X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/28b3821f89f89670a08603c50662d468e82510ad..ea0d0cfba5fa9267c0f82af617f2094bc7545745:/doc/doc-docbook/spec.xfpt

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index 2018af992..44f9d26ff 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 "4.87"
+.set previousversion "4.89"
 .include ./local_params
 
 .set ACL "access control lists (ACLs)"
 .set I   "    "
 
 .macro copyyear
-2016
+2017
 .endmacro
 
 . /////////////////////////////////////////////////////////////////////////////
@@ -436,6 +436,7 @@ directory are:
 .row &_filter.txt_&          "specification of the filter language"
 .row &_Exim3.upgrade_&       "upgrade notes from release 2 to release 3"
 .row &_Exim4.upgrade_&       "upgrade notes from release 3 to release 4"
+.row &_openssl.txt_&         "installing a current OpenSSL release"
 .endtable
 
 The main specification and the specification of the filtering language are also
@@ -2627,6 +2628,8 @@ users to set envelope senders.
 
 .cindex "&'From:'& header line"
 .cindex "&'Sender:'& header line"
+.cindex "header lines" "From:"
+.cindex "header lines" "Sender:"
 For a trusted user, there is never any check on the contents of the &'From:'&
 header line, and a &'Sender:'& line is never added. Furthermore, any existing
 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
@@ -3825,11 +3828,17 @@ 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 &%-MCG%&
+.vitem &%-MCG%&&~<&'queue&~name'&>
 .oindex "&%-MCG%&"
 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 an
-alternate queue is used, named by the following option.
+alternate queue is used, named by the following argument.
+
+.vitem &%-MCK%&
+.oindex "&%-MCK%&"
+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 an
+remote host supports the ESMTP &_CHUNKING_& extension.
 
 .vitem &%-MCP%&
 .oindex "&%-MCP%&"
@@ -3859,6 +3868,15 @@ 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 &%-MCt%&&~<&'IP&~address'&>&~<&'port'&>
+.oindex "&%-MCt%&"
+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
+connection is being proxied by a parent process for handling TLS encryption.
+The pair of arguments give the local address and port being proxied.
+.wen
+
 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
 .oindex "&%-Mc%&"
 .cindex "hints database" "not overridden by &%-Mc%&"
@@ -4377,7 +4395,8 @@ relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
 and &%-S%& options).
 
 .cindex "queue runner" "description of operation"
-The &%-q%& option starts one queue runner process. This scans the queue of
+If other commandline options do not specify an action,
+the &%-q%& option starts one queue runner process. This scans the queue of
 waiting messages, and runs a delivery process for each one in turn. It waits
 for each delivery process to finish before starting the next one. A delivery
 process may not actually do any deliveries if the retry times for the addresses
@@ -4462,15 +4481,25 @@ The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
 be done. If a message requires any remote deliveries, it remains on the queue
 for later delivery.
 
-.vitem &%-q[q][i][f[f]][l][G<name>]%&
+.vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
 .oindex "&%-qG%&"
 .cindex queue named
 .cindex "named queues"
 .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.
-Because the name is the remainder of the option string, any
-periodic-run interval must be given as a separate &%-q%& option.
+The name should not contain a &'/'& character.
+For a periodic queue run (see below)
+append to the name a slash and a time value.
+
+If other commandline options specify an action, a &'-qG<name>'& option
+will specify a queue to operate on.
+For example:
+.code
+exim -bp -qGquarantine
+mailq -qGquarantine
+exim -qGoffpeak -Rf @special.domain.example
+.endd
 
 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
 When scanning the queue, Exim can be made to skip over messages whose ids are
@@ -4907,7 +4936,9 @@ using this syntax:
 .endd
 on a line by itself. Double quotes round the file name are optional. If you use
 the first form, a configuration error occurs if the file does not exist; the
-second form does nothing for non-existent files. In all cases, an absolute file
+second form does nothing for non-existent files.
+The first form allows a relative name. It is resolved relative to
+the directory of the including file. For the second form an absolute file
 name is required.
 
 Includes may be nested to any depth, but remember that Exim reads its
@@ -5014,6 +5045,31 @@ address lists. In Exim 4 these are handled better by named lists &-- see
 section &<<SECTnamedlists>>&.
 
 
+.section "Builtin macros" "SECTbuiltinmacros"
+Exim defines some macros depending on facilities available, which may
+differ due to build-time definitions and from one release to another.
+All of these macros start with an underscore.
+They can be used to conditionally include parts of a configuration
+(see below).
+
+The following classes of macros are defined:
+.display
+&` _HAVE_*                    `&  build-time defines
+&` _DRIVER_ROUTER_*           `&  router drivers
+&` _DRIVER_TRANSPORT_*        `&  transport drivers
+&` _DRIVER_AUTHENTICATOR_*    `&  authenticator drivers
+&` _OPT_MAIN_*                `&  main config options
+&` _OPT_ROUTERS_*             `&  generic router options
+&` _OPT_TRANSPORTS_*          `&  generic transport options
+&` _OPT_AUTHENTICATORS_*      `&  generic authenticator options
+&` _OPT_ROUTER_*_*            `&  private router options
+&` _OPT_TRANSPORT_*_*         `&  private transport options
+&` _OPT_AUTHENTICATOR_*_*     `&  private authenticator options
+.endd
+
+Use an &"exim -bP macros"& command to get the list of macros.
+
+
 .section "Conditional skips in the configuration file" "SECID46"
 .cindex "configuration file" "conditional skips"
 .cindex "&`.ifdef`&"
@@ -5117,7 +5173,9 @@ with the characters &"0x"&, in which case the remainder is interpreted as a
 hexadecimal number.
 
 If an integer value is followed by the letter K, it is multiplied by 1024; if
-it is followed by the letter M, it is multiplied by 1024x1024. When the values
+it is followed by the letter M, it is multiplied by 1024x1024;
+if by the letter G, 1024x1024x1024.
+When the values
 of integer option settings are output, values which are an exact multiple of
 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
 and M. The printing style is independent of the actual input format that was
@@ -6245,7 +6303,9 @@ Chapter &<<CHAPplaintext>>& covers both.
 Exim supports the use of regular expressions in many of its options. It
 uses the PCRE regular expression library; this provides regular expression
 matching that is compatible with Perl 5. The syntax and semantics of
-regular expressions is discussed in many Perl reference books, and also in
+regular expressions is discussed in
+online Perl manpages, in
+many Perl reference books, and also in
 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
 
@@ -6686,8 +6746,8 @@ PostgreSQL database. See section &<<SECTsql>>&.
 .next
 .cindex "Redis lookup type"
 .cindex lookup Redis
-&(redis)&: The format of the query is an SQL statement that is passed to a
-Redis database. See section &<<SECTsql>>&.
+&(redis)&: The format of the query is either a simple get or simple set,
+passed to a Redis database. See section &<<SECTsql>>&.
 
 .next
 .cindex "sqlite lookup type"
@@ -7065,7 +7125,7 @@ Retries for the dnsdb lookup can be controlled by a retry modifier.
 The form if &"retry_VAL"& where VAL is an integer.
 The default count is set by the main configuration option &%dns_retry%&.
 
-.cindex cacheing "of dns lookup"
+.cindex caching "of dns lookup"
 .cindex TTL "of dns lookup"
 .cindex DNS TTL
 Dnsdb lookup results are cached within a single process (and its children).
@@ -7760,6 +7820,17 @@ are rejected after a timeout period, during which the SQLite library
 waits for the lock to be released. In Exim, the default timeout is set
 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
 option.
+
+.section "More about Redis" "SECTredis"
+.cindex "lookup" "Redis"
+.cindex "redis lookup type"
+Redis is a non-SQL database. Commands are simple get and set.
+Examples:
+.code
+${lookup redis{set keyname ${quote_redis:objvalue plus}}}
+${lookup redis{get keyname}}
+.endd
+
 .ecindex IIDfidalo1
 .ecindex IIDfidalo2
 
@@ -7792,10 +7863,8 @@ domain, host, address and local part lists.
 .cindex "expansion" "of lists"
 Each list is expanded as a single string before it is used.
 
