is made using the &%-M%& option to request
delivery of the message. This causes an automatic thaw if the message is
.ilist
ALT_CONFIG_PREFIX can be set to a string that is required to match the
-start of any file names used with the &%-C%& option. When it is set, these file
-names are also not allowed to contain the sequence &"/../"&. (However, if the
-value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
+start of any filenames used with the &%-C%& option. When it is set, these
+filenames are also not allowed to contain the sequence &"/../"&. (However, if
+the value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
&_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
default setting for &%ALT_CONFIG_PREFIX%&.
obviously more secure if Exim does not run as root except when necessary.
For this reason, a user and group for Exim to use must be defined in
&_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
-group"&. Their values can be changed by the run time configuration, though this
+group"&. Their values can be changed by the runtime configuration, though this
is not recommended. Often a user called &'exim'& is used, but some sites use
&'mail'& or another user name altogether.
unprivileged), Exim must be built to allow group read access to its spool
files.
+By default, regular users are trusted to perform basic testing and
+introspection commands, as themselves. This setting can be tightened by
+setting the &%commandline_checks_require_admin%& option.
+This affects most of the checking options,
+such as &%-be%& and anything else &%-b*%&.
.section "Spool files" "SECID275"
is insurance against disk crashes where the directory is lost but the files
themselves are recoverable.
+The file formats may be changed, or new formats added, at any release.
+Spool files are not intended as an interface to other programs
+and should not be used as such.
+
Some people are tempted into editing -D files in order to modify messages. You
need to be extremely careful if you do this; it is not recommended and you are
on your own if you do it. Here are some of the pitfalls:
.next
.vindex "&$body_linecount$&"
If you change the number of lines in the file, the value of
-&$body_linecount$&, which is stored in the -H file, will be incorrect. At
-present, this value is not used by Exim, but there is no guarantee that this
-will always be the case.
+&$body_linecount$&, which is stored in the -H file, will be incorrect and can
+cause incomplete transmission of messages or undeliverable messages.
.next
If the message is in MIME format, you must take care not to break it.
.next
-J file and uses it to update the -H file before starting the next delivery
attempt.
+Files whose names end with -K or .eml may also be seen in the spool.
+These are temporaries used for DKIM or malware processing, when that is used.
+They should be tidied up by normal operations; any old ones are probably
+relics of crashes and can be removed.
+
.section "Format of the -H file" "SECID282"
.cindex "uid (user id)" "in spool file"
.cindex "gid (group id)" "in spool file"
&$authenticated_sender$& variable.
.vitem "&%-body_linecount%&&~<&'number'&>"
-This records the number of lines in the body of the message, and is always
-present.
+This records the number of lines in the body of the message, and is
+present unless &%-spool_file_wireformat%& is.
.vitem "&%-body_zerocount%&&~<&'number'&>"
This records the number of binary zero bytes in the body of the message, and is
If a message was scanned by SpamAssassin, this is present. It records the value
of &$spam_score_int$&.
+.vitem &%-spool_file_wireformat%&
+The -D file for this message is in wire-format (for ESMTP CHUNKING)
+rather than Unix-format.
+The line-ending is CRLF rather than newline.
+There is still, however, no leading-dot-stuffing.
+
.vitem &%-tls_certificate_verified%&
A TLS certificate was received from the client that sent this message, and the
certificate was verified by the server.
certificate.
.endlist
+.new
+Any of the above may have an extra hyphen prepended, to indicate the the
+corresponding data is untrusted.
+.wen
+
Following the options there is a list of those addresses to which the message
is not to be delivered. This set of addresses is initialized from the command
line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
.ecindex IIDforspo2
.ecindex IIDforspo3
+.section "Format of the -D file" "SECID282a"
+The data file is traditionally in Unix-standard format: lines are ended with
+an ASCII newline character.
+However, when the &%spool_wireformat%& main option is used some -D files
+can have an alternate format.
+This is flagged by a &%-spool_file_wireformat%& line in the corresponding -H file.
+The -D file lines (not including the first name-component line) are
+suitable for direct copying to the wire when transmitting using the
+ESMTP CHUNKING option, meaning lower processing overhead.
+Lines are terminated with an ASCII CRLF pair.
+There is no dot-stuffing (and no dot-termination).
+
. ////////////////////////////////////////////////////////////////////////////
. ////////////////////////////////////////////////////////////////////////////
-.chapter "Support for DKIM (DomainKeys Identified Mail)" "CHAPdkim" &&&
- "DKIM Support"
+.chapter "DKIM, SPF and DMARC" "CHAPdkim" &&&
+ "DKIM, SPF and DMARC Support"
+
+.section "DKIM (DomainKeys Identified Mail)" SECDKIM
.cindex "DKIM"
DKIM is a mechanism by which messages sent by some entity can be provably
linked to a domain which that entity controls. It permits reputation to
be tracked on a per-domain basis, rather than merely upon source IP address.
-DKIM is documented in RFC 4871.
+DKIM is documented in RFC 6376.
+
+As DKIM relies on the message being unchanged in transit, messages handled
+by a mailing-list (which traditionally adds to the message) will not match
+any original DKIM signature.
-.new
DKIM support is compiled into Exim by default if TLS support is present.
-.wen
It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
-Exim's DKIM implementation allows to
+Exim's DKIM implementation allows for
.olist
-Sign outgoing messages: This function is implemented in the SMTP transport.
+Signing outgoing messages: This function is implemented in the SMTP transport.
It can co-exist with all other Exim features
(including transport filters)
except cutthrough delivery.
.next
-Verify signatures in incoming messages: This is implemented by an additional
+Verifying signatures in incoming messages: This is implemented by an additional
ACL (acl_smtp_dkim), which can be called several times per message, with
different signature contexts.
.endlist
Exim's standard controls.
