Docs: more subsections

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

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index 902f8e72f2e7f9748fae66977bbbec8e84f91d56..3da27cdea67e53842a79c010f764b6df97576499 100644 (file)
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -1,4 +1,3 @@
-

 . /////////////////////////////////////////////////////////////////////////////
 . This is the primary source of the Exim Manual. It is an xfpt document that is
 . converted into DocBook XML for subsequent conversion into printable and online
 . /////////////////////////////////////////////////////////////////////////////
 . This is the primary source of the Exim Manual. It is an xfpt document that is
 . converted into DocBook XML for subsequent conversion into printable and online


@@ -46,7 +45,7 @@
 . Update the Copyright year (only) when changing content.
 . /////////////////////////////////////////////////////////////////////////////
 
 . Update the Copyright year (only) when changing content.
 . /////////////////////////////////////////////////////////////////////////////
 

-.set previousversion "4.97"
+.set previousversion "4.98"

 .include ./local_params
 
 .set ACL "access control lists (ACLs)"
 .include ./local_params
 
 .set ACL "access control lists (ACLs)"


@@ -55,7 +54,7 @@
 .set drivernamemax "64"
 
 .macro copyyear
 .set drivernamemax "64"
 
 .macro copyyear

-2023
+2024

 .endmacro
 
 . /////////////////////////////////////////////////////////////////////////////
 .endmacro
 
 . /////////////////////////////////////////////////////////////////////////////


@@ -447,7 +446,7 @@ website, are hosted at the University of Cambridge.
 .cindex "FAQ"
 As well as Exim distribution tar files, the Exim website contains a number of
 differently formatted versions of the documentation. A recent addition to the
 .cindex "FAQ"
 As well as Exim distribution tar files, the Exim website contains a number of
 differently formatted versions of the documentation. A recent addition to the

-online information is the Exim wiki (&url(https://wiki.exim.org)),
+online information is &url(https://wiki.exim.org,the Exim wiki),

 which contains what used to be a separate FAQ, as well as various other
 examples, tips, and know-how that have been contributed by Exim users.
 The wiki site should always redirect to the correct place, which is currently
 which contains what used to be a separate FAQ, as well as various other
 examples, tips, and know-how that have been contributed by Exim users.
 The wiki site should always redirect to the correct place, which is currently


@@ -488,7 +487,7 @@ lists.
 .cindex "bug reports"
 .cindex "reporting bugs"
 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
 .cindex "bug reports"
 .cindex "reporting bugs"
 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported

-via the Bugzilla (&url(https://bugs.exim.org)). However, if you are unsure
+via &url(https://bugs.exim.org,the Bugzilla). However, if you are unsure

 whether some behaviour is a bug or not, the best thing to do is to post a
 message to the &'exim-dev'& mailing list and have it discussed.
 
 whether some behaviour is a bug or not, the best thing to do is to post a
 message to the &'exim-dev'& mailing list and have it discussed.
 


@@ -578,7 +577,8 @@ distribution, and are also available in &_.bz2_& and &_.xz_& forms.
 .cindex "limitations of Exim"
 .cindex "bang paths" "not handled by Exim"
 Exim is designed for use as an Internet MTA, and therefore handles addresses in
 .cindex "limitations of Exim"
 .cindex "bang paths" "not handled by Exim"
 Exim is designed for use as an Internet MTA, and therefore handles addresses in

-RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+domain format only. It cannot handle UUCP &"bang paths"&, though

 simple two-component bang paths can be converted by a straightforward rewriting
 configuration. This restriction does not prevent Exim from being interfaced to
 UUCP as a transport mechanism, provided that domain addresses are used.
 simple two-component bang paths can be converted by a straightforward rewriting
 configuration. This restriction does not prevent Exim from being interfaced to
 UUCP as a transport mechanism, provided that domain addresses are used.


@@ -690,7 +690,8 @@ line.
 
 .cindex "local part" "definition of"
 .cindex "domain" "definition of"
 
 .cindex "local part" "definition of"
 .cindex "domain" "definition of"

-The term &'local part'&, which is taken from RFC 2822, is used to refer to the
+The term &'local part'&, which is taken from
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822), is used to refer to the

 part of an email address that precedes the @ sign. The part that follows the
 @ sign is called the &'domain'& or &'mail domain'&.
 
 part of an email address that precedes the @ sign. The part that follows the
 @ sign is called the &'domain'& or &'mail domain'&.
 


@@ -953,7 +954,7 @@ of filtering are available:
 
 .ilist
 Sieve filters are written in the standard filtering language that is defined
 
 .ilist
 Sieve filters are written in the standard filtering language that is defined

-by RFC 3028.
+by &url(https://www.rfc-editor.org/rfc/rfc3028.html,RFC 3028).

 .next
 Exim filters are written in a syntax that is unique to Exim, but which is more
 powerful than Sieve, which it pre-dates.
 .next
 Exim filters are written in a syntax that is unique to Exim, but which is more
 powerful than Sieve, which it pre-dates.


@@ -1765,6 +1766,12 @@ distributors have chosen to bundle different libraries with their packaged
 versions. However, the more recent releases seem to have standardized on the
 Berkeley DB library.
 
 versions. However, the more recent releases seem to have standardized on the
 Berkeley DB library.
 

+.new
+Ownership of the Berkeley DB library has moved to a major corporation;
+development seems to have stalled and documentation is not freely available.
+This is probably not tenable for the long term use by Exim.
+.wen
+

 Different DBM libraries have different conventions for naming the files they
 use. When a program opens a file called &_dbmfile_&, there are several
 possibilities:
 Different DBM libraries have different conventions for naming the files they
 use. When a program opens a file called &_dbmfile_&, there are several
 possibilities:


@@ -1805,6 +1812,9 @@ suited to Exim's usage model.
 Yet another DBM library, called &'tdb'&, is available from
 &url(https://sourceforge.net/projects/tdb/files/). It has its own interface, and also
 operates on a single file.
 Yet another DBM library, called &'tdb'&, is available from
 &url(https://sourceforge.net/projects/tdb/files/). It has its own interface, and also
 operates on a single file.

+.next
+It is possible to use &url(https://www.sqlite.org/index.html,sqlite3)
+for the DBM library.

 .endlist
 
 .cindex "USE_DB"
 .endlist
 
 .cindex "USE_DB"


@@ -1816,8 +1826,9 @@ USE_DB in an appropriate configuration file (typically
 .code
 USE_DB=yes
 .endd
 .code
 USE_DB=yes
 .endd

-Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
-error is diagnosed if you set more than one of these.
+Similarly, for gdbm you set USE_GDBM, for tdb you set USE_TDB,
+and for sqlite3 you set USE_SQLITE.
+An error is diagnosed if you set more than one of these.

 You can set USE_NDBM if needed to override an operating system default.
 
 At the lowest level, the build-time configuration sets none of these options,
 You can set USE_NDBM if needed to override an operating system default.
 
 At the lowest level, the build-time configuration sets none of these options,


@@ -1833,6 +1844,7 @@ in one of these lines:
 .code
 DBMLIB = -ldb
 DBMLIB = -ltdb
 .code
 DBMLIB = -ldb
 DBMLIB = -ltdb

+DBMLIB = -lsqlite3

 DBMLIB = -lgdbm -lgdbm_compat
 .endd
 The last of those was for a Linux having GDBM provide emulated NDBM facilities.
 DBMLIB = -lgdbm -lgdbm_compat
 .endd
 The last of those was for a Linux having GDBM provide emulated NDBM facilities.


@@ -1848,6 +1860,17 @@ DBMLIB=/usr/local/lib/db-4.1/libdb.a
 There is further detailed discussion about the various DBM libraries in the
 file &_doc/dbm.discuss.txt_& in the Exim distribution.
 
 There is further detailed discussion about the various DBM libraries in the
 file &_doc/dbm.discuss.txt_& in the Exim distribution.
 

+.new
+When moving from one DBM library to another,
+for the hints databases it suffices to just remove all the files in the
+directory named &"db/"& under the spool directory.
+This is because hints are only for optimisation and will be rebuilt
+during normal operations.
+Non-hints DBM databases (used by &"dbm"& lookups in the configuration)
+will need individual rebuilds for the new DBM library.
+This is not done automatically
+.wen
+

 
 
 .section "Pre-building configuration" "SECID25"
 
 
 .section "Pre-building configuration" "SECID25"


@@ -1910,7 +1933,8 @@ do this.
 .cindex "&[iconv()]& support"
 .cindex "RFC 2047"
 The contents of header lines in messages may be encoded according to the rules
 .cindex "&[iconv()]& support"
 .cindex "RFC 2047"
 The contents of header lines in messages may be encoded according to the rules

-described RFC 2047. This makes it possible to transmit characters that are not
+described in &url(https://www.rfc-editor.org/rfc/rfc2047,RFC 2047).
+This makes it possible to transmit characters that are not

 in the ASCII character set, and to label them as being in a particular
 character set. When Exim is inspecting header lines by means of the &%$h_%&
 mechanism, it decodes them, and translates them into a specified character set
 in the ASCII character set, and to label them as being in a particular
 character set. When Exim is inspecting header lines by means of the &%$h_%&
 mechanism, it decodes them, and translates them into a specified character set


@@ -1935,7 +1959,8 @@ to your &_Local/Makefile_& and rebuild Exim.
 .cindex "OpenSSL" "building Exim with"
 .cindex "GnuTLS" "building Exim with"
 Exim is usually built to support encrypted SMTP connections, using the STARTTLS
 .cindex "OpenSSL" "building Exim with"
 .cindex "GnuTLS" "building Exim with"
 Exim is usually built to support encrypted SMTP connections, using the STARTTLS

-command as per RFC 2487. It can also support clients that expect to
+command as per &url(https://www.rfc-editor.org/rfc/rfc2487,RFC 2487).
+It can also support clients that expect to

 start a TLS session immediately on connection to a non-standard port (see the
 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
 line option).
 start a TLS session immediately on connection to a non-standard port (see the
 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
 line option).


@@ -2048,19 +2073,29 @@ withdrawn.
 
 
 
 
 
 

-.section "Dynamically loaded lookup module support" "SECTdynamicmodules"
+.section "Dynamically loaded module support" "SECTdynamicmodules"

 .cindex "lookup modules"
 .cindex "lookup modules"

+.cindex "router modules"
+.cindex "transport modules"
+.cindex "authenticator modules"

 .cindex "dynamic modules"
 .cindex ".so building"
 On some platforms, Exim supports not compiling all lookup types directly into
 the main binary, instead putting some into external modules which can be loaded
 on demand.
 This permits packagers to build Exim with support for lookups with extensive
 .cindex "dynamic modules"
 .cindex ".so building"
 On some platforms, Exim supports not compiling all lookup types directly into
 the main binary, instead putting some into external modules which can be loaded
 on demand.
 This permits packagers to build Exim with support for lookups with extensive

-library dependencies without requiring all users to install all of those
+library dependencies without requiring all systems to install all of those

 dependencies.
 dependencies.

-Most, but not all, lookup types can be built this way.
+.new
+Any combination of lookup types can be built this way.
+Lookup types that provide several variants will be loaded as
+Exim starts.
+Types that provide only one method are not loaded until used by
+the runtime configuration.
+.wen

 
 

-Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
+For building
+set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be

 installed; Exim will only load modules from that directory, as a security
 measure.  You will need to set &`CFLAGS_DYNAMIC`& if not already defined
 for your OS; see &_OS/Makefile-Linux_& for an example.
 installed; Exim will only load modules from that directory, as a security
 measure.  You will need to set &`CFLAGS_DYNAMIC`& if not already defined
 for your OS; see &_OS/Makefile-Linux_& for an example.


@@ -2070,12 +2105,25 @@ see &_src/EDITME_& for details.
 Then, for each module to be loaded dynamically, define the relevant
 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
 For example, this will build in lsearch but load sqlite and mysql support
 Then, for each module to be loaded dynamically, define the relevant
 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
 For example, this will build in lsearch but load sqlite and mysql support

-on demand:
+only if each is installed:

 .code
 LOOKUP_LSEARCH=yes
 LOOKUP_SQLITE=2
 LOOKUP_MYSQL=2
 .endd
 .code
 LOOKUP_LSEARCH=yes
 LOOKUP_SQLITE=2
 LOOKUP_MYSQL=2
 .endd

+Set also &`LOOKUP_`&<&'lookup_type'&>&` INCLUDE`& and
+&`LOOKUP_`&<&'lookup_type'&>`_LIBS if needed for each lookup type,
+ensuring that duplicates are not present in more global values.
+
+.new
+Similarly, authenticator, router and transport drivers can be built
+as external modules.
+Modules will be searched for as demanded by the runtime configuration,
+permitting a smaller Exim binary.
+
+For building, as above but using
+&`AUTH_*`&, &`ROUTER_*`& and &`TRANSPORT_*`& instead of &`LOOKUP_*`&,
+.wen

 
 
 .section "The building process" "SECID29"
 
 
 .section "The building process" "SECID29"


@@ -2886,6 +2934,9 @@ available to admin users.
 
 The word &"set"& at the start of a line, followed by a single space,
 is recognised specially as defining a value for a variable.
 
 The word &"set"& at the start of a line, followed by a single space,
 is recognised specially as defining a value for a variable.

+.cindex "tainted data" "expansion testing"
+If the sequence &",t"& is inserted before the space,
+the value is marked as tainted.

 The syntax is otherwise the same as the ACL modifier &"set ="&.
 
 .cmdopt -bem <&'filename'&>
 The syntax is otherwise the same as the ACL modifier &"set ="&.
 
 .cmdopt -bem <&'filename'&>


@@ -3010,7 +3061,8 @@ test your relay controls using &%-bh%&.
 
 &*Warning 1*&:
 .cindex "RFC 1413"
 
 &*Warning 1*&:
 .cindex "RFC 1413"

-You can test features of the configuration that rely on ident (RFC 1413)
+You can test features of the configuration that rely on ident
+(&url(https://www.rfc-editor.org/rfc/rfc2487,RFC 1413))

 information by using the &%-oMt%& option. However, Exim cannot actually perform
 an ident callout when testing using &%-bh%& because there is no incoming SMTP
 connection.
 information by using the &%-oMt%& option. However, Exim cannot actually perform
 an ident callout when testing using &%-bh%& because there is no incoming SMTP
 connection.


@@ -3033,7 +3085,7 @@ acceptable or not. See section &<<SECTcheckaccess>>&.
 Features such as authentication and encryption, where the client input is not
 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
 specialized SMTP test program such as
 Features such as authentication and encryption, where the client input is not
 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
 specialized SMTP test program such as

-&url(https://www.jetmore.org/john/code/swaks/,swaks).
+&url(https://www.jetmore.org/john/code/swaks/,swaks,swaks).

 
 .cmdopt -bhc <&'IP&~address'&>
 This option operates in the same way as &%-bh%&, except that address
 
 .cmdopt -bhc <&'IP&~address'&>
 This option operates in the same way as &%-bh%&, except that address


@@ -3076,7 +3128,9 @@ recognised DSCP names.
 .cindex "Sieve filter" "capabilities"
 This option causes Exim to emit an alphabetically sorted list of all supported
 Sieve protocol extensions on stdout, one per line.  This is anticipated to be
 .cindex "Sieve filter" "capabilities"
 This option causes Exim to emit an alphabetically sorted list of all supported
 Sieve protocol extensions on stdout, one per line.  This is anticipated to be

-useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
+useful for ManageSieve
+(&url(https://datatracker.ietf.org/doc/html/rfc5804.html,RFC 5804))
+implementations, in providing that protocol's

 &`SIEVE`& capability response line.  As the precise list may depend upon
 compile-time build options, which this option will adapt to, this is the only
 way to guarantee a correct response.
 &`SIEVE`& capability response line.  As the precise list may depend upon
 compile-time build options, which this option will adapt to, this is the only
 way to guarantee a correct response.


@@ -3086,7 +3140,9 @@ way to guarantee a correct response.
 This option runs an Exim receiving process that accepts an incoming,
 locally-generated message on the standard input. The recipients are given as the
 command arguments (except when &%-t%& is also present &-- see below). Each
 This option runs an Exim receiving process that accepts an incoming,
 locally-generated message on the standard input. The recipients are given as the
 command arguments (except when &%-t%& is also present &-- see below). Each

-argument can be a comma-separated list of RFC 2822 addresses. This is the
+argument can be a comma-separated list of
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) addresses.
+This is the

 default option for selecting the overall action of an Exim call; it is assumed
 if no other conflicting option is present.
 
 default option for selecting the overall action of an Exim call; it is assumed
 if no other conflicting option is present.
 


@@ -3096,7 +3152,7 @@ options, as appropriate. The &%-bnq%& option (see below) provides a way of
 suppressing this for special cases.
 
 Policy checks on the contents of local messages can be enforced by means of
 suppressing this for special cases.
 
 Policy checks on the contents of local messages can be enforced by means of

-the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
+the non-SMTP ACL. See section &<<SECnonSMTP>>& for details.

 
 .cindex "return code" "for &%-bm%&"
 The return code is zero if the message is successfully accepted. Otherwise, the
 
 .cindex "return code" "for &%-bm%&"
 The return code is zero if the message is successfully accepted. Otherwise, the


@@ -3108,7 +3164,9 @@ The format
 .cindex "&""From""& line"
 .cindex "UUCP" "&""From""& line"
 .cindex "Sendmail compatibility" "&""From""& line"
 .cindex "&""From""& line"
 .cindex "UUCP" "&""From""& line"
 .cindex "Sendmail compatibility" "&""From""& line"

-of the message must be as defined in RFC 2822, except that, for
+of the message must be as defined in
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822),
+except that, for

 compatibility with Sendmail and Smail, a line in one of the forms
 .code
 From sender Fri Jan  5 12:55 GMT 1997
 compatibility with Sendmail and Smail, a line in one of the forms
 .code
 From sender Fri Jan  5 12:55 GMT 1997


@@ -3372,7 +3430,7 @@ dots doubled), terminated by a line containing just a single dot. An error is
 provoked if the terminating dot is missing. A further message may then follow.
 
 As for other local message submissions, the contents of incoming batch SMTP
 provoked if the terminating dot is missing. A further message may then follow.
 
 As for other local message submissions, the contents of incoming batch SMTP

-messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
+messages can be checked using the non-SMTP ACL (see section &<<SECnonSMTP>>&).

 Unqualified addresses are automatically qualified using &%qualify_domain%& and
 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
 
 Unqualified addresses are automatically qualified using &%qualify_domain%& and
 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
 


@@ -4095,8 +4153,9 @@ written to the standard output. This option can be used only by an admin user.
 .cindex "message" "listing in RFC 2822 format"
 .cindex "listing" "message in RFC 2822 format"
 This option causes a copy of the complete message (header lines plus body) to
 .cindex "message" "listing in RFC 2822 format"
 .cindex "listing" "message in RFC 2822 format"
 This option causes a copy of the complete message (header lines plus body) to

-be written to the standard output in RFC 2822 format. This option can be used
-only by an admin user.
+be written to the standard output in
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+format. This option can be used only by an admin user.

 
 .cmdopt -Mvh <&'message&~id'&>
 .cindex "listing" "message headers"
 
 .cmdopt -Mvh <&'message&~id'&>
 .cindex "listing" "message headers"


@@ -4710,7 +4769,7 @@ all selected messages, not just the first; frozen messages are included when
 
 The &%-R%& option makes it straightforward to initiate delivery of all messages
 to a given domain after a host has been down for some time. When the SMTP
 
 The &%-R%& option makes it straightforward to initiate delivery of all messages
 to a given domain after a host has been down for some time. When the SMTP

-command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
+command ETRN is accepted by its ACL (see section &<<SECTETRN>>&), its default

 effect is to run Exim with the &%-R%& option, but it can be configured to run
 an arbitrary command instead.
 
 effect is to run Exim with the &%-R%& option, but it can be configured to run
 an arbitrary command instead.
 


@@ -4761,7 +4820,8 @@ lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
 &%-t%& was used in conjunction with &%Resent-%& header lines.)
 
 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
 &%-t%& was used in conjunction with &%Resent-%& header lines.)
 

-RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+talks about different sets of &%Resent-%& header lines (for when a

 message is resent several times). The RFC also specifies that they should be
 added at the front of the message, and separated by &'Received:'& lines. It is
 not at all clear how &%-t%& should operate in the present of multiple sets,
 message is resent several times). The RFC also specifies that they should be
 added at the front of the message, and separated by &'Received:'& lines. It is
 not at all clear how &%-t%& should operate in the present of multiple sets,


@@ -5428,7 +5488,7 @@ list items, it is not ignored when parsing the list. The spaces around the first
 colon in the example above are necessary. If they were not there, the list would
 be interpreted as the two items 127.0.0.1:: and 1.
 
 colon in the example above are necessary. If they were not there, the list would
 be interpreted as the two items 127.0.0.1:: and 1.
 