-.new
 &'Exception: the router headers_remove option, where list-item
 splitting is done before string-expansion.'&
-.wen
 
 The result of
 expansion must be a list, possibly containing empty items, which is split up
@@ -9062,7 +9131,7 @@ If the ACL returns defer the result is a forced-fail.  Otherwise the expansion f
 
 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
        {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
-.cindex "expansion" "extracting cerificate fields"
+.cindex "expansion" "extracting certificate fields"
 .cindex "&%certextract%&" "certificate fields"
 .cindex "certificate" "extracting fields"
 The <&'certificate'&> must be a variable of type certificate.
@@ -9196,8 +9265,8 @@ The environment is adjusted by the &%keep_environment%& and
 .cindex "&%extract%&" "substrings by key"
 The key and <&'string1'&> are first expanded separately. Leading and trailing
 white space is removed from the key (but not from any of the strings). The key
-must not consist entirely of digits. The expanded <&'string1'&> must be of the
-form:
+must not be empty and must not consist entirely of digits.
+The expanded <&'string1'&> must be of the form:
 .display
 <&'key1'&> = <&'value1'&>  <&'key2'&> = <&'value2'&> ...
 .endd
@@ -9379,12 +9448,15 @@ message, and any that are added by an ACL statement or by a system
 filter. Header lines that are added to a particular copy of a message by a
 router or transport are not accessible.
 
-For incoming SMTP messages, no header lines are visible in ACLs that are obeyed
-before the DATA ACL, because the header structure is not set up until the
-message is received. Header lines that are added in a RCPT ACL (for example)
+For incoming SMTP messages, no header lines are visible in
+ACLs that are obeyed before the data phase completes,
+because the header structure is not set up until the message is received.
+They are visible in DKIM, PRDR and DATA ACLs.
+Header lines that are added in a RCPT ACL (for example)
 are saved until the message's incoming header lines are available, at which
-point they are added. When a DATA ACL is running, however, header lines added
-by earlier ACLs are visible.
+point they are added.
+When any of the above ACLs ar
+running, however, header lines added by earlier ACLs are visible.
 
 Upper case and lower case letters are synonymous in header names. If the
 following character is white space, the terminating colon may be omitted, but
@@ -9711,7 +9783,7 @@ locks out the use of this expansion item in filter files.
 
 
 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
-        {*&<&'timeout'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
+        {*&<&'options'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
 .cindex "expansion" "inserting from a socket"
 .cindex "socket, use of in expansion"
 .cindex "&%readsocket%& expansion item"
@@ -9741,6 +9813,15 @@ extend what can be done. Firstly, you can vary the timeout. For example:
 .code
 ${readsocket{/socket/name}{request string}{3s}}
 .endd
+The third argument is a list of options, of which the first element is the timeout
+and must be present if the argument is given.
+Further elements are options of form &'name=value'&.
+One option type is currently recognised, defining whether (the default)
+or not a shutdown is done on the connection after sending the request.
+Example, to not do so (preferred, eg. by some webservers):
+.code
+${readsocket{/socket/name}{request string}{3s:shutdown=no}}
+.endd
 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
 turns them into spaces:
@@ -10073,6 +10154,19 @@ Last:user@example.com
 user@example.com
 .endd
 
+.vitem &*${base32:*&<&'digits'&>&*}*&
+.cindex "&%base32%& expansion item"
+.cindex "expansion" "conversion to base 32"
+The string must consist entirely of decimal digits. The number is converted to
+base 32 and output as a (empty, for zero) string of characters.
+Only lowercase letters are used.
+
+.vitem &*${base32d:*&<&'base-32&~digits'&>&*}*&
+.cindex "&%base32d%& expansion item"
+.cindex "expansion" "conversion to base 32"
+The string must consist entirely of base-32 digits.
+The number is converted to decimal and output as a string.
+
 .vitem &*${base62:*&<&'digits'&>&*}*&
 .cindex "&%base62%& expansion item"
 .cindex "expansion" "conversion to base 62"
@@ -10124,6 +10218,13 @@ escape sequences starting with a backslash. Whether characters with the most
 significant bit set (so-called &"8-bit characters"&) count as printing or not
 is controlled by the &%print_topbitchars%& option.
 
+.vitem &*${escape8bit:*&<&'string'&>&*}*&
+.cindex "expansion" "escaping 8-bit characters"
+.cindex "&%escape8bit%& expansion item"
+If the string contains and characters with the most significant bit set,
+they are converted to escape sequences starting with a backslash.
+Backslashes and DEL characters are also converted.
+
 
 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
 .cindex "expansion" "expression evaluation"
@@ -10497,7 +10598,7 @@ variables or headers inside regular expressions.
 .cindex "SHA-1 hash"
 .cindex "expansion" "SHA-1 hashing"
 .cindex certificate fingerprint
-.cindex "&%sha2%& expansion item"
+.cindex "&%sha1%& expansion item"
 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
 it as a 40-digit hexadecimal number, in which any letters are in upper case.
 
@@ -10505,16 +10606,34 @@ If the string is a single variable of type certificate,
 returns the SHA-1 hash fingerprint of the certificate.
 
 
-.vitem &*${sha256:*&<&'certificate'&>&*}*&
+.vitem &*${sha256:*&<&'string'&>&*}*&
 .cindex "SHA-256 hash"
 .cindex certificate fingerprint
 .cindex "expansion" "SHA-256 hashing"
 .cindex "&%sha256%& expansion item"
-The &%sha256%& operator computes the SHA-256 hash fingerprint of the
-certificate,
+The &%sha256%& operator computes the SHA-256 hash value of the string
 and returns
 it as a 64-digit hexadecimal number, in which any letters are in upper case.
-Only arguments which are a single variable of certificate type are supported.
+
+If the string is a single variable of type certificate,
+returns the SHA-256 hash fingerprint of the certificate.
+
+
+.vitem &*${sha3:*&<&'string'&>&*}*& &&&
+       &*${sha3_<n>:*&<&'string'&>&*}*&
+.cindex "SHA3 hash"
+.cindex "expansion" "SHA3 hashing"
+.cindex "&%sha3%& expansion item"
+The &%sha3%& operator computes the SHA3-256 hash value of the string
+and returns
+it as a 64-digit hexadecimal number, in which any letters are in upper case.
+
+If a number is appended, separated by an underbar, it specifies
+the output length.  Values of 224, 256, 384 and 512 are accepted;
+with 256 being the default.
+
+The &%sha3%& expansion item is only supported if Exim has been
+compiled with GnuTLS 3.5.0 or later.
 
 
 .vitem &*${stat:*&<&'string'&>&*}*&
@@ -12122,7 +12241,7 @@ normally the gid of the Exim user.
 .cindex "uid (user id)" "of originating user"
 .cindex "sender" "uid"
 .vindex "&$caller_uid$&"
-.vindex "&$originaltor_uid$&"
+.vindex "&$originator_uid$&"
 The value of &$caller_uid$& that was set when the message was received. For
 messages received via the command line, this is the uid of the sending user.
 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
@@ -12163,16 +12282,14 @@ a single-component name, Exim calls &[gethostbyname()]& (or
 qualified host name. See also &$smtp_active_hostname$&.
 
 
-.new
 .vitem &$proxy_external_address$& &&&
        &$proxy_external_port$& &&&
        &$proxy_local_address$& &&&
        &$proxy_local_port$& &&&
        &$proxy_session$&
 These variables are only available when built with Proxy Protocol
-or Socks5 support
+or SOCKS5 support.
 For details see chapter &<<SECTproxyInbound>>&.
-.wen
 
 .vitem &$prdr_requested$&
 .cindex "PRDR" "variable for"
@@ -12203,6 +12320,12 @@ The value set for the &%qualify_domain%& option in the configuration file.
 The value set for the &%qualify_recipient%& option in the configuration file,
 or if not set, the value of &$qualify_domain$&.
 
+.vitem &$queue_name$&
+.vindex &$queue_name$&
+.cindex "named queues"
+.cindex queues named
+The name of the spool queue in use; empty for the default queue.
+
 .vitem &$rcpt_count$&
 .vindex "&$rcpt_count$&"
 When a message is being received by SMTP, this variable contains the number of
@@ -12515,6 +12638,11 @@ validating resolver (e.g. unbound, or bind with suitable configuration).
 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
 mechanism in the list, then this variable will be false.
 
+This requires that your system resolver library support EDNS0 (and that
+DNSSEC flags exist in the system headers).  If the resolver silently drops
+all EDNS0 options, then this will have no effect.  OpenBSD's asr resolver
+is known to currently ignore EDNS0, documented in CAVEATS of asr_run(3).
+
 
 .vitem &$sender_host_name$&
 .vindex "&$sender_host_name$&"
@@ -12736,7 +12864,7 @@ If TLS has not been negotiated, the value will be 0.
 
