GSASL: remove unneeded stringprep operations; library does it for us

[exim.git] / src / README.UPDATING

This document contains detailed information about incompatibilities that might
be encountered when upgrading from one release of Exim to another. The
information is in reverse order of release numbers. Mostly these are relatively
small points, and the configuration file is normally upwards compatible, but
there have been two big upheavals...


**************************************************************************
* There was a big reworking of the way mail routing works for release    *
* 4.00. Previously used "directors" were abolished, and all routing is   *
* now done by routers. Policy controls for incoming mail are now done by *
* Access Control Lists instead of separate options. All this means that  *
* pre-4.00 configuration files have to be massively converted. If you    *
* are coming from a 3.xx release, please read the document in the file   *
* doc/Exim4.upgrade, and allow some time to complete the upgrade.        *
*                                                                        *
* There was a big reworking of the way domain/host/net/address lists are *
* handled at release 3.00. If you are coming from a pre-3.00 release, it *
* might be easier to start again from a default configuration. Otherwise *
* you need to read doc/Exim3.upgrade and do a double conversion of your  *
* configuration file.                                                    *
**************************************************************************


The rest of this document contains information about changes in 4.xx releases
that might affect a running system.

Exim version 4.93
-----------------

For a detailed list of changes that might affect Exim's operation with
an unchanged configuration, please see the doc/ChangeLog file.

Build:

 * SUPPORT_DMARC replaces EXPERIMENTAL_DMARC

 * DISABLE_TLS replaces SUPPORT_TLS

 * Bump the version for the local_scan API.

Runtime:

 * smtp transport option hosts_try_fastopen defaults to "*".

 * DNSSec is requested (not required) for all queries. (This seemes to
   ask for trouble if your resolver is a systemd-resolved.)

 * Generic router option retry_use_local_part defaults to "true" under specific
   pre-conditions.

 * Introduce a tainting mechanism for values read from untrusted sources.

 * Use longer file names for temporary spool files (this avoids
   name conflicts with spool on a shared file system).

 * Use dsn_from main config option (was ignored previously).


Exim version 4.92
-----------------

 * Exim used to manually follow CNAME chains, to a limited depth.  In this
   day-and-age we expect the resolver to be doing this for us, so the loop
   is limited to one retry unless the (new) config option dns_cname_loops
   is changed.

Exim version 4.91
-----------------

 * DANE and SPF have been promoted from Experimental to Supported status, thus
   the options to enable them in Local/Makefile have been renamed.
   See current src/EDITME for full details, including changes in dependencies,
   but loosely: replace EXPERIMENTAL_SPF with SUPPORT_SPF and replace
   EXPERIMENTAL_DANE with SUPPORT_DANE.

 * Ancient ClamAV stream support, long deprecated by ClamAV, has been removed;
   if you were building with WITH_OLD_CLAMAV_STREAM enabled then your problems
   have marginally increased.

 * A number of logging changes; if relying upon the previous DKIM additional
   log-line, explicit log_selector configuration is needed to keep it.

 * Other incompatible changes in EXPERIMENTAL_* features, read NewStuff and
   ChangeLog carefully if relying upon an experimental feature such as DMARC.
   Note that this includes changes to SPF as it was promoted into Supported.


Exim version 4.89
-----------------

 * SMTP CHUNKING in Exim 4.88 did not ensure that received mails had a final
   newline; attempts to deliver such messages onwards to non-chunking hosts
   would probably hang, as Exim does not insert the newline before a ".".
   In 4.89, the newline is added upon receipt.  For already-received messages
   in your queue, try util/chunking_fixqueue_finalnewlines.pl
   to walk the queue, fixing any affected messages.  Note that because a
   delivery attempt will be hanging, attempts to lock the messages for fixing
   them will stall; stopping all queue-runners temporarily is recommended.

 * OpenSSL: oldest supported release series is now 1.0.2, which is the oldest
   supported by the OpenSSL project.  If you can build Exim with an older
   release series, congratulations.  If you can't, then upgrade.
   The file doc/openssl.txt contains instructions for installing a current
   OpenSSL outside the system library paths and building Exim to use it.

 * FreeBSD: we now always use the system iconv in libc, as all versions of
   FreeBSD supported by the FreeBSD project provide this functionality.


