Created new doc file containing specs for the experimental features,
[exim.git] / src / README.UPDATING
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1$Cambridge: exim/src/README.UPDATING,v 1.1 2004/10/06 14:12:40 ph10 Exp $
2
3This document contains detailed information about incompatibilities that might
4be encountered when upgrading from one release of Exim to another. The
5information is in reverse order of release numbers. Mostly these are relatively
6small points, and the configuration file is normally upwards compatible, but
7there have been two big upheavals...
8
9
10**************************************************************************
11* There was a big reworking of the way mail routing works for release *
12* 4.00. Previously used "directors" were abolished, and all routing is *
13* now done by routers. Policy controls for incoming mail are now done by *
14* Access Control Lists instead of separate options. All this means that *
15* pre-4.00 configuration files have to be massively converted. If you *
16* are coming from a 3.xx release, please read the document in the file *
17* doc/Exim4.upgrade, and allow some time to complete the upgrade. *
18* *
19* There was a big reworking of the way domain/host/net/address lists are *
20* handled at release 3.00. If you are coming from a pre-3.00 release, it *
21* might be easier to start again from a default configuration. Otherwise *
22* you need to read doc/Exim3.upgrade and do a double conversion of your *
23* configuration file. *
24**************************************************************************
25
26
27The rest of this document contains information about changes in 4.xx releases
28that might affect a running system.
29
30
31Version 4.42
32------------
33
34RFC 3848 specifies standard names for the "with" phrase in Received: header
35lines when AUTH and/or TLS are in use. This is the "received protocol"
36field. Exim used to use "asmtp" for authenticated SMTP, without any
37indication (in the protocol name) for TLS use. Now it follows the RFC and
38uses "esmtpa" if the connection is authenticated, "esmtps" if it is
39encrypted, and "esmtpsa" if it is both encrypted and authenticated. These names
40appear in log lines as well as in Received: header lines.
41
42
43Version 4.34
44------------
45
46Change 4.31/2 gave problems to data ACLs and local_scan() functions that
47expected to see a Received: header. I have changed to yet another scheme. The
48Received: header is now generated after the body is received, but before the
49ACL or local_scan() is called. After they have run, the timestamp in the
50Received: header is updated.
51
52Thus, change (a) of 4.31/2 has been reversed, but change (b) is still true,
53which is lucky, since I decided it was a bug fix.
54
55
56Version 4.33
57------------
58
59If an expansion in a condition on a "warn" statement fails because a lookup
60defers, the "warn" statement is abandoned, and the next ACL statement is
61processed. Previously this caused the whole ACL to be aborted.
62
63
64Version 4.32
65------------
66
67Change 4.31/2 has been reversed, as it proved contentious. Recipient callout
68verification now uses <> in the MAIL command by default, as it did before. A
69new callout option, "use_sender", has been added to request the other
70behaviour.
71
72
73Version 4.31
74------------
75
761. If you compile Exim to use GnuTLS, it now requires the use of release 1.0.0
77 or greater. The interface to the obsolete 0.8.x releases is no longer
78 supported. There is one externally visible change: the format for the
79 display of Distinguished Names now uses commas as a separator rather than a
80 slash. This is to comply with RFC 2253.
81
822. When a message is received, the Received: header line is now generated when
83 reception is complete, instead of at the start of reception. For messages
84 that take a long time to come in, this changes the meaning of the timestamp.
85 There are several side-effects of this change:
86
87 (a) If a message is rejected by a DATA or non-SMTP ACL, or by local_scan(),
88 the logged header lines no longer include the local Received: line,
89 because it has not yet been created. If the message is a non-SMTP one,
90 and the error is processed by sending a message to the sender, the copy
91 of the original message that is returned does not have an added
92 Received: line.
93
94 (b) When a filter file is tested using -bf, no additional Received: header
95 is added to the test message. After some thought, I decided that this
96 is a bug fix.
