X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/95dfacf282b0a4f0f595b43bdc997ef0e3ed43ed..ea98874e2a6a5aee2d512f3246f7d3c19c2ec63d:/doc/doc-docbook/spec.xfpt

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index 0fc086d7b..00f0dac02 100644
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -45,14 +45,16 @@
 . Update the Copyright year (only) when changing content.
 . /////////////////////////////////////////////////////////////////////////////
 
-.set previousversion "4.91"
+.set previousversion "4.95"
 .include ./local_params
 
 .set ACL "access control lists (ACLs)"
 .set I   "    "
 
+.set drivernamemax "64"
+
 .macro copyyear
-2018
+2021
 .endmacro
 
 . /////////////////////////////////////////////////////////////////////////////
@@ -161,6 +163,13 @@
 .macro index
 .echo "** Don't use .index; use .cindex or .oindex or .vindex"
 .endmacro
+
+
+. use this for a concept-index entry for a header line
+.macro chindex
+.cindex "&'$1'& header line"
+.cindex "header lines" $1
+.endmacro
 . ////////////////////////////////////////////////////////////////////////////
 
 
@@ -184,7 +193,7 @@
 </revision></revhistory>
 <copyright><year>
 .copyyear
-           </year><holder>University of Cambridge</holder></copyright>
+           </year><holder>The Exim Maintainers</holder></copyright>
 </bookinfo>
 .literal off
 
@@ -193,6 +202,8 @@
 . This chunk of literal XML implements index entries of the form "x, see y" and
 . "x, see also y". However, the DocBook DTD doesn't allow <indexterm> entries
 . at the top level, so we have to put the .chapter directive first.
+
+. These do not turn up in the HTML output, unfortunately.  The PDF does get them.
 . /////////////////////////////////////////////////////////////////////////////
 
 .chapter "Introduction" "CHID1"
@@ -228,6 +239,14 @@
   <secondary>failure report</secondary>
   <see><emphasis>bounce message</emphasis></see>
 </indexterm>
+<indexterm role="concept">
+  <primary>de-tainting</primary>
+  <see><emphasis>tainting, de-tainting</emphasis></see>
+</indexterm>
+<indexterm role="concept">
+  <primary>detainting</primary>
+  <see><emphasis>tainting, de-tainting</emphasis></see>
+</indexterm>
 <indexterm role="concept">
   <primary>dialup</primary>
   <see><emphasis>intermittently connected hosts</emphasis></see>
@@ -318,6 +337,10 @@
   <primary>zero, binary</primary>
   <see><emphasis>binary zero</emphasis></see>
 </indexterm>
+<indexterm role="concept">
+  <primary>headers</primary>
+  <see><emphasis>header lines</emphasis></see>
+</indexterm>
 
 .literal off
 
@@ -743,17 +766,17 @@ the Exim documentation, &"spool"& is always used in the first sense.
 .chapter "Incorporated code" "CHID2"
 .cindex "incorporated code"
 .cindex "regular expressions" "library"
-.cindex "PCRE"
+.cindex "PCRE2"
 .cindex "OpenDMARC"
 A number of pieces of external code are included in the Exim distribution.
 
 .ilist
 Regular expressions are supported in the main Exim program and in the
-Exim monitor using the freely-distributable PCRE library, copyright
-&copy; University of Cambridge. The source to PCRE is no longer shipped with
-Exim, so you will need to use the version of PCRE shipped with your system,
+Exim monitor using the freely-distributable PCRE2 library, copyright
+&copy; University of Cambridge. The source to PCRE2 is not longer shipped with
+Exim, so you will need to use the version of PCRE2 shipped with your system,
 or obtain and install the full version of the library from
-&url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
+&url(https://github.com/PhilipHazel/pcre2/releases).
 .next
 .cindex "cdb" "acknowledgment"
 Support for the cdb (Constant DataBase) lookup method is provided by code
@@ -1394,21 +1417,46 @@ Again, cutthrough delivery counts as a verification.
 .next
 Individual routers can be explicitly skipped when running the routers to
 check an address given in the SMTP EXPN command (see the &%expn%& option).
+
 .next
 If the &%domains%& option is set, the domain of the address must be in the set
 of domains that it defines.
+.cindex "tainted data" "de-tainting"
+A match verifies the variable &$domain$& (which carries tainted data)
+and assigns an untainted value to the &$domain_data$& variable.
+Such an untainted value is often needed in the transport.
+For specifics of the matching operation and the resulting untainted value,
+refer to section &<<SECTdomainlist>>&.
+
+When an untainted value is wanted, use this option
+rather than the generic &%condition%& option.
+
 .next
 .vindex "&$local_part_prefix$&"
+.vindex "&$local_part_prefix_v$&"
 .vindex "&$local_part$&"
 .vindex "&$local_part_suffix$&"
+.vindex "&$local_part_suffix_v$&"
 .cindex affix "router precondition"
 If the &%local_parts%& option is set, the local part of the address must be in
-the set of local parts that it defines. If &%local_part_prefix%& or
+the set of local parts that it defines.
+A match verifies the variable &$local_part$& (which carries tainted data)
+and assigns an untainted value to the &$local_part_data$& variable.
+Such an untainted value is often needed in the transport.
+For specifics of the matching operation and the resulting untainted value,
+refer to section &<<SECTlocparlis>>&.
+
+When an untainted value is wanted, use this option
+rather than the generic &%condition%& option.
+
+If &%local_part_prefix%& or
 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
 part before this check. If you want to do precondition tests on local parts
 that include affixes, you can do so by using a &%condition%& option (see below)
-that uses the variables &$local_part$&, &$local_part_prefix$&, and
-&$local_part_suffix$& as necessary.
+that uses the variables &$local_part$&, &$local_part_prefix$&,
+&$local_part_prefix_v$&, &$local_part_suffix$&
+and &$local_part_suffix_v$& as necessary.
+
 .next
 .vindex "&$local_user_uid$&"
 .vindex "&$local_user_gid$&"
@@ -1418,23 +1466,35 @@ an account on the local host. If this check succeeds, the uid and gid of the
 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
 user's home directory is placed in &$home$&; these values can be used in the
 remaining preconditions.
+
 .next
 If the &%router_home_directory%& option is set, it is expanded at this point,
 because it overrides the value of &$home$&. If this expansion were left till
 later, the value of &$home$& as set by &%check_local_user%& would be used in
 subsequent tests. Having two different values of &$home$& in the same router
 could lead to confusion.
+
 .next
 If the &%senders%& option is set, the envelope sender address must be in the
 set of addresses that it defines.
+
 .next
 If the &%require_files%& option is set, the existence or non-existence of
 specified files is tested.
+
 .next
 .cindex "customizing" "precondition"
 If the &%condition%& option is set, it is evaluated and tested. This option
 uses an expanded string to allow you to set up your own custom preconditions.
 Expanded strings are described in chapter &<<CHAPexpand>>&.
+
+Note that while using
+this option for address matching technically works,
+it does not set any de-tainted values.
+Such values are often needed, either for router-specific options or
+for transport options.
+Using the &%domains%& and &%local_parts%& options is usually the most
+convenient way to obtain them.
 .endlist
 
 
@@ -1685,20 +1745,20 @@ overridden if necessary.
 A C99-capable compiler will be required for the build.
 
 
-.section "PCRE library" "SECTpcre"
-.cindex "PCRE library"
-Exim no longer has an embedded PCRE library as the vast majority of
-modern systems include PCRE as a system library, although you may need to
-install the PCRE package or the PCRE development package for your operating
-system. If your system has a normal PCRE installation the Exim build
+.section "PCRE2 library" "SECTpcre"
+.cindex "PCRE2 library"
+Exim no longer has an embedded regular-expression library as the vast majority of
+modern systems include PCRE2 as a system library, although you may need to
+install the PCRE2 package or the PCRE2 development package for your operating
+system. If your system has a normal PCRE2 installation the Exim build
 process will need no further configuration. If the library or the
-headers are in an unusual location you will need to either set the PCRE_LIBS
+headers are in an unusual location you will need to either set the PCRE2_LIBS
 and INCLUDE directives appropriately,
-or set PCRE_CONFIG=yes to use the installed &(pcre-config)& command.
+or set PCRE2_CONFIG=yes to use the installed &(pcre-config)& command.
 If your operating system has no
-PCRE support then you will need to obtain and build the current PCRE
-from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
-More information on PCRE is available at &url(https://www.pcre.org/).
+PCRE2 support then you will need to obtain and build the current PCRE2
+from &url(https://github.com/PhilipHazel/pcre2/releases).
+More information on PCRE2 is available at &url(https://www.pcre.org/).
 
 .section "DBM libraries" "SECTdb"
 .cindex "DBM libraries" "discussion of"
@@ -1888,11 +1948,10 @@ to your &_Local/Makefile_& and rebuild Exim.
 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
 .cindex "TLS" "including support for TLS"
 .cindex "encryption" "including support for"
-.cindex "SUPPORT_TLS"
 .cindex "OpenSSL" "building Exim with"
 .cindex "GnuTLS" "building Exim with"
-Exim can be built to support encrypted SMTP connections, using the STARTTLS
-command as per RFC 2487. It can also support legacy clients that expect to
+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
 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).
@@ -1901,35 +1960,39 @@ If you want to build Exim with TLS support, you must first install either the
 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
 implementing SSL.
 
+If you do not want TLS support you should set
+.code
+DISABLE_TLS=yes
+.endd
+in &_Local/Makefile_&.
+
 If OpenSSL is installed, you should set
 .code
-SUPPORT_TLS=yes
+USE_OPENSL=yes
 TLS_LIBS=-lssl -lcrypto
 .endd
 in &_Local/Makefile_&. You may also need to specify the locations of the
 OpenSSL library and include files. For example:
 .code
-SUPPORT_TLS=yes
+USE_OPENSSL=yes
 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
 TLS_INCLUDE=-I/usr/local/openssl/include/
 .endd
 .cindex "pkg-config" "OpenSSL"
 If you have &'pkg-config'& available, then instead you can just use:
 .code
-SUPPORT_TLS=yes
+USE_OPENSSL=yes
 USE_OPENSSL_PC=openssl
 .endd
 .cindex "USE_GNUTLS"
 If GnuTLS is installed, you should set
 .code
-SUPPORT_TLS=yes
 USE_GNUTLS=yes
 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
 .endd
 in &_Local/Makefile_&, and again you may need to specify the locations of the
 library and include files. For example:
 .code
-SUPPORT_TLS=yes
 USE_GNUTLS=yes
 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
 TLS_INCLUDE=-I/usr/gnu/include
@@ -1937,7 +2000,6 @@ TLS_INCLUDE=-I/usr/gnu/include
 .cindex "pkg-config" "GnuTLS"
 If you have &'pkg-config'& available, then instead you can just use:
 .code
-SUPPORT_TLS=yes
 USE_GNUTLS=yes
 USE_GNUTLS_PC=gnutls
 .endd
@@ -2525,11 +2587,32 @@ use of Exim's filtering capabilities, you should make the document entitled
 
 
 
+.section "Running the daemon" SECTdaemonLaunch
+The most common command line for launching the Exim daemon looks like
+.code
+exim -bd -q5m
+.endd
+This starts a daemon which
+.ilist
+listens for incoming smtp connections, launching handler processes for
+each new one
+.next
+starts a queue-runner process every five minutes, to inspect queued messages
+and run delivery attempts on any that have arrived at their retry time
+.endlist
+Should a queue run take longer than the time between queue-runner starts,
+they will run in parallel.
+Numbers of jobs of the various types are subject to policy controls
+defined in the configuration.
+
+
 .section "Upgrading Exim" "SECID36"
 .cindex "upgrading Exim"
 If you are already running Exim on your host, building and installing a new
 version automatically makes it available to MUAs, or any other programs that
 call the MTA directly. However, if you are running an Exim daemon, you do need
+.cindex restart "on HUP signal"
+.cindex signal "HUP, to restart"
 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
 new binary. You do not need to stop processing mail in order to install a new
 version of Exim. The install script does not modify an existing runtime
@@ -2628,6 +2711,7 @@ supplementary group is one of those listed in the &%trusted_groups%&
 configuration option. Note that the Exim group is not automatically trusted.
 
 .cindex '&"From"& line'
+.cindex "envelope from"
 .cindex "envelope sender"
 Trusted users are always permitted to use the &%-f%& option or a leading
 &"From&~"& line to specify the envelope sender of a message that is passed to
@@ -2635,10 +2719,8 @@ Exim through the local interface (see the &%-bm%& and &%-f%& options below).
 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
 users to set envelope senders.
 
-.cindex "&'From:'& header line"
-.cindex "&'Sender:'& header line"
-.cindex "header lines" "From:"
-.cindex "header lines" "Sender:"
+.chindex From:
+.chindex Sender:
 For a trusted user, there is never any check on the contents of the &'From:'&
 header line, and a &'Sender:'& line is never added. Furthermore, any existing
 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
@@ -2767,7 +2849,12 @@ used to specify a path on the command line if a pid file is required.
 
 The SIGHUP signal
 .cindex "SIGHUP"
+.cindex restart "on HUP signal"
+.cindex signal "HUP, to restart"
 .cindex "daemon" "restarting"
+.cindex signal "to reload configuration"
+.cindex daemon "reload configuration"
+.cindex reload configuration
 can be used to cause the daemon to re-execute itself. This should be done
 whenever Exim's configuration file, or any file that is incorporated into it by
 means of the &%.include%& facility, is changed, and also whenever a new version
@@ -2877,6 +2964,7 @@ separate document entitled &'Exim's interfaces to mail filtering'&.
 
 When testing a filter file,
 .cindex "&""From""& line"
+.cindex "envelope from"
 .cindex "envelope sender"
 .oindex "&%-f%&" "for filter testing"
 the envelope sender can be set by the &%-f%& option,
@@ -3661,14 +3749,12 @@ The &`timestamp`& selector causes the current time to be inserted at the start
 of all debug output lines. This can be useful when trying to track down delays
 in processing.
 
-.new
 .cindex debugging "UTF-8 in"
 .cindex UTF-8 "in debug output"
 The &`noutf8`& selector disables the use of
 UTF-8 line-drawing characters to group related information.
 When disabled. ascii-art is used instead.
 Using the &`+all`& option does not set this modifier,
-.wen
 
 If the &%debug_print%& option is set in any driver, it produces output whenever
 any debugging is selected, or if &%-v%& is used.
@@ -3719,6 +3805,7 @@ between &%-F%& and the <&'string'&> is optional.
 .cindex "sender" "address"
 .cindex "address" "sender"
 .cindex "trusted users"
+.cindex "envelope from"
 .cindex "envelope sender"
 .cindex "user" "trusted"
 This option sets the address of the envelope sender of a locally-generated
@@ -3784,9 +3871,11 @@ headers.)
 .cindex "Solaris" "&'mail'& command"
 .cindex "dot" "in incoming non-SMTP message"
 This option, which has the same effect as &%-oi%&, specifies that a dot on a
-line by itself should not terminate an incoming, non-SMTP message. I can find
-no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
-command in Solaris 2.4 uses it. See also &%-ti%&.
+line by itself should not terminate an incoming, non-SMTP message.
+Solaris 2.4 (SunOS 5.4) Sendmail has a similar &%-i%& processing option
+&url(https://docs.oracle.com/cd/E19457-01/801-6680-1M/801-6680-1M.pdf),
+p. 1M-529), and therefore a &%-oi%& command line option, which both are used
+by its &'mailx'& command.
 
 .vitem &%-L%&&~<&'tag'&>
 .oindex "&%-L%&"
@@ -3832,7 +3921,9 @@ id, and the remaining ones must be email addresses. However, if the message is
 active (in the middle of a delivery attempt), it is not altered. This option
 can be used only by an admin user.
 
-.vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
+.vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&&&
+	&~<&'host&~IP'&>&&&
+	&~<&'sequence&~number'&>&&&
         &~<&'message&~id'&>"
 .oindex "&%-MC%&"
 .cindex "SMTP" "passed connection"
@@ -3856,6 +3947,12 @@ This option is not intended for use by external callers. It is used internally
 by Exim in conjunction with the &%-MC%& option. It signifies that the
 remote host supports the ESMTP &_DSN_& extension.
 
+.vitem &%-MCd%&
+.oindex "&%-MCd%&"
+This option is not intended for use by external callers. It is used internally
+by Exim in conjunction with the &%-d%& option
+to pass on an information string on the purpose of the process.
+
 .vitem &%-MCG%&&~<&'queue&~name'&>
 .oindex "&%-MCG%&"
 This option is not intended for use by external callers. It is used internally
@@ -3868,12 +3965,27 @@ This option is not intended for use by external callers. It is used internally
 by Exim in conjunction with the &%-MC%& option. It signifies that a
 remote host supports the ESMTP &_CHUNKING_& extension.
 
+.vitem &%-MCL%&
+.oindex "&%-MCL%&"
+This option is not intended for use by external callers. It is used internally
+by Exim in conjunction with the &%-MC%& option. It signifies that the server to
+which Exim is connected advertised limits on numbers of mails, recipients or
+recipient domains.
+The limits are given by the following three arguments.
+
 .vitem &%-MCP%&
 .oindex "&%-MCP%&"
 This option is not intended for use by external callers. It is used internally
 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
 which Exim is connected supports pipelining.
 
+.vitem &%-MCp%&
+.oindex "&%-MCp%&"
+This option is not intended for use by external callers. It is used internally
+by Exim in conjunction with the &%-MC%& option. It signifies that the connection
+t a remote server is via a SOCKS proxy, using addresses and ports given by
+the following four arguments.
+
 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
 .oindex "&%-MCQ%&"
 This option is not intended for use by external callers. It is used internally
@@ -3883,11 +3995,16 @@ together with the file descriptor number of an open pipe. Closure of the pipe
 signals the final completion of the sequence of processes that are passing
 messages through the same SMTP connection.
 
+.vitem &%-MCq%&&~<&'recipient&~address'&>&~<&'size'&>
+.oindex "&%-MCq%&"
+This option is not intended for use by external callers. It is used internally
+by Exim to implement quota checking for local users.
+
 .vitem &%-MCS%&
 .oindex "&%-MCS%&"
 This option is not intended for use by external callers. It is used internally
 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
-SMTP SIZE option should be used on messages delivered down the existing
+ESMTP SIZE option should be used on messages delivered down the existing
 connection.
 
 .vitem &%-MCT%&
@@ -3896,6 +4013,16 @@ This option is not intended for use by external callers. It is used internally
 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
 host to which Exim is connected supports TLS encryption.
 
+.vitem &%-MCr%&&~<&'SNI'&> &&&
+       &%-MCs%&&~<&'SNI'&>
+.oindex "&%-MCs%&"
+.oindex "&%-MCr%&"
+These options are not intended for use by external callers. It is used internally
+by Exim in conjunction with the &%-MCt%& option, and passes on the fact that
+a TLS Server Name Indication was sent as part of the channel establishment.
+The argument gives the SNI string.
+The "r" variant indicates a DANE-verified connection.
+
 .vitem &%-MCt%&&~<&'IP&~address'&>&~<&'port'&>&~<&'cipher'&>
 .oindex "&%-MCt%&"
 This option is not intended for use by external callers. It is used internally
@@ -3953,6 +4080,18 @@ is sent to the sender, containing the text &"cancelled by administrator"&.
 Bounce messages are just discarded. This option can be used only by an admin
 user.
 
+.vitem &%-MG%&&~<&'queue&~name'&>&~<&'message&~id'&>&~<&'message&~id'&>&~...
+.oindex "&%-MG%&"
+.cindex queue named
+.cindex "named queues" "moving messages"
+.cindex "queue" "moving messages"
+This option requests that each listed message be moved from its current
+queue to the given named queue.
+The destination queue name argument is required, but can be an empty
+string to define the default queue.
+If the messages are not currently located in the default queue,
+a &%-qG<name>%& option will be required to define the source queue.
+
 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
 .oindex "&%-Mmad%&"
 .cindex "delivery" "cancelling all"
@@ -4048,8 +4187,9 @@ the standard output. This option can be used only by an admin user.
 
 .vitem &%-m%&
 .oindex "&%-m%&"
-This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
-treats it that way too.
+This is a synonym for &%-om%& that is accepted by Sendmail
+(&url(https://docs.oracle.com/cd/E19457-01/801-6680-1M/801-6680-1M.pdf)
+p. 1M-258), so Exim treats it that way too.
 
 .vitem &%-N%&
 .oindex "&%-N%&"
@@ -4163,6 +4303,7 @@ forces queueing.
 .vitem &%-odqs%&
 .oindex "&%-odqs%&"
 .cindex "SMTP" "delaying delivery"
+.cindex "first pass routing"
 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
 However, like &%-odb%& and &%-odi%&, this option has no effect if
 &%queue_only_override%& is false and one of the queueing options in the
@@ -4361,6 +4502,15 @@ written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
 without &%-bd%&, this is the only way of causing Exim to write a pid file,
 because in those cases, the normal pid file is not used.
 
+.vitem &%-oPX%&
+.oindex "&%-oPX%&"
+.cindex "pid (process id)" "of daemon"
+.cindex "daemon" "process id (pid)"
+This option is not intended for general use.
+The daemon uses it when terminating due to a SIGTEM, possibly in
+combination with &%-oP%&&~<&'path'&>.
+It causes the pid file to be removed.
+
 .vitem &%-or%&&~<&'time'&>
 .oindex "&%-or%&"
 .cindex "timeout" "for non-SMTP input"
@@ -4393,6 +4543,25 @@ of the syntax, and how it interacts with configuration file options, are given
 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
 file is written unless &%-oP%& is also present to specify a pid filename.
 
+.vitem &%-oY%&
+.oindex &%-oY%&
+.cindex "daemon notifier socket"
+This option controls the creation of an inter-process communications endpoint
+by the Exim daemon.
+It is only relevant when the &%-bd%& (start listening daemon) option is also
+given.
+Normally the daemon creates this socket, unless a &%-oX%& and &*no*& &%-oP%&
+option is also present.
+If this option is given then the socket will not be created.  This could be
+required if the system is running multiple daemons.
+
+The socket is currently used for
+.ilist
+fast ramp-up of queue runner processes
+.next
+obtaining a current queue size
+.endlist
+
 .vitem &%-pd%&
 .oindex "&%-pd%&"
 .cindex "Perl" "starting the interpreter"
@@ -4470,11 +4639,19 @@ appear in the correct order. Each flag is described in a separate item below.
 .cindex "queue" "double scanning"
 .cindex "queue" "routing"
 .cindex "routing" "whole queue before delivery"
+.cindex "first pass routing"
+.cindex "queue runner" "two phase"
 An option starting with &%-qq%& requests a two-stage queue run. In the first
 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
 every domain. Addresses are routed, local deliveries happen, but no remote
 transports are run.
 
+Performance will be best if the &%queue_run_in_order%& option is false.
+If that is so and the &%queue_fast_ramp%& option is true then
+in the first phase of the run,
+once a threshold number of messages are routed for a given host,
+a delivery process is forked in parallel with the rest of the scan.
+
 .cindex "hints database" "remembering routing"
 The hints database that remembers which messages are waiting for specific hosts
 is updated, as if delivery to those hosts had been deferred. After this is
@@ -4520,7 +4697,7 @@ for later delivery.
 .vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
 .oindex "&%-qG%&"
 .cindex queue named
-.cindex "named queues"
+.cindex "named queues"	"deliver from"
 .cindex "queue" "delivering specific messages"
 If the &'G'& flag and a name is present, the queue runner operates on the
 queue with the given name rather than the default queue.
@@ -4653,9 +4830,9 @@ recognized when Exim is run normally. It allows for the setting up of explicit
 .vitem &%-t%&
 .oindex "&%-t%&"
 .cindex "recipient" "extracting from header lines"
-.cindex "&'Bcc:'& header line"
-.cindex "&'Cc:'& header line"
-.cindex "&'To:'& header line"
+.chindex Bcc:
+.chindex Cc:
+.chindex To:
 When Exim is receiving a locally-generated, non-SMTP message on its standard
 input, the &%-t%& option causes the recipients of the message to be obtained
 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
@@ -5347,8 +5524,8 @@ local_interfaces = 127.0.0.1 : ::::1
 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
 
 &*Note*&: Although leading and trailing white space is ignored in individual
-list items, it is not ignored when parsing the list. The space after the first
-colon in the example above is necessary. If it were not there, the list would
+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.
 
 .section "Changing list separators" "SECTlistsepchange"
@@ -5807,7 +5984,7 @@ Libraries you use may depend on specific environment settings.  This
 imposes a security risk (e.g. PATH). There are two lists:
 &%keep_environment%& for the variables to import as they are, and
 &%add_environment%& for variables we want to set to a fixed value.
-Note that TZ is handled separately, by the $%timezone%$ runtime
+Note that TZ is handled separately, by the &%timezone%& runtime
 option and by the TIMEZONE_DEFAULT buildtime option.
 .code
 # keep_environment = ^LDAP
@@ -5853,13 +6030,13 @@ messages that are submitted by SMTP from local processes using the standard
 input and output (that is, not using TCP/IP). A number of MUAs operate in this
 manner.
 .code
-deny    message       = Restricted characters in address
-        domains       = +local_domains
+deny    domains       = +local_domains
         local_parts   = ^[.] : ^.*[@%!/|]
+        message       = Restricted characters in address
 
-deny    message       = Restricted characters in address
-        domains       = !+local_domains
+deny    domains       = !+local_domains
         local_parts   = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
+        message       = Restricted characters in address
 .endd
 These statements are concerned with local parts that contain any of the
 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
@@ -5963,10 +6140,10 @@ require verify = recipient
 This statement requires the recipient address to be verified; if verification
 fails, the address is rejected.
 .code
-# deny    message     = rejected because $sender_host_address \
+# deny    dnslists    = black.list.example
+#         message     = rejected because $sender_host_address \
 #                       is in a black list at $dnslist_domain\n\
 #                       $dnslist_text
-#         dnslists    = black.list.example
 #
 # warn    dnslists    = black.list.example
 #         add_header  = X-Warning: $sender_host_address is in \
@@ -6253,10 +6430,6 @@ Two remote transports and four local transports are defined.
 remote_smtp:
   driver = smtp
   message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
-.ifdef _HAVE_DANE
-  dnssec_request_domains = *
-  hosts_try_dane = *
-.endif
 .ifdef _HAVE_PRDR
   hosts_try_prdr = *
 .endif
@@ -6264,9 +6437,7 @@ remote_smtp:
 This transport is used for delivering messages over SMTP connections.
 The list of remote hosts comes from the router.
 The &%message_size_limit%& usage is a hack to avoid sending on messages
-with over-long lines.  The built-in macro _HAVE_DANE guards configuration
-to try to use DNSSEC for all queries and to use DANE for delivery;
-see section &<<SECDANE>>& for more details.
+with over-long lines.
 
 The &%hosts_try_prdr%& option enables an efficiency SMTP option.  It is
 negotiated between client and server and not expected to cause problems
@@ -6288,9 +6459,9 @@ smarthost_smtp:
   # request with your smarthost provider to get things fixed:
   hosts_require_tls = *
   tls_verify_hosts = *
-  # As long as tls_verify_hosts is enabled, this won't matter, but if you
-  # have to comment it out then this will at least log whether you succeed
-  # or not:
+  # As long as tls_verify_hosts is enabled, this this will have no effect,
+  # but if you have to comment it out then this will at least log whether
+  # you succeed or not:
   tls_try_verify_hosts = *
   #
   # The SNI name should match the name which we'll expect to verify;
@@ -6335,7 +6506,7 @@ All other options are defaulted.
 .code
 local_delivery:
   driver = appendfile
-  file = /var/mail/$local_part
+  file = /var/mail/$local_part_data
   delivery_date_add
   envelope_to_add
   return_path_add
@@ -6343,7 +6514,15 @@ local_delivery:
 # mode = 0660
 .endd
 This &(appendfile)& transport is used for local delivery to user mailboxes in
-traditional BSD mailbox format. By default it runs under the uid and gid of the
+traditional BSD mailbox format.
+
+We prefer to avoid using &$local_part$& directly to define the mailbox filename,
+as it is provided by a potential bad actor.
+Instead we use &$local_part_data$&,
+the result of looking up &$local_part$& in the user database
+(done by using &%check_local_user%& in the the router).
+
+By default &(appendfile)& runs under the uid and gid of the
 local user, which requires the sticky bit to be set on the &_/var/mail_&
 directory. Some systems use the alternative approach of running mail deliveries
 under a particular group instead of using the sticky bit. The commented options
@@ -6475,9 +6654,9 @@ Chapter &<<CHAPplaintext>>& covers both.
 .chapter "Regular expressions" "CHAPregexp"
 
 .cindex "regular expressions" "library"
-.cindex "PCRE"
+.cindex "PCRE2"
 Exim supports the use of regular expressions in many of its options. It
-uses the PCRE regular expression library; this provides regular expression
+uses the PCRE2 regular expression library; this provides regular expression
 matching that is compatible with Perl 5. The syntax and semantics of
 regular expressions is discussed in
 online Perl manpages, in
@@ -6489,10 +6668,10 @@ O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
 . --- to the old URL for now.  2018-09-07.
 
 The documentation for the syntax and semantics of the regular expressions that
-are supported by PCRE is included in the PCRE distribution, and no further
-description is included here. The PCRE functions are called from Exim using
-the default option settings (that is, with no PCRE options set), except that
-the PCRE_CASELESS option is set when the matching is required to be
+are supported by PCRE2 is included in the PCRE2 distribution, and no further
+description is included here. The PCRE2 functions are called from Exim using
+the default option settings (that is, with no PCRE2 options set), except that
+the PCRE2_CASELESS option is set when the matching is required to be
 case-insensitive.
 
 In most cases, when a regular expression is required in an Exim configuration,
@@ -6548,14 +6727,15 @@ cause parts of the string to be replaced by data that is obtained from the
 lookup. Lookups of this type are conditional expansion items. Different results
 can be defined for the cases of lookup success and failure. See chapter
 &<<CHAPexpand>>&, where string expansions are described in detail.
-The key for the lookup is specified as part of the string expansion.
+The key for the lookup is &*specified*& as part of the string expansion.
 .next
 Lists of domains, hosts, and email addresses can contain lookup requests as a
 way of avoiding excessively long linear lists. In this case, the data that is
 returned by the lookup is often (but not always) discarded; whether the lookup
 succeeds or fails is what really counts. These kinds of list are described in
 chapter &<<CHAPdomhosaddlists>>&.
-The key for the lookup is given by the context in which the list is expanded.
+The key for the lookup is &*implicit*&,
+given by the context in which the list is expanded.
 .endlist
 
 String expansions, lists, and lookups interact with each other in such a way
@@ -6585,10 +6765,13 @@ file that is searched could contain lines like this:
 .endd
 When the lookup succeeds, the result of the expansion is a list of domains (and
 possibly other types of item that are allowed in domain lists).
+.cindex "tainted data" "de-tainting"
+The result of the expansion is not tainted.
 
 In the second example, the lookup is a single item in a domain list. It causes
 Exim to use a lookup to see if the domain that is being processed can be found
-in the file. The file could contains lines like this:
+in the file.
+The file could contains lines like this:
 .code
 domain1:
 domain2:
@@ -6605,6 +6788,16 @@ If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
 first &%domains%& setting above generates the second setting, which therefore
 causes a second lookup to occur.
 
+The lookup type may optionally be followed by a comma
+and a comma-separated list of options.
+Each option is a &"name=value"& pair.
+Whether an option is meaningful depends on the lookup type.
+
+All lookups support the option &"cache=no_rd"&.
+If this is given then the cache that Exim manages for lookup results
+is not checked before doing the lookup.
+The result of the lookup is still written to the cache.
+
 The rest of this chapter describes the different lookup types that are
 available. Any of them can be used in any part of the configuration where a
 lookup is permitted.
@@ -6619,6 +6812,16 @@ Two different types of data lookup are implemented:
 The &'single-key'& type requires the specification of a file in which to look,
 and a single key to search for. The key must be a non-empty string for the
 lookup to succeed. The lookup type determines how the file is searched.
+.cindex "tainted data" "single-key lookups"
+The file string may not be tainted.
+
+.cindex "tainted data" "de-tainting"
+All single-key lookups support the option &"ret=key"&.
+If this is given and the lookup
+(either underlying implementation or cached value)
+returns data, the result is replaced with a non-tainted
+version of the lookup key.
+.cindex "tainted data" "de-tainting"
 .next
 .cindex "query-style lookup" "definition of"
 The &'query-style'& type accepts a generalized database query. No particular
@@ -6657,11 +6860,10 @@ aliases or other indexed data referenced by an MTA. Information about cdb and
 tools for building the files can be found in several places:
 .display
 &url(https://cr.yp.to/cdb.html)
-&url(http://www.corpit.ru/mjt/tinycdb.html)
+&url(https://www.corpit.ru/mjt/tinycdb.html)
 &url(https://packages.debian.org/stable/utils/freecdb)
 &url(https://github.com/philpennock/cdbtools) (in Go)
 .endd
-. --- 2018-09-07: corpit.ru http:-only
 A cdb distribution is not needed in order to build Exim with cdb support,
 because the code for reading cdb files is included directly in Exim itself.
 However, no means of building or testing cdb files is provided with Exim, so
@@ -6711,11 +6913,38 @@ by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
 .next
 .cindex "lookup" "dsearch"
 .cindex "dsearch lookup type"
-&(dsearch)&: The given file must be a directory; 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. If &[lstat()]& succeeds, the result of
-the lookup is the name of the entry, which may be a file, directory,
-symbolic link, or any other kind of directory entry. An example of how this
+&(dsearch)&: 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.
+If &[lstat()]& succeeds then so does the lookup.
+.cindex "tainted data" "dsearch result"
+The result is regarded as untainted.
+
+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.
+
+Two 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:
+.code
+${lookup {passwd} dsearch,ret=full {/etc}}
+.endd
+The default result is just the requested entry.
+The "filter" option requests that only directory entries of a given type
+are matched. The match value is one of "file", "dir" or "subdir" (the latter
+not matching "." or ".."). Example:
+.code
+${lookup {passwd} dsearch,filter=file {/etc}}
+.endd
+The default matching is for any entry type, including directories
+and symlinks.
+
+An example of how this
 lookup can be used to support virtual domains is given in section
 &<<SECTvirtualdomains>>&.
 .next
@@ -6745,6 +6974,53 @@ 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>>&).
+
+&*Warning 3*&: Do not use an IPv4-mapped IPv6 address for a key; use the
+IPv4, in dotted-quad form. (Exim converts IPv4-mapped IPv6 addresses to this
+notation before executing the lookup.)
+
+One option is supported, "ret=full", to request the return of the entire line
+rather than omitting the key porttion.
+Note however that the key portion will have been de-quoted.
+
+.next
+.cindex lookup json
+.cindex json "lookup type"
+.cindex JSON expansions
+&(json)&: The given file is a text file with a JSON structure.
+An element of the structure is extracted, defined by the search key.
+The key is a list of subelement selectors
+(colon-separated by default but changeable in the usual way)
+which are applied in turn to select smaller and smaller portions
+of the JSON structure.
+If a selector is numeric, it must apply to a JSON array; the (zero-based)
+nunbered array element is selected.
+Otherwise it must apply to a JSON object; the named element is selected.
+The final resulting element can be a simple JSON type or a JSON object
+or array; for the latter two a string-representation of the JSON
+is returned.
+For elements of type string, the returned value is de-quoted.
+
+
+.next
+.cindex LMDB
+.cindex lookup lmdb
+.cindex database lmdb
+&(lmdb)&: 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/)
+for the feature set and operation modes.
+
+Exim provides read-only access via the LMDB C library.
+The library can be obtained from &url(https://github.com/LMDB/lmdb)
+or your operating system package repository.
+To enable LMDB support in Exim set LOOKUP_LMDB=yes in &_Local/Makefile_&.
+
+You will need to separately create the LMDB database file,
+possibly using the &"mdb_load"& utility.
+
+
 .next
 .cindex "linear search"
 .cindex "lookup" "lsearch"
@@ -6866,9 +7142,10 @@ be followed by optional colons.
 lookup types support only literal keys.
 
