X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/b4f579d134197249b448cb5d8abf801ba4c729bb..5c161fa615ab4a2d40170fedd71d1b9a7f079ff6:/doc/doc-docbook/spec.xfpt

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index 5463cc1a5..34b36ca9f 100644
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -45,14 +45,14 @@
 . Update the Copyright year (only) when changing content.
 . /////////////////////////////////////////////////////////////////////////////
 
-.set previousversion "4.92"
+.set previousversion "4.94"
 .include ./local_params
 
 .set ACL "access control lists (ACLs)"
 .set I   "    "
 
 .macro copyyear
-2018
+2020
 .endmacro
 
 . /////////////////////////////////////////////////////////////////////////////
@@ -371,11 +371,13 @@ contributors.
 .section "Exim documentation" "SECID1"
 . Keep this example change bar when updating the documentation!
 
+.new
 .cindex "documentation"
 This edition of the Exim specification applies to version &version() of Exim.
 Substantive changes from the &previousversion; edition are marked in some
 renditions of this document; this paragraph is so marked if the rendition is
 capable of showing a change indicator.
+.wen
 
 This document is very much a reference manual; it is not a tutorial. The reader
 is expected to have some familiarity with the SMTP mail transfer protocol and
@@ -1392,21 +1394,50 @@ 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.
+.new
+.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.
+.wen
+
 .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.
+.new
+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.
+.wen
+
+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 "&$local_user_gid$&"
@@ -1416,23 +1447,37 @@ 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>>&.
+
+.new
+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.
+.wen
 .endlist
 
 
@@ -1886,11 +1931,10 @@ 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).
@@ -1899,35 +1943,39 @@ 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
@@ -1935,7 +1983,6 @@ 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
@@ -2528,6 +2575,8 @@ use of Exim's filtering capabilities, you should make the document entitled
 If you are already running Exim on your host, building and installing a new
 version automatically makes it available to MUAs, or any other programs that
 call the MTA directly. However, if you are running an Exim daemon, you do need
+.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
@@ -2766,9 +2815,12 @@ 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
@@ -3857,6 +3909,12 @@ 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
@@ -3884,11 +3942,18 @@ 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.
 
+.new
+.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.
+.wen
+
 .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%&
@@ -3897,6 +3962,18 @@ 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.
 
+.new
+.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.
+.wen
+
 .vitem &%-MCt%&&~<&'IP&~address'&>&~<&'port'&>&~<&'cipher'&>
 .oindex "&%-MCt%&"
 This option is not intended for use by external callers. It is used internally
@@ -3954,6 +4031,18 @@ 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"
@@ -4164,6 +4253,7 @@ 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
@@ -4362,6 +4452,15 @@ 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"
@@ -4394,6 +4493,27 @@ 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.
 
+.new
+.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
+.wen
+
 .vitem &%-pd%&
 .oindex "&%-pd%&"
 .cindex "Perl" "starting the interpreter"
@@ -4471,11 +4591,19 @@ 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
@@ -4521,7 +4649,7 @@ 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.
@@ -5854,13 +5982,13 @@ 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.
@@ -5964,10 +6092,10 @@ 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 \
@@ -6254,10 +6382,6 @@ 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
@@ -6265,9 +6389,7 @@ 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
@@ -6336,7 +6458,7 @@ 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
@@ -6344,7 +6466,15 @@ 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
@@ -6549,14 +6679,15 @@ 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
@@ -6586,10 +6717,13 @@ 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:
@@ -6606,6 +6740,18 @@ 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.
 
+.new
+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.
+.wen
+
 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.
@@ -6620,6 +6766,16 @@ 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
@@ -6658,11 +6814,10 @@ 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
@@ -6712,11 +6867,38 @@ 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
@@ -6747,13 +6929,17 @@ lookup types support only literal keys.
 the implicit key is the host's IP address rather than its name (see section
 &<<SECThoslispatsikey>>&).
 
-.new
 &*Warning 3*&: Do not use an IPv4-mapped IPv6 address for a key; use the
 IPv4, in dotted-quad form. (Exim converts IPv4-mapped IPv6 addresses to this
 notation before executing the lookup.)
+
+.new
+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.
 .wen
+
 .next
-.new
 .cindex lookup json
 .cindex json "lookup type"
 .cindex JSON expansions
@@ -6767,10 +6953,32 @@ 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 os the JSON
+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.
+
+
+.new
+.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.
 .wen
+
+
 .next
 .cindex "linear search"
 .cindex "lookup" "lsearch"
@@ -6892,9 +7100,10 @@ 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
 
@@ -6965,8 +7174,8 @@ 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
@@ -7324,7 +7533,7 @@ 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.
 