97
98 The contents of $received_for are not affected by this change. This
99 variable still contains the single recipient of a message, copied after
100 addresses have been rewritten, but before local_scan() is run.
101
1022. Recipient callout verification, like sender verification, was using <> in
103 the MAIL FROM command. This isn't really the right thing, since the actual
104 sender may affect whether the remote host accepts the recipient or not. I
105 have changed it to use the actual sender in the callout; this means that
106 the cache record is now keyed on a recipient/sender pair, not just the
107 recipient address. There doesn't seem to be a real danger of callout loops,
108 since a callout by the remote host to check the sender would use <>.
109
110
111Version 4.30
112------------
113
1141. I have abolished timeout_DNS as an error that can be detected in retry
115 rules, because it has never worked. Despite the fact that it has been
116 documented since at least release 1.62, there was no code to support it.
117 If you have used it in your retry rules, you will now get a warning message
118 to the log and panic log. It is now treated as plain "timeout".
119
1202. After discussion on the mailing list, Exim no longer adds From:, Date:, or
121 Message-Id: header lines to messages that do not originate locally, that is,
122 messages that have an associated sending host address.
123
1243. When looking up a host name from an IP address, Exim now tries the DNS
125 first, and only if that fails does it use gethostbyaddr() (or equivalent).
126 This change was made because on some OS, not all the names are given for
127 addresses with multiple PTR records via the gethostbyaddr() interface. The
128 order of lookup can be changed by setting host_lookup_order.
129
130
131Version 4.23
132------------
133
1341. The new FIXED_NEVER_USERS build-time option creates a list of "never users"
135 that cannot be overridden. The default in the distributed EDITME is "root".
136 If for some reason you were (against advice) running deliveries as root, you
137 will have to ensure that FIXED_NEVER_USERS is not set in your
138 Local/Makefile.
139
1402. The ${quote: operator now quotes an empty string, which it did not before.
141
1423. Version 4.23 saves the contents of the ACL variables with the message, so
143 that they can be used later. If one of these variables contains a newline,
144 there will be a newline character in the spool that will not be interpreted
145 correctely by a previous version of Exim. (Exim ignores keyed spool file
146 items that it doesn't understand - precisely for this kind of problem - but
147 it expects them all to be on one line.)
148
149 So the bottom line is: if you have newlines in your ACL variables, you
150 cannot retreat from 4.23.
151
152
153Version 4.21
154------------
155
1561. The idea of the "warn" ACL verb is that it adds a header or writes to the
157 log only when "message" or "log_message" are set. However, if one of the
158 conditions was an address verification, or a call to a nested ACL, the
159 messages generated by the underlying test were being passed through. This
160 no longer happens. The underlying message is available in $acl_verify_
161 message for both "message" and "log_message" expansions, so it can be
162 passed through if needed.
163
1642. The way that the $h_ (and $header_) expansions work has been changed by the
165 addition of RFC 2047 decoding. See the main documentation (the NewStuff file
166 until release 4.30, then the manual) for full details. Briefly, there are
167 now three forms:
168
169 $rh_xxx: and $rheader_xxx: give the original content of the header
170 line(s), with no processing at all.
171
172 $bh_xxx: and $bheader_xxx: remove leading and trailing white space, and
173 then decode base64 or quoted-printable "words" within the header text,
174 but do not do charset translation.
175
176 $h_xxx: and $header_xxx: attempt to translate the $bh_ string to a
177 standard character set.
178
179 If you have previously been using $h_ expansions to access the raw
180 characters, you should change to $rh_ instead.
181
1823. When Exim creates an RFC 2047 encoded word in a header line, it labels it
183 with the default character set from the headers_charset option instead of
184 always using iso-8859-1.
185
1864. If TMPDIR is defined in Local/Makefile (default in src/EDITME is
187 TMPDIR="/tmp"), Exim checks for the presence of an environment variable
188 called TMPDIR, and if it finds it is different, it changes its value.