 .next
+.cindex "spf lookup type"
 .cindex "lookup" "spf"
-If Exim is built with SPF support, manual lookups can be done
-(as opposed to the standard ACL condition method.
+&(spf)&: If Exim is built with SPF support, manual lookups can be done
+(as opposed to the standard ACL condition method).
 For details see section &<<SECSPF>>&.
 .endlist ilist
 
@@ -6939,8 +7216,8 @@ passed to a Redis database. See section &<<SECTsql>>&.
 .next
 .cindex "sqlite lookup type"
 .cindex "lookup" "sqlite"
-&(sqlite)&: The format of the query is a filename followed by an SQL statement
-that is passed to an SQLite database. See section &<<SECTsqlite>>&.
+&(sqlite)&: The format of the query is
+an SQL statement that is passed to an SQLite database. See section &<<SECTsqlite>>&.
 
 .next
 &(testdb)&: This is a lookup type that is used for testing Exim. It is
@@ -7143,6 +7420,10 @@ lookups. However, because (apart from the daemon) Exim operates as a collection
 of independent, short-lived processes, this caching applies only within a
 single Exim process. There is no inter-process lookup caching facility.
 
+If an option &"cache=no_rd"& is used on the lookup then
+the cache is only written to, cached data is not used for the operation
+and a real lookup is done.
+
 For single-key lookups, Exim keeps the relevant files open in case there is
 another lookup that needs them. In some types of configuration this can lead to
 many files being kept open for messages with many recipients. To avoid hitting
@@ -7298,7 +7579,7 @@ with the lookup.
 With &"strict"& a response from the DNS resolver that
 is not labelled as authenticated data
 is treated as equivalent to a temporary DNS error.
-The default is &"never"&.
+The default is &"lax"&.
 
 See also the &$lookup_dnssec_authenticated$& variable.
 
@@ -7846,6 +8127,11 @@ If any MySQL, PostgreSQL, Oracle, InterBase or Redis lookups are used, the
 or &%redis_servers%&
 option (as appropriate) must be set to a colon-separated list of server
 information.
+.oindex &%mysql_servers%&
+.oindex &%pgsql_servers%&
+.oindex &%oracle_servers%&
+.oindex &%ibase_servers%&
+.oindex &%redis_servers%&
 (For MySQL and PostgreSQL, the global option need not be set if all
 queries contain their own server information &-- see section
 &<<SECTspeserque>>&.)
@@ -7898,9 +8184,9 @@ escapes whitespace and backslash characters with a backslash.
 .section "Specifying the server in the query" "SECTspeserque"
 For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
 it is possible to specify a list of servers with an individual query. This is
-done by starting the query with
+done by appending a comma-separated option to the query type:
 .display
-&`servers=`&&'server1:server2:server3:...'&&`;`&
+&`,servers=`&&'server1:server2:server3:...'&
 .endd
 Each item in the list may take one of two forms:
 .olist
@@ -7926,15 +8212,24 @@ mysql_servers = slave1/db/name/pw:\
 .endd
 In an updating lookup, you could then write:
 .code
-${lookup mysql{servers=master; UPDATE ...} }
+${lookup mysql,servers=master {UPDATE ...} }
 .endd
 That query would then be sent only to the master server. If, on the other hand,
 the master is not to be used for reading, and so is not present in the global
 option, you can still update it by a query of this form:
 .code
-${lookup pgsql{servers=master/db/name/pw; UPDATE ...} }
+${lookup pgsql,servers=master/db/name/pw {UPDATE ...} }
 .endd
 
+An older syntax places the servers specification before the query,
+semicolon separated:
+.code
+${lookup mysql{servers=master; UPDATE ...} }
+.endd
+The new version avoids potential issues with tainted
+arguments in the query, for explicit expansion.
+&*Note*&: server specifications in list-style lookups are still problematic.
+
 
 .section "Special MySQL features" "SECID73"
 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
@@ -7983,17 +8278,37 @@ affected.
 .cindex "sqlite lookup type"
 SQLite is different to the other SQL lookups because a filename is required in
 addition to the SQL query. An SQLite database is a single file, and there is no
-daemon as in the other SQL databases. The interface to Exim requires the name
-of the file, as an absolute path, to be given at the start of the query. It is
-separated from the query by white space. This means that the path name cannot
-contain white space. Here is a lookup expansion example:
-.code
-${lookup sqlite {/some/thing/sqlitedb \
-  select name from aliases where id='userx';}}
+daemon as in the other SQL databases.
+
+.oindex &%sqlite_dbfile%&
+There are two ways of
+specifying the file.
+The first is is by using the &%sqlite_dbfile%& main option.
+The second, which allows separate files for each query,
+is to use an option appended, comma-separated, to the &"sqlite"&
+lookup type word.  The option is the word &"file"&, then an equals,
+then the filename.
+The filename in this case cannot contain whitespace or open-brace charachters.
+
+A deprecated method is available, prefixing the query with the filename
+separated by white space.
+This means that
+.cindex "tainted data" "sqlite file"
+the query cannot use any tainted values, as that taints
+the entire query including the filename - resulting in a refusal to open
+the file.
+
+In all the above cases the filename must be an absolute path.
+
+Here is a lookup expansion example:
+.code
+sqlite_dbfile = /some/thing/sqlitedb
+...
+${lookup sqlite {select name from aliases where id='userx';}}
 .endd
 In a list, the syntax is similar. For example:
 .code
-domainlist relay_to_domains = sqlite;/some/thing/sqlitedb \
+domainlist relay_to_domains = sqlite;\
    select * from relays where ip='$sender_host_address';
 .endd
 The only character affected by the &%quote_sqlite%& operator is a single
@@ -8185,6 +8500,34 @@ in the previous section. You could also use the &(wildlsearch)& or
 
 
 
+.section "Results of list checking" SECTlistresults
+The primary result of doing a list check is a truth value.
+In some contexts additional information is stored
+about the list element that matched:
+.vlist
+.vitem hosts
+A &%hosts%& ACL condition
+will store a result in the &$host_data$& variable.
+.vitem local_parts
+A &%local_parts%& router option or &%local_parts%& ACL condition
+will store a result in the &$local_part_data$& variable.
+.vitem domains
+A &%domains%& router option or &%domains%& ACL condition
+will store a result in the &$domain_data$& variable.
+.vitem senders
+A &%senders%& router option or &%senders%& ACL condition
+will store a result in the &$sender_data$& variable.
+.vitem recipients
+A &%recipients%& ACL condition
+will store a result in the &$recipient_data$& variable.
+.endlist
+
+The detail of the additional information depends on the
+type of match and is given below as the &*value*& information.
+
+
+
+
 .section "Named lists" "SECTnamedlists"
 .cindex "named lists"
 .cindex "list" "named"
@@ -8243,6 +8586,17 @@ domainlist  dom2 = !a.b : *.b
 where &'x.y'& does not match. It's best to avoid negation altogether in
 referenced lists if you can.
 
+.cindex "hiding named list values"
+.cindex "named lists" "hiding value of"
+Some named list definitions may contain sensitive data, for example, passwords for
+accessing databases. To stop non-admin users from using the &%-bP%& command
+line option to read these values, you can precede the definition with the
+word &"hide"&. For example:
+.code
+hide domainlist filter_for_domains = ldap;PASS=secret ldap::/// ...
+.endd
+
+
 Named lists may have a performance advantage. When Exim is routing an
 address or checking an incoming message, it caches the result of tests on named
 lists. So, if you have a setting such as
@@ -8334,6 +8688,10 @@ If a pattern consists of a single @ character, it matches the local host name,
 as set by the &%primary_hostname%& option (or defaulted). This makes it
 possible to use the same configuration file on several different hosts that
 differ only in their names.
+
+The value for a match will be the primary host name.
+
+
 .next
 .cindex "@[] in a domain list"
 .cindex "domain list" "matching local IP interfaces"
@@ -8343,7 +8701,12 @@ in square brackets (as in an email address that contains a domain literal), but
 only if that IP address is recognized as local for email routing purposes. The
 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
 control which of a host's several IP addresses are treated as local.
-In today's Internet, the use of domain literals is controversial.
+In today's Internet, the use of domain literals is controversial;
+see the &%allow_domain_literals%& main option.
+
+The value for a match will be the string &`@[]`&.
+
+
 .next
 .cindex "@mx_any"
 .cindex "@mx_primary"
@@ -8392,6 +8755,9 @@ involved, it is easiest to change the delimiter for the main list as well:
 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
           an.other.domain ? ...
 .endd
+The value for a match will be the list element string (starting &`@mx_`&).
+
+
 .next
 .cindex "asterisk" "in domain list"
 .cindex "domain list" "asterisk in"
@@ -8404,6 +8770,10 @@ matching works only in terms of dot-separated components. For example, a domain
 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
 &'cipher.key.ex'&.
 
+The value for a match will be the list element string (starting with the asterisk).
+Additionally, &$0$& will be set to the matched string
+and &$1$& to the variable portion which the asterisk matched.
+
 .next
 .cindex "regular expressions" "in domain list"
 .cindex "domain list" "matching regular expression"
@@ -8420,6 +8790,13 @@ must escape any backslash and dollar characters in the regular expression, or
 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
 it is not to be expanded (unless you really do want to build a regular
 expression by expansion, of course).
+
+The value for a match will be the list element string (starting with the circumflex).
+Additionally, &$0$& will be set to the string matching the regular expression,
+and &$1$& (onwards) to any submatches identified by parentheses.
+
+
+
 .next
 .cindex "lookup" "in domain list"
 .cindex "domain list" "matching by lookup"
@@ -8431,12 +8808,20 @@ must be a filename in a suitable format for the lookup type. For example, for
 domains = cdb;/etc/mail/local_domains.cdb
 .endd
 The appropriate type of lookup is done on the file using the domain name as the
-key. In most cases, the data that is looked up is not used; Exim is interested
+key. In most cases, the value resulting from the lookup is not used; Exim is interested
 only in whether or not the key is present in the file. However, when a lookup
 is used for the &%domains%& option on a router
-or a &%domains%& condition in an ACL statement, the data is preserved in the
+or a &%domains%& condition in an ACL statement, the value is preserved in the
 &$domain_data$& variable and can be referred to in other router options or
 other statements in the same ACL.
+.cindex "tainted data" "de-tainting"
+The value will be untainted.
+
+&*Note*&: If the data result of the lookup (as opposed to the key)
+is empty, then this empty value is stored in &$domain_data$&.
+The option to return the key for the lookup, as the value,
+may be what is wanted.
+
 
 .next
 Any of the single-key lookup type names may be preceded by
@@ -8455,6 +8840,7 @@ original lookup fails. This is not a useful feature when using a domain list to
 select particular domains (because any domain would match), but it might have
 value if the result of the lookup is being used via the &$domain_data$&
 expansion variable.
+
 .next
 If the pattern starts with the name of a query-style lookup type followed by a
 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
@@ -8464,17 +8850,40 @@ chapter &<<CHAPfdlookup>>&. For example:
 hold_domains = mysql;select domain from holdlist \
   where domain = '${quote_mysql:$domain}';
 .endd
-In most cases, the data that is looked up is not used (so for an SQL query, for
+In most cases, the value resulting from the lookup is not used (so for an SQL query, for
 example, it doesn't matter what field you select). Exim is interested only in
 whether or not the query succeeds. However, when a lookup is used for the
-&%domains%& option on a router, the data is preserved in the &$domain_data$&
+&%domains%& option on a router, the value is preserved in the &$domain_data$&
 variable and can be referred to in other options.
+.cindex "tainted data" "de-tainting"
+The value will be untainted.
+
+.next
+If the pattern starts with the name of a lookup type
+of either kind (single-key or query-style) it may be
+followed by a comma and options,
+The options are lookup-type specific and consist of a comma-separated list.
+Each item starts with a tag and and equals "=" sign.
+
 .next
 .cindex "domain list" "matching literal domain name"
 If none of the above cases apply, a caseless textual comparison is made
 between the pattern and the domain.
+
+The value for a match will be the list element string.
+.cindex "tainted data" "de-tainting"
+Note that this is commonly untainted
+(depending on the way the list was created).
+Specifically, explicit text in the configuration file in not tainted.
+This is a useful way of obtaining an untainted equivalent to
+the domain, for later operations.
+
+However if the list (including one-element lists)
+is created by expanding a variable containing tainted data,
+it is tainted and so will the match value be.
 .endlist
 
+
 Here is an example that uses several different kinds of pattern:
 .code
 domainlist funny_domains = \
@@ -8573,9 +8982,13 @@ accept hosts = @[]
 .endd
 .next
 .cindex "CIDR notation"
-If the pattern is an IP address followed by a slash and a mask length (for
-example 10.11.42.0/24), it is matched against the IP address of the subject
-host under the given mask. This allows, an entire network of hosts to be
+If the pattern is an IP address followed by a slash and a mask length, for
+example
+.code
+10.11.42.0/24
+.endd
+, it is matched against the IP address of the subject
+host under the given mask. This allows an entire network of hosts to be
 included (or excluded) by a single item. The mask uses CIDR notation; it
 specifies the number of address bits that must match, starting from the most
 significant end of the address.
@@ -8663,8 +9076,10 @@ to quote keys was made available in &(lsearch)& files. However, the more
 recently implemented &(iplsearch)& files do require colons in IPv6 keys
 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
-converted using colons and not dots. In all cases, full, unabbreviated IPv6
+converted using colons and not dots.
+In all cases except IPv4-mapped IPv6, full, unabbreviated IPv6
 addresses are always used.
+The latter are converted to IPv4 addresses, in dotted-quad form.
 
 Ideally, it would be nice to tidy up this anomalous situation by changing to
 colons in all cases, given that quoting is now available for &(lsearch)&.
@@ -9142,6 +9557,9 @@ become case-sensitive after &"+caseful"& has been seen.
 .section "Local part lists" "SECTlocparlis"
 .cindex "list" "local part list"
 .cindex "local part" "list"
+These behave in the same way as domain and host lists, with the following
+changes:
+
 Case-sensitivity in local part lists is handled in the same way as for address
 lists, as just described. The &"+caseful"& item can be used if required. In a
 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
@@ -9173,6 +9591,7 @@ Many strings in Exim's runtime configuration are expanded before use. Some of
 them are expanded every time they are used; others are expanded only once.
 
 When a string is being expanded it is copied verbatim from left to right except
+.cindex expansion "string concatenation"
 when a dollar or backslash character is encountered. A dollar specifies the
 start of a portion of the string that is interpreted and replaced as described
 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
@@ -9183,7 +9602,23 @@ dependent upon the option for which a value is sought; in this documentation,
 options for which string expansion is performed are marked with &dagger; after
 the data type.  ACL rules always expand strings.  A couple of expansion
 conditions do not expand some of the brace-delimited branches, for security
-reasons.
+reasons,
+.cindex "tainted data" expansion
+.cindex "tainted data" definition
+.cindex expansion "tainted data"
+and expansion of data deriving from the sender (&"tainted data"&)
+is not permitted (including acessing a file using a tainted name).
+The main config option &%allow_insecure_tainted_data%& can be used as
+mitigation during uprades to more secure configurations.
+
+Common ways of obtaining untainted equivalents of variables with
+tainted values
+.cindex "tainted data" "de-tainting"
+come down to using the tainted value as a lookup key in a trusted database.
+This database could be the filesystem structure,
+or the password file,
+or accessed via a DBMS.
+Specific methods are indexed under &"de-tainting"&.
 
 
 
@@ -9330,10 +9765,10 @@ If the ACL returns defer the result is a forced-fail.  Otherwise the expansion f
 
 .vitem "&*${authresults{*&<&'authserv-id'&>&*}}*&"
 .cindex authentication "results header"
-.cindex headers "authentication-results:"
+.chindex Authentication-Results:
 .cindex authentication "expansion item"
 This item returns a string suitable for insertion as an
-&'Authentication-Results"'&
+&'Authentication-Results:'&
 header line.
 The given <&'authserv-id'&> is included in the result; typically this
 will be a domain name identifying the system performing the authentications.
@@ -9430,9 +9865,13 @@ set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
 object so that it doesn't reload the same object file in the same Exim process
 (but of course Exim does start new processes frequently).
 
-There may be from zero to eight arguments to the function. When compiling
-a local function that is to be called in this way, &_local_scan.h_& should be
-included. The Exim variables and functions that are defined by that API
+There may be from zero to eight arguments to the function.
+
+When compiling
+a local function that is to be called in this way,
+first &_DLFUNC_IMPL_& should be defined,
+and second &_local_scan.h_& should be included.
+The Exim variables and functions that are defined by that API
 are also available for dynamically loaded functions. The function itself
 must have the following type:
 .code
@@ -9521,8 +9960,9 @@ ${extract{Z}{A=... B=...}{$value} fail }
 This forces an expansion failure (see section &<<SECTforexpfai>>&);
 {<&'string2'&>} must be present for &"fail"& to be recognized.
 
-.new
 .vitem "&*${extract json{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
+       {*&<&'string3'&>&*}}*&" &&&
+       "&*${extract jsons{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
        {*&<&'string3'&>&*}}*&"
 .cindex "expansion" "extracting from JSON object"
 .cindex JSON expansions
@@ -9537,10 +9977,14 @@ The expanded <&'string1'&> must be of the form:
 The braces, commas and colons, and the quoting of the member name are required;
 the spaces are optional.
 Matching of the key against the member names is done case-sensitively.
+For the &"json"& variant,
+if a returned value is a JSON string, it retains its leading and
+trailing quotes.
+For the &"jsons"& variant, which is intended for use with JSON strings, the
+leading and trailing quotes are removed from the returned value.
 . XXX should be a UTF-8 compare
 
 The results of matching are handled as above.
-.wen
 
 
 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
@@ -9574,8 +10018,9 @@ yields &"99"&. Two successive separators mean that the field between them is
 empty (for example, the fifth field above).
 
 
-.new
-.vitem "&*${extract json{*&<&'number'&>&*}}&&&
+.vitem "&*${extract json {*&<&'number'&>&*}}&&&
+        {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&" &&&
+       "&*${extract jsons{*&<&'number'&>&*}}&&&
         {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
 .cindex "expansion" "extracting from JSON array"
 .cindex JSON expansions
@@ -9584,7 +10029,11 @@ apart from leading and trailing white space, which is ignored.
 
 Field selection and result handling is as above;
 there is no choice of field separator.
-.wen
+For the &"json"& variant,
+if a returned value is a JSON string, it retains its leading and
+trailing quotes.
+For the &"jsons"& variant, which is intended for use with JSON strings, the
+leading and trailing quotes are removed from the returned value.
 
 
 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
@@ -9603,7 +10052,7 @@ input, but a separator setting is not included in the output. For example:
 ${filter{a:b:c}{!eq{$item}{b}}}
 .endd
 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
-to what it was before. See also the &*map*& and &*reduce*& expansion items.
+to what it was before. See also the &%map%& and &%reduce%& expansion items.
 
 
 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
@@ -9641,7 +10090,7 @@ letters appear. For example:
        "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
         &*$bh_*&<&'header&~name'&>&*:*&" &&&
        "&*$lheader_*&<&'header&~name'&>&*:*&&~or&~&&&
-        &*$lh_*&<&'header&~name'&>&*:*&"
+        &*$lh_*&<&'header&~name'&>&*:*&" &&&
        "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
         &*$rh_*&<&'header&~name'&>&*:*&"
 .cindex "expansion" "header insertion"
@@ -9726,7 +10175,7 @@ They are visible in DKIM, PRDR and DATA ACLs.
 Header lines that are added in a RCPT ACL (for example)
 are saved until the message's incoming header lines are available, at which
 point they are added.
-When any of the above ACLs ar
+When any of the above ACLs are
 running, however, header lines added by earlier ACLs are visible.
 
 Upper case and lower case letters are synonymous in header names. If the
@@ -9747,6 +10196,10 @@ newline at the very end. For the &%header%& and &%bheader%& expansion, for
 those headers that contain lists of addresses, a comma is also inserted at the
 junctions between headers. This does not happen for the &%rheader%& expansion.
 
+.cindex "tainted data" "message headers"
+When the headers are from an incoming message,
+the result of expanding any of these variables is tainted.
+
 
 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
 .cindex "expansion" "hmac hashing"
@@ -9878,12 +10331,19 @@ extracted is used.
 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
 
 
-.vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
-        {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
-This is the first of one of two different types of lookup item, which are both
-described in the next item.
+.vitem &*${listquote{*&<&'separator'&>&*}{*&<&'string'&>&*}}*&
+.cindex quoting "for list"
+.cindex list quoting
+This item doubles any occurrence of the separator character
+in the given string.
+An empty string is replaced with a single space.
+This converts the string into a safe form for use as a list element,
+in a list using the given separator.
 
-.vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
+
+.vitem "&*${lookup&~{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
+        {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&" &&&
+       "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
         {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
 .cindex "expansion" "lookup in"
 .cindex "file" "lookups"
@@ -9954,8 +10414,8 @@ setting is not included in the output. For example:
 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
 .endd
 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
-value of &$item$& is restored to what it was before. See also the &*filter*&
-and &*reduce*& expansion items.
+value of &$item$& is restored to what it was before. See also the &%filter%&
+and &%reduce%& expansion items.
 
 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
 .cindex "expansion" "numeric hash"
@@ -9989,10 +10449,11 @@ additional arguments need be given; the maximum number permitted, including the
 name of the subroutine, is nine.
 
 The return value of the subroutine is inserted into the expanded string, unless
-the return value is &%undef%&. In that case, the expansion fails in the same
-way as an explicit &"fail"& on a lookup item. The return value is a scalar.
-Whatever you return is evaluated in a scalar context. For example, if you
-return the name of a Perl vector, the return value is the size of the vector,
+the return value is &%undef%&. In that case, the entire expansion is
+forced to fail, in the same way as an explicit &"fail"& on a lookup item
+does (see section &<<SECTforexpfai>>&).  Whatever you return is evaluated
+in a scalar context, thus the return value is a scalar.  For example, if you
+return a Perl vector, the return value is the size of the vector,
 not its contents.
 
 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
@@ -10042,7 +10503,7 @@ For more discussion and an example, see section &<<SECTverifyPRVS>>&.
 .cindex "expansion" "inserting an entire file"
 .cindex "file" "inserting into expansion"
 .cindex "&%readfile%& expansion item"
-The filename and end-of-line string are first expanded separately. The file is
+The filename and end-of-line (eol) string are first expanded separately. The file is
 then read, and its contents replace the entire item. All newline characters in
 the file are replaced by the end-of-line string if it is present. Otherwise,
 newlines are left in the string.
@@ -10079,7 +10540,7 @@ ${readsocket{inet:[::1]:1234}{request string}}
 Only a single host name may be given, but if looking it up yields more than
 one IP address, they are each tried in turn until a connection is made. For
 both kinds of socket, Exim makes a connection, writes the request string
-unless it is an empty string; and no terminating NUL is ever sent)
+(unless it is an empty string; no terminating NUL is ever sent)
 and reads from the socket until an end-of-file
 is read. A timeout of 5 seconds is applied. Additional, optional arguments
 extend what can be done. Firstly, you can vary the timeout. For example:
@@ -10088,23 +10549,35 @@ ${readsocket{/socket/name}{request string}{3s}}
 .endd
 
 The third argument is a list of options, of which the first element is the timeout
-and must be present if the argument is given.
+and must be present if any options are given.
 Further elements are options of form &'name=value'&.
-Two option types is currently recognised: shutdown and tls.
-The first defines whether (the default)
-or not a shutdown is done on the connection after sending the request.
-Example, to not do so (preferred, eg. by some webservers):
+Example:
 .code
 ${readsocket{/socket/name}{request string}{3s:shutdown=no}}
 .endd
-.new
-The second, tls, controls the use of TLS on the connection.  Example:
-.code
-${readsocket{/socket/name}{request string}{3s:tls=yes}}
-.endd
-The default is to not use TLS.
-If it is enabled, a shutdown as descripbed above is never done.
-.wen
+
+The following option names are recognised:
+.ilist
+&*cache*&
+Defines if the result data can be cached for use by a later identical
+request in the same process.
+Values are &"yes"& or &"no"& (the default).
+If not, all cached results for this connection specification
+will be invalidated.
+
+.next
+&*shutdown*&
+Defines whether or not a write-shutdown is done on the connection after
+sending the request. Values are &"yes"& (the default) or &"no"&
+(preferred, eg. by some webservers).
+
+.next
+&*tls*&
+Controls the use of TLS on the connection.
+Values are &"yes"& or &"no"& (the default).
+If it is enabled, a shutdown as described above is never done.
+.endlist
+
 
 A fourth argument allows you to change any newlines that are in the data
 that is read, in the same way as for &%readfile%& (see above). This example
@@ -10156,7 +10629,7 @@ assigned to the &$value$& variable. After this, each item in the <&'string1'&>
 list is assigned to &$item$&, in turn, and <&'string3'&> is expanded for each of
 them. The result of that expansion is assigned to &$value$& before the next
 iteration. When the end of the list is reached, the final value of &$value$& is
-added to the expansion output. The &*reduce*& expansion item can be used in a
+added to the expansion output. The &%reduce%& expansion item can be used in a
 number of ways. For example, to add up a list of numbers:
 .code
 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
@@ -10167,7 +10640,7 @@ can be found:
 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
 .endd
 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
-restored to what they were before. See also the &*filter*& and &*map*&
+restored to what they were before. See also the &%filter%& and &%map%&
 expansion items.
 
 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
@@ -10305,6 +10778,12 @@ ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
 will sort an MX lookup into priority order.
 
 
+
+.vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
+SRS encoding.  See SECT &<<SECTSRS>>& for details.
+
+
+
 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
 .cindex "&%substr%& expansion item"
 .cindex "substring extraction"
@@ -10427,9 +10906,9 @@ separator explicitly:
 ${addresses:>:$h_from:}
 .endd
 
-Compare the &*address*& (singular)
+Compare the &%address%& (singular)
 expansion item, which extracts the working address from a single RFC2822
-address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
+address. See the &%filter%&, &%map%&, and &%reduce%& items for ways of
 processing lists.
 
 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
@@ -10525,7 +11004,7 @@ is controlled by the &%print_topbitchars%& option.
 .vitem &*${escape8bit:*&<&'string'&>&*}*&
 .cindex "expansion" "escaping 8-bit characters"
 .cindex "&%escape8bit%& expansion item"
-If the string contains and characters with the most significant bit set,
+If the string contains any characters with the most significant bit set,
 they are converted to escape sequences starting with a backslash.
 Backslashes and DEL characters are also converted.
 
@@ -10579,8 +11058,7 @@ a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For exam
 
 As a more realistic example, in an ACL you might have
 .code
-deny   message = Too many bad recipients
-       condition =                    \
+deny   condition =                    \
          ${if and {                   \
            {>{$rcpt_count}{10}}       \
            {                          \
@@ -10589,6 +11067,7 @@ deny   message = Too many bad recipients
              {${eval:$rcpt_count/2}}  \
            }                          \
          }{yes}{no}}
+       message = Too many bad recipients
 .endd
 The condition is true if there have been more than 10 RCPT commands and
 fewer than half of them have resulted in a valid recipient.
@@ -10721,6 +11200,8 @@ If the optional type is given it must be one of "a", "d", "h" or "l"
 and selects address-, domain-, host- or localpart- lists to search among respectively.
 Otherwise all types are searched in an undefined order and the first
 matching list is returned.
+&*Note*&: Neither string-expansion of lists referenced by named-list syntax elements,
+nor expansion of lookup elements, is done by the &%listnamed%& operator.
 
 
 .vitem &*${local_part:*&<&'string'&>&*}*&
@@ -10732,7 +11213,8 @@ empty.
 The parsing correctly handles SMTPUTF8 Unicode in the string.
 
 
-.vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
+.vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*& &&&
+       &*${mask_n:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
 .cindex "masked IP address"
 .cindex "IP address" "masking"
 .cindex "CIDR notation"
@@ -10746,8 +11228,14 @@ the result back to text, with mask appended. For example,
 .code
 ${mask:10.111.131.206/28}
 .endd
-returns the string &"10.111.131.192/28"&. Since this operation is expected to
-be mostly used for looking up masked addresses in files, the result for an IPv6
+returns the string &"10.111.131.192/28"&.
+
+Since this operation is expected to
+be mostly used for looking up masked addresses in files, the
+.new
+normal
+.wen
+result for an IPv6
 address uses dots to separate components instead of colons, because colon
 terminates a key string in lsearch files. So, for example,
 .code
@@ -10757,6 +11245,10 @@ returns the string
 .code
 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
 .endd
+.new
+If the optional form &*mask_n*& is used, IPv6 address result are instead
+returned in normailsed form, using colons and with zero-compression.
+.wen
 Letters in IPv6 addresses are always output in lower case.
 
 
@@ -10917,11 +11409,15 @@ If the string is a single variable of type certificate,
 returns the SHA-1 hash fingerprint of the certificate.
 
 
-.vitem &*${sha256:*&<&'string'&>&*}*&
+.vitem &*${sha256:*&<&'string'&>&*}*& &&&
+       &*${sha2:*&<&'string'&>&*}*& &&&
+       &*${sha2_<n>:*&<&'string'&>&*}*&
 .cindex "SHA-256 hash"
+.cindex "SHA-2 hash"
 .cindex certificate fingerprint
 .cindex "expansion" "SHA-256 hashing"
 .cindex "&%sha256%& expansion item"
+.cindex "&%sha2%& expansion item"
 The &%sha256%& operator computes the SHA-256 hash value of the string
 and returns
 it as a 64-digit hexadecimal number, in which any letters are in upper case.
@@ -10929,6 +11425,13 @@ it as a 64-digit hexadecimal number, in which any letters are in upper case.
 If the string is a single variable of type certificate,
 returns the SHA-256 hash fingerprint of the certificate.
 
+The operator can also be spelled &%sha2%& and does the same as &%sha256%&
+(except for certificates, which are not supported).
+Finally, if an underbar
+and a number is appended it specifies the output length, selecting a
+member of the SHA-2 family of hash functions.
+Values of 256, 384 and 512 are accepted, with 256 being the default.
+
 
 .vitem &*${sha3:*&<&'string'&>&*}*& &&&
        &*${sha3_<n>:*&<&'string'&>&*}*&
@@ -10977,7 +11480,7 @@ Now deprecated, a synonym for the &%base64%& expansion operator.
 .cindex "expansion" "string length"
 .cindex "string" "length in expansion"
 .cindex "&%strlen%& expansion item"
-The item is replace by the length of the expanded string, expressed as a
+The item is replaced by the length of the expanded string, expressed as a
 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
 All measurement is done in bytes and is not UTF-8 aware.
 
@@ -11026,7 +11529,6 @@ Case is defined per the system C locale.
 .cindex "expansion" "utf-8 forcing"
 .cindex "&%utf8clean%& expansion item"
 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
-.new
 In versions of Exim before 4.92, this did not correctly do so for a truncated
 final codepoint's encoding, and the character would be silently dropped.
 If you must handle detection of this scenario across both sets of Exim behavior,
@@ -11039,7 +11541,6 @@ condition = ${if inlist{${utf8clean:${length_1:$local_part}}}{:?}{yes}{no}}
 .endd
 (which will false-positive if the first character of the local part is a
 literal question mark).
-.wen
 
 .vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
        "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
@@ -11274,6 +11775,10 @@ condition is true if the named file (or directory) exists. The existence test
 is done by calling the &[stat()]& function. The use of the &%exists%& test in
 users' filter files may be locked out by the system administrator.
 
+&*Note:*& Testing a path using this condition is not a sufficient way of
+de-tainting it.
+Consider using a dsearch lookup.
+
 .vitem &*first_delivery*&
 .cindex "delivery" "first"
 .cindex "first delivery"
@@ -11311,11 +11816,28 @@ list separator is changed to a comma:
 .code
 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
 .endd
-The value of &$item$& is saved and restored while &*forany*& or &*forall*& is
+The value of &$item$& is saved and restored while &%forany%& or &%forall%& is
 being processed, to enable these expansion items to be nested.
 
 To scan a named list, expand it with the &*listnamed*& operator.
 
+.vitem "&*forall_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
+       "&*forany_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
+       "&*forall_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
+       "&*forany_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&"
+.cindex JSON "iterative conditions"
+.cindex JSON expansions
+.cindex expansion "&*forall_json*& condition"
+.cindex expansion "&*forany_json*& condition"
+.cindex expansion "&*forall_jsons*& condition"
+.cindex expansion "&*forany_jsons*& condition"
+As for the above, except that the first argument must, after expansion,
+be a JSON array.
+The array separator is not changeable.
+For the &"jsons"& variants the elements are expected to be JSON strings
+and have their quotes removed before the evaluation of the condition.
+
+
 
 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
        &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
@@ -11341,6 +11863,11 @@ includes the case of letters, whereas for &%gti%& the comparison is
 case-independent.
 Case and collation order are defined per the system C locale.
 
+
+.vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
+SRS decode.  See SECT &<<SECTSRS>>& for details.
+
+
 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
        &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
 .cindex "string" "comparison"
@@ -11571,8 +12098,9 @@ matched using &%match_ip%&.
 .cindex "&%pam%& expansion condition"
 &'Pluggable Authentication Modules'&
 (&url(https://mirrors.edge.kernel.org/pub/linux/libs/pam/)) are a facility that is
-available in the latest releases of Solaris and in some GNU/Linux
-distributions. The Exim support, which is intended for use in conjunction with
+available in Solaris
+and in some GNU/Linux distributions.
+The Exim support, which is intended for use in conjunction with
 the SMTP AUTH command, is available only if Exim is compiled with
 .code
 SUPPORT_PAM=yes
@@ -11590,15 +12118,12 @@ request, for a password, so the data consists of just two strings.
 
 There can be problems if any of the strings are permitted to contain colon
 characters. In the usual way, these have to be doubled to avoid being taken as
-separators. If the data is being inserted from a variable, the &%sg%& expansion
-item can be used to double any existing colons. For example, the configuration
+separators.
+The &%listquote%& expansion item can be used for this.
+For example, the configuration
 of a LOGIN authenticator might contain this setting:
 .code
-server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
-.endd
-For a PLAIN authenticator you could use:
-.code
-server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
+server_condition = ${if pam{$auth1:${listquote{:}{$auth2}}}}
 .endd
 In some operating systems, PAM authentication can be done only from a process
 running as root. Since Exim is running as the Exim user when receiving
@@ -11800,8 +12325,8 @@ this variable has the number of arguments.
 .vitem &$acl_verify_message$&
 .vindex "&$acl_verify_message$&"
 After an address verification has failed, this variable contains the failure
-message. It retains its value for use in subsequent modifiers. The message can
-be preserved by coding like this:
+message. It retains its value for use in subsequent modifiers of the verb.
+The message can be preserved by coding like this:
 .code
 warn !verify = sender
      set acl_m0 = $acl_verify_message
@@ -11809,6 +12334,7 @@ warn !verify = sender
 You can use &$acl_verify_message$& during the expansion of the &%message%& or
 &%log_message%& modifiers, to include information about the verification
 failure.
+&*Note*&: The variable is cleared at the end of processing the ACL verb.
 
