Debug: more detail in dkim processing

[users/heiko/exim.git] / doc / doc-docbook / spec.xfpt

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index aa6da73d3bed0422741f26e0f891ae9da8e8a773..2c783d700ed5982bf8541a0f22d9af78517594b1 100644 (file)
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -3162,6 +3162,10 @@ 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.
 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.

+.new
+For the "-bP macro <name>" form, if no such macro is found
+the exit status will be nonzero.
+.wen

 
 .vitem &%-bp%&
 .oindex "&%-bp%&"
 
 .vitem &%-bp%&
 .oindex "&%-bp%&"


@@ -5579,19 +5583,27 @@ Another two commented-out option settings follow:
 .cindex "port" "465 and 587"
 .cindex "port" "for message submission"
 .cindex "message" "submission, ports for"
 .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 "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
 .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
 
 Two more commented-out options settings follow:
 .code


@@ -9337,7 +9349,7 @@ 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
 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.
 .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.


@@ -10637,7 +10649,11 @@ 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
 with 256 being the default.
 
 The &%sha3%& expansion item is only supported if Exim has been

-compiled with GnuTLS 3.5.0 or later.
+compiled with GnuTLS 3.5.0 or later,
+.new
+or OpenSSL 1.1.1 or later.
+The macro "_CRYPTO_HASH_SHA3" will be defined if it is supported.
+.wen

 
 
 .vitem &*${stat:*&<&'string'&>&*}*&
 
 
 .vitem &*${stat:*&<&'string'&>&*}*&


@@ -11659,7 +11675,7 @@ contain the trailing slash. If &$config_file$& does not contain a slash,
 .vindex "&$config_file$&"
 The name of the main configuration file Exim is using.
 
 .vindex "&$config_file$&"
 The name of the main configuration file Exim is using.
 

-.vitem &$dkim_verify_status$& &&&
+.vitem &$dkim_verify_status$&

 Results of DKIM verification.
 For details see section &<<SECDKIMVFY>>&.
 
 Results of DKIM verification.
 For details see section &<<SECDKIMVFY>>&.
 


@@ -13408,23 +13424,32 @@ value of &%daemon_smtp_ports%& is no longer relevant in this example.)
 
 
 
 
 
 

-.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"
 .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
 .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
 
 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
 daemon to listen on those ports. You must still specify them in


@@ -14693,6 +14718,7 @@ If the resolver library does not support DNSSEC then this option has no effect.
 .option dns_ipv4_lookup main "domain list&!!" unset
 .cindex "IPv6" "DNS lookup for AAAA records"
 .cindex "DNS" "IPv6 lookup for AAAA records"
 .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
 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


@@ -16898,8 +16924,8 @@ and any external programs which are passed a reference to a message data file
 will need to be aware of the potential different format.
 
 Using any of the ACL conditions noted will negate the reception benefit
 will need to be aware of the potential different format.
 
 Using any of the ACL conditions noted will negate the reception benefit

-(as a Unix-mbox-format file is contructed for them).
-The transimssion benefit is maintained.
+(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"
 
 .option sqlite_lock_timeout main time 5s
 .cindex "sqlite lookup type" "lock timeout"


@@ -17126,7 +17152,7 @@ option in the relevant &(smtp)& transport.
 separator in the usual way to avoid confusion under IPv6.
 
 &*Note*&: Under current versions of OpenSSL, when a list of more than one
 separator in the usual way to avoid confusion under IPv6.
 
 &*Note*&: Under current versions of OpenSSL, when a list of more than one

-file is used, the &$tls_in_ourcert$& veriable is unreliable.
+file is used, the &$tls_in_ourcert$& variable is unreliable.

 
 &*Note*&: OCSP stapling is not usable under OpenSSL
 when a list of more than one file is used.
 
 &*Note*&: OCSP stapling is not usable under OpenSSL
 when a list of more than one file is used.


@@ -18745,7 +18771,9 @@ records.
 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,
 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
+.new
+except that IPv6 addresses are sorted before IPv4 addresses. If all the
+.wen

 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
 generic option, the router declines.
 
 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
 generic option, the router declines.
 


@@ -18878,6 +18906,24 @@ However, it will result in any message with mistyped domains
 also being queued.
 
 
 also being queued.
 