Exim version 4.88
-----------------

 * The "demime" ACL condition, deprecated for the past 10 years, has
   now been removed.

 * Old GnuTLS configuration options "gnutls_require_kx", "gnutls_require_mac",
   and "gnutls_require_protocols" have now been removed.  (Inoperative from
   4.80, per below; logging warnings since 4.83, again per below).


Exim version 4.83
-----------------

 * SPF condition results renamed "permerror" and "temperror".  The old
   names are still accepted for back-compatibility, for this release.

 * TLS details are now logged on rejects, subject to log selectors.

 * Items in headers_remove lists must now have any embedded list-separators
   doubled.

 * Attempted use of the deprecated options "gnutls_require_kx" et. al.
   now result in logged warning.


Exim version 4.82
-----------------

 * New option gnutls_allow_auto_pkcs11 defaults false; if you have GnuTLS 2.12.0
   or later and do want PKCS11 modules to be autoloaded, then set this option.

 * A per-transport wait-<name> database is no longer updated if the transport
   sets "connection_max_messages" to 1, as it can not be used and causes
   unnecessary serialisation and load.  External tools tracking the state of
   Exim by the hints databases may need modification to take this into account.

 * The av_scanner option can now accept multiple clamd TCP targets, all other
   setting limitations remain.


Exim version 4.80
-----------------

 * BEWARE backwards-incompatible changes in SSL libraries, thus the version
   bump.  See points below for details.
   Also an LDAP data returned format change.

 * The value of $tls_peerdn is now print-escaped when written to the spool file
   in a -tls_peerdn line, and unescaped when read back in.  We received reports
   of values with embedded newlines, which caused spool file corruption.

   If you have a corrupt spool file and you wish to recover the contents after
   upgrading, then lock the message, replace the new-lines that should be part
   of the -tls_peerdn line with the two-character sequence \n and then unlock
   the message.  No tool has been provided as we believe this is a rare
   occurrence.

 * For OpenSSL, SSLv2 is now disabled by default.  (GnuTLS does not support
   SSLv2).  RFC 6176 prohibits SSLv2 and some informal surveys suggest no
   actual usage.  You can re-enable with the "openssl_options" Exim option,
   in the main configuration section.  Note that supporting SSLv2 exposes
   you to ciphersuite downgrade attacks.

 * With OpenSSL 1.0.1+, Exim now supports TLS 1.1 and TLS 1.2.  If built
   against 1.0.1a then you will get a warning message and the
   "openssl_options" value will not parse "no_tlsv1_1": the value changes
   incompatibly between 1.0.1a and 1.0.1b, because the value chosen for 1.0.1a
   is infelicitous.  We advise avoiding 1.0.1a.

   "openssl_options" gains "no_tlsv1_1", "no_tlsv1_2" and "no_compression".

   COMPATIBILITY WARNING: The default value of "openssl_options" is no longer
   "+dont_insert_empty_fragments".  We default to "+no_sslv2".
   That old default was grandfathered in from before openssl_options became a
   configuration option.
   Empty fragments are inserted by default through TLS1.0, to partially defend
   against certain attacks; TLS1.1+ change the protocol so that this is not
   needed.  The DIEF SSL option was required for some old releases of mail
   clients which did not gracefully handle the empty fragments, and was
   initially set in Exim release 4.31 (see ChangeLog, item 37).

   If you still have affected mail-clients, and you see SSL protocol failures
   with this release of Exim, set:
     openssl_options = +dont_insert_empty_fragments
   in the main section of your Exim configuration file.  You're trading off
   security for compatibility.  Exim is now defaulting to higher security and
   rewarding more modern clients.

   If the option tls_dhparams is set and the parameters loaded from the file
   have a bit-count greater than the new option tls_dh_max_bits, then the file
   will now be ignored.  If this affects you, raise the tls_dh_max_bits limit.
   We suspect that most folks are using dated defaults and will not be affected.

 * Ldap lookups returning multi-valued attributes now separate the attributes
   with only a comma, not a comma-space sequence.  Also, an actual comma within
   a returned attribute is doubled.  This makes it possible to parse the
   attribute as a comma-separated list.  Note the distinction from multiple
   attributes being returned, where each one is a name=value pair.