 .vitem &$tls_in_ourcert$&
 .vindex "&$tls_in_ourcert$&"
-.cindex certificate veriables
+.cindex certificate variables
 This variable refers to the certificate presented to the peer of an
 inbound connection when the message was received.
 It is only useful as the argument of a
@@ -12791,7 +12919,7 @@ When a message is received from a remote host over an encrypted SMTP
 connection, this variable is set to the cipher suite that was negotiated, for
 example DES-CBC3-SHA. In other circumstances, in particular, for message
 received over unencrypted connections, the variable is empty. Testing
-&$tls_cipher$& for emptiness is one way of distinguishing between encrypted and
+&$tls_in_cipher$& for emptiness is one way of distinguishing between encrypted and
 non-encrypted connections during ACL processing.
 
 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
@@ -12926,8 +13054,7 @@ or external command, as described above. It is also used during a
 
 .vitem &$verify_mode$&
 .vindex "&$verify_mode$&"
-While a router or transport is being run in verify mode
-or for cutthrough delivery,
+While a router or transport is being run in verify mode or for cutthrough delivery,
 contains "S" for sender-verification or "R" for recipient-verification.
 Otherwise, empty.
 
@@ -13003,16 +13130,14 @@ overriding the setting of &%perl_at_start%&.
 There is also a command line option &%-pd%& (for delay) which suppresses the
 initial startup, even if &%perl_at_start%& is set.
 
-.new
 .ilist
 .oindex "&%perl_taintmode%&"
 .cindex "Perl" "taintmode"
 To provide more security executing Perl code via the embedded Perl
-interpeter, the &%perl_taintmode%& option can be set. This enables the
+interpreter, the &%perl_taintmode%& option can be set. This enables the
 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.
-.wen
 
 
 .section "Calling Perl subroutines" "SECID86"
@@ -13439,6 +13564,7 @@ listed in more than one group.
 .section "Miscellaneous" "SECID96"
 .table2
 .row &%bi_command%&                  "to run for &%-bi%& command line option"
+.row &%debug_store%&                 "do extra internal checks"
 .row &%disable_ipv6%&                "do no IPv6 processing"
 .row &%keep_malformed%&              "for broken files &-- should not happen"
 .row &%localhost_number%&            "for unique message ids in clusters"
@@ -13492,6 +13618,7 @@ listed in more than one group.
 .row &%slow_lookup_log%&             "control logging of slow DNS lookups"
 .row &%syslog_duplication%&          "controls duplicate log lines on syslog"
 .row &%syslog_facility%&             "set syslog &""facility""& field"
+.row &%syslog_pid%&                  "pid in syslog lines"
 .row &%syslog_processname%&          "set syslog &""ident""& field"
 .row &%syslog_timestamp%&            "timestamp syslog lines"
 .row &%write_rejectlog%&             "control use of message log"
@@ -13754,6 +13881,7 @@ See also the &'Policy controls'& section above.
 .table2
 .row &%accept_8bitmime%&             "advertise 8BITMIME"
 .row &%auth_advertise_hosts%&        "advertise AUTH to these hosts"
+.row &%chunking_advertise_hosts%&    "advertise CHUNKING to these hosts"
 .row &%dsn_advertise_hosts%&         "advertise DSN extensions to these hosts"
 .row &%ignore_fromline_hosts%&       "allow &""From ""& from these hosts"
 .row &%ignore_fromline_local%&       "allow &""From ""& from local SMTP"
@@ -13927,6 +14055,7 @@ acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
 .option acl_smtp_dkim main string&!! unset
 .cindex DKIM "ACL for"
 This option defines the ACL that is run for each DKIM signature
+(by default, or as specified in the dkim_verify_signers option)
 of a received message.
 See chapter &<<CHAPdkim>>& for further details.
 
@@ -14243,11 +14372,11 @@ $primary_hostname-$tod_epoch-testing
 See section &<<CALLaddparcall>>& for details of how this value is used.
 
 
-.option check_log_inodes main integer 0
+.option check_log_inodes main integer 100
 See &%check_spool_space%& below.
 
 
-.option check_log_space main integer 0
+.option check_log_space main integer 10M
 See &%check_spool_space%& below.
 
 .oindex "&%check_rfc2047_length%&"
@@ -14262,11 +14391,11 @@ of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
 set false, Exim recognizes encoded words of any length.
 
 
-.option check_spool_inodes main integer 0
+.option check_spool_inodes main integer 100
 See &%check_spool_space%& below.
 
 
-.option check_spool_space main integer 0
+.option check_spool_space main integer 10M
 .cindex "checking disk space"
 .cindex "disk space, checking"
 .cindex "spool directory" "checking space"
@@ -14277,7 +14406,7 @@ message is accepted.
 .vindex "&$log_space$&"
 .vindex "&$spool_inodes$&"
 .vindex "&$spool_space$&"
-When any of these options are set, they apply to all incoming messages. If you
+When any of these options are nonzero, they apply to all incoming messages. If you
 want to apply different checks to different kinds of message, you can do so by
 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
 &$spool_space$& in an ACL with appropriate additional conditions.
@@ -14286,7 +14415,7 @@ testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
 either value is greater than zero, for example:
 .code
-check_spool_space = 10M
+check_spool_space = 100M
 check_spool_inodes = 100
 .endd
 The spool partition is the one that contains the directory defined by
@@ -14305,12 +14434,32 @@ SIZE parameter on the MAIL command, its value is added to the
 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
 
 The values for &%check_spool_space%& and &%check_log_space%& are held as a
-number of kilobytes. If a non-multiple of 1024 is specified, it is rounded up.
+number of kilobytes (though specified in bytes).
+If a non-multiple of 1024 is specified, it is rounded up.
 
 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
 failure a message is written to stderr and Exim exits with a non-zero code, as
 it obviously cannot send an error message of any kind.
 
+There is a slight performance penalty for these checks.
+Versions of Exim preceding 4.88 had these disabled by default;
+high-rate installations confident they will never run out of resources
+may wish to deliberately disable them.
+
+.option chunking_advertise_hosts main "host list&!!" *
+.cindex CHUNKING advertisement
+.cindex "RFC 3030" "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.
+
+.option debug_store main boolean &`false`&
+.cindex debugging "memory corruption"
+.cindex memory debugging
+This option, when true, enables extra checking in Exim's internal memory
+management.  For use when a memory corruption issue is being investigated,
+it should normally be left as default.
+
 .option daemon_smtp_ports main string &`smtp`&
 .cindex "port" "for daemon"
 .cindex "TCP/IP" "setting listening ports"
@@ -14332,6 +14481,7 @@ See &%daemon_startup_retries%&.
 .option delay_warning main "time list" 24h
 .cindex "warning of delay"
 .cindex "delay warning, specifying"
+.cindex "queue" "delay warning"
 When a message is delayed, Exim sends a warning message to the sender at
 intervals specified by this option. The data is a colon-separated list of times
 after which to send warning messages. If the value of the option is an empty
@@ -14559,6 +14709,7 @@ record in the authoritative section is used instead.
 .option dns_use_edns0 main integer -1
 .cindex "DNS" "resolver options"
 .cindex "DNS" "EDNS0"
+.cindex "DNS" "OpenBSD
 If this option is set to a non-negative number then Exim will initialise the
 DNS resolver library to either use or not use EDNS0 extensions, overriding
 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
@@ -14566,6 +14717,10 @@ on.
 
 If the resolver library does not support EDNS0 then this option has no effect.
 
+OpenBSD's asr resolver routines are known to ignore the EDNS0 option; this
+means that DNSSEC will not work with Exim on that platform either, unless Exim
+is linked against an alternative DNS client library.
+
 
 .option drop_cr main boolean false
 This is an obsolete option that is now a no-op. It used to affect the way Exim
@@ -14664,7 +14819,7 @@ not used.
 .option event_action main string&!! unset
 .cindex events
 This option declares a string to be expanded for Exim's events mechanism.
-For details see &<<CHAPevents>>&.
+For details see chapter &<<CHAPevents>>&.
 
 
 .option exim_group main string "compile-time configured"
@@ -15015,7 +15170,7 @@ If the &%smtp_connection%& log selector is not set, this option has no effect.
 .option hosts_proxy main "host list&!!" unset
 .cindex proxy "proxy protocol"
 This option enables use of Proxy Protocol proxies for incoming
-connections.  For details see &<<SECTproxyInbound>>&.
+connections.  For details see section &<<SECTproxyInbound>>&.
 