Please note that verification of DKIM signatures in incoming mail is turned
-on by default for logging purposes. For each signature in incoming email,
+on by default for logging (in the <= line) purposes.
+
+Additional log detail can be enabled using the &%dkim_verbose%& log_selector.
+When set, for each signature in incoming email,
exim will log a line displaying the most important signature details, and the
signature status. Here is an example (with line-breaks added for clarity):
.code
c=relaxed/relaxed a=rsa-sha1
i=@facebookmail.com t=1252484542 [verification succeeded]
.endd
+
You might want to turn off DKIM verification processing entirely for internal
or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
control modifier. This should typically be done in the RCPT ACL, at points
senders).
-.section "Signing outgoing messages" "SECID513"
+.section "Signing outgoing messages" "SECDKIMSIGN"
.cindex "DKIM" "signing"
-Signing is implemented by setting private options on the SMTP transport.
-These options take (expandable) strings as arguments.
+For signing to be usable you must have published a DKIM record in DNS.
+Note that RFC 8301 (which does not cover EC keys) says:
+.code
+rsa-sha1 MUST NOT be used for signing or verifying.
-.option dkim_domain smtp string&!! unset
-MANDATORY:
-The domain you want to sign with. The result of this expanded
-option is put into the &%$dkim_domain%& expansion variable.
+Signers MUST use RSA keys of at least 1024 bits for all keys.
+Signers SHOULD use RSA keys of at least 2048 bits.
+.endd
-.option dkim_selector smtp string&!! unset
-MANDATORY:
-This sets the key selector string. You can use the &%$dkim_domain%& expansion
-variable to look up a matching selector. The result is put in the expansion
-variable &%$dkim_selector%& which should be used in the &%dkim_private_key%&
+Note also that the key content (the 'p=' field)
+in the DNS record is different between RSA and EC keys;
+for the former it is the base64 of the ASN.1 for the RSA public key
+(equivalent to the private-key .pem with the header/trailer stripped)
+but for EC keys it is the base64 of the pure key; no ASN.1 wrapping.
+
+Signing is enabled by setting private options on the SMTP transport.
+These options take (expandable) strings as arguments.
+
+.option dkim_domain smtp string list&!! unset
+The domain(s) you want to sign with.
+After expansion, this can be a list.
+Each element in turn,
+.new
+lowercased,
+.wen
+is put into the &%$dkim_domain%& expansion variable
+while expanding the remaining signing options.
+If it is empty after expansion, DKIM signing is not done,
+and no error will result even if &%dkim_strict%& is set.
+
+.option dkim_selector smtp string list&!! unset
+This sets the key selector string.
+After expansion, which can use &$dkim_domain$&, this can be a list.
+Each element in turn is put in the expansion
+variable &%$dkim_selector%& which may be used in the &%dkim_private_key%&
option along with &%$dkim_domain%&.
+If the option is empty after expansion, DKIM signing is not done for this domain,
+and no error will result even if &%dkim_strict%& is set.
.option dkim_private_key smtp string&!! unset
-MANDATORY:
-This sets the private key to use. You can use the &%$dkim_domain%& and
+This sets the private key to use.
+You can use the &%$dkim_domain%& and
&%$dkim_selector%& expansion variables to determine the private key to use.
The result can either
.ilist
-be a valid RSA private key in ASCII armor, including line breaks.
+be a valid RSA private key in ASCII armor (.pem file), including line breaks
+.next
+with GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
+be a valid Ed25519 private key (same format as above)
.next
start with a slash, in which case it is treated as a file that contains
-the private key.
+the private key
.next
be "0", "false" or the empty string, in which case the message will not
be signed. This case will not result in an error, even if &%dkim_strict%&
is set.
.endlist
+To generate keys under OpenSSL:
+.code
+openssl genrsa -out dkim_rsa.private 2048
+openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM
+.endd
+Take the base-64 lines from the output of the second command, concatenated,
+for the DNS TXT record.
+See section 3.6 of RFC6376 for the record specification.
+
+Under GnuTLS:
+.code
+certtool --generate-privkey --rsa --bits=2048 --password='' -8 --outfile=dkim_rsa.private
+certtool --load-privkey=dkim_rsa.private --pubkey-info
+.endd
+
+Note that RFC 8301 says:
+.code
+Signers MUST use RSA keys of at least 1024 bits for all keys.
+Signers SHOULD use RSA keys of at least 2048 bits.
+.endd
+
+.new
+EC keys for DKIM are defined by RFC 8463.
+.wen
+They are considerably smaller than RSA keys for equivalent protection.
+As they are a recent development, users should consider dual-signing
+(by setting a list of selectors, and an expansion for this option)
+for some transition period.
+The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
+for EC keys.
+
+OpenSSL 1.1.1 and GnuTLS 3.6.0 can create Ed25519 private keys:
+.code
+openssl genpkey -algorithm ed25519 -out dkim_ed25519.private
+certtool --generate-privkey --key-type=ed25519 --outfile=dkim_ed25519.private
+.endd
+
+To produce the required public key value for a DNS record:
+.code
+openssl pkey -outform DER -pubout -in dkim_ed25519.private | tail -c +13 | base64
+certtool --load_privkey=dkim_ed25519.private --pubkey_info --outder | tail -c +13 | base64
+.endd
+
+.new
+Exim also supports an alternate format
+of Ed25519 keys in DNS which was a candidate during development
+of the standard, but not adopted.
+A future release will probably drop that support.
+.wen
+
+.option dkim_hash smtp string&!! sha256
+Can be set to any one of the supported hash methods, which are:
+.ilist
+&`sha1`& &-- should not be used, is old and insecure
+.next
+&`sha256`& &-- the default
+.next
+&`sha512`& &-- possibly more secure but less well supported
+.endlist
+
+Note that RFC 8301 says:
+.code
+rsa-sha1 MUST NOT be used for signing or verifying.