   If you are currently splitting the results from LDAP upon a comma, then you
   should check carefully to see if adjustments are needed.

   This change lets cautious folks distinguish "comma used as separator for
   joining values" from "comma inside the data".

 * accept_8bitmime now defaults on, which is not RFC compliant but is better
   suited to today's Internet.  See http://cr.yp.to/smtp/8bitmime.html for a
   sane rationale.  Those who wish to be strictly RFC compliant, or know that
   they need to talk to servers that are not 8-bit-clean, now need to take
   explicit configuration action to default this option off.  This is not a
   new option, you can safely force it off before upgrading, to decouple
   configuration changes from the binary upgrade while remaining RFC compliant.

 * The GnuTLS support has been mostly rewritten, to use APIs which don't cause
   deprecation warnings in GnuTLS 2.12.x.  As part of this, these three options
   are no longer supported:

     gnutls_require_kx
     gnutls_require_mac
     gnutls_require_protocols

   Their functionality is entirely subsumed into tls_require_ciphers.  In turn,
   tls_require_ciphers is no longer an Exim list and is not parsed by Exim, but
   is instead given to gnutls_priority_init(3), which expects a priority string;
   this behaviour is much closer to the OpenSSL behaviour.  See:

     http://www.gnutls.org/manual/html_node/Priority-Strings.html

   for fuller documentation of the strings parsed.  The three gnutls_require_*
   options are still parsed by Exim and, for this release, silently ignored.
   A future release will add warnings, before a later still release removes
   parsing entirely and the presence of the options will be a configuration
   error.

   Note that by default, GnuTLS will not accept RSA-MD5 signatures in chains.
   A tls_require_ciphers value of NORMAL:%VERIFY_ALLOW_SIGN_RSA_MD5 may
   re-enable support, but this is not supported by the Exim maintainers.
   Our test suite no longer includes MD5-based certificates.

   This rewrite means that Exim will continue to build against GnuTLS in the
   future, brings Exim closer to other GnuTLS applications and lets us add
   support for SNI and other features more readily.  We regret that it wasn't
   feasible to retain the three dropped options.

 * If built with TLS support, then Exim will now validate the value of
   the main section tls_require_ciphers option at start-up.  Before, this
   would cause a STARTTLS 4xx failure, now it causes a failure to start.
   Running with a broken configuration which causes failures that may only
   be left in the logs has been traded off for something more visible.  This
   change makes an existing problem more prominent, but we do not believe
   anyone would deliberately be running with an invalid tls_require_ciphers
   option.

   This also means that library linkage issues caused by conflicts of some
   kind might take out the main daemon, not just the delivery or receiving
   process.  Conceivably some folks might prefer to continue delivering
   mail plaintext when their binary is broken in this way, if there is a
   server that is a candidate to receive such mails that does not advertise
   STARTTLS.  Note that Exim is typically a setuid root binary and given
   broken linkage problems that cause segfaults, we feel it is safer to
   fail completely.  (The check is not done as root, to ensure that problems
   here are not made worse by the check).

 * The "tls_dhparam" option has been updated, so that it can now specify a
   path or an identifier for a standard DH prime from one of a few RFCs.
   The default for OpenSSL is no longer to not use DH but instead to use
   one of these standard primes.  The default for GnuTLS is no longer to use
   a file in the spool directory, but to use that same standard prime.
   The option is now used by GnuTLS too.  If it points to a path, then
   GnuTLS will use that path, instead of a file in the spool directory;
   GnuTLS will attempt to create it if it does not exist.

   To preserve the previous behaviour of generating files in the spool
   directory, set "tls_dhparam = historic".  Since prior releases of Exim
   ignored tls_dhparam when using GnuTLS, this can safely be done before
   the upgrade.



Exim version 4.77
-----------------

 * GnuTLS will now attempt to use TLS 1.2 and TLS 1.1 before TLS 1.0 and SSL3,
   if supported by your GnuTLS library.  Use the existing
   "gnutls_require_protocols" option to downgrade this if that will be a
   problem.  Prior to this release, supported values were "TLS1" and "SSL3",
   so you should be able to update configuration prior to update.