 .vitem &$address_data$&
 .vindex "&$address_data$&"
@@ -11856,7 +12382,7 @@ to the relevant file.
 When, as a result of aliasing or forwarding, a message is directed to a pipe,
 this variable holds the pipe command when the transport is running.
 
-.vitem "&$auth1$& &-- &$auth3$&"
+.vitem "&$auth1$& &-- &$auth4$&"
 .vindex "&$auth1$&, &$auth2$&, etc"
 These variables are used in SMTP authenticators (see chapters
 &<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
@@ -12025,6 +12551,13 @@ When a message has been received this variable contains
 a colon-separated list of signer domains and identities for the message.
 For details see section &<<SECDKIMVFY>>&.
 
+.vitem &$dmarc_domain_policy$& &&&
+       &$dmarc_status$& &&&
+       &$dmarc_status_text$& &&&
+       &$dmarc_used_domains$&
+Results of DMARC verification.
+For details see section &<<SECDMARC>>&.
+
 .vitem &$dnslist_domain$& &&&
        &$dnslist_matched$& &&&
        &$dnslist_text$& &&&
@@ -12093,20 +12626,32 @@ When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
 .endlist
 
+.cindex "tainted data"
+If the origin of the data is an incoming message,
+the result of expanding this variable is tainted and may not
+be further expanded or used as a filename.
+When an untainted version is needed, one should be obtained from
+looking up the value in a local (therefore trusted) database.
+Often &$domain_data$& is usable in this role.
+
 
 .vitem &$domain_data$&
 .vindex "&$domain_data$&"
-When the &%domains%& option on a router matches a domain by
-means of a lookup, the data read by the lookup is available during the running
-of the router as &$domain_data$&. In addition, if the driver routes the
+When the &%domains%& condition on a router
+or an ACL
+matches a domain
+against a list, the match value is copied to &$domain_data$&.
+This is an enhancement over previous versions of Exim, when it only
+applied to the data read by a lookup.
+For details on match values see section &<<SECTlistresults>>& et. al.
+
+If the router routes the
 address to a transport, the value is available in that transport. If the
 transport is handling multiple addresses, the value from the first address is
 used.
 
-&$domain_data$& is also set when the &%domains%& condition in an ACL matches a
-domain by means of a lookup. The data read by the lookup is available during
-the rest of the ACL statement. In all other situations, this variable expands
-to nothing.
+&$domain_data$& set in an ACL is available during
+the rest of the ACL statement.
 
 .vitem &$exim_gid$&
 .vindex "&$exim_gid$&"
@@ -12126,6 +12671,7 @@ This variable contains the version string of the Exim build.
 The first character is a major version number, currently 4.
 Then after a dot, the next group of digits is a minor version number.
 There may be other characters following the minor version.
+This value may be overridden by the &%exim_version%& main config option.
 
 .vitem &$header_$&<&'name'&>
 This is not strictly an expansion variable. It is expansion syntax for
@@ -12186,7 +12732,7 @@ result of the lookup is made available in the &$host_data$& variable. This
 allows you, for example, to do things like this:
 .code
 deny  hosts = net-lsearch;/some/file
-message = $host_data
+      message = $host_data
 .endd
 .vitem &$host_lookup_deferred$&
 .cindex "host name" "lookup, failure of"
@@ -12219,7 +12765,7 @@ the result, the name is not accepted, and &$host_lookup_deferred$& is set to
 
 .cindex authentication "expansion item"
 Performing these checks sets up information used by the
-&$authresults$& expansion item.
+&%authresults%& expansion item.
 
 
 .vitem &$host_lookup_failed$&
@@ -12245,13 +12791,11 @@ option in the &(appendfile)& transport. The variable contains the inode number
 of the temporary file which is about to be renamed. It can be used to construct
 a unique name for the file.
 
-.vitem &$interface_address$&
+.vitem &$interface_address$& &&&
+       &$interface_port$&
 .vindex "&$interface_address$&"
-This is an obsolete name for &$received_ip_address$&.
-
-.vitem &$interface_port$&
 .vindex "&$interface_port$&"
-This is an obsolete name for &$received_port$&.
+These are obsolete names for &$received_ip_address$& and &$received_port$&.
 
 .vitem &$item$&
 .vindex "&$item$&"
@@ -12285,13 +12829,24 @@ Global address rewriting happens when a message is received, so the value of
 because a message may have many recipients and the system filter is called just
 once.
 
-.vindex "&$local_part_prefix$&"
-.vindex "&$local_part_suffix$&"
-.cindex affix variables
-If a local part prefix or suffix has been recognized, it is not included in the
-value of &$local_part$& during routing and subsequent delivery. The values of
-any prefix or suffix are in &$local_part_prefix$& and
-&$local_part_suffix$&, respectively.
+.cindex "tainted data"
+If the origin of the data is an incoming message,
+the result of expanding this variable is tainted and
+may not be further expanded or used as a filename.
+
+&*Warning*&: the content of this variable is usually provided by a potential
+attacker.
+Consider carefully the implications of using it unvalidated as a name
+for file access.
+This presents issues for users' &_.forward_& and filter files.
+For traditional full user accounts, use &%check_local_users%& and the
+&$local_part_data$& variable rather than this one.
+For virtual users, store a suitable pathname component in the database
+which is used for account name validation, and use that retrieved value
+rather than this variable.
+Often &$local_part_data$& is usable in this role.
+If needed, use a router &%address_data%& or &%set%& option for
+the retrieved data.
 
 When a message is being delivered to a file, pipe, or autoreply transport as a
 result of aliasing or forwarding, &$local_part$& is set to the local part of
@@ -12327,29 +12882,32 @@ to process local parts in a case-dependent manner in a router, you can set the
 
 .vitem &$local_part_data$&
 .vindex "&$local_part_data$&"
-When the &%local_parts%& option on a router matches a local part by means of a
-lookup, the data read by the lookup is available during the running of the
-router as &$local_part_data$&. In addition, if the driver routes the address
-to a transport, the value is available in that transport. If the transport is
-handling multiple addresses, the value from the first address is used.
-
-&$local_part_data$& is also set when the &%local_parts%& condition in an ACL
-matches a local part by means of a lookup. The data read by the lookup is
-available during the rest of the ACL statement. In all other situations, this
-variable expands to nothing.
-
-.vitem &$local_part_prefix$&
-.vindex "&$local_part_prefix$&"
+When the &%local_parts%& condition on a router or ACL
+matches a local part list
+the match value is copied to &$local_part_data$&.
+This is an enhancement over previous versions of Exim, when it only
+applied to the data read by a lookup.
+For details on match values see section &<<SECTlistresults>>& et. al.
+
+The &%check_local_user%& router option also sets this variable.
+
+.vindex &$local_part_prefix$& &&&
+	&$local_part_prefix_v$& &&&
+	&$local_part_suffix$& &&&
+	&$local_part_suffix_v$&
 .cindex affix variables
-When an address is being routed or delivered, and a
-specific prefix for the local part was recognized, it is available in this
-variable, having been removed from &$local_part$&.
+If a local part prefix or suffix has been recognized, it is not included in the
+value of &$local_part$& during routing and subsequent delivery. The values of
+any prefix or suffix are in &$local_part_prefix$& and
+&$local_part_suffix$&, respectively.
+.cindex "tainted data"
+If the specification did not include a wildcard then
+the affix variable value is not tainted.
 
-.vitem &$local_part_suffix$&
-.vindex "&$local_part_suffix$&"
-When an address is being routed or delivered, and a
-specific suffix for the local part was recognized, it is available in this
-variable, having been removed from &$local_part$&.
+If the affix specification included a wildcard then the portion of
+the affix matched by the wildcard is in
+&$local_part_prefix_v$& or &$local_part_suffix_v$& as appropriate,
+and both the whole and varying values are tainted.
 
 .vitem &$local_scan_data$&
 .vindex "&$local_scan_data$&"
@@ -12425,7 +12983,7 @@ when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
 This variable contains the number of bytes in the longest line that was
 received as part of the message, not counting the line termination
 character(s).
-It is not valid if the &%spool_files_wireformat%& option is used.
+It is not valid if the &%spool_wireformat%& option is used.
 
 .vitem &$message_age$&
 .cindex "message" "age of"
@@ -12469,7 +13027,7 @@ separates the body from the header. Newlines are included in the count. See
 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
 
 If the spool file is wireformat
-(see the &%spool_files_wireformat%& main option)
+(see the &%spool_wireformat%& main option)
 the CRLF line-terminators are included in the count.
 
 .vitem &$message_exim_id$&
@@ -12515,14 +13073,14 @@ header and the body).
 
 Here is an example of the use of this variable in a DATA ACL:
 .code
-deny message   = Too many lines in message header
-     condition = \
+deny condition = \
       ${if <{250}{${eval:$message_linecount - $body_linecount}}}
+     message   = Too many lines in message header
 .endd
 In the MAIL and RCPT ACLs, the value is zero because at that stage the
 message has not yet been received.
 
-This variable is not valid if the &%spool_files_wireformat%& option is used.
+This variable is not valid if the &%spool_wireformat%& option is used.
 
 .vitem &$message_size$&
 .cindex "size" "of message"
@@ -12542,7 +13100,22 @@ While running a per message ACL (mail/rcpt/predata), &$message_size$&
 contains the size supplied on the MAIL command, or -1 if no size was given. The
 value may not, of course, be truthful.
 
-.vitem &$mime_$&&'xxx'&
+.vitem &$mime_anomaly_level$& &&&
+       &$mime_anomaly_text$& &&&
+       &$mime_boundary$& &&&
+       &$mime_charset$& &&&
+       &$mime_content_description$& &&&
+       &$mime_content_disposition$& &&&
+       &$mime_content_id$& &&&
+       &$mime_content_size$& &&&
+       &$mime_content_transfer_encoding$& &&&
+       &$mime_content_type$& &&&
+       &$mime_decoded_filename$& &&&
+       &$mime_filename$& &&&
+       &$mime_is_coverletter$& &&&
+       &$mime_is_multipart$& &&&
+       &$mime_is_rfc822$& &&&
+       &$mime_part_count$&
 A number of variables whose names start with &$mime$& are
 available when Exim is compiled with the content-scanning extension. For
 details, see section &<<SECTscanmimepart>>&.
@@ -12655,18 +13228,10 @@ For details see chapter &<<SECTproxyInbound>>&.
 This variable is set to &"yes"& if PRDR was requested by the client for the
 current message, otherwise &"no"&.
 
-.vitem &$prvscheck_address$&
-This variable is used in conjunction with the &%prvscheck%& expansion item,
-which is described in sections &<<SECTexpansionitems>>& and
-&<<SECTverifyPRVS>>&.
-
-.vitem &$prvscheck_keynum$&
-This variable is used in conjunction with the &%prvscheck%& expansion item,
-which is described in sections &<<SECTexpansionitems>>& and
-&<<SECTverifyPRVS>>&.
-
-.vitem &$prvscheck_result$&
-This variable is used in conjunction with the &%prvscheck%& expansion item,
+.vitem &$prvscheck_address$& &&&
+       &$prvscheck_keynum$& &&&
+       &$prvscheck_result$&
+These variables are used in conjunction with the &%prvscheck%& expansion item,
 which is described in sections &<<SECTexpansionitems>>& and
 &<<SECTverifyPRVS>>&.
 
@@ -12681,10 +13246,27 @@ or if not set, the value of &$qualify_domain$&.
 
 .vitem &$queue_name$&
 .vindex &$queue_name$&
-.cindex "named queues"
+.cindex "named queues" variable
 .cindex queues named
 The name of the spool queue in use; empty for the default queue.
 
+.vitem &$queue_size$&
+.vindex "&$queue_size$&"
+.cindex "queue" "size of"
+.cindex "spool" "number of messages"
+This variable contains the number of messages queued.
+It is evaluated on demand, but no more often than once every minute.
+If there is no daemon notifier socket open, the value will be
+an empty string.
+
+.vitem &$r_...$&
+.vindex &$r_...$&
+.cindex router variables
+Values can be placed in these variables by the &%set%& option of a router.
+They can be given any name that starts with &$r_$&.
+The values persist for the address being handled through subsequent routers
+and the eventual transport.
+
 .vitem &$rcpt_count$&
 .vindex "&$rcpt_count$&"
 When a message is being received by SMTP, this variable contains the number of
@@ -12718,11 +13300,13 @@ variable contains that address when the &'Received:'& header line is being
 built. The value is copied after recipient rewriting has happened, but before
 the &[local_scan()]& function is run.
 
-.vitem &$received_ip_address$&
+.vitem &$received_ip_address$& &&&
+       &$received_port$&
 .vindex "&$received_ip_address$&"
-As soon as an Exim server starts processing an incoming TCP/IP connection, this
-variable is set to the address of the local IP interface, and &$received_port$&
-is set to the local port number. (The remote IP address and port are in
+.vindex "&$received_port$&"
+As soon as an Exim server starts processing an incoming TCP/IP connection, these
+variables are set to the address and port on the local IP interface.
+(The remote IP address and port are in
 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
 the port value is -1 unless it has been set using the &%-oMi%& command line
 option.
@@ -12735,10 +13319,6 @@ messages that are received, thus making these variables available at delivery
 time.
 For outbound connections see &$sending_ip_address$&.
 
-.vitem &$received_port$&
-.vindex "&$received_port$&"
-See &$received_ip_address$&.
-
 .vitem &$received_protocol$&
 .vindex "&$received_protocol$&"
 When a message is being processed, this variable contains the name of the
@@ -12991,6 +13571,16 @@ library, by setting:
 dns_dnssec_ok = 1
 .endd
 
+In addition, on Linux with glibc 2.31 or newer the resolver library will
+default to stripping out a successful validation status.
+This will break a previously working Exim installation.
+Provided that you do trust the resolver (ie, is on localhost) you can tell
+glibc to pass through any successful validation with a new option in
+&_/etc/resolv.conf_&:
+.code
+options trust-ad
+.endd
+
 Exim does not perform DNSSEC validation itself, instead leaving that to a
 validating resolver (e.g. unbound, or bind with suitable configuration).
 
@@ -13170,7 +13760,11 @@ filter file to set values that can be tested in users' filter files. For
 example, a system filter could set a value indicating how likely it is that a
 message is junk mail.
 
-.vitem &$spam_$&&'xxx'&
+.vitem &$spam_score$& &&&
+       &$spam_score_int$& &&&
+       &$spam_bar$& &&&
+       &$spam_report$& &&&
+       &$spam_action$&
 A number of variables whose names start with &$spam$& are available when Exim
 is compiled with the content-scanning extension. For details, see section
 &<<SECTscanspamass>>&.
@@ -13247,6 +13841,7 @@ or a &%def%& condition.
 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
 when a list of more than one
 file is used for &%tls_certificate%&, this variable is not reliable.
+The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
 
 .vitem &$tls_in_peercert$&
 .vindex "&$tls_in_peercert$&"
@@ -13303,6 +13898,10 @@ The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during m
 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
 becomes the same as &$tls_out_cipher$&.
 
+.vitem &$tls_in_cipher_std$&
+.vindex "&$tls_in_cipher_std$&"
+As above, but returning the RFC standard name for the cipher suite.
+
 .vitem &$tls_out_cipher$&
 .vindex "&$tls_out_cipher$&"
 This variable is
@@ -13311,6 +13910,10 @@ and then set to the outgoing cipher suite if one is negotiated. See chapter
 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
 details of the &(smtp)& transport.
 
+.vitem &$tls_out_cipher_std$&
+.vindex "&$tls_out_cipher_std$&"
+As above, but returning the RFC standard name for the cipher suite.
+
 .vitem &$tls_out_dane$&
 .vindex &$tls_out_dane$&
 DANE active status.  See section &<<SECDANE>>&.
@@ -13357,10 +13960,21 @@ the value of the Distinguished Name of the certificate is made available in the
 If certificate verification fails it may refer to a failing chain element
 which is not the leaf.
 
+
+.vitem &$tls_in_resumption$& &&&
+       &$tls_out_resumption$&
+.vindex &$tls_in_resumption$&
+.vindex &$tls_out_resumption$&
+.cindex TLS resumption
+Observability for TLS session resumption.  See &<<SECTresumption>>& for details.
+
+
 .vitem &$tls_in_sni$&
 .vindex "&$tls_in_sni$&"
 .vindex "&$tls_sni$&"
 .cindex "TLS" "Server Name Indication"
+.cindex "TLS" SNI
+.cindex SNI "observability on server"
 When a TLS session is being established, if the client sends the Server
 Name Indication extension, the value will be placed in this variable.
 If the variable appears in &%tls_certificate%& then this option and
@@ -13376,6 +13990,8 @@ the outbound.
 .vitem &$tls_out_sni$&
 .vindex "&$tls_out_sni$&"
 .cindex "TLS" "Server Name Indication"
+.cindex "TLS" SNI
+.cindex SNI "observability in client"
 During outbound
 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
 the transport.
@@ -13384,6 +14000,17 @@ the transport.
 .vindex &$tls_out_tlsa_usage$&
 Bitfield of TLSA record types found.  See section &<<SECDANE>>&.
 
+.vitem &$tls_in_ver$&
+.vindex "&$tls_in_ver$&"
+When a message is received from a remote host over an encrypted SMTP connection
+this variable is set to the protocol version, eg &'TLS1.2'&.
+
+.vitem &$tls_out_ver$&
+.vindex "&$tls_out_ver$&"
+When a message is being delivered to a remote host over an encrypted SMTP connection
+this variable is set to the protocol version.
+
+
 .vitem &$tod_bsdinbox$&
 .vindex "&$tod_bsdinbox$&"
 The time of day and the date, in the format required for BSD-style mailbox
@@ -13445,7 +14072,8 @@ Otherwise, empty.
 
 .vitem &$version_number$&
 .vindex "&$version_number$&"
-The version number of Exim.
+The version number of Exim. Same as &$exim_version$&, may be overridden
+by the &%exim_version%& main config option.
 
 .vitem &$warn_message_delay$&
 .vindex "&$warn_message_delay$&"
@@ -13524,6 +14152,8 @@ taint mode of the Perl interpreter. You are encouraged to set this
 option to a true value. To avoid breaking existing installations, it
 defaults to false.
 
+&*Note*&: This is entirely separate from Exim's tainted-data tracking.
+
 
 .section "Calling Perl subroutines" "SECID86"
 When the configuration file includes a &%perl_startup%& option you can make use
@@ -13958,9 +14588,12 @@ listed in more than one group.
 
 .section "Miscellaneous" "SECID96"
 .table2
+.row &%add_environment%&             "environment variables"
+.row &%allow_insecure_tainted_data%& "turn taint errors into warnings"
 .row &%bi_command%&                  "to run for &%-bi%& command line option"
 .row &%debug_store%&                 "do extra internal checks"
 .row &%disable_ipv6%&                "do no IPv6 processing"
+.row &%keep_environment%&            "environment variables"
 .row &%keep_malformed%&              "for broken files &-- should not happen"
 .row &%localhost_number%&            "for unique message ids in clusters"
 .row &%message_body_newlines%&       "retain newlines in &$message_body$&"
@@ -14078,8 +14711,10 @@ listed in more than one group.
 .row &%daemon_startup_sleep%&        "time to sleep between tries"
 .row &%extra_local_interfaces%&      "not necessarily listened on"
 .row &%local_interfaces%&            "on which to listen, with optional ports"
+.row &%notifier_socket%&             "override compiled-in value"
 .row &%pid_file_path%&               "override compiled-in value"
 .row &%queue_run_max%&               "maximum simultaneous queue runners"
+.row &%smtp_backlog_monitor%&        "level to log listen backlog"
 .endtable
 
 
@@ -14155,8 +14790,10 @@ listed in more than one group.
 .row &%local_scan_timeout%&          "timeout for &[local_scan()]&"
 .row &%message_size_limit%&          "for all messages"
 .row &%percent_hack_domains%&        "recognize %-hack for these domains"
+.row &%proxy_protocol_timeout%&      "timeout for proxy protocol negotiation"
 .row &%spamd_address%&               "set interface to SpamAssassin"
 .row &%strict_acl_vars%&             "object to unset ACL variables"
+.row &%spf_smtp_comment_template%&   "template for &$spf_smtp_comment$&"
 .endtable
 
 
@@ -14178,8 +14815,10 @@ listed in more than one group.
 .table2
 .row &%gnutls_compat_mode%&          "use GnuTLS compatibility mode"
 .row &%gnutls_allow_auto_pkcs11%&    "allow GnuTLS to autoload PKCS11 modules"
+.row &%hosts_require_alpn%&          "mandatory ALPN"
 .row &%openssl_options%&             "adjust OpenSSL compatibility options"
 .row &%tls_advertise_hosts%&         "advertise TLS to these hosts"
+.row &%tls_alpn%&		     "acceptable protocol names"
 .row &%tls_certificate%&             "location of server certificate"
 .row &%tls_crl%&                     "certificate revocation list"
 .row &%tls_dh_max_bits%&             "clamp D-H bit count suggestion"
@@ -14239,7 +14878,13 @@ listed in more than one group.
 See also the &'Policy controls'& section above.
 
 .table2
-.row &%dkim_verify_signers%&         "DKIM domain for which DKIM ACL is run"
+.row &%dkim_verify_hashes%&          "DKIM hash methods accepted for signatures"
+.row &%dkim_verify_keytypes%&        "DKIM key types accepted for signatures"
+.row &%dkim_verify_min_keysizes%&    "DKIM key sizes accepted for signatures"
+.row &%dkim_verify_signers%&         "DKIM domains for which DKIM ACL is run"
+.row &%dmarc_forensic_sender%&       "DMARC sender for report messages"
+.row &%dmarc_history_file%&          "DMARC results log"
+.row &%dmarc_tld_file%&              "DMARC toplevel domains file"
 .row &%host_lookup%&                 "host name looked up for these hosts"
 .row &%host_lookup_order%&           "order of DNS and local name lookups"
 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
@@ -14284,6 +14929,7 @@ See also the &'Policy controls'& section above.
 .row &%ignore_fromline_hosts%&       "allow &""From ""& from these hosts"
 .row &%ignore_fromline_local%&       "allow &""From ""& from local SMTP"
 .row &%pipelining_advertise_hosts%&  "advertise pipelining to these hosts"
+.row &%pipelining_connect_advertise_hosts%& "advertise pipelining to these hosts"
 .row &%prdr_enable%&                 "advertise PRDR to all hosts"
 .row &%smtputf8_advertise_hosts%&    "advertise SMTPUTF8 to these hosts"
 .row &%tls_advertise_hosts%&         "advertise TLS to these hosts"
@@ -14340,6 +14986,7 @@ See also the &'Policy controls'& section above.
 .row &%hold_domains%&                "hold delivery for these domains"
 .row &%local_interfaces%&            "for routing checks"
 .row &%queue_domains%&               "no immediate delivery for these"
+.row &%queue_fast_ramp%&             "parallel delivery with 2-phase queue run"
 .row &%queue_only%&                  "no immediate delivery at all"
 .row &%queue_only_file%&             "no immediate delivery if file exists"
 .row &%queue_only_load%&             "no immediate delivery if load is high"
@@ -14386,6 +15033,7 @@ Those options that undergo string expansion before use are marked with
 .cindex "8-bit characters"
 .cindex "log" "selectors"
 .cindex "log" "8BITMIME"
+.cindex "ESMTP extensions" 8BITMIME
 This option causes Exim to send 8BITMIME in its response to an SMTP
 EHLO command, and to accept the BODY= parameter on MAIL commands.
 However, though Exim is 8-bit clean, it is not a protocol converter, and it
@@ -14524,8 +15172,10 @@ received. See chapter &<<CHAPACL>>& for further details.
 
 .option add_environment main "string list" empty
 .cindex "environment" "set values"
-This option allows to set individual environment variables that the
-currently linked libraries and programs in child processes use.
+This option adds individual environment variables that the
+currently linked libraries and programs in child processes may use.
+Each list element should be of the form &"name=value"&.
+
 See &<<SECTpipeenv>>& for the environment of &(pipe)& transports.
 
 .option admin_groups main "string list&!!" unset
@@ -14553,6 +15203,16 @@ domains (defined in the named domain list &%local_domains%& in the default
 configuration). This &"magic string"& matches the domain literal form of all
 the local host's IP addresses.
 
+.option allow_insecure_tainted_data main boolean false
+.cindex "de-tainting"
+.oindex "allow_insecure_tainted_data"
+The handling of tainted data may break older (pre 4.94) configurations.
+Setting this option to "true" turns taint errors (which result in a temporary
+message rejection) into warnings. This option is meant as mitigation only
+and deprecated already today. Future releases of Exim may ignore it.
+The &%taint%& log selector can be used to suppress even the warnings.
+
+
 
 .option allow_mx_to_ip main boolean false
 .cindex "MX record" "pointing to IP address"
@@ -14569,13 +15229,18 @@ recommended, except when you have no other choice.
 .cindex "UTF-8" "in domain name"
 Lots of discussion is going on about internationalized domain names. One
 camp is strongly in favour of just using UTF-8 characters, and it seems
-that at least two other MTAs permit this. This option allows Exim users to
-experiment if they wish.
+that at least two other MTAs permit this.
+This option allows Exim users to experiment if they wish.
 
 If it is set true, Exim's domain parsing function allows valid
 UTF-8 multicharacters to appear in domain name components, in addition to
-letters, digits, and hyphens. However, just setting this option is not
-enough; if you want to look up these domain names in the DNS, you must also
+letters, digits, and hyphens.
+
+If Exim is built with internationalization support
+and the SMTPUTF8 ESMTP option is in use (see chapter &<<CHAPi18n>>&)
+this option can be left as default.
+Without that,
+if you want to look up such domain names in the DNS, you must also
 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
 suitable setting is:
 .code
@@ -14592,6 +15257,7 @@ That is, set the option to an empty string so that no check is done.
 .option auth_advertise_hosts main "host list&!!" *
 .cindex "authentication" "advertising"
 .cindex "AUTH" "advertising"
+.cindex "ESMTP extensions" AUTH
 If any server authentication mechanisms are configured, Exim advertises them in
 response to an EHLO command only if the calling host matches this list.
 Otherwise, Exim does not advertise AUTH.
@@ -14653,12 +15319,16 @@ just the command name, it is not a complete command line. If an argument is
 required, it must come from the &%-oA%& command line option.
 
 
-.option bounce_message_file main string unset
+.option bounce_message_file main string&!! unset
 .cindex "bounce message" "customizing"
 .cindex "customizing" "bounce message"
 This option defines a template file containing paragraphs of text to be used
 for constructing bounce messages.  Details of the file's contents are given in
-chapter &<<CHAPemsgcust>>&. See also &%warn_message_file%&.
+chapter &<<CHAPemsgcust>>&.
+.cindex bounce_message_file "tainted data"
+The option is expanded to give the file path, which must be
+absolute and untainted.
+See also &%warn_message_file%&.
 
 
 .option bounce_message_text main string unset
@@ -14847,6 +15517,7 @@ may wish to deliberately disable them.
 .option chunking_advertise_hosts main "host list&!!" *
 .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.
 Hosts may use the BDAT command as an alternate to DATA.
@@ -14983,6 +15654,38 @@ etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
 to handle IPv6 literal addresses.
 
 
+.option dkim_verify_hashes main "string list" "sha256 : sha512"
+.cindex DKIM "selecting signature algorithms"
+This option gives a list of hash types which are acceptable in signatures,
+and an order of processing.
+Signatures with algorithms not in the list will be ignored.
+
+Acceptable values include:
+.code
+sha1
+sha256
+sha512
+.endd
+
+Note that the acceptance of sha1 violates RFC 8301.
+
+.option dkim_verify_keytypes main "string list" "ed25519 : rsa"
+This option gives a list of key types which are acceptable in signatures,
+and an order of processing.
+Signatures with algorithms not in the list will be ignored.
+
+
+.option dkim_verify_min_keysizes main "string list" "rsa=1024 ed25519=250"
+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 default enforces the 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
+first success.
+
 .option dkim_verify_signers main "domain list&!!" $dkim_signers
 .cindex DKIM "controlling calls to the ACL"
 This option gives a list of DKIM domains for which the DKIM ACL is run.
@@ -14991,6 +15694,14 @@ the ACL once for each signature in the message.
 See section &<<SECDKIMVFY>>&.
 
 
+.option dmarc_forensic_sender main string&!! unset
+.option dmarc_history_file main string unset
+.option dmarc_tld_file main string unset
+.cindex DMARC "main section options"
+These options control DMARC processing.
+See section &<<SECDMARC>>& for details.
+
+
 .option dns_again_means_nonexist main "domain list&!!" unset
 .cindex "DNS" "&""try again""& response; overriding"
 DNS lookups give a &"try again"& response for the DNS errors
@@ -15040,7 +15751,6 @@ This option controls whether or not an IP address, given as a CSA domain, is
 reversed and looked up in the reverse DNS, as described in more detail in
 section &<<SECTverifyCSA>>&.
 
-.new
 .option dns_cname_loops main integer 1
 .cindex DNS "CNAME following"
 This option controls the following of CNAME chains, needed if the resolver does
@@ -15051,7 +15761,6 @@ If you have an ancient one, a value of 10 is likely needed.
 The default value of one CNAME-follow is needed
 thanks to the observed return for an MX request,
 given no MX presence but a CNAME to an A, of the CNAME.
-.wen
 
 
 .option dns_dnssec_ok main integer -1
@@ -15063,6 +15772,16 @@ default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
 
 If the resolver library does not support DNSSEC then this option has no effect.
 
+On Linux with glibc 2.31 or newer this is insufficient, the resolver library
+will default to stripping out a successful validation status.
+This will break a previously working Exim installation.
+Provided that you do trust the resolver (ie, is on localhost) you can tell
+glibc to pass through any successful validation with a new option in
+&_/etc/resolv.conf_&:
+.code
+options trust-ad
+.endd
+
 
 .option dns_ipv4_lookup main "domain list&!!" unset
 .cindex "IPv6" "DNS lookup for AAAA records"
@@ -15076,6 +15795,9 @@ domain matches this list.
 This is a fudge to help with name servers that give big delays or otherwise do
 not work for the AAAA record type. In due course, when the world's name
 servers have all been upgraded, there should be no need for this option.
+Note that all lookups, including those done for verification, are affected;
+this will result in verify failure for IPv6 connections or ones using names
+only valid for IPv6 addresses.
 
 
 .option dns_retrans main time 0s
@@ -15149,13 +15871,16 @@ described in section &<<SECTlineendings>>&.
 .cindex "bounce messages" "success"
 .cindex "DSN" "success"
 .cindex "Delivery Status Notification" "success"
+.cindex "ESMTP extensions" DSN
 DSN extensions (RFC3461) will be advertised in the EHLO message to,
 and accepted from, these hosts.
-Hosts may use the NOTIFY and ENVID options on RCPT TO commands,
-and RET and ORCPT options on MAIL FROM commands.
+Hosts may use the NOTIFY and ORCPT options on RCPT TO commands,
+and RET and ENVID options on MAIL FROM commands.
 A NOTIFY=SUCCESS option requests success-DSN messages.
 A NOTIFY= option with no argument requests that no delay or failure DSNs
 are sent.
+&*Note*&: Supplying success-DSN messages has been criticised
+on privacy grounds; it can leak details of internal forwarding.
 
 .option dsn_from main "string&!!" "see below"
 .cindex "&'From:'& header line" "in bounces"
@@ -15278,6 +16003,14 @@ not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
 
 
+.option exim_version main string "current version"
+.cindex "Exim version"
+.cindex customizing "version number"
+.cindex "version number of Exim" override
+This option overrides the &$version_number$&/&$exim_version$& that Exim reports in
+various places.  Use with care; this may fool stupid security scanners.
+
+
 .option extra_local_interfaces main "string list" unset
 This option defines network interfaces that are to be considered local when
 routing, but which are not used for listening by the daemon. See section
@@ -15584,6 +16317,18 @@ hosts_connection_nolog = :
 If the &%smtp_connection%& log selector is not set, this option has no effect.
 
 
+.option hosts_require_alpn main "host list&!!" unset
+.cindex ALPN "require negotiation in server"
+.cindex TLS ALPN
+.cindex TLS "Application Layer Protocol Names"
+If the TLS library supports ALPN
+then a successful negotiation of ALPN will be required for any client
+matching the list, for TLS to be used.
+See also the &%tls_alpn%& option.
+
+&*Note*&: prevention of fallback to in-clear connection is not
+managed by this option, and should be done separately.
+
 
 .option hosts_proxy main "host list&!!" unset
 .cindex proxy "proxy protocol"
@@ -15797,6 +16542,7 @@ and no &'Sender:'& header is ever added. If, in addition, you want to retain
 &'Sender:'& header lines supplied by untrusted users, you must also set
 &%local_sender_retain%& to be true.
 
+.cindex "envelope from"
 .cindex "envelope sender"
 These options affect only the header lines in the message. The envelope sender
 is still forced to be the login id at the qualify domain unless
@@ -15897,6 +16643,8 @@ when Exim is entered, so it can, for example, contain a reference to the host
 name. If no specific path is set for the log files at compile or runtime,
 or if the option is unset at runtime (i.e.  &`log_file_path = `&)
 they are written in a sub-directory called &_log_& in Exim's spool directory.
+A path must start with a slash.
+To send to syslog, use the word &"syslog"&.
 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
 used. If this string is fixed at your installation (contains no expansion
@@ -16026,6 +16774,11 @@ to depend on the IP address of the remote host for messages arriving via
 TCP/IP. After expansion, the value must be a sequence of decimal digits,
 optionally followed by K or M.
 
+.cindex "SIZE" "ESMTP extension, advertising"
+.cindex "ESMTP extensions" SIZE
+If nonzero the value will be advertised as a parameter to the ESMTP SIZE
+service extension keyword.
+
 &*Note*&: This limit cannot be made to depend on a message's sender or any
 other properties of an individual message, because it has to be advertised in
 the server's response to EHLO. String expansion failure causes a temporary
@@ -16103,7 +16856,26 @@ harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
 transport driver.
 
 
-.option openssl_options main "string list" "+no_sslv2 +single_dh_use +no_ticket"
+.option notifier_socket main string "$spool_directory/exim_daemon_notify"
+This option gives the name for a unix-domain socket on which the daemon
+listens for work and information-requests.
+Only installations running multiple daemons sharing a spool directory
+should need to modify the default.
+
+The option is expanded before use.
+If the platform supports Linux-style abstract socket names, the result
+is used with a nul byte prefixed.
+Otherwise,
+it should be a full path name and use a directory accessible
+to Exim.
+
+If this option is set as empty,
+or the command line &%-oY%& option is used, or
+the command line uses a &%-oX%& option and does not use &%-oP%&,
+then a notifier socket is not created.
+
+
+.option openssl_options main "string list" "+no_sslv2 +no_sslv3 +single_dh_use +no_ticket +no_renegotiation"
 .cindex "OpenSSL "compatibility options"
 This option allows an administrator to adjust the SSL options applied
 by OpenSSL to connections.  It is given as a space-separated list of items,
@@ -16244,9 +17016,9 @@ interpreter. See chapter &<<CHAPperl>>& for details of its use.
 This option is available only when Exim is built with an embedded Perl
 interpreter. See chapter &<<CHAPperl>>& for details of its use.
 
-.option perl_startup main boolean false
+.option perl_taintmode main boolean false
 .cindex "Perl"
-This Option enables the taint mode of the embedded Perl interpreter.
+This option enables the taint mode of the embedded Perl interpreter.
 
