. Update the Copyright year (only) when changing content.
. /////////////////////////////////////////////////////////////////////////////
-.set previousversion "4.97"
+.set previousversion "4.98"
.include ./local_params
.set ACL "access control lists (ACLs)"
.set drivernamemax "64"
.macro copyyear
-2023
+2024
.endmacro
. /////////////////////////////////////////////////////////////////////////////
.cindex "FAQ"
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(https://wiki.exim.org)),
+online information is &url(https://wiki.exim.org,the Exim wiki),
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
.cindex "bug reports"
.cindex "reporting bugs"
Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
-via the Bugzilla (&url(https://bugs.exim.org)). However, if you are unsure
+via &url(https://bugs.exim.org,the Bugzilla). 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.
versions. However, the more recent releases seem to have standardized on the
Berkeley DB library.
+.new
+Ownership of the Berkeley DB library has moved to a major corporation;
+development seems to have stalled and documentation is not freely available.
+This is probably not tenable for the long term use by Exim.
+.wen
+
Different DBM libraries have different conventions for naming the files they
use. When a program opens a file called &_dbmfile_&, there are several
possibilities:
&url(https://sourceforge.net/projects/tdb/files/). It has its own interface, and also
operates on a single file.
.next
-.new
-It is possible to use sqlite3 (&url(https://www.sqlite.org/index.html))
+It is possible to use &url(https://www.sqlite.org/index.html,sqlite3)
for the DBM library.
-.wen
.endlist
.cindex "USE_DB"
There is further detailed discussion about the various DBM libraries in the
file &_doc/dbm.discuss.txt_& in the Exim distribution.
+.new
+When moving from one DBM library to another,
+for the hints databases it suffices to just remove all the files in the
+directory named &"db/"& under the spool directory.
+This is because hints are only for optimisation and will be rebuilt
+during normal operations.
+Non-hints DBM databases (used by &"dbm"& lookups in the configuration)
+will need individual rebuilds for the new DBM library.
+This is not done automatically
+.wen
+
.section "Pre-building configuration" "SECID25"
-.section "Dynamically loaded lookup module support" "SECTdynamicmodules"
+.section "Dynamically loaded module support" "SECTdynamicmodules"
.cindex "lookup modules"
+.cindex "router modules"
+.cindex "transport modules"
+.cindex "authenticator modules"
.cindex "dynamic modules"
.cindex ".so building"
On some platforms, Exim supports not compiling all lookup types directly into
the main binary, instead putting some into external modules which can be loaded
on demand.
This permits packagers to build Exim with support for lookups with extensive
-library dependencies without requiring all users to install all of those
+library dependencies without requiring all systems to install all of those
dependencies.
-Most, but not all, lookup types can be built this way.
+.new
+Any combination of lookup types can be built this way.
+Lookup types that provide several variants will be loaded as
+Exim starts.
+Types that provide only one method are not loaded until used by
+the runtime configuration.
+.wen
-Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
+For building
+set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
installed; Exim will only load modules from that directory, as a security
measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
for your OS; see &_OS/Makefile-Linux_& for an example.
Then, for each module to be loaded dynamically, define the relevant
&`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
For example, this will build in lsearch but load sqlite and mysql support
-on demand:
+only if each is installed:
.code
LOOKUP_LSEARCH=yes
LOOKUP_SQLITE=2
LOOKUP_MYSQL=2
.endd
+Set also &`LOOKUP_`&<&'lookup_type'&>&` INCLUDE`& and
+&`LOOKUP_`&<&'lookup_type'&>`_LIBS if needed for each lookup type,
+ensuring that duplicates are not present in more global values.
+
+.new
+Similarly, authenticator, router and transport drivers can be built
+as external modules.
+Modules will be searched for as demanded by the runtime configuration,
+permitting a smaller Exim binary.