-.section "Changing list separators" "SECTlistsepchange"
+.subsection "Changing list separators" "SECTlistsepchange"

 .cindex "list separator" "changing"
 .cindex "IPv6" "addresses in lists"
 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
 .cindex "list separator" "changing"
 .cindex "IPv6" "addresses in lists"
 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was


@@ -5469,7 +5529,7 @@ enclosing an empty list item.
 
 
 
 
 
 

-.section "Empty items in lists" "SECTempitelis"
+.subsection "Empty items in lists" "SECTempitelis"

 .cindex "list" "empty item in"
 An empty item at the end of a list is always ignored. In other words, trailing
 separator characters are ignored. Thus, the list in
 .cindex "list" "empty item in"
 An empty item at the end of a list is always ignored. In other words, trailing
 separator characters are ignored. Thus, the list in


@@ -5728,9 +5788,11 @@ 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).
 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,
+&url(https://www.rfc-editor.org/rfc/rfc6409,RFC 6409) (previously 4409)
+specifies use of port 587 for SMTP Submission,

 which uses STARTTLS, so this is the &"submission"& port.
 which uses STARTTLS, so this is the &"submission"& port.

-RFC 8314 specifies use of port 465 as the &"submissions"& protocol,
+&url(https://www.rfc-editor.org/rfc/rfc8314,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.
 which should be used in preference to 587.
 You should also consider deploying SRV records to help clients find
 these ports.


@@ -5789,8 +5851,9 @@ Note that it is not always possible to find a host name from an IP address,
 because not all DNS reverse zones are maintained, and sometimes DNS servers are
 unreachable.
 
 because not all DNS reverse zones are maintained, and sometimes DNS servers are
 unreachable.
 

-The next two lines are concerned with &'ident'& callbacks, as defined by RFC
-1413 (hence their names):
+The next two lines are concerned with &'ident'& callbacks, as defined by
+&url(https://www.rfc-editor.org/rfc/rfc1413,RFC 1413)
+(hence their names):

 .code
 rfc1413_hosts = *
 rfc1413_query_timeout = 0s
 .code
 rfc1413_hosts = *
 rfc1413_query_timeout = 0s


@@ -5863,7 +5926,8 @@ not often needed).
 .endd
 
 In an ideal world everybody follows the standards. For non-ASCII
 .endd
 
 In an ideal world everybody follows the standards. For non-ASCII

-messages RFC 2047 is a standard, allowing a maximum line length of 76
+messages &url(https://www.rfc-editor.org/rfc/rfc2048,RFC 2047)
+is a standard, allowing a maximum line length of 76

 characters. Exim adheres that standard and won't process messages which
 violate this standard. (Even ${rfc2047:...} expansions will fail.)
 In particular, the Exim maintainers have had multiple reports of
 characters. Exim adheres that standard and won't process messages which
 violate this standard. (Even ${rfc2047:...} expansions will fail.)
 In particular, the Exim maintainers have had multiple reports of


@@ -5965,7 +6029,9 @@ block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
 or &"|"&. If you have local accounts that include these characters, you will
 have to modify this rule.
 
 or &"|"&. If you have local accounts that include these characters, you will
 have to modify this rule.
 

-Empty components (two dots in a row) are not valid in RFC 2822, but Exim
+Empty components (two dots in a row) are not valid in
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822),
+but Exim

 allows them because they have been encountered in practice. (Consider the
 common convention of local parts constructed as
 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
 allows them because they have been encountered in practice. (Consider the
 common convention of local parts constructed as
 &"&'first-initial.second-initial.family-name'&"& when applied to someone like


@@ -6841,7 +6907,8 @@ by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
 .cindex "dsearch lookup type"
 The given file must be an absolute directory path; this is searched for an entry
 whose name is the key by calling the &[lstat()]& function.
 .cindex "dsearch lookup type"
 The given file must be an absolute directory path; this is searched for an entry
 whose name is the key by calling the &[lstat()]& function.

-The key may not contain any forward slash characters.
+Unless the options (below) permit a path,
+the key may not contain any forward slash characters.

 If &[lstat()]& succeeds then so does the lookup.
 .cindex "tainted data" "dsearch result"
 The result is regarded as untainted.
 If &[lstat()]& succeeds then so does the lookup.
 .cindex "tainted data" "dsearch result"
 The result is regarded as untainted.


@@ -6850,7 +6917,7 @@ Options for the lookup can be given by appending them after the word "dsearch",
 separated by a comma.  Options, if present, are a comma-separated list having
 each element starting with a tag name and an equals.
 
 separated by a comma.  Options, if present, are a comma-separated list having
 each element starting with a tag name and an equals.
 

-Two options are supported, for the return value and for filtering match
+Three options are supported, for the return value and for filtering match

 candidates.
 The "ret" option requests an alternate result value of
 the entire path for the entry. Example:
 candidates.
 The "ret" option requests an alternate result value of
 the entire path for the entry. Example:


@@ -6858,6 +6925,7 @@ the entire path for the entry. Example:
 ${lookup {passwd} dsearch,ret=full {/etc}}
 .endd
 The default result is just the requested entry.
 ${lookup {passwd} dsearch,ret=full {/etc}}
 .endd
 The default result is just the requested entry.

+

 The "filter" option requests that only directory entries of a given type
 are matched. The match value is one of "file", "dir" or "subdir" (the latter
 not matching "." or ".."). Example:
 The "filter" option requests that only directory entries of a given type
 are matched. The match value is one of "file", "dir" or "subdir" (the latter
 not matching "." or ".."). Example:


@@ -6867,6 +6935,14 @@ ${lookup {passwd} dsearch,filter=file {/etc}}
 The default matching is for any entry type, including directories
 and symlinks.
 
 The default matching is for any entry type, including directories
 and symlinks.
 

+The "key" option relaxes the restriction that only a simple path component can
+be searched for, to permit a sequence of path components. Example:
+.code
+${lookup {foo/bar} dsearch,key=path {/etc}}
+.endd
+If this option is used, a ".." component in the key is specifically disallowed.
+The default operation is that the key may only be a single path component.
+

 An example of how this
 lookup can be used to support virtual domains is given in section
 &<<SECTvirtualdomains>>&.
 An example of how this
 lookup can be used to support virtual domains is given in section
 &<<SECTvirtualdomains>>&.


@@ -6896,8 +6972,8 @@ key is found. The first key that matches is used; there is no attempt to find a
 lookup types support only literal keys.
 
 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
 lookup types support only literal keys.
 
 &*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>>&).
+the implicit key is the host's IP address rather than its name
+(see section &<<SECThoslispatsikey>>&).

 
 &*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
 
 &*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


@@ -6933,7 +7009,7 @@ For elements of type string, the returned value is de-quoted.
 The given file is an LMDB database.
 LMDB is a memory-mapped key-value store,
 with API modeled loosely on that of BerkeleyDB.
 The given file is an LMDB database.
 LMDB is a memory-mapped key-value store,
 with API modeled loosely on that of BerkeleyDB.

-See &url(https://symas.com/products/lightning-memory-mapped-database/)
+See &url(https://symas.com/products/lightning-memory-mapped-database/,LMDB)

 for the feature set and operation modes.
 
 Exim provides read-only access via the LMDB C library.
 for the feature set and operation modes.
 
 Exim provides read-only access via the LMDB C library.


@@ -7659,7 +7735,8 @@ First we explain how LDAP queries are coded.
 
 .subsection "Format of LDAP queries" SECTforldaque
 .cindex "LDAP" "query format"
 
 .subsection "Format of LDAP queries" SECTforldaque
 .cindex "LDAP" "query format"

-An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
+An LDAP query takes the form of a URL as defined in
+&url(https://www.rfc-editor.org/rfc/rfc2255,RFC 2255). For example, in

 the configuration of a &(redirect)& router one might have this setting:
 .code
 data = ${lookup ldap \
 the configuration of a &(redirect)& router one might have this setting:
 .code
 data = ${lookup ldap \


@@ -7702,7 +7779,9 @@ the string:
 )   =>   \29
 \   =>   \5C
 .endd
 )   =>   \29
 \   =>   \5C
 .endd

-in accordance with RFC 2254. The resulting string is then quoted according
+in accordance with
+&url(https://www.rfc-editor.org/rfc/rfc2254,RFC 2254).
+The resulting string is then quoted according

 to the rules for URLs, that is, all non-alphanumeric characters except
 .code
 ! $ ' - . _ ( ) * +
 to the rules for URLs, that is, all non-alphanumeric characters except
 .code
 ! $ ' - . _ ( ) * +


@@ -7726,8 +7805,10 @@ by inserting a backslash in front of any of the following characters:
 , + " \ < > ;
 .endd
 It also inserts a backslash before any leading spaces or # characters, and
 , + " \ < > ;
 .endd
 It also inserts a backslash before any leading spaces or # characters, and

-before any trailing spaces. (These rules are in RFC 2253.) The resulting string
-is then quoted according to the rules for URLs. For example:
+before any trailing spaces. (These rules are in
+&url(https://www.rfc-editor.org/rfc/rfc2255,RFC 2253).)
+The resulting string is then quoted according to the rules for URLs.
+For example:

 .code
 ${quote_ldap_dn: a(bc)*, a<yz>; }
 .endd
 .code
 ${quote_ldap_dn: a(bc)*, a<yz>; }
 .endd


@@ -7763,7 +7844,8 @@ Errors which cause the next server to be tried are connection failures, bind
 failures, and timeouts.
 
 For each server name in the list, a port number can be given. The standard way
 failures, and timeouts.
 
 For each server name in the list, a port number can be given. The standard way

-of specifying a host and port is to use a colon separator (RFC 1738). Because
+of specifying a host and port is to use a colon separator
+(&url(https://www.rfc-editor.org/rfc/rfc1738,RFC 1738)). Because

 &%ldap_default_servers%& is a colon-separated list, such colons have to be
 doubled. For example
 .code
 &%ldap_default_servers%& is a colon-separated list, such colons have to be
 doubled. For example
 .code


@@ -8156,7 +8238,6 @@ option, you can still update it by a query of this form:
 ${lookup pgsql,servers=master/db/name/pw {UPDATE ...} }
 .endd
 
 ${lookup pgsql,servers=master/db/name/pw {UPDATE ...} }
 .endd
 

-.new

 A now-deprecated syntax places the servers specification before the query,
 semicolon separated:
 .code
 A now-deprecated syntax places the servers specification before the query,
 semicolon separated:
 .code


@@ -8165,10 +8246,9 @@ ${lookup mysql{servers=master; UPDATE ...} }
 The new version avoids issues with tainted
 arguments explicitly expanded as part of the query.
 The entire string within the braces becomes tainted,
 The new version avoids issues with tainted
 arguments explicitly expanded as part of the query.
 The entire string within the braces becomes tainted,

-including the server sepcification - which is not permissible.
+including the server specification - which is not permissible.

 If the older sytax is used, a warning message will be logged.
 This syntax will be removed in a future release.
 If the older sytax is used, a warning message will be logged.
 This syntax will be removed in a future release.

-.wen

 
 &*Note*&: server specifications in list-style lookups are still problematic.
 
 
 &*Note*&: server specifications in list-style lookups are still problematic.
 


@@ -8197,6 +8277,9 @@ or delete command), the result of the lookup is the number of rows affected.
 anything (for example, setting a field to the value it already has), the result
 is zero because no rows are affected.
 
 anything (for example, setting a field to the value it already has), the result
 is zero because no rows are affected.
 

+To get an encryted connection, use a Mysql option file with the required
+parameters for the connection.
+

 
 .subsection "Special PostgreSQL features" SECID74
 PostgreSQL lookups can also use Unix domain socket connections to the database.
 
 .subsection "Special PostgreSQL features" SECID74
 PostgreSQL lookups can also use Unix domain socket connections to the database.


@@ -9230,8 +9313,9 @@ is not used.
 
 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
 keys in the file, not IP addresses. If you want to do lookups based on IP
 
 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
 keys in the file, not IP addresses. If you want to do lookups based on IP

-addresses, you must precede the search type with &"net-"& (see section
-&<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
+addresses, you must precede the search type with &"net-"&
+(see section &<<SECThoslispatsikey>>&).
+There is, however, no reason why you could not use

 two items in the same list, one doing an address lookup and one doing a name
 lookup, both using the same file.
 
 two items in the same list, one doing an address lookup and one doing a name
 lookup, both using the same file.
 


@@ -9475,7 +9559,8 @@ example it is a named domain list.
 .cindex "case forcing in address lists"
 Domains in email addresses are always handled caselessly, but for local parts
 case may be significant on some systems (see &%caseful_local_part%& for how
 .cindex "case forcing in address lists"
 Domains in email addresses are always handled caselessly, but for local parts
 case may be significant on some systems (see &%caseful_local_part%& for how

-Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
+Exim deals with this when routing addresses). However,
+&url(https://www.rfc-editor.org/rfc/rfc2505,RFC 2505) (&'Anti-Spam

 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
 blocking lists should be done in a case-independent manner. Since most address
 lists in Exim are used for this kind of control, Exim attempts to do this by
 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
 blocking lists should be done in a case-independent manner. Since most address
 lists in Exim are used for this kind of control, Exim attempts to do this by


@@ -10118,7 +10203,9 @@ option in the runtime configuration. The value of this option defaults to the
 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
 ISO-8859-1.
 
 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
 ISO-8859-1.
 

-Header names follow the syntax of RFC 2822, which states that they may contain
+Header names follow the syntax of
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822),
+which states that they may contain

 any printing characters except space and colon. Consequently, curly brackets
 &'do not'& terminate header names, and should not be used to enclose them as
 if they were variables. Attempting to do so causes a syntax error.
 any printing characters except space and colon. Consequently, curly brackets
 &'do not'& terminate header names, and should not be used to enclose them as
 if they were variables. Attempting to do so causes a syntax error.


@@ -10167,7 +10254,8 @@ the result of expanding any of these variables is tainted.
 .cindex &%hmac%&
 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
 shared secret and some text into a message authentication code, as specified in
 .cindex &%hmac%&
 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
 shared secret and some text into a message authentication code, as specified in

-RFC 2104. This differs from &`${md5:secret_text...}`& or
+&url(https://www.rfc-editor.org/rfc/rfc2104.RFC 2104).
+This differs from &`${md5:secret_text...}`& or

 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
 cryptographic hash, allowing for authentication that is not possible with MD5
 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
 cryptographic hash, allowing for authentication that is not possible with MD5
 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at


@@ -10774,7 +10862,7 @@ will sort an MX lookup into priority order.
 
 
 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
 
 
 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&

-SRS encoding.  See SECT &<<SECTSRS>>& for details.
+SRS encoding.  See section &<<SECTSRS>>& for details.

 
 
 
 
 
 


@@ -10869,7 +10957,9 @@ following operations can be performed:
 .vitem &*${address:*&<&'string'&>&*}*&
 .cindex "expansion" "RFC 2822 address handling"
 .cindex "&%address%& expansion item"
 .vitem &*${address:*&<&'string'&>&*}*&
 .cindex "expansion" "RFC 2822 address handling"
 .cindex "&%address%& expansion item"

-The string is interpreted as an RFC 2822 address, as it might appear in a
+The string is interpreted as an
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+address, as it might appear in a

 header line, and the effective address is extracted from it. If the string does
 not parse successfully, the result is empty.
 
 header line, and the effective address is extracted from it. If the string does
 not parse successfully, the result is empty.
 


@@ -10879,8 +10969,9 @@ The parsing correctly handles SMTPUTF8 Unicode in the string.
 .vitem &*${addresses:*&<&'string'&>&*}*&
 .cindex "expansion" "RFC 2822 address handling"
 .cindex "&%addresses%& expansion item"
 .vitem &*${addresses:*&<&'string'&>&*}*&
 .cindex "expansion" "RFC 2822 address handling"
 .cindex "&%addresses%& expansion item"

-The string (after expansion) is interpreted as a list of addresses in RFC
-2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
+The string (after expansion) is interpreted as a list of addresses in
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+format, such as can be found in a &'To:'& or &'Cc:'& header line. The

 operative address (&'local-part@domain'&) is extracted from each item, and the
 result of the expansion is a colon-separated list, with appropriate
 doubling of colons should any happen to be present in the email addresses.
 operative address (&'local-part@domain'&) is extracted from each item, and the
 result of the expansion is a colon-separated list, with appropriate
 doubling of colons should any happen to be present in the email addresses.


@@ -10983,8 +11074,10 @@ This operator converts a base64-encoded string into the un-coded form.
 .vitem &*${domain:*&<&'string'&>&*}*&
 .cindex "domain" "extraction"
 .cindex "expansion" "domain extraction"
 .vitem &*${domain:*&<&'string'&>&*}*&
 .cindex "domain" "extraction"
 .cindex "expansion" "domain extraction"

-The string is interpreted as an RFC 2822 address and the domain is extracted
-from it. If the string does not parse successfully, the result is empty.
+The string is interpreted as an
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+address and the domain is extracted from it.
+If the string does not parse successfully, the result is empty.

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


@@ -11217,9 +11310,10 @@ nor expansion of lookup elements, is done by the &%listnamed%& operator.
 .vitem &*${local_part:*&<&'string'&>&*}*&
 .cindex "expansion" "local part extraction"
 .cindex "&%local_part%& expansion item"
 .vitem &*${local_part:*&<&'string'&>&*}*&
 .cindex "expansion" "local part extraction"
 .cindex "&%local_part%& expansion item"

-The string is interpreted as an RFC 2822 address and the local part is
-extracted from it. If the string does not parse successfully, the result is
-empty.
+The string is interpreted as an
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+address and the local part is extracted from it.
+If the string does not parse successfully, the result is empty.

 The parsing correctly handles SMTPUTF8 Unicode in the string.
 
 
 The parsing correctly handles SMTPUTF8 Unicode in the string.
 
 


@@ -11305,8 +11399,10 @@ variable or a message header.
 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
 .cindex "&%quote_local_part%& expansion item"
 This operator is like &%quote%&, except that it quotes the string only if
 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
 .cindex "&%quote_local_part%& expansion item"
 This operator is like &%quote%&, except that it quotes the string only if

-required to do so by the rules of RFC 2822 for quoting local parts. For
-example, a plus sign would not cause quoting (but it would for &%quote%&).
+required to do so by the rules of
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+for quoting local parts. For example,
+a plus sign would not cause quoting (but it would for &%quote%&).

 If you are creating a new email address from the contents of &$local_part$&
 (or any other unknown data), you should always use this operator.
 
 If you are creating a new email address from the contents of &$local_part$&
 (or any other unknown data), you should always use this operator.
 


@@ -11365,7 +11461,8 @@ f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
 .cindex "expansion" "RFC 2047"
 .cindex "RFC 2047" "expansion operator"
 .cindex "&%rfc2047%& expansion item"
 .cindex "expansion" "RFC 2047"
 .cindex "RFC 2047" "expansion operator"
 .cindex "&%rfc2047%& expansion item"

-This operator encodes text according to the rules of RFC 2047. This is an
+This operator encodes text according to the rules of
+&url(https://www.rfc-editor.org/rfc/rfc2047,RFC 2047). This is an

 encoding that is used in header lines to encode non-ASCII characters. It is
 assumed that the input string is in the encoding specified by the
 &%headers_charset%& option, which gets its default at build time. If the string
 encoding that is used in header lines to encode non-ASCII characters. It is
 assumed that the input string is in the encoding specified by the
 &%headers_charset%& option, which gets its default at build time. If the string


@@ -11383,7 +11480,9 @@ characters.
 .cindex "expansion" "RFC 2047"
 .cindex "RFC 2047" "decoding"
 .cindex "&%rfc2047d%& expansion item"
 .cindex "expansion" "RFC 2047"
 .cindex "RFC 2047" "decoding"
 .cindex "&%rfc2047d%& expansion item"

-This operator decodes strings that are encoded as per RFC 2047. Binary zero
+This operator decodes strings that are encoded as per
+&url(https://www.rfc-editor.org/rfc/rfc2047,RFC 2047).
+Binary zero

 bytes are replaced by question marks. Characters are converted into the
 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
 not recognized unless &%check_rfc2047_length%& is set false.
 bytes are replaced by question marks. Characters are converted into the
 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
 not recognized unless &%check_rfc2047_length%& is set false.


@@ -11562,6 +11661,18 @@ literal question mark).
 .cindex "&%utf8_localpart_from_alabel%& expansion item"
 These convert EAI mail name components between UTF-8 and a-label forms.
 For information on internationalisation support see &<<SECTi18nMTA>>&.
 .cindex "&%utf8_localpart_from_alabel%& expansion item"
 These convert EAI mail name components between UTF-8 and a-label forms.
 For information on internationalisation support see &<<SECTi18nMTA>>&.