 
 .option pgsql_servers main "string list" unset
@@ -16275,6 +17047,7 @@ of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
 
 .option pipelining_advertise_hosts main "host list&!!" *
 .cindex "PIPELINING" "suppressing advertising"
+.cindex "ESMTP extensions" PIPELINING
 This option can be used to suppress the advertisement of the SMTP
 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
@@ -16283,9 +17056,24 @@ for each SMTP command and response. When PIPELINING is advertised, Exim assumes
 that clients will use it; &"out of order"& commands that are &"expected"& do
 not count as protocol errors (see &%smtp_max_synprot_errors%&).
 
+.option pipelining_connect_advertise_hosts main "host list&!!" *
+.cindex "pipelining" "early connection"
+.cindex "pipelining" PIPE_CONNECT
+.cindex "ESMTP extensions" PIPE_CONNECT
+If Exim is built with the SUPPORT_PIPE_CONNECT build option
+this option controls which hosts the facility is advertised to
+and from which pipeline early-connection (before MAIL) SMTP
+commands are acceptable.
+When used, the pipelining saves on roundtrip times.
+
+See also the &%hosts_pipe_connect%& smtp transport option.
+
+The SMTP service extension keyword advertised is &"PIPE_CONNECT"&.
+
 
 .option prdr_enable main boolean false
 .cindex "PRDR" "enabling on server"
+.cindex "ESMTP extensions" PRDR
 This option can be used to enable the Per-Recipient Data Response extension
 to SMTP, defined by Eric Hall.
 If the option is set, PRDR is advertised by Exim when operating as a server.
@@ -16361,6 +17149,12 @@ admin user unless &%prod_requires_admin%& is set false. See also
 &%queue_list_requires_admin%& and &%commandline_checks_require_admin%&.
 
 
+.option proxy_protocol_timeout main time 3s
+.cindex proxy "proxy protocol"
+This option sets the timeout for proxy protocol negotiation.
+For details see section &<<SECTproxyInbound>>&.
+
+
 .option qualify_domain main string "see below"
 .cindex "domain" "for qualifying addresses"
 .cindex "address" "qualification"
@@ -16396,6 +17190,15 @@ domains that do not match are processed. All other deliveries wait until the
 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
 
 
+.option queue_fast_ramp main boolean false
+.cindex "queue runner" "two phase"
+.cindex "queue" "double scanning"
+If set to true, two-phase queue runs, initiated using &%-qq%& on the
+command line, may start parallel delivery processes during their first
+phase.  This will be done when a threshold number of messages have been
+routed for a single host.
+
+
 .option queue_list_requires_admin main boolean true
 .cindex "restricting access to features"
 .oindex "&%-bp%&"
@@ -16506,13 +17309,14 @@ run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
 the daemon's command line.
 
 .cindex queues named
-.cindex "named queues"
+.cindex "named queues" "resource limit"
 To set limits for different named queues use
 an expansion depending on the &$queue_name$& variable.
 
 .option queue_smtp_domains main "domain list&!!" unset
 .cindex "queueing incoming messages"
 .cindex "message" "queueing remote deliveries"
+.cindex "first pass routing"
 When this option is set, a delivery process is started whenever a message is
 received, routing is performed, and local deliveries take place.
 However, if any SMTP deliveries are required for domains that match
@@ -16543,17 +17347,19 @@ 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. The default setting is:
+header lines.
+The default setting is:
 
 .code
 received_header_text = Received: \
   ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
-  {${if def:sender_ident \
-  {from ${quote_local_part:$sender_ident} }}\
-  ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
+    {${if def:sender_ident \
+      {from ${quote_local_part:$sender_ident} }}\
+        ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
   by $primary_hostname \
-  ${if def:received_protocol {with $received_protocol}} \
-  ${if def:tls_in_cipher {($tls_in_cipher)\n\t}}\
+  ${if def:received_protocol {with $received_protocol }}\
+  ${if def:tls_in_ver        { ($tls_in_ver)}}\
+  ${if def:tls_in_cipher_std { tls $tls_in_cipher_std\n\t}}\
   (Exim $version_number)\n\t\
   ${if def:sender_address \
   {(envelope-from <$sender_address>)\n\t}}\
@@ -16561,7 +17367,8 @@ received_header_text = Received: \
   ${if def:received_for {\n\tfor $received_for}}
 .endd
 
-The reference to the TLS cipher is omitted when Exim is built without TLS
+The references to the TLS version and cipher are
+omitted when Exim is built without TLS
 support. The use of conditional expansions ensures that this works for both
 locally generated messages and messages received from remote hosts, giving
 header lines such as the following:
@@ -16603,7 +17410,7 @@ or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
 option was not set.
 
 
-.option recipients_max main integer 0
+.option recipients_max main integer 50000
 .cindex "limit" "number of recipients"
 .cindex "recipient" "maximum number"
 If this option is set greater than zero, it specifies the maximum number of
@@ -16648,6 +17455,9 @@ manager, there is no way of controlling the total number of simultaneous
 deliveries if the configuration allows a delivery attempt as soon as a message
 is received.
 
+See also the &%max_parallel%& generic transport option,
+and the &%serialize_hosts%& smtp transport option.
+
 .cindex "number of deliveries"
 .cindex "delivery" "maximum number of"
 If you want to control the total number of deliveries on the system, you
@@ -16738,12 +17548,6 @@ it qualifies them only if the message came from a host that matches
 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
 using TCP/IP), and the &%-bnq%& option was not set.
 
-.option set_environment main "string list" empty
-.cindex "environment"
-This option allows to set individual environment variables that the
-currently linked libraries and programs in child processes use. The
-default list is empty,
-
 
 .option slow_lookup_log main integer 0
 .cindex "logging" "slow lookups"
@@ -16822,7 +17626,7 @@ live with.
 . 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 &&&
+.option "smtp_accept_max_per_connection" main integer&!! 1000 &&&
          smtp_accept_max_per_connection
 .cindex "SMTP" "limiting incoming message count"
 .cindex "limit" "messages per SMTP connection"
@@ -16832,6 +17636,9 @@ results in the transfer of a message. After the limit is reached, a 421
 response is given to subsequent MAIL commands. This limit is a safety
 precaution against a client that goes mad (incidents of this type have been
 seen).
+The option is expanded after the HELO or EHLO is received
+and may depend on values available at that time.
+An empty or zero value after expansion removes the limit.
 
 
 .option smtp_accept_max_per_host main string&!! unset
@@ -16939,6 +17746,14 @@ messages, it is also used as the default for HELO commands in callout
 verification if there is no remote transport from which to obtain a
 &%helo_data%& value.
 
+.option smtp_backlog_monitor main integer 0
+.cindex "connection backlog" monitoring
+If this option is set to greater than zero, and the backlog of available
+TCP connections on a socket listening for SMTP is larger than it, a line
+is logged giving the value and the socket address and port.
+The value is retrived jsut before an accept call.
+This facility is only available on Linux.
+
 .option smtp_banner main string&!! "see below"
 .cindex "SMTP" "welcome banner"
 .cindex "banner for SMTP"
@@ -16969,7 +17784,7 @@ is zero). If there isn't enough space, a temporary error code is returned.
 
 
 .option smtp_connect_backlog main integer 20
-.cindex "connection backlog"
+.cindex "connection backlog" "set maximum"
 .cindex "SMTP" "connection backlog"
 .cindex "backlog of connections"
 This option specifies a maximum number of waiting SMTP connections. Exim passes
@@ -17007,6 +17822,7 @@ hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
 
 .option smtp_etrn_command main string&!! unset
 .cindex "ETRN" "command to be run"
+.cindex "ESMTP extensions" ETRN
 .vindex "&$domain$&"
 If this option is set, the given command is run whenever an SMTP ETRN
 command is received from a host that is permitted to issue such commands (see
@@ -17018,6 +17834,11 @@ example:
 smtp_etrn_command = /etc/etrn_command $domain \
                     $sender_host_address
 .endd
+If the option is not set, the argument for the ETRN command must
+be a &'#'& followed by an address string.
+In this case an &'exim -R <string>'& command is used;
+if the ETRN ACL has set up a named-queue then &'-MCG <queue>'& is appended.
+
 A new process is created to run the command, but Exim does not wait for it to
 complete. Consequently, its status cannot be checked. If the command cannot be
 run, a line is written to the panic log, but the ETRN caller still receives
@@ -17180,7 +18001,8 @@ example, instead of &"Administrative prohibition"&, it might give:
 
 
 .option smtputf8_advertise_hosts main "host list&!!" *
-.cindex "SMTPUTF8" "advertising"
+.cindex "SMTPUTF8" "ESMTP extension, advertising"
+.cindex "ESMTP extensions" SMTPUTF8
 When Exim is built with support for internationalised mail names,
 the availability thereof is advertised in
 response to EHLO only to those client hosts that match this option. See
@@ -17198,6 +18020,46 @@ See section &<<SECTscanspamass>>& for more details.
 This option is available when Exim is compiled with SPF support.
 See section &<<SECSPF>>& for more details.
 
+.option spf_smtp_comment_template main string&!! "Please%_see%_http://www.open-spf.org/Why"
+This option is available when Exim is compiled with SPF support.  It
+allows the customisation of the SMTP comment that the SPF library
+generates.  You are strongly encouraged to link to your own explanative
+site. The template must not contain spaces. If you need spaces in the
+output, use the proper placeholder. If libspf2 can not parse the
+template, it uses a built-in default broken link. The following placeholders
+(along with Exim variables (but see below)) are allowed in the template:
+.ilist
+&*%_*&: A space.
+.next
+&*%{L}*&: Envelope sender's local part.
+.next
+&*%{S}*&: Envelope sender.
+.next
+&*%{O}*&: Envelope sender's domain.
+.next
+&*%{D}*&: Current(?) domain.
+.next
+&*%{I}*&: SMTP client Ip.
+.next
+&*%{C}*&: SMTP client pretty IP.
+.next
+&*%{T}*&: Epoch time (UTC).
+.next
+&*%{P}*&: SMTP client domain name.
+.next
+&*%{V}*&: IP version.
+.next
+&*%{H}*&: EHLO/HELO domain.
+.next
+&*%{R}*&: Receiving domain.
+.endlist
+The capitalized placeholders do proper URL encoding, if you use them
+lowercased, no encoding takes place.  This list was compiled from the
+libspf2 sources.
+
+A note on using Exim variables: As
+currently the SPF library is initialized before the SMTP EHLO phase,
+the variables useful for expansion are quite limited.
 
 
 .option split_spool_directory main boolean false
@@ -17349,6 +18211,7 @@ syslog. The value must be no longer than 32 characters. See chapter
 
 .option syslog_timestamp main boolean true
 .cindex "syslog" "timestamps"
+.cindex timestamps syslog
 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
 details of Exim's logging.
@@ -17471,6 +18334,7 @@ unfortunately not all, operating systems.
 .cindex "TLS" "advertising"
 .cindex "encryption" "on SMTP connection"
 .cindex "SMTP" "encrypted connection"
+.cindex "ESMTP extensions" STARTTLS
 When Exim is built with support for TLS encrypted connections, the availability
 of the STARTTLS command to set up an encrypted session is advertised in
 response to EHLO only to those client hosts that match this option. See
@@ -17480,12 +18344,23 @@ using the &%tls_certificate%& option.  If TLS support for incoming connections
 is not required the &%tls_advertise_hosts%& option should be set empty.
 
 
-.option tls_certificate main string list&!! unset
+.option tls_alpn main "string list&!!" "smtp : esmtp"
+.cindex TLS "Application Layer Protocol Names"
+.cindex TLS ALPN
+.cindex ALPN "set acceptable names for server"
+If this option is set,
+the TLS library supports ALPN,
+and the client offers either more than
+ALPN name or a name which does not match the list,
+the TLS connection is declined.
+
+
+.option tls_certificate main "string list&!!" unset
 .cindex "TLS" "server certificate; location of"
 .cindex "certificate" "server, location of"
 The value of this option is expanded, and must then be a list of absolute paths to
-files which contains the server's certificates.  Commonly only one file is
-needed.
+files which contain the server's certificates (in PEM format).
+Commonly only one file is needed.
 The server's private key is also
 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
 &<<CHAPTLS>>& for further details.
@@ -17496,22 +18371,23 @@ use when sending messages as a client, you must set the &%tls_certificate%&
 option in the relevant &(smtp)& transport.
 
 &*Note*&: If you use filenames based on IP addresses, change the list
-separator in the usual way (&<<SECTlistsepchange>>&) >to avoid confusion under IPv6.
+separator in the usual way (&<<SECTlistsepchange>>&) to avoid confusion under IPv6.
 
 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
 when a list of more than one
 file is used, the &$tls_in_ourcert$& variable is unreliable.
+The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
 
-&*Note*&: OCSP stapling is not usable under OpenSSL
-when a list of more than one file is used.
-
+.cindex SNI "selecting server certificate based on"
 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
 if the OpenSSL build supports TLS extensions and the TLS client sends the
 Server Name Indication extension, then this option and others documented in
 &<<SECTtlssni>>& will be re-expanded.
 
-If this option is unset or empty a fresh self-signed certificate will be
-generated for every connection.
+If this option is unset or empty a self-signed certificate will be
+used.
+Under Linux this is generated at daemon startup; on other platforms it will be
+generated fresh for every connection.
 
 .option tls_crl main string&!! unset
 .cindex "TLS" "server certificate revocation list"
@@ -17605,8 +18481,17 @@ of the later IKE values, which led into RFC7919 providing new fixed constants
 (the "ffdhe" identifiers).
 
 At this point, all of the "ike" values should be considered obsolete;
-they're still in Exim to avoid breaking unusual configurations, but are
+they are still in Exim to avoid breaking unusual configurations, but are
 candidates for removal the next time we have backwards-incompatible changes.
+.new
+Two of them in particular (&`ike1`& and &`ike22`&) are called out by 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
+are used, warnings will be logged in the paniclog, and if any are used then
+warnings will be logged in the mainlog.
+All four will be removed in a future Exim release.
+.wen
 
 The TLS protocol does not negotiate an acceptable size for this; clients tend
 to hard-drop connections if what is offered by the server is unacceptable,
@@ -17649,11 +18534,29 @@ status proof for the server's certificate, as obtained from the
 Certificate Authority.
 
 Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
+The macro "_HAVE_TLS_OCSP" will be defined for those versions.
 
-For GnuTLS 3.5.6 or later the expanded value of this option can be a list
+For OpenSSL 1.1.0 or later, and
+for GnuTLS 3.5.6 or later the expanded value of this option can be a list
 of files, to match a list given for the &%tls_certificate%& option.
 The ordering of the two lists must match.
-
+The macro "_HAVE_TLS_OCSP_LIST" will be defined for those versions.
+
+The file(s) should be in DER format,
+except for GnuTLS 3.6.3 or later
+or for OpenSSL,
+when an optional filetype prefix can be used.
+The prefix must be one of "DER" or "PEM", followed by
+a single space.  If one is used it sets the format for subsequent
+files in the list; the initial format is DER.
+If multiple proofs are wanted, for multiple chain elements
+(this only works under TLS1.3)
+they must be coded as a combined OCSP response.
+
+Although GnuTLS will accept PEM files with multiple separate
+PEM blobs (ie. separate OCSP responses), it sends them in the
+TLS Certificate record interleaved with the certificates of the chain;
+although a GnuTLS client is happy with that, an OpenSSL client is not.
 
 .option tls_on_connect_ports main "string list" unset
 .cindex SSMTP
@@ -17665,7 +18568,7 @@ further details, see section &<<SECTsupobssmt>>&.
 
 
 
-.option tls_privatekey main string list&!! unset
+.option tls_privatekey main "string list&!!" unset
 .cindex "TLS" "server private key; location of"
 The value of this option is expanded, and must then be a list of absolute paths to
 files which contains the server's private keys.
@@ -17699,6 +18602,12 @@ preference order of the available ciphers. Details are given in sections
 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
 
 
+.option tls_resumption_hosts main "host list&!!" unset
+.cindex TLS resumption
+This option controls which connections to offer the TLS resumption feature.
+See &<<SECTresumption>>& for details.
+
+
 .option tls_try_verify_hosts main "host list&!!" unset
 .cindex "TLS" "client certificate verification"
 .cindex "certificate" "verification of client"
@@ -17733,7 +18642,9 @@ than the public cert of individual clients.  With both OpenSSL and GnuTLS, if
 the value is a file then the certificates are sent by Exim as a server to
 connecting clients, defining the list of accepted certificate authorities.
 Thus the values defined should be considered public data.  To avoid this,
-use the explicit directory version.
+use the explicit directory version. (If your peer is Exim up to 4.85,
+using GnuTLS, you may need to send the CAs (thus using the file
+variant). Otherwise the peer doesn't send its certificate.)
 
 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
 
@@ -17753,7 +18664,8 @@ either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
 Any client that matches &%tls_verify_hosts%& is constrained by
 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
 present one of the listed certificates. If it does not, the connection is
-aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
+aborted.
+&*Warning*&: Including a host in &%tls_verify_hosts%& does not require
 the host to use TLS. It can still send SMTP commands through unencrypted
 connections. Forcing a client to use TLS has to be done separately using an
 ACL to reject inappropriate commands when the connection is not encrypted.
@@ -17811,6 +18723,7 @@ See &%unknown_login%&.
 .cindex "sender" "setting by untrusted user"
 .cindex "untrusted user setting sender"
 .cindex "user" "untrusted setting sender"
+.cindex "envelope from"
 .cindex "envelope sender"
 When an untrusted user submits a message to Exim using the standard input, Exim
 normally creates an envelope sender address from the user's login and the
@@ -17886,14 +18799,18 @@ regular expression by a parenthesized subpattern. The default value for
 See &%uucp_from_pattern%& above.
 
 
-.option warn_message_file main string unset
+.option warn_message_file main string&!! unset
 .cindex "warning of delay" "customizing the message"
 .cindex "customizing" "warning message"
 This option defines a template file containing paragraphs of text to be used
 for constructing the warning message which is sent by Exim when a message has
 been in the queue for a specified amount of time, as specified by
 &%delay_warning%&. Details of the file's contents are given in chapter
-&<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
+&<<CHAPemsgcust>>&.
+.cindex warn_message_file "tainted data"
+The option is expanded to give the file path, which must be
+absolute and untainted.
+See also &%bounce_message_file%&.
 
 
 .option write_rejectlog main boolean true
@@ -17921,6 +18838,9 @@ which the preconditions are tested. The order of expansion of the options that
 provide data for a transport is: &%errors_to%&, &%headers_add%&,
 &%headers_remove%&, &%transport%&.
 
+The name of a router is limited to be &drivernamemax; ASCII characters long;
+prior to Exim 4.95 names would be silently truncated at this length, but now
+it is enforced.
 
 
 .option address_data routers string&!! unset
@@ -17961,6 +18881,8 @@ file = ${extract{mailbox}{$address_data}}
 This makes the configuration file less messy, and also reduces the number of
 lookups (though Exim does cache lookups).
 
+See also the &%set%& option below.
+
 .vindex "&$sender_address_data$&"
 .vindex "&$address_data$&"
 The &%address_data%& facility is also useful as a means of passing information
@@ -18045,7 +18967,10 @@ address (with affixes removed if relevant) is the name of an account on the
 local system. The check is done by calling the &[getpwnam()]& function rather
 than trying to read &_/etc/passwd_& directly. This means that other methods of
 holding password data (such as NIS) are supported. If the local part is a local
-user, &$home$& is set from the password data, and can be tested in other
+user,
+.cindex "tainted data" "de-tainting"
+&$local_part_data$& is set to an untainted version of the local part and
+&$home$& is set from the password data. The latter can be tested in other
 preconditions that are evaluated after this one (the order of evaluation is
 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
 overridden by &%router_home_directory%&. If the local part is not a local user,
@@ -18166,13 +19091,13 @@ or for any deliveries caused by this router. You should not set this option
 unless you really, really know what you are doing. See also the generic
 transport option of the same name.
 
-.option dnssec_request_domains routers "domain list&!!" unset
+.option dnssec_request_domains routers "domain list&!!" *
 .cindex "MX record" "security"
 .cindex "DNSSEC" "MX lookup"
 .cindex "security" "MX lookup"
 .cindex "DNS" "DNSSEC"
 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
-the dnssec request bit set.
+the DNSSEC request bit set.
 This applies to all of the SRV, MX, AAAA, A lookup sequence.
 
 .option dnssec_require_domains routers "domain list&!!" unset
@@ -18181,7 +19106,7 @@ This applies to all of the SRV, MX, AAAA, A lookup sequence.
 .cindex "security" "MX lookup"
 .cindex "DNS" "DNSSEC"
 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
-the dnssec request bit set.  Any returns not having the Authenticated Data bit
+the DNSSEC request bit set.  Any returns not having the Authenticated Data bit
 (AD bit) set will be ignored and logged as a host-lookup failure.
 This applies to all of the SRV, MX, AAAA, A lookup sequence.
 
@@ -18192,7 +19117,8 @@ This applies to all of the SRV, MX, AAAA, A lookup sequence.
 If this option is set, the router is skipped unless the current domain matches
 the list. If the match is achieved by means of a file lookup, the data that the
 lookup returned for the domain is placed in &$domain_data$& for use in string
-expansions of the driver's private options. See section &<<SECTrouprecon>>& for
+expansions of the driver's private options and in the transport.
+See section &<<SECTrouprecon>>& for
 a list of the order in which preconditions are evaluated.
 
 
@@ -18213,6 +19139,7 @@ Not effective on redirect routers.
 
 
 .option errors_to routers string&!! unset
+.cindex "envelope from"
 .cindex "envelope sender"
 .cindex "router" "changing address for errors"
 If a router successfully handles an address, it may assign the address to a
@@ -18373,15 +19300,17 @@ avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
 This option specifies a list of text headers,
 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
 that is associated with any addresses that are accepted by the router.
-Each item is separately expanded, at routing time.  However, this
-option has no effect when an address is just being verified. The way in which
+However, the option has no effect when an address is just being verified.
+Each list item is separately expanded, at transport time.
+If an item ends in *, it will match any header with the given prefix.
+The way in which
 the text is used to remove header lines at transport time is described in
 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
 the message is in the process of being transported. This means that references
 to header lines in string expansions in the transport's configuration still
 &"see"& the original header lines.
 
-The &%headers_remove%& option is expanded after &%errors_to%& and
+The &%headers_remove%& option is handled after &%errors_to%& and
 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
 the item has no effect. Other expansion failures are treated as configuration
 errors.
@@ -18486,6 +19415,10 @@ command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
 the relevant transport.
 
+.vindex &$local_part_prefix_v$&
+If wildcarding (above) was used then the part of the prefix matching the
+wildcard is available in &$local_part_prefix_v$&.
+
 When an address is being verified, &%local_part_prefix%& affects only the
 behaviour of the router. If the callout feature of verification is in use, this
 means that the full address, including the prefix, will be used during the
@@ -18548,12 +19481,13 @@ section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
 string is expanded, it is possible to make it depend on the domain, for
 example:
 .code
-local_parts = dbm;/usr/local/specials/$domain
+local_parts = dbm;/usr/local/specials/$domain_data
 .endd
 .vindex "&$local_part_data$&"
 If the match is achieved by a lookup, the data that the lookup returned
 for the local part is placed in the variable &$local_part_data$& for use in
-expansions of the router's private options. You might use this option, for
+expansions of the router's private options or in the transport.
+You might use this option, for
 example, if you have a large number of local virtual domains, and you want to
 send all postmaster mail to the same place without having to set up an alias in
 each virtual domain:
@@ -18691,7 +19625,7 @@ but the user is specified symbolically, the gid associated with the uid is
 used. For example:
 .code
 require_files = mail:/some/file
-require_files = $local_part:$home/.procmailrc
+require_files = $local_part_data:$home/.procmailrc
 .endd
 If a user or group name in a &%require_files%& list does not exist, the
 &%require_files%& condition fails.
@@ -18741,11 +19675,22 @@ latter kind.
 
 This option controls whether the local part is used to form the key for retry
 hints for addresses that suffer temporary errors while being handled by this
-router. The default value is true for any router that has &%check_local_user%&
+router. The default value is true for any router that has any of
+&%check_local_user%&,
+&%local_parts%&,
+&%condition%&,
+&%local_part_prefix%&,
+&%local_part_suffix%&,
+&%senders%& or
+&%require_files%&
 set, and false otherwise. Note that this option does not apply to hints keys
 for transport delays; they are controlled by a generic transport option of the
 same name.
 
+Failing to set this option when it is needed
+(because a remote router handles only some of the local-parts for a domain)
+can result in incorrect error messages being generated.
+
 The setting of &%retry_use_local_part%& applies only to the router on which it
 appears. If the router generates child addresses, they are routed
 independently; this setting does not become attached to them.
@@ -18874,6 +19819,32 @@ SMTP VRFY command is enabled, it must be used after MAIL if the sender address
 matters.
 
 
+.option set routers "string list" unset
+.cindex router variables
+This option may be used multiple times on a router;
+because of this the list aspect is mostly irrelevant.
+The list separator is a semicolon but can be changed in the
+usual way.
+
+Each list-element given must be of the form &"name = value"&
+and the names used must start with the string &"r_"&.
+Values containing a list-separator should have them doubled.
+When a router runs, the strings are evaluated in order,
+to create variables which are added to the set associated with
+the address.
+This is done immediately after all the preconditions, before the
+evaluation of the &%address_data%& option.
+The variable is set with the expansion of the value.
+The variables can be used by the router options
+(not including any preconditions)
+and by the transport.
+Later definitions of a given named variable will override former ones.
+Variable use is via the usual &$r_...$& syntax.
+
+This is similar to the &%address_data%& option, except that
+many independent variables can be used, with choice of naming.
+
+
 .option translate_ip_address routers string&!! unset
 .cindex "IP address" "translating"
 .cindex "packet radio"
@@ -19789,8 +20760,10 @@ semicolon is the default route list separator.
 
 
 .section "Format of one host item" "SECTformatonehostitem"
-Each item in the list of hosts is either a host name or an IP address,
-optionally with an attached port number. When no port is given, an IP address
+Each item in the list of hosts can be either a host name or an IP address,
+optionally with an attached port number, or it can be a single "+"
+(see &%hosts_randomize%&).
+When no port is given, an IP address
 is not enclosed in brackets. When a port is specified, it overrides the port
 specification on the transport. The port is separated from the name or address
 by a colon. This leads to some complications:
@@ -20282,6 +21255,17 @@ 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.
 
+.cindex "tainted data" "in filenames"
+.cindex redirect "tainted data"
+Tainted data may not be used for a filename.
+
+&*Warning*&: It is unwise to use &$local_part$& or &$domain$&
+directly for redirection,
+as they are provided by a potential attacker.
+In the examples above, &$local_part$& is used for looking up data held locally
+on the system, and not used directly (the second example derives &$home$& via
+the passsword file or database, using &$local_part$&).
+
 
 
 .section "Forward files and address verification" "SECID125"
@@ -20507,6 +21491,9 @@ It must be given as
 .code
 list1:   :include:/opt/lists/list1
 .endd
+.cindex "tainted data" "in filenames"
+.cindex redirect "tainted data"
+Tainted data may not be used for a filename.
 .next
 .cindex "address redirection" "to black hole"
 .cindex "delivery" "discard"
@@ -20558,7 +21545,7 @@ The text is not included in the response to an EXPN command. In non-SMTP cases
 the text is included in the error message that Exim generates.
 
 .cindex "SMTP" "error codes"
-By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
+By default for verify, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
 &':fail:'&. However, if the message starts with three digits followed by a
 space, optionally followed by an extended code of the form &'n.n.n'&, also
 followed by a space, and the very first digit is the same as the default error
@@ -21267,7 +22254,7 @@ local_users:
 # This transport overrides the group
 group_delivery:
   driver = appendfile
-  file = /var/spool/mail/$local_part
+  file = /var/spool/mail/$local_part_data
   group = mail
 .endd
 If &%user%& is set for a transport, its value overrides what is set in the
@@ -21395,6 +22382,10 @@ and &$original_domain$& is never set.
 .scindex IIDgenoptra1 "generic options" "transport"
 .scindex IIDgenoptra2 "options" "generic; for transports"
 .scindex IIDgenoptra3 "transport" "generic options for"
+The name of a transport is limited to be &drivernamemax; ASCII characters long;
+prior to Exim 4.95 names would be silently truncated at this length, but now
+it is enforced.
+
 The following generic options apply to all transports:
 
 
@@ -21464,6 +22455,12 @@ header, Exim has a configuration option (&%envelope_to_remove%&) which requests
 its removal from incoming messages, so that delivered messages can safely be
 resent to other recipients.
 
+&*Note:*& If used on a transport handling multiple recipients
+(the smtp transport unless &%rcpt_max%& is 1, the appendfile, pipe or lmtp
+transport if &%batch_max%& is greater than 1)
+then information about Bcc recipients will be leaked.
+Doing so is generally not advised.
+
 
 .option event_action transports string&!! unset
 .cindex events
@@ -21507,15 +22504,19 @@ checked, since this option does not automatically suppress them.
 .option headers_remove transports list&!! unset
 .cindex "header lines" "removing"
 .cindex "transport" "header lines; removing"
-This option specifies a list of header names,
-colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&);
-these headers are omitted from the message as it is transported, as described
-in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
-routers.
+This option specifies a list of text headers,
+colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
+to be removed from the message.
+However, the option has no effect when an address is just being verified.
 Each list item is separately expanded.
 If the result of the expansion is an empty string, or if the expansion
 is forced to fail, no action is taken. Other expansion failures are treated as
 errors and cause the delivery to be deferred.
+If an item ends in *, it will match any header with the given prefix.
+
+Matching headers are omitted from the message as it is transported, as described
+in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
+routers.
 
 Unlike most options, &%headers_remove%& can be specified multiple times
 for a transport; all listed headers are removed.
@@ -21659,6 +22660,7 @@ on a remote transport in the current implementation.
 
 .option return_path transports string&!! unset
 .cindex "envelope sender"
+.cindex "envelope from"
 .cindex "transport" "return path; changing"
 .cindex "return path" "changing in transport"
 If this option is set, the string is expanded at transport time and replaces
@@ -21689,7 +22691,7 @@ This defaults to the incoming sender address, but can be changed by setting
 
 
 .option return_path_add transports boolean false
-.cindex "&'Return-path:'& header line"
+.chindex Return-path:
 If this option is true, a &'Return-path:'& header is added to the message.
 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
@@ -21775,7 +22777,7 @@ message. For example, a content scan could insert a new header line containing
 a spam score. This could be interpreted by a filter in the user's MUA. It is
 not possible to discard a message at this stage.
 
-.cindex "SMTP" "SIZE"
+.cindex "SIZE" "ESMTP extension"
 A problem might arise if the filter increases the size of a message that is
 being sent down an SMTP connection. If the receiving SMTP server has indicated
 support for the SIZE parameter, Exim will have sent the size of the message
@@ -22065,6 +23067,17 @@ If &%file%& or &%directory%& is set for a delivery from a redirection, it is
 used to determine the file or directory name for the delivery. Normally, the
 contents of &$address_file$& are used in some way in the string expansion.
 .endlist
+If the &%create_file%& option is set to a path which
+matches (see the option definition below for details)
+a file or directory name
+for the delivery, that name becomes de-tainted.
+
+.cindex "tainted data" "in filenames"
+.cindex appendfile "tainted data"
+Tainted data may not be used for a file or directory name.
+This means that, for instance, &$local_part$& cannot be used directly
+as a component of a path.  It can however be used as the key for a lookup
+which returns a path (or component).
 
 
 .cindex "Sieve filter" "configuring &(appendfile)&"
@@ -22087,7 +23100,7 @@ is used as a result of a &"keep"& action in the filter. This example shows one
 way of handling this requirement:
 .code
 file = ${if eq{$address_file}{inbox} \
-            {/var/mail/$local_part} \
+            {/var/mail/$local_part_data} \
             {${if eq{${substr_0_1:$address_file}}{/} \
                   {$address_file} \
                   {$home/mail/$address_file} \
@@ -22207,13 +23220,29 @@ delivery, it applies to the top level directory, not the maildir directories
 beneath.
 
 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
-&"belowhome"&. In the second and third cases, a home directory must have been
-set for the transport. This option is not useful when an explicit filename is
+&"belowhome"&, or to an absolute path.
+
+In the second and third cases, a home directory must have been
+set for the transport, and the file or directory being created must
+reside within it.
+The "belowhome" checking additionally checks for attempts to use "../"
+to evade the testing.
+This option is not useful when an explicit filename is
 given for normal mailbox deliveries. It is intended for the case when filenames
 are generated from users' &_.forward_& files. These are usually handled
 by an &(appendfile)& transport called &%address_file%&. See also
 &%file_must_exist%&.
 
+In the fourth case,
+the value given for this option must be an absolute path for an
+existing directory.
+The value is used for checking instead of a home directory;
+checking is done in "belowhome" mode.
+
+.cindex "tainted data" "de-tainting"
+If "belowhome" checking is used, the file or directory path
+becomes de-tainted.
+
 
 .option directory appendfile string&!! unset
 This option is mutually exclusive with the &%file%& option, but one of &%file%&
@@ -22226,6 +23255,9 @@ appended to a single mailbox file. A number of different formats are provided
 (see &%maildir_format%& and &%mailstore_format%&), and see section
 &<<SECTopdir>>& for further details of this form of delivery.
 
+The result of expansion must not be tainted, unless the &%create_file%& option
+specifies a path.
+
 
 .option directory_file appendfile string&!! "see below"
 .cindex "base62"
@@ -22258,6 +23290,9 @@ specifies a single file, to which the message is appended. One or more of
 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
 &%file%&.
 
+The result of expansion must not be tainted, unless the &%create_file%& option
+specifies a path.
+
 .cindex "NFS" "lock file"
 .cindex "locking files"
 .cindex "lock files"
@@ -22268,8 +23303,8 @@ The string value is expanded for each delivery, and must yield an absolute
 path. The most common settings of this option are variations on one of these
 examples:
 .code
-file = /var/spool/mail/$local_part
-file = /home/$local_part/inbox
+file = /var/spool/mail/$local_part_data
+file = /home/$local_part_data/inbox
 file = $home/inbox
 .endd
 .cindex "&""sticky""& bit"
@@ -22653,6 +23688,13 @@ sometimes add other information onto the ends of message filenames.
 
 Section &<<SECID136>>& contains further information.
 
+This option should not be used when other message-handling software
+may duplicate messages by making hardlinks to the files.  When that is done Exim
+will count the message size once for each filename, in contrast with the actual
+disk usage.  When the option is not set, calculating total usage requires
+a system-call per file to get the size; the number of links is then available also
+as is used to adjust the effective size.
+
 
 .option quota_warn_message appendfile string&!! "see below"
 See below for the use of this option. If it is not set when
@@ -22705,6 +23747,7 @@ percentage.
 
 
 .option use_bsmtp appendfile boolean false
+.cindex "envelope from"
 .cindex "envelope sender"
 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
 format, with the envelope sender and recipient(s) included as SMTP commands. If
@@ -23017,7 +24060,7 @@ and directories in a maildir mailbox, including subdirectories for maildir++
 folders. Consider this example:
 .code
 maildir_format = true
-directory = /var/mail/$local_part\
+directory = /var/mail/$local_part_data\
            ${if eq{$local_part_suffix}{}{}\
            {/.${substr_1:$local_part_suffix}}}
 maildirfolder_create_regex = /\.[^/]+$
@@ -23494,6 +24537,10 @@ directories are also controllable. See chapter &<<CHAPenvironment>>& for
 details of the local delivery environment and chapter &<<CHAPbatching>>&
 for a discussion of local delivery batching.
 