+
+For building, as above but using
+&`AUTH_*`&, &`ROUTER_*`& and &`TRANSPORT_*`& instead of &`LOOKUP_*`&,
+.wen
.section "The building process" "SECID29"
The word &"set"& at the start of a line, followed by a single space,
is recognised specially as defining a value for a variable.
-.new
.cindex "tainted data" "expansion testing"
If the sequence &",t"& is inserted before the space,
the value is marked as tainted.
-.wen
The syntax is otherwise the same as the ACL modifier &"set ="&.
.cmdopt -bem <&'filename'&>
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(https://www.jetmore.org/john/code/swaks/,swaks).
+&url(https://www.jetmore.org/john/code/swaks/,swaks,swaks).
.cmdopt -bhc <&'IP&~address'&>
This option operates in the same way as &%-bh%&, except that address
colon in the example above are necessary. If they were not there, the list would
be interpreted as the two items 127.0.0.1:: and 1.
-.section "Changing list separators" "SECTlistsepchange"
+.subsection "Changing list separators" "SECTlistsepchange"
.cindex "list separator" "changing"
.cindex "IPv6" "addresses in lists"
Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
-.section "Empty items in lists" "SECTempitelis"
+.subsection "Empty items in lists" "SECTempitelis"
.cindex "list" "empty item in"
An empty item at the end of a list is always ignored. In other words, trailing
separator characters are ignored. Thus, the list in
.cindex "dsearch lookup type"
The given file must be an absolute directory path; this is searched for an entry
whose name is the key by calling the &[lstat()]& function.
-.new
Unless the options (below) permit a path,
-.wen
the key may not contain any forward slash characters.
If &[lstat()]& succeeds then so does the lookup.
.cindex "tainted data" "dsearch result"
The given file is an LMDB database.
LMDB is a memory-mapped key-value store,
with API modeled loosely on that of BerkeleyDB.
-See &url(https://symas.com/products/lightning-memory-mapped-database/)
+See &url(https://symas.com/products/lightning-memory-mapped-database/,LMDB)
for the feature set and operation modes.
Exim provides read-only access via the LMDB C library.
${lookup pgsql,servers=master/db/name/pw {UPDATE ...} }
.endd
-.new
A now-deprecated syntax places the servers specification before the query,
semicolon separated:
.code
The new version avoids issues with tainted
arguments explicitly expanded as part of the query.
The entire string within the braces becomes tainted,
-including the server sepcification - which is not permissible.
+including the server specification - which is not permissible.
If the older sytax is used, a warning message will be logged.
This syntax will be removed in a future release.
-.wen
&*Note*&: server specifications in list-style lookups are still problematic.
anything (for example, setting a field to the value it already has), the result
is zero because no rows are affected.
-.new
To get an encryted connection, use a Mysql option file with the required
parameters for the connection.
-.wen
.subsection "Special PostgreSQL features" SECID74
.vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
-SRS encoding. See SECT &<<SECTSRS>>& for details.
+SRS encoding. See section &<<SECTSRS>>& for details.
For information on internationalisation support see &<<SECTi18nMTA>>&.
-.new
.vitem &*${xtextd:*&<&'string'&>&*}*&
.cindex "text forcing in strings"
.cindex "string" "xtext decoding"
.cindex "xtext"
.cindex "&%xtextd%& expansion item"
This performs xtext decoding of the string (per RFC 3461 section 4).
-.wen
.vindex "&$config_file$&"
The name of the main configuration file Exim is using.
+.vitem &$connection_id$&
+.vindex "&$connection_id$&"
+.cindex connection "identifier logging"
+An identifier for the accepted connection, for use in custom logging.
+
.vitem &$dkim_verify_status$&
Results of DKIM verification.
For details see section &<<SECDKIMVFY>>&.
.option acl_smtp_etrn main string&!! unset
.cindex "ETRN" "ACL for"
+.cindex "ETRN" advertisement
This option defines the ACL that is run when an SMTP ETRN command is
-received. See chapter &<<CHAPACL>>& for further details.
+received.
+If no value is set then the ETRN facility is not advertised.