@@ -7872,6 +8081,11 @@ 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>>&.)
@@ -7924,9 +8138,9 @@ 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
@@ -7952,14 +8166,23 @@ 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"
@@ -8009,17 +8232,39 @@ 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:
+daemon as in the other SQL databases.
+
+.new
+.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.
+.wen
+
+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
-${lookup sqlite {/some/thing/sqlitedb \
-  select name from aliases where id='userx';}}
+sqlite_dbfile = /some/thing/sqlitedb
+...
+${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
@@ -8211,6 +8456,36 @@ 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
+.new
+A &%domains%& router option or &%domains%& ACL condition
+will store a result in the &$domain_data$& variable
+.wen
+.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"
@@ -8269,6 +8544,17 @@ 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
@@ -8360,6 +8646,10 @@ 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"
@@ -8369,7 +8659,12 @@ 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"
@@ -8418,6 +8713,9 @@ 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"
@@ -8430,6 +8728,10 @@ 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"
@@ -8446,6 +8748,13 @@ 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"
@@ -8457,12 +8766,15 @@ 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.
+
 
 .next
 Any of the single-key lookup type names may be preceded by
@@ -8481,6 +8793,7 @@ 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
@@ -8490,17 +8803,40 @@ 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 "=".
+
 .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 = \
@@ -8690,11 +9026,9 @@ 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.
-.new
 In all cases except IPv4-mapped IPv6, full, unabbreviated IPv6
 addresses are always used.
 The latter are converted to IPv4 addresses, in dotted-quad form.
-.wen
 
 Ideally, it would be nice to tidy up this anomalous situation by changing to
 colons in all cases, given that quoting is now available for &(lsearch)&.
@@ -9172,6 +9506,9 @@ 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%&
@@ -9214,7 +9551,25 @@ 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"&)
+.new
+is not permitted (including acessing a file using a tainted name).
+.wen
+
+.new
+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"&.
+.wen
 
 
 
@@ -9364,7 +9719,7 @@ If the ACL returns defer the result is a forced-fail.  Otherwise the expansion f
 .cindex headers "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.
@@ -9461,9 +9816,13 @@ 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
@@ -9572,10 +9931,8 @@ 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.
-.new
 For the &"jsons"& variant, which is intended for use with JSON strings, the
 leading and trailing quotes are removed from the returned value.
-.wen
 . XXX should be a UTF-8 compare
 
 The results of matching are handled as above.
@@ -9626,10 +9983,8 @@ there is no choice of field separator.
 For the &"json"& variant,
 if a returned value is a JSON string, it retains its leading and
 trailing quotes.
-.new
 For the &"jsons"& variant, which is intended for use with JSON strings, the
 leading and trailing quotes are removed from the returned value.
-.wen
 
 
 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
@@ -9648,7 +10003,7 @@ 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 &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
@@ -9686,7 +10041,7 @@ letters appear. For example:
        "&*$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"
@@ -9792,6 +10147,10 @@ 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"
@@ -9923,12 +10282,21 @@ extracted is used.
 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
 
 
-.vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
-        {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
-This is the first of one of two different types of lookup item, which are both
-described in the next item.
+.new
+.vitem &*${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.
+.wen
+
 
-.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"
@@ -9999,8 +10367,8 @@ 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"
@@ -10133,21 +10501,35 @@ ${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
 ${readsocket{/socket/name}{request string}{3s:shutdown=no}}
 .endd
-The second, tls, controls the use of TLS on the connection.  Example:
-.code
-${readsocket{/socket/name}{request string}{3s:tls=yes}}
-.endd
-The default is to not use TLS.
+
+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 descripbed 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
@@ -10199,7 +10581,7 @@ 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}}}
@@ -10210,7 +10592,7 @@ 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'&>&*:*&
@@ -10348,6 +10730,14 @@ ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
 will sort an MX lookup into priority order.
 
 
+
+.new
+.vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
+SRS encoding.  See SECT &<<SECTSRS>>& for details.
+.wen
+
+
+
 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
 .cindex "&%substr%& expansion item"
 .cindex "substring extraction"
@@ -10470,9 +10860,9 @@ 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
@@ -10622,8 +11012,7 @@ 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}}       \
            {                          \
@@ -10632,6 +11021,7 @@ 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.
@@ -10976,14 +11366,12 @@ it as a 64-digit hexadecimal number, in which any letters are in upper case.
 If the string is a single variable of type certificate,
 returns the SHA-256 hash fingerprint of the certificate.
 
-.new
 The operator can also be spelled &%sha2%& and does the same as &%sha256%&
 (except for certificates, which are not supported).
 Finally, if an underbar
 and a number is appended it specifies the output length, selecting a
 member of the SHA-2 family of hash functions.
 Values of 256, 384 and 512 are accepted, with 256 being the default.
-.wen
 
 
 .vitem &*${sha3:*&<&'string'&>&*}*& &&&
@@ -11328,6 +11716,11 @@ 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.
 
+.new
+&*Note:*& Testing a path using this condition is not a sufficient way of
+de-tainting it.
+.wen
+
 .vitem &*first_delivery*&
 .cindex "delivery" "first"
 .cindex "first delivery"
@@ -11365,12 +11758,11 @@ 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.
 
-.new
 .vitem "&*forall_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
        "&*forany_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
        "&*forall_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
@@ -11386,7 +11778,6 @@ 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.
-.wen
 
 
 
@@ -11414,6 +11805,13 @@ includes the case of letters, whereas for &%gti%& the comparison is
 case-independent.
 Case and collation order are defined per the system C locale.
 