+.endd
+
+.option dkim_identity smtp string&!! unset
+If set after expansion, the value is used to set an "i=" tag in
+the signing header. The DKIM standards restrict the permissible
+syntax of this optional tag to a mail address, with possibly-empty
+local part, an @, and a domain identical to or subdomain of the "d="
+tag value. Note that Exim does not check the value.
+
.option dkim_canon smtp string&!! unset
-OPTIONAL:
This option sets the canonicalization method used when signing a message.
The DKIM RFC currently supports two methods: "simple" and "relaxed".
The option defaults to "relaxed" when unset. Note: the current implementation
-only supports using the same canonicalization method for both headers and body.
+only supports signing with the same canonicalization method for both headers and body.
.option dkim_strict smtp string&!! unset
-OPTIONAL:
This option defines how Exim behaves when signing a message that
should be signed fails for some reason. When the expansion evaluates to
either "1" or "true", Exim will defer. Otherwise Exim will send the message
unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
variables here.
-.option dkim_sign_headers smtp string&!! unset
-OPTIONAL:
-When set, this option must expand to (or be specified as) a colon-separated
-list of header names. Headers with these names will be included in the message
-signature. When unspecified, the header names recommended in RFC4871 will be
-used.
+.option dkim_sign_headers smtp string&!! "see below"
+If set, this option must expand to a colon-separated
+list of header names.
+Headers with these names, or the absence or such a header, will be included
+in the message signature.
+When unspecified, the header names listed in RFC4871 will be used,
+whether or not each header is present in the message.
+The default list is available for the expansion in the macro
+"_DKIM_SIGN_HEADERS".
+
+If a name is repeated, multiple headers by that name (or the absence thereof)
+will be signed. The textually later headers in the headers part of the
+message are signed first, if there are multiples.
+
+A name can be prefixed with either an '=' or a '+' character.
+If an '=' prefix is used, all headers that are present with this name
+will be signed.
+If a '+' prefix if used, all headers that are present with this name
+will be signed, and one signature added for a missing header with the
+name will be appended.
+
+.option dkim_timestamps smtp integer&!! unset
+This option controls the inclusion of timestamp information in the signature.
+If not set, no such information will be included.
+Otherwise, must be an unsigned number giving an offset in seconds from the current time
+for the expiry tag
+(eg. 1209600 for two weeks);
+both creation (t=) and expiry (x=) tags will be included.
+
+RFC 6376 lists these tags as RECOMMENDED.
+
+
+.section "Verifying DKIM signatures in incoming mail" "SECDKIMVFY"
+.cindex "DKIM" "verification"
+Verification of DKIM signatures in SMTP incoming email is done for all
+messages for which an ACL control &%dkim_disable_verify%& has not been set.
+.new
+.cindex DKIM "selecting signature algorithms"
+Individual classes of signature algorithm can be ignored by changing
+the main options &%dkim_verify_hashes%& or &%dkim_verify_keytypes%&.
+The &%dkim_verify_minimal%& option can be set to cease verification
+processing for a message once the first passing signature is found.
+.wen
-.section "Verifying DKIM signatures in incoming mail" "SECID514"
-.cindex "DKIM" "verification"
+.cindex authentication "expansion item"
+Performing verification sets up information used by the
+&%authresults%& expansion item.
-Verification of DKIM signatures in incoming email is implemented via the
-&%acl_smtp_dkim%& ACL. By default, this ACL is called once for each
-syntactically(!) correct signature in the incoming message.
+.new
+For most purposes the default option settings suffice and the remainder
+of this section can be ignored.
+.wen
+
+The results of verification are made available to the
+&%acl_smtp_dkim%& ACL, which can examine and modify them.
A missing ACL definition defaults to accept.
+By default, the ACL is called once for each
+syntactically(!) correct signature in the incoming message.
If any ACL call does not accept, the message is not accepted.
-If a cutthrough delivery was in progress for the message it is
+If a cutthrough delivery was in progress for the message, that is
summarily dropped (having wasted the transmission effort).
-To evaluate the signature in the ACL a large number of expansion variables
+To evaluate the verification result in the ACL
+a large number of expansion variables
containing the signature status and its details are set up during the
runtime of the ACL.
Calling the ACL only for existing signatures is not sufficient to build
-more advanced policies. For that reason, the global option
-&%dkim_verify_signers%&, and a global expansion variable
+more advanced policies. For that reason, the main option
+&%dkim_verify_signers%&, and an expansion variable
&%$dkim_signers%& exist.
-The global option &%dkim_verify_signers%& can be set to a colon-separated
+The main option &%dkim_verify_signers%& can be set to a colon-separated
list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
called. It is expanded when the message has been received. At this point,
the expansion variable &%$dkim_signers%& already contains a colon-separated
If a domain or identity is listed several times in the (expanded) value of
&%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
+.new
+Note that if the option is set using untrustworthy data
+(such as the From: header)
+care should be taken to force lowercase for domains
+and for the domain part if identities.
+The default setting can be regarded as trustworthy in this respect.
+.wen
+
+If multiple signatures match a domain (or identity), the ACL is called once
+for each matching signature.
+
-Inside the &%acl_smtp_dkim%&, the following expansion variables are
+Inside the DKIM ACL, the following expansion variables are
available (from most to least important):
The signer that is being evaluated in this ACL run. This can be a domain or
an identity. This is one of the list items from the expanded main option
&%dkim_verify_signers%& (see above).
+
.vitem &%$dkim_verify_status%&
-A string describing the general status of the signature. One of
+Within the DKIM ACL,
+a string describing the general status of the signature. One of
.ilist
&%none%&: There is no signature in the message for the current domain or
identity (as reflected by &%$dkim_cur_signer%&).