+.cindex "tainted data" "in pipe command"
+.cindex pipe "tainted data"
+Tainted data may not be used for the command name.
+
 
 .section "Concurrent delivery" "SECID140"
 If two messages arrive at almost the same time, and both are routed to a pipe
@@ -23581,14 +24628,15 @@ command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
 .cindex "filter" "transport filter"
 .vindex "&$pipe_addresses$&"
 Special handling takes place when an argument consists of precisely the text
-&`$pipe_addresses`&. This is not a general expansion variable; the only
+&`$pipe_addresses`& (no quotes).
+This is not a general expansion variable; the only
 place this string is recognized is when it appears as an argument for a pipe or
 transport filter command. It causes each address that is being handled to be
 inserted in the argument list at that point &'as a separate argument'&. This
 avoids any problems with spaces or shell metacharacters, and is of use when a
 &(pipe)& transport is handling groups of addresses in a batch.
 
-If &%force_command%& is enabled on the transport, Special handling takes place
+If &%force_command%& is enabled on the transport, special handling takes place
 for an argument that consists of precisely the text &`$address_pipe`&.  It
 is handled similarly to &$pipe_addresses$& above.  It is expanded and each
 argument is inserted in the argument list at that point
@@ -24000,14 +25048,14 @@ configuration for &%procmail%&:
 # transport
 procmail_pipe:
   driver = pipe
-  command = /usr/local/bin/procmail -d $local_part
+  command = /usr/local/bin/procmail -d $local_part_data
   return_path_add
   delivery_date_add
   envelope_to_add
   check_string = "From "
   escape_string = ">From "
   umask = 077
-  user = $local_part
+  user = $local_part_data
   group = mail
 
 # router
@@ -24198,12 +25246,14 @@ authenticated as a client.
 
 
 .option command_timeout smtp time 5m
+.cindex timeout "smtp transport command"
 This sets a timeout for receiving a response to an SMTP command that has been
 sent out. It is also used when waiting for the initial banner line from the
 remote host. Its value must not be zero.
 
 
 .option connect_timeout smtp time 5m
+.cindex timeout "smtp transport connect"
 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
 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
@@ -24239,21 +25289,30 @@ be treated as unset and &%tls_require_ciphers%& will be used instead.
 
 
 .option data_timeout smtp time 5m
+.cindex timeout "for transmitted SMTP data blocks"
 This sets a timeout for the transmission of each block in the data portion of
 the message. As a result, the overall timeout for a message depends on the size
 of the message. Its value must not be zero. See also &%final_timeout%&.
 
 
 .option dkim_canon smtp string&!! unset
-.option dkim_domain smtp string list&!! unset
+DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.
+.option dkim_domain smtp "string list&!!" unset
+DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.
 .option dkim_hash smtp string&!! sha256
+DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.
 .option dkim_identity smtp string&!! unset
+DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.
 .option dkim_private_key smtp string&!! unset
+DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.
 .option dkim_selector smtp string&!! unset
+DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.
 .option dkim_strict smtp string&!! unset
+DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.
 .option dkim_sign_headers smtp string&!! "per RFC"
+DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.
 .option dkim_timestamps smtp string&!! unset
-DKIM signing options.  For details see section &<<SECDKIMSIGN>>&.
+DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.
 
 
 .option delay_after_cutoff smtp boolean true
@@ -24295,14 +25354,15 @@ See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
 details.
 
 
-.option dnssec_request_domains smtp "domain list&!!" unset
+.option dnssec_request_domains smtp "domain list&!!" *
 .cindex "MX record" "security"
 .cindex "DNSSEC" "MX lookup"
 .cindex "security" "MX lookup"
 .cindex "DNS" "DNSSEC"
 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
-the dnssec request bit set.
-This applies to all of the SRV, MX, AAAA, A lookup sequence.
+the DNSSEC request bit set. Setting this transport option is only useful if the
+transport overrides or sets the host names. See the &%dnssec_request_domains%&
+router option.
 
 
 
@@ -24312,9 +25372,9 @@ This applies to all of the SRV, MX, AAAA, A lookup sequence.
 .cindex "security" "MX lookup"
 .cindex "DNS" "DNSSEC"
 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
-the dnssec request bit set.  Any returns not having the Authenticated Data bit
-(AD bit) set will be ignored and logged as a host-lookup failure.
-This applies to all of the SRV, MX, AAAA, A lookup sequence.
+the DNSSEC request bit set.  Setting this transport option is only
+useful if the transport overrides or sets the host names. See the
+&%dnssec_require_domains%& router option.
 
 
 
@@ -24368,6 +25428,7 @@ fails"& facility.
 
 
 .option final_timeout smtp time 10m
+.cindex timeout "for transmitted SMTP data accept"
 This is the timeout that applies while waiting for the response to the final
 line containing just &"."& that terminates a message. Its value must not be
 zero.
@@ -24456,9 +25517,34 @@ facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
 
 .option hosts_avoid_pipelining smtp "host list&!!" unset
 .cindex "PIPELINING" "avoiding the use of"
-Exim will not use the SMTP PIPELINING extension when delivering to any host
+.cindex "ESMTP extensions" PIPELINING
+Exim will not use the ESMTP PIPELINING extension when delivering to any host
 that matches this list, even if the server host advertises PIPELINING support.
 
+.option hosts_pipe_connect smtp "host list&!!" unset
+.cindex "pipelining" "early connection"
+.cindex "pipelining" PIPE_CONNECT
+If Exim is built with the SUPPORT_PIPE_CONNECT build option
+this option controls which to hosts the facility watched for
+and recorded, and used for subsequent connections.
+
+The retry hints database is used for the record,
+and records are subject to the &%retry_data_expire%& option.
+When used, the pipelining saves on roundtrip times.
+It also turns SMTP into a client-first protocol
+so combines well with TCP Fast Open.
+
+See also the &%pipelining_connect_advertise_hosts%& main option.
+
+Note:
+When the facility is used, the transport &%helo_data%& option
+will be expanded before the &$sending_ip_address$& variable
+is filled in.
+A check is made for the use of that variable, without the
+presence of a &"def:"& test on it, but suitably complex coding
+can avoid the check and produce unexpected results.
+You have been warned.
+
 
 .option hosts_avoid_tls smtp "host list&!!" unset
 .cindex "TLS" "avoiding for certain hosts"
@@ -24498,7 +25584,7 @@ been started will not be passed to a new delivery process for sending another
 message on the same connection. See section &<<SECTmulmessam>>& for an
 explanation of when this might be needed.
 
-.option hosts_noproxy_tls smtp "host list&!!" *
+.option hosts_noproxy_tls smtp "host list&!!" unset
 .cindex "TLS" "passing connection"
 .cindex "multiple SMTP deliveries"
 .cindex "TLS" "multiple message deliveries"
@@ -24562,6 +25648,18 @@ Exim will request a Certificate Status on a
 TLS session for any host that matches this list.
 &%tls_verify_certificates%& should also be set for the transport.
 
+.option hosts_require_alpn smtp "host list&!!" unset
+.cindex ALPN "require negotiation in client"
+.cindex TLS ALPN
+.cindex TLS "Application Layer Protocol Names"
+If the TLS library supports ALPN
+then a successful negotiation of ALPN will be required for any host
+matching the list, for TLS to be used.
+See also the &%tls_alpn%& option.
+
+&*Note*&: prevention of fallback to in-clear connection is not
+managed by this option; see &%hosts_require_tls%&.
+
 .option hosts_require_dane smtp "host list&!!" unset
 .cindex DANE "transport options"
 .cindex DANE "requiring for certain servers"
@@ -24569,8 +25667,14 @@ If built with DANE support, Exim  will require that a DNSSEC-validated
 TLSA record is present for any host matching the list,
 and that a DANE-verified TLS connection is made.
 There will be no fallback to in-clear communication.
+See the &%dnssec_request_domains%& router and transport options.
 See section &<<SECDANE>>&.
 
+.option hosts_require_helo smtp "host list&!!" *
+.cindex "HELO/EHLO" requiring
+Exim will require an accepted HELO or EHLO command from a host matching
+this list, before accepting a MAIL command.
+
 .option hosts_require_ocsp smtp "host list&!!" unset
 .cindex "TLS" "requiring for certain servers"
 Exim will request, and check for a valid Certificate Status being given, on a
@@ -24588,9 +25692,10 @@ incoming messages, use an appropriate ACL.
 .cindex "authentication" "optional in client"
 This option provides a list of servers to which, provided they announce
 authentication support, Exim will attempt to authenticate as a client when it
-connects. If authentication fails, Exim will try to transfer the message
-unauthenticated. See also &%hosts_require_auth%&, and chapter
-&<<CHAPSMTPAUTH>>& for details of authentication.
+connects. If authentication fails
+and &%hosts_require_auth%& permits,
+Exim will try to transfer the message unauthenticated.
+See also chapter &<<CHAPSMTPAUTH>>& for details of authentication.
 
 .option hosts_try_chunking smtp "host list&!!" *
 .cindex CHUNKING "enabling, in client"
@@ -24598,19 +25703,21 @@ unauthenticated. See also &%hosts_require_auth%&, and chapter
 .cindex "RFC 3030" "CHUNKING"
 This option provides a list of servers to which, provided they announce
 CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
+Unless DKIM signing is being done,
 BDAT will not be used in conjunction with a transport filter.
 
-.option hosts_try_dane smtp "host list&!!" unset
+.option hosts_try_dane smtp "host list&!!" *
 .cindex DANE "transport options"
 .cindex DANE "attempting for certain servers"
-If built with DANE support, Exim  will lookup a
-TLSA record for any host matching the list.
-If found and verified by DNSSEC,
-a DANE-verified TLS connection is made to that host;
+If built with DANE support, Exim  will look up a
+TLSA record for any host matching the list,
+If one is found and that lookup was DNSSEC-validated,
+then Exim requires that a DANE-verified TLS connection is made for that host;
 there will be no fallback to in-clear communication.
+See the &%dnssec_request_domains%& router and transport options.
 See section &<<SECDANE>>&.
 
-.option hosts_try_fastopen smtp "host list&!!" unset
+.option hosts_try_fastopen smtp "host list&!!" *
 .cindex "fast open, TCP" "enabling, in client"
 .cindex "TCP Fast Open" "enabling, in client"
 .cindex "RFC 7413" "TCP Fast Open"
@@ -24632,6 +25739,7 @@ such as DNSBL lookups, will still delay the emission of the SMTP banner.
 
 .option hosts_try_prdr smtp "host list&!!" *
 .cindex "PRDR" "enabling, optional in client"
+.cindex "ESMTP extensions" PRDR
 This option provides a list of servers to which, provided they announce
 PRDR support, Exim will attempt to negotiate PRDR
 for multi-recipient messages.
@@ -24691,7 +25799,19 @@ has advertised support for IGNOREQUOTA in its response to the LHLO command.
 This option limits the number of RCPT commands that are sent in a single
 SMTP message transaction. Each set of addresses is treated independently, and
 so can cause parallel connections to the same host if &%remote_max_parallel%&
-permits this.
+permits this. A value setting of zero disables the limit.
+
+
+.option message_linelength_limit smtp integer 998
+.cindex "line length" limit
+This option sets the maximum line length, in bytes, that the transport
+will send.  Any messages with lines exceeding the given value
+will fail and a failure-DSN ("bounce") message will if possible be returned
+to the sender.
+The default value is that defined by the SMTP standards.
+
+It is generally wise to also check in the data ACL so that messages
+received via SMTP can be refused without producing a bounce.
 
 
 .option multi_domain smtp boolean&!! true
@@ -24707,6 +25827,10 @@ It is expanded per-address and can depend on any of
 &$address_data$&, &$domain_data$&, &$local_part_data$&,
 &$host$&, &$host_address$& and &$host_port$&.
 
+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.
+
 .option port smtp string&!! "see below"
 .cindex "port" "sending TCP/IP"
 .cindex "TCP/IP" "setting outgoing port"
@@ -24724,10 +25848,8 @@ and if &%protocol%& is set to &"smtps"& the default is &"smtps"&.
 If the expansion fails, or if a port number cannot be found, delivery
 is deferred.
 
-.new
 Note that at least one Linux distribution has been seen failing
 to put &"smtps"& in its &"/etc/services"& file, resulting is such deferrals.
-.wen
 
 
 
@@ -24745,11 +25867,9 @@ over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
 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.
-.new
 The Internet standards bodies used to strongly discourage use of this mode,
-but as of RFC 8314 it is perferred over STARTTLS for message submission
+but as of RFC 8314 it is preferred over STARTTLS for message submission
 (as distinct from MTA-MTA communication).
-.wen
 
 
 .option retry_include_ip_address smtp boolean&!! true
@@ -24793,7 +25913,7 @@ See also the &%max_parallel%& generic transport option.
 
 
 .option size_addition smtp integer 1024
-.cindex "SMTP" "SIZE"
+.cindex "SIZE" "ESMTP extension"
 .cindex "message" "size issue for transport filter"
 .cindex "size" "of message"
 .cindex "transport" "filter"
@@ -24815,6 +25935,19 @@ This option enables use of SOCKS proxies for connections made by the
 transport.  For details see section &<<SECTproxySOCKS>>&.
 
 
+.option tls_alpn smtp string&!! unset
+.cindex TLS "Application Layer Protocol Names"
+.cindex TLS ALPN
+.cindex ALPN "set name in client"
+If this option is set
+and the TLS library supports ALPN,
+the value given is used.
+
+As of writing no value has been standardised for email use.
+The authors suggest using &"smtp"&.
+
+
+
 .option tls_certificate smtp string&!! unset
 .cindex "TLS" "client certificate, location of"
 .cindex "certificate" "client, location of"
@@ -24879,11 +26012,21 @@ is used in different ways by OpenSSL and GnuTLS (see sections
 ciphers is a preference order.
 
 
+.option tls_resumption_hosts smtp "host list&!!" unset
+.cindex TLS resumption
+This option controls which connections to use the TLS resumption feature.
+See &<<SECTresumption>>& for details.
+
+
 
 .option tls_sni smtp string&!! unset
 .cindex "TLS" "Server Name Indication"
+.cindex "TLS" SNI
+.cindex SNI "setting in client"
 .vindex "&$tls_sni$&"
-If this option is set then it sets the $tls_out_sni variable and causes any
+If this option is set
+and the connection is not DANE-validated
+then it sets the $tls_out_sni variable and causes any
 TLS session to pass this value as the Server Name Indication extension to
 the remote side, which can be used by the remote side to select an appropriate
 certificate and private key for the session.
@@ -24977,16 +26120,22 @@ certificate verification must succeed.
 The &%tls_verify_certificates%& option must also be set.
 If both this option and &%tls_try_verify_hosts%& are unset
 operation is as if this option selected all hosts.
+&*Warning*&: Including a host in &%tls_verify_hosts%& does not require
+that connections use TLS.
+Fallback to in-clear communication will be done unless restricted by 
+the &%hosts_require_tls%& option.
 
-.new
-.option utf8_downconvert smtp integer!! unset
+.option utf8_downconvert smtp integer&!! -1
 .cindex utf8 "address downconversion"
 .cindex i18n "utf8 address downconversion"
 If built with internationalization support,
-this option controls conversion of UTF-8 in message addresses
+this option controls conversion of UTF-8 in message envelope addresses
 to a-label form.
-For details see section &<<SECTi18nMTA>>&.
-.wen
+If, after expansion, the value is 1, 0, or -1 then this value overrides
+any value previously set for the message.  Otherwise, any previously
+set value is used.  To permit use of a previous value,
+set this option to an empty string.
+For details on the values see section &<<SECTi18nMTA>>&.
 
 
 
@@ -25179,6 +26328,7 @@ When an address is being routed, either for delivery or for verification,
 rewriting is applied immediately to child addresses that are generated by
 redirection, unless &%no_rewrite%& is set on the router.
 
+.cindex "envelope from"
 .cindex "envelope sender" "rewriting at transport time"
 .cindex "rewriting" "at transport time"
 .cindex "header lines" "rewriting at transport time"
@@ -26092,7 +27242,12 @@ 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
 other.
 
+The name of an authenticator is limited to be &drivernamemax; ASCII characters long;
+prior to Exim 4.95 names would be silently truncated at this length, but now
+it is enforced.
+
 .cindex "AUTH" "description of"
+.cindex "ESMTP extensions" AUTH
 Very briefly, the way SMTP authentication works is as follows:
 
 .ilist
@@ -26147,6 +27302,7 @@ included by setting
 AUTH_CRAM_MD5=yes
 AUTH_CYRUS_SASL=yes
 AUTH_DOVECOT=yes
+AUTH_EXTERNAL=yes
 AUTH_GSASL=yes
 AUTH_HEIMDAL_GSSAPI=yes
 AUTH_PLAINTEXT=yes
@@ -26158,15 +27314,18 @@ authentication mechanism (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 an interface to the GNU SASL authentication library, which
+The fourth provides for negotiation of authentication done via non-SMTP means,
+as defined by RFC 4422 Appendix A.
+The fifth provides an interface to the GNU SASL authentication library, which
 provides mechanisms but typically not data sources.
-The fifth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
+The sixth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
 supporting setting a server keytab.
-The sixth can be configured to support
+The seventh can be configured to support
 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
-not formally documented, but used by several MUAs. The seventh authenticator
+not formally documented, but used by several MUAs.
+The eighth authenticator
 supports Microsoft's &'Secure Password Authentication'& mechanism.
-The eighth is an Exim authenticator but not an SMTP one;
+The last is an Exim authenticator but not an SMTP one;
 instead it can use information from a TLS negotiation.
 
 The authenticators are configured using the same syntax as other drivers (see
@@ -26379,7 +27538,7 @@ conditions:
 .ilist
 The client host must match &%auth_advertise_hosts%& (default *).
 .next
-It the &%server_advertise_condition%& option is set, its expansion must not
+If the &%server_advertise_condition%& option is set, its expansion must not
 yield the empty string, &"0"&, &"no"&, or &"false"&.
 .endlist
 
@@ -26445,7 +27604,7 @@ no successful authentication.
 
 .cindex authentication "expansion item"
 Successful authentication sets up information used by the
-&$authresults$& expansion item.
+&%authresults%& expansion item.
 
 
 
@@ -26487,7 +27646,7 @@ encode '\0user@domain.com\0pas$$word'
 .endd
 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
 
-If you have the &%mimencode%& command installed, another way to do produce
+If you have the &%mimencode%& command installed, another way to produce
 base64-encoded strings is to run the command
 .code
 echo -e -n `\0user\0password' | mimencode
@@ -26581,7 +27740,19 @@ security risk; you are strongly advised to insist on the use of SMTP encryption
 use unencrypted plain text, you should not use the same passwords for SMTP
 connections as you do for login accounts.
 
-.section "Plaintext options" "SECID171"
+.section "Avoiding cleartext use" "SECTplain_TLS"
+The following generic option settings will disable &(plaintext)& authenticators when
+TLS is not being used:
+.code
+  server_advertise_condition = ${if def:tls_in_cipher }
+  client_condition =           ${if def:tls_out_cipher}
+.endd
+
+&*Note*&: a plaintext SMTP AUTH done inside TLS is not vulnerable to casual snooping,
+but is still vulnerable to a Man In The Middle attack unless certificates
+(including their names) have been properly verified.
+
+.section "Plaintext server options" "SECID171"
 .cindex "options" "&(plaintext)& authenticator (server)"
 When configured as a server, &(plaintext)& uses the following options:
 
@@ -26589,7 +27760,7 @@ When configured as a server, &(plaintext)& uses the following options:
 This is actually a global authentication option, but it must be set in order to
 configure the &(plaintext)& driver as a server. Its use is described below.
 
-.option server_prompts plaintext string&!! unset
+.option server_prompts plaintext "string list&!!" unset
 The contents of this option, after expansion, must be a colon-separated list of
 prompt strings. If expansion fails, a temporary authentication rejection is
 given.
@@ -26638,7 +27809,7 @@ There are good and bad examples at the end of the next section.
 
 .section "The PLAIN authentication mechanism" "SECID172"
 .cindex "PLAIN authentication mechanism"
-.cindex "authentication" "PLAIN mechanism"
+.cindex authentication PLAIN
 .cindex "binary zero" "in &(plaintext)& authenticator"
 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
 sent as one item of data (that is, one combined string containing two NUL
@@ -26720,7 +27891,7 @@ writing the test makes the logic clearer.
 
 .section "The LOGIN authentication mechanism" "SECID173"
 .cindex "LOGIN authentication mechanism"
-.cindex "authentication" "LOGIN mechanism"
+.cindex authentication LOGIN
 The LOGIN authentication mechanism is not documented in any RFC, but is in use
 in a number of programs. No data is sent with the AUTH command. Instead, a
 user name and password are supplied separately, in response to prompts. The
@@ -26817,7 +27988,12 @@ fixed_plain:
   client_send = ^username^mysecret
 .endd
 The lack of colons means that the entire text is sent with the AUTH
-command, with the circumflex characters converted to NULs. A similar example
+command, with the circumflex characters converted to NULs.
+Note that due to the ambiguity of parsing three consectutive circumflex characters
+there is no way to provide a password having a leading circumflex.
+
+
+A similar example
 that uses the LOGIN mechanism is:
 .code
 fixed_login:
@@ -26841,7 +28017,7 @@ prompts.
 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
 .cindex "CRAM-MD5 authentication mechanism"
-.cindex "authentication" "CRAM-MD5 mechanism"
+.cindex authentication CRAM-MD5
 The CRAM-MD5 authentication mechanism is described in 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
@@ -27059,7 +28235,7 @@ but it is present in many binary distributions.
 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
 This authenticator is an interface to the authentication facility of the
-Dovecot POP/IMAP server, which can support a number of authentication methods.
+Dovecot 2 POP/IMAP server, which can support a number of authentication methods.
 Note that Dovecot must be configured to use auth-client not auth-userdb.
 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
 to use the same mechanisms for SMTP authentication. This is a server
@@ -27090,6 +28266,27 @@ option is passed in the Dovecot authentication command. If, for a TLS
 connection, a client certificate has been verified, the &"valid-client-cert"&
 option is passed. When authentication succeeds, the identity of the user
 who authenticated is placed in &$auth1$&.
+
+The Dovecot configuration to match the above will look
+something like:
+.code
+conf.d/10-master.conf :-
+
+service auth {
+...
+#SASL
+  unix_listener auth-client {
+    mode = 0660
+    user = mail
+  }
+...
+}
+
+conf.d/10-auth.conf :-
+
+auth_mechanisms = plain login ntlm
+.endd
+
 .ecindex IIDdcotauth1
 .ecindex IIDdcotauth2
 
@@ -27107,21 +28304,76 @@ who authenticated is placed in &$auth1$&.
 .cindex "authentication" "LOGIN"
 .cindex "authentication" "DIGEST-MD5"
 .cindex "authentication" "CRAM-MD5"
-.cindex "authentication" "SCRAM-SHA-1"
-The &(gsasl)& authenticator provides server integration for the GNU SASL
+.cindex "authentication" "SCRAM family"
+The &(gsasl)& authenticator provides integration for the GNU SASL
 library and the mechanisms it provides.  This is new as of the 4.80 release
 and there are a few areas where the library does not let Exim smoothly
 scale to handle future authentication mechanisms, so no guarantee can be
 made that any particular new authentication mechanism will be supported
 without code changes in Exim.
 
-Exim's &(gsasl)& authenticator does not have client-side support at this
-time; only the server-side support is implemented.  Patches welcome.
+The library is expected to add support in an upcoming
+realease for the SCRAM-SHA-256 method.
+The macro _HAVE_AUTH_GSASL_SCRAM_SHA_256 will be defined
+when this happens.
 
+To see the list of mechanisms supported by the library run Exim with "auth" debug
+enabled and look for a line containing "GNU SASL supports".
+Note however that some may not have been tested from Exim.
 
-.option server_channelbinding gsasl boolean false
-Do not set this true without consulting a cryptographic engineer.
 
+.option client_authz gsasl string&!! unset
+This option can be used to supply an &'authorization id'&
+which is different to the &'authentication_id'& provided
+by &%client_username%& option.
+If unset or (after expansion) empty it is not used,
+which is the common case.
+
+.option client_channelbinding gsasl boolean false
+See &%server_channelbinding%& below.
+
+.option client_password gsasl string&!! unset
+This option is exapanded before use, and should result in
+the password to be used, in clear.
+
+.option client_username gsasl string&!! unset
+This option is exapanded before use, and should result in
+the account name to be used.
+
+
+.option client_spassword gsasl string&!! unset
+This option is only supported for library versions 1.9.1 and greater.
+The macro _HAVE_AUTH_GSASL_SCRAM_S_KEY will be defined when this is so.
+
+If a SCRAM mechanism is being used and this option is set
+and correctly sized
+it is used in preference to &%client_password%&.
+The value after expansion should be
+a 40 (for SHA-1) or 64 (for SHA-256) character string
+with the PBKDF2-prepared password, hex-encoded.
+
+Note that this value will depend on the salt and iteration-count
+supplied by the server.
+The option is expanded before use.
+During the expansion &$auth1$& is set with the client username,
+&$auth2$& with the iteration count, and
+&$auth3$& with the salt.
+
+The intent of this option
+is to support clients that can cache thes salted password
+to save on recalculation costs.
+The cache lookup should return an unusable value
+(eg. an empty string)
+if the salt or iteration count has changed
+
+If the authentication succeeds then the above variables are set,
+.vindex "&$auth4$&"
+plus the calculated salted password value value in &$auth4$&,
+during the expansion of the &%client_set_id%& option.
+A side-effect of this expansion can be used to prime the cache.
+
+
+.option server_channelbinding gsasl boolean false
 Some authentication mechanisms are able to use external context at both ends
 of the session to bind the authentication to that context, and fail the
 authentication process if that context differs.  Specifically, some TLS
@@ -27132,17 +28384,23 @@ This should have meant that certificate identity and verification becomes a
 non-issue, as a man-in-the-middle attack will cause the correct client and
 server to see different identifiers and authentication will fail.
 
-This is currently only supported when using the GnuTLS library.  This is
+This is
 only usable by mechanisms which support "channel binding"; at time of
 writing, that's the SCRAM family.
+When using this feature the "-PLUS" variants of the method names need to be used.
 
 This defaults off to ensure smooth upgrade across Exim releases, in case
 this option causes some clients to start failing.  Some future release
 of Exim might have switched the default to be true.
 
-However, Channel Binding in TLS has proven to be broken in current versions.
-Do not plan to rely upon this feature for security, ever, without consulting
-with a subject matter expert (a cryptographic engineer).
+. However, Channel Binding in TLS has proven to be vulnerable in current versions.
+. Do not plan to rely upon this feature for security, ever, without consulting
+. with a subject matter expert (a cryptographic engineer).
+
+This option was deprecated in previous releases due to doubts over
+the "Triple Handshake" vulnerability.
+Exim takes suitable precausions (requiring Extended Master Secret if TLS
+Session Resumption was used) for safety.
 
 
 .option server_hostname gsasl string&!! "see below"
@@ -27188,16 +28446,54 @@ This specifies the SASL realm that the server claims to be in.
 Some mechanisms will use this data.
 
 
-.option server_scram_iter gsasl string&!! unset
+.option server_scram_iter gsasl string&!! 4096
 This option provides data for the SCRAM family of mechanisms.
-&$auth1$& is not available at evaluation time.
-(This may change, as we receive feedback on use)
+The &$auth1$&, &$auth2$& and &$auth3$& variables are available
+when this option is expanded.
 
+The result of expansion should be a decimal number,
+and represents both a lower-bound on the security, and
+a compute cost factor imposed on the client
+(if it does not cache results, or the server changes
+either the iteration count or the salt).
+A minimum value of 4096 is required by the standards
+for all current SCRAM mechanism variants.
 
 .option server_scram_salt gsasl string&!! unset
 This option provides data for the SCRAM family of mechanisms.
-&$auth1$& is not available at evaluation time.
-(This may change, as we receive feedback on use)
+The &$auth1$&, &$auth2$& and &$auth3$& variables are available
+when this option is expanded.
+The value should be a base64-encoded string,
+of random data typically 4-to-16 bytes long.
+If unset or empty after expansion the library will provides a value for the
+protocol conversation.
+
+
+.option server_key gsasl string&!! unset
+.option server_skey gsasl string&!! unset
+These options can be used for the SCRAM family of mechanisms
+to provide stored information related to a password,
+the storage of which is preferable to plaintext.
+
+&%server_key%& is the value defined in the SCRAM standards as ServerKey;
+&%server_skey%& is StoredKey.
+
+They are only available for version 1.9.0 (or later) of the gsasl library.
+When this is so, the macros
+_OPT_AUTHENTICATOR_GSASL_SERVER_KEY
+and _HAVE_AUTH_GSASL_SCRAM_S_KEY
+will be defined.
+
+The &$authN$& variables are available when these options are expanded.
+
+If set, the results of expansion should for each
+should be a 28 (for SHA-1) or 44 (for SHA-256) character string
+of base64-coded data, and will be used in preference to the
+&%server_password%& option.
+If unset or not of the right length, &%server_password%& will be used.
+
+The libgsasl library release includes a utility &'gsasl'& which can be used
+to generate these values.
 
 
 .option server_service gsasl string &`smtp`&
@@ -27401,6 +28697,142 @@ msn:
 
 
 
+. ////////////////////////////////////////////////////////////////////////////
+. ////////////////////////////////////////////////////////////////////////////
+
+.chapter "The external authenticator" "CHAPexternauth"
+.scindex IIDexternauth1 "&(external)& authenticator"
+.scindex IIDexternauth2 "authenticators" "&(external)&"
+.cindex "authentication" "Client Certificate"
+.cindex "authentication" "X509"
+.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)).
+It is only a transport and negotiation mechanism;
+the process of authentication is entirely controlled
+by the server configuration.
+
+The client presents an identity in-clear.
+It is probably wise for a server to only advertise,
+and for clients to only attempt,
+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/)),
+is for using X509 client certificates.
+
+It thus overlaps in function with the TLS authenticator
+(see &<<CHAPtlsauth>>&)
+but is a full SMTP SASL authenticator
+rather than being implicit for TLS-connection carried
+client certificates only.
+
+The examples and discussion in this chapter assume that
+client-certificate authentication is being done.
+
+The client must present a certificate,
+for which it must have been requested via the
+&%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
+(see &<<CHAPTLS>>&).
+For authentication to be effective the certificate should be
+verifiable against a trust-anchor certificate known to the server.
+
+.section "External options" "SECTexternsoptions"
+.cindex "options" "&(external)& authenticator (server)"
+The &(external)& authenticator has two server options:
+
+.option server_param2 external string&!! unset
+.option server_param3 external string&!! unset
+.cindex "variables (&$auth1$& &$auth2$& etc)" "in &(external)& authenticator"
+These options are expanded before the &%server_condition%& option
+and the result are placed in &$auth2$& and &$auth3$& resectively.
+If the expansion is forced to fail, authentication fails. Any other expansion
+failure causes a temporary error code to be returned.
+
+They can be used to clarify the coding of a complex &%server_condition%&.
+
+.section "Using external in a server" "SECTexternserver"
+.cindex "AUTH" "in &(external)& authenticator"
+.cindex "numerical variables (&$1$& &$2$& etc)" &&&
+        "in &(external)& authenticator"
+.vindex "&$auth1$&, &$auth2$&, etc"
+.cindex "base64 encoding" "in &(external)& authenticator"
+
+When running as a server, &(external)& performs the authentication test by
+expanding a string. The data sent by the client with the AUTH command, or in
+response to subsequent prompts, is base64 encoded, and so may contain any byte
+values when decoded. The decoded value is treated as
+an identity for authentication and
+placed in the expansion variable &$auth1$&.
+
+For compatibility with previous releases of Exim, the value is also placed in
+the expansion variable &$1$&. However, the use of this
+variable for this purpose is now deprecated, as it can lead to confusion in
+string expansions that also use them for other things.
+
+.vindex "&$authenticated_id$&"
+Once an identity has been received,
+&%server_condition%& is expanded. If the expansion is forced to fail,
+authentication fails. Any other expansion failure causes a temporary error code
+to be returned. If the result of a successful expansion is an empty string,
+&"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
+expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
+generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
+For any other result, a temporary error code is returned, with the expanded
+string as the error text.
+
+Example:
+.code
+ext_ccert_san_mail:
+  driver =            external
+  public_name =       EXTERNAL
+
+  server_advertise_condition = $tls_in_certificate_verified
+  server_param2 =     ${certextract {subj_altname,mail,>:} \
+                                    {$tls_in_peercert}}
+  server_condition =  ${if forany {$auth2} \
+                            {eq {$item}{$auth1}}}
+  server_set_id =     $auth1
+.endd
+This accepts a client certificate that is verifiable against any
+of your configured trust-anchors
+(which usually means the full set of public CAs)
+and which has a mail-SAN matching the claimed identity sent by the client.
+
+&*Note*&: up to TLS1.2, the client cert is on the wire in-clear, including the SAN.
+The account name is therefore guessable by an opponent.
+TLS 1.3 protects both server and client certificates, and is not vulnerable
+in this way.
+
+
+.section "Using external in a client" "SECTexternclient"
+.cindex "options" "&(external)& authenticator (client)"
+The &(external)& authenticator has one client option:
+
+.option client_send external string&!! unset
+This option is expanded and sent with the AUTH command as the
+identity being asserted.
+
+Example:
+.code
+ext_ccert:
+  driver =      external
+  public_name = EXTERNAL
+
+  client_condition = ${if !eq{$tls_out_cipher}{}}
+  client_send = myaccount@smarthost.example.net
+.endd
+
+
+.ecindex IIDexternauth1
+.ecindex IIDexternauth2
+
+
+
+
+
 . ////////////////////////////////////////////////////////////////////////////
 . ////////////////////////////////////////////////////////////////////////////
 
@@ -27585,16 +29017,19 @@ There is also a &%-tls-on-connect%& command line option. This overrides
 
 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
-The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
-followed later, when the first versions of GnuTLS were released. To build Exim
-to use GnuTLS, you need to set
+TLS is supported in Exim using either the OpenSSL or GnuTLS library.
+To build Exim to use OpenSSL you need to set
 .code
-USE_GNUTLS=yes
+USE_OPENSSL=yes
 .endd
-in Local/Makefile, in addition to
+in Local/Makefile.
+
+To build Exim to use GnuTLS, you need to set
 .code
-SUPPORT_TLS=yes
+USE_GNUTLS=yes
 .endd
+in Local/Makefile.
+
 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
 include files and libraries for GnuTLS can be found.
 