+
+
+.vitem &*${xtextd:*&<&'string'&>&*}*&
+.cindex "text forcing in strings"
+.cindex "string" "xtext decoding"
+.cindex "xtext"
+.cindex "&%xtextd%& expansion item"
+This performs xtext decoding of the string (per
+&url(https://www.rfc-editor.org/rfc/rfc3461,RFC 3461) section 4).
+
+
+

 .endlist
 
 
 .endlist
 
 


@@ -12051,7 +12162,8 @@ where the first item in the list is the empty string.
 .next
 The item @[] matches any of the local host's interface addresses.
 .next
 .next
 The item @[] matches any of the local host's interface addresses.
 .next

-Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
+Single-key lookups are assumed to be like &"net-"& style lookups in host lists
+(see section &<<SECThoslispatsikey>>&),

 even if &`net-`& is not specified. There is never any attempt to turn the IP
 address into a host name. The most common type of linear search for
 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
 even if &`net-`& is not specified. There is never any attempt to turn the IP
 address into a host name. The most common type of linear search for
 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR


@@ -12209,7 +12321,9 @@ initiated by queue runner processes, and false otherwise.
 .cindex "Radius"
 .cindex "expansion" "Radius authentication"
 .cindex "&%radius%& expansion condition"
 .cindex "Radius"
 .cindex "expansion" "Radius authentication"
 .cindex "&%radius%& expansion condition"

-Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
+Radius authentication
+(&url(https://www.rfc-editor.org/rfc/rfc2865,RFC 2865))
+is supported in a similar way to PAM. You must

 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
 the Radius client configuration file in order to build Exim with Radius
 support.
 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
 the Radius client configuration file in order to build Exim with Radius
 support.


@@ -12563,6 +12677,11 @@ 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 &$connection_id$&
+.vindex "&$connection_id$&"
+.cindex connection "identifier logging"
+An identifier for the accepted connection, for use in custom logging.
+

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


@@ -14455,7 +14574,7 @@ The common use of this option is expected to be
 .code
 tls_on_connect_ports = 465
 .endd
 .code
 tls_on_connect_ports = 465
 .endd

-per RFC 8314.
+per &url(https://www.rfc-editor.org/rfc/rfc8314,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.
 
 There is also a command line option &%-tls-on-connect%&, which forces all ports
 to behave in this way when a daemon is started.
 


@@ -14812,6 +14931,7 @@ listed in more than one group.
 .row &%acl_smtp_rcpt%&               "ACL for RCPT"
 .row &%acl_smtp_starttls%&           "ACL for STARTTLS"
 .row &%acl_smtp_vrfy%&               "ACL for VRFY"
 .row &%acl_smtp_rcpt%&               "ACL for RCPT"
 .row &%acl_smtp_starttls%&           "ACL for STARTTLS"
 .row &%acl_smtp_vrfy%&               "ACL for VRFY"

+.row &%acl_smtp_wellknown%&          "ACL for WELLKNOWN"

 .row &%av_scanner%&                  "specify virus scanner"
 .row &%check_rfc2047_length%&        "check length of RFC 2047 &""encoded &&&
                                       words""&"
 .row &%av_scanner%&                  "specify virus scanner"
 .row &%check_rfc2047_length%&        "check length of RFC 2047 &""encoded &&&
                                       words""&"


@@ -14978,6 +15098,7 @@ See also the &'Policy controls'& section above.
 .row &%prdr_enable%&                 "advertise PRDR to all hosts"
 .row &%smtputf8_advertise_hosts%&    "advertise SMTPUTF8 to these hosts"
 .row &%tls_advertise_hosts%&         "advertise TLS to these hosts"
 .row &%prdr_enable%&                 "advertise PRDR to all hosts"
 .row &%smtputf8_advertise_hosts%&    "advertise SMTPUTF8 to these hosts"
 .row &%tls_advertise_hosts%&         "advertise TLS to these hosts"

+.row &%wellknown_advertise_hosts%&   "advertise WELLKNOWN to these hosts"

 .endtable
 
 
 .endtable
 
 


@@ -15101,7 +15222,7 @@ log_selector = +8bitmime
 .cindex "&ACL;" "for non-SMTP messages"
 .cindex "non-SMTP messages" "ACLs for"
 This option defines the ACL that is run when a non-SMTP message has been
 .cindex "&ACL;" "for non-SMTP messages"
 .cindex "non-SMTP messages" "ACLs for"
 This option defines the ACL that is run when a non-SMTP message has been

-read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
+read and is on the point of being accepted. See section &<<SECnonSMTP>>& for

 further details.
 
 .option acl_not_smtp_mime main string&!! unset
 further details.
 
 .option acl_not_smtp_mime main string&!! unset


@@ -15113,24 +15234,26 @@ SMTP messages.
 .cindex "&ACL;" "at start of non-SMTP message"
 .cindex "non-SMTP messages" "ACLs for"
 This option defines the ACL that is run before Exim starts reading a
 .cindex "&ACL;" "at start of non-SMTP message"
 .cindex "non-SMTP messages" "ACLs for"
 This option defines the ACL that is run before Exim starts reading a

-non-SMTP message. See chapter &<<CHAPACL>>& for further details.
+non-SMTP message. See section &<<SECnonSMTP>>& for further details.

 
 .option acl_smtp_auth main string&!! unset
 .cindex "&ACL;" "setting up for SMTP commands"
 .cindex "AUTH" "ACL for"
 This option defines the ACL that is run when an SMTP AUTH command is
 
 .option acl_smtp_auth main string&!! unset
 .cindex "&ACL;" "setting up for SMTP commands"
 .cindex "AUTH" "ACL for"
 This option defines the ACL that is run when an SMTP AUTH command is

-received. See chapter &<<CHAPACL>>& for further details.
+received.
+See chapter &<<CHAPACL>>& for general information on ACLs, and chapter
+&<<CHAPSMTPAUTH>>& for details of authentication.

 
 .option acl_smtp_connect main string&!! unset
 .cindex "&ACL;" "on SMTP connection"
 This option defines the ACL that is run when an SMTP connection is received.
 
 .option acl_smtp_connect main string&!! unset
 .cindex "&ACL;" "on SMTP connection"
 This option defines the ACL that is run when an SMTP connection is received.

-See chapter &<<CHAPACL>>& for further details.
+See section &<<SECconnectACL>>& for further details.

 
 .option acl_smtp_data main string&!! unset
 .cindex "DATA" "ACL for"
 This option defines the ACL that is run after an SMTP DATA command has been
 processed and the message itself has been received, but before the final
 
 .option acl_smtp_data main string&!! unset
 .cindex "DATA" "ACL for"
 This option defines the ACL that is run after an SMTP DATA command has been
 processed and the message itself has been received, but before the final

-acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
+acknowledgment is sent. See section &<<SECdataACLS>>& for further details.

 
 .option acl_smtp_data_prdr main string&!! accept
 .cindex "PRDR" "ACL for"
 
 .option acl_smtp_data_prdr main string&!! accept
 .cindex "PRDR" "ACL for"


@@ -15141,7 +15264,7 @@ This option defines the ACL that,
 if the PRDR feature has been negotiated,
 is run for each recipient after an SMTP DATA command has been
 processed and the message itself has been received, but before the
 if the PRDR feature has been negotiated,
 is run for each recipient after an SMTP DATA command has been
 processed and the message itself has been received, but before the

-acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
+acknowledgment is sent. See section &<<SECTPRDRACL>>& for further details.

 
 .option acl_smtp_dkim main string&!! unset
 .cindex DKIM "ACL for"
 
 .option acl_smtp_dkim main string&!! unset
 .cindex DKIM "ACL for"


@@ -15152,8 +15275,11 @@ See section &<<SECDKIMVFY>>& for further details.
 
 .option acl_smtp_etrn main string&!! unset
 .cindex "ETRN" "ACL for"
 
 .option acl_smtp_etrn main string&!! unset
 .cindex "ETRN" "ACL for"

+.cindex "ETRN" advertisement

 This option defines the ACL that is run when an SMTP ETRN command is
 This option defines the ACL that is run when an SMTP ETRN command is

-received. See chapter &<<CHAPACL>>& for further details.
+received.
+If no value is set then the ETRN facility is not advertised.
+See chapter &<<CHAPACL>>& for further details.

 
 .option acl_smtp_expn main string&!! unset
 .cindex "EXPN" "ACL for"
 
 .option acl_smtp_expn main string&!! unset
 .cindex "EXPN" "ACL for"


@@ -15164,7 +15290,7 @@ received. See chapter &<<CHAPACL>>& for further details.
 .cindex "EHLO" "ACL for"
 .cindex "HELO" "ACL for"
 This option defines the ACL that is run when an SMTP EHLO or HELO
 .cindex "EHLO" "ACL for"
 .cindex "HELO" "ACL for"
 This option defines the ACL that is run when an SMTP EHLO or HELO

-command is received. See chapter &<<CHAPACL>>& for further details.
+command is received. See section &<<SECheloACL>>& for further details.

 
 
 .option acl_smtp_mail main string&!! unset
 
 
 .option acl_smtp_mail main string&!! unset


@@ -15175,7 +15301,8 @@ received. See chapter &<<CHAPACL>>& for further details.
 .option acl_smtp_mailauth main string&!! unset
 .cindex "AUTH" "on MAIL command"
 This option defines the ACL that is run when there is an AUTH parameter on
 .option acl_smtp_mailauth main string&!! unset
 .cindex "AUTH" "on MAIL command"
 This option defines the ACL that is run when there is an AUTH parameter on

-a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
+a MAIL command.
+See chapter &<<CHAPACL>>& for general information on ACLs, and chapter

 &<<CHAPSMTPAUTH>>& for details of authentication.
 
 .option acl_smtp_mime main string&!! unset
 &<<CHAPSMTPAUTH>>& for details of authentication.
 
 .option acl_smtp_mime main string&!! unset


@@ -15188,7 +15315,7 @@ section &<<SECTscanmimepart>>& for details.
 .cindex "not-QUIT, ACL for"
 This option defines the ACL that is run when an SMTP session
 ends without a QUIT command being received.
 .cindex "not-QUIT, ACL for"
 This option defines the ACL that is run when an SMTP session
 ends without a QUIT command being received.

-See chapter &<<CHAPACL>>& for further details.
+See section &<<SECTNOTQUITACL>>& for further details.

 
 .option acl_smtp_predata main string&!! unset
 This option defines the ACL that is run when an SMTP DATA command is
 
 .option acl_smtp_predata main string&!! unset
 This option defines the ACL that is run when an SMTP DATA command is


@@ -15203,7 +15330,7 @@ received. See chapter &<<CHAPACL>>& for further details.
 .option acl_smtp_rcpt main string&!! unset
 .cindex "RCPT" "ACL for"
 This option defines the ACL that is run when an SMTP RCPT command is
 .option acl_smtp_rcpt main string&!! unset
 .cindex "RCPT" "ACL for"
 This option defines the ACL that is run when an SMTP RCPT command is

-received. See chapter &<<CHAPACL>>& for further details.
+received. See section &<<SECTQUITACL>>& for further details.

 
 .option acl_smtp_starttls main string&!! unset
 .cindex "STARTTLS, ACL for"
 
 .option acl_smtp_starttls main string&!! unset
 .cindex "STARTTLS, ACL for"


@@ -15215,6 +15342,11 @@ received. See chapter &<<CHAPACL>>& for further details.
 This option defines the ACL that is run when an SMTP VRFY command is
 received. See chapter &<<CHAPACL>>& for further details.
 
 This option defines the ACL that is run when an SMTP VRFY command is
 received. See chapter &<<CHAPACL>>& for further details.
 

+.option acl_smtp_wellknown main string&!! unset
+.cindex "WELLKNOWN, ACL for"
+This option defines the ACL that is run when an SMTP WELLKNOWN command is
+received. See section &<<SECTWELLKNOWNACL>>& for further details.
+

 .option add_environment main "string list" empty
 .cindex "environment" "set values"
 This option adds individual environment variables that the
 .option add_environment main "string list" empty
 .cindex "environment" "set values"
 This option adds individual environment variables that the


@@ -15235,7 +15367,9 @@ To permit this, you have to add individuals to the Exim group.
 
 .option allow_domain_literals main boolean false
 .cindex "domain literal"
 
 .option allow_domain_literals main boolean false
 .cindex "domain literal"

-If this option is set, the RFC 2822 domain literal format is permitted in
+If this option is set, the
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+domain literal format is permitted in

 email addresses. The option is not set by default, because the domain literal
 format is not normally required these days, and few people know about it. It
 has, however, been exploited by mail abusers.
 email addresses. The option is not set by default, because the domain literal
 format is not normally required these days, and few people know about it. It
 has, however, been exploited by mail abusers.


@@ -15481,7 +15615,8 @@ See &%check_spool_space%& below.
 .oindex "&%check_rfc2047_length%&"
 .cindex "RFC 2047" "disabling length check"
 .option check_rfc2047_length main boolean true
 .oindex "&%check_rfc2047_length%&"
 .cindex "RFC 2047" "disabling length check"
 .option check_rfc2047_length main boolean true

-RFC 2047 defines a way of encoding non-ASCII characters in headers using a
+&url(https://www.rfc-editor.org/rfc/rfc2047,RFC 2047)
+defines a way of encoding non-ASCII characters in headers using a

 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
 word; strings to be encoded that exceed this length are supposed to use
 multiple encoded words. By default, Exim does not recognize encoded words that
 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
 word; strings to be encoded that exceed this length are supposed to use
 multiple encoded words. By default, Exim does not recognize encoded words that


@@ -15546,8 +15681,9 @@ may wish to deliberately disable them.
 .cindex CHUNKING advertisement
 .cindex "RFC 3030" "CHUNKING"
 .cindex "ESMTP extensions" CHUNKING
 .cindex CHUNKING advertisement
 .cindex "RFC 3030" "CHUNKING"
 .cindex "ESMTP extensions" CHUNKING

-The CHUNKING extension (RFC3030) will be advertised in the EHLO message to
-these hosts.
+The CHUNKING extension
+(&url(https://www.rfc-editor.org/rfc/rfc3030.html,RFC 3030))
+will be advertised in the EHLO message to these hosts.

 Hosts may use the BDAT command as an alternate to DATA.
 
 .option commandline_checks_require_admin main boolean &`false`&
 Hosts may use the BDAT command as an alternate to DATA.
 
 .option commandline_checks_require_admin main boolean &`false`&


@@ -15693,7 +15829,8 @@ sha256
 sha512
 .endd
 
 sha512
 .endd
 

-Note that the acceptance of sha1 violates RFC 8301.
+Note that the acceptance of sha1 violates
+&url(https://www.rfc-editor.org/rfc/rfc8301,RFC 8301).

 
 .option dkim_verify_keytypes main "string list" "ed25519 : rsa"
 This option gives a list of key types which are acceptable in signatures,
 
 .option dkim_verify_keytypes main "string list" "ed25519 : rsa"
 This option gives a list of key types which are acceptable in signatures,


@@ -15706,7 +15843,9 @@ This option gives a list of key sizes which are acceptable in signatures.
 The list is keyed by the algorithm type for the key; the values are in bits.
 Signatures with keys smaller than given by this option will fail verification.
 
 The list is keyed by the algorithm type for the key; the values are in bits.
 Signatures with keys smaller than given by this option will fail verification.
 

-The default enforces the RFC 8301 minimum key size for RSA signatures.
+The default enforces the
+&url(https://www.rfc-editor.org/rfc/rfc8301,RFC 8301)
+minimum key size for RSA signatures.

 
 .option dkim_verify_minimal main boolean false
 If set to true, verification of signatures will terminate after the
 
 .option dkim_verify_minimal main boolean false
 If set to true, verification of signatures will terminate after the


@@ -15720,9 +15859,9 @@ the ACL once for each signature in the message.
 See section &<<SECDKIMVFY>>&.
 
 
 See section &<<SECDKIMVFY>>&.
 
 

-.option dmarc_forensic_sender main string&!! unset &&&
-        dmarc_history_file main string unset &&&
-        dmarc_tld_file main string unset
+.options dmarc_forensic_sender main string&!! unset &&&
+         dmarc_history_file main string unset &&&
+         dmarc_tld_file main string unset

 .cindex DMARC "main section options"
 These options control DMARC processing.
 See section &<<SECDMARC>>& for details.
 .cindex DMARC "main section options"
 These options control DMARC processing.
 See section &<<SECDMARC>>& for details.


@@ -15901,7 +16040,8 @@ described in section &<<SECTlineendings>>&.
 .cindex "DSN" "success"
 .cindex "Delivery Status Notification" "success"
 .cindex "ESMTP extensions" DSN
 .cindex "DSN" "success"
 .cindex "Delivery Status Notification" "success"
 .cindex "ESMTP extensions" DSN

-DSN extensions (RFC3461) will be advertised in the EHLO message to,
+DSN extensions (&url(https://www.rfc-editor.org/rfc/rfc3461,RFC 3461))
+will be advertised in the EHLO message to,

 and accepted from, these hosts.
 Hosts may use the NOTIFY and ORCPT options on RCPT TO commands,
 and RET and ENVID options on MAIL FROM commands.
 and accepted from, these hosts.
 Hosts may use the NOTIFY and ORCPT options on RCPT TO commands,
 and RET and ENVID options on MAIL FROM commands.


@@ -15981,7 +16121,8 @@ and warning messages. For example:
 .code
 errors_reply_to = postmaster@my.domain.example
 .endd
 .code
 errors_reply_to = postmaster@my.domain.example
 .endd

-The value of the option is not expanded. It must specify a valid RFC 2822
+The value of the option is not expanded. It must specify a valid
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)

 address. However, if a warning message that is generated by the
 &%quota_warn_message%& option in an &(appendfile)& transport contain its
 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
 address. However, if a warning message that is generated by the
 &%quota_warn_message%& option in an &(appendfile)& transport contain its
 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is


@@ -16048,9 +16189,11 @@ routing, but which are not used for listening by the daemon. See section
 
 . Allow this long option name to split; give it unsplit as a fifth argument
 . for the automatic .oindex that is generated by .option.
 
 . Allow this long option name to split; give it unsplit as a fifth argument
 . for the automatic .oindex that is generated by .option.

+. WAS:
+. .option "extract_addresses_remove_ &~&~arguments"
+. but apparently this results in searchability problems; bug 1197

 
 

-.option "extract_addresses_remove_arguments" main boolean true &&&
-         extract_addresses_remove_arguments
+.option extract_addresses_remove_arguments main boolean true

 .oindex "&%-t%&"
 .cindex "command line" "addresses with &%-t%&"
 .cindex "Sendmail compatibility" "&%-t%& option"
 .oindex "&%-t%&"
 .cindex "command line" "addresses with &%-t%&"
 .cindex "Sendmail compatibility" "&%-t%& option"


@@ -16189,11 +16332,13 @@ set.
 .cindex "EHLO" "underscores in"
 .cindex "underscore in EHLO/HELO"
 This option can be set to a string of rogue characters that are permitted in
 .cindex "EHLO" "underscores in"
 .cindex "underscore in EHLO/HELO"
 This option can be set to a string of rogue characters that are permitted in

-all EHLO and HELO names in addition to the standard letters, digits,
-hyphens, and dots. If you really must allow underscores, you can set
+non-ip-literal EHLO and HELO names in addition to the standard letters, digits,
+hyphens, and dots. For example if you really must allow underscores,
+you can set

 .code
 helo_allow_chars = _
 .endd
 .code
 helo_allow_chars = _
 .endd

+This option does not apply to names that look like ip-literals.

 Note that the value is one string, not a list.
 
 
 Note that the value is one string, not a list.
 
 


@@ -16557,17 +16702,16 @@ has been built with LDAP support.
 
 
 
 
 
 

-.new

 .option limits_advertise_hosts main "host list&!!" *
 .cindex LIMITS "suppressing advertising"
 .cindex "ESMTP extensions" LIMITS
 This option can be used to suppress the advertisement of the SMTP
 .option limits_advertise_hosts main "host list&!!" *
 .cindex LIMITS "suppressing advertising"
 .cindex "ESMTP extensions" LIMITS
 This option can be used to suppress the advertisement of the SMTP

-LIMITS extension (RFC 9422) to specific hosts.
-If permitted, Exim as a servier will advertise in the EHLO response
+LIMITS extension (&url(https://www.ietf.org/rfc/rfc9422.html,RFC 9422))
+to specific hosts.
+If permitted, Exim as a server will advertise in the EHLO response

 the limit for RCPT commands set by the &%recipients_max%& option (if it is set)
 and the limit for MAIL commands set by the &%smtp_accept_max_per_connection%&
 option.
 the limit for RCPT commands set by the &%recipients_max%& option (if it is set)
 and the limit for MAIL commands set by the &%smtp_accept_max_per_connection%&
 option.