+See chapter &<<CHAPACL>>& for further details.
.option acl_smtp_expn main string&!! unset
.cindex "EXPN" "ACL for"
This option defines the ACL that is run when an SMTP VRFY command is
received. See chapter &<<CHAPACL>>& for further details.
-.new
.option acl_smtp_wellknown main string&!! unset
.cindex "WELLKNOWN, ACL for"
This option defines the ACL that is run when an SMTP WELLKNOWN command is
received. See section &<<SECTWELLKNOWNACL>>& for further details.
-.wen
.option add_environment main "string list" empty
.cindex "environment" "set values"
See section &<<SECDKIMVFY>>&.
-.option dmarc_forensic_sender main string&!! unset &&&
- dmarc_history_file main string unset &&&
- dmarc_tld_file main string unset
+.options dmarc_forensic_sender main string&!! unset &&&
+ dmarc_history_file main string unset &&&
+ dmarc_tld_file main string unset
.cindex DMARC "main section options"
These options control DMARC processing.
See section &<<SECDMARC>>& for details.
. Allow this long option name to split; give it unsplit as a fifth argument
. for the automatic .oindex that is generated by .option.
+. WAS:
+. .option "extract_addresses_remove_ &~&~arguments"
+. but apparently this results in searchability problems; bug 1197
-.option "extract_addresses_remove_arguments" main boolean true &&&
- extract_addresses_remove_arguments
+.option extract_addresses_remove_arguments main boolean true
.oindex "&%-t%&"
.cindex "command line" "addresses with &%-t%&"
.cindex "Sendmail compatibility" "&%-t%& option"
.cindex "underscore in EHLO/HELO"
This option can be set to a string of rogue characters that are permitted in
non-ip-literal EHLO and HELO names in addition to the standard letters, digits,
-hyphens, and dots. For examplem if you really must allow underscores,
+hyphens, and dots. For example if you really must allow underscores,
you can set
.code
helo_allow_chars = _
-.new
.option limits_advertise_hosts main "host list&!!" *
.cindex LIMITS "suppressing advertising"
.cindex "ESMTP extensions" LIMITS
This option can be used to suppress the advertisement of the SMTP
LIMITS extension (RFC 9422) to specific hosts.
-If permitted, Exim as a servier will advertise in the EHLO response
+If permitted, Exim as a server will advertise in the EHLO response
the limit for RCPT commands set by the &%recipients_max%& option (if it is set)
and the limit for MAIL commands set by the &%smtp_accept_max_per_connection%&
option.
-.wen
.option local_from_check main boolean true
.cindex "&'Sender:'& header line" "disabling addition of"
The SMTP service extension keyword advertised is &"PIPECONNECT"&;
it permits the client to pipeline
-TCP connection and hello command (inclear phase),
+TCP connection and hello command (cleatext phase),
or TLS-establishment and hello command (encrypted phase),
on later connections to the same host.
Non-SMTP messages with too many recipients are failed, and no deliveries are
done.
-.new
For SMTP message the expansion is done after the connection is
accepted (but before any SMTP conversation) and may depend on
the IP addresses and port numbers of the connection.
&*Note*&: If an expansion is used for the option,
care should be taken that a resonable value results for
non-SMTP messages.
-.wen
.cindex "RCPT" "maximum number of incoming"
&*Note*&: The RFCs specify that an SMTP server should accept at least 100
. searchable. NM changed this occurrence for bug 1197 to no longer allow
. the option name to split.
-.option "smtp_accept_max_per_connection" main integer&!! 1000 &&&
- smtp_accept_max_per_connection
+.option smtp_accept_max_per_connection main integer&!! 1000
.cindex "SMTP" "limiting incoming message count"
.cindex "limit" "messages per SMTP connection"
The value of this option limits the number of MAIL commands that Exim is
. See the comment on smtp_accept_max_per_connection
-.option "smtp_accept_queue_per_connection" main integer 10 &&&
- smtp_accept_queue_per_connection
+.option smtp_accept_queue_per_connection main integer 10
.cindex "queueing incoming messages"
.cindex "message" "queueing by message count"
This option limits the number of delivery processes that Exim starts
See also &%bounce_message_file%&.