+
+.new
+.vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
+SRS decode.  See SECT &<<SECTSRS>>& for details.
+.wen
+
+
 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
        &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
 .cindex "string" "comparison"
@@ -11663,15 +12061,12 @@ 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
@@ -12098,6 +12493,13 @@ 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 &$dnslist_domain$& &&&
        &$dnslist_matched$& &&&
        &$dnslist_text$& &&&
@@ -12166,20 +12568,34 @@ 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
+.new
+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.
+.wen
+
+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 "&$exim_gid$&"
@@ -12260,7 +12676,7 @@ 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$&
 .cindex "host name" "lookup, failure of"
@@ -12293,7 +12709,7 @@ the result, the name is not accepted, and &$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 &$host_lookup_failed$&
@@ -12359,13 +12775,24 @@ 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
@@ -12401,29 +12828,34 @@ 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
+.new
+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.
+.wen
+
+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 "&$local_scan_data$&"
@@ -12589,9 +13021,9 @@ 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 - $body_linecount}}}
+     message   = Too many lines in message header
 .endd
 In the MAIL and RCPT ACLs, the value is zero because at that stage the
 message has not yet been received.
@@ -12755,11 +13187,19 @@ or if not set, the value of &$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.
 
-.new
+.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
@@ -12767,7 +13207,6 @@ Values can be placed in these variables by the &%set%& option of a router.
 They can be given any name that starts with &$r_$&.
 The values persist for the address being handled through subsequent routers
 and the eventual transport.
-.wen
 
 .vitem &$rcpt_count$&
 .vindex "&$rcpt_count$&"
@@ -13075,6 +13514,16 @@ 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).
 
@@ -13331,6 +13780,7 @@ 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 "&$tls_in_peercert$&"
@@ -13387,11 +13837,9 @@ 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 &$tls_out_cipher$&.
 
-.new
 .vitem &$tls_in_cipher_std$&
 .vindex "&$tls_in_cipher_std$&"
 As above, but returning the RFC standard name for the cipher suite.
-.wen
 
 .vitem &$tls_out_cipher$&
 .vindex "&$tls_out_cipher$&"
@@ -13401,11 +13849,9 @@ 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.
 
-,new
 .vitem &$tls_out_cipher_std$&
 .vindex "&$tls_out_cipher_std$&"
 As above, but returning the RFC standard name for the cipher suite.
-.wen
 
 .vitem &$tls_out_dane$&
 .vindex &$tls_out_dane$&
@@ -13453,10 +13899,23 @@ 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.
 
+
+.new
+.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.
+.wen
+
+
 .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
@@ -13472,6 +13931,8 @@ 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.
@@ -13480,6 +13941,17 @@ 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
@@ -13621,6 +14093,10 @@ 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.
 
+.new
+&*Note*&: This is entirely separate from Exim's tainted-data tracking.
+.wen
+
 
 .section "Calling Perl subroutines" "SECID86"
 When the configuration file includes a &%perl_startup%& option you can make use
@@ -14175,6 +14651,7 @@ 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"
 .endtable
@@ -14252,8 +14729,10 @@ 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
 
 
@@ -14336,7 +14815,13 @@ 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"
@@ -14438,6 +14923,7 @@ 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"
@@ -14484,6 +14970,7 @@ 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
@@ -14622,8 +15109,10 @@ 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
@@ -14667,13 +15156,18 @@ 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
@@ -14690,6 +15184,7 @@ 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.
@@ -14751,12 +15246,16 @@ 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
@@ -14945,6 +15444,7 @@ 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.
@@ -15081,6 +15581,38 @@ 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.
@@ -15089,6 +15621,14 @@ 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
@@ -15159,6 +15699,16 @@ 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"
@@ -15172,11 +15722,9 @@ 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.
-.new
 Note that all lookups, including those done for verification, are affected;
 this will result in verify failure for IPv6 connections or ones using names
 only valid for IPv6 addresses.
-.wen
 
 
 .option dns_retrans main time 0s
@@ -15250,6 +15798,7 @@ 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,
@@ -15257,6 +15806,8 @@ and RET and ORCPT 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"
@@ -15383,8 +15934,8 @@ used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
 .cindex "Exim version"
 .cindex customizing "version number"
 .cindex "version number of Exim" override
-This option allows to override the &$version_number$&/&$exim_version$& Exim reports in
-various places.  Use with care, this may fool stupid security scanners.
+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
@@ -16007,6 +16558,8 @@ 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
@@ -16136,6 +16689,11 @@ 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
@@ -16213,7 +16771,29 @@ harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
 transport driver.
 
 
-.option openssl_options main "string list" "+no_sslv2 +no_sslv3 +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,
+.new "if nonempty,"
+it should be a full path name and use a directory accessible
+to Exim.
+
+.new
+If this option is set as empty,
+or the command line &%-oY%& option is used, or
+.wen
+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,
@@ -16354,9 +16934,9 @@ 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
@@ -16385,6 +16965,7 @@ 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
@@ -16393,22 +16974,24 @@ 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%&).
 