    [nb: gnutls_require_protocols removed in Exim 4.80, instead use
         tls_require_ciphers to provide a priority string; see notes above]

 * The match_<type>{string1}{string2} expansion conditions no longer subject
   string2 to string expansion, unless Exim was built with the new
   "EXPAND_LISTMATCH_RHS" option.  Too many people have inadvertently created
   insecure configurations that way.  If you need the functionality and turn on
   that build option, please let the developers know, and know why, so we can
   try to provide a safer mechanism for you.

   The match{}{} expansion condition (for regular expressions) is NOT affected.
   For match_<type>{s1}{s2}, all list functionality is unchanged.  The only
   change is that a '$' appearing in s2 will not trigger expansion, but instead
   will be treated as a literal $ sign; the effect is very similar to having
   wrapped s2 with \N...\N.  If s2 contains a named list and the list definition
   uses $expansions then those _will_ be processed as normal.  It is only the
   point at which s2 is read where expansion is inhibited.

   If you are trying to test if two email addresses are equal, use eqi{s1}{s2}.
   If you are testing if the address in s1 occurs in the list of items given
   in s2, either use the new inlisti{s1}{s2} condition (added in 4.77) or use
   the pre-existing forany{s2}{eqi{$item}{s1}} condition.


Exim version 4.74
-----------------

 * The integrated support for dynamically loadable lookup modules has an ABI
   change from the modules supported by some OS vendors through an unofficial
   patch. Don't try to mix & match.

 * Some parts of the build system are now beginning to assume that the host
   environment is POSIX. If you're building on a system where POSIX tools are
   not the default, you might have an easier time if you switch to the POSIX
   tools.  Feel free to report non-POSIX issues as a request for a feature
   enhancement, but if the POSIX variants are available then the fix will
   probably just involve some coercion.  See the README instructions for
   building on such hosts.


Exim version 4.73
-----------------

 * The Exim run-time user can no longer be root; this was always
   strongly discouraged, but is now prohibited both at build and
   run-time.  If you need Exim to run routinely as root, you'll need to
   patch the source and accept the risk.  Here be dragons.

 * Exim will no longer accept a configuration file owned by the Exim
   run-time user, unless that account is explicitly the value in
   CONFIGURE_OWNER, which we discourage.  Exim now checks to ensure that
   files are not writeable by other accounts.

 * The ALT_CONFIG_ROOT_ONLY build option is no longer optional and is forced
   on; the Exim user can, by default, no longer use -C/-D and retain privilege.
   Two new build options mitigate this.

    * TRUSTED_CONFIG_LIST defines a file containing a whitelist of config
      files that are trusted to be selected by the Exim user; one per line.
      This is the recommended approach going forward.

    * WHITELIST_D_MACROS defines a colon-separated list of macro names which
      the Exim run-time user may safely pass without dropping privileges.
      Because changes to this involve a recompile, this is not the recommended
      approach but may ease transition.  The values of the macros, when
      overridden, are constrained to match this regex: ^[A-Za-z0-9_/.-]*$

 * The system_filter_user option now defaults to the Exim run-time user,
   rather than root.  You can still set it explicitly to root and this
   can be done with prior versions too, letting you roll versions
   without needing to change this configuration option.

 * ClamAV must be at least version 0.95 unless WITH_OLD_CLAMAV_STREAM is
   defined at build time.


Exim version 4.70
-----------------

1. Experimental Yahoo! Domainkeys support has been dropped in this release.
It has been superseded by a native implementation of its successor DKIM.

2. Up to version 4.69, Exim came with an embedded version of the PCRE library.
As of 4.70, this is no longer the case. To compile Exim, you will need PCRE
installed. Most OS distributions have ready-made library and development
packages.


Exim version 4.68
-----------------

1. The internal implementation of the database keys that are used for ACL
ratelimiting has been tidied up. This means that an update to 4.68 might cause
Exim to "forget" previous rates that it had calculated, and reset them to zero.


Exim version 4.64
-----------------

1. Callouts were setting the name used for EHLO/HELO from $smtp_active_
hostname. This is wrong, because it relates to the incoming message (and
probably the interface on which it is arriving) and not to the outgoing
callout (which could be using a different interface). This has been
changed to use the value of the helo_data option from the smtp transport
instead - this is what is used when a message is actually being sent. If
there is no remote transport (possible with a router that sets up host
addresses), $smtp_active_hostname is used. This change is mentioned here in
case somebody is relying on the use of $smtp_active_hostname.