-.new
.option wellknown_advertise_hosts main boolean unset
.cindex WELLKNOWN advertisement
.cindex "ESMTP extensions" WELLKNOWN
This option enables the advertising of the SMTP WELLKNOWN extension.
See also the &%acl_smtp_wellknown%& ACL (&<<SECTWELLKNOWNACL>>&).
-.wen
.option write_rejectlog main boolean true
.cindex "reject log" "disabling"
and are rewritten according to the global rewriting rules.
+.option sieve_inbox redirect string&!! inbox
+.new
+The value of this option is passed to a Sieve filter to specify the
+name of the mailbox used for "keep" operations (explicit or implicit).
+.wen
+
.option sieve_subaddress redirect string&!! unset
The value of this option is passed to a Sieve filter to specify the
:subaddress part of an address.
.endd
In this situation, the expansion of &%file%& or &%directory%& in the transport
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
+case of Sieve filters, the name &'inbox'& must be handled. It is the
+.new
+default
+.wen
+name that
is used as a result of a &"keep"& action in the filter. This example shows one
way of handling this requirement:
.code
location, absolute paths are used without change, and other folders are in the
&_mail_& directory within the home directory.
+.new
+An alternative for the &"keep"& aspect is to use the &%sieve_inbox%& option
+on the redirect router that calls the Sieve filter,
+to explicitly set the filename used.
+.wen
+
&*Note 1*&: While processing an Exim filter, a relative path such as
&_folder23_& is turned into an absolute path if a home directory is known to
the router. In particular, this is the case if &%check_local_user%& is set. If
&*Note 2*&: An absolute path in &$address_file$& is not treated specially;
the &%file%& or &%directory%& option is still used if it is set.
+.new
+&*Note 3*&: Permitting a user to enable writes to an absolute path
+may be a security issue.
+.wen
For testing purposes, this value can be overridden by the &%-oB%& command line
option.
-.new
.cindex "ESMTP extensions" LIMITS
If the peer advertises a LIMITS extension with a MAILMAX value,
and either TLSS is in use or was not advertised,
that value also constrains the result of this option.
-.wen
.option dane_require_tls_ciphers smtp string&!! unset
During the expansion of this option the &$item$& variable will have the
server's EHLO response.
-.new
For TLS-on-connect connections we do not have an EHLO
response to use. Because of this the default value of this option is
set to a static string for those cases, meaning that resumption will
always be attempted if permitted by the &%tls_resumption_hosts%& option.
-.wen
The result of the option expansion is included in the key used to store and
retrieve the TLS session, for session resumption.
so can cause parallel connections to the same host if &%remote_max_parallel%&
permits this.
-.new
.cindex "ESMTP extensions" LIMITS
If the peer advertises a LIMITS extension with a RCPTMAX value,
and either TLSS is in use or was not advertised,
that value also constrains the result of this option
and no parallel connections will be caused on meeting the RCPTMAX limit.
-.wen
.option message_linelength_limit smtp integer 998
only messages having the domain used for the DANE TLSA lookup are
sent on the connection.
-.new
.cindex "ESMTP extensions" LIMITS
If the peer advertises a LIMITS extension with a RCPTDOMAINMAX value,
and either TLSS is in use or was not advertised,
this option is regarded as being false.
-.wen
.option port smtp string&!! "see below"
deliveries into closed message stores. Exim also has support for running LMTP
over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
-.new
&*Note*&: When using LMTP it should be considered whether the default values
for some other features, such as DANE, are appropriate.
-.wen
If this option is set to &"smtps"&, the default value for the &%port%& option
changes to &"smtps"&, and the transport initiates TLS immediately after
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(https://www.samba.org/)). The code for the
+taken from the &url(https://www.samba.org/,Samba project). The code for the
server side was subsequently contributed by Tom Kistner. The mechanism works as
follows:
.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)).