-.new
 .option pipelining_connect_advertise_hosts main "host list&!!" *
 .cindex "pipelining" "early connection"
 .cindex "pipelining" PIPE_CONNECT
+.cindex "ESMTP extensions" X_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.
+
 Currently the option name &"X_PIPE_CONNECT"& is used.
-.wen
 
 
 .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.
@@ -16484,6 +17067,14 @@ admin user unless &%prod_requires_admin%& is set false. See also
 &%queue_list_requires_admin%& and &%commandline_checks_require_admin%&.
 
 
+.new
+.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>>&.
+.wen
+
+
 .option qualify_domain main string "see below"
 .cindex "domain" "for qualifying addresses"
 .cindex "address" "qualification"
@@ -16519,6 +17110,17 @@ domains that do not match are processed. All other deliveries wait until the
 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
 
 
+.new
+.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.
+.wen
+
+
 .option queue_list_requires_admin main boolean true
 .cindex "restricting access to features"
 .oindex "&%-bp%&"
@@ -16629,13 +17231,14 @@ 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
@@ -16667,7 +17270,6 @@ 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.
-.new
 The default setting is:
 
 .code
@@ -16678,6 +17280,7 @@ received_header_text = Received: \
         ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
   by $primary_hostname \
   ${if def:received_protocol {with $received_protocol }}\
+  ${if def:tls_in_ver        { ($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 \
@@ -16685,9 +17288,9 @@ received_header_text = Received: \
   id $message_exim_id\
   ${if def:received_for {\n\tfor $received_for}}
 .endd
-.wen
 
-The reference to the TLS cipher is omitted when Exim is built without TLS
+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:
@@ -16774,6 +17377,9 @@ 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
@@ -16864,12 +17470,6 @@ 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"
@@ -17133,6 +17733,7 @@ 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
@@ -17144,6 +17745,11 @@ 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
@@ -17306,7 +17912,8 @@ 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
@@ -17324,6 +17931,46 @@ 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
@@ -17475,6 +18122,7 @@ 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.
@@ -17597,6 +18245,7 @@ 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
@@ -17610,8 +18259,8 @@ is not required the &%tls_advertise_hosts%& option should be set empty.
 .cindex "TLS" "server certificate; location of"
 .cindex "certificate" "server, location of"
 The value of this option is expanded, and must then be a list of absolute paths to
-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.
@@ -17627,10 +18276,9 @@ separator in the usual way (&<<SECTlistsepchange>>&) to avoid confusion under IP
 &*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
@@ -17680,7 +18328,12 @@ larger prime than requested.
 The value of this option is expanded and indicates the source of DH parameters
 to be used by Exim.
 
-&*Note: The Exim Maintainers strongly recommend using a filename with site-generated
+This option is ignored for GnuTLS version 3.6.0 and later.
+The library manages parameter negotiation internally.
+
+&*Note: The Exim Maintainers strongly recommend,
+for other TLS library versions,
+using a filename with site-generated
 local DH parameters*&, which has been supported across all versions of Exim.  The
 other specific constants available are a fallback so that even when
 "unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
@@ -17775,11 +18428,29 @@ 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
@@ -17825,6 +18496,14 @@ preference order of the available ciphers. Details are given in sections
 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
 
 
+.new
+.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.
+.wen
+
+
 .option tls_try_verify_hosts main "host list&!!" unset
 .cindex "TLS" "client certificate verification"
 .cindex "certificate" "verification of client"
@@ -17859,7 +18538,9 @@ 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.
 
@@ -18013,14 +18694,18 @@ 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
@@ -18088,9 +18773,7 @@ file = ${extract{mailbox}{$address_data}}
 This makes the configuration file less messy, and also reduces the number of
 lookups (though Exim does cache lookups).
 
-.new
 See also the &%set%& option below.
-.wen
 
 .vindex "&$sender_address_data$&"
 .vindex "&$address_data$&"
@@ -18176,7 +18859,10 @@ 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,
@@ -18297,7 +18983,7 @@ 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"
@@ -18323,7 +19009,8 @@ 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.
 
 
@@ -18505,15 +19192,17 @@ 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.
@@ -18618,6 +19307,10 @@ 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
@@ -18680,12 +19373,13 @@ 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:
@@ -18823,7 +19517,7 @@ 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.
@@ -18873,11 +19567,22 @@ 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.
@@ -19006,18 +19711,16 @@ SMTP VRFY command is enabled, it must be used after MAIL if the sender address
 matters.
 
 
-.new
 .option set routers "string list" unset
 .cindex router variables
 This option may be used multiple times on a router;
 because of this the list aspect is mostly irrelevant.
-The list separator is a colon but can be changed in the
+The list separator is a semicolon but can be changed in the
 usual way.
 