-,wen

 
 .option local_from_check main boolean true
 .cindex "&'Sender:'& header line" "disabling addition of"
 
 .option local_from_check main boolean true
 .cindex "&'Sender:'& header line" "disabling addition of"


@@ -16794,8 +16938,9 @@ empty string, the option is ignored.
 .option message_id_header_text main string&!! unset
 If this variable is set, the string is expanded and used to augment the text of
 the &'Message-id:'& header that Exim creates if a locally-originated incoming
 .option message_id_header_text main string&!! unset
 If this variable is set, the string is expanded and used to augment the text of
 the &'Message-id:'& header that Exim creates if a locally-originated incoming

-message does not have one. The text of this header is required by RFC 2822 to
-take the form of an address. By default, Exim uses its internal message id as
+message does not have one. The text of this header is required by
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+to take the form of an address. By default, Exim uses its internal message id as

 the local part, and the primary host name as the domain. If this option is set,
 it is expanded, and provided the expansion is not forced to fail, and does not
 yield an empty string, the result is inserted into the header immediately
 the local part, and the primary host name as the domain. If this option is set,
 it is expanded, and provided the expansion is not forced to fail, and does not
 yield an empty string, the result is inserted into the header immediately


@@ -17054,7 +17199,9 @@ common installed configuration.
 The &"percent hack"& is the convention whereby a local part containing a
 percent sign is re-interpreted as a new email address, with the percent
 replaced by @. This is sometimes called &"source routing"&, though that term is
 The &"percent hack"& is the convention whereby a local part containing a
 percent sign is re-interpreted as a new email address, with the percent
 replaced by @. This is sometimes called &"source routing"&, though that term is

-also applied to RFC 2822 addresses that begin with an @ character. If this
+also applied to
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+addresses that begin with an @ character. If this

 option is set, Exim implements the percent facility for those domains listed,
 but no others. This happens before an incoming SMTP address is tested against
 an ACL.
 option is set, Exim implements the percent facility for those domains listed,
 but no others. This happens before an incoming SMTP address is tested against
 an ACL.


@@ -17128,7 +17275,7 @@ See also the &%hosts_pipe_connect%& smtp transport option.
 
 The SMTP service extension keyword advertised is &"PIPECONNECT"&;
 it permits the client to pipeline
 
 The SMTP service extension keyword advertised is &"PIPECONNECT"&;
 it permits the client to pipeline

-TCP connection and hello command (inclear phase),
+TCP connection and hello command (cleatext phase),

 or TLS-establishment and hello command (encrypted phase),
 on later connections to the same host.
 
 or TLS-establishment and hello command (encrypted phase),
 on later connections to the same host.
 


@@ -17182,7 +17329,8 @@ is set, code values of 128 and above are also considered to be printing
 characters.
 
 This option also affects the header syntax checks performed by the
 characters.
 
 This option also affects the header syntax checks performed by the

-&(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
+&(autoreply)& transport, and whether Exim uses
+&url(https://www.rfc-editor.org/rfc/rfc2047,RFC 2047) encoding of

 the user's full name when constructing From: and Sender: addresses (as
 described in section &<<SECTconstr>>&). Setting this option can cause
 Exim to generate eight bit message headers that do not conform to the
 the user's full name when constructing From: and Sender: addresses (as
 described in section &<<SECTconstr>>&). Setting this option can cause
 Exim to generate eight bit message headers that do not conform to the


@@ -17408,8 +17556,9 @@ added to each message, except for the timestamp, which is automatically added
 on at the end (preceded by a semicolon). The string is expanded each time it is
 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
 on at the end (preceded by a semicolon). The string is expanded each time it is
 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.
+&"Received:"& and conform to the
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+specification for &'Received:'& header lines.

 The default setting is:
 
 .code
 The default setting is:
 
 .code


@@ -17472,16 +17621,24 @@ or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
 option was not set.
 
 
 option was not set.
 
 

-.option recipients_max main integer 50000
+.option recipients_max main integer&!! 50000

 .cindex "limit" "number of recipients"
 .cindex "recipient" "maximum number"
 .cindex "limit" "number of recipients"
 .cindex "recipient" "maximum number"

-If this option is set greater than zero, it specifies the maximum number of
+If the value resulting from expanding this option
+is set greater than zero, it specifies the maximum number of

 original recipients for any message. Additional recipients that are generated
 by aliasing or forwarding do not count. SMTP messages get a 452 response for
 all recipients over the limit; earlier recipients are delivered as normal.
 Non-SMTP messages with too many recipients are failed, and no deliveries are
 done.
 
 original recipients for any message. Additional recipients that are generated
 by aliasing or forwarding do not count. SMTP messages get a 452 response for
 all recipients over the limit; earlier recipients are delivered as normal.
 Non-SMTP messages with too many recipients are failed, and no deliveries are
 done.
 

+For SMTP message the expansion is done after the connection is
+accepted (but before any SMTP conversation) and may depend on
+the IP addresses and port numbers of the connection.
+&*Note*&: If an expansion is used for the option,
+care should be taken that a resonable value results for
+non-SMTP messages.
+

 .cindex "RCPT" "maximum number of incoming"
 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
 RCPT commands in a single message.
 .cindex "RCPT" "maximum number of incoming"
 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
 RCPT commands in a single message.


@@ -17570,7 +17727,8 @@ the default value.
 
 .option return_path_remove main boolean true
 .cindex "&'Return-path:'& header line" "removing"
 
 .option return_path_remove main boolean true
 .cindex "&'Return-path:'& header line" "removing"

-RFC 2821, section 4.4, states that an SMTP server must insert a
+&url(https://www.rfc-editor.org/rfc/rfc2821,RFC 2821), section 4.4,
+states that an SMTP server must insert a

 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
 The &'Return-path:'& header preserves the sender address as received in the
 MAIL command. This description implies that this header should not be present
 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
 The &'Return-path:'& header preserves the sender address as received in the
 MAIL command. This description implies that this header should not be present


@@ -17587,7 +17745,8 @@ This option is an obsolete synonym for &%bounce_return_size_limit%&.
 .option rfc1413_hosts main "host list&!!" @[]
 .cindex "RFC 1413"
 .cindex "host" "for RFC 1413 calls"
 .option rfc1413_hosts main "host list&!!" @[]
 .cindex "RFC 1413"
 .cindex "host" "for RFC 1413 calls"

-RFC 1413 identification calls are made to any client host which matches
+&url(https://www.rfc-editor.org/rfc/rfc1413,RFC 1413)
+identification calls are made to any client host which matches

 an item in the list.
 The default value specifies just this host, being any local interface
 for the system.
 an item in the list.
 The default value specifies just this host, being any local interface
 for the system.


@@ -17595,7 +17754,9 @@ for the system.
 .option rfc1413_query_timeout main time 0s
 .cindex "RFC 1413" "query timeout"
 .cindex "timeout" "for RFC 1413 call"
 .option rfc1413_query_timeout main time 0s
 .cindex "RFC 1413" "query timeout"
 .cindex "timeout" "for RFC 1413 call"

-This sets the timeout on RFC 1413 identification calls. If it is set to zero,
+This sets the timeout on
+&url(https://www.rfc-editor.org/rfc/rfc1413,RFC 1413)
+identification calls. If it is set to zero,

 no RFC 1413 calls are ever made.
 
 
 no RFC 1413 calls are ever made.
 
 


@@ -17688,8 +17849,7 @@ live with.
 . searchable.  NM changed this occurrence for bug 1197 to no longer allow
 . the option name to split.
 
 . searchable.  NM changed this occurrence for bug 1197 to no longer allow
 . the option name to split.
 

-.option "smtp_accept_max_per_connection" main integer&!! 1000 &&&
-         smtp_accept_max_per_connection
+.option smtp_accept_max_per_connection main integer&!! 1000

 .cindex "SMTP" "limiting incoming message count"
 .cindex "limit" "messages per SMTP connection"
 The value of this option limits the number of MAIL commands that Exim is
 .cindex "SMTP" "limiting incoming message count"
 .cindex "limit" "messages per SMTP connection"
 The value of this option limits the number of MAIL commands that Exim is


@@ -17743,8 +17903,7 @@ various &%-od%&&'x'& command line options.
 
 . See the comment on smtp_accept_max_per_connection
 
 
 . See the comment on smtp_accept_max_per_connection
 

-.option "smtp_accept_queue_per_connection" main integer 10 &&&
-         smtp_accept_queue_per_connection
+.option smtp_accept_queue_per_connection main integer 10

 .cindex "queueing incoming messages"
 .cindex "message" "queueing by message count"
 This option limits the number of delivery processes that Exim starts
 .cindex "queueing incoming messages"
 .cindex "message" "queueing by message count"
 This option limits the number of delivery processes that Exim starts


@@ -18516,11 +18675,16 @@ If Exim is using OpenSSL and this option is empty or unset, then Exim will load
 a default DH prime; the default is Exim-specific but lacks verifiable provenance.
 
 In older versions of Exim the default was the 2048 bit prime described in section
 a default DH prime; the default is Exim-specific but lacks verifiable provenance.
 
 In older versions of Exim the default was the 2048 bit prime described in section

-2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
+2.2 of &url(https://www.rfc-editor.org/rfc/rfc5114,RFC 5114),
+"2048-bit MODP Group with 224-bit Prime Order Subgroup", which

 in IKE is assigned number 23.
 
 Otherwise, the option must expand to the name used by Exim for any of a number
 in IKE is assigned number 23.
 
 Otherwise, the option must expand to the name used by Exim for any of a number

-of DH primes specified in RFC 2409, RFC 3526, RFC 5114, RFC 7919, or from other
+of DH primes specified in
+&url(https://www.rfc-editor.org/rfc/rfc2409,RFC 2409),
+&url(https://www.rfc-editor.org/rfc/rfc3526,RFC 3526),
+&url(https://www.rfc-editor.org/rfc/rfc5114,RFC 5114),
+&url(https://www.rfc-editor.org/rfc/rfc7919,RFC 7919), or from other

 sources.  As names, Exim uses a standard specified name, else "ike" followed by
 the number used by IKE, or "default" which corresponds to
 &`exim.dev.20160529.3`&.
 sources.  As names, Exim uses a standard specified name, else "ike" followed by
 the number used by IKE, or "default" which corresponds to
 &`exim.dev.20160529.3`&.


@@ -18537,13 +18701,15 @@ The available additional primes are:
 Some of these will be too small to be accepted by clients.
 Some may be too large to be accepted by clients.
 The open cryptographic community has suspicions about the integrity of some
 Some of these will be too small to be accepted by clients.
 Some may be too large to be accepted by clients.
 The open cryptographic community has suspicions about the integrity of some

-of the later IKE values, which led into RFC7919 providing new fixed constants
-(the "ffdhe" identifiers).
+of the later IKE values, which led into
+&url(https://www.rfc-editor.org/rfc/rfc7919,RFC 7919)
+providing new fixed constants (the "ffdhe" identifiers).

 
 At this point, all of the "ike" values should be considered obsolete;
 they are still in Exim to avoid breaking unusual configurations, but are
 candidates for removal the next time we have backwards-incompatible changes.
 
 At this point, all of the "ike" values should be considered obsolete;
 they are still in Exim to avoid breaking unusual configurations, but are
 candidates for removal the next time we have backwards-incompatible changes.

-Two of them in particular (&`ike1`& and &`ike22`&) are called out by RFC 8247
+Two of them in particular (&`ike1`& and &`ike22`&) are called out by
+&url(https://www.rfc-editor.org/rfc/rfc8247,RFC 8247)

 as MUST NOT use for IPSEC, and two more (&`ike23`& and &`ike24`&) as
 SHOULD NOT.
 Because of this, Exim regards them as deprecated; if either of the first pair
 as MUST NOT use for IPSEC, and two more (&`ike23`& and &`ike24`&) as
 SHOULD NOT.
 Because of this, Exim regards them as deprecated; if either of the first pair


@@ -18874,6 +19040,12 @@ absolute and untainted.
 See also &%bounce_message_file%&.
 
 
 See also &%bounce_message_file%&.
 
 

+.option wellknown_advertise_hosts main boolean unset
+.cindex WELLKNOWN advertisement
+.cindex "ESMTP extensions" WELLKNOWN
+This option enables the advertising of the SMTP WELLKNOWN extension.
+See also the &%acl_smtp_wellknown%& ACL (&<<SECTWELLKNOWNACL>>&).
+

 .option write_rejectlog main boolean true
 .cindex "reject log" "disabling"
 If this option is set false, Exim no longer writes anything to the reject log.
 .option write_rejectlog main boolean true
 .cindex "reject log" "disabling"
 If this option is set false, Exim no longer writes anything to the reject log.


@@ -19206,7 +19378,8 @@ to be used.
 .option dsn_lasthop routers boolean false
 .cindex "DSN" "success"
 .cindex "Delivery Status Notification" "success"
 .option dsn_lasthop routers boolean false
 .cindex "DSN" "success"
 .cindex "Delivery Status Notification" "success"

-If this option is set true, and extended DSN (RFC3461) processing is in effect,
+If this option is set true, and extended DSN
+(&url(https://www.rfc-editor.org/rfc/rfc3461,RFC 3461)) processing is in effect,

 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
 instead send a success DSN as if the next hop does not support DSN.
 Not effective on redirect routers.
 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
 instead send a success DSN as if the next hop does not support DSN.
 Not effective on redirect routers.


@@ -20249,8 +20422,9 @@ the local host is described in section &<<SECTreclocipadd>>&.
 
 .option check_srv dnslookup string&!! unset
 .cindex "SRV record" "enabling use of"
 
 .option check_srv dnslookup string&!! unset
 .cindex "SRV record" "enabling use of"

-The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
-addition to MX and address records. The support is disabled by default. To
+The &(dnslookup)& router supports the use of SRV records
+(see &url(https://www.rfc-editor.org/rfc/rfc2782,RFC 2782))
+in addition to MX and address records. The support is disabled by default. To

 enable SRV support, set the &%check_srv%& option to the name of the service
 required. For example,
 .code
 enable SRV support, set the &%check_srv%& option to the name of the service
 required. For example,
 .code


@@ -20478,7 +20652,9 @@ entered. No widening ever takes place for these lookups.
 This router has no private options. Unless it is being used purely for
 verification (see &%verify_only%&) a transport is required to be defined by the
 generic &%transport%& option. The router accepts the address if its domain part
 This router has no private options. Unless it is being used purely for
 verification (see &%verify_only%&) a transport is required to be defined by the
 generic &%transport%& option. The router accepts the address if its domain part

-takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
+takes the form of an
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+domain literal. For example, the &(ipliteral)&

 router handles the address
 .code
 root@[192.168.1.1]
 router handles the address
 .code
 root@[192.168.1.1]


@@ -21327,8 +21503,9 @@ userforward:
 If the file does not exist, or causes no action to be taken (for example, it is
 empty or consists only of comments), the router declines. &*Warning*&: This
 is not the case when the file contains syntactically valid items that happen to
 If the file does not exist, or causes no action to be taken (for example, it is
 empty or consists only of comments), the router declines. &*Warning*&: This
 is not the case when the file contains syntactically valid items that happen to

-yield empty addresses, for example, items containing only RFC 2822 address
-comments.
+yield empty addresses, for example, items containing only
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+address comments.

 
 .cindex "tainted data" "in filenames"
 .cindex redirect "tainted data"
 
 .cindex "tainted data" "in filenames"
 .cindex redirect "tainted data"


@@ -21452,8 +21629,9 @@ preceded by &"\"&, but this is not a requirement for loop prevention. However,
 it does make a difference if more than one domain is being handled
 synonymously.
 
 it does make a difference if more than one domain is being handled
 synonymously.
 

-If an item begins with &"\"& and the rest of the item parses as a valid RFC
-2822 address that does not include a domain, the item is qualified using the
+If an item begins with &"\"& and the rest of the item parses as a valid
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+address that does not include a domain, the item is qualified using the

 domain of the incoming address. In the absence of a leading &"\"&, unqualified
 addresses are qualified using the value in &%qualify_recipient%&, but you can
 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
 domain of the incoming address. In the absence of a leading &"\"&, unqualified
 addresses are qualified using the value in &%qualify_recipient%&, but you can
 force the incoming domain to be used by setting &%qualify_preserve_domain%&.


@@ -21492,7 +21670,9 @@ lists (that is, in non-filter redirection data):
 .cindex "pipe" "in redirection list"
 .cindex "address redirection" "to pipe"
 An item is treated as a pipe command if it begins with &"|"& and does not parse
 .cindex "pipe" "in redirection list"
 .cindex "address redirection" "to pipe"
 An item is treated as a pipe command if it begins with &"|"& and does not parse

-as a valid RFC 2822 address that includes a domain. A transport for running the
+as a valid
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+address that includes a domain. A transport for running the

 command must be specified by the &%pipe_transport%& option.
 Normally, either the router or the transport specifies a user and a group under
 which to run the delivery. The default is to use the Exim user and group.
 command must be specified by the &%pipe_transport%& option.
 Normally, either the router or the transport specifies a user and a group under
 which to run the delivery. The default is to use the Exim user and group.


@@ -21525,7 +21705,9 @@ an &%accept%& router.
 .cindex "file" "in redirection list"
 .cindex "address redirection" "to file"
 An item is interpreted as a path name if it begins with &"/"& and does not
 .cindex "file" "in redirection list"
 .cindex "address redirection" "to file"
 An item is interpreted as a path name if it begins with &"/"& and does not

-parse as a valid RFC 2822 address that includes a domain. For example,
+parse as a valid
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+address that includes a domain. For example,

 .code
 /home/world/minbari
 .endd
 .code
 /home/world/minbari
 .endd


@@ -22148,6 +22330,12 @@ subject to address rewriting. Otherwise, they are treated like new addresses
 and are rewritten according to the global rewriting rules.
 
 
 and are rewritten according to the global rewriting rules.
 
 

+.option sieve_inbox redirect string&!! inbox
+.new
+The value of this option is passed to a Sieve filter to specify the
+name of the mailbox used for "keep" operations (explicit or implicit).
+.wen
+

 .option sieve_subaddress redirect string&!! unset
 The value of this option is passed to a Sieve filter to specify the
 :subaddress part of an address.
 .option sieve_subaddress redirect string&!! unset
 The value of this option is passed to a Sieve filter to specify the
 :subaddress part of an address.


@@ -22196,7 +22384,9 @@ so it is passed to the following routers.
 
 .cindex "Sieve filter" "syntax errors in"
 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
 
 .cindex "Sieve filter" "syntax errors in"
 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This

-action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
+action is specified by
+&url(https://www.rfc-editor.org/rfc/rfc3028.html,RFC 3028).
+The values of &%skip_syntax_errors%&,

 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
 
 &%skip_syntax_errors%& can be used to specify that errors in users' forward
 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
 
 &%skip_syntax_errors%& can be used to specify that errors in users' forward


@@ -22772,7 +22962,8 @@ Although the return path is normally available in the prefix line of BSD
 mailboxes, this is commonly not displayed by MUAs, and so the user does not
 have easy access to it.
 
 mailboxes, this is commonly not displayed by MUAs, and so the user does not
 have easy access to it.
 

-RFC 2821 states that the &'Return-path:'& header is added to a message &"when
+&url(https://www.rfc-editor.org/rfc/rfc2821,RFC 2821)
+states that the &'Return-path:'& header is added to a message &"when

 the delivery SMTP server makes the final delivery"&. This implies that this
 header should not be present in incoming messages. Exim has a configuration
 option, &%return_path_remove%&, which requests removal of this header from
 the delivery SMTP server makes the final delivery"&. This implies that this
 header should not be present in incoming messages. Exim has a configuration
 option, &%return_path_remove%&, which requests removal of this header from


@@ -22844,7 +23035,9 @@ filter itself, and the original process that reads the result and delivers it
 are all run in parallel, like a shell pipeline.
 
 The filter can perform any transformations it likes, but of course should take
 are all run in parallel, like a shell pipeline.
 
 The filter can perform any transformations it likes, but of course should take

-care not to break RFC 2822 syntax. Exim does not check the result, except to
+care not to break
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+syntax. Exim does not check the result, except to

 test for a final newline when SMTP is in use. All messages transmitted over
 SMTP must end with a newline, so Exim supplies one if it is missing.
 
 test for a final newline when SMTP is in use. All messages transmitted over
 SMTP must end with a newline, so Exim supplies one if it is missing.
 


@@ -23184,7 +23377,11 @@ fileinto "folder23";
 .endd
 In this situation, the expansion of &%file%& or &%directory%& in the transport
 must transform the relative path into an appropriate absolute filename. In the
 .endd
 In this situation, the expansion of &%file%& or &%directory%& in the transport
 must transform the relative path into an appropriate absolute filename. In the

-case of Sieve filters, the name &'inbox'& must be handled. It is the name that
+case of Sieve filters, the name &'inbox'& must be handled. It is the
+.new
+default
+.wen
+name that

 is used as a result of a &"keep"& action in the filter. This example shows one
 way of handling this requirement:
 .code
 is used as a result of a &"keep"& action in the filter. This example shows one
 way of handling this requirement:
 .code


@@ -23200,6 +23397,12 @@ With this setting of &%file%&, &'inbox'& refers to the standard mailbox
 location, absolute paths are used without change, and other folders are in the
 &_mail_& directory within the home directory.
 
 location, absolute paths are used without change, and other folders are in the
 &_mail_& directory within the home directory.
 