2. A bug has been fixed that might just possibly be something that is relied on
in some configurations. In expansion items such as ${if >{xxx}{yyy}...} an
empty string (that is {}) was being interpreted as if it was {0} and therefore
treated as the number zero. From release 4.64, such strings cause an error
because a decimal number, possibly followed by K or M, is required (as has
always been documented).

3. There has been a change to the GnuTLS support (ChangeLog/PH/20) to improve
Exim's performance. Unfortunately, this has the side effect of being slightly
non-upwards compatible for versions 4.50 and earlier. If you are upgrading from
one of these earlier versions and you use GnuTLS, you must remove the file
called gnutls-params in Exim's spool directory. If you don't do this, you will
see this error:

  TLS error on connection from ... (DH params import): Base64 decoding error.

Removing the file causes Exim to recompute the relevant encryption parameters
and cache them in the new format that was introduced for release 4.51 (May
2005). If you are upgrading from release 4.51 or later, there should be no
problem.


Exim version 4.63
-----------------

When an SMTP error message is specified in a "message" modifier in an ACL, or
in a :fail: or :defer: message in a redirect router, Exim now checks the start
of the message for an SMTP error code. This consists of three digits followed
by a space, optionally followed by an extended code of the form n.n.n, also
followed by a space. If this is the case and the very first digit is the same
as the default error code, the code from the message is used instead. If the
very first digit is incorrect, a panic error is logged, and the default code is
used. This is an incompatible change, but it is not expected to affect many (if
any) configurations. It is possible to suppress the use of the supplied code in
a redirect router by setting the smtp_error_code option false. In this case,
any SMTP code is quietly ignored.


Exim version 4.61
-----------------

1. The default number of ACL variables of each type has been increased to 20,
and it's possible to compile Exim with more. You can safely upgrade to this
release if you already have messages on the queue with saved ACL variable
values. However, if you downgrade from this release with messages on the queue,
any saved ACL values they may have will be lost.

2. The default value for rfc1413_query_timeout has been changed from 30s to 5s.


Exim version 4.54
-----------------

There was a problem with 4.52/TF/02 in that a "name=" option on control=
submission terminated at the next slash, thereby not allowing for slashes in
the name. This has been changed so that "name=" takes the rest of the string as
its data. It must therefore be the last option.


Version 4.53
------------

If you are using the experimental Domain Keys support, you must upgrade to
at least libdomainkeys 0.67 in order to run this release of Exim.


Version 4.51
------------

1. The format in which GnuTLS parameters are cached (in the file gnutls-params
in the spool directory) has been changed. The new format can also be generated
externally, so it is now possible to update the values from outside Exim. This
has been implemented in an upwards, BUT NOT downwards, compatible manner.
Upgrading should be seamless: when Exim finds that it cannot understand an
existing cache file, it generates new parameters and writes them to the cache
in the new format. If, however, you downgrade from 4.51 to a previous release,
you MUST delete the gnutls-params file in the spool directory, because the
older Exim will not recognize the new format.

2. When doing a callout as part of verifying an address, Exim was not paying
attention to any local part prefix or suffix that was matched by the router
that accepted the address. It now behaves in the same way as it does for
delivery: the affixes are removed from the local part unless
rcpt_include_affixes is set on the transport. If you have a configuration that
uses prefixes or suffixes on addresses that could be used for callouts, and you
want the affixes to be retained, you must make sure that rcpt_include_affixes
is set on the transport.

3. Bounce and delay warning messages no longer contain details of delivery
errors, except for explicit messages (e.g. generated by :fail:) and SMTP
responses from remote hosts.


Version 4.50
------------

The exicyclog script has been updated to use three-digit numbers in rotated log
files if the maximum number to keep is greater than 99. If you are already
keeping more than 99, there will be an incompatible change when you upgrade.
You will probably want to rename your old log files to the new form before
running the new exicyclog.


Version 4.42
------------

RFC 3848 specifies standard names for the "with" phrase in Received: header
lines when AUTH and/or TLS are in use. This is the "received protocol"
field. Exim used to use "asmtp" for authenticated SMTP, without any
indication (in the protocol name) for TLS use. Now it follows the RFC and
uses "esmtpa" if the connection is authenticated, "esmtps" if it is
encrypted, and "esmtpsa" if it is both encrypted and authenticated. These names
appear in log lines as well as in Received: header lines.