-Each list-element given must be of the form $"name = value"$
+Each list-element given must be of the form &"name = value"&
 and the names used must start with the string &"r_"&.
-Values containing colons should either have them doubled, or
-the entire list should be prefixed with a list-separator change.
+Values containing a list-separator should have them doubled.
 When a router runs, the strings are evaluated in order,
 to create variables which are added to the set associated with
 the address.
@@ -19026,11 +19729,10 @@ The variables can be used by the router options
 (not including any preconditions)
 and by the transport.
 Later definitions of a given named variable will override former ones.
-Varible use is via the usual &$r_...$& syntax.
+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.
-.wen
 
 
 .option translate_ip_address routers string&!! unset
@@ -19948,8 +20650,10 @@ 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:
@@ -20441,6 +21145,17 @@ 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"
@@ -20666,6 +21381,9 @@ 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"
@@ -21426,7 +22144,7 @@ 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
@@ -21666,15 +22384,19 @@ 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.
@@ -21935,7 +22657,7 @@ 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
@@ -22225,6 +22947,12 @@ 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
+.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)&"
@@ -22247,7 +22975,7 @@ 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} \
@@ -22428,8 +23156,8 @@ 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"
@@ -22813,6 +23541,13 @@ 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
@@ -23178,7 +23913,7 @@ 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 = /\.[^/]+$
@@ -23655,6 +24390,10 @@ 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
@@ -24162,14 +24901,14 @@ 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
@@ -24360,12 +25099,14 @@ 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
@@ -24401,21 +25142,30 @@ 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
+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
@@ -24457,14 +25207,15 @@ 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.
 
 
 
@@ -24474,9 +25225,9 @@ 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.
 
 
 
@@ -24530,6 +25281,7 @@ 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.
@@ -24618,10 +25370,10 @@ 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.
 
-.new
 .option hosts_pipe_connect smtp "host list&!!" unset
 .cindex "pipelining" "early connection"
 .cindex "pipelining" PIPE_CONNECT
@@ -24635,6 +25387,8 @@ 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
@@ -24643,7 +25397,6 @@ A check is made for the use of that variable, without the
 presence of a &"def:"& test on it, but suitably complex coding
 can avoid the check and produce unexpected results.
 You have been warned.
-.wen
 
 
 .option hosts_avoid_tls smtp "host list&!!" unset
@@ -24684,7 +25437,6 @@ 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.
 
-.new
 .option hosts_noproxy_tls smtp "host list&!!" unset
 .cindex "TLS" "passing connection"
 .cindex "multiple SMTP deliveries"
@@ -24692,7 +25444,6 @@ explanation of when this might be needed.
 For any host that matches this list, a TLS session which has
 been started will not be passed to a new delivery process for sending another
 message on the same session.
-.wen
 
 The traditional implementation closes down TLS and re-starts it in the new
 process, on the same open TCP connection, for each successive message
@@ -24755,7 +25506,8 @@ TLS session for any host that matches this list.
 .cindex DANE "requiring for certain servers"
 If built with DANE support, Exim  will require that a DNSSEC-validated
 TLSA record is present for any host matching the list,
-and that a DANE-verified TLS connection is made.
+and that a DANE-verified TLS connection is made. See
+the &%dnssec_request_domains%& router and transport options.
 There will be no fallback to in-clear communication.
 See section &<<SECDANE>>&.
 
@@ -24776,9 +25528,12 @@ 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
+.new
+and &%hosts_require_auth%& permits,
+.wen
+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"
@@ -24786,16 +25541,17 @@ 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&!!" *
 .cindex DANE "transport options"
 .cindex DANE "attempting for certain servers"
-If built with DANE support, Exim  will lookup a
-TLSA record for any host matching the list.
-If found and verified by DNSSEC,
-a DANE-verified TLS connection is made to that host;
-there will be no fallback to in-clear communication.
+If built with DANE support, Exim  will require that a DNSSEC-validated
+TLSA record is present for any host matching the list,
+and that a DANE-verified TLS connection is made. See
+the &%dnssec_request_domains%& router and transport options.
+There will be no fallback to in-clear communication.
 See section &<<SECDANE>>&.
 
 .option hosts_try_fastopen smtp "host list&!!" *
@@ -24820,6 +25576,7 @@ 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.
@@ -24882,6 +25639,20 @@ so can cause parallel connections to the same host if &%remote_max_parallel%&
 permits this.
 
 
+.new
+.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.
+.wen
+
+
 .option multi_domain smtp boolean&!! true
 .vindex "&$domain$&"
 When this option is set, the &(smtp)& transport can handle a number of
@@ -24895,6 +25666,12 @@ It is expanded per-address and can depend on any of
 &$address_data$&, &$domain_data$&, &$local_part_data$&,
 &$host$&, &$host_address$& and &$host_port$&.
 
+.new
+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.
+.wen
+
 .option port smtp string&!! "see below"
 .cindex "port" "sending TCP/IP"
 .cindex "TCP/IP" "setting outgoing port"
@@ -24977,7 +25754,7 @@ 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"
@@ -25063,11 +25840,25 @@ is used in different ways by OpenSSL and GnuTLS (see sections
 ciphers is a preference order.
 
 
+.new
+.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.
+.wen
+
+
 
 .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
+.new
+and the connection is not DANE-validated
+.wen
+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.
@@ -25162,13 +25953,17 @@ 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.
 
-.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>>&.
+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>>&.
 
 
 
@@ -26276,6 +27071,7 @@ transfer of mail between servers that have no managerial connection with each
 other.
 
