Docs: more detail on log_file_path, in the main-config chapter

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

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index 5463cc1a52b8529389630f138da74b1bfc7bdde8..f7e930c083b45a2f9f1589270b0b789c88de4a09 100644 (file)
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -2528,6 +2528,8 @@ use of Exim's filtering capabilities, you should make the document entitled
 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
 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
 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


@@ -2766,9 +2768,12 @@ used to specify a path on the command line if a pid file is required.
 
 The SIGHUP signal
 .cindex "SIGHUP"
 
 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 "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
 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


@@ -6104,6 +6109,9 @@ dnslookup:
   domains = ! +local_domains
   transport = remote_smtp
   ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
   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.
   no_more
 .endd
 The &%domains%& option behaves as per smarthost, above.


@@ -6255,7 +6263,6 @@ remote_smtp:
   driver = smtp
   message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
 .ifdef _HAVE_DANE
   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
   hosts_try_dane = *
 .endif
 .ifdef _HAVE_PRDR


@@ -6266,7 +6273,7 @@ This transport is used for delivering messages over SMTP connections.
 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
 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
 see section &<<SECDANE>>& for more details.
 
 The &%hosts_try_prdr%& option enables an efficiency SMTP option.  It is


@@ -9214,7 +9221,13 @@ dependent upon the option for which a value is sought; in this documentation,
 options for which string expansion is performed are marked with &dagger; 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
 options for which string expansion is performed are marked with &dagger; 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

 
 
 
 
 
 


@@ -14336,7 +14349,9 @@ listed in more than one group.
 See also the &'Policy controls'& section above.
 
 .table2
 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 &%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"


@@ -15081,6 +15096,27 @@ etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
 to handle IPv6 literal addresses.
 
 
 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.
 .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.


@@ -16007,6 +16043,10 @@ when Exim is entered, so it can, for example, contain a reference to the host
 name. If no specific path is set for the log files at compile or 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.
 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
 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


@@ -16864,11 +16904,11 @@ it qualifies them only if the message came from a host that matches
 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
 using TCP/IP), and the &%-bnq%& option was not set.
 
 &%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"
 .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
 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
 
 
 .option slow_lookup_log main integer 0


@@ -17610,8 +17650,8 @@ is not required the &%tls_advertise_hosts%& option should be set empty.
 .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
 .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.
 The server's private key is also
 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
 &<<CHAPTLS>>& for further details.


@@ -18873,11 +18913,24 @@ latter kind.
 
 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
 
 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.
 
 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.
 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.


@@ -19011,13 +19064,12 @@ matters.
 .cindex router variables
 This option may be used multiple times on a router;
 because of this the list aspect is mostly irrelevant.
 .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 colon but can be changed in the
+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_"&.
 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 colons should either have them doubled, or
-the entire list should be prefixed with a list-separator change.
+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.
 When a router runs, the strings are evaluated in order,
 to create variables which are added to the set associated with
 the address.


@@ -22813,6 +22865,15 @@ sometimes add other information onto the ends of message filenames.
 
 Section &<<SECID136>>& contains further information.
 
 
 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 quota_warn_message appendfile string&!! "see below"
 See below for the use of this option. If it is not set when


@@ -24407,15 +24468,23 @@ of the message. Its value must not be zero. See also &%final_timeout%&.
 
 
 .option dkim_canon smtp string&!! unset
 
 
 .option dkim_canon smtp string&!! unset

+DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.

 .option dkim_domain smtp string list&!! unset
 .option dkim_domain smtp string list&!! unset

+DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.

 .option dkim_hash smtp string&!! sha256
 .option dkim_hash smtp string&!! sha256

+DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.

 .option dkim_identity smtp string&!! unset
 .option dkim_identity smtp string&!! unset

+DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.

 .option dkim_private_key smtp string&!! unset
 .option dkim_private_key smtp string&!! unset

+DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.

 .option dkim_selector smtp string&!! unset
 .option dkim_selector smtp string&!! unset

+DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.

 .option dkim_strict smtp string&!! unset
 .option dkim_strict smtp string&!! unset

+DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.

 .option dkim_sign_headers smtp string&!! "per RFC"
 .option dkim_sign_headers smtp string&!! "per RFC"

+DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.