@@ -27638,6 +29073,10 @@ Some other recently added features may only be available in one or the other.
 This should be documented with the feature.  If the documentation does not
 explicitly state that the feature is infeasible in the other TLS
 implementation, then patches are welcome.
+.next
+The output from "exim -bV" will show which (if any) support was included
+in the build.
+Also, the macro "_HAVE_OPENSSL" or "_HAVE_GNUTLS" will be defined.
 .endlist
 
 
@@ -27729,9 +29168,7 @@ the size of the generated prime, so it might still be too large.
 .oindex "&%tls_require_ciphers%&" "OpenSSL"
 There is a function in the OpenSSL library that can be passed a list of cipher
 suites before the cipher negotiation takes place. This specifies which ciphers
-.new
 are acceptable for TLS versions prior to 1.3.
-.wen
 The list is colon separated and may contain names like
 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
 directly to this function call.
@@ -27797,7 +29234,6 @@ This example will prefer ECDSA-authenticated ciphers over RSA ones:
 tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT
 .endd
 
-.new
 For TLS version 1.3 the control available is less fine-grained
 and Exim does not provide access to it at present.
 The value of the &%tls_require_ciphers%& option is ignored when
@@ -27807,7 +29243,6 @@ As of writing the library default cipher suite list for TLSv1.3 is
 .code
 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
 .endd
-.wen
 
 
 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
@@ -27867,6 +29302,7 @@ tls_require_ciphers = ${if =={$received_port}{25}\
 
 .section "Configuring an Exim server to use TLS" "SECID182"
 .cindex "TLS" "configuring an Exim server"
+.cindex "ESMTP extensions" STARTTLS
 When Exim has been built with TLS support, it advertises the availability of
 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
 but not to any others. The default value of this option is *, which means
@@ -28114,9 +29550,62 @@ There is no current way to staple a proof for a client certificate.
 .endd
 
 
-
-
-.section "Configuring an Exim client to use TLS" "SECID185"
+.section "Caching of static server configuration items" "SECTserverTLScache"
+.cindex certificate caching
+.cindex privatekey caching
+.cindex crl caching
+.cindex ocsp caching
+.cindex ciphers caching
+.cindex "CA bundle" caching
+.cindex "certificate authorities" caching
+.cindex tls_certificate caching
+.cindex tls_privatekey caching
+.cindex tls_crl caching
+.cindex tls_ocsp_file caching
+.cindex tls_require_ciphers caching
+.cindex tls_verify_certificate caching
+.cindex caching certificate
+.cindex caching privatekey
+.cindex caching crl
+.cindex caching ocsp
+.cindex caching ciphers
+.cindex caching "certificate authorities
+If any of the main configuration options &%tls_certificate%&, &%tls_privatekey%&,
+&%tls_crl%& and &%tls_ocsp_file%& have values with no
+expandable elements,
+then the associated information is loaded at daemon startup.
+It is made available
+to child processes forked for handling received SMTP connections.
+
+This caching is currently only supported under Linux and FreeBSD.
+
+If caching is not possible, for example if an item has to be dependent
+on the peer host so contains a &$sender_host_name$& expansion, the load
+of the associated information is done at the startup of the TLS connection.
+
+The cache is invalidated and reloaded after any changes to the directories
+containing files specified by these options.
+
+The information specified by the main option &%tls_verify_certificates%&
+is similarly cached so long as it specifies files explicitly
+or (under GnuTLS) is the string &"system,cache"&.
+The latter case is not automatically invalidated;
+it is the operator's responsibility to arrange for a daemon restart
+any time the system certificate authority bundle is updated.
+A HUP signal is sufficient for this.
+The value &"system"& results in no caching under GnuTLS.
+
+The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
+is acceptable in configurations for the Exim executavble.
+
+Caching of the system Certificate Authorities bundle can
+save siginificant time and processing on every TLS connection
+accepted by Exim.
+
+
+
+
+.section "Configuring an Exim client to use TLS" "SECTclientTLS"
 .cindex "cipher" "logging"
 .cindex "log" "TLS cipher"
 .cindex "log" "distinguished name"
@@ -28126,6 +29615,7 @@ deliveries as well as to incoming, the latter one causing logging of the
 server certificate's DN. The remaining client configuration for TLS is all
 within the &(smtp)& transport.
 
+.cindex "ESMTP extensions" STARTTLS
 It is not necessary to set any options to have TLS work in the &(smtp)&
 transport. If Exim is built with TLS support, and TLS is advertised by a
 server, the &(smtp)& transport always tries to start a TLS session. However,
@@ -28153,9 +29643,17 @@ unencrypted.
 
 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
 transport provide the client with a certificate, which is passed to the server
-if it requests it. If the server is Exim, it will request a certificate only if
+if it requests it.
+This is an optional thing for TLS connections, although either end
+may insist on it.
+If the server is Exim, it will request a certificate only if
 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
 
+&*Note*&: Do not use a certificate which has the OCSP-must-staple extension,
+for client use (they are usable for server use).
+As the TLS protocol has no means for the client to staple before TLS 1.3 it will result
+in failed connections.
+
 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
 specifies a collection of expected server certificates.
 These may be
@@ -28173,8 +29671,12 @@ certificate verification to the listed servers.  Verification either must
 or need not succeed respectively.
 
 The &%tls_verify_cert_hostnames%& option lists hosts for which additional
-checks are made: that the host name (the one in the DNS A record)
-is valid for the certificate.
+name checks are made on the server certificate.
+The match against this list is, as per other Exim usage, the
+IP for the host.  That is most closely associated with the
+name on the DNS A (or AAAA) record for the host.
+However, the name that needs to be in the certificate
+is the one at the head of any CNAME chain leading to the A record.
 The option defaults to always checking.
 
 The &(smtp)& transport has two OCSP-related options:
@@ -28222,8 +29724,64 @@ outgoing connection.
 
 
 
+.section "Caching of static client configuration items" "SECTclientTLScache"
+.cindex certificate caching
+.cindex privatekey caching
+.cindex crl caching
+.cindex ciphers caching
+.cindex "CA bundle" caching
+.cindex "certificate authorities" caching
+.cindex tls_certificate caching
+.cindex tls_privatekey caching
+.cindex tls_crl caching
+.cindex tls_require_ciphers caching
+.cindex tls_verify_certificate caching
+.cindex caching certificate
+.cindex caching privatekey
+.cindex caching crl
+.cindex caching ciphers
+.cindex caching "certificate authorities
+If any of the transport configuration options &%tls_certificate%&, &%tls_privatekey%&
+and &%tls_crl%& have values with no
+expandable elements,
+then the associated information is loaded per smtp transport
+at daemon startup, at the start of a queue run, or on a
+command-line specified message delivery.
+It is made available
+to child processes forked for handling making SMTP connections.
+
+This caching is currently only supported under Linux.
+
+If caching is not possible, the load
+of the associated information is done at the startup of the TLS connection.
+
+The cache is invalidated in the daemon
+and reloaded after any changes to the directories
+containing files specified by these options.
+
+The information specified by the main option &%tls_verify_certificates%&
+is similarly cached so long as it specifies files explicitly
+or (under GnuTLS) is the string &"system,cache"&.
+The latter case is not automatically invaludated;
+it is the operator's responsibility to arrange for a daemon restart
+any time the system certificate authority bundle is updated.
+A HUP signal is sufficient for this.
+The value &"system"& results in no caching under GnuTLS.
+
+The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
+is acceptable in configurations for the Exim executavble.
+
+Caching of the system Certificate Authorities bundle can
+save siginificant time and processing on every TLS connection
+initiated by Exim.
+
+
+
+
 .section "Use of TLS Server Name Indication" "SECTtlssni"
 .cindex "TLS" "Server Name Indication"
+.cindex "TLS" SNI
+.cindex SNI
 .vindex "&$tls_in_sni$&"
 .oindex "&%tls_in_sni%&"
 With TLS1.0 or above, there is an extension mechanism by which extra
@@ -28255,6 +29813,9 @@ nothing more to it.  Choosing a sensible value not derived insecurely is the
 only point of caution.  The &$tls_out_sni$& variable will be set to this string
 for the lifetime of the client connection (including during authentication).
 
+If DANE validated the connection attempt then the value of the &%tls_sni%& option
+is forced to the domain part of the recipient address.
+
 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
 received from a client.
 It can be logged with the &%log_selector%& item &`+tls_sni`&.
@@ -28279,7 +29840,7 @@ Great care should be taken to deal with matters of case, various injection
 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
 can always be referenced; it is important to remember that &$tls_in_sni$& is
 arbitrary unverified data provided prior to authentication.
-Further, the initial certificate is loaded before SNI is arrived, so
+Further, the initial certificate is loaded before SNI has arrived, so
 an expansion for &%tls_certificate%& must have a default which is used
 when &$tls_in_sni$& is empty.
 
@@ -28295,6 +29856,33 @@ When Exim is built against GnuTLS, SNI support is available as of GnuTLS
 0.5.10.  (Its presence predates the current API which Exim uses, so if Exim
 built, then you have SNI support).
 
+.cindex TLS ALPN
+.cindex ALPN "general information"
+.cindex TLS "Application Layer Protocol Names"
+There is a TLS feature related to SNI
+called Application Layer Protocol Name (ALPN).
+This is intended to declare, or select, what protocol layer will be using a TLS
+connection.
+The client for the connection proposes a set of protocol names, and
+the server responds with a selected one.
+It is not, as of 2021, commonly used for SMTP connections.
+However, to guard against misirected or malicious use of web clients
+(which often do use ALPN) against MTA ports, Exim by default check that
+there is no incompatible ALPN specified by a client for a TLS connection.
+If there is, the connection is rejected.
+
+As a client Exim does not supply ALPN by default.
+The behaviour of both client and server can be configured using the options
+&%tls_alpn%& and &%hosts_require_alpn%&.
+There are no variables providing observability.
+Some feature-specific logging may appear on denied connections, but this
+depends on the behavious of the peer
+(not all peers can send a feature-specific TLS Alert).
+
+This feature is available when Exim is built with
+OpenSSL 1.1.0 or later or GnuTLS 3.2.0 or later;
+the macro _HAVE_TLS_ALPN will be defined when this is so.
+
 
 
 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
@@ -28368,7 +29956,7 @@ Ivan is the author of the popular TLS testing tools at
 
 
 .section "Certificate chains" "SECID186"
-The file named by &%tls_certificate%& may contain more than one
+A file named by &%tls_certificate%& may contain more than one
 certificate. This is useful in the case where the certificate that is being
 sent is validated by an intermediate certificate which the other end does
 not have. Multiple certificates must be in the correct order in the file.
@@ -28441,6 +30029,98 @@ Open-source PKI book, available online at
 .ecindex IIDencsmtp2
 
 
+.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).
+
+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
+client and used for a later session.  The ticket contains sufficient state for
+the server to reconstruct the TLS session, avoiding some expensive crypto
+calculation and (on TLS1.2) one full packet roundtrip time.
+
+.ilist
+Operational cost/benefit:
+
+ The extra data being transmitted costs a minor amount, and the client has
+ extra costs in storing and retrieving the data.
+
+ In the Exim/Gnutls implementation the extra cost on an initial connection
+ which is TLS1.2 over a loopback path is about 6ms on 2017-laptop class hardware.
+ The saved cost on a subsequent connection is about 4ms; three or more
+ connections become a net win.  On longer network paths, two or more
+ connections will have an average lower startup time thanks to the one
+ saved packet roundtrip.  TLS1.3 will save the crypto cpu costs but not any
+ packet roundtrips.
+
+.cindex "hints database" tls
+ Since a new hints DB is used on the TLS client,
+ the hints DB maintenance should be updated to additionally handle "tls".
+
+.next
+Security aspects:
+
+ The session ticket is encrypted, but is obviously an additional security
+ vulnarability surface.  An attacker able to decrypt it would have access
+ all connections using the resumed session.
+ The session ticket encryption key is not committed to storage by the server
+ and is rotated regularly (OpenSSL: 1hr, and one previous key is used for
+ overlap; GnuTLS 6hr but does not specify any overlap).
+ Tickets have limited lifetime (2hr, and new ones issued after 1hr under
+ OpenSSL.  GnuTLS 2hr, appears to not do overlap).
+
+ There is a question-mark over the security of the Diffie-Helman parameters
+ used for session negotiation.
+
+.next
+Observability:
+
+ The &%log_selector%& "tls_resumption" appends an asterisk to the tls_cipher "X="
+ element.
+
+ The variables &$tls_in_resumption$& and &$tls_out_resumption$&
+ have bits 0-4 indicating respectively
+ support built, client requested ticket, client offered session,
+ server issued ticket, resume used.  A suitable decode list is provided
+ in the builtin macro _RESUME_DECODE for in &%listextract%& expansions.
+
+.next
+Control:
+
+The &%tls_resumption_hosts%& main option specifies a hostlist for which
+exim, operating as a server, will offer resumption to clients.
+Current best practice is to not offer the feature to MUA connection.
+Commonly this can be done like this:
+.code
+tls_resumption_hosts = ${if inlist {$received_port}{587:465} {:}{*}}
+.endd
+If the peer host matches the list after expansion then resumption
+is offered and/or accepted.
+
+The &%tls_resumption_hosts%& smtp transport option performs the
+equivalent function for operation as a client.
+If the peer host matches the list after expansion then resumption
+is attempted (if a stored session is available) or the information
+stored (if supplied by the peer).
+
+
+.next
+Issues:
+
+ In a resumed session:
+.ilist
+  The variables &$tls_{in,out}_cipher$& will have values different
+ to the original (under GnuTLS).
+.next
+  The variables &$tls_{in,out}_ocsp$& will be "not requested" or "no response",
+ and the &%hosts_require_ocsp%& smtp trasnport option will fail.
+. XXX need to do something with that hosts_require_ocsp
+.endlist
+
+.endlist
+
 
 .section DANE "SECDANE"
 .cindex DANE
@@ -28458,7 +30138,7 @@ by (a) is thought to be smaller than that of the set of root CAs.
 It also allows the server to declare (implicitly) that connections to it should use TLS.  An MITM could simply
 fail to pass on a server's STARTTLS.
 
-DANE scales better than having to maintain (and side-channel communicate) copies of server certificates
+DANE scales better than having to maintain (and communicate via side-channel) copies of server certificates
 for every possible target server.  It also scales (slightly) better than having to maintain on an SMTP
 client a copy of the standard CAs bundle.  It also means not having to pay a CA for certificates.
 
@@ -28474,7 +30154,12 @@ Support for client-side operation of DANE can be included at compile time by def
 in &_Local/Makefile_&.
 If it has been included, the macro "_HAVE_DANE" will be defined.
 
-The TLSA record for the server may have "certificate usage" of DANE-TA(2) or DANE-EE(3).
+A TLSA record consist of 4 fields, the "Certificate Usage", the
+"Selector", the "Matching type", and the "Certificate Association Data".
+For a detailed description of the TLSA record see
+&url(https://tools.ietf.org/html/rfc7671#page-5,RFC 7671).
+
+The TLSA record for the server may have "Certificate Usage" (1st) field of DANE-TA(2) or DANE-EE(3).
 These are the "Trust Anchor" and "End Entity" variants.
 The latter specifies the End Entity directly, i.e. the certificate involved is that of the server
 (and if only DANE-EE is used then it should be the sole one transmitted during the TLS handshake);
@@ -28490,7 +30175,6 @@ DANE-TA is commonly used for several services and/or servers, each having a TLSA
 all of which point to a single TLSA record.
 DANE-TA and DANE-EE can both be used together.
 
-.new
 Our recommendation is to use DANE with a certificate from a public CA,
 because this enables a variety of strategies for remote clients to verify
 your certificate.
@@ -28515,25 +30199,33 @@ The list of requirements is subject to change as best practices evolve.
 If you're not already using a private CA, or it doesn't meet these
 requirements, then we encourage you to avoid all these issues and use a public
 CA such as &url(https://letsencrypt.org/,Let's Encrypt) instead.
-.wen
 
-The TLSA record should have a Selector field of SPKI(1) and a Matching Type field of SHA2-512(2).
+The TLSA record should have a "Selector" (2nd) field of SPKI(1) and
+a "Matching Type" (3rd) field of SHA2-512(2).
 
-At the time of writing, &url(https://www.huque.com/bin/gen_tlsa)
-is useful for quickly generating TLSA records; and commands like
+For the "Certificate Authority Data" (4th) field, commands like
 
 .code
-  openssl x509 -in -pubkey -noout <certificate.pem \
+  openssl x509 -pubkey -noout <certificate.pem \
   | openssl rsa -outform der -pubin 2>/dev/null \
   | openssl sha512 \
   | awk '{print $2}'
 .endd
 
-are workable for 4th-field hashes.
+are workable to create a hash of the certificate's public key.
+
+An example TLSA record for DANE-EE(3), SPKI(1), and SHA-512 (2) looks like
+
+.code
+  _25._tcp.mail.example.com. TLSA 3 1 2 8BA8A336E...
+.endd
+
+At the time of writing, &url(https://www.huque.com/bin/gen_tlsa)
+is useful for quickly generating TLSA records.
+
 
 For use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName).
 
-.new
 The Certificate issued by the CA published in the DANE-TA model should be
 issued using a strong hash algorithm.
 Exim, and importantly various other MTAs sending to you, will not
@@ -28541,7 +30233,6 @@ re-enable hash algorithms which have been disabled by default in TLS
 libraries.
 This means no MD5 and no SHA-1.  SHA2-256 is the minimum for reliable
 interoperability (and probably the maximum too, in 2018).
-.wen
 
 The use of OCSP-stapling should be considered, allowing for fast revocation of certificates (which would otherwise
 be limited by the DNS TTL on the TLSA records).  However, this is likely to only be usable with DANE-TA.  NOTE: the
@@ -28565,11 +30256,13 @@ those who use &%hosts_require_ocsp%&, should consider the interaction with DANE
 
 For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%&
 and &%dane_require_tls_ciphers%&.
-The require variant will result in failure if the target host is not DNSSEC-secured.
+The &"require"& variant will result in failure if the target host is not
+DNSSEC-secured. To get DNSSEC-secured hostname resolution, use
+the &%dnssec_request_domains%& router or transport option.
 
 DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
 
-A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using dnssec.
+A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using DNSSEC.
 If a TLSA lookup is done and succeeds, a DANE-verified TLS connection
 will be required for the host.  If it does not, the host will not
 be used; there is no fallback to non-DANE or non-TLS.
@@ -28590,12 +30283,14 @@ If DANE is requested and useable (see above) the following transport options are
   tls_verify_certificates
   tls_crl
   tls_verify_cert_hostnames
+  tls_sni
 .endd
 
 If DANE is not usable, whether requested or not, and CA-anchored
 verification evaluation is wanted, the above variables should be set appropriately.
 
-Currently the &%dnssec_request_domains%& must be active and &%dnssec_require_domains%& is ignored.
+The router and transport option &%dnssec_request_domains%& must not be
+set to &"never"&, and &%dnssec_require_domains%& is ignored.
 
 If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane".
 
@@ -29245,8 +30940,8 @@ The &%message%& modifier operates exactly as it does for &%accept%&.
 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
 forcibly closed after the 5&'xx'& error message has been sent. For example:
 .code
-drop   message   = I don't take more than 20 RCPTs
-       condition = ${if > {$rcpt_count}{20}}
+drop   condition = ${if > {$rcpt_count}{20}}
+       message   = I don't take more than 20 RCPTs
 .endd
 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
 The connection is always dropped after sending a 550 response.
@@ -29475,7 +31170,7 @@ in several different ways. For example:
 It can be at the end of an &%accept%& statement:
 .code
     accept  ...some conditions
-            control = queue_only
+            control = queue
 .endd
 In this case, the control is applied when this statement yields &"accept"&, in
 other words, when the conditions are all true.
@@ -29484,7 +31179,7 @@ other words, when the conditions are all true.
 It can be in the middle of an &%accept%& statement:
 .code
     accept  ...some conditions...
-            control = queue_only
+            control = queue
             ...some more conditions...
 .endd
 If the first set of conditions are true, the control is applied, even if the
@@ -29702,8 +31397,9 @@ anyway. If the message contains newlines, this gives rise to a multi-line SMTP
 response.
 
 .vindex "&$acl_verify_message$&"
-For ACLs that are called by an &%acl =%& ACL condition, the message is
-stored in &$acl_verify_message$&, from which the calling ACL may use it.
+While the text is being expanded, the &$acl_verify_message$& variable
+contains any message previously set.
+Afterwards, &$acl_verify_message$& is cleared.
 
 If &%message%& is used on a statement that verifies an address, the message
 specified overrides any message that is generated by the verification process.
@@ -29914,6 +31610,13 @@ This control turns off DKIM verification processing entirely.  For details on
 the operation and configuration of DKIM, see section &<<SECDKIM>>&.
 
 
+.vitem &*control&~=&~dmarc_disable_verify*&
+.cindex "disable DMARC verify"
+.cindex "DMARC" "disable verify"
+This control turns off DMARC verification processing entirely.  For details on
+the operation and configuration of DMARC, see section &<<SECDMARC>>&.
+
+
 .vitem &*control&~=&~dscp/*&<&'value'&>
 .cindex "&ACL;" "setting DSCP value"
 .cindex "DSCP" "inbound"
@@ -30042,22 +31745,37 @@ calling host. Its effect lasts until the end of the SMTP connection.
 
 .vitem &*control&~=&~no_pipelining*&
 .cindex "PIPELINING" "suppressing advertising"
+.cindex "ESMTP extensions" PIPELINING
 This control turns off the advertising of the PIPELINING extension to SMTP in
 the current session. To be useful, it must be obeyed before Exim sends its
 response to an EHLO command. Therefore, it should normally appear in an ACL
 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
 &%pipelining_advertise_hosts%&.
 
-.vitem &*control&~=&~queue_only*&
+.vitem &*control&~=&~queue/*&<&'options'&>* &&&
+       &*control&~=&~queue_only*&
+.oindex "&%queue%&"
 .oindex "&%queue_only%&"
 .cindex "queueing incoming messages"
+.cindex queueing "forcing in ACL"
+.cindex "first pass routing"
 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
 other words, only when a message is being received. If the message is accepted,
 it is placed on Exim's queue and left there for delivery by a subsequent queue
-runner. No immediate delivery process is started. In other words, it has the
-effect as the &%queue_only%& global option. However, the control applies only
-to the current message, not to any subsequent ones that may be received in the
-same SMTP connection.
+runner.
+If used with no options set,
+no immediate delivery process is started. In other words, it has the
+effect as the &%queue_only%& global option or &'-odq'& command-line option.
+
+If the &'first_pass_route'& option is given then
+the behaviour is like the command-line &'-oqds'& option;
+a delivery process is started which stops short of making
+any SMTP delivery.  The benefit is that the hints database will be updated for
+the message being waiting for a specific host, and a later queue run will be
+able to send all such messages on a single connection.
+
+The control only applies to the current message, not to any subsequent ones that
+ may be received in the same SMTP connection.
 
 .vitem &*control&~=&~submission/*&<&'options'&>
 .cindex "message" "submission"
@@ -30101,7 +31819,7 @@ data is read.
 that are being submitted at the same time using &%-bs%& or &%-bS%&.
 
 .vitem &*control&~=&~utf8_downconvert*&
-This control enables conversion of UTF-8 in message addresses
+This control enables conversion of UTF-8 in message envelope addresses
 to a-label form.
 For details see section &<<SECTi18nMTA>>&.
 .endlist vlist
@@ -30458,7 +32176,7 @@ of the lookup is made available in the &$host_data$& variable. This
 allows you, for example, to set up a statement like this:
 .code
 deny  hosts = net-lsearch;/some/file
-message = $host_data
+      message = $host_data
 .endd
 which gives a custom error message for each denied host.
 
@@ -30478,7 +32196,9 @@ the next &%local_parts%& test.
 .cindex "&ACL;" "virus scanning"
 .cindex "&ACL;" "scanning for viruses"
 This condition is available only when Exim is compiled with the
-content-scanning extension. It causes the incoming message to be scanned for
+content-scanning extension
+and only after a DATA command.
+It causes the incoming message to be scanned for
 viruses. For details, see chapter &<<CHAPexiscan>>&.
 
 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
@@ -30510,6 +32230,14 @@ content-scanning extension, and is available only in the DATA, MIME, and
 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
 
+.new
+.vitem &*seen&~=&~*&<&'parameters'&>
+.cindex "&%sseen%& ACL condition"
+This condition can be used to test if a situation has been previously met,
+for example for greylisting.
+Details are given in section &<<SECTseen>>&.
+.wen
+
 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
 .cindex "&%sender_domains%& ACL condition"
 .cindex "sender" "ACL checking"
@@ -30569,8 +32297,9 @@ send email. Details of how this works are given in section
 .cindex "header lines" "verifying header names only ASCII"
 .cindex "verifying" "header names only ASCII"
 This condition is relevant only in an ACL that is run after a message has been
-received, that is, in an ACL specified by &%acl_smtp_data%& or
-&%acl_not_smtp%&.  It checks all header names (not the content) to make sure
+received.
+This usually means an ACL specified by &%acl_smtp_data%& or &%acl_not_smtp%&.
+It checks all header names (not the content) to make sure
 there are no non-ASCII characters, also excluding control characters.  The
 allowable characters are decimal ASCII values 33 through 126.
 
@@ -30600,8 +32329,8 @@ section &<<SECTaddressverification>>& (callouts are described in section
 condition to restrict it to bounce messages only:
 .code
 deny    senders = :
-        message = A valid sender header is required for bounces
        !verify  = header_sender
+        message = A valid sender header is required for bounces
 .endd
 
 .vitem &*verify&~=&~header_syntax*&
@@ -30639,13 +32368,13 @@ client host, and its contents have been verified. If there has been no previous
 attempt to verify the HELO/EHLO contents, it is carried out when this
 condition is encountered. See the description of the &%helo_verify_hosts%& and
 &%helo_try_verify_hosts%& options for details of how to request verification
-independently of this condition.
+independently of this condition, and for detail of the verification.
 
 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
 option), this condition is always true.
 
 
-.vitem &*verify&~=&~not_blind*&
+.vitem &*verify&~=&~not_blind/*&<&'options'&>
 .cindex "verifying" "not blind"
 .cindex "bcc recipients, verifying none"
 This condition checks that there are no blind (bcc) recipients in the message.
@@ -30655,6 +32384,9 @@ case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
 used only in a DATA or non-SMTP ACL.
 
+There is one possible option, &`case_insensitive`&.  If this is present then
+local parts are checked case-insensitively.
+
 There are, of course, many legitimate messages that make use of blind (bcc)
 recipients. This check should not be used on its own for blocking messages.
 
@@ -30722,7 +32454,7 @@ Note that '/' is legal in local-parts; if the address may have such
 (eg. is generated from the received message)
 they must be protected from the options parsing by doubling:
 .code
-verify = sender=${sg{${address:$h_sender:}}{/}{//}}
+verify = sender=${listquote{/}{${address:$h_sender:}}}
 .endd
 .endlist
 
@@ -30780,8 +32512,8 @@ Testing the list of domains stops as soon as a match is found. If you want to
 warn for one list and block for another, you can use two different statements:
 .code
 deny  dnslists = blackholes.mail-abuse.org
-warn  message  = X-Warn: sending host is on dialups list
-      dnslists = dialups.mail-abuse.org
+warn  dnslists = dialups.mail-abuse.org
+      message  = X-Warn: sending host is on dialups list
 .endd
 .cindex caching "of dns lookup"
 .cindex DNS TTL
@@ -30822,8 +32554,8 @@ addresses (see, e.g., the &'domain based zones'& link at
 with these lists. You can change the name that is looked up in a DNS list by
 listing it after the domain name, introduced by a slash. For example,
 .code
-deny  message  = Sender's domain is listed at $dnslist_domain
-      dnslists = dsn.rfc-ignorant.org/$sender_address_domain
+deny  dnslists = dsn.rfc-ignorant.org/$sender_address_domain
+      message  = Sender's domain is listed at $dnslist_domain
 .endd
 This particular example is useful only in ACLs that are obeyed after the
 RCPT or DATA commands, when a sender address is available. If (for
@@ -30887,13 +32619,13 @@ dnslists = black.list.tld/a.domain::b.domain
 However, when the data for the list is obtained from a lookup, the second form
 is usually much more convenient. Consider this example:
 .code
-deny message  = The mail servers for the domain \
+deny dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
+                                   ${lookup dnsdb {>|mxh=\
+                                   $sender_address_domain} }} }
+     message  = The mail servers for the domain \
                 $sender_address_domain \
                 are listed at $dnslist_domain ($dnslist_value); \
                 see $dnslist_text.
-     dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
-                                   ${lookup dnsdb {>|mxh=\
-                                   $sender_address_domain} }} }
 .endd
 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
@@ -30930,6 +32662,11 @@ Section &<<SECTaddmatcon>>& below describes how you can distinguish between
 different values. Some DNS lists may return more than one address record;
 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
 
+Values returned by a properly running DBSBL should be in the 127.0.0.0/8
+range. If a DNSBL operator loses control of the domain, lookups on it
+may start returning other addresses.  Because of this, Exim now ignores
+returned values outside the 127/8 region.
+
 
 .section "Variables set from DNS lists" "SECID204"
 .cindex "expansion" "variables, set from DNS list"
@@ -30966,7 +32703,7 @@ very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
 information.
 
 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
-&-- although these appear before the condition in the ACL, they are not
+&-- even if these appear before the condition in the ACL, they are not
 expanded until after it has failed. For example:
 .code
 deny    hosts = !+local_networks
@@ -31066,6 +32803,14 @@ deny  dnslists = relays.ordb.org
 .endd
 which is less clear, and harder to maintain.
 
+Negation can also be used with a bitwise-and restriction.
+The dnslists condition with only be trus if a result is returned
+by the lookup which, anded with the restriction, is all zeroes.
+For example:
+.code
+deny dnslists = zen.spamhaus.org!&0.255.255.0
+.endd
+
 
 
 
@@ -31152,12 +32897,12 @@ restrictions, to get the TXT record. As a byproduct of this, there is also
 a check that the IP being tested is indeed on the first list. The first
 domain is the one that is put in &$dnslist_domain$&. For example:
 .code
-deny message  = \
-         rejected because $sender_host_address is blacklisted \
-         at $dnslist_domain\n$dnslist_text
-       dnslists = \
+deny   dnslists = \
          sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
          dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
+       message  = \
+         rejected because $sender_host_address is blacklisted \
+         at $dnslist_domain\n$dnslist_text
 .endd
 For the first blacklist item, this starts by doing a lookup in
 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
@@ -31215,6 +32960,59 @@ address you should specify alternate list separators for both the outer
        dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
 .endd
 
+
+.new
+.section "Previously seen user and hosts" "SECTseen"
+.cindex "&%sseen%& ACL condition"
+.cindex greylisting
+The &%seen%& ACL condition can be used to test whether a
+situation has been previously met.
+It uses a hints database to record a timestamp against a key.
+host. The syntax of the condition is:
+.display
+&`seen =`& <&'time interval'&> &`/`& <&'options'&>
+.endd
+
+For example,
+.code
+defer	seen = -5m / key=${sender_host_address}_$local_part@$domain
+.endd
+in a RCPT ACL will implement simple greylisting.
+
+The parameters for the condition
+are an interval followed, slash-separated, by a list of options.
+The interval is taken as an offset before the current time,
+and used for the test.
+If the interval is preceded by a minus sign then the condition returns
+whether a record is found which is before the test time.
+Otherwise, the condition returns whether one is found which is since the
+test time.
+
+Options are read in order with later ones overriding earlier ones.
+
+The default key is &$sender_host_address$&.
+An explicit key can be set using a &%key=value%& option.
+
+If a &%readonly%& option is given then
+no record create or update is done.
+If a &%write%& option is given then
+a record create or update is always done.
+An update is done if the test is for &"since"&.
+
+Creates and updates are marked with the current time.
+
+Finally, a &"before"& test which succeeds, and for which the record
+is old enough, will be refreshed with a timestamp of the test time.
+This can prevent tidying of the database from removing the entry.
+The interval for this is, by default, 10 days.
+An explicit interval can be set using a
+&%refresh=value%& option.
+
+Note that &"seen"& should be added to the list of hints databases
+for maintenance if this ACL condition is used.
+.wen
+
+
 .section "Rate limiting incoming messages" "SECTratelimiting"
 .cindex "rate limiting" "client sending"
 .cindex "limiting client sending rates"
@@ -31304,7 +33102,7 @@ in kilobytes, megabytes, or gigabytes, respectively.
 
 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
-&%acl_smtp_mime%&, &%acl_smtp_data%&, or &%acl_smtp_rcpt%& ACLs. In
+&%acl_smtp_mime%&, or &%acl_smtp_data%& ACLs. In
 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
 in either case the rate limiting engine will see a message with many
@@ -31347,12 +33145,12 @@ new rate.
 .code
 acl_check_connect:
  deny ratelimit = 100 / 5m / readonly
-    log_message = RATE CHECK: $sender_rate/$sender_rate_period \
+      log_message = RATE CHECK: $sender_rate/$sender_rate_period \
                   (max $sender_rate_limit)
 # ...
 acl_check_mail:
  warn ratelimit = 100 / 5m / strict
-    log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
+      log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
                   (max $sender_rate_limit)
 .endd
 
@@ -31382,14 +33180,12 @@ rest of the ACL.
 The &%leaky%& (default) option means that the client's recorded rate is not
 updated if it is above the limit. The effect of this is that Exim measures the
 client's average rate of successfully sent email,
-.new
 up to the given limit.
 This is appropriate if the countermeasure when the condition is true
 consists of refusing the message, and
 is generally the better choice if you have clients that retry automatically.
 If the action when true is anything more complex then this option is
 likely not what is wanted.
-.wen
 
 The &%strict%& option means that the client's recorded rate is always
 updated. The effect of this is that Exim measures the client's average rate
@@ -31464,16 +33260,16 @@ deny authenticated = *
      ratelimit = 100 / 1d / strict / $authenticated_id
 
 # System-wide rate limit
-defer message = Sorry, too busy. Try again later.
-     ratelimit = 10 / 1s / $primary_hostname
+defer ratelimit = 10 / 1s / $primary_hostname
+      message = Sorry, too busy. Try again later.
 
 # Restrict incoming rate from each host, with a default
 # set using a macro and special cases looked up in a table.
-defer message = Sender rate exceeds $sender_rate_limit \
-               messages per $sender_rate_period
-     ratelimit = ${lookup {$sender_host_address} \
+defer ratelimit = ${lookup {$sender_host_address} \
                    cdb {DB/ratelimits.cdb} \
                    {$value} {RATELIMIT} }
+      message = Sender rate exceeds $sender_rate_limit \
+               messages per $sender_rate_period
 .endd
 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
 especially with the &%per_rcpt%& option, you may suffer from a performance
@@ -31522,6 +33318,13 @@ The &%success_on_redirect%& option causes verification always to succeed
 immediately after a successful redirection. By default, if a redirection
 generates just one address, that address is also verified. See further
 discussion in section &<<SECTredirwhilveri>>&.
+.next
+If the &%quota%& option is specified for recipient verify,
+successful routing to an appendfile transport is followed by a call into
+the transport to evaluate the quota status for the recipient.
+No actual delivery is done, but verification will succeed if the quota
+is sufficient for the message (if the sender gave a message size) or
+not already exceeded (otherwise).
 .endlist
 
 .cindex "verifying address" "differentiating failures"
@@ -31538,6 +33341,7 @@ warn  !verify = sender
 If you are writing your own custom rejection message or log message when
 denying access, you can use this variable to include information about the
 verification failure.
+This variable is cleared at the end of processing the ACL verb.
 
 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
 appropriate) contains one of the following words:
@@ -31555,19 +33359,19 @@ connection, HELO, or MAIL).
 &%recipient%&: The RCPT command in a callout was rejected.
 .next
 &%postmaster%&: The postmaster check in a callout was rejected.
+.next
+&%quota%&: The quota check for a local recipient did non pass.
 .endlist
 
 The main use of these variables is expected to be to distinguish between
 rejections of MAIL and rejections of RCPT in callouts.
 
-.new
 The above variables may also be set after a &*successful*&
 address verification to:
 
 .ilist
 &%random%&: A random local-part callout succeeded
 .endlist
-.wen
 
 
 
@@ -31886,6 +33690,36 @@ behaviour will be the same.
 
