+PH/12 When the plaintext authenticator is running as a client, the server
+ challenges are now checked to ensure they are valid base64 strings. The
+ default action on failure is to abort the authentication. However, if
+ client_ignore_invalid_base64 is set true, invalid responses are ignored.
+
+PH/13 When the plaintext authenticator is running as a client, the challenges
+ from the server are placed in $auth1, $auth2, etc. as they are received.
+ Thus, the challege that is received in response to sending the first
+ string (with the AUTH command) can be used in the expansion of the second
+ string, and so on. Currently, up to 3 challenge strings are available in
+ this way. If an invalid base64 string is received when client_ignore_
+ invalid_base64 is set, an empty string is put in the $auth<n> variable.
+
+PH/14 Messages created by the autoreply transport now contain a References:
+ header. This is constructed in accordance with rules that are described
+ in section 3.64 of RFC 2822, which states that replies should contain
+ such a header line, and section 3.14 of RFC 3834, which states that
+ automatic responses are not different in this respect. However, because
+ some mail processing software does not cope well with very long header
+ lines, no more than 12 message IDs are copied from the References: header
+ line in the incoming message. If there are more than 12, the first one
+ and then the final 11 are copied, before adding the message ID of the
+ incoming message.
+
+PH/15 The smtp transport has a new option called authenticated_sender_force.
+ When set true, it allows the authenticated_sender option's value to be
+ used, even if Exim has not authenticated as a client.
+
+PH/16 The expansion ${time_eval:<string>} converts an Exim time string such as
+ 2d4h1m into a number of seconds.
+
+PH/17 The ACL modifier control=allow_auth_unadvertised can be used to permit a
+ client host to use the SMTP AUTH command even when it has not been
+ advertised in response to EHLO. Furthermore, because there are apparently
+ some really broken clients that do this, Exim will even accept AUTH after
+ HELO when this control is set. It should only be used if you really need
+ it, and you should limit its use to those broken hosts that do not work
+ without it. For example:
+
+ warn hosts = 192.168.34.25
+ control = allow_auth_unadvertised
+
+ This control is permitted only in the connection and HELO ACLs.
+
+PH/18 There is a new ACL modifier called "add_header" which does what its name
+ implies. It specifies one of more header lines that are to be added to an
+ incoming message, assuming, of course, that the message is ultimately
+ accepted.
+
+ This modifier is permitted in the MAIL, RCPT, PREDATA, DATA, MIME, and
+ non-SMTP ACLs (in other words, those that are concerned with accepting a
+ message). Added header lines are accumulated during the MAIL, RCPT, and
+ PREDATA ACLs, with any duplicates being discarded. They are then added to
+ the message before processing the DATA and MIME ACLs, during which
+ further added header lines are accumulated, again with duplicates
+ discarded. Thus, it is possible to add two identical header lines to an
+ SMTP message, but only if one is added before DATA and one after.
+
+ In the case of non-SMTP messages, new headers are accumulated during the
+ non-SMTP ACL, and added to the message at the end.
+
+ The add_header modifier is available for use with all ACL verbs. In the
+ case of the WARN verb, add_header supersedes the use of "message" for
+ this purpose; for the other verbs, it provides a new facility. If both
+ add_header and "message" are present on a WARN verb, both are processed
+ according to their specifications.
+
+ The add_header modifier acts immediately it is encountered during the
+ processing of an ACL. This is different to the (now-deprecated) use of
+ "message" on a WARN verb, where the action is taken only if all the
+ conditions are true. Notice the difference between these two cases on a
+ RCPT ACL:
+
+ deny add_header = ADDED: some text
+ <some condition>
+
+ deny <some condition>
+ add_header = ADDED: some text
+
+ In the first case, the header is always added, whether or not the current
+ recipient is rejected. In the second case, the header is added only if
+ the recipient is rejected.
+
+ If add_header appears more than once on an ACL statement, multiple
+ headers are added, provided that they have different content. (In the
+ case of WARN with "message", only the last value of "message" is used.)
+
+ The facility for specifying where the new header is to be inserted, as
+ described for WARN with "message" in section 39.19 of the 4.60 manual, is
+ supported.
+
+PH/19 The following errors can now be detected in retry rules:
+
+ mail_4xx This is like rcpt_4xx, but applies to MAIL commands
+
+ data_4xx This is like rcpt_4xx, but applies to DATA commands and the
+ response code after the end of the data
+
+ lost_connection This error occurs when the server unexpectedly closes
+ the SMTP connection. There may, of course, legitmate reasons
+ for this (host died, network died), but if it repeats a lot
+ for the same host, it indicates something odd.
+
+ tls_required The server was required to use TLS (hosts_require_tls),
+ but either did not offer it, or responded with 4xx to
+ STARTTLS, or there was a problem setting up the TLS connection
+
+ Note that a 5xx response to STARTTLS is a permanent error.
+
+PH/20 There are now two options for the exicyclog script:
+
+ -k <days> specifies the number of old logs to keep, overriding the
+ default that is set when Exim is built.
+
+ -l <path> specifies the log file path, in the same format as the
+ log_file_path option (e.g. /var/log/exim_%slog), again,
+ overriding the script's default - which is to find the setting
+ from Exim's configuration.
+