 

+.new
+.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).
+.wen
+

 .option mx_domains dnslookup "domain list&!!" unset
 .cindex "MX record" "required to exist"
 .cindex "SRV record" "required to exist"
 .option mx_domains dnslookup "domain list&!!" unset
 .cindex "MX record" "required to exist"
 .cindex "SRV record" "required to exist"


@@ -19482,8 +19528,8 @@ whether obtained from an MX lookup or not.
 
 
 .section "How the options are used" "SECThowoptused"
 
 
 .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
 &%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


@@ -19503,6 +19549,12 @@ also look in &_/etc/hosts_& or other sources of information.
 &%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.
 &%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.

+.new
+.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.
+.wen

 .endlist
 
 For example:
 .endlist
 
 For example:


@@ -24195,7 +24247,7 @@ 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
 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 enebled.  Note that legthy operations in the connect ACL,
+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&!!" *
 such as DNSBL lookups, will still delay the emission of the SMTP banner.
 
 .option hosts_try_prdr smtp "host list&!!" *


@@ -27057,22 +27109,36 @@ in order to get TLS to work.
 
 
 
 
 
 

-.section "Support for the legacy &""ssmtp""& (aka &""smtps""&) protocol" &&&
+.section "Support for the &""submissions""& (aka &""ssmtp""& and &""smtps""&) protocol" &&&

          "SECID284"
          "SECID284"

+.cindex "submissions protocol"

 .cindex "ssmtp protocol"
 .cindex "smtps protocol"
 .cindex "ssmtp protocol"
 .cindex "smtps protocol"

+.cindex "SMTP" "submissions protocol"

 .cindex "SMTP" "ssmtp protocol"
 .cindex "SMTP" "smtps 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
+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 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
 .code
 tls_on_connect_ports = 465
 .endd


@@ -27084,7 +27150,7 @@ an extra port &-- rather, it specifies different behaviour on a port that is
 defined elsewhere.
 
 There is also a &%-tls-on-connect%& command line option. This overrides
 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.

 
 
 
 
 
 


@@ -27363,8 +27429,8 @@ tls_require_ciphers = ${if =={$received_port}{25}\
 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 *, which means
 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 *, which means

-that STARTTLS is alway advertised.  Set it to blank to never advertise;
-this is reasonble for systems that want to use TLS only as a client.
+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 STARTTLS is to be used you
 need to set some other options in order to make TLS available.


@@ -27797,7 +27863,7 @@ 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
 
 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 descibed above is not used; instead Exim
+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
 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


@@ -28244,8 +28310,8 @@ acl_smtp_rcpt = ${if ={25}{$interface_port} \
                      {acl_check_rcpt} {acl_check_rcpt_submit} }
 .endd
 In the default configuration file there are some example settings for
                      {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.
 
 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.
 


@@ -31073,7 +31139,7 @@ This option applies to recipient callouts only. For example:
 .code
 require  verify = recipient/callout=use_sender,hold
 .endd
 .code
 require  verify = recipient/callout=use_sender,hold
 .endd

-It causes the connection to be helod open and used for any further recipients
+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.
 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.


@@ -32302,7 +32368,7 @@ All parts contained within an attachment multipart are attachments.
 
 As an example, the following will ban &"HTML mail"& (including that sent with
 alternative plain text), while allowing HTML files to be attached. HTML
 
 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
 .code
 deny message = HTML mail is not accepted here
 !condition = $mime_is_rfc822


@@ -36077,6 +36143,7 @@ the following table:
 &`    `&        on &"Completed"& lines: time spent on queue
 &`R   `&        on &`<=`& lines: reference for local bounce
 &`    `&        on &`=>`&  &`>>`& &`**`& and &`==`& lines: router name
 &`    `&        on &"Completed"& lines: time spent on queue
 &`R   `&        on &`<=`& lines: reference for local bounce
 &`    `&        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
 &`S   `&        size of message in bytes
 &`SNI `&        server name indication from TLS client hello
 &`ST  `&        shadow transport name


@@ -36171,7 +36238,7 @@ selection marked by asterisks:
 &` incoming_interface         `&  local interface on <= and => lines
 &` incoming_port              `&  remote port on <= lines
 &`*lost_incoming_connection   `&  as it says (includes timeouts)
 &` incoming_interface         `&  local interface on <= and => lines
 &` incoming_port              `&  remote port on <= lines
 &`*lost_incoming_connection   `&  as it says (includes timeouts)

-&` millisec                   `&  millisecond timestamps and QT,DT,D times
+&` millisec                   `&  millisecond timestamps and RT,QT,DT,D times

 &` outgoing_interface         `&  local interface on => lines
 &` outgoing_port              `&  add remote port to => lines
 &`*queue_run                  `&  start and end queue runs
 &` outgoing_interface         `&  local interface on => lines
 &` outgoing_port              `&  add remote port to => lines
 &`*queue_run                  `&  start and end queue runs


@@ -36262,7 +36329,7 @@ process is started because &%queue_only%& is set or &%-odq%& was used.
 &%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
 &%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=0.304`&.
+precision, eg. &`DT=0.304s`&.