 .cindex "AUTH" "description of"
+.cindex "ESMTP extensions" AUTH
 Very briefly, the way SMTP authentication works is as follows:
 
 .ilist
@@ -26342,10 +27138,8 @@ 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.
-.new
 The fourth provides for negotiation of authentication done via non-SMTP means,
 as defined by RFC 4422 Appendix A.
-.wen
 The fifth provides an interface to the GNU SASL authentication library, which
 provides mechanisms but typically not data sources.
 The sixth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
@@ -26634,7 +27428,7 @@ no successful authentication.
 
 .cindex authentication "expansion item"
 Successful authentication sets up information used by the
-&$authresults$& expansion item.
+&%authresults%& expansion item.
 
 
 
@@ -26770,7 +27564,19 @@ 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:
 
@@ -26778,7 +27584,7 @@ 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.
@@ -26827,7 +27633,7 @@ 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
@@ -26909,7 +27715,7 @@ 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
@@ -27030,7 +27836,7 @@ 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
@@ -27248,7 +28054,7 @@ 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
@@ -27279,6 +28085,27 @@ 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 wil 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
 
@@ -27296,20 +28123,52 @@ 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.
+
+
+.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
+If a SCRAM mechanism is being used and this option is set
+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.
+
 
 
 .option server_channelbinding gsasl boolean false
-Do not set this true without consulting a cryptographic engineer.
+Do not set this true and rely on the properties
+without consulting a cryptographic engineer.
 
 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
@@ -27321,15 +28180,16 @@ 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.
+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).
 
@@ -27377,16 +28237,54 @@ 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`&
@@ -27694,11 +28592,10 @@ 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 that, up to TLS1.2, the client cert is on the wire in-clear, including the SAN,
+&*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.
-Likewise, a traditional plaintext SMTP AUTH done inside TLS is not.
 
 
 .section "Using external in a client" "SECTexternclient"
@@ -27911,16 +28808,19 @@ 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.
 
@@ -27964,6 +28864,12 @@ 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.
+.new
+.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.
+.wen
 .endlist
 
 
@@ -28189,6 +29095,7 @@ 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
@@ -28436,6 +29343,61 @@ There is no current way to staple a proof for a client certificate.
 .endd
 
 
+.new
+.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.
+.wen
+
+
 
 
 .section "Configuring an Exim client to use TLS" "SECTclientTLS"
@@ -28448,6 +29410,7 @@ 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,
@@ -28475,9 +29438,17 @@ 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
@@ -28495,8 +29466,14 @@ 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.
+.new
+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.
+.wen
 The option defaults to always checking.
 
 The &(smtp)& transport has two OCSP-related options:
@@ -28544,8 +29521,66 @@ outgoing connection.
 
 
 
+.new
+.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.
+.wen
+
+
+
+
 .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
@@ -28577,6 +29612,11 @@ 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).
 
+.new
+If DANE validated the connection attempt then the value of the &%tls_sni%& option
+is forced to the domain part of the recipient address.
+.wen
+
 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`&.
@@ -28601,7 +29641,7 @@ 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.
 
@@ -28763,6 +29803,100 @@ Open-source PKI book, available online at
 .ecindex IIDencsmtp2
 
 
+.new
+.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
+.wen
+
 
 .section DANE "SECDANE"
 .cindex DANE
@@ -28780,7 +29914,7 @@ 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.
 
@@ -28796,7 +29930,12 @@ 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);
@@ -28837,19 +29976,29 @@ If you're not already using a private CA, or it doesn't meet these
 requirements, then we encourage you to avoid all these issues and use a public
 CA such as &url(https://letsencrypt.org/,Let's Encrypt) instead.
 
-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).
 
@@ -28883,7 +30032,9 @@ those who use &%hosts_require_ocsp%&, should consider the interaction with DANE
 
 For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%&
 and &%dane_require_tls_ciphers%&.
-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.
 
@@ -28908,12 +30059,14 @@ 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".
 
@@ -29563,8 +30716,8 @@ 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.
@@ -29793,7 +30946,7 @@ 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.
@@ -29802,7 +30955,7 @@ 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
@@ -30232,6 +31385,13 @@ 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"
@@ -30360,22 +31520,37 @@ 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"
@@ -30419,7 +31594,7 @@ 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
@@ -30776,7 +31951,7 @@ 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.
 
@@ -30796,7 +31971,9 @@ 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'&>
@@ -30887,8 +32064,9 @@ 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.
 
@@ -30918,8 +32096,8 @@ 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*&
@@ -30973,10 +32151,8 @@ 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.
 
-.new
 There is one possible option, &`case_insensitive`&.  If this is present then
 local parts are checked case-insensitively.
-.wen
 
 There are, of course, many legitimate messages that make use of blind (bcc)
 recipients. This check should not be used on its own for blocking messages.
@@ -31045,7 +32221,7 @@ 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
 
@@ -31103,8 +32279,8 @@ 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
@@ -31145,8 +32321,8 @@ 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 $dnslist_domain
 .endd
 This particular example is useful only in ACLs that are obeyed after the
 RCPT or DATA commands, when a sender address is available. If (for
@@ -31210,13 +32386,13 @@ dnslists = black.list.tld/a.domain::b.domain
 However, when the data for the list is obtained from a lookup, the second form
 is usually much more convenient. Consider this example:
 .code
-deny message  = The mail servers for the domain \
+deny dnslists = sbl.spamhaus.org/<|${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
@@ -31289,7 +32465,7 @@ 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
@@ -31475,12 +32651,12 @@ 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
@@ -31627,7 +32803,7 @@ 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
@@ -31670,12 +32846,12 @@ 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
 
@@ -31785,16 +32961,16 @@ 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
@@ -31843,6 +33019,15 @@ 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>>&.
+.new
+.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).
+.wen
 .endlist
 
 .cindex "verifying address" "differentiating failures"
@@ -31876,6 +33061,9 @@ connection, HELO, or MAIL).
 &%recipient%&: The RCPT command in a callout was rejected.
 .next
 &%postmaster%&: The postmaster check in a callout was rejected.
+.new
+.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
@@ -32205,6 +33393,38 @@ behaviour will be the same.
 