.next
&%pass%&: The signature passed verification. It is valid.
.endlist
+
+This variable can be overwritten using an ACL 'set' modifier.
+This might, for instance, be done to enforce a policy restriction on
+hash-method or key-size:
+.code
+ warn condition = ${if eq {$dkim_verify_status}{pass}}
+ condition = ${if eq {${length_3:$dkim_algo}}{rsa}}
+ condition = ${if or {{eq {$dkim_algo}{rsa-sha1}} \
+ {< {$dkim_key_length}{1024}}}}
+ logwrite = NOTE: forcing DKIM verify fail (was pass)
+ set dkim_verify_status = fail
+ set dkim_verify_reason = hash too weak or key too short
+.endd
+
+So long as a DKIM ACL is defined (it need do no more than accept),
+after all the DKIM ACL runs have completed, the value becomes a
+colon-separated list of the values after each run.
+This is maintained for the mime, prdr and data ACLs.
+
.vitem &%$dkim_verify_reason%&
A string giving a little bit more detail when &%$dkim_verify_status%& is either
"fail" or "invalid". One of
re-written or otherwise changed in a way which is incompatible with
DKIM verification. It may of course also mean that the signature is forged.
.endlist
+
+This variable can be overwritten, with any value, using an ACL 'set' modifier.
+
.vitem &%$dkim_domain%&
The signing domain. IMPORTANT: This variable is only populated if there is
an actual signature in the message for the current domain or identity (as
reflected by &%$dkim_cur_signer%&).
+
.vitem &%$dkim_identity%&
The signing identity, if present. IMPORTANT: This variable is only populated
if there is an actual signature in the message for the current domain or
identity (as reflected by &%$dkim_cur_signer%&).
+
.vitem &%$dkim_selector%&
The key record selector string.
+
.vitem &%$dkim_algo%&
The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
+If running under GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
+may also be 'ed25519-sha256'.
+The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
+for EC keys.
+
+Note that RFC 8301 says:
+.code
+rsa-sha1 MUST NOT be used for signing or verifying.
+
+DKIM signatures identified as having been signed with historic
+algorithms (currently, rsa-sha1) have permanently failed evaluation
+.endd
+
+To enforce this you must either have a DKIM ACL which checks this variable
+and overwrites the &$dkim_verify_status$& variable as discussed above,
+.new
+or have set the main option &%dkim_verify_hashes%& to exclude
+processing of such signatures.
+.wen
+
.vitem &%$dkim_canon_body%&
The body canonicalization method. One of 'relaxed' or 'simple'.
-.vitem &%dkim_canon_headers%&
+
+.vitem &%$dkim_canon_headers%&
The header canonicalization method. One of 'relaxed' or 'simple'.
+
.vitem &%$dkim_copiedheaders%&
A transcript of headers and their values which are included in the signature
(copied from the 'z=' tag of the signature).
+Note that RFC6376 requires that verification fail if the From: header is
+not included in the signature. Exim does not enforce this; sites wishing
+strict enforcement should code the check explicitly.
+
.vitem &%$dkim_bodylength%&
The number of signed body bytes. If zero ("0"), the body is unsigned. If no
limit was set by the signer, "9999999999999" is returned. This makes sure
that this variable always expands to an integer value.
+&*Note:*& The presence of the signature tag specifying a signing body length
+is one possible route to spoofing of valid DKIM signatures.
+A paranoid implementation might wish to regard signature where this variable
+shows less than the "no limit" return as being invalid.
+
.vitem &%$dkim_created%&
UNIX timestamp reflecting the date and time when the signature was created.
When this was not specified by the signer, "0" is returned.
+
.vitem &%$dkim_expires%&
UNIX timestamp reflecting the date and time when the signer wants the
signature to be treated as "expired". When this was not specified by the
signer, "9999999999999" is returned. This makes it possible to do useful
integer size comparisons against this value.
+Note that Exim does not check this value.
+
.vitem &%$dkim_headernames%&
A colon-separated list of names of headers included in the signature.
+
.vitem &%$dkim_key_testing%&
"1" if the key record has the "testing" flag set, "0" if not.
+
.vitem &%$dkim_key_nosubdomains%&
"1" if the key record forbids subdomaining, "0" otherwise.
+
.vitem &%$dkim_key_srvtype%&
Service type (tag s=) from the key record. Defaults to "*" if not specified
in the key record.
+
.vitem &%$dkim_key_granularity%&
Key granularity (tag g=) from the key record. Defaults to "*" if not specified
in the key record.
+
.vitem &%$dkim_key_notes%&
Notes from the key record (tag n=).
+
.vitem &%$dkim_key_length%&
Number of bits in the key.
+
+Note that RFC 8301 says:
+.code
+Verifiers MUST NOT consider signatures using RSA keys of
+less than 1024 bits as valid signatures.
+.endd
+
+To enforce this you must have a DKIM ACL which checks this variable
+and overwrites the &$dkim_verify_status$& variable as discussed above.
+As EC keys are much smaller, the check should only do this for RSA keys.
+
.endlist
In addition, two ACL conditions are provided:
verb to a group of domains or identities. For example:
.code
-# Warn when Mail purportedly from GMail has no signature at all
-warn log_message = GMail sender without DKIM signature
+# Warn when Mail purportedly from GMail has no gmail signature
+warn log_message = GMail sender without gmail.com DKIM signature
sender_domains = gmail.com
dkim_signers = gmail.com
dkim_status = none
.endd
+Note that the above does not check for a total lack of DKIM signing;
+for that check for empty &$h_DKIM-Signature:$& in the data ACL.
+
.vitem &%dkim_status%&
ACL condition that checks a colon-separated list of possible DKIM verification
results against the actual result of verification. This is typically used
for more information of what they mean.