Version 4.34
------------

Change 4.31/2 gave problems to data ACLs and local_scan() functions that
expected to see a Received: header. I have changed to yet another scheme. The
Received: header is now generated after the body is received, but before the
ACL or local_scan() is called. After they have run, the timestamp in the
Received: header is updated.

Thus, change (a) of 4.31/2 has been reversed, but change (b) is still true,
which is lucky, since I decided it was a bug fix.


Version 4.33
------------

If an expansion in a condition on a "warn" statement fails because a lookup
defers, the "warn" statement is abandoned, and the next ACL statement is
processed. Previously this caused the whole ACL to be aborted.


Version 4.32
------------

Change 4.31/2 has been reversed, as it proved contentious. Recipient callout
verification now uses <> in the MAIL command by default, as it did before. A
new callout option, "use_sender", has been added to request the other
behaviour.


Version 4.31
------------

1. If you compile Exim to use GnuTLS, it now requires the use of release 1.0.0
   or greater. The interface to the obsolete 0.8.x releases is no longer
   supported. There is one externally visible change: the format for the
   display of Distinguished Names now uses commas as a separator rather than a
   slash. This is to comply with RFC 2253.

2. When a message is received, the Received: header line is now generated when
   reception is complete, instead of at the start of reception. For messages
   that take a long time to come in, this changes the meaning of the timestamp.
   There are several side-effects of this change:

    (a) If a message is rejected by a DATA or non-SMTP ACL, or by local_scan(),
        the logged header lines no longer include the local Received: line,
        because it has not yet been created. If the message is a non-SMTP one,
        and the error is processed by sending a message to the sender, the copy
        of the original message that is returned does not have an added
        Received: line.

    (b) When a filter file is tested using -bf, no additional Received: header
        is added to the test message. After some thought, I decided that this
        is a bug fix.

    The contents of $received_for are not affected by this change. This
    variable still contains the single recipient of a message, copied after
    addresses have been rewritten, but before local_scan() is run.

2. Recipient callout verification, like sender verification, was using <> in
   the MAIL FROM command. This isn't really the right thing, since the actual
   sender may affect whether the remote host accepts the recipient or not. I
   have changed it to use the actual sender in the callout; this means that
   the cache record is now keyed on a recipient/sender pair, not just the
   recipient address. There doesn't seem to be a real danger of callout loops,
   since a callout by the remote host to check the sender would use <>.


Version 4.30
------------

1. I have abolished timeout_DNS as an error that can be detected in retry
   rules, because it has never worked. Despite the fact that it has been
   documented since at least release 1.62, there was no code to support it.
   If you have used it in your retry rules, you will now get a warning message
   to the log and panic log. It is now treated as plain "timeout".

2. After discussion on the mailing list, Exim no longer adds From:, Date:, or
   Message-Id: header lines to messages that do not originate locally, that is,
   messages that have an associated sending host address.

3. When looking up a host name from an IP address, Exim now tries the DNS
   first, and only if that fails does it use gethostbyaddr() (or equivalent).
   This change was made because on some OS, not all the names are given for
   addresses with multiple PTR records via the gethostbyaddr() interface. The
   order of lookup can be changed by setting host_lookup_order.


Version 4.23
------------

1. The new FIXED_NEVER_USERS build-time option creates a list of "never users"
   that cannot be overridden. The default in the distributed EDITME is "root".
   If for some reason you were (against advice) running deliveries as root, you
   will have to ensure that FIXED_NEVER_USERS is not set in your
   Local/Makefile.

2. The ${quote: operator now quotes an empty string, which it did not before.

3. Version 4.23 saves the contents of the ACL variables with the message, so
   that they can be used later. If one of these variables contains a newline,
   there will be a newline character in the spool that will not be interpreted
   correctly by a previous version of Exim. (Exim ignores keyed spool file
   items that it doesn't understand - precisely for this kind of problem - but
   it expects them all to be on one line.)

   So the bottom line is: if you have newlines in your ACL variables, you
   cannot retreat from 4.23.


