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
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
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,
.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
domains = ! +local_domains
transport = remote_smtp
ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
+.ifdef _HAVE_DNSSEC
+ dnssec_request_domains = *
+.endif
no_more
.endd
The &%domains%& option behaves as per smarthost, above.
driver = smtp
message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
.ifdef _HAVE_DANE
- dnssec_request_domains = *
hosts_try_dane = *
.endif
.ifdef _HAVE_PRDR
The list of remote hosts comes from the router.
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 try to use DNSSEC for all queries and to use DANE for delivery;
+to use DANE for delivery;
see section &<<SECDANE>>& for more details.
The &%hosts_try_prdr%& option enables an efficiency SMTP option. It is
&*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
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)&.
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
returns the SHA-1 hash fingerprint of the certificate.
-.vitem &*${sha256:*&<&'string'&>&*}*&
+.vitem &*${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"
+.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.
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'&>&*}*&
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.
+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
.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
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 &$version_number$&
.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 "&$warn_message_delay$&"
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"
.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"
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&!!" $dkim_signers
.cindex DKIM "controlling calls to the ACL"
This option gives a list of DKIM domains for which the DKIM ACL is run.
This is a fudge to help with name servers that give big delays or otherwise do
not work for the AAAA record type. In due course, when the world's name
servers have all been upgraded, there should be no need for this option.
+.new
+Note that all lookups, including those done for verification, are affected;
+this will result in verify failure for IPv6 connections or ones using names
+only valid for IPv6 addresses.
+.wen
.option dns_retrans main time 0s
used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
+.option exim_version main string "current version"
+.cindex "Exim version"
+.cindex customizing "version number"
+.cindex "version number of Exim" override
+This option allows to override the &$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
&'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
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 +no_ticket"
+.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,
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.
+
+Currently the option name &"X_PIPE_CONNECT"& is used.
+.wen
+
.option prdr_enable main boolean false
.cindex "PRDR" "enabling on server"
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 set_environment main "string list" empty
+.option add_environment main "string list" empty
.cindex "environment"
-This option allows to set individual environment variables that the
+This option allows to add individual environment variables that the
currently linked libraries and programs in child processes use. The
-default list is empty,
+default list is empty.
.option slow_lookup_log main integer 0
.cindex "TLS" "server certificate; location of"
.cindex "certificate" "server, location of"
The value of this option is expanded, and must then be a list of absolute paths to
-files which contains the server's certificates. Commonly only one file is
-needed.
+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.
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.
+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
.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
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
.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
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"
.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
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
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
.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 options. For details see section &<<SECDKIMSIGN>>&.
+DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
.option delay_after_cutoff smtp boolean true
.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 "security" "MX lookup"
.cindex "DNS" "DNSSEC"
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.
+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.
+
+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.
-.option hosts_noproxy_tls smtp "host list&!!" *
+.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
.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.
+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>>&.
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&!!" unset
+.option hosts_try_dane smtp "host list&!!" *
.cindex DANE "transport options"
.cindex DANE "attempting for certain servers"
-If built with DANE support, Exim will lookup a
-TLSA record for any host matching the list.
-If found and verified by DNSSEC,
-a DANE-verified TLS connection is made to that host;
-there will be no fallback to in-clear communication.
+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&!!" unset
+.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"
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"
rather than being implicit for TLS-connection carried
client certificates only.
-The examples and discussion in this chapter assume that
+The examples and discussion in this chapter assume that
client-certificate authentication is being done.
The client must present a certificate,
-.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
attacks in the string (&`../`& or SQL), and ensuring that a valid filename
can always be referenced; it is important to remember that &$tls_in_sni$& is
arbitrary unverified data provided prior to authentication.
-Further, the initial certificate is loaded before SNI is arrived, so
+Further, the initial certificate is loaded before SNI has arrived, so
an expansion for &%tls_certificate%& must have a default which is used
when &$tls_in_sni$& is empty.
in &_Local/Makefile_&.
If it has been included, the macro "_HAVE_DANE" will be defined.
-The TLSA record for the server may have "certificate usage" of DANE-TA(2) or DANE-EE(3).
+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);
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 field of SPKI(1) and a Matching Type field of SHA2-512(2).
+The TLSA record should have a "Selector" (2nd) field of SPKI(1) and
+a "Matching Type" (3rd) field of SHA2-512(2).
-At the time of writing, &url(https://www.huque.com/bin/gen_tlsa)
-is useful for quickly generating TLSA records; and commands like
+For the "Certificate Authority Data" (4th) field, commands like
.code
- openssl x509 -in -pubkey -noout <certificate.pem \
+ openssl x509 -pubkey -noout <certificate.pem \
| openssl rsa -outform der -pubin 2>/dev/null \
| openssl sha512 \
| awk '{print $2}'
.endd
-are workable for 4th-field hashes.
+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).
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.
+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.
If DANE is not usable, whether requested or not, and CA-anchored
verification evaluation is wanted, the above variables should be set appropriately.