 
 
+.new
+.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.
+.wen
+
 .section "Sender address verification reporting" "SECTsenaddver"
 .cindex "verifying" "suppressing error details"
 See section &<<SECTaddressverification>>& for a general discussion of
@@ -32383,16 +33603,16 @@ 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
@@ -32584,6 +33804,13 @@ 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.
 
@@ -32922,13 +34149,13 @@ 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:
@@ -32937,13 +34164,13 @@ 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
 
 
@@ -33072,8 +34299,8 @@ 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
@@ -33105,9 +34332,9 @@ 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
@@ -33165,8 +34392,8 @@ 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%&.
 
@@ -33184,9 +34411,9 @@ 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
 
 
@@ -33270,13 +34497,22 @@ 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
@@ -33288,31 +34524,37 @@ 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:
@@ -33327,6 +34569,7 @@ 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.
@@ -33335,6 +34578,7 @@ 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
@@ -33345,6 +34589,7 @@ 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.
@@ -33372,23 +34617,27 @@ 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
@@ -33424,8 +34673,8 @@ 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
@@ -33492,7 +34741,10 @@ 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
@@ -33514,13 +34766,14 @@ 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 *)
@@ -34122,8 +35375,8 @@ 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%&
@@ -34135,6 +35388,15 @@ 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
@@ -34152,7 +35414,9 @@ 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
@@ -34160,12 +35424,16 @@ 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.
 
@@ -34484,20 +35752,20 @@ 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
@@ -35255,13 +36523,14 @@ 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
@@ -35657,7 +36926,8 @@ 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
@@ -36012,10 +37282,10 @@ 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
@@ -36103,7 +37373,8 @@ 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:
@@ -36111,10 +37382,10 @@ lists_post:
   domains = lists.example
   senders = ${if exists {/usr/lists/$local_part}\
              {lsearch;/usr/lists/$local_part}{*}}
-  file = /usr/lists/$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
 
 lists_closed:
@@ -36172,7 +37443,7 @@ 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
@@ -36223,7 +37494,7 @@ 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
@@ -36271,12 +37542,16 @@ 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$& variable.
+
+When the router runs, it looks up the local
 part in the file to find a new address (or list of addresses). The &%no_more%&
 setting ensures that if the lookup fails (leading to &%data%& being an empty
 string), Exim gives up on the address without trying any subsequent routers.
@@ -36305,7 +37580,7 @@ follows:
 .code
 my_mailboxes:
   driver = appendfile
-  file = /var/mail/$domain/$local_part
+  file = /var/mail/$domain_data/$local_part_data
   user = mail
 .endd
 This uses a directory of mailboxes for each domain. The &%user%& setting is
@@ -36345,7 +37620,7 @@ It runs a user's &_.forward_& file for all local parts of the form
 cases by testing the variable &$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
@@ -36360,9 +37635,9 @@ 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
@@ -36479,6 +37754,7 @@ 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,
@@ -37009,7 +38285,8 @@ 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
@@ -37136,7 +38413,7 @@ 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
@@ -37234,7 +38511,7 @@ 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
@@ -37278,6 +38555,7 @@ selection marked by asterisks:
 &`*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
 
@@ -37390,6 +38668,7 @@ 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"
@@ -37398,7 +38677,10 @@ 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
+.new
+&"=>"&, &"->"&, &"=="& and &"**"& lines.
+.wen
 The latter can be disabled by turning off the &%outgoing_interface%& option.
 .next
 .cindex log "incoming proxy address"
@@ -37432,7 +38714,6 @@ connection is unexpectedly dropped.
 &%millisec%&: Timestamps have a period and three decimal places of finer granularity
 appended to the seconds value.
 .next
-.new
 .cindex "log" "message id"
 &%msg_id%&: The value of the Message-ID: header.
 .next
@@ -37440,7 +38721,6 @@ appended to the seconds value.
 This will be either because the message is a bounce, or was submitted locally
 (submission mode) without one.
 The field identifier will have an asterix appended: &"id*="&.
-.wen
 .next
 .cindex "log" "outgoing interface"
 .cindex "log" "local interface"
@@ -37477,13 +38757,11 @@ 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.
 