Version 4.21
------------

1. The idea of the "warn" ACL verb is that it adds a header or writes to the
   log only when "message" or "log_message" are set. However, if one of the
   conditions was an address verification, or a call to a nested ACL, the
   messages generated by the underlying test were being passed through. This
   no longer happens. The underlying message is available in $acl_verify_
   message for both "message" and "log_message" expansions, so it can be
   passed through if needed.

2. The way that the $h_ (and $header_) expansions work has been changed by the
   addition of RFC 2047 decoding. See the main documentation (the NewStuff file
   until release 4.30, then the manual) for full details. Briefly, there are
   now three forms:

     $rh_xxx: and $rheader_xxx: give the original content of the header
       line(s), with no processing at all.

     $bh_xxx: and $bheader_xxx: remove leading and trailing white space, and
       then decode base64 or quoted-printable "words" within the header text,
       but do not do charset translation.

     $h_xxx: and $header_xxx: attempt to translate the $bh_ string to a
       standard character set.

   If you have previously been using $h_ expansions to access the raw
   characters, you should change to $rh_ instead.

3. When Exim creates an RFC 2047 encoded word in a header line, it labels it
   with the default character set from the headers_charset option instead of
   always using iso-8859-1.

4. If TMPDIR is defined in Local/Makefile (default in src/EDITME is
   TMPDIR="/tmp"), Exim checks for the presence of an environment variable
   called TMPDIR, and if it finds it is different, it changes its value.

5. Following a discussion on the list, the rules by which Exim recognises line
   endings on incoming messages have been changed. The -dropcr and drop_cr
   options are now no-ops, retained only for backwards compatibility. The
   following line terminators are recognized: LF CRLF CR. However, special
   processing applies to CR:

   (i)  The sequence CR . CR does *not* terminate an incoming SMTP message,
        nor a local message in the state where . is a terminator.

   (ii) If a bare CR is encountered in a header line, an extra space is added
        after the line terminator so as not to end the header. The reasoning
        behind this is that bare CRs in header lines are most likely either
        to be mistakes, or people trying to play silly games.

6. The code for using daemon_smtp_port, local_interfaces, and the -oX options
   has been reorganized. It is supposed to be backwards compatible, but it is
   mentioned here just in case I've screwed up.



Version 4.20
------------

1. I have tidied and re-organized the code that uses alarm() for imposing time
   limits on various things. It shouldn't affect anything, but if you notice
   processes getting stuck, it may be that I've broken something.

2. The "arguments" log selector now also logs the current working directory
   when Exim is called.

3. An incompatible change has been made to the appendfile transport. This
   affects the case when it is used for file deliveries that are set up by
   .forward and filter files. Previously, any settings of the "file" or
   "directory" options were ignored. It is hoped that, like the address_file
   transport in the default configuration, these options were never in fact set
   on such transports, because they were of no use.

   Now, if either of these options is set, it is used. The path that is passed
   by the router is in $address_file (this is not new), so it can be used as
   part of a longer path, or modified in any other way that expansion permits.

   If neither "file" nor "directory" is set, the behaviour is unchanged.

4. Related to the above: in a filter, if a "save" command specifies a non-
   absolute path, the value of $home/ is pre-pended. This no longer happens if
   $home is unset or is set to an empty string.

5. Multiple file deliveries from a filter or .forward file can never be
   batched; the value of batch_max on the transport is ignored for file
   deliveries. I'm assuming that nobody ever actually set batch_max on the
   address_file transport - it would have had odd effects previously.

6. DESTDIR is the more common variable that ROOT for use when installing
   software under a different root filing system. The Exim install script now
   recognizes DESTDIR first; if it is not set, ROOT is used.

7. If DESTDIR is set when installing Exim, it no longer prepends its value to
   the path of the system aliases file that appears in the default
   configuration (when a default configuration is installed). If an aliases
   file is actually created, its name *does* use the prefix.


Version 4.14
------------

1. The default for the maximum number of unknown SMTP commands that Exim will
accept before dropping a connection has been reduced from 5 to 3. However, you
can now change the value by setting smtp_max_unknown_commands.

2. The ${quote: operator has been changed so that it turns newline and carriage
return characters into \n and \r, respectively.