 .next
 .cindex "log" "message size on delivery"
 .cindex "size" "of message"
 .next
 .cindex "log" "message size on delivery"
 .cindex "size" "of message"


@@ -36272,7 +36339,7 @@ the &"=>"& line, tagged with S=.
 .new
 .cindex log "DKIM verification"
 .cindex DKIM "verification logging"
 .new
 .cindex log "DKIM verification"
 .cindex DKIM "verification logging"

-&%dkim%&: For message acceptance log lines, when an DKIM signture in the header
+&%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"
 verifies successfully a tag of DKIM is added, with one of the verified domains.
 .next
 .cindex log "DKIM verification"


@@ -36351,7 +36418,7 @@ connection is unexpectedly dropped.
 .next
 .cindex "log" "millisecond timestamps"
 .cindex millisecond logging
 .next
 .cindex "log" "millisecond timestamps"
 .cindex millisecond logging

-.cindex timstamps "millisecond, in logs"
+.cindex timestamps "millisecond, in logs"

 &%millisec%&: Timestamps have a period and three decimal places of finer granularity
 appended to the seconds value.
 .next
 &%millisec%&: Timestamps have a period and three decimal places of finer granularity
 appended to the seconds value.
 .next


@@ -36366,7 +36433,7 @@ followed by IP address in square brackets. You can disable this by turning
 off the &%outgoing_interface%& option.
 .next
 .cindex "log" "outgoing remote port"
 off the &%outgoing_interface%& option.
 .next
 .cindex "log" "outgoing remote port"

-.cindex "port" "logging outgoint remote"
+.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.
 .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.


@@ -36400,6 +36467,14 @@ precision, eg. &`QT=1.578s`&.
 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.
 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.

+.new
+.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`&.
+.wen

 .next
 .cindex "log" "recipients"
 &%received_recipients%&: The recipients of a message are listed in the main log
 .next
 .cindex "log" "recipients"
 &%received_recipients%&: The recipients of a message are listed in the main log


@@ -38524,7 +38599,7 @@ There is no dot-stuffing (and no dot-termination).
 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 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.

 
 .new
 As DKIM relies on the message being unchanged in transit, messages handled
 
 .new
 As DKIM relies on the message being unchanged in transit, messages handled


@@ -38551,8 +38626,12 @@ In typical Exim style, the verification implementation does not include any
 default "policy". Instead it enables you to build your own policy using
 Exim's standard controls.
 
 default "policy". Instead it enables you to build your own policy using
 Exim's standard controls.
 

+.new

 Please note that verification of DKIM signatures in incoming mail is turned
 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
 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


@@ -38561,6 +38640,8 @@ signature status. Here is an example (with line-breaks added for clarity):
     c=relaxed/relaxed a=rsa-sha1
     i=@facebookmail.com t=1252484542 [verification succeeded]
 .endd
     c=relaxed/relaxed a=rsa-sha1
     i=@facebookmail.com t=1252484542 [verification succeeded]
 .endd

+.wen
+

 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
 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


@@ -38571,6 +38652,23 @@ senders).
 .section "Signing outgoing messages" "SECDKIMSIGN"
 .cindex "DKIM" "signing"
 
 .section "Signing outgoing messages" "SECDKIMSIGN"
 .cindex "DKIM" "signing"
 

+.new
+For signing to be usable you must have published a DKIM record in DNS.
+Note that RFC 8301 says:
+.code
+rsa-sha1 MUST NOT be used for signing or verifying.
+
+Signers MUST use RSA keys of at least 1024 bits for all keys.
+Signers SHOULD use RSA keys of at least 2048 bits.
+.endd
+
+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.
+.wen
+

 Signing is enabled by setting private options on the SMTP transport.
 These options take (expandable) strings as arguments.
 
 Signing is enabled by setting private options on the SMTP transport.
 These options take (expandable) strings as arguments.
 