.endlist
+
+
+
+.section "SPF (Sender Policy Framework)" SECSPF
+.cindex SPF verification
+
+SPF is a mechanism whereby a domain may assert which IP addresses may transmit
+messages with its domain in the envelope from, documented by RFC 7208.
+For more information on SPF see &url(http://www.open-spf.org), a static copy of
+the &url(http://openspf.org).
+. --- 2019-10-28: still not https, open-spf.org is told to be a
+. --- web-archive copy of the now dead openspf.org site
+. --- See https://www.mail-archive.com/mailop@mailop.org/msg08019.html for a
+. --- discussion.
+
+Messages sent by a system not authorised will fail checking of such assertions.
+This includes retransmissions done by traditional forwarders.
+
+SPF verification support is built into Exim if SUPPORT_SPF=yes is set in
+&_Local/Makefile_&. The support uses the &_libspf2_& library
+&url(https://www.libspf2.org/).
+There is no Exim involvement in the transmission of messages;
+publishing certain DNS records is all that is required.
+
+For verification, an ACL condition and an expansion lookup are provided.
+.cindex authentication "expansion item"
+Performing verification sets up information used by the
+&%authresults%& expansion item.
+
+
+.cindex SPF "ACL condition"
+.cindex ACL "spf condition"
+The ACL condition "spf" can be used at or after the MAIL ACL.
+It takes as an argument a list of strings giving the outcome of the SPF check,
+and will succeed for any matching outcome.
+Valid strings are:
+.vlist
+.vitem &%pass%&
+The SPF check passed, the sending host is positively verified by SPF.
+
+.vitem &%fail%&
+The SPF check failed, the sending host is NOT allowed to send mail for the
+domain in the envelope-from address.
+
+.vitem &%softfail%&
+The SPF check failed, but the queried domain can't absolutely confirm that this
+is a forgery.
+
+.vitem &%none%&
+The queried domain does not publish SPF records.
+
+.vitem &%neutral%&
+The SPF check returned a "neutral" state. This means the queried domain has
+published a SPF record, but wants to allow outside servers to send mail under
+its domain as well. This should be treated like "none".
+
+.vitem &%permerror%&
+This indicates a syntax error in the SPF record of the queried domain.
+You may deny messages when this occurs.
+
+.vitem &%temperror%&
+This indicates a temporary error during all processing, including Exim's
+SPF processing. You may defer messages when this occurs.
+.endlist
+
+You can prefix each string with an exclamation mark to invert
+its meaning, for example "!fail" will match all results but
+"fail". The string list is evaluated left-to-right, in a
+short-circuit fashion.
+
+Example:
+.code
+deny spf = fail
+ message = $sender_host_address is not allowed to send mail from \
+ ${if def:sender_address_domain \
+ {$sender_address_domain}{$sender_helo_name}}. \
+ Please see http://www.open-spf.org/Why?scope=\
+ ${if def:sender_address_domain {mfrom}{helo}};\
+ identity=${if def:sender_address_domain \
+ {$sender_address}{$sender_helo_name}};\
+ ip=$sender_host_address
+.endd
+
+When the spf condition has run, it sets up several expansion
+variables:
+
+.cindex SPF "verification variables"
+.vlist
+.vitem &$spf_header_comment$&
+.vindex &$spf_header_comment$&
+ This contains a human-readable string describing the outcome
+ of the SPF check. You can add it to a custom header or use
+ it for logging purposes.
+
+.vitem &$spf_received$&
+.vindex &$spf_received$&
+ This contains a complete Received-SPF: header that can be
+ added to the message. Please note that according to the SPF
+ draft, this header must be added at the top of the header
+ list. Please see section 10 on how you can do this.
+
+ Note: in case of "Best-guess" (see below), the convention is
+ to put this string in a header called X-SPF-Guess: instead.
+
+.vitem &$spf_result$&
+.vindex &$spf_result$&
+ This contains the outcome of the SPF check in string form,
+ one of pass, fail, softfail, none, neutral, permerror or
+ temperror.
+
+.vitem &$spf_result_guessed$&
+.vindex &$spf_result_guessed$&
+ This boolean is true only if a best-guess operation was used
+ and required in order to obtain a result.
+
+.vitem &$spf_smtp_comment$&
+.vindex &$spf_smtp_comment$&
+ This contains a string that can be used in a SMTP response
+ to the calling party. Useful for "fail".
+.endlist
+
+
+.cindex SPF "ACL condition"
+.cindex ACL "spf_guess condition"
+.cindex SPF "best guess"
+In addition to SPF, you can also perform checks for so-called
+"Best-guess". Strictly speaking, "Best-guess" is not standard
+SPF, but it is supported by the same framework that enables SPF
+capability.
+Refer to &url(http://www.open-spf.org/FAQ/Best_guess_record)
+for a description of what it means.
+. --- 2019-10-28: still not https:
+
+To access this feature, simply use the spf_guess condition in place
+of the spf one. For example:
+
+.code
+deny spf_guess = fail
+ message = $sender_host_address doesn't look trustworthy to me
+.endd
+
+In case you decide to reject messages based on this check, you
+should note that although it uses the same framework, "Best-guess"
+is not SPF, and therefore you should not mention SPF at all in your
+reject message.
+
+When the spf_guess condition has run, it sets up the same expansion
+variables as when spf condition is run, described above.
+
+Additionally, since Best-guess is not standardized, you may redefine
+what "Best-guess" means to you by redefining the main configuration
+&%spf_guess%& option.
+For example, the following:
+
+.code
+spf_guess = v=spf1 a/16 mx/16 ptr ?all
+.endd
+
+would relax host matching rules to a broader network range.