-Currently the &%dnssec_request_domains%& must be active and &%dnssec_require_domains%& is ignored.
+Currently the (router or transport options) &%dnssec_request_domains%& must be active 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".
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.
.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 "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(https://cr.yp.to/proto/verp.txt) &--
are a way of helping mailing list administrators discover which subscription
&`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
&` incoming_port `& remote port on <= lines
&`*lost_incoming_connection `& as it says (includes timeouts)
&` 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
&` outgoing_port `& add remote port to => lines
&`*queue_run `& start and end queue runs
&%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"
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"
.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:
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%&
.cindex "DKIM" "signing"
For signing to be usable you must have published a DKIM record in DNS.
-Note that RFC 8301 says:
+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 list&!! unset
The domain(s) you want to sign with.
After expansion, this can be a list.
-Each element in turn is put into the &%$dkim_domain%& expansion variable
+Each element in turn,
+.new
+lowercased,
+.wen
+is put into the &%$dkim_domain%& expansion variable
while expanding the remaining signing options.
If it is empty after expansion, DKIM signing is not done,
and no error will result even if &%dkim_strict%& is set.
Signers SHOULD use RSA keys of at least 2048 bits.
.endd
-Support for EC keys is being developed under
-&url(https://datatracker.ietf.org/doc/draft-ietf-dcrup-dkim-crypto/).
+.new
+EC keys for DKIM are defined by RFC 8463.
+.wen
They are considerably smaller than RSA keys for equivalent protection.
As they are a recent development, users should consider dual-signing
(by setting a list of selectors, and an expansion for this option)
certtool --load_privkey=dkim_ed25519.private --pubkey_info --outder | tail -c +13 | base64
.endd
-Note that the format
-of Ed25519 keys in DNS has not yet been decided; this release supports
-both of the leading candidates at this time, a future release will
-probably drop support for whichever proposal loses.
+.new
+Exim also supports an alternate format
+of Ed25519 keys in DNS which was a candidate during development
+of the standard, but not adopted.
+A future release will probably drop that support.
+.wen
.option dkim_hash smtp string&!! sha256
Can be set to any one of the supported hash methods, which are:
Verification of DKIM signatures in SMTP incoming email is done for all
messages for which an ACL control &%dkim_disable_verify%& has not been set.
+.new
+.cindex DKIM "selecting signature algorithms"
+Individual classes of signature algorithm can be ignored by changing
+the main options &%dkim_verify_hashes%& or &%dkim_verify_keytypes%&.
+The &%dkim_verify_minimal%& option can be set to cease verification
+processing for a message once the first passing signature is found.
+.wen
+
.cindex authentication "expansion item"
Performing verification sets up information used by the
&$authresults$& expansion item.
-The results of that verification are then made available to the
+.new
+For most purposes the default option settings suffice and the remainder
+of this section can be ignored.
+.wen
+
+The results of verification are made available to the
&%acl_smtp_dkim%& ACL, which can examine and modify them.
-By default, this ACL is called once for each
-syntactically(!) correct signature in the incoming message.
A missing ACL definition defaults to accept.
+By default, the ACL is called once for each
+syntactically(!) correct signature in the incoming message.
If any ACL call does not accept, the message is not accepted.
If a cutthrough delivery was in progress for the message, that is
summarily dropped (having wasted the transmission effort).
runtime of the ACL.
Calling the ACL only for existing signatures is not sufficient to build
-more advanced policies. For that reason, the global option
-&%dkim_verify_signers%&, and a global expansion variable
+more advanced policies. For that reason, the main option
+&%dkim_verify_signers%&, and an expansion variable
&%$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 &%$dkim_signers%& already contains a colon-separated
If a domain or identity is listed several times in the (expanded) value of
&%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
+.new
+Note that if the option is set using untrustworthy data
+(such as the From: header)
+care should be taken to force lowercase for domains
+and for the domain part if identities.
+The default setting can be regarded as trustworthy in this respect.
+.wen
+
If multiple signatures match a domain (or identity), the ACL is called once
for each matching signature.
-Inside the &%acl_smtp_dkim%&, the following expansion variables are
+Inside the DKIM ACL, the following expansion variables are
available (from most to least important):
algorithms (currently, rsa-sha1) have permanently failed evaluation
.endd
-To enforce this you must have a DKIM ACL which checks this variable
-and overwrites the &$dkim_verify_status$& variable as discussed above.
+To enforce this you must either have a DKIM ACL which checks this variable
+and overwrites the &$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'.
.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 as the database:
+address as the key and an IP address
+.new
+(v4 or v6)
+.wen
+as the database:
.code
${lookup {username@domain} spf {ip.ip.ip.ip}}
The lookup will return the same result strings as can appear in
&$spf_result$& (pass,fail,softfail,neutral,none,err_perm,err_temp).
-Currently, only IPv4 addresses are supported.
.endd
If &$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
git://git.exim.org / exim.git / blobdiff