 
 .option hosts_treat_as_local main "domain list&!!" unset
@@ -15189,6 +15344,7 @@ connecting on a regular LDAP port.  This is the LDAP equivalent of SMTP's
 of SSL-on-connect.
 In the event of failure to negotiate TLS, the action taken is controlled
 by &%ldap_require_cert%&.
+This option is ignored for &`ldapi`& connections.
 
 
 .option ldap_version main integer unset
@@ -15913,7 +16069,7 @@ large list. In most situations, &%queue_run_in_order%& should not be set.
 
 
 
-.option queue_run_max main integer 5
+.option queue_run_max main integer&!! 5
 .cindex "queue runner" "maximum number of"
 This controls the maximum number of queue runner processes that an Exim daemon
 can run simultaneously. This does not mean that it starts them all at once,
@@ -15928,6 +16084,11 @@ the limit, allowing any number of simultaneous queue runner processes to be
 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"
+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"
@@ -16600,7 +16761,7 @@ example, instead of &"Administrative prohibition"&, it might give:
 .option smtputf8_advertise_hosts main "host list&!!" *
 .cindex "SMTPUTF8" "advertising"
 When Exim is built with support for internationalised mail names,
-the availability therof is advertised in
+the availability thereof is advertised in
 response to EHLO only to those client hosts that match this option. See
 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
 
@@ -16721,6 +16882,15 @@ If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
 details of Exim's logging.
 
 
+.option syslog_pid main boolean true
+.cindex "syslog" "pid"
+If &%syslog_pid%& is set false, the PID on Exim's log lines are
+omitted when these lines are sent to syslog. (Syslog normally prefixes
+the log lines with the PID of the logging process automatically.) You need
+to enable the &`+pid`& log selector item, if you want Exim to write it's PID
+into the logs.) See chapter &<<CHAPlog>>& for details of Exim's logging.
+
+
 
 .option syslog_processname main string &`exim`&
 .cindex "syslog" "process name; setting"
@@ -16748,6 +16918,7 @@ generates any deliveries to files or pipes, or any new mail messages, the
 appropriate &%system_filter_..._transport%& option(s) must be set, to define
 which transports are to be used. Details of this facility are given in chapter
 &<<CHAPsystemfilter>>&.
+A forced expansion failure results in no filter operation.
 
 
 .option system_filter_directory_transport main string&!! unset
@@ -16880,10 +17051,8 @@ if the OpenSSL build supports TLS extensions and the TLS client sends the
 Server Name Indication extension, then this option and others documented in
 &<<SECTtlssni>>& will be re-expanded.
 
-.new
 If this option is unset or empty a fresh self-signed certificate will be
 generated for every connection.
-.wen
 
 .option tls_crl main string&!! unset
 .cindex "TLS" "server certificate revocation list"
@@ -16920,7 +17089,13 @@ larger prime than requested.
 The value of this option is expanded and indicates the source of DH parameters
 to be used by Exim.
 
-If it is a filename starting with a &`/`&, then it names a file from which DH
+&*Note: The Exim Maintainers strongly recommend 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.
+
+If &%tls_dhparam%& is a filename starting with a &`/`&,
+then it names a file from which DH
 parameters should be loaded.  If the file exists, it should hold a PEM-encoded
 PKCS#3 representation of the DH prime.  If the file does not exist, for
 OpenSSL it is an error.  For GnuTLS, Exim will attempt to create the file and
@@ -16937,22 +17112,36 @@ does not exist, Exim will attempt to create it.
 See section &<<SECTgnutlsparam>>& for further details.
 
 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
-a default DH prime; the default is the 2048 bit prime described in section
+a default DH prime; the default is Exim-specific but lacks verifiable provenance.
+
+In older versions of Exim the default was the 2048 bit prime described in section
 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
 in IKE is assigned number 23.
 
 Otherwise, the option must expand to the name used by Exim for any of a number
-of DH primes specified in RFC 2409, RFC 3526 and RFC 5114.  As names, Exim uses
-"ike" followed by the number used by IKE, of "default" which corresponds to
-"ike23".
+of DH primes specified in RFC 2409, RFC 3526, RFC 5114, RFC 7919, or from other
+sources.  As names, Exim uses a standard specified name, else "ike" followed by
+the number used by IKE, or "default" which corresponds to
+&`exim.dev.20160529.3`&.
 
-The available primes are:
+The available standard primes are:
+&`ffdhe2048`&, &`ffdhe3072`&, &`ffdhe4096`&, &`ffdhe6144`&, &`ffdhe8192`&,
 &`ike1`&, &`ike2`&, &`ike5`&,
 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
-&`ike22`&, &`ike23`& (aka &`default`&) and &`ike24`&.
+&`ike22`&, &`ike23`& and &`ike24`&.
+
+The available additional primes are:
+&`exim.dev.20160529.1`&, &`exim.dev.20160529.2`& and &`exim.dev.20160529.3`&.
 
 Some of these will be too small to be accepted by clients.
 Some may be too large to be accepted by clients.
+The open cryptographic community has suspicions about the integrity of some
+of the later IKE values, which led into RFC7919 providing new fixed constants
+(the "ffdhe" identifiers).
+
+At this point, all of the "ike" values should be considered obsolete;
+they're still in Exim to avoid breaking unusual configurations, but are
+candidates for removal the next time we have backwards-incompatible changes.
 
 The TLS protocol does not negotiate an acceptable size for this; clients tend
 to hard-drop connections if what is offered by the server is unacceptable,
@@ -16970,17 +17159,20 @@ prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
 acceptable bound from 1024 to 2048.
 
 
-.option tls_eccurve main string&!! prime256v1
+.option tls_eccurve main string&!! &`auto`&
 .cindex TLS "EC cryptography"
-If built with a recent-enough version of OpenSSL,
-this option selects a EC curve for use by Exim.
+This option selects a EC curve for use by Exim when used with OpenSSL.
+It has no effect when Exim is used with GnuTLS.
+
+After expansion it must contain a valid EC curve parameter, such as
+&`prime256v1`&, &`secp384r1`&, or &`P-512`&. Consult your OpenSSL manual
+for valid selections.
 
-Curve names of the form &'prime256v1'& are accepted.
-For even more-recent library versions, names of the form &'P-512'&
-are also accepted, plus the special value &'auto'&
-which tells the library to choose.
+For OpenSSL versions before (and not including) 1.0.2, the string
+&`auto`& selects &`prime256v1`&. For more recent OpenSSL versions
+&`auto`& tells the library to choose.
 
-If the option is set to an empty string, no EC curves will be enabled.
+If the option expands to an empty string, no EC curves will be enabled.
 
 
 .option tls_ocsp_file main string&!! unset
@@ -17518,7 +17710,7 @@ This applies to all of the SRV, MX, AAAA, A lookup sequence.
 .cindex "DNSSEC" "MX lookup"
 .cindex "security" "MX lookup"
 .cindex "DNS" "DNSSEC"
-DNS lookups for domains matching &%dnssec_request_domains%& will be done with
+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.
@@ -19819,12 +20011,17 @@ list1:   :include:/opt/lists/list1
 .endd
 .next
 .cindex "address redirection" "to black hole"
-Sometimes you want to throw away mail to a particular local part. Making the
-&%data%& option expand to an empty string does not work, because that causes
-the router to decline. Instead, the alias item
+.cindex "delivery" "discard"
+.cindex "delivery" "blackhole"
 .cindex "black hole"
 .cindex "abandoning mail"
-&':blackhole:'& can be used. It does what its name implies. No delivery is
+Sometimes you want to throw away mail to a particular local part.  Making the
+&%data%& option expand to an empty string does not work, because that causes
+the router to decline. Instead, the alias item
+.code
+:blackhole:
+.endd
+can be used. It does what its name implies. No delivery is
 done, and no error message is generated. This has the same effect as specifying
 &_/dev/null_& as a destination, but it can be independently disabled.
 
@@ -20744,7 +20941,7 @@ resent to other recipients.
 .option event_action transports string&!! unset
 .cindex events
 This option declares a string to be expanded for Exim's events mechanism.
-For details see &<<CHAPevents>>&.
+For details see chapter &<<CHAPevents>>&.
 
 
 .option group transports string&!! "Exim group"
@@ -20794,7 +20991,7 @@ is forced to fail, no action is taken. Other expansion failures are treated as
 errors and cause the delivery to be deferred.
 