 .option dkim_timestamps smtp string&!! unset
 .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
 
 
 .option delay_after_cutoff smtp boolean true


@@ -24463,8 +24532,9 @@ details.
 .cindex "security" "MX lookup"
 .cindex "DNS" "DNSSEC"
 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
 .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.

 
 
 
 
 
 


@@ -24474,9 +24544,9 @@ This applies to all of the SRV, MX, AAAA, A lookup sequence.
 .cindex "security" "MX lookup"
 .cindex "DNS" "DNSSEC"
 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
 .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.

 
 
 
 
 
 


@@ -24755,7 +24825,8 @@ TLS session for any host that matches this list.
 .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,
 .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>>&.
 
 There will be no fallback to in-clear communication.
 See section &<<SECDANE>>&.
 


@@ -24791,11 +24862,11 @@ BDAT will not be used in conjunction with a transport filter.
 .option hosts_try_dane smtp "host list&!!" *
 .cindex DANE "transport options"
 .cindex DANE "attempting for certain servers"
 .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&!!" *
 See section &<<SECDANE>>&.
 
 .option hosts_try_fastopen smtp "host list&!!" *


@@ -28478,6 +28549,13 @@ transport provide the client with a certificate, which is passed to the server
 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.
 
 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
 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
 specifies a collection of expected server certificates.
 These may be


@@ -28601,7 +28679,7 @@ Great care should be taken to deal with matters of case, various injection
 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
 can always be referenced; it is important to remember that &$tls_in_sni$& is
 arbitrary unverified data provided prior to authentication.
 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.
 
 an expansion for &%tls_certificate%& must have a default which is used
 when &$tls_in_sni$& is empty.
 


@@ -28796,7 +28874,12 @@ Support for client-side operation of DANE can be included at compile time by def
 in &_Local/Makefile_&.
 If it has been included, the macro "_HAVE_DANE" will be defined.
 
 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);
 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);


@@ -28837,19 +28920,29 @@ If you're not already using a private CA, or it doesn't meet these
 requirements, then we encourage you to avoid all these issues and use a public
 CA such as &url(https://letsencrypt.org/,Let's Encrypt) instead.
 
 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
 
 .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
 
   | 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 use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName).
 


@@ -28883,7 +28976,9 @@ those who use &%hosts_require_ocsp%&, should consider the interaction with DANE
 
 For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%&
 and &%dane_require_tls_ciphers%&.
 
 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.
 
 
 DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
 


@@ -28913,7 +29008,7 @@ If DANE is requested and useable (see above) the following transport options are
 If DANE is not usable, whether requested or not, and CA-anchored
 verification evaluation is wanted, the above variables should be set appropriately.
 
 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".
 
 
 If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane".
 


@@ -39532,6 +39627,11 @@ was received from the client, this records the Distinguished Name from that
 certificate.
 .endlist
 
 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%&
 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%&


@@ -39878,15 +39978,28 @@ RFC 6376 lists these tags as RECOMMENDED.
 
 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.
 
 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.
 
 .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.
 &%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.
 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).
 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).


@@ -39897,11 +40010,11 @@ containing the signature status and its details are set up during the
 runtime of the ACL.
 
 Calling the ACL only for existing signatures is not sufficient to build
 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.
 
 &%$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 &%$dkim_signers%& already contains a colon-separated
 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
 called. It is expanded when the message has been received. At this point,
 the expansion variable &%$dkim_signers%& already contains a colon-separated


@@ -39939,7 +40052,7 @@ If multiple signatures match a domain (or identity), the ACL is called once
 for each matching signature.
 
 
 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):
 
 
 available (from most to least important):
 
 


@@ -40033,8 +40146,12 @@ DKIM signatures identified as having been signed with historic
 algorithms (currently, rsa-sha1) have permanently failed evaluation
 .endd
 
 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'.
 
 .vitem &%$dkim_canon_body%&
 The body canonicalization method. One of 'relaxed' or 'simple'.


@@ -40301,7 +40418,11 @@ would relax host matching rules to a broader network range.
 .cindex SPF "lookup expansion"
 .cindex lookup spf
 A lookup expansion is also available. It takes an email
 .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}}
 
 .code
   ${lookup {username@domain} spf {ip.ip.ip.ip}}


@@ -40309,7 +40430,6 @@ address as the key and an IP address as the database:
 
 The lookup will return the same result strings as can appear in
 &$spf_result$& (pass,fail,softfail,neutral,none,err_perm,err_temp).
 
 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.