 
 
+.section "Quota caching" "SECTquotacache"
+.cindex "hints database" "quota cache"
+.cindex "quota" "cache, description of"
+.cindex "caching" "quota"
+Exim caches the results of quota verification
+in order to reduce the amount of resources used.
+The &"callout"& hints database is used.
+
+The default cache periods are five minutes for a positive (good) result
+and one hour for a negative result.
+To change the periods the &%quota%& option can be followed by an equals sign
+and a number of optional paramemters, separated by commas.
+For example:
+.code
+verify = recipient/quota=cachepos=1h,cacheneg=1d
+.endd
+Possible parameters are:
+.vlist
+.vitem &*cachepos&~=&~*&<&'time&~interval'&>
+.cindex "quota cache" "positive entry expiry, specifying"
+Set the lifetime for a positive cache entry.
+A value of zero seconds is legitimate.
+
+.vitem &*cacheneg&~=&~*&<&'time&~interval'&>
+.cindex "quota cache" "negative entry expiry, specifying"
+As above, for a negative entry.
+
+.vitem &*no_cache*&
+Set both positive and negative lifetimes to zero.
+
 .section "Sender address verification reporting" "SECTsenaddver"
 .cindex "verifying" "suppressing error details"
 See section &<<SECTaddressverification>>& for a general discussion of
@@ -32064,16 +33898,16 @@ list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
 use this:
 .code
 # Bounces: drop unsigned addresses for BATV senders
-deny message = This address does not send an unsigned reverse path
-     senders = :
+deny senders = :
      recipients = +batv_senders
+     message = This address does not send an unsigned reverse path
 
 # Bounces: In case of prvs-signed address, check signature.
-deny message = Invalid reverse path signature.
-     senders = :
+deny senders = :
      condition  = ${prvscheck {$local_part@$domain}\
                   {PRVSCHECK_SQL}{1}}
      !condition = $prvscheck_result
+     message = Invalid reverse path signature.
 .endd
 The first statement rejects recipients for bounce messages that are addressed
 to plain BATV sender addresses, because it is known that BATV senders do not
@@ -32265,6 +34099,13 @@ It supports a &"generic"& interface to scanners called via the shell, and
 specialized interfaces for &"daemon"& type virus scanners, which are resident
 in memory and thus are much faster.
 
+Since message data needs to have arrived,
+the condition may be only called in ACL defined by
+&%acl_smtp_data%&,
+&%acl_smtp_data_prdr%&,
+&%acl_smtp_mime%& or
+&%acl_smtp_dkim%&
+
 A timeout of 2 minutes is applied to a scanner call (by default);
 if it expires then a defer action is taken.
 
@@ -32603,13 +34444,13 @@ imposed by your anti-virus scanner.
 
 Here is a very simple scanning example:
 .code
-deny message = This message contains malware ($malware_name)
-     malware = *
+deny malware = *
+     message = This message contains malware ($malware_name)
 .endd
 The next example accepts messages when there is a problem with the scanner:
 .code
-deny message = This message contains malware ($malware_name)
-     malware = */defer_ok
+deny malware = */defer_ok
+     message = This message contains malware ($malware_name)
 .endd
 The next example shows how to use an ACL variable to scan with both sophie and
 aveserver. It assumes you have set:
@@ -32618,13 +34459,13 @@ av_scanner = $acl_m0
 .endd
 in the main Exim configuration.
 .code
-deny message = This message contains malware ($malware_name)
-     set acl_m0 = sophie
+deny set acl_m0 = sophie
      malware = *
+     message = This message contains malware ($malware_name)
 
-deny message = This message contains malware ($malware_name)
-     set acl_m0 = aveserver
+deny set acl_m0 = aveserver
      malware = *
+     message = This message contains malware ($malware_name)
 .endd
 
 
@@ -32656,7 +34497,7 @@ intend to use an instance running on the local host you do not need to set
 you must set the &%spamd_address%& option in the global part of the Exim
 configuration as follows (example):
 .code
-spamd_address = 192.168.99.45 387
+spamd_address = 192.168.99.45 783
 .endd
 The SpamAssassin protocol relies on a TCP half-close from the client.
 If your SpamAssassin client side is running a Linux system with an
@@ -32753,8 +34594,8 @@ is set to record the actual address used.
 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
 .code
-deny message = This message was classified as SPAM
-     spam = joe
+deny spam = joe
+     message = This message was classified as SPAM
 .endd
 The right-hand side of the &%spam%& condition specifies a name. This is
 relevant if you have set up multiple SpamAssassin profiles. If you do not want
@@ -32786,9 +34627,9 @@ large ones may cause significant performance degradation. As most spam messages
 are quite small, it is recommended that you do not scan the big ones. For
 example:
 .code
-deny message = This message was classified as SPAM
-     condition = ${if < {$message_size}{10K}}
+deny condition = ${if < {$message_size}{10K}}
      spam = nobody
+     message = This message was classified as SPAM
 .endd
 
 The &%spam%& condition returns true if the threshold specified in the user's
@@ -32846,8 +34687,8 @@ failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
 statement block), append &`/defer_ok`& to the right-hand side of the
 spam condition, like this:
 .code
-deny message = This message was classified as SPAM
-     spam    = joe/defer_ok
+deny spam    = joe/defer_ok
+     message = This message was classified as SPAM
 .endd
 This causes messages to be accepted even if there is a problem with &%spamd%&.
 
@@ -32865,9 +34706,9 @@ warn  spam = nobody
       add_header = Subject: *SPAM* $h_Subject:
 
 # reject spam at high scores (> 12)
-deny  message = This message scored $spam_score spam points.
-      spam = nobody:true
+deny  spam = nobody:true
       condition = ${if >{$spam_score_int}{120}{1}{0}}
+      message = This message scored $spam_score spam points.
 .endd
 
 
@@ -32951,13 +34792,22 @@ The following list describes all expansion variables that are
 available in the MIME ACL:
 
 .vlist
+.vitem &$mime_anomaly_level$& &&&
+       &$mime_anomaly_text$&
+.vindex &$mime_anomaly_level$&
+.vindex &$mime_anomaly_text$&
+If there are problems decoding, these variables contain information on
+the detected issue.
+
 .vitem &$mime_boundary$&
-If the current part is a multipart (see &$mime_is_multipart$&) below, it should
+.vindex &$mime_boundary$&
+If the current part is a multipart (see &$mime_is_multipart$& below), it should
 have a boundary string, which is stored in this variable. If the current part
 has no boundary parameter in the &'Content-Type:'& header, this variable
 contains the empty string.
 
 .vitem &$mime_charset$&
+.vindex &$mime_charset$&
 This variable contains the character set identifier, if one was found in the
 &'Content-Type:'& header. Examples for charset identifiers are:
 .code
@@ -32969,31 +34819,37 @@ Please note that this value is not normalized, so you should do matches
 case-insensitively.
 
 .vitem &$mime_content_description$&
+.vindex &$mime_content_description$&
 This variable contains the normalized content of the &'Content-Description:'&
 header. It can contain a human-readable description of the parts content. Some
 implementations repeat the filename for attachments here, but they are usually
 only used for display purposes.
 
 .vitem &$mime_content_disposition$&
+.vindex &$mime_content_disposition$&
 This variable contains the normalized content of the &'Content-Disposition:'&
 header. You can expect strings like &"attachment"& or &"inline"& here.
 
 .vitem &$mime_content_id$&
+.vindex &$mime_content_id$&
 This variable contains the normalized content of the &'Content-ID:'& header.
 This is a unique ID that can be used to reference a part from another part.
 
 .vitem &$mime_content_size$&
+.vindex &$mime_content_size$&
 This variable is set only after the &%decode%& modifier (see above) has been
 successfully run. It contains the size of the decoded part in kilobytes. The
 size is always rounded up to full kilobytes, so only a completely empty part
 has a &$mime_content_size$& of zero.
 
 .vitem &$mime_content_transfer_encoding$&
+.vindex &$mime_content_transfer_encoding$&
 This variable contains the normalized content of the
 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
 type. Typical values are &"base64"& and &"quoted-printable"&.
 
 .vitem &$mime_content_type$&
+.vindex &$mime_content_type$&
 If the MIME part has a &'Content-Type:'& header, this variable contains its
 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
 are some examples of popular MIME types, as they may appear in this variable:
@@ -33008,6 +34864,7 @@ If the MIME part has no &'Content-Type:'& header, this variable contains the
 empty string.
 
 .vitem &$mime_decoded_filename$&
+.vindex &$mime_decoded_filename$&
 This variable is set only after the &%decode%& modifier (see above) has been
 successfully run. It contains the full path and filename of the file
 containing the decoded data.
@@ -33016,6 +34873,7 @@ containing the decoded data.
 .cindex "RFC 2047"
 .vlist
 .vitem &$mime_filename$&
+.vindex &$mime_filename$&
 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
@@ -33026,6 +34884,7 @@ decoded, but no additional sanity checks are done.
 found, this variable contains the empty string.
 
 .vitem &$mime_is_coverletter$&
+.vindex &$mime_is_coverletter$&
 This variable attempts to differentiate the &"cover letter"& of an e-mail from
 attached data. It can be used to clamp down on flashy or unnecessarily encoded
 content in the cover letter, while not restricting attachments at all.
@@ -33053,23 +34912,27 @@ As an example, the following will ban &"HTML mail"& (including that sent with
 alternative plain text), while allowing HTML files to be attached. HTML
 coverletter mail attached to non-HTML coverletter mail will also be allowed:
 .code
-deny message = HTML mail is not accepted here
-!condition = $mime_is_rfc822
-condition = $mime_is_coverletter
-condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
+deny !condition = $mime_is_rfc822
+     condition = $mime_is_coverletter
+     condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
+     message = HTML mail is not accepted here
 .endd
+
 .vitem &$mime_is_multipart$&
+.vindex &$mime_is_multipart$&
 This variable has the value 1 (true) when the current part has the main type
 &"multipart"&, for example, &"multipart/alternative"& or &"multipart/mixed"&.
 Since multipart entities only serve as containers for other parts, you may not
 want to carry out specific actions on them.
 
 .vitem &$mime_is_rfc822$&
+.vindex &$mime_is_rfc822$&
 This variable has the value 1 (true) if the current part is not a part of the
 checked message itself, but part of an attached message. Attached message
 decoding is fully recursive.
 
 .vitem &$mime_part_count$&
+.vindex &$mime_part_count$&
 This variable is a counter that is raised for each processed MIME part. It
 starts at zero for the very first part (which is usually a multipart). The
 counter is per-message, so it is reset when processing RFC822 attachments (see
@@ -33105,8 +34968,8 @@ expanded before being used, you must also escape dollar signs and backslashes
 with more backslashes, or use the &`\N`& facility to disable expansion.
 Here is a simple example that contains two regular expressions:
 .code
-deny message = contains blacklisted regex ($regex_match_string)
-     regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
+deny regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
+     message = contains blacklisted regex ($regex_match_string)
 .endd
 The conditions returns true if any one of the regular expressions matches. The
 &$regex_match_string$& expansion variable is then set up and contains the
@@ -33165,9 +35028,7 @@ code. The incident is logged on the main and reject logs.
 .cindex "&[local_scan()]& function" "building Exim to use"
 To make use of the local scan function feature, you must tell Exim where your
 function is before building Exim, by setting
-.new
 both HAVE_LOCAL_SCAN and
-.wen
 LOCAL_SCAN_SOURCE in your
 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
 directory, so you might set
@@ -33175,7 +35036,10 @@ directory, so you might set
 HAVE_LOCAL_SCAN=yes
 LOCAL_SCAN_SOURCE=Local/local_scan.c
 .endd
-for example. The function must be called &[local_scan()]&. It is called by
+for example. The function must be called &[local_scan()]&;
+the source file(s) for it should first #define LOCAL_SCAN
+and then #include "local_scan.h".
+It is called by
 Exim after it has received a message, when the success return code is about to
 be sent. This is after all the ACLs have been run. The return code from your
 function controls whether the message is actually accepted or not. There is a
@@ -33197,13 +35061,14 @@ in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
 .cindex &%dlfunc%& "API description"
 You must include this line near the start of your code:
 .code
+#define LOCAL_SCAN
 #include "local_scan.h"
 .endd
 This header file defines a number of variables and other values, and the
 prototype for the function itself. Exim is coded to use unsigned char values
 almost exclusively, and one of the things this header defines is a shorthand
 for &`unsigned char`& called &`uschar`&.
-It also contains the following macro definitions, to simplify casting character
+It also makes available the following macro definitions, to simplify casting character
 strings and pointers to character strings:
 .code
 #define CS   (char *)
@@ -33377,11 +35242,11 @@ C variables are as follows:
 .vlist
 .vitem &*int&~body_linecount*&
 This variable contains the number of lines in the message's body.
-It is not valid if the &%spool_files_wireformat%& option is used.
+It is not valid if the &%spool_wireformat%& option is used.
 
 .vitem &*int&~body_zerocount*&
 This variable contains the number of binary zero bytes in the message's body.
-It is not valid if the &%spool_files_wireformat%& option is used.
+It is not valid if the &%spool_wireformat%& option is used.
 
 .vitem &*unsigned&~int&~debug_selector*&
 This variable is set to zero when no debugging is taking place. Otherwise, it
@@ -33416,8 +35281,10 @@ discussed below.
 .vitem &*header_line&~*header_last*&
 A pointer to the last of the header lines.
 
-.vitem &*uschar&~*headers_charset*&
+.new
+.vitem &*const&~uschar&~*headers_charset*&
 The value of the &%headers_charset%& configuration option.
+.wen
 
 .vitem &*BOOL&~host_checking*&
 This variable is TRUE during a host checking session that is initiated by the
@@ -33805,8 +35672,8 @@ with translation.
 This function is used in conjunction with &'smtp_printf()'&, as described
 below.
 
-.vitem &*void&~smtp_printf(char&~*,&~...)*&
-The arguments of this function are like &[printf()]&; it writes to the SMTP
+.vitem &*void&~smtp_printf(char&~*,BOOL,&~...)*&
+The arguments of this function are almost like &[printf()]&; it writes to the SMTP
 output stream. You should use this function only when there is an SMTP output
 stream, that is, when the incoming message is being received via interactive
 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
@@ -33818,6 +35685,15 @@ is involved.
 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
 output function, so it can be used for all forms of SMTP connection.
 
+The second argument is used to request that the data be buffered
+(when TRUE) or flushed (along with any previously buffered, when FALSE).
+This is advisory only, but likely to save on system-calls and packets
+sent when a sequence of calls to the function are made.
+
+The argument was added in Exim version 4.90 - changing the API/ABI.
+Nobody noticed until 4.93 was imminent, at which point the
+ABI version number was incremented.
+
 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
 must start with an appropriate response code: 550 if you are going to return
 LOCAL_SCAN_REJECT, 451 if you are going to return
@@ -33835,7 +35711,9 @@ the data returned via the &%return_text%& argument. The added value of using
 multiple output lines.
 
 The &'smtp_printf()'& function does not return any error indication, because it
-does not automatically flush pending output, and therefore does not test
+does not
+guarantee a flush of
+pending output, and therefore does not test
 the state of the stream. (In the main code of Exim, flushing and error
 detection is done when Exim is ready for the next SMTP input command.) If
 you want to flush the output and check for an error (for example, the
@@ -33843,12 +35721,16 @@ dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
 arguments. It flushes the output stream, and returns a non-zero value if there
 is an error.
 
-.vitem &*void&~*store_get(int)*&
+.vitem &*void&~*store_get(int,BOOL)*&
 This function accesses Exim's internal store (memory) manager. It gets a new
-chunk of memory whose size is given by the argument. Exim bombs out if it ever
+chunk of memory whose size is given by the first argument.
+The second argument should be given as TRUE if the memory will be used for
+data possibly coming from an attacker (eg. the message content),
+FALSE if it is locally-sourced.
+Exim bombs out if it ever
 runs out of memory. See the next section for a discussion of memory handling.
 
-.vitem &*void&~*store_get_perm(int)*&
+.vitem &*void&~*store_get_perm(int,BOOL)*&
 This function is like &'store_get()'&, but it always gets memory from the
 permanent pool. See the next section for a discussion of memory handling.
 
@@ -34148,6 +36030,7 @@ headers remove "Old-Subject"
 
 
 .section "Setting an errors address in a system filter" "SECID217"
+.cindex "envelope from"
 .cindex "envelope sender"
 In a system filter, if a &%deliver%& command is followed by
 .code
@@ -34166,20 +36049,20 @@ address if its delivery failed.
 
 
 .section "Per-address filtering" "SECTperaddfil"
-.vindex "&$domain$&"
-.vindex "&$local_part$&"
+.vindex "&$domain_data$&"
+.vindex "&$local_part_data$&"
 In contrast to the system filter, which is run just once per message for each
 delivery attempt, it is also possible to set up a system-wide filtering
 operation that runs once for each recipient address. In this case, variables
-such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
-filter file could be made dependent on them. This is an example of a router
-which implements such a filter:
+such as &$local_part_data$& and &$domain_data$& can be used,
+and indeed, the choice of filter file could be made dependent on them.
+This is an example of a router which implements such a filter:
 .code
 central_filter:
   check_local_user
   driver = redirect
   domains = +local_domains
-  file = /central/filters/$local_part
+  file = /central/filters/$local_part_data
   no_verify
   allow_filter
   allow_freeze
@@ -34381,6 +36264,7 @@ other words, such qualification is also controlled by
 .cindex "sender" "address"
 .oindex "&%uucp_from_pattern%&"
 .oindex "&%uucp_from_sender%&"
+.cindex "envelope from"
 .cindex "envelope sender"
 .cindex "Sendmail compatibility" "&""From""& line"
 Messages that have come from UUCP (and some other applications) often begin
@@ -34420,8 +36304,7 @@ incoming SMTP message from a source that is not permitted to send them.
 
 
 .section "Resent- header lines" "SECID220"
-.cindex "&%Resent-%& header lines"
-.cindex "header lines" "Resent-"
+.chindex Resent-
 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:'&,
@@ -34477,8 +36360,7 @@ existing &'Bcc:'& is not removed.
 
 
 .section "The Date: header line" "SECID223"
-.cindex "&'Date:'& header line"
-.cindex "header lines" "Date:"
+.cindex Date:
 If a locally-generated or submission-mode message has no &'Date:'& header line,
 Exim adds one, using the current date and time, unless the
 &%suppress_local_fixups%& control has been specified.
@@ -34495,8 +36377,7 @@ messages.
 
 
 .section "The Envelope-to: header line" "SECID225"
-.cindex "&'Envelope-to:'& header line"
-.cindex "header lines" "Envelope-to:"
+.chindex Envelope-to:
 .oindex "&%envelope_to_remove%&"
 &'Envelope-to:'& 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 the
@@ -34507,8 +36388,7 @@ messages.
 
 
 .section "The From: header line" "SECTthefrohea"
-.cindex "&'From:'& header line"
-.cindex "header lines" "From:"
+.chindex From:
 .cindex "Sendmail compatibility" "&""From""& line"
 .cindex "message" "submission"
 .cindex "submission mode"
@@ -34551,8 +36431,7 @@ name as described in section &<<SECTconstr>>&.
 
 
 .section "The Message-ID: header line" "SECID226"
-.cindex "&'Message-ID:'& header line"
-.cindex "header lines" "Message-ID:"
+.chindex Message-ID:
 .cindex "message" "submission"
 .oindex "&%message_id_header_text%&"
 If a locally-generated or submission-mode incoming message does not contain a
@@ -34567,8 +36446,7 @@ in this header line by setting the &%message_id_header_text%& and/or
 
 
 .section "The Received: header line" "SECID227"
-.cindex "&'Received:'& header line"
-.cindex "header lines" "Received:"
+.chindex Received:
 A &'Received:'& header line is added at the start of every message. The
 contents are defined by the &%received_header_text%& configuration option, and
 Exim automatically adds a semicolon and a timestamp to the configured string.
@@ -34584,8 +36462,7 @@ changed to the time of acceptance, which is (apart from a small delay while the
 
 
 .section "The References: header line" "SECID228"
-.cindex "&'References:'& header line"
-.cindex "header lines" "References:"
+.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
@@ -34599,8 +36476,7 @@ incoming message. If there are more than 12, the first one and then the final
 
 
 .section "The Return-path: header line" "SECID229"
-.cindex "&'Return-path:'& header line"
-.cindex "header lines" "Return-path:"
+.chindex Return-path:
 .oindex "&%return_path_remove%&"
 &'Return-path:'& header lines are defined as something an MTA may insert when
 it does the final delivery of messages. (See the generic &%return_path_add%&
@@ -34613,7 +36489,7 @@ default), Exim removes &'Return-path:'& header lines from incoming messages.
 .section "The Sender: header line" "SECTthesenhea"
 .cindex "&'Sender:'& header line"
 .cindex "message" "submission"
-.cindex "header lines" "Sender:"
+.chindex Sender:
 For a locally-originated message from an untrusted user, Exim may remove an
 existing &'Sender:'& header line, and it may add a new one. You can modify
 these actions by setting the &%local_sender_retain%& option true, the
@@ -34936,13 +36812,14 @@ used to contain the envelope information.
 .cindex "outgoing LMTP over TCP/IP"
 .cindex "EHLO"
 .cindex "HELO"
-.cindex "SIZE option on MAIL command"
+.cindex "SIZE" "option on MAIL command"
 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
 The &%protocol%& option selects which protocol is to be used, but the actual
 processing is the same in both cases.
 
+.cindex "ESMTP extensions" SIZE
 If, in response to its EHLO command, Exim is told that the SIZE
-parameter is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
+extension is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
 command. The value of <&'n'&> is the message size plus the value of the
 &%size_addition%& option (default 1024) to allow for additions to the message
 such as per-transport header lines, or changes made in a
@@ -35338,7 +37215,8 @@ RCPT failures.
 
 .section "The ETRN command" "SECTETRN"
 .cindex "ETRN" "processing"
-RFC 1985 describes an SMTP command called ETRN that is designed to
+.cindex "ESMTP extensions" ETRN
+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
@@ -35693,10 +37571,10 @@ lists in a separate domain from normal mail. For example:
 lists:
   driver = redirect
   domains = lists.example
-  file = /usr/lists/$local_part
+  file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
   forbid_pipe
   forbid_file
-  errors_to = $local_part-request@lists.example
+  errors_to = ${quote_local_part:$local_part-request}@lists.example
   no_more
 .endd
 This router is skipped for domains other than &'lists.example'&. For addresses
@@ -35784,18 +37662,19 @@ lists_request:
   driver = redirect
   domains = lists.example
   local_part_suffix = -request
-  file = /usr/lists/$local_part$local_part_suffix
+  local_parts = ${lookup {$local_part} dsearch,filter=file {/usr/lists}}
+  file = /usr/lists/${local_part_data}-request
   no_more
 
 lists_post:
   driver = redirect
   domains = lists.example
-  senders = ${if exists {/usr/lists/$local_part}\
-             {lsearch;/usr/lists/$local_part}{*}}
-  file = /usr/lists/$local_part
+  local_parts = ${lookup {$local_part} dsearch,filter=file,ret=full {/usr/lists}}
+  senders = ${if exists {$local_part_data} {lsearch;$local_part_data}{*}}
+  file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
   forbid_pipe
   forbid_file
-  errors_to = $local_part-request@lists.example
+  errors_to = ${quote_local_part:$local_part-request}@lists.example
   no_more
 
 lists_closed:
@@ -35829,6 +37708,7 @@ the address, giving a suitable error message.
 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
 .cindex "VERP"
 .cindex "Variable Envelope Return Paths"
+.cindex "envelope from"
 .cindex "envelope sender"
 Variable Envelope Return Paths &-- see &url(https://cr.yp.to/proto/verp.txt) &--
 are a way of helping mailing list administrators discover which subscription
@@ -35852,7 +37732,7 @@ verp_smtp:
   max_rcpt = 1
   return_path = \
     ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
-      {$1-request+$local_part=$domain@your.dom.example}fail}
+      {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
 .endd
 This has the effect of rewriting the return path (envelope sender) on outgoing
 SMTP messages, if the local part of the original return path ends in
@@ -35903,7 +37783,7 @@ verp_dnslookup:
   transport = remote_smtp
   errors_to = \
     ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
-     {$1-request+$local_part=$domain@your.dom.example}fail}
+     {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
   no_more
 .endd
 Before you start sending out messages with VERPed return paths, you must also
@@ -35951,12 +37831,16 @@ to a router of this form:
 virtual:
   driver = redirect
   domains = dsearch;/etc/mail/virtual
-  data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
+  data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain_data}}
   no_more
 .endd
 The &%domains%& option specifies that the router is to be skipped, unless there
 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
-domain that is being processed. When the router runs, it looks up the local
+domain that is being processed.
+The &(dsearch)& lookup used results in an untainted version of &$domain$&
+being placed into the &$domain_data$& variable.
+
+When the router runs, it looks up the local
 part in the file to find a new address (or list of addresses). The &%no_more%&
 setting ensures that if the lookup fails (leading to &%data%& being an empty
 string), Exim gives up on the address without trying any subsequent routers.
@@ -35985,7 +37869,7 @@ follows:
 .code
 my_mailboxes:
   driver = appendfile
-  file = /var/mail/$domain/$local_part
+  file = /var/mail/$domain_data/$local_part_data
   user = mail
 .endd
 This uses a directory of mailboxes for each domain. The &%user%& setting is
@@ -36025,7 +37909,7 @@ It runs a user's &_.forward_& file for all local parts of the form
 cases by testing the variable &$local_part_suffix$&. For example:
 .code
 if $local_part_suffix contains -special then
-save /home/$local_part/Mail/special
+save /home/$local_part_data/Mail/special
 endif
 .endd
 If the filter file does not exist, or does not deal with such addresses, they
@@ -36040,9 +37924,9 @@ another MTA:
 userforward:
   driver = redirect
   check_local_user
-  file = $home/.forward$local_part_suffix
   local_part_suffix = -*
   local_part_suffix_optional
+  file = ${lookup {.forward$local_part_suffix} dsearch,ret=full {$home} {$value}fail}
   allow_filter
 .endd
 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
@@ -36159,6 +38043,7 @@ delivered immediately.
 .cindex "SMTP" "passed connection"
 .cindex "SMTP" "multiple deliveries"
 .cindex "multiple SMTP deliveries"
+.cindex "first pass routing"
 Mail waiting to be sent from an intermittently connected host will probably
 not have been routed, because without a connection DNS lookups are not
 possible. This means that if a normal queue run is done at connection time,
@@ -36392,7 +38277,7 @@ implying the use of a default path.
 When Exim encounters an empty item in the list, it searches the list defined by
 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
-mean &"use the path specified at build time"&. It no such item exists, log
+mean &"use the path specified at build time"&. If no such item exists, log
 files are written in the &_log_& subdirectory of the spool directory. This is
 equivalent to the setting:
 .code
@@ -36689,7 +38574,8 @@ fields record the router and transport that were used to process the address.
 If SMTP AUTH was used for the delivery there is an additional item A=
 followed by the name of the authenticator that was used.
 If an authenticated identification was set up by the authenticator's &%client_set_id%&
-option, this is logged too, separated by a colon from the authenticator name.
+option, this is logged too, as a second colon-separated list item.
+Optionally (see the &%smtp_mailauth%& &%log_selector%&) there may be a third list item.
 
 If a shadow transport was run after a successful local delivery, the log line
 for the successful delivery has an item added on the end, of the form
@@ -36703,8 +38589,9 @@ parentheses afterwards.
 When more than one address is included in a single delivery (for example, two
 SMTP RCPT commands in one transaction) the second and subsequent addresses are
 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
-down a single SMTP connection, an asterisk follows the IP address in the log
-lines for the second and subsequent messages.
+down a single SMTP connection, an asterisk follows the
+remote IP address (and port if enabled)
+in the log lines for the second and subsequent messages.
 When two or more messages are delivered down a single TLS connection, the
 DNS and some TLS-related information logged for the first message delivered
 will not be present in the log lines for the second and subsequent messages.
@@ -36816,11 +38703,11 @@ the following table:
 &`DKIM`&        domain verified in incoming message
 &`DN  `&        distinguished name from peer certificate
 &`DS  `&        DNSSEC secured lookups
-&`DT  `&        on &`=>`& lines: time taken for a delivery
+&`DT  `&        on &`=>`&, &'=='& and &'**'& lines: time taken for, or to attempt, a delivery
 &`F   `&        sender address (on delivery lines)
 &`H   `&        host name and IP address
 &`I   `&        local interface used
-&`id  `&        message id for incoming message
+&`id  `&        message id (from header) for incoming message
 &`K   `&        CHUNKING extension used
 &`L   `&        on &`<=`& and &`=>`& lines: PIPELINING extension used
 &`M8S `&        8BITMIME status for incoming message
@@ -36914,7 +38801,7 @@ selection marked by asterisks:
 &` arguments                  `&  command line arguments
 &`*connection_reject          `&  connection rejections
 &`*delay_delivery             `&  immediate delivery delayed
-&` deliver_time               `&  time taken to perform delivery
+&` deliver_time               `&  time taken to attempt delivery
 &` delivery_size              `&  add &`S=`&&'nnn'& to => lines
 &`*dkim                       `&  DKIM verified domain on <= lines
 &` dkim_verbose               `&  separate full DKIM verification result line, per signature
@@ -36927,10 +38814,13 @@ selection marked by asterisks:
 &` incoming_port              `&  remote port on <= lines
 &`*lost_incoming_connection   `&  as it says (includes timeouts)
 &` millisec                   `&  millisecond timestamps and RT,QT,DT,D times
+&`*msg_id                     `&  on <= lines, Message-ID: header value
+&` msg_id_created             `&  on <= lines, Message-ID: header value when one had to be added
 &` outgoing_interface         `&  local interface on => lines
 &` outgoing_port              `&  add remote port to => lines
 &`*queue_run                  `&  start and end queue runs
 &` queue_time                 `&  time on queue for one recipient
+&`*queue_time_exclusive       `&  exclude recieve time from QT times
 &` queue_time_overall         `&  time on queue for whole message
 &` pid                        `&  Exim process id
 &` pipelining                 `&  PIPELINING use, on <= and => lines
@@ -36953,9 +38843,11 @@ selection marked by asterisks:
 &` smtp_protocol_error        `&  SMTP protocol errors
 &` smtp_syntax_error          `&  SMTP syntax errors
 &` subject                    `&  contents of &'Subject:'& on <= lines
+&`*taint                      `&  taint errors or warnings
 &`*tls_certificate_verified   `&  certificate verification status
 &`*tls_cipher                 `&  TLS cipher suite on <= and => lines
 &` tls_peerdn                 `&  TLS peer DN on <= and => lines
+&` tls_resumption             `&  append * to cipher field
 &` tls_sni                    `&  TLS SNI on <= lines
 &` unknown_in_list            `&  DNS lookup failed in list match
 
@@ -37068,6 +38960,7 @@ routing email addresses, but it does apply to &"byname"& lookups.
 client's ident port times out.
 .next
 .cindex "log" "incoming interface"
+.cindex "log" "outgoing interface"
 .cindex "log" "local interface"
 .cindex "log" "local address and port"
 .cindex "TCP/IP" "logging local address and port"
@@ -37076,7 +38969,8 @@ client's ident port times out.
 to the &"<="& line as an IP address in square brackets, tagged by I= and
 followed by a colon and the port number. The local interface and port are also
 added to other SMTP log lines, for example, &"SMTP connection from"&, to
-rejection lines, and (despite the name) to outgoing &"=>"& and &"->"& lines.
+rejection lines, and (despite the name) to outgoing
+&"=>"&, &"->"&, &"=="& and &"**"& lines.
 The latter can be disabled by turning off the &%outgoing_interface%& option.
 .next
 .cindex log "incoming proxy address"
@@ -37110,6 +39004,14 @@ connection is unexpectedly dropped.
 &%millisec%&: Timestamps have a period and three decimal places of finer granularity
 appended to the seconds value.
 .next
+.cindex "log" "message id"
+&%msg_id%&: The value of the Message-ID: header.
+.next
+&%msg_id_created%&: The value of the Message-ID: header, when one had to be created.
+This will be either because the message is a bounce, or was submitted locally
+(submission mode) without one.
+The field identifier will have an asterix appended: &"id*="&.
+.next
 .cindex "log" "outgoing interface"
 .cindex "log" "local interface"
 .cindex "log" "local address and port"
@@ -37136,7 +39038,6 @@ local port is a random ephemeral port.
 &%pid%&: The current process id is added to every log line, in square brackets,
 immediately after the time and date.
 .next
-.new
 .cindex log pipelining
 .cindex pipelining "logging outgoing"
 &%pipelining%&: A field is added to delivery and accept
@@ -37145,6 +39046,13 @@ The field is a single "L".
 
 On accept lines, where PIPELINING was offered but not used by the client,
 the field has a minus appended.
+
+.cindex "pipelining" "early connection"
+If Exim is built with the SUPPORT_PIPE_CONNECT build option
+accept "L" fields have a period appended if the feature was
+offered but not used, or an asterisk appended if used.
+Delivery "L" fields have an asterisk appended if used.
+
 .next
 .cindex "log" "queue run"
 .cindex "queue runner" "logging"
@@ -37153,18 +39061,13 @@ the field has a minus appended.
 .cindex "log" "queue time"
 &%queue_time%&: The amount of time the message has been in the queue on the
 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
-&`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
-includes reception time as well as the delivery time for the current address.
-This means that it may be longer than the difference between the arrival and
-delivery log line times, because the arrival log line is not written until the
-message has been successfully received.
+&`QT=3m45s`&.
 If millisecond logging is enabled, short times will be shown with greater
 precision, eg. &`QT=1.578s`&.
 .next
 &%queue_time_overall%&: The amount of time the message has been in the queue on
 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
-example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
-message, so it includes reception time as well as the total delivery time.
+example, &`QT=3m45s`&.
 .next
 .cindex "log" "receive duration"
 &%receive_time%&: For each message, the amount of real time it has taken to
@@ -37223,10 +39126,12 @@ it is too big.
 .cindex "log" "frozen messages; skipped"
 .cindex "frozen messages" "logging skipping"
 &%skip_delivery%&: A log line is written whenever a message is skipped during a
-queue run because it is frozen or because another process is already delivering
-it.
+queue run because it another process is already delivering it or because
+it is frozen.
 .cindex "&""spool file is locked""&"
-The message that is written is &"spool file is locked"&.
+.cindex "&""message is frozen""&"
+The message that is written is either &"spool file is locked"& or
+&"message is frozen"&.
 .next
 .cindex "log" "smtp confirmation"
 .cindex "SMTP" "logging confirmation"
@@ -37329,9 +39234,14 @@ unchanged, or whether they should be rendered as escape sequences.
 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
 verified
 using a CA trust anchor,
-&`CA=dane`& if using a DNS trust anchor,
+&`CV=dane`& if using a DNS trust anchor,
 and &`CV=no`& if not.
 .next
+.cindex "log" "Taint warnings"
+&%taint%&: Log warnings about tainted data. This selector can't be
+turned of if &%allow_insecure_tainted_data%& is false (which is the
+default).
+.next
 .cindex "log" "TLS cipher"
 .cindex "TLS" "logging cipher"
 &%tls_cipher%&: When a message is sent or received over an encrypted
@@ -37343,8 +39253,15 @@ connection, the cipher suite used is added to the log line, preceded by X=.
 connection, and a certificate is supplied by the remote host, the peer DN is
 added to the log line, preceded by DN=.
 .next
+.cindex "log" "TLS resumption"
+.cindex "TLS" "logging session resumption"
+&%tls_resumption%&: When a message is sent or received over an encrypted
+connection and the TLS session resumed one used on a previous TCP connection,
+an asterisk is appended to the X= cipher field in the log line.
+.next
 .cindex "log" "TLS SNI"
 .cindex "TLS" "logging SNI"
+.cindex SNI logging
 &%tls_sni%&: When a message is received over an encrypted connection, and
 the remote host provided the Server Name Indication extension, the SNI is
 added to the log line, preceded by SNI=.
@@ -37401,9 +39318,9 @@ the next chapter. The utilities described here are:
   "check address acceptance from given IP"
 .irow &<<SECTdbmbuild>>&      &'exim_dbmbuild'& "build a DBM file"
 .irow &<<SECTfinindret>>&     &'exinext'&       "extract retry information"
-.irow &<<SECThindatmai>>&     &'exim_dumpdb'&   "dump a hints database"
-.irow &<<SECThindatmai>>&     &'exim_tidydb'&   "clean up a hints database"
-.irow &<<SECThindatmai>>&     &'exim_fixdb'&    "patch a hints database"
+.irow &<<SECTdumpdb>>&        &'exim_dumpdb'&   "dump a hints database"
+.irow &<<SECTtidydb>>&        &'exim_tidydb'&   "clean up a hints database"
+.irow &<<SECTfixdb>>&         &'exim_fixdb'&    "patch a hints database"
 .irow &<<SECTmailboxmaint>>&  &'exim_lock'&     "lock a mailbox file"
 .endtable
 
@@ -37500,6 +39417,9 @@ Match only frozen messages.
 