 Unlike most options, &%headers_remove%& can be specified multiple times
-for a router; all listed headers are removed.
+for a transport; all listed headers are removed.
 
 &*Warning*&: Because of the separate expansion of the list items,
 items that contain a list separator must have it doubled.
@@ -20859,7 +21056,7 @@ The control does not apply to shadow transports.
 
 .cindex "hints database" "transport concurrency control"
 Exim implements this control by means of a hints database in which a record is
-incremented whenever a transport process is beaing created. The record
+incremented whenever a transport process is being created. The record
 is decremented and possibly removed when the process terminates.
 Obviously there is scope for
 records to get left lying around if there is a system or program crash. To
@@ -23116,12 +23313,10 @@ message_suffix =
 &`\n`& to &`\r\n`& in &%message_suffix%&.
 
 
-.option path pipe string "see below"
-This option specifies the string that is set up in the PATH environment
-variable of the subprocess. The default is:
-.code
-/bin:/usr/bin
-.endd
+.option path pipe string&!! "/bin:/usr/bin"
+This option is expanded and
+specifies the string that is set up in the PATH environment
+variable of the subprocess.
 If the &%command%& option does not yield an absolute path name, the command is
 sought in the PATH directories, in the usual way. &*Warning*&: This does not
 apply to a command specified as a transport filter.
@@ -23506,7 +23701,7 @@ of the message. Its value must not be zero. See also &%final_timeout%&.
 .option dkim_canon smtp string&!! unset
 .option dkim_strict smtp string&!! unset
 .option dkim_sign_headers smtp string&!! unset
-DKIM signing options.  For details see &<<SECDKIMSIGN>>&.
+DKIM signing options.  For details see section &<<SECDKIMSIGN>>&.
 
 
 .option delay_after_cutoff smtp boolean true
@@ -23562,7 +23757,7 @@ This applies to all of the SRV, MX, AAAA, A lookup sequence.
 .cindex "DNSSEC" "MX lookup"
 .cindex "security" "MX lookup"
 .cindex "DNS" "DNSSEC"
-DNS lookups for domains matching &%dnssec_request_domains%& will be done with
+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.
@@ -23749,6 +23944,25 @@ 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&!!" *
+.cindex "TLS" "passing connection"
+.cindex "multiple SMTP deliveries"
+.cindex "TLS" "multiple message deliveries"
+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.
+
+The traditional implementation closes down TLS and re-starts it in the new
+process, on the same open TCP connection, for each successive message
+sent.  If permitted by this option a pipe to to the new process is set up
+instead, and the original process maintains the TLS connection and proxies
+the SMTP connection from and to the new process and any subsequents.
+The new process has no access to TLS information, so cannot include it in
+logging.
+.wen
+
+
 
 .option hosts_override smtp boolean false
 If this option is set and the &%hosts%& option is also set, any hosts that are
@@ -23817,6 +24031,31 @@ connects. If authentication fails, Exim will try to transfer the message
 unauthenticated. See also &%hosts_require_auth%&, and chapter
 &<<CHAPSMTPAUTH>>& for details of authentication.
 
+.option hosts_try_chunking smtp "host list&!!" *
+.cindex CHUNKING "enabling, in client"
+.cindex BDAT "SMTP command"
+.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.
+BDAT will not be used in conjunction with a transport filter.
+
+.option hosts_try_fastopen smtp "host list!!" unset
+.cindex "fast open, TCP" "enabling, in client"
+.cindex "TCP Fast Open" "enabling, in client"
+.cindex "RFC 7413" "TCP Fast Open"
+This option provides a list of servers to which, provided
+the facility is supported by this system, Exim will attempt to
+perform a TCP Fast Open.
+No data is sent on the SYN segment but, if the remote server also
+supports the facility, it can send its SMTP banner immediately after
+the SYN,ACK segment.  This can save up to one round-trip time.
+
+The facility is only active for previously-contacted servers,
+as the initiator must present a cookie in the SYN segment.
+
+On (at least some) current Linux distributions the facility must be enabled
+in the kernel by the sysadmin before the support is usable.
+
 .option hosts_try_prdr smtp "host list&!!" *
 .cindex "PRDR" "enabling, optional in client"
 This option provides a list of servers to which, provided they announce
@@ -23987,7 +24226,7 @@ the use of the SIZE option altogether.
 .option socks_proxy smtp string&!! unset
 .cindex proxy SOCKS
 This option enables use of SOCKS proxies for connections made by the
-transport.  For details see &<<SECTproxySOCKS>>&.
+transport.  For details see section &<<SECTproxySOCKS>>&.
 
 
 .option tls_certificate smtp string&!! unset
@@ -25692,6 +25931,17 @@ turned into a permanent error if you wish. In the second case, Exim tries to
 deliver the message unauthenticated.
 .endlist
 
+Note that the hostlist test for whether to do authentication can be
+confused if name-IP lookups change between the time the peer is decided
+on and the transport running.  For example, with a manualroute
+router given a host name, and DNS "round-robin" use by that name: if
+the local resolver cache times out between the router and the transport
+running, the transport may get an IP for the name for its authentication
+check which does not match the connection peer IP.
+No authentication will then be done, despite the names being identical.
+
+For such cases use a separate transport which always authenticates.
+
 .cindex "AUTH" "on MAIL command"
 When Exim has authenticated itself to a remote server, it adds the AUTH
 parameter to the MAIL commands it sends, if it has an authenticated sender for
@@ -26601,7 +26851,7 @@ tls:
 .endd
 This accepts a client certificate that is verifiable against any
 of your configured trust-anchors
-which usually means the full set of public CAs)
+(which usually means the full set of public CAs)
 and which has a SAN with a good account name.
 Note that the client cert is on the wire in-clear, including the SAN,
 whereas a plaintext SMTP AUTH done inside TLS is not.
@@ -26963,10 +27213,12 @@ tls_require_ciphers = ${if =={$received_port}{25}\
 .cindex "TLS" "configuring an Exim server"
 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 unset, which means
-that STARTTLS is not advertised at all. This default is chosen because you
-need to set some other options in order to make TLS available, and also it is
-sensible for systems that want to use TLS only as a client.
+but not to any others. The default value of this option is *, which means
+that STARTTLS is alway advertised.  Set it to blank to never advertise;
+this is reasonble for systems that want to use TLS only as a client.
+
+If STARTTLS is to be used you
+need to set some other options in order to make TLS available.
 
 If a client issues a STARTTLS command and there is some configuration
 problem in the server, the command is rejected with a 454 error. If the client
@@ -26981,12 +27233,10 @@ rejected with a 554 error code.
 To enable TLS operations on a server, the &%tls_advertise_hosts%& option
 must be set to match some hosts. The default is * which matches all hosts.
 
-.new
 If this is all you do, TLS encryption will be enabled but not authentication -
 meaning that the peer has no assurance it is actually you he is talking to.
 You gain protection from a passive sniffer listening on the wire but not
 from someone able to intercept the communication.
-.wen
 
 Further protection requires some further configuration at the server end.
 
@@ -27363,8 +27613,11 @@ during TLS session handshake, to permit alternative values to be chosen:
 
 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 &$tls_sni$& is
+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
+an expansion for &%tls_certificate%& must have a default which is used
+when &$tls_in_sni$& is empty.
 
 The Exim developers are proceeding cautiously and so far no other TLS options
 are re-expanded.
@@ -27687,6 +27940,15 @@ received, before the final response to the DATA command is sent. This is
 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
 associated with the DATA command.
 
+.cindex CHUNKING "BDAT command"
+.cindex BDAT "SMTP command"
+.cindex "RFC 3030" CHUNKING
+If CHUNKING was advertised and a BDAT command sequence is received,
+the &%acl_smtp_predata%& ACL is not run.
+. XXX why not?  It should be possible, for the first BDAT.
+The &%acl_smtp_data%& is run after the last BDAT command and all of
+the data specified is received.
+
 For both of these ACLs, it is not possible to reject individual recipients. An
 error response rejects the entire message. Unfortunately, it is known that some
 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
@@ -27897,6 +28159,9 @@ run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
 remaining recipients. The &"discard"& return is not permitted for the
 &%acl_smtp_predata%& ACL.
 