+.new
+An alternative for the &"keep"& aspect is to use the &%sieve_inbox%& option
+on the redirect router that calls the Sieve filter,
+to explicitly set the filename used.
+.wen
+

 &*Note 1*&: While processing an Exim filter, a relative path such as
 &_folder23_& is turned into an absolute path if a home directory is known to
 the router. In particular, this is the case if &%check_local_user%& is set. If
 &*Note 1*&: While processing an Exim filter, a relative path such as
 &_folder23_& is turned into an absolute path if a home directory is known to
 the router. In particular, this is the case if &%check_local_user%& is set. If


@@ -23210,6 +23413,10 @@ path to the transport.
 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
 the &%file%& or &%directory%& option is still used if it is set.
 
 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
 the &%file%& or &%directory%& option is still used if it is set.
 

+.new
+&*Note 3*&: Permitting a user to enable writes to an absolute path
+may be a security issue.
+.wen

 
 
 
 
 
 


@@ -24308,7 +24515,9 @@ The &(autoreply)& transport is not a true transport in that it does not cause
 the message to be transmitted. Instead, it generates a new mail message as an
 automatic reply to the incoming message. &'References:'& and
 &'Auto-Submitted:'& header lines are included. These are constructed according
 the message to be transmitted. Instead, it generates a new mail message as an
 automatic reply to the incoming message. &'References:'& and
 &'Auto-Submitted:'& header lines are included. These are constructed according

-to the rules in RFCs 2822 and 3834, respectively.
+to the rules in RFCs
+&url(https://www.rfc-editor.org/rfc/rfc2822,2822) and
+&url(https://datatracker.ietf.org/doc/html/rfc3834,3834), respectively.

 
 If the router that passes the message to this transport does not have the
 &%unseen%& option set, the original message (for the current recipient) is not
 
 If the router that passes the message to this transport does not have the
 &%unseen%& option set, the original message (for the current recipient) is not


@@ -24404,7 +24613,9 @@ specified by the transport.
 
 
 .option headers autoreply string&!! unset
 
 
 .option headers autoreply string&!! unset

-This specifies additional RFC 2822 headers that are to be added to the message
+This specifies additional
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+headers that are to be added to the message

 when the message is specified by the transport. Several can be given by using
 &"\n"& to separate them. There is no check on the format.
 
 when the message is specified by the transport. Several can be given by using
 &"\n"& to separate them. There is no check on the format.
 


@@ -24512,8 +24723,9 @@ when the message is specified by the transport.
 .cindex "transports" "&(lmtp)&"
 .cindex "&(lmtp)& transport"
 .cindex "LMTP" "over a pipe"
 .cindex "transports" "&(lmtp)&"
 .cindex "&(lmtp)& transport"
 .cindex "LMTP" "over a pipe"

-.cindex "LMTP" "over a socket"
-The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
+.cindex "LMTP" "over a unix-domain socket"
+The &(lmtp)& transport runs the LMTP protocol
+(&url(https://www.rfc-editor.org/rfc/rfc2033,RFC 2033)) over a pipe to a

 specified command
 or by interacting with a Unix domain socket.
 This transport is something of a cross between the &(pipe)& and &(smtp)&
 specified command
 or by interacting with a Unix domain socket.
 This transport is something of a cross between the &(pipe)& and &(smtp)&


@@ -25357,7 +25569,8 @@ to a remote host. A setting of zero allows the system timeout (typically
 several minutes) to act. To have any effect, the value of this option must be
 less than the system timeout. However, it has been observed that on some
 systems there is no system timeout, which is why the default value for this
 several minutes) to act. To have any effect, the value of this option must be
 less than the system timeout. However, it has been observed that on some
 systems there is no system timeout, which is why the default value for this

-option is 5 minutes, a value recommended by RFC 1123.
+option is 5 minutes, a value recommended by
+&url(https://www.rfc-editor.org/rfc/rfc1123,RFC 1123).

 
 
 .option connection_max_messages smtp integer 500
 
 
 .option connection_max_messages smtp integer 500


@@ -25369,12 +25582,10 @@ over a single TCP/IP connection. If the value is zero, there is no limit.
 For testing purposes, this value can be overridden by the &%-oB%& command line
 option.
 
 For testing purposes, this value can be overridden by the &%-oB%& command line
 option.
 

-.new

 .cindex "ESMTP extensions" LIMITS
 If the peer advertises a LIMITS extension with a MAILMAX value,
 and either TLSS is in use or was not advertised,
 that value also constrains the result of this option.
 .cindex "ESMTP extensions" LIMITS
 If the peer advertises a LIMITS extension with a MAILMAX value,
 and either TLSS is in use or was not advertised,
 that value also constrains the result of this option.

-.wen

 
 
 .option dane_require_tls_ciphers smtp string&!! unset
 
 
 .option dane_require_tls_ciphers smtp string&!! unset


@@ -25599,12 +25810,10 @@ suffices for one known case.
 During the expansion of this option the &$item$& variable will have the
 server's EHLO response.
 
 During the expansion of this option the &$item$& variable will have the
 server's EHLO response.
 

-.new

 For TLS-on-connect connections we do not have an EHLO
 response to use. Because of this the default value of this option is
 set to a static string for those cases, meaning that resumption will
 always be attempted if permitted by the &%tls_resumption_hosts%& option.
 For TLS-on-connect connections we do not have an EHLO
 response to use. Because of this the default value of this option is
 set to a static string for those cases, meaning that resumption will
 always be attempted if permitted by the &%tls_resumption_hosts%& option.

-.wen

 
 The result of the option expansion is included in the key used to store and
 retrieve the TLS session, for session resumption.
 
 The result of the option expansion is included in the key used to store and
 retrieve the TLS session, for session resumption.


@@ -25868,7 +26077,7 @@ See section &<<SECDANE>>&.
 .cindex "RFC 7413" "TCP Fast Open"
 This option provides a list of servers to which, provided
 the facility is supported by this system, Exim will attempt to
 .cindex "RFC 7413" "TCP Fast Open"
 This option provides a list of servers to which, provided
 the facility is supported by this system, Exim will attempt to

-perform a TCP Fast Open.
+perform a TCP Fast Open (&url(https://www.rfc-editor.org/rfc/rfc7413,RFC 7413).

 No data is sent on the SYN segment but, if the remote server also
 supports the facility, it can send its SMTP banner immediately after
 the SYN,ACK segment.  This can save up to one round-trip time.
 No data is sent on the SYN segment but, if the remote server also
 supports the facility, it can send its SMTP banner immediately after
 the SYN,ACK segment.  This can save up to one round-trip time.


@@ -25952,13 +26161,11 @@ each set of addresses is treated independently, and
 so can cause parallel connections to the same host if &%remote_max_parallel%&
 permits this.
 
 so can cause parallel connections to the same host if &%remote_max_parallel%&
 permits this.
 

-.new

 .cindex "ESMTP extensions" LIMITS
 If the peer advertises a LIMITS extension with a RCPTMAX value,
 and either TLSS is in use or was not advertised,
 that value also constrains the result of this option
 and no parallel connections will be caused on meeting the RCPTMAX limit.
 .cindex "ESMTP extensions" LIMITS
 If the peer advertises a LIMITS extension with a RCPTMAX value,
 and either TLSS is in use or was not advertised,
 that value also constrains the result of this option
 and no parallel connections will be caused on meeting the RCPTMAX limit.

-.wen

 
 
 .option message_linelength_limit smtp integer 998
 
 
 .option message_linelength_limit smtp integer 998


@@ -25991,12 +26198,10 @@ If the connection is DANE-enabled then this option is ignored;
 only messages having the domain used for the DANE TLSA lookup are
 sent on the connection.
 
 only messages having the domain used for the DANE TLSA lookup are
 sent on the connection.
 

-.new

 .cindex "ESMTP extensions" LIMITS
 If the peer advertises a LIMITS extension with a RCPTDOMAINMAX value,
 and either TLSS is in use or was not advertised,
 this option is regarded as being false.
 .cindex "ESMTP extensions" LIMITS
 If the peer advertises a LIMITS extension with a RCPTDOMAINMAX value,
 and either TLSS is in use or was not advertised,
 this option is regarded as being false.

-.wen

 
 
 .option port smtp string&!! "see below"
 
 
 .option port smtp string&!! "see below"


@@ -26028,15 +26233,21 @@ to put &"smtps"& in its &"/etc/services"& file, resulting is such deferrals.
 .vindex "&$port$&"
 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
 .vindex "&$port$&"
 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP

-protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
+protocol
+(&url(https://www.rfc-editor.org/rfc/rfc2033,RFC 2033)) instead of SMTP.
+This protocol is sometimes used for local

 deliveries into closed message stores. Exim also has support for running LMTP
 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
 
 deliveries into closed message stores. Exim also has support for running LMTP
 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
 

+&*Note*&: When using LMTP it should be considered whether the default values
+for some other features, such as DANE, are appropriate.
+

 If this option is set to &"smtps"&, the default value for the &%port%& option
 changes to &"smtps"&, and the transport initiates TLS immediately after
 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
 The Internet standards bodies used to strongly discourage use of this mode,
 If this option is set to &"smtps"&, the default value for the &%port%& option
 changes to &"smtps"&, and the transport initiates TLS immediately after
 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
 The Internet standards bodies used to strongly discourage use of this mode,

-but as of RFC 8314 it is preferred over STARTTLS for message submission
+but as of &url(https://www.rfc-editor.org/rfc/rfc8314,RFC 8314) it is preferred
+over STARTTLS for message submission

 (as distinct from MTA-MTA communication).
 
 
 (as distinct from MTA-MTA communication).
 
 


@@ -26520,8 +26731,9 @@ transport time.
 .cindex "testing" "rewriting"
 Exim's input rewriting configuration appears in a part of the runtime
 configuration file headed by &"begin rewrite"&. It can be tested by the
 .cindex "testing" "rewriting"
 Exim's input rewriting configuration appears in a part of the runtime
 configuration file headed by &"begin rewrite"&. It can be tested by the

-&%-brw%& command line option. This takes an address (which can be a full RFC
-2822 address) as its argument. The output is a list of how the address would be
+&%-brw%& command line option. This takes an address (which can be a full
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+address) as its argument. The output is a list of how the address would be

 transformed by the rewriting rules for each of the different places it might
 appear in an incoming message, that is, for each different header and for the
 envelope sender and recipient fields. For example,
 transformed by the rewriting rules for each of the different places it might
 appear in an incoming message, that is, for each different header and for the
 envelope sender and recipient fields. For example,


@@ -26732,7 +26944,10 @@ data for the command, including any surrounding angle brackets.
 .vindex "&$domain$&"
 .vindex "&$local_part$&"
 This form of rewrite rule allows for the handling of addresses that are not
 .vindex "&$domain$&"
 .vindex "&$local_part$&"
 This form of rewrite rule allows for the handling of addresses that are not

-compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
+compliant with RFCs
+&url(https://www.rfc-editor.org/rfc/rfc2821,2821) and
+&url(https://www.rfc-editor.org/rfc/rfc2822,2822)
+(for example, &"bang paths"& in batched SMTP

 input). Because the input is not required to be a syntactically valid address,
 the variables &$local_part$& and &$domain$& are not available during the
 expansion of the replacement string. The result of rewriting replaces the
 input). Because the input is not required to be a syntactically valid address,
 the variables &$local_part$& and &$domain$& are not available during the
 expansion of the replacement string. The result of rewriting replaces the


@@ -26760,8 +26975,9 @@ rewriting once it fails to match (after at least one successful rewrite).
 .next
 .cindex "rewriting" "whole addresses"
 When an address in a header is rewritten, the rewriting normally applies only
 .next
 .cindex "rewriting" "whole addresses"
 When an address in a header is rewritten, the rewriting normally applies only

-to the working part of the address, with any comments and RFC 2822 &"phrase"&
-left unchanged. For example, rewriting might change
+to the working part of the address, with any comments and
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+&"phrase"& left unchanged. For example, rewriting might change

 .code
 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
 .endd
 .code
 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
 .endd


@@ -26773,10 +26989,12 @@ From: Ford Prefect <prefectf@hitch.fict.example>
 Sometimes there is a need to replace the whole address item, and this can be
 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
 causes an address in a header line to be rewritten, the entire address is
 Sometimes there is a need to replace the whole address item, and this can be
 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
 causes an address in a header line to be rewritten, the entire address is

-replaced, not just the working part. The replacement must be a complete RFC
-2822 address, including the angle brackets if necessary. If text outside angle
+replaced, not just the working part. The replacement must be a complete
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+address, including the angle brackets if necessary. If text outside angle

 brackets contains a character whose value is greater than 126 or less than 32
 brackets contains a character whose value is greater than 126 or less than 32

-(except for tab), the text is encoded according to RFC 2047. The character set
+(except for tab), the text is encoded according to
+&url(https://www.rfc-editor.org/rfc/rfc2047,RFC 2047). The character set

 is taken from &%headers_charset%&, which gets its default at build time.
 
 When the &"w"& flag is set on a rule that causes an envelope address to be
 is taken from &%headers_charset%&, which gets its default at build time.
 
 When the &"w"& flag is set on a rule that causes an envelope address to be


@@ -27405,7 +27623,9 @@ considered immediately.
 .scindex IIDauthconf2 "authentication"
 The &"authenticators"& section of Exim's runtime configuration is concerned
 with SMTP authentication. This facility is an extension to the SMTP protocol,
 .scindex IIDauthconf2 "authentication"
 The &"authenticators"& section of Exim's runtime configuration is concerned
 with SMTP authentication. This facility is an extension to the SMTP protocol,

-described in RFC 2554, which allows a client SMTP host to authenticate itself
+described in
+&url(https://www.rfc-editor.org/rfc/rfc2554,RFC 2554),
+which allows a client SMTP host to authenticate itself

 to a server. This is a common way for a server to recognize clients that are
 permitted to use it as a relay. SMTP authentication is not of relevance to the
 transfer of mail between servers that have no managerial connection with each
 to a server. This is a common way for a server to recognize clients that are
 permitted to use it as a relay. SMTP authentication is not of relevance to the
 transfer of mail between servers that have no managerial connection with each


@@ -27479,18 +27699,21 @@ AUTH_SPA=yes
 AUTH_TLS=yes
 .endd
 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
 AUTH_TLS=yes
 .endd
 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5

-authentication mechanism (RFC 2195), and the second provides an interface to
-the Cyrus SASL authentication library.
+authentication mechanism
+(&url(https://www.rfc-editor.org/rfc/rfc2195,RFC 2195)),
+and the second provides an interface to the Cyrus SASL authentication library.

 The third is an interface to Dovecot's authentication system, delegating the
 work via a socket interface.
 The fourth provides for negotiation of authentication done via non-SMTP means,
 The third is an interface to Dovecot's authentication system, delegating the
 work via a socket interface.
 The fourth provides for negotiation of authentication done via non-SMTP means,

-as defined by RFC 4422 Appendix A.
+as defined by &url(https://www.rfc-editor.org/rfc/rfc4422,RFC 4422) Appendix A.

 The fifth provides an interface to the GNU SASL authentication library, which
 provides mechanisms but typically not data sources.
 The sixth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
 supporting setting a server keytab.
 The seventh can be configured to support
 The fifth provides an interface to the GNU SASL authentication library, which
 provides mechanisms but typically not data sources.
 The sixth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
 supporting setting a server keytab.
 The seventh can be configured to support

-the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
+the PLAIN authentication mechanism
+(&url(https://www.rfc-editor.org/rfc/rfc2595,RFC 2595))
+or the LOGIN mechanism, which is

 not formally documented, but used by several MUAs.
 The eighth authenticator
 supports Microsoft's &'Secure Password Authentication'& mechanism.
 not formally documented, but used by several MUAs.
 The eighth authenticator
 supports Microsoft's &'Secure Password Authentication'& mechanism.


@@ -27579,7 +27802,8 @@ authenticators is to be used.
 .option public_name authenticators string unset
 This option specifies the name of the authentication mechanism that the driver
 implements, and by which it is known to the outside world. These names should
 .option public_name authenticators string unset
 This option specifies the name of the authentication mechanism that the driver
 implements, and by which it is known to the outside world. These names should

-contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
+contain only upper case letters, digits, underscores, and hyphens
+(&url(https://www.rfc-editor.org/rfc/rfc2222,RFC 2222)),

 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
 defaults to the driver's instance name.
 
 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
 defaults to the driver's instance name.
 


@@ -27996,11 +28220,13 @@ There are good and bad examples at the end of the next section.
 
 
 
 
 
 

-.section "The PLAIN authentication mechanism" "SECID172"
+.subsection "The PLAIN authentication mechanism" "SECID172"

 .cindex "PLAIN authentication mechanism"
 .cindex authentication PLAIN
 .cindex "binary zero" "in &(plaintext)& authenticator"
 .cindex "PLAIN authentication mechanism"
 .cindex authentication PLAIN
 .cindex "binary zero" "in &(plaintext)& authenticator"

-The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
+The PLAIN authentication mechanism
+(&url(https://www.rfc-editor.org/rfc/rfc2595,RFC 2595))
+specifies that three strings be

 sent as one item of data (that is, one combined string containing two NUL
 separators). The data is sent either as part of the AUTH command, or
 subsequently in response to an empty prompt from the server.
 sent as one item of data (that is, one combined string containing two NUL
 separators). The data is sent either as part of the AUTH command, or
 subsequently in response to an empty prompt from the server.


@@ -28078,7 +28304,7 @@ always fails if its second argument is empty. However, the second way of
 writing the test makes the logic clearer.
 
 
 writing the test makes the logic clearer.
 
 

-.section "The LOGIN authentication mechanism" "SECID173"
+.subsection "The LOGIN authentication mechanism" "SECID173"

 .cindex "LOGIN authentication mechanism"
 .cindex authentication LOGIN
 The LOGIN authentication mechanism is not documented in any RFC, but is in use
 .cindex "LOGIN authentication mechanism"
 .cindex authentication LOGIN
 The LOGIN authentication mechanism is not documented in any RFC, but is in use


@@ -28126,7 +28352,7 @@ the password conform to the Exim syntax. At the LDAP level, the password is an
 uninterpreted string.
 
 
 uninterpreted string.
 
 

-.section "Support for different kinds of authentication" "SECID174"
+.subsection "Support for different kinds of authentication" "SECID174"

 A number of string expansion features are provided for the purpose of
 interfacing to different ways of user authentication. These include checking
 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
 A number of string expansion features are provided for the purpose of
 interfacing to different ways of user authentication. These include checking
 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,


@@ -28207,7 +28433,8 @@ prompts.
 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
 .cindex "CRAM-MD5 authentication mechanism"
 .cindex authentication CRAM-MD5
 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
 .cindex "CRAM-MD5 authentication mechanism"
 .cindex authentication CRAM-MD5

-The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
+The CRAM-MD5 authentication mechanism is described in
+&url(https://www.rfc-editor.org/rfc/rfc2195,RFC 2195). The server

 sends a challenge string to the client, and the response consists of a user
 name and the CRAM-MD5 digest of the challenge string combined with a secret
 string (password) which is known to both server and client. Thus, the secret
 sends a challenge string to the client, and the response consists of a user
 name and the CRAM-MD5 digest of the challenge string combined with a secret
 string (password) which is known to both server and client. Thus, the secret


@@ -28325,7 +28552,9 @@ The code for this authenticator was provided by Matthew Byng-Maddick while
 at A L Digital Ltd.
 
 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
 at A L Digital Ltd.
 
 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL

-library implementation of the RFC 2222 (&"Simple Authentication and Security
+library implementation of the
+&url(https://www.rfc-editor.org/rfc/rfc2222,RFC 2222)
+(&"Simple Authentication and Security

 Layer"&). This library supports a number of authentication mechanisms,
 including PLAIN and LOGIN, but also several others that Exim does not support
 directly. In particular, there is support for Kerberos authentication.
 Layer"&). This library supports a number of authentication mechanisms,
 including PLAIN and LOGIN, but also several others that Exim does not support
 directly. In particular, there is support for Kerberos authentication.


@@ -28815,7 +29044,7 @@ The &(spa)& authenticator provides client support for Microsoft's &'Secure
 Password Authentication'& mechanism,
 which is also sometimes known as NTLM (NT LanMan). The code for client side of
 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
 Password Authentication'& mechanism,
 which is also sometimes known as NTLM (NT LanMan). The code for client side of
 this authenticator was contributed by Marc Prud'hommeaux, and much of it is

-taken from the Samba project (&url(https://www.samba.org/)). The code for the
+taken from the &url(https://www.samba.org/,Samba project). The code for the

 server side was subsequently contributed by Tom Kistner. The mechanism works as
 follows:
 
 server side was subsequently contributed by Tom Kistner. The mechanism works as
 follows:
 


@@ -28903,8 +29132,8 @@ msn:
 .cindex "Certificate-based authentication"
 The &(external)& authenticator provides support for
 authentication based on non-SMTP information.
 .cindex "Certificate-based authentication"
 The &(external)& authenticator provides support for
 authentication based on non-SMTP information.