+The specification is in
+&url(https://tools.ietf.org/html/rfc4422,PFC 4422) Appendix A.
It is only a transport and negotiation mechanism;
the process of authentication is entirely controlled
by the server configuration.
this authentication method on a secure (eg. under TLS) connection.
One possible use, compatible with the
-K-9 Mail Android client (&url(https://k9mail.github.io/)),
+&url(https://k9mail.github.io/,K-9 Mail Android client)
is for using X509 client certificates.
It thus overlaps in function with the TLS authenticator
If the ACL is not defined, processing completes as if
the feature was not requested by the client.
-.new
.subsection "The SMTP WELLKNOWN ACL" SECTWELLKNOWNACL
.cindex "WELLKNOWN" "ACL for"
.oindex "&%acl_smtp_wellknown%&"
giving a key for an item of "site-wide metadata".
The verb and key are separated by whitespace,
and the key is xtext-encoded (per RFC 3461 section 4).
-.wen
.subsection "The QUIT ACL" SECTQUITACL
For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&,
&%acl_smtp_vrfy%&
-.new
and &%acl_smtp_wellknown%&),
-.wen
the action when the ACL
is not defined is &"deny"&. This means that &%acl_smtp_rcpt%& must be
defined in order to receive any messages over an SMTP connection.
the operation and configuration of DKIM, see section &<<SECDKIM>>&.
-.vitem &*control&~=&~dmarc_disable_verify*&
+.vitem &*control&~=&~dmarc_disable_verify*& &&&
+ &*control&~=&~dmarc_enable_forensic*&
.cindex "disable DMARC verify"
-.cindex "DMARC" "disable verify"
-This control turns off DMARC verification processing entirely. For details on
+.cindex DMARC "disable verify"
+.cindex DMARC controls
+.cindex DMARC "forensic mails"
+These control affect DMARC processing. For details on
the operation and configuration of DMARC, see section &<<SECDMARC>>&.
+The &"disable"& turns off DMARC verification processing entirely.
+
.vitem &*control&~=&~dscp/*&<&'value'&>
.cindex "&ACL;" "setting DSCP value"
to a-label form.
For details see section &<<SECTi18nMTA>>&.
-.new
.vitem &*control&~=&~wellknown*&
This control sets up a response data file for a WELLKNOWN SMTP command.
It may only be used in an ACL servicing that command.
For details see section &<<SECTWELLKNOWNACL>>&.
-.wen
.endlist vlist
.endlist
The &%decode%& condition normally succeeds. It is only false for syntax
errors or unusual circumstances such as memory shortages.
-.new
The variable &$mime_filename$& will have the suggested name for the file.
Note however that this might contain anything, and is very difficult
to safely use as all or even part of the filename.
-.wen
If you place files outside of the default path, they are not
automatically unlinked.
.vitem &*void&~debug_printf(char&~*,&~...)*&
-This is Exim's debugging function, with arguments as for &'(printf()'&. The
+This is Exim's debugging function, with arguments as for &'printf()'&. The
output is written to the standard error stream. If no debugging is selected,
calls to &'debug_printf()'& have no effect. Normally, you should make calls
conditional on the &`local_scan`& debug selector by coding like this:
.cindex "SMTP" "batching over TCP/IP"
When a message is successfully delivered over a TCP/IP SMTP connection, Exim
looks in the hints database for the transport to see if there are any queued
-messages waiting for the host to which it is connected. If it finds one, it
-creates a new Exim process using the &%-MC%& option (which can only be used by
-a process running as root or the Exim user) and passes the TCP/IP socket to it
-so that it can deliver another message using the same socket. The new process
-does only those deliveries that are routed to the connected host, and may in
-turn pass the socket on to a third process, and so on.
+messages waiting for the host to which it is connected.