+If the ACL for VRFY returns &"accept"&, a recipient verify (without callout)
+is done on the address and the result determines the SMTP response.
+
 
 .cindex "&[local_scan()]& function" "when all recipients discarded"
 The &[local_scan()]& function is always run, even if there are no remaining
@@ -28008,7 +28273,7 @@ provides a means of specifying an &"and"& conjunction between conditions. For
 example:
 .code
 deny  dnslists = list1.example
-dnslists = list2.example
+      dnslists = list2.example
 .endd
 If there are no conditions, the verb is always obeyed. Exim stops evaluating
 the conditions and modifiers when it reaches a condition that fails. What
@@ -28030,8 +28295,8 @@ after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
 check a RCPT command:
 .code
 accept domains = +local_domains
-endpass
-verify = recipient
+       endpass
+       verify = recipient
 .endd
 If the recipient domain does not match the &%domains%& condition, control
 passes to the next statement. If it does match, the recipient is verified, and
@@ -28583,6 +28848,17 @@ all the conditions are true, wherever it appears in an ACL command, whereas
 effect.
 
 
+.vitem &*queue*&&~=&~<&'text'&>
+This modifier specifies the use of a named queue for spool files
+for the message.
+It can only be used before the message is received (i.e. not in
+the DATA ACL).
+This could be used, for example, for known high-volume burst sources
+of traffic, or for quarantine of messages.
+Separate queue-runner processes will be needed for named queues.
+If the text after expansion is empty, the default queue is used.
+
+
 .vitem &*remove_header*&&~=&~<&'text'&>
 This modifier specifies one or more header names in a colon-separated list
  that are to be removed from an incoming message, assuming, of course, that
@@ -28669,7 +28945,7 @@ Notice that we put back the lower cased version afterwards, assuming that
 is what is wanted for subsequent tests.
 
 
-.vitem &*control&~=&~cutthrough_delivery*&
+.vitem &*control&~=&~cutthrough_delivery/*&<&'options'&>
 .cindex "&ACL;" "cutthrough routing"
 .cindex "cutthrough" "requesting"
 This option requests delivery be attempted while the item is being received.
@@ -28705,15 +28981,24 @@ message body.
 Cutthrough delivery is not supported via transport-filters or when DKIM signing
 of outgoing messages is done, because it sends data to the ultimate destination
 before the entire message has been received from the source.
-It is not supported for messages received with the SMTP PRDR option in use.
+It is not supported for messages received with the SMTP PRDR
+or CHUNKING
+options in use.
 
 Should the ultimate destination system positively accept or reject the mail,
 a corresponding indication is given to the source system and nothing is queued.
-If there is a temporary error the item is queued for later delivery in the
-usual fashion. If the item is successfully delivered in cutthrough mode
+If the item is successfully delivered in cutthrough mode
 the delivery log lines are tagged with ">>" rather than "=>" and appear
 before the acceptance "<=" line.
 
+If there is a temporary error the item is queued for later delivery in the
+usual fashion.
+This behaviour can be adjusted by appending the option &*defer=*&<&'value'&>
+to the control; the default value is &"spool"& and the alternate value
+&"pass"& copies an SMTP defer response from the target back to the initiator
+and does not queue the message.
+Note that this is independent of any recipient verify conditions in the ACL.
+
 Delivery in this mode avoids the generation of a bounce mail to a
 (possibly faked)
 sender when the destination system is doing content-scan based rejection.
@@ -28727,13 +29012,16 @@ with &`-d`&, with the output going to a new logfile, by default called
 &'debuglog'&.  The filename can be adjusted with the &'tag'& option, which
 may access any variables already defined.  The logging may be adjusted with
 the &'opts'& option, which takes the same values as the &`-d`& command-line
-option.  Some examples (which depend on variables that don't exist in all
+option.
+Logging may be stopped, and the file removed, with the &'kill'& option.
+Some examples (which depend on variables that don't exist in all
 contexts):
 .code
       control = debug
       control = debug/tag=.$sender_host_address
       control = debug/opts=+expand+acl
       control = debug/tag=.$message_exim_id/opts=+expand
+      control = debug/kill
 .endd
 
 
@@ -28933,7 +29221,7 @@ 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
 to a-label form.
-For details see &<<SECTi18nMTA>>&.
+For details see section &<<SECTi18nMTA>>&.
 .endlist vlist
 
 
@@ -28972,7 +29260,7 @@ any ACL verb, including &%deny%& (though this is potentially useful only in a
 RCPT ACL).
 
 Headers will not be added to the message if the modifier is used in
-DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing.
+DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
 
 Leading and trailing newlines are removed from
 the data for the &%add_header%& modifier; if it then
@@ -29073,8 +29361,8 @@ receiving a message). The message must ultimately be accepted for
 with any ACL verb, including &%deny%&, though this is really not useful for
 any verb that doesn't result in a delivered message.
 
-Headers will not be removed to the message if the modifier is used in
-DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing.
+Headers will not be removed from the message if the modifier is used in
+DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
 
 More than one header can be removed at the same time by using a colon separated
 list of header names. The header matching is case insensitive. Wildcards are
@@ -29546,6 +29834,13 @@ to avoid doing it more than once per message.
 .cindex "&%verify%& ACL condition"
 This is a variation of the previous option, in which a modified address is
 verified as a sender.
+
+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:}}{/}{//}}
+.endd
 .endlist
 
 
@@ -29605,7 +29900,7 @@ deny  dnslists = blackholes.mail-abuse.org
 warn  message  = X-Warn: sending host is on dialups list
       dnslists = dialups.mail-abuse.org
 .endd
-.cindex cacheing "of dns lookup"
+.cindex caching "of dns lookup"
 .cindex DNS TTL
 DNS list lookups are cached by Exim for the duration of the SMTP session
 (but limited by the DNS return TTL value),
@@ -29718,7 +30013,7 @@ multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
 of expanding the condition might be something like this:
 .code
-dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|...
+dnslists = sbl.spamhaus.org/<|192.168.2.3|192.168.5.6|...
 .endd
 Thus, this example checks whether or not the IP addresses of the sender
 domain's mail servers are on the Spamhaus black list.
@@ -31422,6 +31717,15 @@ configuration as follows (example):
 .code
 spamd_address = 192.168.99.45 387
 .endd
+The SpamAssassin protocol relies on a TCP half-close from the client.
+If your SpamAssassin client side is running a Linux system with an
+iptables firewall, consider setting
+&%net.netfilter.nf_conntrack_tcp_timeout_close_wait%& to at least the
+timeout, Exim uses when waiting for a response from the SpamAssassin
+server (currently defaulting to 120s).  With a lower value the Linux
+connection tracking may consider your half-closed connection as dead too
+soon.
+
 
 To use Rspamd (which by default listens on all local addresses
 on TCP port 11333)
@@ -31452,7 +31756,7 @@ condition defers.
 
 Unix and TCP socket specifications may be mixed in any order.
 Each element of the list is a list itself, space-separated by default
-and changeable in the usual way.
+and changeable in the usual way; take care to not double the separator.
 
 For TCP socket specifications a host name or IP (v4 or v6, but
 subject to list-separator quoting rules) address can be used,
@@ -31579,6 +31883,9 @@ spam bar is 50 characters.
 A multiline text table, containing the full SpamAssassin report for the
 message. Useful for inclusion in headers or reject messages.
 This variable is only usable in a DATA-time ACL.
+Beware that SpamAssassin may return non-ASCII characters, especially
+when running in country-specific locales, which are not legal
+unencoded in headers.
 
 .vitem &$spam_action$&
 For SpamAssassin either 'reject' or 'no action' depending on the
@@ -33164,6 +33471,7 @@ incoming SMTP message from a source that is not permitted to send them.
 
 .section "Resent- header lines" "SECID220"
 .cindex "&%Resent-%& header lines"
+.cindex "header lines" "Resent-"
 RFC 2822 makes provision for sets of header lines starting with the string
 &`Resent-`& to be added to a message when it is resent by the original
 recipient to somebody else. These headers are &'Resent-Date:'&,
@@ -33220,6 +33528,7 @@ existing &'Bcc:'& is not removed.
 
 .section "The Date: header line" "SECID223"
 .cindex "&'Date:'& header line"
+.cindex "header lines" "Date:"
 If a locally-generated or submission-mode message has no &'Date:'& header line,
 Exim adds one, using the current date and time, unless the
 &%suppress_local_fixups%& control has been specified.
@@ -33237,6 +33546,7 @@ messages.
 
 .section "The Envelope-to: header line" "SECID225"
 .cindex "&'Envelope-to:'& header line"
+.cindex "header lines" "Envelope-to:"
 .oindex "&%envelope_to_remove%&"
 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
 Exim can be configured to add them to the final delivery of messages. (See the
@@ -33248,6 +33558,7 @@ messages.
 