+
+
+.cindex SPF "lookup expansion"
+.cindex lookup spf
+A lookup expansion is also available. It takes an email
+address as the key and an IP address
+.new
+(v4 or v6)
+.wen
+as the database:
+
+.code
+ ${lookup {username@domain} spf {ip.ip.ip.ip}}
+.endd
+
+The lookup will return the same result strings as can appear in
+&$spf_result$& (pass,fail,softfail,neutral,none,err_perm,err_temp).
+
+
+
+
+
+.new
+.section DMARC SECDMARC
+.cindex DMARC verification
+
+DMARC combines feedback from SPF, DKIM, and header From: in order
+to attempt to provide better indicators of the authenticity of an
+email. This document does not explain the fundamentals; you
+should read and understand how it works by visiting the website at
+&url(http://www.dmarc.org/).
+
+If Exim is built with DMARC support,
+the libopendmarc library is used.
+
+For building Exim yourself, obtain the library from
+&url(http://sourceforge.net/projects/opendmarc/)
+to obtain a copy, or find it in your favorite rpm package
+repository. You will need to attend to the local/Makefile feature
+SUPPORT_DMARC and the associated LDFLAGS addition.
+This description assumes
+that headers will be in /usr/local/include, and that the libraries
+are in /usr/local/lib.
+
+. subsection
+
+There are three main-configuration options:
+.cindex DMARC "configuration options"
+
+The &%dmarc_tld_file%& option
+.oindex &%dmarc_tld_file%&
+defines the location of a text file of valid
+top level domains the opendmarc library uses
+during domain parsing. Maintained by Mozilla,
+the most current version can be downloaded
+from a link at &url(https://publicsuffix.org/list/, currently pointing
+at https://publicsuffix.org/list/public_suffix_list.dat)
+See also util/renew-opendmarc-tlds.sh script.
+The default for the option is /etc/exim/opendmarc.tlds.
+
+
+The &%dmarc_history_file%& option, if set
+.oindex &%dmarc_history_file%&
+defines the location of a file to log results
+of dmarc verification on inbound emails. The
+contents are importable by the opendmarc tools
+which will manage the data, send out DMARC
+reports, and expire the data. Make sure the
+directory of this file is writable by the user
+exim runs as.
+The default is unset.
+
+The &%dmarc_forensic_sender%& option
+.oindex &%dmarc_forensic_sender%&
+defines an alternate email address to use when sending a
+forensic report detailing alignment failures
+if a sender domain's dmarc record specifies it
+and you have configured Exim to send them.
+If set, this is expanded and used for the
+From: header line; the address is extracted
+from it and used for the envelope from.
+If not set (the default), the From: header is expanded from
+the dsn_from option, and <> is used for the
+envelope from.
+
+. I wish we had subsections...
+
+.cindex DMARC controls
+By default, the DMARC processing will run for any remote,
+non-authenticated user. It makes sense to only verify DMARC
+status of messages coming from remote, untrusted sources. You can
+use standard conditions such as hosts, senders, etc, to decide that
+DMARC verification should *not* be performed for them and disable
+DMARC with a control setting:
+.code
+ control = dmarc_disable_verify
+.endd
+A DMARC record can also specify a "forensic address", which gives
+exim an email address to submit reports about failed alignment.
+Exim does not do this by default because in certain conditions it
+results in unintended information leakage (what lists a user might
+be subscribed to, etc). You must configure exim to submit forensic
+reports to the owner of the domain. If the DMARC record contains a
+forensic address and you specify the control statement below, then
+exim will send these forensic emails. It's also advised that you
+configure a dmarc_forensic_sender because the default sender address
+construction might be inadequate.
+.code
+ control = dmarc_enable_forensic
+.endd
+(AGAIN: You can choose not to send these forensic reports by simply
+not putting the dmarc_enable_forensic control line at any point in
+your exim config. If you don't tell it to send them, it will not
+send them.)
+
+There are no options to either control. Both must appear before
+the DATA acl.
+
+. subsection
+
+DMARC checks cam be run on incoming SMTP messages by using the
+"dmarc_status" ACL condition in the DATA ACL. You are required to
+call the "spf" condition first in the ACLs, then the "dmarc_status"
+condition. Putting this condition in the ACLs is required in order
+for a DMARC check to actually occur. All of the variables are set
+up before the DATA ACL, but there is no actual DMARC check that
+occurs until a "dmarc_status" condition is encountered in the ACLs.
+
+The dmarc_status condition takes a list of strings on its
+right-hand side. These strings describe recommended action based
+on the DMARC check. To understand what the policy recommendations
+mean, refer to the DMARC website above. Valid strings are:
+.display
+&'accept '& The DMARC check passed and the library recommends accepting the email.
+&'reject '& The DMARC check failed and the library recommends rejecting the email.
+&'quarantine '& The DMARC check failed and the library recommends keeping it for further inspection.
+&'none '& The DMARC check passed and the library recommends no specific action, neutral.
+&'norecord '& No policy section in the DMARC record for this sender domain.
+&'nofrom '& Unable to determine the domain of the sender.
+&'temperror '& Library error or dns error.
+&'off '& The DMARC check was disabled for this email.
+.endd
+You can prefix each string with an exclamation mark to invert its
+meaning, for example "!accept" will match all results but
+"accept". The string list is evaluated left-to-right in a
+short-circuit fashion. When a string matches the outcome of the
+DMARC check, the condition succeeds. If none of the listed
+strings matches the outcome of the DMARC check, the condition
+fails.
+
+Of course, you can also use any other lookup method that Exim
+supports, including LDAP, Postgres, MySQL, etc, as long as the
+result is a list of colon-separated strings.
+
+Performing the check sets up information used by the
+&%authresults%& expansion item.