+If it finds one, it arranges to attempt that message on the same connection.
The &%connection_max_messages%& option of the &(smtp)& transport can be used to
limit the number of messages sent down a single TCP/IP connection.
.subsection "The ETRN command" SECTETRN
.cindex "ETRN" "processing"
.cindex "ESMTP extensions" ETRN
+Most modern installations never need to use this.
+It is used for managing messages queued for an intermittently-connecting
+destination (eg. one using a dialup connection).
+
+.oindex "&%acl_smtp_etrn%&"
+The command is only available if permitted by an ACL
+specfied by the main-section &%acl_smtp_etrn%& option.
+
RFC 1985 describes an ESMTP command called ETRN that is designed to
overcome the security problems of the TURN command (which has fallen into
disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
only way to log such cases is to interpose a script such as &_util/logargs.sh_&
between the caller and Exim.
.next
-.cindex "log" "connection identifier"
-&%connection_identifier%&: An identifier for the accepted connection is added to
+.cindex log "connection identifier"
+.cindex connection "identifier logging"
+&%connection_id%&: An identifier for the accepted connection is added to
connection start and end lines and to message accept lines.
The identifier is tagged by Ci=.
The value is PID-based, so will reset on reboot and will wrap.
.next
-.cindex "log" "connection rejections"
+.cindex log "connection rejections"
+.cindex connection "rejection logging"
&%connection_reject%&: A log entry is written whenever an incoming SMTP
connection is rejected, for whatever reason.
.next
-.cindex "log" "delayed delivery"
+.cindex log "delayed delivery"
.cindex "delayed delivery, logging"
&%delay_delivery%&: A log entry is written whenever a delivery process is not
started for an incoming message because the load is too high or too many
.cindex log "DKIM verification"
.cindex DKIM "verification logging"
&%dkim_verbose%&: A log entry is written for each attempted DKIM verification.
-.new
Also, on message delivery lines signing information (domain and selector)
is added, tagged with DKIM=.
-.wen
.next
.cindex "log" "dnslist defer"
.cindex "DNS list" "logging defer"
The &'misc'& database is used for
.ilist
-Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
-.next
Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
&(smtp)& transport)
.next
in a transport)
.next
Recording EHLO-time facilities advertised by hosts
+.next
+Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
.endlist
-.section "exim_dumpdb" "SECTdumpdb"
+.subsection "exim_dumpdb" "SECTdumpdb"
.cindex "&'exim_dumpdb'&"
The entire contents of a database are written to the standard output by the
&'exim_dumpdb'& program,
-.section "exim_tidydb" "SECTtidydb"
+.subsection "exim_tidydb" "SECTtidydb"
.cindex "&'exim_tidydb'&"
The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
database. If run with no options, it removes all records that are more than 30
-.section "exim_fixdb" "SECTfixdb"
+.subsection "exim_fixdb" "SECTfixdb"
.cindex "&'exim_fixdb'&"
The &'exim_fixdb'& program is a utility for interactively modifying databases.
Its main use is for testing Exim, but it might also be occasionally useful for
.next
A queue runner process retains root privilege throughout its execution. Its
job is to fork a controlled sequence of delivery processes.
+
+.next
+A delivery process retains root privilege throughout most of its execution.,
+including while the recipient addresses in a message are being routed.
+
+.ilist
+However, if a user's filter file has to be processed,
+this is done in a subprocess that runs under the individual user's uid and
+gid. A system filter is run as root unless &%system_filter_user%& is set.
+.endlist
+
+Any actual deliveries (that is, the transports themselves) are run in
+subprocesses which always change to a non-root uid and gid.
+.ilist
+For local
+deliveries this is typically the uid and gid of the owner of the mailbox.
.next
-A delivery process retains root privilege throughout most of its execution,
-but any actual deliveries (that is, the transports themselves) are run in
-subprocesses which always change to a non-root uid and gid. For local
-deliveries this is typically the uid and gid of the owner of the mailbox; for
-remote deliveries, the Exim uid and gid are used. Once all the delivery
+For remote deliveries, the Exim uid and gid are used.