 .section "The From: header line" "SECTthefrohea"
 .cindex "&'From:'& header line"
+.cindex "header lines" "From:"
 .cindex "Sendmail compatibility" "&""From""& line"
 .cindex "message" "submission"
 .cindex "submission mode"
@@ -33291,6 +33602,7 @@ name as described in section &<<SECTconstr>>&.
 
 .section "The Message-ID: header line" "SECID226"
 .cindex "&'Message-ID:'& header line"
+.cindex "header lines" "Message-ID:"
 .cindex "message" "submission"
 .oindex "&%message_id_header_text%&"
 If a locally-generated or submission-mode incoming message does not contain a
@@ -33306,6 +33618,7 @@ in this header line by setting the &%message_id_header_text%& and/or
 
 .section "The Received: header line" "SECID227"
 .cindex "&'Received:'& header line"
+.cindex "header lines" "Received:"
 A &'Received:'& header line is added at the start of every message. The
 contents are defined by the &%received_header_text%& configuration option, and
 Exim automatically adds a semicolon and a timestamp to the configured string.
@@ -33322,6 +33635,7 @@ changed to the time of acceptance, which is (apart from a small delay while the
 
 .section "The References: header line" "SECID228"
 .cindex "&'References:'& header line"
+.cindex "header lines" "References:"
 Messages created by the &(autoreply)& transport include a &'References:'&
 header line. This is constructed according to the rules that are described in
 section 3.64 of RFC 2822 (which states that replies should contain such a
@@ -33336,6 +33650,7 @@ incoming message. If there are more than 12, the first one and then the final
 
 .section "The Return-path: header line" "SECID229"
 .cindex "&'Return-path:'& header line"
+.cindex "header lines" "Return-path:"
 .oindex "&%return_path_remove%&"
 &'Return-path:'& header lines are defined as something an MTA may insert when
 it does the final delivery of messages. (See the generic &%return_path_add%&
@@ -33348,6 +33663,7 @@ default), Exim removes &'Return-path:'& header lines from incoming messages.
 .section "The Sender: header line" "SECTthesenhea"
 .cindex "&'Sender:'& header line"
 .cindex "message" "submission"
+.cindex "header lines" "Sender:"
 For a locally-originated message from an untrusted user, Exim may remove an
 existing &'Sender:'& header line, and it may add a new one. You can modify
 these actions by setting the &%local_sender_retain%& option true, the
@@ -35316,6 +35632,7 @@ picked out by the distinctive two-character flags that immediately follow the
 timestamp. The flags are:
 .display
 &`<=`&     message arrival
+&`(=`&     message fakereject
 &`=>`&     normal message delivery
 &`->`&     additional address in same delivery
 &`>>`&     cutthrough message delivery
@@ -35438,6 +35755,12 @@ SMTP RCPT commands in one transaction) the second and subsequent addresses are
 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
 down a single SMTP connection, an asterisk follows the IP address in the log
 lines for the second and subsequent messages.
+.new
+When two or more messages are delivered down a single TLS connection, the
+TLS-related information logged for the first message delivered
+(which may not be the earliest line in the log)
+will not be present in the log lines for the second and subsequent messages.
+.wen
 
 .cindex "delivery" "cutthrough; logging"
 .cindex "cutthrough" "logging"
@@ -35543,14 +35866,18 @@ the following table:
 &`CV  `&        certificate verification status
 &`D   `&        duration of &"no mail in SMTP session"&
 &`DN  `&        distinguished name from peer certificate
+&`DS  `&        DNSSEC secured lookups
 &`DT  `&        on &`=>`& lines: time taken for a delivery
 &`F   `&        sender address (on delivery lines)
 &`H   `&        host name and IP address
 &`I   `&        local interface used
+&`K   `&        CHUNKING extension used
 &`id  `&        message id for incoming message
 &`P   `&        on &`<=`& lines: protocol used
 &`    `&        on &`=>`& and &`**`& lines: return path
-&`PRX `&        on &'<='& and&`=>`& lines: proxy address
+&`PRDR`&        PRDR extension used
+&`PRX `&        on &`<=`& and &`=>`& lines: proxy address
+&`Q   `&        alternate queue name
 &`QT  `&        on &`=>`& lines: time spent on queue so far
 &`    `&        on &"Completed"& lines: time spent on queue
 &`R   `&        on &`<=`& lines: reference for local bounce
@@ -35633,6 +35960,7 @@ selection marked by asterisks:
 &` deliver_time               `&  time taken to perform delivery
 &` delivery_size              `&  add &`S=`&&'nnn'& to => lines
 &`*dnslist_defer              `&  defers of DNS list (aka RBL) lookups
+&` dnssec                     `&  DNSSEC secured lookups
 &`*etrn                       `&  ETRN commands
 &`*host_lookup_failed         `&  as it says
 &` ident_timeout              `&  timeout for ident connection
@@ -35740,6 +36068,14 @@ the &"=>"& line, tagged with S=.
 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
 DNS black list suffers a temporary error.
 .next
+.cindex log dnssec
+.cindex dnssec logging
+&%dnssec%&: For message acceptance and (attempted) delivery log lines, when
+dns lookups gave secure results a tag of DS is added.
+For acceptance this covers the reverse and forward lookups for host name verification.
+It does not cover helo-name verification.
+For delivery this covers the SRV, MX, A and/or AAAA lookups.
+.next
 .cindex "log" "ETRN commands"
 .cindex "ETRN" "logging"
 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
@@ -35776,7 +36112,7 @@ The latter can be disabled by turning off the &%outgoing_interface%& option.
 &%proxy%&: The internal (closest to the system running Exim) IP address
 of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
 on a proxied connection
-or the &"=>"& line for a message delivered on a proxied connection..
+or the &"=>"& line for a message delivered on a proxied connection.
 See &<<SECTproxyInbound>>& for more information.
 .next
 .cindex "log" "incoming remote port"
@@ -35807,7 +36143,7 @@ off the &%outgoing_interface%& option.
 .next
 .cindex "log" "outgoing remote port"
 .cindex "port" "logging outgoint remote"
-.cindex "TCP/IP" "logging ougtoing remote port"
+.cindex "TCP/IP" "logging outgoing remote port"
 &%outgoing_port%&: The remote port number is added to delivery log lines (those
 containing => tags) following the IP address.
 The local port is also added if &%incoming_interface%& and
@@ -37636,9 +37972,8 @@ lock will be lost at the instant of rename.
 .next
 .vindex "&$body_linecount$&"
 If you change the number of lines in the file, the value of
-&$body_linecount$&, which is stored in the -H file, will be incorrect. At
-present, this value is not used by Exim, but there is no guarantee that this
-will always be the case.
+&$body_linecount$&, which is stored in the -H file, will be incorrect and can
+cause incomplete transmission of messages or undeliverable messages.
 .next
 If the message is in MIME format, you must take care not to break it.
 .next
@@ -37939,14 +38274,14 @@ DKIM is documented in RFC 4871.
 DKIM support is compiled into Exim by default if TLS support is present.
 It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
 
-Exim's DKIM implementation allows to
+Exim's DKIM implementation allows for
 .olist
-Sign outgoing messages: This function is implemented in the SMTP transport.
+Signing outgoing messages: This function is implemented in the SMTP transport.
 It can co-exist with all other Exim features
 (including transport filters)
 except cutthrough delivery.
 .next
-Verify signatures in incoming messages: This is implemented by an additional
+Verifying signatures in incoming messages: This is implemented by an additional
 ACL (acl_smtp_dkim), which can be called several times per message, with
 different signature contexts.
 .endlist
@@ -37975,13 +38310,14 @@ senders).
 .section "Signing outgoing messages" "SECDKIMSIGN"
 .cindex "DKIM" "signing"
 
-Signing is implemented by setting private options on the SMTP transport.
+Signing is enabled by setting private options on the SMTP transport.
 These options take (expandable) strings as arguments.
 
 .option dkim_domain smtp string&!! unset
 MANDATORY:
 The domain you want to sign with. The result of this expanded
 option is put into the &%$dkim_domain%& expansion variable.
+If it is empty after expansion, DKIM signing is not done.
 