3. The file names used for maildir messages now include the microsecond time
fraction as well as the time in seconds, to cope with systems where the process
id can be re-used within the same second. The format is now

  <time>.H<microsec>P<pid>.<host>

This should be a compatible change, but is noted here just in case.

4. The rules for creating message ids have changed, to cope with systems where
the process id can be re-used within the same second. The format, however, is
unchanged, so this should not cause any problems, except as noted in the next
item.

5. The maximum value for localhost_number has been reduced from 255 to 16, in
order to implement the new message id rules. For operating systems that have
case-insensitive file systems (Cygwin and Darwin), the limit is 10.

6. verify = header_syntax was allowing unqualified addresses in all cases. Now
it allows them only for locally generated messages and from hosts that match
sender_unqualified_hosts or recipient_unqualified_hosts, respectively.

7. For reasons lost in the mists of time, when a pipe transport was run, the
environment variable MESSAGE_ID was set to the message ID preceded by 'E' (the
form used in Message-ID: header lines). The 'E' has been removed.


Version 4.11
------------

1. The handling of lines in the configuration file has changed. Previously,
macro expansion was applied to logical lines, after continuations had been
joined on. This meant that it could not be used in .include lines, which are
handled as physical rather than logical lines. Macro expansion is now done on
physical lines rather than logical lines. This means there are two
incompatibilities:

  (a) A macro that expands to # to turn a line into a comment now applies only
      to the physical line where it appears. Previously, it would have caused
      any following continuations also to be ignored.

  (b) A macro name can no longer be split over the boundary between a line and
      its continuation. Actually, this is more of a bug fix. :-)

2. The -D command line option must now all be within one command line item.
This makes it possible to use -D to set a macro to the empty string by commands
such as

  exim -DABC  ...
  exim -DABC= ...

Previously, these items would have moved on to the next item on the command
line. To include spaces in a macro definition item, quotes must be used, in
which case you can also have spaces after -D and surrounding the equals. For
example:

  exim '-D ABC = something' ...

3. The way that addresses that redirect to themselves are handled has been
changed, in order to fix an obscure bug. This should not cause any problems
except in the case of wanting to go back from a 4.11 (or later) release to an
earlier release. If there are undelivered messages on the spool that contain
addresses which redirect to themselves, and the redirected addresses have
already been delivered, you might get a duplicate delivery if you revert to an
earlier Exim.

4. The default way of looking up IP addresses for hosts in the manualroute and
queryprogram routers has been changed. If "byname" or "bydns" is explicitly
specified, there is no change, but if no method is specified, Exim now behaves
as follows:

  First, a DNS lookup is done. If this yields anything other than
  HOST_NOT_FOUND, that result is used. Otherwise, Exim goes on to try a call to
  getipnodebyname() (or gethostbyname() on older systems) and the result of the
  lookup is the result of that call.

This change has been made because it has been discovered that on some systems,
if a DNS lookup called via getipnodebyname() times out, HOST_NOT_FOUND is
returned instead of TRY_AGAIN. Thus, it is safest to try a DNS lookup directly
first, and only if that gives a definite "no such host" to try the local
function.

5. In fixing the minor security problem with pid_file_path, I have removed some
backwards-compatible (undocumented) code which was present to ease conversion
from Exim 3. In Exim 4, pid_file_path is a literal; in Exim 3 it was allowed to
contain "%s", which was replaced by the port number for daemons listening on
non-standard ports. In Exim 4, such daemons do not write a pid file. The
backwards compatibility feature was to replace "%s" by nothing if it occurred
in an Exim 4 setting of pid_file_path. The bug was in this code. I have solved
the problem by removing the backwards compatibility feature. Thus, if you still
have "%s" somewhere in a setting of pid_file_path, you should remove it.

6. There has been an extension to lsearch files. The keys in these files may
now be quoted in order to allow for whitespace and colons in them. This means
that if you were previously using keys that began with a doublequote, you will
now have to wrap them with extra quotes and escape the internal quotes. The
possibility that anybody is actually doing this seems extremely remote, but it
is documented just in case.


Version 4.10
------------

The build-time parameter EXIWHAT_KILL_ARG has been renamed EXIWHAT_KILL_SIGNAL
to better reflect its function. The OS-specific files have been updated. Only
if you have explicitly set this in your Makefile (highly unlikely) do you need
to change anything.

****