@@ -38579,7 +38677,8 @@ The domain(s) you want to sign with.
 After expansion, this can be a list.
 Each element in turn is put into the &%$dkim_domain%& expansion variable
 while expanding the remaining signing options.
 After expansion, this can be a list.
 Each element in turn is put into the &%$dkim_domain%& expansion variable
 while expanding the remaining signing options.

-If it is empty after expansion, DKIM signing is not done.
+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.
 
 .option dkim_selector smtp string list&!! unset
 This sets the key selector string.


@@ -38587,7 +38686,8 @@ 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%&.
 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.
+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
 This sets the private key to use.
 
 .option dkim_private_key smtp string&!! unset
 This sets the private key to use.


@@ -38595,20 +38695,47 @@ You can use the &%$dkim_domain%& and
 &%$dkim_selector%& expansion variables to determine the private key to use.
 The result can either
 .ilist
 &%$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
+.new
+.next
+with GnuTLS 3.6.0 or later, be a valid Ed25519 private key (same format as above)
+.wen

 .next
 start with a slash, in which case it is treated as a file that contains
 .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
 .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

-If the option is empty after expansion, DKIM signing is not done.
+
+.new
+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
+
+Support for EC keys is being developed under
+&url(https://datatracker.ietf.org/doc/draft-ietf-dcrup-dkim-crypto/).
+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.
+.wen

 
 .option dkim_hash smtp string&!! sha256
 Can be set alternatively to &"sha1"& to use an alternate hash
 
 .option dkim_hash smtp string&!! sha256
 Can be set alternatively to &"sha1"& to use an alternate hash

-method.  Note that sha1 is now condidered insecure, and deprecated.
+method.
+
+.new
+Note that RFC 8301 says:
+.code
+rsa-sha1 MUST NOT be used for signing or verifying.
+.endd
+.wen

 
 .option dkim_identity smtp string&!! unset
 If set after expansion, the value is used to set an "i=" tag in
 
 .option dkim_identity smtp string&!! unset
 If set after expansion, the value is used to set an "i=" tag in


@@ -38640,7 +38767,7 @@ whether or not each header is present in the message.
 The default list is available for the expansion in the macro
 "_DKIM_SIGN_HEADERS".
 
 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 therof)
+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.
 
 will be signed.  The textually later headers in the headers part of the
 message are signed first, if there are multiples.
 


@@ -38648,7 +38775,7 @@ 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
 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 signtature added for a missing header with the
+will be signed, and one signature added for a missing header with the

 name will be appended.
 
 
 name will be appended.
 
 


@@ -38762,7 +38889,7 @@ 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
 
 DKIM verification. It may of course also mean that the signature is forged.
 .endlist
 

-This variable can be overwritten using an ACL 'set' modifier.
+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
 
 .vitem &%$dkim_domain%&
 The signing domain. IMPORTANT: This variable is only populated if there is


@@ -38779,6 +38906,24 @@ The key record selector string.
 
 .vitem &%$dkim_algo%&
 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
 
 .vitem &%$dkim_algo%&
 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.

+.new
+If running under GnuTLS 3.6.0 or later, may also be 'ed25519-sha256'.
+The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
+for EC keys.
+.wen
+
+.new
+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 have a DKIM ACL which checks this variable
+and overwrites the &$dkim_verify_status$& variable as discussed above.
+.wen

 
 .vitem &%$dkim_canon_body%&
 The body canonicalization method. One of 'relaxed' or 'simple'.
 
 .vitem &%$dkim_canon_body%&
 The body canonicalization method. One of 'relaxed' or 'simple'.


@@ -38830,6 +38975,18 @@ Notes from the key record (tag n=).
 
 .vitem &%$dkim_key_length%&
 Number of bits in the key.
 
 .vitem &%$dkim_key_length%&
 Number of bits in the key.

+
+.new
+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.
+.wen
+

 .endlist
 
 In addition, two ACL conditions are provided:
 .endlist
 
 In addition, two ACL conditions are provided:


@@ -39295,7 +39452,7 @@ the "headers charset" command (in a filter file)
 or &%headers_charset%& main configuration option (otherwise),
 to the
 modified UTF-7 encoding specified by RFC 2060,
 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.
 (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.


@@ -39381,7 +39538,7 @@ The second column in the table above describes whether the event fires
 before or after the action is associates with.  Those which fire before
 can be used to affect that action (more on this below).
 
 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 configumration
+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
 should define the event action.
 
 An additional variable, &$event_data$&, is filled with information varying