189
1905. Following a discussion on the list, the rules by which Exim recognises line
191 endings on incoming messages have been changed. The -dropcr and drop_cr
192 options are now no-ops, retained only for backwards compatibility. The
193 following line terminators are recognized: LF CRLF CR. However, special
194 processing applies to CR:
195
196 (i) The sequence CR . CR does *not* terminate an incoming SMTP message,
197 nor a local message in the state where . is a terminator.
198
199 (ii) If a bare CR is encountered in a header line, an extra space is added
200 after the line terminator so as not to end the header. The reasoning
201 behind this is that bare CRs in header lines are most likely either
202 to be mistakes, or people trying to play silly games.
203
2046. The code for using daemon_smtp_port, local_interfaces, and the -oX options
205 has been reorganized. It is supposed to be backwards compatible, but it is
206 mentioned here just in case I've screwed up.
207
208
209
210Version 4.20
211------------
212
2131. I have tidied and re-organized the code that uses alarm() for imposing time
214 limits on various things. It shouldn't affect anything, but if you notice
215 processes getting stuck, it may be that I've broken something.
216
2172. The "arguments" log selector now also logs the current working directory
218 when Exim is called.
219
2203. An incompatible change has been made to the appendfile transport. This
221 affects the case when it is used for file deliveries that are set up by
222 .forward and filter files. Previously, any settings of the "file" or
223 "directory" options were ignored. It is hoped that, like the address_file
224 transport in the default configuration, these options were never in fact set
225 on such transports, because they were of no use.
226
227 Now, if either of these options is set, it is used. The path that is passed
228 by the router is in $address_file (this is not new), so it can be used as
229 part of a longer path, or modified in any other way that expansion permits.
230
231 If neither "file" nor "directory" is set, the behaviour is unchanged.
232
2334. Related to the above: in a filter, if a "save" command specifies a non-
234 absolute path, the value of $home/ is pre-pended. This no longer happens if
235 $home is unset or is set to an empty string.
236
2375. Multiple file deliveries from a filter or .forward file can never be
238 batched; the value of batch_max on the transport is ignored for file
239 deliveries. I'm assuming that nobody ever actually set batch_max on the
240 address_file transport - it would have had odd effects previously.
241
2426. DESTDIR is the more common variable that ROOT for use when installing
243 software under a different root filing system. The Exim install script now
244 recognizes DESTDIR first; if it is not set, ROOT is used.
245
2467. If DESTDIR is set when installing Exim, it no longer prepends its value to
247 the path of the system aliases file that appears in the default
248 configuration (when a default configuration is installed). If an aliases
249 file is actually created, its name *does* use the prefix.
250
251
252Version 4.14
253------------
254
2551. The default for the maximum number of unknown SMTP commands that Exim will
256accept before dropping a connection has been reduced from 5 to 3. However, you
257can now change the value by setting smtp_max_unknown_commands.
258
2592. The ${quote: operator has been changed so that it turns newline and carriage
260return characters into \n and \r, respectively.
261
2623. The file names used for maildir messages now include the microsecond time
263fraction as well as the time in seconds, to cope with systems where the process
264id can be re-used within the same second. The format is now
265
266 <time>.H<microsec>P<pid>.<host>
267
268This should be a compatible change, but is noted here just in case.
269
2704. The rules for creating message ids have changed, to cope with systems where
271the process id can be re-used within the same second. The format, however, is
272unchanged, so this should not cause any problems, except as noted in the next
273item.
274
2755. The maximum value for localhost_number has been reduced from 255 to 16, in
276order to implement the new message id rules. For operating systems that have
277case-insensitive file systems (Cygwin and Darwin), the limit is 10.
278
2796. verify = header_syntax was allowing unqualified addresses in all cases. Now
280it allows them only for locally generated messages and from hosts that match
281sender_unqualified_hosts or recipient_unqualified_hosts, respectively.
