This document contains detailed information about changes and 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 upgrades to 4.xx releases.


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.

****