+
+Several expansion variables are set before the DATA ACL is
+processed, and you can use them in this ACL. The following
+expansion variables are available:
+
+&$dmarc_status$&
+.vindex &$dmarc_status$&
+.cindex DMARC result
+is a one word status indicating what the DMARC library
+thinks of the email. It is a combination of the results of
+DMARC record lookup and the SPF/DKIM/DMARC processing results
+(if a DMARC record was found). The actual policy declared
+in the DMARC record is in a separate expansion variable.
+
+&$dmarc_status_text$&
+.vindex &$dmarc_status_text$&
+is a slightly longer, human readable status.
+
+&$dmarc_used_domain$&
+.vindex &$dmarc_used_domain$&
+is the domain which DMARC used to look up the DMARC policy record.
+
+&$dmarc_domain_policy$&
+.vindex &$dmarc_domain_policy$&
+is the policy declared in the DMARC record. Valid values
+are "none", "reject" and "quarantine". It is blank when there
+is any error, including no DMARC record.
+
+. subsection
+
+By default, Exim's DMARC configuration is intended to be
+non-intrusive and conservative. To facilitate this, Exim will not
+create any type of logging files without explicit configuration by
+you, the admin. Nor will Exim send out any emails/reports about
+DMARC issues without explicit configuration by you, the admin (other
+than typical bounce messages that may come about due to ACL
+processing or failure delivery issues).
+
+In order to log statistics suitable to be imported by the opendmarc
+tools, you need to:
+.ilist
+Configure the global setting dmarc_history_file
+.next
+Configure cron jobs to call the appropriate opendmarc history
+import scripts and truncating the dmarc_history_file
+.endlist
+
+In order to send forensic reports, you need to:
+.ilist
+Configure the global setting dmarc_forensic_sender
+.next
+Configure, somewhere before the DATA ACL, the control option to
+enable sending DMARC forensic reports
+.endlist
+
+. subsection
+
+Example usage:
+.code
+(RCPT ACL)
+ warn domains = +local_domains
+ hosts = +local_hosts
+ control = dmarc_disable_verify
+
+ warn !domains = +screwed_up_dmarc_records
+ control = dmarc_enable_forensic
+
+ warn condition = (lookup if destined to mailing list)
+ set acl_m_mailing_list = 1
+
+(DATA ACL)
+ warn dmarc_status = accept : none : off
+ !authenticated = *
+ log_message = DMARC DEBUG: $dmarc_status $dmarc_used_domain
+
+ warn dmarc_status = !accept
+ !authenticated = *
+ log_message = DMARC DEBUG: '$dmarc_status' for $dmarc_used_domain
+
+ warn dmarc_status = quarantine
+ !authenticated = *
+ set $acl_m_quarantine = 1
+ # Do something in a transport with this flag variable
+
+ deny condition = ${if eq{$dmarc_domain_policy}{reject}}
+ condition = ${if eq{$acl_m_mailing_list}{1}}
+ message = Messages from $dmarc_used_domain break mailing lists
+
+ deny dmarc_status = reject
+ !authenticated = *
+ message = Message from $dmarc_used_domain failed sender's DMARC policy, REJECT
+
+ warn add_header = :at_start:${authresults {$primary_hostname}}
+.endd
+
+.wen
+
+
+
+
. ////////////////////////////////////////////////////////////////////////////
. ////////////////////////////////////////////////////////////////////////////
.cindex "proxy support"
.cindex "proxy" "access via"
-.new
A proxy is an intermediate system through which communication is passed.
Proxies may provide a security, availability or load-distribution function.
To include this support, include &"SUPPORT_PROXY=yes"&
in Local/Makefile.
-It was built on specifications from:
-http://haproxy.1wt.eu/download/1.5/doc/proxy-protocol.txt
-That URL was revised in May 2014 to version 2 spec:
-http://git.1wt.eu/web?p=haproxy.git;a=commitdiff;h=afb768340c9d7e50d8e
+It was built on the HAProxy specification, found at
+&url(https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt).
The purpose of this facility is so that an application load balancer,
such as HAProxy, can sit in front of several Exim servers
Use of a proxy is enabled by setting the &%hosts_proxy%&
main configuration option to a hostlist; connections from these
hosts will use Proxy Protocol.
+Exim supports both version 1 and version 2 of the Proxy Protocol and
+automatically determines which version is in use.
+
+The Proxy Protocol header is the first data received on a TCP connection
+and is inserted before any TLS-on-connect handshake from the client; Exim
+negotiates TLS between Exim-as-server and the remote client, not between
+Exim and the proxy server.
The following expansion variables are usable
(&"internal"& and &"external"& here refer to the interfaces
of the proxy):
.display
-&'proxy_host_address '& internal IP address of the proxy
-&'proxy_host_port '& internal TCP port of the proxy
-&'proxy_target_address '& external IP address of the proxy
-&'proxy_target_port '& external TCP port of the proxy
-&'proxy_session '& boolean: SMTP connection via proxy
+&'proxy_external_address '& IP of host being proxied or IP of remote interface of proxy
+&'proxy_external_port '& Port of host being proxied or Port on remote interface of proxy
+&'proxy_local_address '& IP of proxy server inbound or IP of local interface of proxy
+&'proxy_local_port '& Port of proxy server inbound or Port on local interface of proxy
+&'proxy_session '& boolean: SMTP connection via proxy
.endd
-If &$proxy_session$& is set but &$proxy_host_address$& is empty
+If &$proxy_session$& is set but &$proxy_external_address$& is empty
there was a protocol error.
+The variables &$sender_host_address$& and &$sender_host_port$&
+will have values for the actual client system, not the proxy.
Since the real connections are all coming from the proxy, and the
per host connection tracking is done before Proxy Protocol is
(space-separated by default) where the initial element
is an IP address and any subsequent elements are options.
-Options are a string <name>=<value>.
+Options are a string <name>=<value>.