-The specification is in RFC 4422 Appendix A
-(&url(https://tools.ietf.org/html/rfc4422)).
+The specification is in
+&url(https://tools.ietf.org/html/rfc4422,RFC 4422) Appendix A.

 It is only a transport and negotiation mechanism;
 the process of authentication is entirely controlled
 by the server configuration.
 It is only a transport and negotiation mechanism;
 the process of authentication is entirely controlled
 by the server configuration.


@@ -28915,7 +29144,7 @@ and for clients to only attempt,
 this authentication method on a secure (eg. under TLS) connection.
 
 One possible use, compatible with the
 this authentication method on a secure (eg. under TLS) connection.
 
 One possible use, compatible with the

-K-9 Mail Android client (&url(https://k9mail.github.io/)),
+&url(https://k9mail.github.io/,K-9 Mail Android client)

 is for using X509 client certificates.
 
 It thus overlaps in function with the TLS authenticator
 is for using X509 client certificates.
 
 It thus overlaps in function with the TLS authenticator


@@ -29145,7 +29374,8 @@ You also need to understand the basic concepts of encryption at a managerial
 level, and in particular, the way that public keys, private keys, and
 certificates are used.
 
 level, and in particular, the way that public keys, private keys, and
 certificates are used.
 

-RFC 3207 defines how SMTP connections can make use of encryption. Once a
+&url(https://www.rfc-editor.org/rfc/rfc3207,RFC 3207)
+defines how SMTP connections can make use of encryption. Once a

 connection is established, the client issues a STARTTLS command. If the
 server accepts this, the client and the server negotiate an encryption
 mechanism. If the negotiation succeeds, the data that subsequently passes
 connection is established, the client issues a STARTTLS command. If the
 server accepts this, the client and the server negotiate an encryption
 mechanism. If the negotiation succeeds, the data that subsequently passes


@@ -29172,7 +29402,9 @@ in order to get TLS to work.
 .cindex "SMTP" "ssmtp protocol"
 .cindex "SMTP" "smtps protocol"
 The history of port numbers for TLS in SMTP is a little messy and has been
 .cindex "SMTP" "ssmtp protocol"
 .cindex "SMTP" "smtps protocol"
 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
+contentious.  As of
+&url(https://www.rfc-editor.org/rfc/rfc8314,RFC 8314),
+the common practice of using the historically

 allocated port 465 for "email submission but with TLS immediately upon connect
 instead of using STARTTLS" is officially blessed by the IETF, and recommended
 by them in preference to STARTTLS.
 allocated port 465 for "email submission but with TLS immediately upon connect
 instead of using STARTTLS" is officially blessed by the IETF, and recommended
 by them in preference to STARTTLS.


@@ -29242,7 +29474,8 @@ The default value for &%tls_dhparam%& differs for historical reasons.
 .vindex "&$tls_in_peerdn$&"
 .vindex "&$tls_out_peerdn$&"
 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
 .vindex "&$tls_in_peerdn$&"
 .vindex "&$tls_out_peerdn$&"
 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for

-separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
+separating fields; GnuTLS uses commas, in accordance with
+&url(https://www.rfc-editor.org/rfc/rfc2253,RFC 2253). This

 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
 .next
 OpenSSL identifies cipher suites using hyphens as separators, for example:
 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
 .next
 OpenSSL identifies cipher suites using hyphens as separators, for example:


@@ -29903,7 +30136,9 @@ initiated by Exim.
 .oindex "&%tls_in_sni%&"
 With TLS1.0 or above, there is an extension mechanism by which extra
 information can be included at various points in the protocol.  One of these
 .oindex "&%tls_in_sni%&"
 With TLS1.0 or above, there is an extension mechanism by which extra
 information can be included at various points in the protocol.  One of these

-extensions, documented in RFC 6066 (and before that RFC 4366) is
+extensions, documented in
+&url(https://www.rfc-editor.org/rfc/rfc6066,RFC 6066)
+(and before that &url(https://www.rfc-editor.org/rfc/rfc4366,RFC 4366)) is

 &"Server Name Indication"&, commonly &"SNI"&.  This extension is sent by the
 client in the initial handshake, so that the server can examine the servername
 within and possibly choose to use different certificates and keys (and more)
 &"Server Name Indication"&, commonly &"SNI"&.  This extension is sent by the
 client in the initial handshake, so that the server can examine the servername
 within and possibly choose to use different certificates and keys (and more)


@@ -30238,8 +30473,8 @@ There is no current way to staple a proof for a client certificate.
 .section "TLS Resumption" "SECTresumption"
 .cindex TLS resumption
 TLS Session Resumption for TLS 1.2 and TLS 1.3 connections can be used (defined
 .section "TLS Resumption" "SECTresumption"
 .cindex TLS resumption
 TLS Session Resumption for TLS 1.2 and TLS 1.3 connections can be used (defined

-in RFC 5077 for 1.2).  The support for this requires GnuTLS 3.6.3 or OpenSSL 1.1.1
-(or later).
+in &url(https://www.rfc-editor.org/rfc/rfc5077,RFC 5077) for 1.2).
+The support for this requires GnuTLS 3.6.3 or OpenSSL 1.1.1 (or later).

 
 Session resumption (this is the "stateless" variant) involves the server sending
 a "session ticket" to the client on one connection, which can be stored by the
 
 Session resumption (this is the "stateless" variant) involves the server sending
 a "session ticket" to the client on one connection, which can be stored by the


@@ -30525,12 +30760,19 @@ Section 4.3 of that document.
 .subsection General
 Under GnuTLS, DANE is only supported from version 3.0.0 onwards.
 
 .subsection General
 Under GnuTLS, DANE is only supported from version 3.0.0 onwards.
 

-DANE is specified in published RFCs and decouples certificate authority trust
+DANE is specified in &url(https://www.rfc-editor.org/rfc/rfc6698,RFC 6698).
+It decouples certificate authority trust

 selection from a "race to the bottom" of "you must trust everything for mail
 to get through".
 selection from a "race to the bottom" of "you must trust everything for mail
 to get through".

-There is an alternative technology called MTA-STS, which
-instead publishes MX trust anchor information on an HTTPS website.  At the
-time this text was last updated, MTA-STS was still a draft, not yet an RFC.
+It does retain the need to trust the assurances provided by the DNSSEC tree.
+
+There is an alternative technology called MTA-STS
+(&url(https://www.rfc-editor.org/rfc/rfc8461,RFC 8461)), which
+instead publishes MX trust anchor information on an HTTPS website.
+The discovery of the address for that website does not (per standard)
+require DNSSEC, and could be regarded as being less secure than DANE
+as a result.
+

 Exim has no support for MTA-STS as a client, but Exim mail server operators
 can choose to publish information describing their TLS configuration using
 MTA-STS to let those clients who do use that protocol derive trust
 Exim has no support for MTA-STS as a client, but Exim mail server operators
 can choose to publish information describing their TLS configuration using
 MTA-STS to let those clients who do use that protocol derive trust


@@ -30601,6 +30843,7 @@ options in the main part of the configuration. These options are:
 .cindex "RCPT" "ACL for"
 .cindex "STARTTLS, ACL for"
 .cindex "VRFY" "ACL for"
 .cindex "RCPT" "ACL for"
 .cindex "STARTTLS, ACL for"
 .cindex "VRFY" "ACL for"

+.cindex "WELLKNOWN" "ACL for"

 .cindex "SMTP" "connection, ACL for"
 .cindex "non-SMTP messages" "ACLs for"
 .cindex "MIME content scanning" "ACL for"
 .cindex "SMTP" "connection, ACL for"
 .cindex "non-SMTP messages" "ACLs for"
 .cindex "MIME content scanning" "ACL for"


@@ -30627,6 +30870,7 @@ options in the main part of the configuration. These options are:
 .irow &%acl_smtp_rcpt%&        "ACL for RCPT"
 .irow &%acl_smtp_starttls%&    "ACL for STARTTLS"
 .irow &%acl_smtp_vrfy%&        "ACL for VRFY"
 .irow &%acl_smtp_rcpt%&        "ACL for RCPT"
 .irow &%acl_smtp_starttls%&    "ACL for STARTTLS"
 .irow &%acl_smtp_vrfy%&        "ACL for VRFY"

+.irow &%acl_smtp_wellknown%&   "ACL for WELLKNOWN"

 .endtable
 
 For example, if you set
 .endtable
 
 For example, if you set


@@ -30642,7 +30886,7 @@ trying to deliver the message. It is therefore recommended that you do as much
 testing as possible at RCPT time.
 
 
 testing as possible at RCPT time.
 
 

-.subsection "The non-SMTP ACLs" SECID190
+.subsection "The non-SMTP ACLs" SECnonSMTP

 .cindex "non-SMTP messages" "ACLs for"
 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
 .cindex "non-SMTP messages" "ACLs for"
 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not


@@ -30676,7 +30920,7 @@ kind of rejection is treated as permanent, because there is no way of sending a
 temporary error for these kinds of message.
 
 
 temporary error for these kinds of message.
 
 

-.subsection "The SMTP connect ACL" SECID191
+.subsection "The SMTP connect ACL" SECconnectACL

 .cindex "SMTP" "connection, ACL for"
 .oindex &%smtp_banner%&
 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
 .cindex "SMTP" "connection, ACL for"
 .oindex &%smtp_banner%&
 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP


@@ -30691,7 +30935,7 @@ is accepted; if the ACL does not accept then the TCP connection is dropped witho
 any TLS startup attempt and without any SMTP response being transmitted.
 
 
 any TLS startup attempt and without any SMTP response being transmitted.
 
 

-.subsection "The EHLO/HELO ACL" SECID192
+.subsection "The EHLO/HELO ACL" SECheloACL

 .cindex "EHLO" "ACL for"
 .cindex "HELO" "ACL for"
 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
 .cindex "EHLO" "ACL for"
 .cindex "HELO" "ACL for"
 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an


@@ -30712,7 +30956,7 @@ affect the EHLO options that are listed on the second and subsequent lines of
 an EHLO response.
 
 
 an EHLO response.
 
 

-.subsection "The DATA ACLs" SECID193
+.subsection "The DATA ACLs" SECdataACLS

 .cindex "DATA" "ACLs for"
 Two ACLs are associated with the DATA command, because it is two-stage
 command, with two responses being sent to the client.
 .cindex "DATA" "ACLs for"
 Two ACLs are associated with the DATA command, because it is two-stage
 command, with two responses being sent to the client.


@@ -30755,6 +30999,10 @@ and the &%acl_smtp_mime%& ACLs.
 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
 enabled (which is the default).
 
 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
 enabled (which is the default).
 

+If, for a specific message, an ACL control
+&*dkim_disable_verify*&
+has been set, this &%acl_smtp_dkim%& ACL is not called.
+

 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
 received, and is executed for each DKIM signature found in a message.  If not
 otherwise specified, the default action is to accept.
 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
 received, and is executed for each DKIM signature found in a message.  If not
 otherwise specified, the default action is to accept.


@@ -30805,6 +31053,64 @@ This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
 If the ACL is not defined, processing completes as if
 the feature was not requested by the client.
 
 If the ACL is not defined, processing completes as if
 the feature was not requested by the client.
 

+.subsection "The SMTP WELLKNOWN ACL" SECTWELLKNOWNACL
+.cindex "WELLKNOWN" "ACL for"
+.oindex "&%acl_smtp_wellknown%&"
+The &%acl_smtp_wellknown%& ACL is available only when Exim is compiled
+with WELLKNOWN support enabled.
+
+The ACL determines the response to an SMTP WELLKNOWN command, using the normal
+accept/defer/deny verbs for the response code,
+and a new &"control=wellknown"& modifier.
+This modifier takes a single option, separated by a '/'
+character, which must be the name of a file containing the response
+cleartext.  The modifier is expanded before use in the usual way before
+it is used.  The configuration is responsible for picking a suitable file
+to return and, most importantly, not returning any unexpected file.
+The argument for the SMTP verb will be available in the &$smtp_command_argument$&
+variable and can be used for building the file path.
+If the file path given in the modifier is empty or inacessible, the control will
+fail.
+
+For example:
+.code
+ check_wellknown:
+  accept control = wellknown/\
+                   ${lookup {${xtextd:$smtp_command_argument}} \
+                       dsearch,key=path,filter=file,ret=full \
+                       {$spooldir/wellknown.d}}
+.endd
+File content will be encoded in &"xtext"& form, and line-wrapping
+for line-length limitation will be done before transmission.
+A response summary line will be prepended, with the (pre-encoding) file size.
+
+The above example uses the expansion operator ${xtextd:<coded-string>}
+which is needed to decode the xtext-encoded key from the SMTP verb.
+
+Under the util directory there is a "mailtest" utility which can be used
+to test/retrieve WELLKNOWN items. Syntax is
+.code
+  mailtest -h host.example.com -w security.txt
+.endd
+
+WELLKNOWN is a ESMTP extension providing access to extended
+information about the server.  It is modelled on the webserver
+facilities documented in
+&url(https://www.rfc-editor.org/rfc/rfc8615,RFC 8615)
+and can be used for a security.txt file
+and could be used for ACME handshaking
+(&url(https://www.rfc-editor.org/rfc/rfc8555,RFC 8555)).
+
+Exim will advertise WELLKNOWN support in the EHLO response
+.oindex &%wellknown_advertise_hosts%&
+(conditional on a new option &%wellknown_advertise_hosts%&)
+and service WELLKNOWN smtp verbs having a single parameter
+giving a key for an item of "site-wide metadata".
+The verb and key are separated by whitespace,
+and the key is xtext-encoded
+(per &url(https://www.rfc-editor.org/rfc/rfc3461,RFC 3461) section 4).
+
+

 .subsection "The QUIT ACL" SECTQUITACL
 .cindex "QUIT, ACL for"
 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
 .subsection "The QUIT ACL" SECTQUITACL
 .cindex "QUIT, ACL for"
 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL


@@ -30878,8 +31184,11 @@ 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
-an RFC 8314 &"submissions"& service on port 465. You can use a string
+providing an
+&url(https://www.rfc-editor.org/rfc/rfc4409,RFC 4409)
+message &"submission"& service on port 587 and an
+&url(https://www.rfc-editor.org/rfc/rfc8314,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.
 


@@ -30975,12 +31284,13 @@ For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
 when the ACL is not defined is &"accept"&.
 
 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
 when the ACL is not defined is &"accept"&.
 

-For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
-&%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
-This means that &%acl_smtp_rcpt%& must be defined in order to receive any
-messages over an SMTP connection. For an example, see the ACL in the default
-configuration file.
-
+For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&,
+&%acl_smtp_vrfy%&
+and &%acl_smtp_wellknown%&),
+the action when the ACL
+is not defined is &"deny"&.  This means that &%acl_smtp_rcpt%& must be
+defined in order to receive any messages over an SMTP connection.
+For an example, see the ACL in the default configuration file.

 
 
 
 
 
 


@@ -31052,7 +31362,8 @@ option to do this.)
 .section "Format of an ACL" "SECID199"
 .cindex "&ACL;" "format of"
 .cindex "&ACL;" "verbs, definition of"
 .section "Format of an ACL" "SECID199"
 .cindex "&ACL;" "format of"
 .cindex "&ACL;" "verbs, definition of"

-An individual ACL consists of a number of statements. Each statement starts
+An individual ACL definition consists of a number of statements.
+Each statement starts

 with a verb, optionally followed by a number of conditions and &"modifiers"&.
 Modifiers can change the way the verb operates, define error and log messages,
 set variables, insert delays, and vary the processing of accepted messages.
 with a verb, optionally followed by a number of conditions and &"modifiers"&.
 Modifiers can change the way the verb operates, define error and log messages,
 set variables, insert delays, and vary the processing of accepted messages.


@@ -31071,6 +31382,9 @@ happens then depends on the verb (and in one case, on a special modifier). Not
 all the conditions make sense at every testing point. For example, you cannot
 test a sender address in the ACL that is run for a VRFY command.
 
 all the conditions make sense at every testing point. For example, you cannot
 test a sender address in the ACL that is run for a VRFY command.
 

+The definition of an ACL ends where another starts,
+or a different configuration section starts.
+

 
 .section "ACL verbs" "SECID200"
 The ACL verbs are as follows:
 
 .section "ACL verbs" "SECID200"
 The ACL verbs are as follows:


@@ -31867,12 +32181,17 @@ This control turns off DKIM verification processing entirely.  For details on
 the operation and configuration of DKIM, see section &<<SECDKIM>>&.
 
 
 the operation and configuration of DKIM, see section &<<SECDKIM>>&.
 
 

-.vitem &*control&~=&~dmarc_disable_verify*&
+.vitem &*control&~=&~dmarc_disable_verify*& &&&
+       &*control&~=&~dmarc_enable_forensic*&

 .cindex "disable DMARC verify"
 .cindex "disable DMARC verify"

-.cindex "DMARC" "disable verify"
-This control turns off DMARC verification processing entirely.  For details on
+.cindex DMARC "disable verify"
+.cindex DMARC controls
+.cindex DMARC "forensic mails"
+These control affect DMARC processing.  For details on

 the operation and configuration of DMARC, see section &<<SECDMARC>>&.
 
 the operation and configuration of DMARC, see section &<<SECDMARC>>&.
 

+The &"disable"& turns off DMARC verification processing entirely.
+

 
 .vitem &*control&~=&~dscp/*&<&'value'&>
 .cindex "&ACL;" "setting DSCP value"
 
 .vitem &*control&~=&~dscp/*&<&'value'&>
 .cindex "&ACL;" "setting DSCP value"


@@ -31981,11 +32300,15 @@ to be useful in production.
 .cindex "multiline responses, suppressing"
 This control is permitted for any ACL except the one for non-SMTP messages.
 It seems that there are broken clients in use that cannot handle multiline
 .cindex "multiline responses, suppressing"
 This control is permitted for any ACL except the one for non-SMTP messages.
 It seems that there are broken clients in use that cannot handle multiline

-SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
+SMTP responses, despite the fact that
+&url(https://www.rfc-editor.org/rfc/rfc821,RFC 821)
+defined them over 20 years ago.

 
 If this control is set, multiline SMTP responses from ACL rejections are
 suppressed. One way of doing this would have been to put out these responses as
 
 If this control is set, multiline SMTP responses from ACL rejections are
 suppressed. One way of doing this would have been to put out these responses as

-one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
+one long line. However,
+&url(https://www.rfc-editor.org/rfc/rfc2821,RFC 2821)
+specifies a maximum of 512 bytes per response

 (&"use multiline responses for more"& it says &-- ha!), and some of the
 responses might get close to that. So this facility, which is after all only a
 sop to broken clients, is implemented by doing two very easy things:
 (&"use multiline responses for more"& it says &-- ha!), and some of the
 responses might get close to that. So this facility, which is after all only a
 sop to broken clients, is implemented by doing two very easy things:


@@ -32081,6 +32404,11 @@ that are being submitted at the same time using &%-bs%& or &%-bS%&.
 This control enables conversion of UTF-8 in message envelope addresses
 to a-label form.
 For details see section &<<SECTi18nMTA>>&.
 This control enables conversion of UTF-8 in message envelope addresses
 to a-label form.
 For details see section &<<SECTi18nMTA>>&.

+
+.vitem &*control&~=&~wellknown*&
+This control sets up a response data file for a WELLKNOWN SMTP command.
+It may only be used in an ACL servicing that command.
+For details see section &<<SECTWELLKNOWNACL>>&.

 .endlist vlist
 
 
 .endlist vlist
 
 


@@ -33804,8 +34132,9 @@ updated in this circumstance.
 .cindex "callout" "full postmaster check"
 This operates like the &%postmaster%& option (see below), but if the check for
 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
 .cindex "callout" "full postmaster check"
 This operates like the &%postmaster%& option (see below), but if the check for
 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in

-accordance with the specification in RFC 2821. The RFC states that the
-unqualified address &'postmaster'& should be accepted.
+accordance with the specification in
+&url(https://www.rfc-editor.org/rfc/rfc2821,RFC 2821).
+The RFC states that the unqualified address &'postmaster'& should be accepted.

 
 
 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
 
 
 .vitem &*mailfrom&~=&~*&<&'email&~address'&>


@@ -35070,13 +35399,11 @@ If the string does not start with a slash, it is used as the
 filename, and the default path is then used.
 .endlist
 The &%decode%& condition normally succeeds. It is only false for syntax
 filename, and the default path is then used.
 .endlist
 The &%decode%& condition normally succeeds. It is only false for syntax

-errors or unusual circumstances such as memory shortages. You can easily decode
-a file with its original, proposed filename using
-.code
-decode = $mime_filename
-.endd
-However, you should keep in mind that &$mime_filename$& might contain
-anything. If you place files outside of the default path, they are not
+errors or unusual circumstances such as memory shortages.
+The variable &$mime_filename$& will have the suggested name for the file.
+Note however that this might contain anything, and is very difficult
+to safely use as all or even part of the filename.
+If you place files outside of the default path, they are not

 automatically unlinked.
 