+.endlist
+
+Once all the delivery
subprocesses have been run, a delivery process changes to the Exim uid and gid
while doing post-delivery tidying up such as updating the retry database and
generating bounce and warning messages.
-While the recipient addresses in a message are being routed, the delivery
-process runs as root. However, if a user's filter file has to be processed,
-this is done in a subprocess that runs under the individual user's uid and
-gid. A system filter is run as root unless &%system_filter_user%& is set.
.next
A process that is testing addresses (the &%-bt%& option) runs as root so that
the routing is done in the same environment as a message delivery.
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.
-.new
However, signing options may not depend on headers modified by
routers, the transport or a transport filter.
-.wen
.next
Verifying signatures in incoming messages: This is implemented by an additional
ACL (acl_smtp_dkim), which can be called several times per message, with
openssl genrsa -out dkim_rsa.private 2048
openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM
.endd
-The result file from the first command should be retained, and
-this option set to use it.
+The result file from the first command should be retained,
+permissions set so that Exim can read it,
+and this option set to use it.
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.
.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.
-.new
Otherwise, must be an unsigned number giving an offset in seconds from the
current time for the expiry tag (e.g. 1209600 for two weeks); both creation
(t=) and expiry (x=) tags will be included unless the offset is 0 (no expiry).
-.wen
RFC 6376 lists these tags as RECOMMENDED.
ACL condition that checks a colon-separated list of possible DKIM verification
results against the actual result of verification,
given by &$dkim_verify_status$& if that is non-empty or "none" if empty.
-.new
This condition may be used in DKIM, MIME, PRDR and DATA ACLs.
-.wen
A basic verification might be:
.code
for more information of what they mean.
The condition is true if the status
-.new
(or any of the list of status values)
-.wen
is any one of the supplied list.
.endlist
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/).
+.new
+.cindex "dynamic modules"
+The support can be built as a dynamic-load module if desired;
+see the comments in that Makefile.
+.wen
+
There is no Exim involvement in the transmission of messages;
publishing certain DNS records is all that is required.
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/).
+should read and understand how it works by visiting the
+&url(http://www.dmarc.org/,DMARC website).
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/)
+&url(http://sourceforge.net/projects/opendmarc/,sourceforge)
to obtain a copy, or find it in your favorite package
repository. You will need to attend to the local/Makefile feature
SUPPORT_DMARC and the associated LDFLAGS addition.
.new
The current list of events is:
-.wen
.itable all 0 0 4 25* left 10* center 15* center 50* left
.row auth:fail after both "per driver per authentication attempt"
.row dane:fail after transport "per connection"
.row tls:fail:connect after main "per connection"
.row smtp:connect after transport "per connection"
.row smtp:ehlo after transport "per connection"
+.row smtp:fail:protocol after main "per connection"
+.row smtp:fail:syntax after main "per connection"
.endtable
+.wen
New event types may be added in future.
The event name is a colon-separated list, defining the type of
An additional variable, &$event_data$&, is filled with information varying
with the event type:
+.new
.itable all 0 0 2 20* left 80* left
.row auth:fail "smtp response"
.row dane:fail "failure reason"
.row tls:fail:connect "error string"
.row smtp:connect "smtp banner"
.row smtp:ehlo "smtp ehlo response"
+.row smtp:fail:protocol "error string"
+.row smtp:fail:syntax "error string"
.endtable
+.wen
The :defer events populate one extra variable: &$event_defer_errno$&.
For OpenSSL it will trigger for every chain element including those
loaded locally.
-.new
For dns:fail events from dnsdb lookups, a &"defer_never"& option does not
affect the reporting of DNS_AGAIN.
-.wen
. ////////////////////////////////////////////////////////////////////////////
. ////////////////////////////////////////////////////////////////////////////
git://git.exim.org / exim.git / blobdiff