The list of options is in the following table:
.display
&'auth '& authentication method
To log the (local) IP of a proxy in the incoming or delivery logline,
add &"+proxy"& to the &%log_selector%& option.
This will add a component tagged with &"PRX="& to the line.
-.wen
. ////////////////////////////////////////////////////////////////////////////
. ////////////////////////////////////////////////////////////////////////////
.cindex internationalisation "email address"
.cindex EAI
.cindex i18n
-.cindex UTF-8 "mail name handling"
+.cindex utf8 "mail name handling"
-.new
Exim has support for Internationalised mail names.
To include this it must be built with SUPPORT_I18N and the libidn library.
Standards supported are RFCs 2060, 5890, 6530 and 6533.
+If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not
+instead of it) then IDNA2008 is supported; this adds an extra library
+requirement, upon libidn2.
+
.section "MTA operations" SECTi18nMTA
.cindex SMTPUTF8 "ESMTP option"
The main configuration option &%smtputf8_advertise_hosts%& specifies
.cindex log protocol
.cindex SMTPUTF8 logging
+.cindex i18n logging
Log lines and Received-by: header lines will acquire a "utf8"
prefix on the protocol element, eg. utf8esmtp.
-The following expansion operator can be used:
+The following expansion operators can be used:
.code
${utf8_domain_to_alabel:str}
${utf8_domain_from_alabel:str}
${utf8_localpart_from_alabel:str}
.endd
-ACLs may use the following modifier:
+.cindex utf8 "address downconversion"
+.cindex i18n "utf8 address downconversion"
+The RCPT ACL
+may use the following modifier:
.display
control = utf8_downconvert
control = utf8_downconvert/<value>
If mua_wrapper is set, the utf8_downconvert control
is initially set to -1.
+The smtp transport has an option &%utf8_downconvert%&.
+If set it must expand to one of the three values described above,
+and it overrides any previously set value.
+
There is no explicit support for VRFY and EXPN.
Configurations supporting these should inspect
or &%headers_charset%& main configuration option (otherwise),
to the
modified UTF-7 encoding specified by RFC 2060,
-with the following exception: All occurences of <sep>
+with the following exception: All occurrences of <sep>
(which has to be a single character)
are replaced with periods ("."), and all periods and slashes that are not
<sep> and are not in the <specials> string are BASE64 encoded.
Note that the source charset setting is vital, and also that characters
must be representable in UTF-16.
-.wen
. ////////////////////////////////////////////////////////////////////////////
. ////////////////////////////////////////////////////////////////////////////
"Events"
.cindex events
-.new
The events mechanism in Exim can be used to intercept processing at a number
-of points. It was originally invented to giave a way to do customised logging
+of points. It was originally invented to give a way to do customised logging
actions (for example, to a database) but can also be used to modify some
processing actions.
The name is placed in the variable &$event_name$& and the event action
expansion must check this, as it will be called for every possible event type.
+.new
The current list of events is:
+.wen
.display
+&`dane:fail after transport `& per connection
&`msg:complete after main `& per message
&`msg:delivery after transport `& per recipient
&`msg:rcpt:host:defer after transport `& per recipient per host
&`msg:rcpt:defer after transport `& per recipient
&`msg:host:defer after transport `& per attempt
-&`msg:fail:delivery after main `& per recipient
+&`msg:fail:delivery after transport `& per recipient
&`msg:fail:internal after main `& per recipient
&`tcp:connect before transport `& per connection
&`tcp:close after transport `& per connection
&`tls:cert before both `& per certificate in verification chain
&`smtp:connect after transport `& per connection
+&`smtp:ehlo after transport `& per connection
.endd
New event types may be added in future.
before or after the action is associates with. Those which fire before
can be used to affect that action (more on this below).
+The third column in the table above says what section of the configuration
+should define the event action.
+
An additional variable, &$event_data$&, is filled with information varying
with the event type:
.display
-&`msg:delivery `& smtp confirmation mssage
+&`dane:fail `& failure reason
+&`msg:delivery `& smtp confirmation message
+&`msg:fail:internal `& failure reason
+&`msg:fail:delivery `& smtp error message
&`msg:rcpt:host:defer `& error string
&`msg:rcpt:defer `& error string
&`msg:host:defer `& error string
&`tls:cert `& verification chain depth
&`smtp:connect `& smtp banner
+&`smtp:ehlo `& smtp ehlo response
.endd
The :defer events populate one extra variable: &$event_defer_errno$&.
For complex operations an ACL expansion can be used in &%event_action%&
-however due to the multiple contextx that Exim operates in during
+however due to the multiple contexts that Exim operates in during
the course of its processing:
.ilist
variables set in transport events will not be visible outside that
return an empty string. Should it return anything else the
following will be forced:
.display
-&`msg:delivery `& (ignored)
-&`msg:host:defer `& (ignored)
-&`msg:fail:delivery`& (ignored)
&`tcp:connect `& do not connect
-&`tcp:close `& (ignored)
&`tls:cert `& refuse verification
&`smtp:connect `& close connection
.endd
-No other use is made of the result string.
+All other message types ignore the result string, and
+no other use is made of it.
For a tcp:connect event, if the connection is being made to a proxy
then the address and port variables will be that of the proxy and not
chain element received on the connection.
For OpenSSL it will trigger for every chain element including those
loaded locally.
-.wen
. ////////////////////////////////////////////////////////////////////////////
. ////////////////////////////////////////////////////////////////////////////
&_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
driver or lookup type and add it to the definition of OBJ.
.next
+Edit &_OS/Makefile-Base_& adding a &_.o_& file for the predefined-macros, to the
+definition of OBJ_MACRO. Add a set of line to do the compile also.
+.next
Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
&_src_&.
.next
git://git.exim.org / exim.git / blobdiff