 For RFC822 attachments (these are messages attached to messages, with a
 automatically unlinked.
 
 For RFC822 attachments (these are messages attached to messages, with a


@@ -35179,8 +35506,8 @@ containing the decoded data.
 This is perhaps the most important of the MIME variables. It contains a
 proposed filename for an attachment, if one was found in either the
 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
 This is perhaps the most important of the MIME variables. It contains a
 proposed filename for an attachment, if one was found in either the
 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be

-RFC2047
-or RFC2231
+&url(https://www.rfc-editor.org/rfc/rfc2047,RFC 2047) or
+&url(https://www.rfc-editor.org/rfc/rfc2231,RFC 2231)

 decoded, but no additional sanity checks are done.
  If no filename was
 found, this variable contains the empty string.
 decoded, but no additional sanity checks are done.
  If no filename was
 found, this variable contains the empty string.


@@ -35786,7 +36113,7 @@ The third argument may be NULL, in which case the &%-oMas%& option is omitted.
 
 
 .vitem &*void&~debug_printf(char&~*,&~...)*&
 
 
 .vitem &*void&~debug_printf(char&~*,&~...)*&

-This is Exim's debugging function, with arguments as for &'(printf()'&. The
+This is Exim's debugging function, with arguments as for &'printf()'&. The

 output is written to the standard error stream. If no debugging is selected,
 calls to &'debug_printf()'& have no effect. Normally, you should make calls
 conditional on the &`local_scan`& debug selector by coding like this:
 output is written to the standard error stream. If no debugging is selected,
 calls to &'debug_printf()'& have no effect. Normally, you should make calls
 conditional on the &`local_scan`& debug selector by coding like this:


@@ -35941,7 +36268,8 @@ address.
 .vlist
 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
   &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
 .vlist
 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
   &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"

-This function decodes strings that are encoded according to RFC 2047. Typically
+This function decodes strings that are encoded according to
+&url(https://www.rfc-editor.org/rfc/rfc2047,RFC 2047). Typically

 these are the contents of header lines. First, each &"encoded word"& is decoded
 from the Q or B encoding into a byte-string. Then, if provided with the name of
 a charset encoding, and if the &[iconv()]& function is available, an attempt is
 these are the contents of header lines. First, each &"encoded word"& is decoded
 from the Q or B encoding into a byte-string. Then, if provided with the name of
 a charset encoding, and if the &[iconv()]& function is available, an attempt is


@@ -36273,7 +36601,8 @@ headers remove <string>
 .endd
 The argument for the &%headers add%& is a string that is expanded and then
 added to the end of the message's headers. It is the responsibility of the
 .endd
 The argument for the &%headers add%& is a string that is expanded and then
 added to the end of the message's headers. It is the responsibility of the

-filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
+filter maintainer to make sure it conforms to
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) syntax. Leading white

 space is ignored, and if the string is otherwise empty, or if the expansion is
 forced to fail, the command has no effect.
 
 space is ignored, and if the string is otherwise empty, or if the expansion is
 forced to fail, the command has no effect.
 


@@ -36493,7 +36822,8 @@ spoof another's address.
 .cindex "line endings"
 .cindex "carriage return"
 .cindex "linefeed"
 .cindex "line endings"
 .cindex "carriage return"
 .cindex "linefeed"

-RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
+&url(https://www.rfc-editor.org/rfc/rfc2821,RFC 2821)
+specifies that CRLF (two characters: carriage-return, followed by

 linefeed) is the line ending for messages transmitted over the Internet using
 SMTP over TCP/IP. However, within individual operating systems, different
 conventions are used. For example, Unix-like systems use just LF, but others
 linefeed) is the line ending for messages transmitted over the Internet using
 SMTP over TCP/IP. However, within individual operating systems, different
 conventions are used. For example, Unix-like systems use just LF, but others


@@ -36577,7 +36907,9 @@ with a line containing the envelope sender and a timestamp, following the word
 From a.oakley@berlin.mus Fri Jan  5 12:35 GMT 1996
 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
 .endd
 From a.oakley@berlin.mus Fri Jan  5 12:35 GMT 1996
 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
 .endd

-This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
+This line precedes the
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+header lines. For compatibility with Sendmail,

 Exim recognizes such lines at the start of messages that are submitted to it
 via the command line (that is, on the standard input). It does not recognize
 such lines in incoming SMTP messages, unless the sending host matches
 Exim recognizes such lines at the start of messages that are submitted to it
 via the command line (that is, on the standard input). It does not recognize
 such lines in incoming SMTP messages, unless the sending host matches


@@ -36591,7 +36923,9 @@ that follows &"From"& into &$1$&.
 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
 a trusted user, the message's sender address is constructed by expanding the
 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
 a trusted user, the message's sender address is constructed by expanding the
 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is

-then parsed as an RFC 2822 address. If there is no domain, the local part is
+then parsed as an
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+address. If there is no domain, the local part is

 qualified with &%qualify_domain%& unless it is the empty string. However, if
 the command line &%-f%& option is used, it overrides the &"From"& line.
 
 qualified with &%qualify_domain%& unless it is the empty string. However, if
 the command line &%-f%& option is used, it overrides the &"From"& line.
 


@@ -36609,7 +36943,8 @@ incoming SMTP message from a source that is not permitted to send them.
 .section "Header lines"
 .subsection "Resent- header lines" SECID220
 .chindex Resent-
 .section "Header lines"
 .subsection "Resent- header lines" SECID220
 .chindex Resent-

-RFC 2822 makes provision for sets of header lines starting with the string
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+makes provision for sets of header lines starting with the string

 &`Resent-`& to be added to a message when it is resent by the original
 recipient to somebody else. These headers are &'Resent-Date:'&,
 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
 &`Resent-`& to be added to a message when it is resent by the original
 recipient to somebody else. These headers are &'Resent-Date:'&,
 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,


@@ -36672,8 +37007,10 @@ Exim adds one, using the current date and time, unless the
 .subsection Delivery-date: SECID224
 .cindex "&'Delivery-date:'& header line"
 .oindex "&%delivery_date_remove%&"
 .subsection Delivery-date: SECID224
 .cindex "&'Delivery-date:'& header line"
 .oindex "&%delivery_date_remove%&"

-&'Delivery-date:'& header lines are not part of the standard RFC 2822 header
-set. Exim can be configured to add them to the final delivery of messages. (See
+&'Delivery-date:'& header lines are not part of the standard
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+header set.
+Exim can be configured to add them to the final delivery of messages. (See

 the generic &%delivery_date_add%& transport option.) They should not be present
 in messages in transit. If the &%delivery_date_remove%& configuration option is
 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
 the generic &%delivery_date_add%& transport option.) They should not be present
 in messages in transit. If the &%delivery_date_remove%& configuration option is
 set (the default), Exim removes &'Delivery-date:'& header lines from incoming


@@ -36683,7 +37020,8 @@ messages.
 .subsection Envelope-to: SECID225
 .chindex Envelope-to:
 .oindex "&%envelope_to_remove%&"
 .subsection Envelope-to: SECID225
 .chindex Envelope-to:
 .oindex "&%envelope_to_remove%&"

-&'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
+&'Envelope-to:'& header lines are not part of the standard
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822) header set.

 Exim can be configured to add them to the final delivery of messages. (See the
 generic &%envelope_to_add%& transport option.) They should not be present in
 messages in transit. If the &%envelope_to_remove%& configuration option is set
 Exim can be configured to add them to the final delivery of messages. (See the
 generic &%envelope_to_add%& transport option.) They should not be present in
 messages in transit. If the &%envelope_to_remove%& configuration option is set


@@ -36769,8 +37107,11 @@ changed to the time of acceptance, which is (apart from a small delay while the
 .chindex References:
 Messages created by the &(autoreply)& transport include a &'References:'&
 header line. This is constructed according to the rules that are described in
 .chindex References:
 Messages created by the &(autoreply)& transport include a &'References:'&
 header line. This is constructed according to the rules that are described in

-section 3.64 of RFC 2822 (which states that replies should contain such a
-header line), and section 3.14 of RFC 3834 (which states that automatic
+section 3.64 of
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+(which states that replies should contain such a header line),
+and section 3.14 of &url(https://datatracker.ietf.org/doc/html/rfc3834,RFC 3834)
+(which states that automatic

 responses are not different in this respect). However, because some mail
 processing software does not cope well with very long header lines, no more
 than 12 message IDs are copied from the &'References:'& header line in the
 responses are not different in this respect). However, because some mail
 processing software does not cope well with very long header lines, no more
 than 12 message IDs are copied from the &'References:'& header line in the


@@ -36872,8 +37213,9 @@ the transport cannot refer to the modified header lines, because such
 expansions all occur before the message is actually transported.
 
 For both routers and transports, the argument of a &%headers_add%&
 expansions all occur before the message is actually transported.
 
 For both routers and transports, the argument of a &%headers_add%&

-option must be in the form of one or more RFC 2822 header lines, separated by
-newlines (coded as &"\n"&). For example:
+option must be in the form of one or more
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+header lines, separated by newlines (coded as &"\n"&). For example:

 .code
 headers_add = X-added-header: added by $primary_hostname\n\
               X-added-second: another added header line
 .code
 headers_add = X-added-header: added by $primary_hostname\n\
               X-added-second: another added header line


@@ -36984,9 +37326,12 @@ The &%unknown_username%& option can be used to specify user names in cases when
 there is no password file entry.
 
 .cindex "RFC 2047"
 there is no password file entry.
 
 .cindex "RFC 2047"

-In all cases, the user name is made to conform to RFC 2822 by quoting all or
+In all cases, the user name is made to conform to
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+by quoting all or

 parts of it if necessary. In addition, if it contains any non-printing
 parts of it if necessary. In addition, if it contains any non-printing

-characters, it is encoded as described in RFC 2047, which defines a way of
+characters, it is encoded as described in
+&url(https://www.rfc-editor.org/rfc/rfc2047,RFC 2047), which defines a way of

 including non-ASCII characters in header lines. The value of the
 &%headers_charset%& option specifies the name of the encoding that is used (the
 characters are assumed to be in this encoding). The setting of
 including non-ASCII characters in header lines. The value of the
 &%headers_charset%& option specifies the name of the encoding that is used (the
 characters are assumed to be in this encoding). The setting of


@@ -36998,7 +37343,8 @@ is, with codes greater than 127) count as printing characters or not.
 .section "Case of local parts" "SECID230"
 .cindex "case of local parts"
 .cindex "local part" "case of"
 .section "Case of local parts" "SECID230"
 .cindex "case of local parts"
 .cindex "local part" "case of"

-RFC 2822 states that the case of letters in the local parts of addresses cannot
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+states that the case of letters in the local parts of addresses cannot

 be assumed to be non-significant. Exim preserves the case of local parts of
 addresses, but by default it uses a lower-cased form when it is routing,
 because on most Unix systems, usernames are in lower case and case-insensitive
 be assumed to be non-significant. Exim preserves the case of local parts of
 addresses, but by default it uses a lower-cased form when it is routing,
 because on most Unix systems, usernames are in lower case and case-insensitive


@@ -37030,7 +37376,8 @@ local parts with the correct case in a case-sensitive manner.
 .section "Dots in local parts" "SECID231"
 .cindex "dot" "in local part"
 .cindex "local part" "dots in"
 .section "Dots in local parts" "SECID231"
 .cindex "dot" "in local part"
 .cindex "local part" "dots in"

-RFC 2822 forbids empty components in local parts. That is, an unquoted local
+&url(https://www.rfc-editor.org/rfc/rfc2822,RFC 2822)
+forbids empty components in local parts. That is, an unquoted local

 part may not begin or end with a dot, nor have two consecutive dots in the
 middle. However, it seems that many MTAs do not enforce this, so Exim permits
 empty components for compatibility.
 part may not begin or end with a dot, nor have two consecutive dots in the
 middle. However, it seems that many MTAs do not enforce this, so Exim permits
 empty components for compatibility.


@@ -37133,8 +37480,9 @@ transport filter. If &%size_addition%& is set negative, the use of SIZE is
 suppressed.
 
 If the remote server advertises support for PIPELINING, Exim uses the
 suppressed.
 
 If the remote server advertises support for PIPELINING, Exim uses the

-pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
-required for the transaction.
+pipelining extension to SMTP
+(&url(https://datatracker.ietf.org/doc/html/rfc2197,RFC 2197))
+to reduce the number of TCP/IP packets required for the transaction.

 
 If the remote server advertises support for the STARTTLS command, and Exim
 was built to support TLS encryption, it tries to start a TLS session unless the
 
 If the remote server advertises support for the STARTTLS command, and Exim
 was built to support TLS encryption, it tries to start a TLS session unless the


@@ -37177,12 +37525,8 @@ See the next section for more detail about error handling.
 .cindex "SMTP" "batching over TCP/IP"
 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
 looks in the hints database for the transport to see if there are any queued
 .cindex "SMTP" "batching over TCP/IP"
 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
 looks in the hints database for the transport to see if there are any queued

-messages waiting for the host to which it is connected. If it finds one, it
-creates a new Exim process using the &%-MC%& option (which can only be used by
-a process running as root or the Exim user) and passes the TCP/IP socket to it
-so that it can deliver another message using the same socket. The new process
-does only those deliveries that are routed to the connected host, and may in
-turn pass the socket on to a third process, and so on.
+messages waiting for the host to which it is connected.
+If it finds one, it arranges to attempt that message on the same connection.

 
 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
 limit the number of messages sent down a single TCP/IP connection.
 
 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
 limit the number of messages sent down a single TCP/IP connection.


@@ -37520,7 +37864,16 @@ RCPT failures.
 .subsection "The ETRN command" SECTETRN
 .cindex "ETRN" "processing"
 .cindex "ESMTP extensions" ETRN
 .subsection "The ETRN command" SECTETRN
 .cindex "ETRN" "processing"
 .cindex "ESMTP extensions" ETRN

-RFC 1985 describes an ESMTP command called ETRN that is designed to
+Most modern installations never need to use this.
+It is used for managing messages queued for an intermittently-connecting
+destination (eg. one using a dialup connection).
+
+.oindex "&%acl_smtp_etrn%&"
+The command is only available if permitted by an ACL
+specfied by the main-section &%acl_smtp_etrn%& option.
+
+&url(https://www.rfc-editor.org/rfc/rfc1985,RFC 1985)
+describes an ESMTP command called ETRN that is designed to

 overcome the security problems of the TURN command (which has fallen into
 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
 overcome the security problems of the TURN command (which has fallen into
 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command


@@ -38709,7 +39062,7 @@ calls at each internal newline, and also after a maximum of
 870 data characters. (This allows for a total syslog line length of 1024, when
 additions such as timestamps are added.) If you are running a syslog
 replacement that can handle lines longer than the 1024 characters allowed by
 870 data characters. (This allows for a total syslog line length of 1024, when
 additions such as timestamps are added.) If you are running a syslog
 replacement that can handle lines longer than the 1024 characters allowed by

-RFC 3164, you should set
+&url(https://www.rfc-editor.org/rfc/rfc3164,RFC 3164), you should set

 .code
 SYSLOG_LONG_LINES=yes
 .endd
 .code
 SYSLOG_LONG_LINES=yes
 .endd


@@ -39200,17 +39553,19 @@ because the arguments are checked before the configuration file is read. The
 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
 between the caller and Exim.
 .next
 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
 between the caller and Exim.
 .next

-.cindex "log" "connection identifier"
-&%connection_identifier%&: An identifier for the accepted connection is added to
+.cindex log "connection identifier"
+.cindex connection "identifier logging"
+&%connection_id%&: An identifier for the accepted connection is added to

 connection start and end lines and to message accept lines.
 The identifier is tagged by Ci=.
 The value is PID-based, so will reset on reboot and will wrap.
 .next
 connection start and end lines and to message accept lines.
 The identifier is tagged by Ci=.
 The value is PID-based, so will reset on reboot and will wrap.
 .next

-.cindex "log" "connection rejections"
+.cindex log "connection rejections"
+.cindex connection "rejection logging"

 &%connection_reject%&: A log entry is written whenever an incoming SMTP
 connection is rejected, for whatever reason.
 .next
 &%connection_reject%&: A log entry is written whenever an incoming SMTP
 connection is rejected, for whatever reason.
 .next

-.cindex "log" "delayed delivery"
+.cindex log "delayed delivery"

 .cindex "delayed delivery, logging"
 &%delay_delivery%&: A log entry is written whenever a delivery process is not
 started for an incoming message because the load is too high or too many
 .cindex "delayed delivery, logging"
 &%delay_delivery%&: A log entry is written whenever a delivery process is not
 started for an incoming message because the load is too high or too many


@@ -39236,10 +39591,8 @@ verifies successfully a tag of DKIM is added, with one of the verified domains.
 .cindex log "DKIM verification"
 .cindex DKIM "verification logging"
 &%dkim_verbose%&: A log entry is written for each attempted DKIM verification.
 .cindex log "DKIM verification"
 .cindex DKIM "verification logging"
 &%dkim_verbose%&: A log entry is written for each attempted DKIM verification.

-.new

 Also, on message delivery lines signing information (domain and selector)
 is added, tagged with DKIM=.
 Also, on message delivery lines signing information (domain and selector)
 is added, tagged with DKIM=.

-.wen

 .next
 .cindex "log" "dnslist defer"
 .cindex "DNS list" "logging defer"
 .next
 .cindex "log" "dnslist defer"
 .cindex "DNS list" "logging defer"


@@ -39306,7 +39659,8 @@ added to log entries and &'Received:'& header lines, following the IP address
 in square brackets, and separated from it by a colon. This is implemented by
 changing the value that is put in the &$sender_fullhost$& and
 &$sender_rcvhost$& variables. Recording the remote port number has become more
 in square brackets, and separated from it by a colon. This is implemented by
 changing the value that is put in the &$sender_fullhost$& and
 &$sender_rcvhost$& variables. Recording the remote port number has become more

-important with the widening use of NAT (see RFC 2505).
+important with the widening use of NAT
+(see &url(https://www.rfc-editor.org/rfc/rfc2505,RFC 2505)).

 .next
 .cindex "log" "dropped connection"
 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
 .next
 .cindex "log" "dropped connection"
 &%lost_incoming_connection%&: A log line is written when an incoming SMTP


@@ -40134,8 +40488,6 @@ for remote hosts
 The &'misc'& database is used for
 
 .ilist
 The &'misc'& database is used for
 
 .ilist

-Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
-.next

 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
 &(smtp)& transport)
 .next
 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
 &(smtp)& transport)
 .next


@@ -40143,11 +40495,13 @@ Limiting the concurrency of specific transports (when &%max_parallel%& is set
 in a transport)
 .next
 Recording EHLO-time facilities advertised by hosts
 in a transport)
 .next
 Recording EHLO-time facilities advertised by hosts

+.next
+Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)

 .endlist
 
 
 
 .endlist
 
 
 

-.section "exim_dumpdb" "SECTdumpdb"
+.subsection "exim_dumpdb" "SECTdumpdb"

 .cindex "&'exim_dumpdb'&"
 The entire contents of a database are written to the standard output by the
 &'exim_dumpdb'& program,
 .cindex "&'exim_dumpdb'&"
 The entire contents of a database are written to the standard output by the
 &'exim_dumpdb'& program,


@@ -40189,7 +40543,7 @@ cross-references.
 
 
 
 
 
 

-.section "exim_tidydb" "SECTtidydb"
+.subsection "exim_tidydb" "SECTtidydb"

 .cindex "&'exim_tidydb'&"
 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
 database. If run with no options, it removes all records that are more than 30
 .cindex "&'exim_tidydb'&"
 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
 database. If run with no options, it removes all records that are more than 30


@@ -40238,7 +40592,7 @@ databases is likely to keep on increasing.
 
 
 
 
 
 

-.section "exim_fixdb" "SECTfixdb"
+.subsection "exim_fixdb" "SECTfixdb"

 .cindex "&'exim_fixdb'&"
 The &'exim_fixdb'& program is a utility for interactively modifying databases.
 Its main use is for testing Exim, but it might also be occasionally useful for
 .cindex "&'exim_fixdb'&"
 The &'exim_fixdb'& program is a utility for interactively modifying databases.
 Its main use is for testing Exim, but it might also be occasionally useful for


@@ -40867,20 +41221,31 @@ will be used during message reception.
 .next
 A queue runner process retains root privilege throughout its execution. Its
 job is to fork a controlled sequence of delivery processes.
 .next
 A queue runner process retains root privilege throughout its execution. Its
 job is to fork a controlled sequence of delivery processes.