-.new
 .cindex "pipelining" "early connection"
 If Exim is built with the SUPPORT_PIPE_CONNECT build option
 accept "L" fields have a period appended if the feature was
 offered but not used, or an asterisk appended if used.
 Delivery "L" fields have an asterisk appended if used.
-.wen
 
 .next
 .cindex "log" "queue run"
@@ -37683,8 +38961,17 @@ 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"
+.new
+&%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.
+.wen
+.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=.
@@ -37741,9 +39028,9 @@ 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
 
@@ -37841,10 +39128,8 @@ Match only frozen messages.
 .vitem &*-x*&
 Match only non-frozen messages.
 
-.new
 .vitem &*-G*&&~<&'queuename'&>
 Match only messages in the given queue.  Without this, the default queue is searched.
-.wen
 .endlist
 
 The following options control the format of the output:
@@ -38230,6 +39515,10 @@ for remote hosts
 .next
 &'ratelimit'&: the data for implementing the ratelimit ACL condition
 .next
+.new
+&'tls'&: TLS session resumption data
+.wen
+.next
 &'misc'&: other hints data
 .endlist
 
@@ -38247,7 +39536,7 @@ 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
@@ -38284,7 +39573,7 @@ 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
@@ -38333,7 +39622,7 @@ 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
@@ -39532,6 +40821,9 @@ 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%&
@@ -39640,11 +40932,11 @@ 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
@@ -39716,19 +41008,17 @@ 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,
-.new
 lowercased,
-.wen
 is put into the &%$dkim_domain%& expansion variable
 while expanding the remaining signing options.
 If it is empty after expansion, DKIM signing is not done,
 and no error will result even if &%dkim_strict%& is set.
 
-.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
@@ -39761,6 +41051,8 @@ 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.
@@ -39777,9 +41069,7 @@ Signers MUST use RSA keys of at least 1024 bits for all keys.
 Signers SHOULD use RSA keys of at least 2048 bits.
 .endd
 
-.new
 EC keys for DKIM are defined by RFC 8463.
-.wen
 They are considerably smaller than RSA keys for equivalent protection.
 As they are a recent development, users should consider dual-signing
 (by setting a list of selectors, and an expansion for this option)
@@ -39799,12 +41089,10 @@ 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
 
-.new
 Exim also supports an alternate format
 of Ed25519 keys in DNS which was a candidate during development
 of the standard, but not adopted.
 A future release will probably drop that support.
-.wen
 
 .option dkim_hash smtp string&!! sha256
 Can be set to any one of the supported hash methods, which are:
@@ -39837,7 +41125,7 @@ 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.
 
@@ -39849,16 +41137,17 @@ 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.
 
@@ -39878,15 +41167,24 @@ RFC 6376 lists these tags as RECOMMENDED.
 
 Verification of DKIM signatures in SMTP incoming email is done for all
 messages for which an ACL control &%dkim_disable_verify%& has not been set.
+.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.
+&%authresults%& expansion item.
+
+For most purposes the default option settings suffice and the remainder
+of this section can be ignored.
 
-The results of that verification are then made available to the
+The results of verification are made available to the
 &%acl_smtp_dkim%& ACL, which can examine and modify them.
-By default, this ACL is called once for each
-syntactically(!) correct signature in the incoming message.
 A missing ACL definition defaults to accept.
+By default, the ACL is called once for each
+syntactically(!) correct signature in the incoming message.
 If any ACL call does not accept, the message is not accepted.
 If a cutthrough delivery was in progress for the message, that is
 summarily dropped (having wasted the transmission effort).
@@ -39897,11 +41195,11 @@ containing the signature status and its details are set up during the
 runtime of the ACL.
 
 Calling the ACL only for existing signatures is not sufficient to build
-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
@@ -39927,19 +41225,17 @@ 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.
 
-.new
 Note that if the option is set using untrustworthy data
 (such as the From: header)
 care should be taken to force lowercase for domains
 and for the domain part if identities.
 The default setting can be regarded as trustworthy in this respect.
-.wen
 
 If multiple signatures match a domain (or identity), the ACL is called once
 for each matching signature.
 
 
-Inside the &%acl_smtp_dkim%&, the following expansion variables are
+Inside the DKIM ACL, the following expansion variables are
 available (from most to least important):
 
 
@@ -40033,8 +41329,10 @@ 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'.
@@ -40091,6 +41389,8 @@ 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
@@ -40098,9 +41398,8 @@ 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
 
@@ -40115,10 +41414,10 @@ 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;
@@ -40130,10 +41429,10 @@ 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
@@ -40149,8 +41448,12 @@ 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.
@@ -40164,7 +41467,7 @@ 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"
@@ -40213,13 +41516,16 @@ 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:
 
@@ -40254,8 +41560,11 @@ 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
 
 
@@ -40266,9 +41575,9 @@ 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:
@@ -40301,7 +41610,9 @@ 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}}
@@ -40309,7 +41620,343 @@ 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"
+
+.new
+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
+
+
+.wen
+
+
+
+.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
+
 
 
 
@@ -40358,7 +42005,8 @@ 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
@@ -40390,8 +42038,8 @@ 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
 
 
@@ -40487,6 +42135,7 @@ 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
@@ -40533,22 +42182,27 @@ 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.
 
 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.
+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.
@@ -40642,16 +42296,18 @@ 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.
 
@@ -40670,14 +42326,16 @@ 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: &$event_defer_errno$&.