 .option dkim_selector smtp string&!! unset
 MANDATORY:
@@ -38032,7 +38368,7 @@ used.
 .section "Verifying DKIM signatures in incoming mail" "SECID514"
 .cindex "DKIM" "verification"
 
-Verification of DKIM signatures in incoming email is implemented via the
+Verification of DKIM signatures in SMTP incoming email is implemented via the
 &%acl_smtp_dkim%& ACL. By default, this ACL is called once for each
 syntactically(!) correct signature in the incoming message.
 A missing ACL definition defaults to accept.
@@ -38085,6 +38421,7 @@ available (from most to least important):
 The signer that is being evaluated in this ACL run. This can be a domain or
 an identity. This is one of the list items from the expanded main option
 &%dkim_verify_signers%& (see above).
+
 .vitem &%$dkim_verify_status%&
 A string describing the general status of the signature. One of
 .ilist
@@ -38099,6 +38436,7 @@ available in &%$dkim_verify_reason%&.
 .next
 &%pass%&: The signature passed verification. It is valid.
 .endlist
+
 .vitem &%$dkim_verify_reason%&
 A string giving a little bit more detail when &%$dkim_verify_status%& is either
 "fail" or "invalid". One of
@@ -38118,51 +38456,71 @@ could not be verified. This may mean that headers were modified,
 re-written or otherwise changed in a way which is incompatible with
 DKIM verification. It may of course also mean that the signature is forged.
 .endlist
+
 .vitem &%$dkim_domain%&
 The signing domain. IMPORTANT: This variable is only populated if there is
 an actual signature in the message for the current domain or identity (as
 reflected by &%$dkim_cur_signer%&).
+
 .vitem &%$dkim_identity%&
 The signing identity, if present. IMPORTANT: This variable is only populated
 if there is an actual signature in the message for the current domain or
 identity (as reflected by &%$dkim_cur_signer%&).
+
 .vitem &%$dkim_selector%&
 The key record selector string.
+
 .vitem &%$dkim_algo%&
 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
+
 .vitem &%$dkim_canon_body%&
 The body canonicalization method. One of 'relaxed' or 'simple'.
+
 .vitem &%dkim_canon_headers%&
 The header canonicalization method. One of 'relaxed' or 'simple'.
+
 .vitem &%$dkim_copiedheaders%&
 A transcript of headers and their values which are included in the signature
 (copied from the 'z=' tag of the signature).
+Note that RFC6376 requires that verification fail if the From: header is
+not included in the signature.  Exim does not enforce this; sites wishing
+strict enforcement should code the check explicitly.
+
 .vitem &%$dkim_bodylength%&
 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
 limit was set by the signer, "9999999999999" is returned. This makes sure
 that this variable always expands to an integer value.
+
 .vitem &%$dkim_created%&
 UNIX timestamp reflecting the date and time when the signature was created.
 When this was not specified by the signer, "0" is returned.
+
 .vitem &%$dkim_expires%&
 UNIX timestamp reflecting the date and time when the signer wants the
 signature to be treated as "expired". When this was not specified by the
 signer, "9999999999999" is returned. This makes it possible to do useful
 integer size comparisons against this value.
+
 .vitem &%$dkim_headernames%&
 A colon-separated list of names of headers included in the signature.
+
 .vitem &%$dkim_key_testing%&
 "1" if the key record has the "testing" flag set, "0" if not.
+
 .vitem &%$dkim_key_nosubdomains%&
 "1" if the key record forbids subdomaining, "0" otherwise.
+
 .vitem &%$dkim_key_srvtype%&
 Service type (tag s=) from the key record. Defaults to "*" if not specified
 in the key record.
+
 .vitem &%$dkim_key_granularity%&
 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
 in the key record.
+
 .vitem &%$dkim_key_notes%&
 Notes from the key record (tag n=).
+
 .vitem &%$dkim_key_length%&
 Number of bits in the key.
 .endlist
@@ -38177,13 +38535,16 @@ for a match against the domain or identity that the ACL is currently verifying
 verb to a group of domains or identities. For example:
 
 .code
-# Warn when Mail purportedly from GMail has no signature at all
-warn log_message = GMail sender without DKIM signature
+# Warn when Mail purportedly from GMail has no gmail signature
+warn log_message = GMail sender without gmail.com DKIM signature
      sender_domains = gmail.com
      dkim_signers = gmail.com
      dkim_status = none
 .endd
 
+Note that the above does not check for a total lack of DKIM signing;
+for that check for empty &$h_DKIM-Signature:$& in the data ACL.
+
 .vitem &%dkim_status%&
 ACL condition that checks a colon-separated list of possible DKIM verification
 results against the actual result of verification. This is typically used
@@ -38225,9 +38586,9 @@ To include this support, include &"SUPPORT_PROXY=yes"&
 in Local/Makefile.
 
 It was built on specifications from:
-http://haproxy.1wt.eu/download/1.5/doc/proxy-protocol.txt
+(&url(http://haproxy.1wt.eu/download/1.5/doc/proxy-protocol.txt)).
 That URL was revised in May 2014 to version 2 spec:
-http://git.1wt.eu/web?p=haproxy.git;a=commitdiff;h=afb768340c9d7e50d8e
+(&url(http://git.1wt.eu/web?p=haproxy.git;a=commitdiff;h=afb768340c9d7e50d8e)).
 
 The purpose of this facility is so that an application load balancer,
 such as HAProxy, can sit in front of several Exim servers
@@ -38241,21 +38602,26 @@ recorded in an ACL (example is below).
 Use of a proxy is enabled by setting the &%hosts_proxy%&
 main configuration option to a hostlist; connections from these
 hosts will use Proxy Protocol.
+Exim supports both version 1 and version 2 of the Proxy Protocol and
+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.
 
-.new
 The following expansion variables are usable
 (&"internal"& and &"external"& here refer to the interfaces
 of the proxy):
 .display
 &'proxy_external_address   '& IP of host being proxied or IP of remote interface of proxy
 &'proxy_external_port      '& Port of host being proxied or Port on remote interface of proxy
-&'proxy_local_address '& IP of proxy server inbound or IP of local interface of proxy
-&'proxy_local_port    '& Port of proxy server inbound or Port on local interface of proxy
-&'proxy_session        '& boolean: SMTP connection via proxy
+&'proxy_local_address      '& IP of proxy server inbound or IP of local interface of proxy
+&'proxy_local_port         '& Port of proxy server inbound or Port on local interface of proxy
+&'proxy_session            '& boolean: SMTP connection via proxy
 .endd
 If &$proxy_session$& is set but &$proxy_external_address$& is empty
 there was a protocol error.
-.wen
 
 Since the real connections are all coming from the proxy, and the
 per host connection tracking is done before Proxy Protocol is
@@ -38363,6 +38729,10 @@ Exim has support for Internationalised mail names.
 To include this it must be built with SUPPORT_I18N and the libidn library.
 Standards supported are RFCs 2060, 5890, 6530 and 6533.
 
+If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not
+instead of it) then IDNA2008 is supported; this adds an extra library
+requirement, upon libidn2.
+
 .section "MTA operations" SECTi18nMTA
 .cindex SMTPUTF8 "ESMTP option"
 The main configuration option &%smtputf8_advertise_hosts%& specifies
@@ -38394,7 +38764,7 @@ form of the name.
 Log lines and Received-by: header lines will acquire a "utf8"
 prefix on the protocol element, eg. utf8esmtp.
 
-The following expansion operator can be used:
+The following expansion operators can be used:
 .code
 ${utf8_domain_to_alabel:str}
 ${utf8_domain_from_alabel:str}
@@ -38476,7 +38846,7 @@ must be representable in UTF-16.
 .cindex events
 
 The events mechanism in Exim can be used to intercept processing at a number
-of points.  It was originally invented to giave a way to do customised logging
+of points.  It was originally invented to give a way to do customised logging
 actions (for example, to a database) but can also be used to modify some
 processing actions.
 
@@ -38535,7 +38905,7 @@ can be used to affect that action (more on this below).
 An additional variable, &$event_data$&, is filled with information varying
 with the event type:
 .display
-&`msg:delivery         `& smtp confirmation mssage
+&`msg:delivery         `& smtp confirmation message
 &`msg:rcpt:host:defer  `& error string
 &`msg:rcpt:defer       `& error string
 &`msg:host:defer       `& error string
@@ -38546,7 +38916,7 @@ with the event type:
 The :defer events populate one extra variable: &$event_defer_errno$&.
 
 For complex operations an ACL expansion can be used in &%event_action%&
-however due to the multiple contextx that Exim operates in during
+however due to the multiple contexts that Exim operates in during
 the course of its processing:
 .ilist
 variables set in transport events will not be visible outside that