+

 .next
 .next

-A delivery process retains root privilege throughout most of its execution,
-but any actual deliveries (that is, the transports themselves) are run in
-subprocesses which always change to a non-root uid and gid. For local
-deliveries this is typically the uid and gid of the owner of the mailbox; for
-remote deliveries, the Exim uid and gid are used. Once all the delivery
+A delivery process retains root privilege throughout most of its execution.,
+including while the recipient addresses in a message are being routed.
+
+.ilist
+However, if a user's filter file has to be processed,
+this is done in a subprocess that runs under the individual user's uid and
+gid. A system filter is run as root unless &%system_filter_user%& is set.
+.endlist
+
+Any actual deliveries (that is, the transports themselves) are run in
+subprocesses which always change to a non-root uid and gid.
+.ilist
+For local
+deliveries this is typically the uid and gid of the owner of the mailbox.
+.next
+For remote deliveries, the Exim uid and gid are used.
+.endlist
+
+Once all the delivery

 subprocesses have been run, a delivery process changes to the Exim uid and gid
 while doing post-delivery tidying up such as updating the retry database and
 generating bounce and warning messages.
 
 subprocesses have been run, a delivery process changes to the Exim uid and gid
 while doing post-delivery tidying up such as updating the retry database and
 generating bounce and warning messages.
 

-While the recipient addresses in a message are being routed, the delivery
-process runs as root. However, if a user's filter file has to be processed,
-this is done in a subprocess that runs under the individual user's uid and
-gid. A system filter is run as root unless &%system_filter_user%& is set.

 .next
 A process that is testing addresses (the &%-bt%& option) runs as root so that
 the routing is done in the same environment as a message delivery.
 .next
 A process that is testing addresses (the &%-bt%& option) runs as root so that
 the routing is done in the same environment as a message delivery.


@@ -41573,7 +41938,7 @@ 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 6376.
+DKIM is documented in &url(https://www.rfc-editor.org/rfc/rfc6376,RFC 6376).

 
 As DKIM relies on the message being unchanged in transit, messages handled
 by a mailing-list (which traditionally adds to the message) will not match
 
 As DKIM relies on the message being unchanged in transit, messages handled
 by a mailing-list (which traditionally adds to the message) will not match


@@ -41586,8 +41951,9 @@ Exim's DKIM implementation allows for
 .olist
 Signing outgoing messages: This function is implemented in the SMTP transport.
 It can co-exist with all other Exim features
 .olist
 Signing outgoing messages: This function is implemented in the SMTP transport.
 It can co-exist with all other Exim features

-(including transport filters)
-except cutthrough delivery.
+(including transport filters) except cutthrough delivery.
+However, signing options may not depend on headers modified by
+routers, the transport or a transport filter.

 .next
 Verifying signatures in incoming messages: This is implemented by an additional
 ACL (acl_smtp_dkim), which can be called several times per message, with
 .next
 Verifying signatures in incoming messages: This is implemented by an additional
 ACL (acl_smtp_dkim), which can be called several times per message, with


@@ -41623,7 +41989,8 @@ senders).
 .cindex DKIM signing
 
 For signing to be usable you must have published a DKIM record in DNS.
 .cindex DKIM signing
 
 For signing to be usable you must have published a DKIM record in DNS.

-Note that RFC 8301 (which does not cover EC keys) says:
+Note that &url(https://www.rfc-editor.org/rfc/rfc8301,RFC 8301)
+(which does not cover EC keys) says:

 .code
 rsa-sha1 MUST NOT be used for signing or verifying.
 
 .code
 rsa-sha1 MUST NOT be used for signing or verifying.
 


@@ -41692,11 +42059,13 @@ To generate keys under OpenSSL:
 openssl genrsa -out dkim_rsa.private 2048
 openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM
 .endd
 openssl genrsa -out dkim_rsa.private 2048
 openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM
 .endd

-The result file from the first command should be retained, and
-this option set to use it.
+The result file from the first command should be retained,
+permissions set so that Exim can read it,
+and this option set to use it.

 Take the base-64 lines from the output of the second command, concatenated,
 for the DNS TXT record.
 Take the base-64 lines from the output of the second command, concatenated,
 for the DNS TXT record.

-See section 3.6 of RFC6376 for the record specification.
+See section 3.6 of &url(https://www.rfc-editor.org/rfc/rfc6376,RFC 6376)
+for the record specification.

 
 Under GnuTLS:
 .code
 
 Under GnuTLS:
 .code


@@ -41704,13 +42073,14 @@ certtool --generate-privkey --rsa --bits=2048 --password='' -8 --outfile=dkim_rs
 certtool --load-privkey=dkim_rsa.private --pubkey-info
 .endd
 
 certtool --load-privkey=dkim_rsa.private --pubkey-info
 .endd
 

-Note that RFC 8301 says:
+Note that &url(https://www.rfc-editor.org/rfc/rfc8301,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
 
 .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
 

-EC keys for DKIM are defined by RFC 8463.
+EC keys for DKIM are defined by
+&url(https://www.rfc-editor.org/rfc/rfc8463,RFC 8463).

 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)
 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)


@@ -41745,7 +42115,7 @@ Can be set to any one of the supported hash methods, which are:
 &`sha512`& &-- possibly more secure but less well supported
 .endlist
 
 &`sha512`& &-- possibly more secure but less well supported
 .endlist
 

-Note that RFC 8301 says:
+Note that &url(https://www.rfc-editor.org/rfc/rfc8301,RFC 8301) says:

 .code
 rsa-sha1 MUST NOT be used for signing or verifying.
 .endd
 .code
 rsa-sha1 MUST NOT be used for signing or verifying.
 .endd


@@ -41775,7 +42145,8 @@ If set, this option must expand to a colon-separated
 list of header names.
 Headers with these names, or the absence of such a header, will be included
 in the message signature.
 list of header names.
 Headers with these names, or the absence of such a header, will be included
 in the message signature.

-When unspecified, the header names listed in RFC4871 will be used,
+When unspecified, the header names listed in
+&url(https://www.rfc-editor.org/rfc/rfc4871,RFC 4871) will be used,

 whether or not each header is present in the message.
 The default list is available for the expansion in the macro
 &"_DKIM_SIGN_HEADERS"&
 whether or not each header is present in the message.
 The default list is available for the expansion in the macro
 &"_DKIM_SIGN_HEADERS"&


@@ -41795,13 +42166,12 @@ name will be appended.
 .option dkim_timestamps smtp integer&!! unset
 This option controls the inclusion of timestamp information in the signature.
 If not set, no such information will be included.
 .option dkim_timestamps smtp integer&!! unset
 This option controls the inclusion of timestamp information in the signature.
 If not set, no such information will be included.

-.new

 Otherwise, must be an unsigned number giving an offset in seconds from the
 current time for the expiry tag (e.g. 1209600 for two weeks); both creation
 (t=) and expiry (x=) tags will be included unless the offset is 0 (no expiry).
 Otherwise, must be an unsigned number giving an offset in seconds from the
 current time for the expiry tag (e.g. 1209600 for two weeks); both creation
 (t=) and expiry (x=) tags will be included unless the offset is 0 (no expiry).

-.wen

 
 

-RFC 6376 lists these tags as RECOMMENDED.
+&url(https://www.rfc-editor.org/rfc/rfc6376,RFC 6376)
+lists these tags as RECOMMENDED.

 
 
 .subsection "Verifying DKIM signatures in incoming mail" SECDKIMVFY
 
 
 .subsection "Verifying DKIM signatures in incoming mail" SECDKIMVFY


@@ -41965,7 +42335,7 @@ may also be 'ed25519-sha256'.
 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
 for EC keys.
 
 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
 for EC keys.
 

-Note that RFC 8301 says:
+Note that &url(https://www.rfc-editor.org/rfc/rfc8301,RFC 8301) says:

 .code
 rsa-sha1 MUST NOT be used for signing or verifying.
 
 .code
 rsa-sha1 MUST NOT be used for signing or verifying.
 


@@ -41987,7 +42357,8 @@ The header canonicalization method. One of 'relaxed' or 'simple'.
 .vitem &%$dkim_copiedheaders%&
 A transcript of headers and their values which are included in the signature
 (copied from the 'z=' tag of the signature).
 .vitem &%$dkim_copiedheaders%&
 A transcript of headers and their values which are included in the signature
 (copied from the 'z=' tag of the signature).

-Note that RFC6376 requires that verification fail if the From: header is
+Note that &url(https://www.rfc-editor.org/rfc/rfc6376,RFC 6376)
+requires that verification fail if the From: header is

 not included in the signature.  Exim does not enforce this; sites wishing
 strict enforcement should code the check explicitly.
 
 not included in the signature.  Exim does not enforce this; sites wishing
 strict enforcement should code the check explicitly.
 


@@ -42036,7 +42407,7 @@ Number of bits in the key.
 Valid only once the key is loaded, which is at the time the header signature
 is verified, which is after the body hash is.
 
 Valid only once the key is loaded, which is at the time the header signature
 is verified, which is after the body hash is.
 

-Note that RFC 8301 says:
+Note that &url(https://www.rfc-editor.org/rfc/rfc8301,RFC 8301) says:

 .code
 Verifiers MUST NOT consider signatures using RSA keys of
 less than 1024 bits as valid signatures.
 .code
 Verifiers MUST NOT consider signatures using RSA keys of
 less than 1024 bits as valid signatures.


@@ -42073,9 +42444,7 @@ for that check for empty &$h_DKIM-Signature:$& in the data ACL.
 ACL condition that checks a colon-separated list of possible DKIM verification
 results against the actual result of verification,
 given by &$dkim_verify_status$& if that is non-empty or "none" if empty.
 ACL condition that checks a colon-separated list of possible DKIM verification
 results against the actual result of verification,
 given by &$dkim_verify_status$& if that is non-empty or "none" if empty.

-.new

 This condition may be used in DKIM, MIME, PRDR and DATA ACLs.
 This condition may be used in DKIM, MIME, PRDR and DATA ACLs.

-.wen

 
 A basic verification might be:
 .code
 
 A basic verification might be:
 .code


@@ -42097,9 +42466,7 @@ see the documentation of the &%$dkim_verify_status%& expansion variable above
 for more information of what they mean.
 
 The condition is true if the status
 for more information of what they mean.
 
 The condition is true if the status

-.new

 (or any of the list of status values)
 (or any of the list of status values)

-.wen

 is any one of the supplied list.
 .endlist
 
 is any one of the supplied list.
 .endlist
 


@@ -42110,7 +42477,8 @@ is any one of the supplied list.
 .cindex SPF verification
 
 SPF is a mechanism whereby a domain may assert which IP addresses may transmit
 .cindex SPF verification
 
 SPF is a mechanism whereby a domain may assert which IP addresses may transmit

-messages with its domain in the envelope from, documented by RFC 7208.
+messages with its domain in the envelope from, documented by
+&url(https://www.rfc-editor.org/rfc/rfc7208,RFC 7208).

 For more information on SPF see &url(http://www.open-spf.org), a static copy of
 the &url(http://openspf.org).
 . --- 2019-10-28: still not https, open-spf.org is told to be a
 For more information on SPF see &url(http://www.open-spf.org), a static copy of
 the &url(http://openspf.org).
 . --- 2019-10-28: still not https, open-spf.org is told to be a


@@ -42124,6 +42492,12 @@ This includes retransmissions done by traditional forwarders.
 SPF verification support is built into Exim if SUPPORT_SPF=yes is set in
 &_Local/Makefile_&.  The support uses the &_libspf2_& library
 &url(https://www.libspf2.org/).
 SPF verification support is built into Exim if SUPPORT_SPF=yes is set in
 &_Local/Makefile_&.  The support uses the &_libspf2_& library
 &url(https://www.libspf2.org/).

+.new
+.cindex "dynamic modules"
+The support can be built as a dynamic-load module if desired;
+see the comments in that Makefile.
+.wen
+

 There is no Exim involvement in the transmission of messages;
 publishing certain DNS records is all that is required.
 
 There is no Exim involvement in the transmission of messages;
 publishing certain DNS records is all that is required.
 


@@ -42396,7 +42770,8 @@ Example usage:
     allow_fail
     data =      :fail: Invalid SRS recipient address
 
     allow_fail
     data =      :fail: Invalid SRS recipient address
 

-  #... further routers here
+  #... further routers here get inbound_srs-redirected recipients
+  # and any that were not SRS'd

 
 
   # transport; should look like the non-forward outbound
 
 
   # transport; should look like the non-forward outbound


@@ -42419,14 +42794,14 @@ Example usage:
 DMARC combines feedback from SPF, DKIM, and header From: in order
 to attempt to provide better indicators of the authenticity of an
 email.  This document does not explain the fundamentals; you
 DMARC combines feedback from SPF, DKIM, and header From: in order
 to attempt to provide better indicators of the authenticity of an
 email.  This document does not explain the fundamentals; you

-should read and understand how it works by visiting the website at
-&url(http://www.dmarc.org/).
+should read and understand how it works by visiting the
+&url(http://www.dmarc.org/,DMARC website).

 
 If Exim is built with DMARC support,
 the libopendmarc library is used.
 
 For building Exim yourself, obtain the library from
 
 If Exim is built with DMARC support,
 the libopendmarc library is used.
 
 For building Exim yourself, obtain the library from

-&url(http://sourceforge.net/projects/opendmarc/)
+&url(http://sourceforge.net/projects/opendmarc/,sourceforge)

 to obtain a copy, or find it in your favorite package
 repository.  You will need to attend to the local/Makefile feature
 SUPPORT_DMARC and the associated LDFLAGS addition.
 to obtain a copy, or find it in your favorite package
 repository.  You will need to attend to the local/Makefile feature
 SUPPORT_DMARC and the associated LDFLAGS addition.


@@ -42740,19 +43115,23 @@ A possible solution is:
 .cindex proxy SOCKS
 .cindex SOCKS proxy
 Exim has support for sending outbound SMTP via a proxy
 .cindex proxy SOCKS
 .cindex SOCKS proxy
 Exim has support for sending outbound SMTP via a proxy

-using a protocol called SOCKS5 (defined by RFC1928).
+using a protocol called SOCKS5 (defined by
+&url(https://www.rfc-editor.org/rfc/rfc1928,RFC 1928)).

 The support can be optionally included by defining SUPPORT_SOCKS=yes in
 Local/Makefile.
 
 Use of a proxy is enabled by setting the &%socks_proxy%& option
 on an smtp transport.
 The support can be optionally included by defining SUPPORT_SOCKS=yes in
 Local/Makefile.
 
 Use of a proxy is enabled by setting the &%socks_proxy%& option
 on an smtp transport.

-The option value is expanded and should then be a list
+.new
+If unset (or empty after expansion) then proxying is not done.
+.wen
+Otherwise, expansion should result in a list

 (colon-separated by default) of proxy specifiers.
 Each proxy specifier is a list
 (space-separated by default) where the initial element
 is an IP address and any subsequent elements are options.
 
 (colon-separated by default) of proxy specifiers.
 Each proxy specifier is a list
 (space-separated by default) where the initial element
 is an IP address and any subsequent elements are options.
 

-Options are a string <name>=<value>.
+Each option is a string of form <name>=<value>.

 The list of options is in the following table:
 .itable none 0 0 2 10* left 90* left
 .irow &'auth'& "authentication method"
 The list of options is in the following table:
 .itable none 0 0 2 10* left 90* left
 .irow &'auth'& "authentication method"


@@ -42770,7 +43149,8 @@ More details on each of these options follows:
 .cindex authentication "to proxy"
 .cindex proxy authentication
 &%auth%&: Either &"none"& (default) or &"name"&.
 .cindex authentication "to proxy"
 .cindex proxy authentication
 &%auth%&: Either &"none"& (default) or &"name"&.

-Using &"name"& selects username/password authentication per RFC 1929
+Using &"name"& selects username/password authentication per
+&url(https://www.rfc-editor.org/rfc/rfc1929,RFC 1929)

 for access to the proxy.
 Default is &"none"&.
 .next
 for access to the proxy.
 Default is &"none"&.
 .next


@@ -42817,7 +43197,11 @@ This will add a component tagged with &"PRX="& to the line.
 
 Exim has support for Internationalised mail names.
 To include this it must be built with SUPPORT_I18N and the libidn library.
 
 Exim has support for Internationalised mail names.
 To include this it must be built with SUPPORT_I18N and the libidn library.

-Standards supported are RFCs 2060, 5890, 6530 and 6533.
+Standards supported are RFCs
+&url(https://www.rfc-editor.org/rfc/rfc2060.html,2060),
+&url(https://www.rfc-editor.org/rfc/rfc5890.html,5890),
+&url(https://www.rfc-editor.org/rfc/rfc6530.html,6530) and
+&url(https://www.rfc-editor.org/rfc/rfc6533.html,6533).

 
 If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not
 instead of it) then IDNA2008 is supported; this adds an extra library
 
 If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not
 instead of it) then IDNA2008 is supported; this adds an extra library


@@ -42919,7 +43303,8 @@ The string is converted from the charset specified by
 the "headers charset" command (in a filter file)
 or &%headers_charset%& main configuration option (otherwise),
 to the
 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,
+modified UTF-7 encoding specified by
+&url(https://www.rfc-editor.org/rfc/rfc2060.html,RFC 2060),

 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
 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


@@ -42982,10 +43367,12 @@ Events have names which correspond to the point in process at which they fire.
 The name is placed in the variable &$event_name$& and the event action
 expansion must check this, as it will be called for every possible event type.
 
 The name is placed in the variable &$event_name$& and the event action
 expansion must check this, as it will be called for every possible event type.
 

+.new

 The current list of events is:
 .itable all 0 0 4 25* left 10* center 15* center 50* left
 .row auth:fail             after    both       "per driver per authentication attempt"
 .row dane:fail              after    transport  "per connection"
 The current list of events is:
 .itable all 0 0 4 25* left 10* center 15* center 50* left
 .row auth:fail             after    both       "per driver per authentication attempt"
 .row dane:fail              after    transport  "per connection"

+.row dns:fail               after    both       "per lookup"

 .row msg:complete           after    main       "per message"
 .row msg:defer              after    transport  "per message per delivery try"
 .row msg:delivery           after    transport  "per recipient"
 .row msg:complete           after    main       "per message"
 .row msg:defer              after    transport  "per message per delivery try"
 .row msg:delivery           after    transport  "per recipient"


@@ -43000,7 +43387,10 @@ The current list of events is:
 .row tls:fail:connect       after    main       "per connection"
 .row smtp:connect           after    transport  "per connection"
 .row smtp:ehlo              after    transport  "per connection"
 .row tls:fail:connect       after    main       "per connection"
 .row smtp:connect           after    transport  "per connection"
 .row smtp:ehlo              after    transport  "per connection"

+.row smtp:fail:protocol     after    main       "per connection"
+.row smtp:fail:syntax       after    main       "per connection"

 .endtable
 .endtable

+.wen

 New event types may be added in future.
 
 The event name is a colon-separated list, defining the type of
 New event types may be added in future.
 
 The event name is a colon-separated list, defining the type of


@@ -43016,9 +43406,11 @@ should define the event action.
 
 An additional variable, &$event_data$&, is filled with information varying
 with the event type:
 
 An additional variable, &$event_data$&, is filled with information varying
 with the event type:

+.new

 .itable all 0 0 2 20* left 80* left
 .row auth:fail           "smtp response"
 .row dane:fail            "failure reason"
 .itable all 0 0 2 20* left 80* left
 .row auth:fail           "smtp response"
 .row dane:fail            "failure reason"

+.row dns:fail             "failure reason, key and lookup-type"

 .row msg:defer            "error string"
 .row msg:delivery         "smtp confirmation message"
 .row msg:fail:internal    "failure reason"
 .row msg:defer            "error string"
 .row msg:delivery         "smtp confirmation message"
 .row msg:fail:internal    "failure reason"


@@ -43030,7 +43422,10 @@ with the event type:
 .row tls:fail:connect     "error string"
 .row smtp:connect         "smtp banner"
 .row smtp:ehlo            "smtp ehlo response"
 .row tls:fail:connect     "error string"
 .row smtp:connect         "smtp banner"
 .row smtp:ehlo            "smtp ehlo response"

+.row smtp:fail:protocol   "error string"
+.row smtp:fail:syntax     "error string"

 .endtable
 .endtable

+.wen

 
 The :defer events populate one extra variable: &$event_defer_errno$&.
 
 
 The :defer events populate one extra variable: &$event_defer_errno$&.
 


@@ -43068,6 +43463,9 @@ chain element received on the connection.
 For OpenSSL it will trigger for every chain element including those
 loaded locally.
 
 For OpenSSL it will trigger for every chain element including those
 loaded locally.
 

+For dns:fail events from dnsdb lookups, a &"defer_never"& option does not
+affect the reporting of DNS_AGAIN.
+

 . ////////////////////////////////////////////////////////////////////////////
 . ////////////////////////////////////////////////////////////////////////////
 
 . ////////////////////////////////////////////////////////////////////////////
 . ////////////////////////////////////////////////////////////////////////////