 .vitem &*-x*&
 Match only non-frozen messages.
+
+.vitem &*-G*&&~<&'queuename'&>
+Match only messages in the given queue.  Without this, the default queue is searched.
 .endlist
 
 The following options control the format of the output:
@@ -37885,6 +39805,8 @@ for remote hosts
 .next
 &'ratelimit'&: the data for implementing the ratelimit ACL condition
 .next
+&'tls'&: TLS session resumption data
+.next
 &'misc'&: other hints data
 .endlist
 
@@ -37902,15 +39824,21 @@ in a transport)
 
 
 
-.section "exim_dumpdb" "SECID261"
+.section "exim_dumpdb" "SECTdumpdb"
 .cindex "&'exim_dumpdb'&"
 The entire contents of a database are written to the standard output by the
-&'exim_dumpdb'& program, which has no options or arguments other than the
-spool and database names. For example, to dump the retry database:
+&'exim_dumpdb'& program,
+.new
+taking as arguments the spool and database names.
+An option &'-z'& may be given to regest times in UTC;
+otherwise times are in the local timezone.
+.wen
+For example, to dump the retry database:
 .code
 exim_dumpdb /var/spool/exim retry
 .endd
-Two lines of output are produced for each entry:
+For the retry database
+two lines of output are produced for each entry:
 .code
 T:mail.ref.example:192.168.242.242 146 77 Connection refused
 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
@@ -37939,7 +39867,7 @@ cross-references.
 
 
 
-.section "exim_tidydb" "SECID262"
+.section "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
@@ -37988,11 +39916,11 @@ databases is likely to keep on increasing.
 
 
 
-.section "exim_fixdb" "SECID263"
+.section "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
-getting round problems in a live system. It has no options, and its interface
+getting round problems in a live system. Its interface
 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
 key of a database record can then be entered, and the data for that record is
 displayed.
@@ -38009,6 +39937,12 @@ resets the time of the next delivery attempt. Time values are given as a
 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
 used as optional separators.
 
+.new
+Both displayed and input times are in the local timezone by default.
+If an option &'-z'& is used on the command line, displayed times
+are in UTC.
+.wen
+
 
 
 
@@ -38779,7 +40713,7 @@ Consider the use of the &%inlisti%& expansion condition instead.
 .cindex "security" "data sources"
 .cindex "security" "regular expressions"
 .cindex "regular expressions" "security"
-.cindex "PCRE" "security"
+.cindex "PCRE2" "security"
 If configuration data for Exim can come from untrustworthy sources, there
 are some issues to be aware of:
 
@@ -38789,7 +40723,7 @@ Use of &%${expand...}%& may provide a path for shell injection attacks.
 Letting untrusted data provide a regular expression is unwise.
 .next
 Using &%${match...}%& to apply a fixed regular expression against untrusted
-data may result in pathological behaviour within PCRE.  Be aware of what
+data may result in pathological behaviour within PCRE2.  Be aware of what
 "backtracking" means and consider options for being more strict with a regular
 expression. Avenues to explore include limiting what can match (avoiding &`.`&
 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
@@ -38965,11 +40899,9 @@ two files contains the final component of its own name as its first line. This
 is insurance against disk crashes where the directory is lost but the files
 themselves are recoverable.
 
-.new
 The file formats may be changed, or new formats added, at any release.
 Spool files are not intended as an interface to other programs
 and should not be used as such.
-.wen
 
 Some people are tempted into editing -D files in order to modify messages. You
 need to be extremely careful if you do this; it is not recommended and you are
@@ -39189,6 +41121,9 @@ was received from the client, this records the Distinguished Name from that
 certificate.
 .endlist
 
+Any of the above may have an extra hyphen prepended, to indicate the the
+corresponding data is untrusted.
+
 Following the options there is a list of those addresses to which the message
 is not to be delivered. This set of addresses is initialized from the command
 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
@@ -39297,11 +41232,11 @@ There is no dot-stuffing (and no dot-termination).
 . ////////////////////////////////////////////////////////////////////////////
 . ////////////////////////////////////////////////////////////////////////////
 
-.chapter "DKIM and SPF" "CHAPdkim" &&&
-         "DKIM and SPF Support"
-.cindex "DKIM"
+.chapter "DKIM, SPF, SRS and DMARC" "CHAPdkim" &&&
+         "DKIM, SPF, SRS and DMARC Support"
 
 .section "DKIM (DomainKeys Identified Mail)" SECDKIM
+.cindex "DKIM"
 
 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
@@ -39356,7 +41291,7 @@ senders).
 .cindex "DKIM" "signing"
 
 For signing to be usable you must have published a DKIM record in DNS.
-Note that RFC 8301 says:
+Note that RFC 8301 (which does not cover EC keys) says:
 .code
 rsa-sha1 MUST NOT be used for signing or verifying.
 
@@ -39373,15 +41308,17 @@ but for EC keys it is the base64 of the pure key; no ASN.1 wrapping.
 Signing is enabled by setting private options on the SMTP transport.
 These options take (expandable) strings as arguments.
 
-.option dkim_domain smtp string list&!! unset
+.option dkim_domain smtp "string list&!!" unset
 The domain(s) you want to sign with.
 After expansion, this can be a list.
-Each element in turn is put into the &%$dkim_domain%& expansion variable
+Each element in turn,
+lowercased,
+is put into the &%$dkim_domain%& expansion variable
 while expanding the remaining signing options.
 If it is empty after expansion, DKIM signing is not done,
 and no error will result even if &%dkim_strict%& is set.
 
-.option dkim_selector smtp string list&!! unset
+.option dkim_selector smtp "string list&!!" unset
 This sets the key selector string.
 After expansion, which can use &$dkim_domain$&, this can be a list.
 Each element in turn is put in the expansion
@@ -39390,6 +41327,13 @@ option along with &%$dkim_domain%&.
 If the option is empty after expansion, DKIM signing is not done for this domain,
 and no error will result even if &%dkim_strict%& is set.
 
+To do, for example, dual-signing with RSA and EC keys
+this could be be used:
+.code
+dkim_selector = ec_sel : rsa_sel
+dkim_private_key = KEYS_DIR/$dkim_selector
+.endd
+
 .option dkim_private_key smtp string&!! unset
 This sets the private key to use.
 You can use the &%$dkim_domain%& and
@@ -39414,6 +41358,8 @@ 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
+The result file from the first command should be retained, and
+this option set to use it.
 Take the base-64 lines from the output of the second command, concatenated,
 for the DNS TXT record.
 See section 3.6 of RFC6376 for the record specification.
@@ -39430,8 +41376,7 @@ Signers MUST use RSA keys of at least 1024 bits for all keys.
 Signers SHOULD use RSA keys of at least 2048 bits.
 .endd
 
-Support for EC keys is being developed under
-&url(https://datatracker.ietf.org/doc/draft-ietf-dcrup-dkim-crypto/).
+EC keys for DKIM are defined by 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)
@@ -39451,10 +41396,10 @@ openssl pkey -outform DER -pubout -in dkim_ed25519.private | tail -c +13 | base6
 certtool --load_privkey=dkim_ed25519.private --pubkey_info --outder | tail -c +13 | base64
 .endd
 
-Note that the format
-of Ed25519 keys in DNS has not yet been decided; this release supports
-both of the leading candidates at this time, a future release will
-probably drop support for whichever proposal loses.
+Exim also supports an alternate format
+of Ed25519 keys in DNS which was a candidate during development
+of the standard, but not adopted.
+A future release will probably drop that support.
 
 .option dkim_hash smtp string&!! sha256
 Can be set to any one of the supported hash methods, which are:
@@ -39487,7 +41432,7 @@ only supports signing with the same canonicalization method for both headers and
 .option dkim_strict smtp string&!! unset
 This  option  defines  how  Exim  behaves  when  signing a message that
 should be signed fails for some reason.  When the expansion evaluates to
-either "1" or "true", Exim will defer. Otherwise Exim will send the message
+either &"1"& or &"true"&, Exim will defer. Otherwise Exim will send the message
 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
 variables here.
 
@@ -39499,20 +41444,20 @@ in the message signature.
 When unspecified, the header names listed in RFC4871 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".
+&"_DKIM_SIGN_HEADERS"&
+and an oversigning variant is in &"_DKIM_OVERSIGN_HEADERS"&.
 
 If a name is repeated, multiple headers by that name (or the absence thereof)
 will be signed.  The textually later headers in the headers part of the
 message are signed first, if there are multiples.
 
-A name can be prefixed with either an '=' or a '+' character.
-If an '=' prefix is used, all headers that are present with this name
+A name can be prefixed with either an &"="& or a &"+"& character.
+If an &"="& prefix is used, all headers that are present with this name
 will be signed.
-If a '+' prefix if used, all headers that are present with this name
+If a &"+"& prefix if used, all headers that are present with this name
 will be signed, and one signature added for a missing header with the
 name will be appended.
 
-.new
 .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.
@@ -39522,40 +41467,46 @@ for the expiry tag
 both creation (t=) and expiry (x=) tags will be included.
 
 RFC 6376 lists these tags as RECOMMENDED.
-.wen
 
 
 .section "Verifying DKIM signatures in incoming mail" "SECDKIMVFY"
 .cindex "DKIM" "verification"
 
-.new
 Verification of DKIM signatures in SMTP incoming email is done for all
 messages for which an ACL control &%dkim_disable_verify%& has not been set.
+.cindex DKIM "selecting signature algorithms"
+Individual classes of signature algorithm can be ignored by changing
+the main options &%dkim_verify_hashes%& or &%dkim_verify_keytypes%&.
+The &%dkim_verify_minimal%& option can be set to cease verification
+processing for a message once the first passing signature is found.
+
 .cindex authentication "expansion item"
 Performing verification sets up information used by the
-&$authresults$& expansion item.
-.wen
+&%authresults%& expansion item.
 
-.new The results of that verification are then made available to the
-&%acl_smtp_dkim%& ACL, &new(which can examine and modify them).
-By default, this ACL is called once for each
-syntactically(!) correct signature in the incoming message.
+For most purposes the default option settings suffice and the remainder
+of this section can be ignored.
+
+The results of verification are made available to the
+&%acl_smtp_dkim%& ACL, which can examine and modify them.
 A missing ACL definition defaults to accept.
+By default, the ACL is called once for each
+syntactically(!) correct signature in the incoming message.
 If any ACL call does not accept, the message is not accepted.
 If a cutthrough delivery was in progress for the message, that is
 summarily dropped (having wasted the transmission effort).
 
-To evaluate the &new(verification result) in the ACL
+To evaluate the verification result in the ACL
 a large number of expansion variables
 containing the signature status and its details are set up during the
 runtime of the ACL.
 
 Calling the ACL only for existing signatures is not sufficient to build
-more advanced policies. For that reason, the global option
-&%dkim_verify_signers%&, and a global expansion variable
+more advanced policies. For that reason, the main option
+&%dkim_verify_signers%&, and an expansion variable
 &%$dkim_signers%& exist.
 
-The global option &%dkim_verify_signers%& can be set to a colon-separated
+The main option &%dkim_verify_signers%& can be set to a colon-separated
 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
 called. It is expanded when the message has been received. At this point,
 the expansion variable &%$dkim_signers%& already contains a colon-separated
@@ -39581,11 +41532,17 @@ dkim_verify_signers = $sender_address_domain:$dkim_signers
 If a domain or identity is listed several times in the (expanded) value of
 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
 
+Note that if the option is set using untrustworthy data
+(such as the From: header)
+care should be taken to force lowercase for domains
+and for the domain part if identities.
+The default setting can be regarded as trustworthy in this respect.
+
 If multiple signatures match a domain (or identity), the ACL is called once
 for each matching signature.
 
 
-Inside the &%acl_smtp_dkim%&, the following expansion variables are
+Inside the DKIM ACL, the following expansion variables are
 available (from most to least important):
 
 
@@ -39679,8 +41636,10 @@ DKIM signatures identified as having been signed with historic
 algorithms (currently, rsa-sha1) have permanently failed evaluation
 .endd
 
-To enforce this you must have a DKIM ACL which checks this variable
-and overwrites the &$dkim_verify_status$& variable as discussed above.
+To enforce this you must either have a DKIM ACL which checks this variable
+and overwrites the &$dkim_verify_status$& variable as discussed above,
+or have set the main option &%dkim_verify_hashes%& to exclude
+processing of such signatures.
 
 .vitem &%$dkim_canon_body%&
 The body canonicalization method. One of 'relaxed' or 'simple'.
@@ -39699,12 +41658,10 @@ strict enforcement should code the check explicitly.
 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
 limit was set by the signer, "9999999999999" is returned. This makes sure
 that this variable always expands to an integer value.
-.new
 &*Note:*& The presence of the signature tag specifying a signing body length
 is one possible route to spoofing of valid DKIM signatures.
 A paranoid implementation might wish to regard signature where this variable
 shows less than the "no limit" return as being invalid.
-.wen
 
 .vitem &%$dkim_created%&
 UNIX timestamp reflecting the date and time when the signature was created.
@@ -39739,6 +41696,8 @@ Notes from the key record (tag n=).
 
 .vitem &%$dkim_key_length%&
 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.
 
 Note that RFC 8301 says:
 .code
@@ -39746,9 +41705,8 @@ Verifiers MUST NOT consider signatures using RSA keys of
 less than 1024 bits as valid signatures.
 .endd
 
-To enforce this you must have a DKIM ACL which checks this variable
-and overwrites the &$dkim_verify_status$& variable as discussed above.
-As EC keys are much smaller, the check should only do this for RSA keys.
+This is enforced by the default setting for the &%dkim_verify_min_keysizes%&
+option.
 
 .endlist
 
@@ -39763,10 +41721,10 @@ verb to a group of domains or identities. For example:
 
 .code
 # Warn when Mail purportedly from GMail has no gmail signature
-warn log_message = GMail sender without gmail.com DKIM signature
-     sender_domains = gmail.com
+warn sender_domains = gmail.com
      dkim_signers = gmail.com
      dkim_status = none
+     log_message = GMail sender without gmail.com DKIM signature
 .endd
 
 Note that the above does not check for a total lack of DKIM signing;
@@ -39778,10 +41736,10 @@ results against the actual result of verification. This is typically used
 to restrict an ACL verb to a list of verification outcomes, for example:
 
 .code
-deny message = Mail from Paypal with invalid/missing signature
-     sender_domains = paypal.com:paypal.de
+deny sender_domains = paypal.com:paypal.de
      dkim_signers = paypal.com:paypal.de
      dkim_status = none:invalid:fail
+     message = Mail from Paypal with invalid/missing signature
 .endd
 
 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
@@ -39797,8 +41755,12 @@ for more information of what they mean.
 
 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.
-For more information on SPF see &url(http://www.openspf.org).
-. --- 2018-09-07: still not https
+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
+. --- web-archive copy of the now dead openspf.org site
+. --- See https://www.mail-archive.com/mailop@mailop.org/msg08019.html for a
+. --- discussion.
 
 Messages sent by a system not authorised will fail checking of such assertions.
 This includes retransmissions done by traditional forwarders.
@@ -39812,7 +41774,7 @@ publishing certain DNS records is all that is required.
 For verification, an ACL condition and an expansion lookup are provided.
 .cindex authentication "expansion item"
 Performing verification sets up information used by the
-&$authresults$& expansion item.
+&%authresults%& expansion item.
 
 
 .cindex SPF "ACL condition"
@@ -39848,6 +41810,9 @@ You may deny messages when this occurs.
 .vitem &%temperror%&
 This indicates a temporary error during all processing, including Exim's
 SPF processing.  You may defer messages when this occurs.
+
+.vitem &%invalid%&
+There was an error during processing of the SPF lookup
 .endlist
 
 You can prefix each string with an exclamation mark to  invert
@@ -39861,13 +41826,16 @@ deny spf = fail
      message = $sender_host_address is not allowed to send mail from \
                ${if def:sender_address_domain \
                     {$sender_address_domain}{$sender_helo_name}}.  \
-               Please see http://www.openspf.org/Why?scope=\
-               ${if def:sender_address_domain {mfrom}{helo}};\
+               Please see http://www.open-spf.org/Why;\
                identity=${if def:sender_address_domain \
                              {$sender_address}{$sender_helo_name}};\
                ip=$sender_host_address
 .endd
 
+Note: The above mentioned URL may not be as helpful as expected. You are
+encouraged to replace the link with a link to a site with more
+explanations.
+
 When the spf condition has run, it sets up several expansion
 variables:
 
@@ -39881,10 +41849,14 @@ variables:
 
 .vitem &$spf_received$&
 .vindex &$spf_received$&
-  This contains a complete Received-SPF: header that can be
-  added to the message. Please note that according to the SPF
-  draft, this header must be added at the top of the header
-  list. Please see section 10 on how you can do this.
+  This contains a complete Received-SPF: header (name and
+  content) that can be added to the message. Please note that
+  according to the SPF draft, this header must be added at the
+  top of the header list, i.e. with
+.code
+add_header = :at_start:$spf_received
+.endd
+  See section &<<SECTaddheadacl>>& for further details.
 
   Note: in case of "Best-guess" (see below), the convention is
   to put this string in a header called X-SPF-Guess: instead.
@@ -39892,8 +41864,8 @@ variables:
 .vitem &$spf_result$&
 .vindex &$spf_result$&
   This contains the outcome of the SPF check in string form,
-  one of pass, fail, softfail, none, neutral, permerror or
-  temperror.
+  currently one of pass, fail, softfail, none, neutral, permerror,
+  temperror, or &"(invalid)"&.
 
 .vitem &$spf_result_guessed$&
 .vindex &$spf_result_guessed$&
@@ -39902,8 +41874,11 @@ variables:
 
 .vitem &$spf_smtp_comment$&
 .vindex &$spf_smtp_comment$&
+.vindex &%spf_smtp_comment_template%&
   This contains a string that can be used in a SMTP response
   to the calling party. Useful for "fail".
+  The string is generated by the SPF library from the template configured in the main config
+  option &%spf_smtp_comment_template%&.
 .endlist
 
 
@@ -39914,9 +41889,9 @@ In addition to SPF, you can also perform checks for so-called
 "Best-guess".  Strictly speaking, "Best-guess" is not standard
 SPF, but it is supported by the same framework that enables SPF
 capability.
-Refer to &url(http://www.openspf.org/FAQ/Best_guess_record)
+Refer to &url(http://www.open-spf.org/FAQ/Best_guess_record)
 for a description of what it means.
-. --- 2018-09-07: still not https:
+. --- 2019-10-28: still not https:
 
 To access this feature, simply use the spf_guess condition in place
 of the spf one.  For example:
@@ -39949,7 +41924,9 @@ would relax host matching rules to a broader network range.
 .cindex SPF "lookup expansion"
 .cindex lookup spf
 A lookup expansion is also available. It takes an email
-address as the key and an IP address as the database:
+address as the key and an IP address
+(v4 or v6)
+as the database:
 
 .code
   ${lookup {username@domain} spf {ip.ip.ip.ip}}
@@ -39957,7 +41934,341 @@ address as the key and an IP address as the database:
 
 The lookup will return the same result strings as can appear in
 &$spf_result$& (pass,fail,softfail,neutral,none,err_perm,err_temp).
-Currently, only IPv4 addresses are supported.
+
+
+
+
+
+.section "SRS (Sender Rewriting Scheme)" SECTSRS
+.cindex SRS "sender rewriting scheme"
+
+SRS can be used to modify sender addresses when forwarding so that
+SPF verification does not object to them.
+It operates by encoding the original envelope sender in a new
+sender local part and using a domain run by the forwarding site
+as the new domain for the sender.  Any DSN message should be returned
+to this new sender at the forwarding site, which can extract the
+original sender from the coded local part and forward the DSN to
+the originator.
+
+This is a way of avoiding the breakage that SPF does to forwarding.
+The constructed local-part will be longer than the original,
+leading to possible problems with very long addresses.
+The changing of the sender address also hinders the tracing of mail
+problems.
+
+Exim can be built to include native SRS support.  To do this
+SUPPORT_SRS=yes must be defined in &_Local/Makefile_&.
+If this has been done, the macros _HAVE_SRS and _HAVE_NATIVE_SRS
+will be defined.
+The support is limited to SRS0-encoding; SRS1 is not supported.
+
+.cindex SRS excoding
+To encode an address use this expansion item:
+.vlist
+.vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
+.cindex "&%srs_encode%& expansion item"
+.cindex SRS "expansion item"
+The first argument should be a secret known and used by all systems
+handling the recipient domain for the original message.
+There is no need to periodically change this key; a timestamp is also
+encoded.
+The second argument should be given as the envelope sender address before this
+encoding operation.
+The third argument should be the recipient domain of the message when
+it arrived at this system.
+.endlist
+
+.cindex SRS decoding
+To decode an address use this expansion condition:
+.vlist
+.vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
+The first argument should be the recipient local prt as is was received.
+The second argument is the site secret.
+
+If the messages is not for an SRS-encoded recipient the condition will
+return false.  If it is, the condition will return true and the variable
+&$srs_recipient$& will be set to the decoded (original) value.
+.endlist
+
+Example usage:
+.code
+  #macro
+  SRS_SECRET = <pick something unique for your site for this. Use on all MXs.>
+
+  #routers
+
+  outbound:
+    driver =    dnslookup
+    # if outbound, and forwarding has been done, use an alternate transport
+    domains =   ! +my_domains
+    transport = ${if eq {$local_part@$domain} \
+                        {$original_local_part@$original_domain} \
+                     {remote_smtp} {remote_forwarded_smtp}}
+
+  inbound_srs:
+    driver =    redirect
+    senders =   :
+    domains =   +my_domains
+    # detect inbound bounces which are SRS'd, and decode them
+    condition = ${if inbound_srs {$local_part} {SRS_SECRET}}
+    data =      $srs_recipient
+
+  inbound_srs_failure:
+    driver =    redirect
+    senders =   :
+    domains =   +my_domains
+    # detect inbound bounces which look SRS'd but are invalid
+    condition = ${if inbound_srs {$local_part} {}}
+    allow_fail
+    data =      :fail: Invalid SRS recipient address
+
+  #... further routers here
+
+
+  # transport; should look like the non-forward outbound
+  # one, plus the max_rcpt and return_path options
+  remote_forwarded_smtp:
+    driver =              smtp
+    # modify the envelope from, for mails that we forward
+    max_rcpt =            1
+    return_path =         ${srs_encode {SRS_SECRET} {$return_path} {$original_domain}}
+.endd
+
+
+
+
+
+.section DMARC SECDMARC
+.cindex DMARC verification
+
+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/).
+
+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/)
+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.
+This description assumes
+that headers will be in /usr/local/include, and that the libraries
+are in /usr/local/lib.
+
+. subsection
+
+There are three main-configuration options:
+.cindex DMARC "configuration options"
+
+The &%dmarc_tld_file%& option
+.oindex &%dmarc_tld_file%&
+defines the location of a text file of valid
+top level domains the opendmarc library uses
+during domain parsing. Maintained by Mozilla,
+the most current version can be downloaded
+from a link at &url(https://publicsuffix.org/list/public_suffix_list.dat).
+See also the util/renew-opendmarc-tlds.sh script.
+The default for the option is unset.
+If not set, DMARC processing is disabled.
+
+
+The &%dmarc_history_file%& option, if set
+.oindex &%dmarc_history_file%&
+defines the location of a file to log results
+of dmarc verification on inbound emails. The
+contents are importable by the opendmarc tools
+which will manage the data, send out DMARC
+reports, and expire the data. Make sure the
+directory of this file is writable by the user
+exim runs as.
+The default is unset.
+
+The &%dmarc_forensic_sender%& option
+.oindex &%dmarc_forensic_sender%&
+defines an alternate email address to use when sending a
+forensic report detailing alignment failures
+if a sender domain's dmarc record specifies it
+and you have configured Exim to send them.
+If set, this is expanded and used for the
+From: header line; the address is extracted
+from it and used for the envelope from.
+If not set (the default), the From: header is expanded from
+the dsn_from option, and <> is used for the
+envelope from.
+
+. I wish we had subsections...
+
+.cindex DMARC controls
+By default, the DMARC processing will run for any remote,
+non-authenticated user.  It makes sense to only verify DMARC
+status of messages coming from remote, untrusted sources.  You can
+use standard conditions such as hosts, senders, etc, to decide that
+DMARC verification should *not* be performed for them and disable
+DMARC with an ACL control modifier:
+.code
+  control = dmarc_disable_verify
+.endd
+A DMARC record can also specify a "forensic address", which gives
+exim an email address to submit reports about failed alignment.
+Exim does not do this by default because in certain conditions it
+results in unintended information leakage (what lists a user might
+be subscribed to, etc).  You must configure exim to submit forensic
+reports to the owner of the domain.  If the DMARC record contains a
+forensic address and you specify the control statement below, then
+exim will send these forensic emails.  It is also advised that you
+configure a &%dmarc_forensic_sender%& because the default sender address
+construction might be inadequate.
+.code
+  control = dmarc_enable_forensic
+.endd
+(AGAIN: You can choose not to send these forensic reports by simply
+not putting the dmarc_enable_forensic control line at any point in
+your exim config.  If you don't tell exim to send them, it will not
+send them.)
+
+There are no options to either control.  Both must appear before
+the DATA acl.
+
+. subsection
+
+DMARC checks cam be run on incoming SMTP  messages by using the
+&"dmarc_status"& ACL condition in the DATA ACL.  You are required to
+call the &"spf"& condition first in the ACLs, then the &"dmarc_status"&
+condition.  Putting this condition in the ACLs is required in order
+for a DMARC check to actually occur.  All of the variables are set
+up before the DATA ACL, but there is no actual DMARC check that
+occurs until a &"dmarc_status"& condition is encountered in the ACLs.
+
+The &"dmarc_status"& condition takes a list of strings on its
+right-hand side.  These strings describe recommended action based
+on the DMARC check.  To understand what the policy recommendations
+mean, refer to the DMARC website above.  Valid strings are:
+.display
+&'accept      '& The DMARC check passed and the library recommends accepting the email.
+&'reject      '& The DMARC check failed and the library recommends rejecting the email.
+&'quarantine  '& The DMARC check failed and the library recommends keeping it for further inspection.
+&'none        '& The DMARC check passed and the library recommends no specific action, neutral.
+&'norecord    '& No policy section in the DMARC record for this RFC5322.From field
+&'nofrom      '& Unable to determine the domain of the sender.
+&'temperror   '& Library error or dns error.
+&'off         '& The DMARC check was disabled for this email.
+.endd
+You can prefix each string with an exclamation mark to invert its
+meaning, for example "!accept" will match all results but
+"accept".  The string list is evaluated left-to-right in a
+short-circuit fashion.  When a string matches the outcome of the
+DMARC check, the condition succeeds.  If none of the listed
+strings matches the outcome of the DMARC check, the condition
+fails.
+
+Of course, you can also use any other lookup method that Exim
+supports, including LDAP, Postgres, MySQL, etc, as long as the
+result is a list of colon-separated strings.
+
+Performing the check sets up information used by the
+&%authresults%& expansion item.
+
+Several expansion variables are set before the DATA ACL is
+processed, and you can use them in this ACL.  The following
+expansion variables are available:
+
+.vlist
+.vitem &$dmarc_status$&
+.vindex &$dmarc_status$&
+.cindex DMARC result
+A one word status indicating what the DMARC library
+thinks of the email.  It is a combination of the results of
+DMARC record lookup and the SPF/DKIM/DMARC processing results
+(if a DMARC record was found).  The actual policy declared
+in the DMARC record is in a separate expansion variable.
+
+.vitem &$dmarc_status_text$&
+.vindex &$dmarc_status_text$&
+Slightly longer, human readable status.
+
+.vitem &$dmarc_used_domain$&
+.vindex &$dmarc_used_domain$&
+The domain which DMARC used to look up the DMARC policy record.
+
+.vitem &$dmarc_domain_policy$&
+.vindex &$dmarc_domain_policy$&
+The policy declared in the DMARC record.  Valid values
+are "none", "reject" and "quarantine".  It is blank when there
+is any error, including no DMARC record.
+.endlist
+
+. subsection
+
+By default, Exim's DMARC configuration is intended to be
+non-intrusive and conservative.  To facilitate this, Exim will not
+create any type of logging files without explicit configuration by
+you, the admin.  Nor will Exim send out any emails/reports about
+DMARC issues without explicit configuration by you, the admin (other
+than typical bounce messages that may come about due to ACL
+processing or failure delivery issues).
+
+In order to log statistics suitable to be imported by the opendmarc
+tools, you need to:
+.ilist
+Configure the global option &%dmarc_history_file%&
+.next
+Configure cron jobs to call the appropriate opendmarc history
+import scripts and truncating the dmarc_history_file
+.endlist
+
+In order to send forensic reports, you need to:
+.ilist
+Configure the global option &%dmarc_forensic_sender%&
+.next
+Configure, somewhere before the DATA ACL, the control option to
+enable sending DMARC forensic reports
+.endlist
+
+. subsection
+
+Example usage:
+.code
+(RCPT ACL)
+  warn    domains        = +local_domains
+          hosts          = +local_hosts
+          control        = dmarc_disable_verify
+
+  warn    !domains       = +screwed_up_dmarc_records
+          control        = dmarc_enable_forensic
+
+  warn    condition      = (lookup if destined to mailing list)
+          set acl_m_mailing_list = 1
+
+(DATA ACL)
+  warn    dmarc_status   = accept : none : off
+          !authenticated = *
+          log_message    = DMARC DEBUG: $dmarc_status $dmarc_used_domain
+
+  warn    dmarc_status   = !accept
+          !authenticated = *
+          log_message    = DMARC DEBUG: '$dmarc_status' for $dmarc_used_domain
+
+  warn    dmarc_status   = quarantine
+          !authenticated = *
+          set $acl_m_quarantine = 1
+          # Do something in a transport with this flag variable
+
+  deny    condition      = ${if eq{$dmarc_domain_policy}{reject}}
+          condition      = ${if eq{$acl_m_mailing_list}{1}}
+          message        = Messages from $dmarc_used_domain break mailing lists
+
+  deny    dmarc_status   = reject
+          !authenticated = *
+          message        = Message from $dmarc_used_domain failed sender's DMARC policy, REJECT
+
+  warn    add_header     = :at_start:${authresults {$primary_hostname}}
+.endd
+
 
 
 
@@ -40006,7 +42317,8 @@ automatically determines which version is in use.
 The Proxy Protocol header is the first data received on a TCP connection
 and is inserted before any TLS-on-connect handshake from the client; Exim
 negotiates TLS between Exim-as-server and the remote client, not between
-Exim and the proxy server.
+Exim and the proxy server. The Proxy Protocol header must be received
+within &%proxy_protocol_timeout%&, which defaults to 3s.
 
 The following expansion variables are usable
 (&"internal"& and &"external"& here refer to the interfaces
@@ -40020,6 +42332,8 @@ of the proxy):
 .endd
 If &$proxy_session$& is set but &$proxy_external_address$& is empty
 there was a protocol error.
+The variables &$sender_host_address$& and &$sender_host_port$&
+will have values for the actual client system, not the proxy.
 
 Since the real connections are all coming from the proxy, and the
 per host connection tracking is done before Proxy Protocol is
@@ -40036,8 +42350,8 @@ A possible solution is:
   # Or do some kind of IP lookup in a flat file or database
   # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
 
-  defer   message        = Too many connections from this IP right now
-          ratelimit      = LIMIT / 5s / per_conn / strict
+  defer   ratelimit      = LIMIT / 5s / per_conn / strict
+          message        = Too many connections from this IP right now
 .endd
 
 
@@ -40133,6 +42447,7 @@ requirement, upon libidn2.
 
 .section "MTA operations" SECTi18nMTA
 .cindex SMTPUTF8 "ESMTP option"
+.cindex "ESMTP extensions" SMTPUTF8
 The main configuration option &%smtputf8_advertise_hosts%& specifies
 a host list.  If this matches the sending host and
 accept_8bitmime is true (the default) then the ESMTP option
@@ -40179,24 +42494,27 @@ may use the following modifier:
 control = utf8_downconvert
 control = utf8_downconvert/<value>
 .endd
-This sets a flag requiring that addresses are converted to
-a-label form before smtp delivery, for use in a
-Message Submission Agent context.
+This sets a flag requiring that envelope addresses are converted to
+a-label form before smtp delivery.
+This is usually for use in a Message Submission Agent context,
+but could be used for any message.
+
 If a value is appended it may be:
 .display
-&`1  `& (default) mandatory downconversion
+&`1  `& mandatory downconversion
 &`0  `& no downconversion
 &`-1 `& if SMTPUTF8 not supported by destination host
 .endd
+If no value is given, 1 is used.
 
 If mua_wrapper is set, the utf8_downconvert control
 is initially set to -1.
 
-.new
 The smtp transport has an option &%utf8_downconvert%&.
 If set it must expand to one of the three values described above,
-and it overrides any previously set value.
-.wen
+or an empty string.
+If non-empty it overrides value previously set
+(due to mua_wrapper or by an ACL control).
 
 
 There is no explicit support for VRFY and EXPN.
@@ -40290,16 +42608,18 @@ The current list of events is:
 .display
 &`dane:fail              after    transport  `& per connection
 &`msg:complete           after    main       `& per message
+&`msg:defer              after    transport  `& per message per delivery try
 &`msg:delivery           after    transport  `& per recipient
 &`msg:rcpt:host:defer    after    transport  `& per recipient per host
 &`msg:rcpt:defer         after    transport  `& per recipient
-&`msg:host:defer         after    transport  `& per attempt
+&`msg:host:defer         after    transport  `& per host per delivery try; host errors
 &`msg:fail:delivery      after    transport  `& per recipient
 &`msg:fail:internal      after    main       `& per recipient
 &`tcp:connect            before   transport  `& per connection
 &`tcp:close              after    transport  `& per connection
 &`tls:cert               before   both       `& per certificate in verification chain
 &`smtp:connect           after    transport  `& per connection
+&`smtp:ehlo              after    transport  `& per connection
 .endd
 New event types may be added in future.
 
@@ -40318,14 +42638,16 @@ An additional variable, &$event_data$&, is filled with information varying
 with the event type:
 .display
 &`dane:fail            `& failure reason
+&`msg:defer            `& error string
 &`msg:delivery         `& smtp confirmation message
 &`msg:fail:internal    `& failure reason
 &`msg:fail:delivery    `& smtp error message
+&`msg:host:defer       `& error string
 &`msg:rcpt:host:defer  `& error string
 &`msg:rcpt:defer       `& error string
-&`msg:host:defer       `& error string
 &`tls:cert             `& verification chain depth
 &`smtp:connect         `& smtp banner
+&`smtp:ehlo            `& smtp ehlo response
 .endd
 
 The :defer events populate one extra variable: &$event_defer_errno$&.