282
2837. For reasons lost in the mists of time, when a pipe transport was run, the
284environment variable MESSAGE_ID was set to the message ID preceded by 'E' (the
285form used in Message-ID: header lines). The 'E' has been removed.
286
287
288Version 4.11
289------------
290
2911. The handling of lines in the configuration file has changed. Previously,
292macro expansion was applied to logical lines, after continuations had been
293joined on. This meant that it could not be used in .include lines, which are
294handled as physical rather than logical lines. Macro expansion is now done on
295physical lines rather than logical lines. This means there are two
296incompatibilities:
297
298 (a) A macro that expands to # to turn a line into a comment now applies only
299 to the physical line where it appears. Previously, it would have caused
300 any following continuations also to be ignored.
301
302 (b) A macro name can no longer be split over the boundary between a line and
303 its continuation. Actually, this is more of a bug fix. :-)
304
3052. The -D command line option must now all be within one command line item.
306This makes it possible to use -D to set a macro to the empty string by commands
307such as
308
309 exim -DABC ...
310 exim -DABC= ...
311
312Previously, these items would have moved on to the next item on the command
313line. To include spaces in a macro definition item, quotes must be used, in
314which case you can also have spaces after -D and surrounding the equals. For
315example:
316
317 exim '-D ABC = something' ...
318
3193. The way that addresses that redirect to themselves are handled has been
320changed, in order to fix an obscure bug. This should not cause any problems
321except in the case of wanting to go back from a 4.11 (or later) release to an
322earlier release. If there are undelivered messages on the spool that contain
323addresses which redirect to themselves, and the redirected addresses have
324already been delivered, you might get a duplicate delivery if you revert to an
325earlier Exim.
326
3274. The default way of looking up IP addresses for hosts in the manualroute and
328queryprogram routers has been changed. If "byname" or "bydns" is explicitly
329specified, there is no change, but if no method is specified, Exim now behaves
330as follows:
331
332 First, a DNS lookup is done. If this yields anything other than
333 HOST_NOT_FOUND, that result is used. Otherwise, Exim goes on to try a call to
334 getipnodebyname() (or gethostbyname() on older systems) and the result of the
335 lookup is the result of that call.
336
337This change has been made because it has been discovered that on some systems,
338if a DNS lookup called via getipnodebyname() times out, HOST_NOT_FOUND is
339returned instead of TRY_AGAIN. Thus, it is safest to try a DNS lookup directly
340first, and only if that gives a definite "no such host" to try the local
341function.
342
3435. In fixing the minor security problem with pid_file_path, I have removed some
344backwards-compatible (undocumented) code which was present to ease conversion
345from Exim 3. In Exim 4, pid_file_path is a literal; in Exim 3 it was allowed to
346contain "%s", which was replaced by the port number for daemons listening on
347non-standard ports. In Exim 4, such daemons do not write a pid file. The
348backwards compatibility feature was to replace "%s" by nothing if it occurred
349in an Exim 4 setting of pid_file_path. The bug was in this code. I have solved
350the problem by removing the backwards compatibility feature. Thus, if you still
351have "%s" somewhere in a setting of pid_file_path, you should remove it.
352
3536. There has been an extension to lsearch files. The keys in these files may
354now be quoted in order to allow for whitespace and colons in them. This means
355that if you were previously using keys that began with a doublequote, you will
356now have to wrap them with extra quotes and escape the internal quotes. The
357possibility that anybody is actually doing this seems extremely remote, but it
358is documented just in case.
359
360
361Version 4.10
362------------
363
364The build-time parameter EXIWHAT_KILL_ARG has been renamed EXIWHAT_KILL_SIGNAL
365to better reflect its function. The OS-specific files have been updated. Only
366if you have explicitly set this in your Makefile (highly unlikely) do you need
367to change anything.
368
369****