[Mailman-Developers] Overhauled 'Exim and Mailman' doc

Greg Ward gward@mems-exchange.org
Fri, 11 Oct 2002 21:44:33 -0400

Hi all --

I've just spent the last couple of hours beating the README.EXIM
document from Mailman's current CVS tree into shape.  (This is derived
from Nigel Metheringham's "HOWTO - Using exim and Mailman together"
document, which can be found at www.exim.org.)

I reorganized the document, rewrote lots of text, reformatted just about
everything, simplified the Exim configuration code, and removed some
obsolete-looking stuff.  The document is now all about Mailman 2.1 on
Exim 3 or Exim 4; it doesn't explain how to have cohabiting MM 2.0 and
2.1 installations (although it should be possible -- I'm doing it on
mems-exchange.org with a config nearly identical to what's in the doc,
and Barry Warsaw is doing it on python.org with something vaguely

Exim-oids, please take a look at the hairy-scary routers/directors/
transports and make sure they look sane to you.  You could even test
them for me if you're feeling inclined; I have *not* actually tested
what I'm about to present.  Will do so sooner or later, I promise.  At
least with Exim 4 -- I don't use Exim 3 anywhere anymore.

Mailman-heads, I don't think there's much here for you, unless you're
also an Exim-oid, in which case see above.  Of course you should all
read this for clarity and grammar and so forth.  ;-)

Here 'tis:

Using Exim and Mailman Together

[This is derived from Nigel Metheringham's "HOWTO - Using exim and
 Mailman together", which covers Mailman 2.0.x and Exim 3.  It
 has been updated to cover Mailman 2.1 and Exim 4.  The original
 document is here: http://www.exim.org/howto/mailman.html]

Mailman configuration

There is no Mailman configuration needed other than the standard options
detailed in the Mailman install documentation.  The Exim configuration
is transparent to Mailman.  The uid/gid settings for Mailman must match
those in the config fragments given below.

Exim configuration

The Exim configuration is built so that a list created within Mailman
automatically appears to Exim without the need for defining any
additional aliases.

The drawback of this configuration is that it will work poorly on
systems supporting lists in several different mail domains.  While
Mailman handles virtual domains, it does not yet support having two
lists with the same name in different virtual domains, using the same
Mailman installation.  This will eventually change.  (But see below for
a variation on this scheme that should accomodate virtual domains

The configuration file excerpts below are for use in an already
functional Exim configuration, which accepts mail for the domain in
which the list resides.  If this domain is separate from the others
handled by your Exim configuration, then you'll need to:

  * add the list domain, "my.list.domain" to local_domains

  * add a "domains=my.list.domain" option to each of the directors
    (routers) for the list

  * (optional) exclude that domain from the other directors (routers)

[Note: the instructions in this document should work with either Exim 3
or Exim 4.  In Exim 3, you must have a 'local_domains' configuration
setting; in Exim 4, you most likely have a 'local_domains' domainlist.
If you don't, you probably know what you're doing and can adjust
accordingly.  Similarly, in Exim 4 the concept of "directors" has
disappeared -- there are only routers now.  So if you're using Exim 4,
whenever this document says "director", read "router".]

Whether you are using Exim 3 or Exim 4, you will need to add some macros
to the main section of your Exim config file.  You will also need to
define one new transport.  With Exim 3, you'll need to add two new
directors; with Exim 4, two new routers play the same role.

Finally, the configuration supplied here should allow co-habiting
Mailman 2.0 and 2.1 installations, with the proviso that you'll probably
want to use "mm21" in place of "mailman" -- e.g., MM21_HOME,
mm21_transport, etc.

Main configuration settings

First, you need to add some macros to the top of your Exim config file.
These just make the directors (routers) and transport below a bit
cleaner.  Obviously, you'll need to edit these based on how you
configured and installed Mailman.

  # Home dir for your Mailman installation -- aka Mailman's prefix
  # directory.

  # User and group for Mailman, should match your --with-mail-gid
  # switch to Mailman's configure script.

Transport for Exim 3

Add this to the transports section of your Exim config file,
i.e. somewhere between the first and second "end" line:

    driver = pipe
    command = MAILMAN_WRAP \
              ${if def:local_part_suffix \
                   {post}} \
    current_directory = MAILMAN_HOME
    home_directory = MAILMAN_HOME
    user = MAILMAN_UID
    group = MAILMAN_GID

Directors for Exim 3

If you're using Exim 3, you'll need to add the following two directors
to your config file (directors go between the second and third "end"
lines).  Also, don't forget that order matters -- eg. you can make
Mailman lists take precedence over system aliases by putting these
directors in front of your aliasfile director, or vice-versa.

  # Director to handle a list's main posting address.  Should come first
  # in case there's a list named, eg. "mailman-owner".  Automatically
  # detects list existence by looking for lists/$local_part/config.pck
  # under MAILMAN_HOME.
    driver = smartuser
    require_files = MAILMAN_HOME/lists/$local_part/config.pck
    transport = mailman_transport

  # Handle all the other addresses related to a list: -bounces, -admin,
  # etc.  Same trick works to detect list existence thanks to the
  # 'suffix' option.
    driver = smartuser
    require_files = MAILMAN_HOME/lists/$local_part/config.pck
    suffix = -bounces : -bounces+* : \
             -confirm+* : -join : -leave : \
             -owner : -request : -admin
    transport = mailman_transport

Routers for Exim 4

In Exim 4, there's no such thing as directors -- you instead need to add
two routers.  Also, the canonical order of the configuration file was
changed so routers come before transports, so the routers for Exim 4
come first here.  Put these two routers somewhere after the "begin
routers" line of your config file, and remember that order matters.

    driver = accept
    require_files = MAILMAN_HOME/lists/$local_part/config.pck
    transport = mailman_transport

    driver = accept
    require_files = MAILMAN_HOME/lists/$local_part/config.pck
    local_part_suffix = -bounces : -bounces+* : \
                        -confirm+* : -join : -leave : \
                        -owner : -request : -admin
    transport = mailman_transport

Transports for Exim 4

The transport for Exim 4 is the same as for Exim 3; just copy the
transport given above to somewhere under the "begin transports" line of
your Exim config file.


Exim should be configured to allow reasonable volume -- e.g. don't
setting max_recipients down to a silly value -- and with normal degrees
of security -- specifically, be sure to allow relaying from,
but pretty much nothing else.  Parallel deliveries and other tweaks can
also be used if you like; experiment with your setup to see what works.
Delay warning messages should be switched off or configured to only
happen for non-list mail, unless you like receiving tons of mail when
some random host is down.


  * Mailman will send as many MAIL FROM/RCPT TO as it needs. It may result
    in more than 10 or 100 messages sent in one connection, which will exceed
    the default value of Exim's smtp_accept_queue_per_connection
    This is bad because it will cause Exim to switch into queue mode and
    severely delay delivery of your list messages.
    The way to fix this is to set mailman's SMTP_MAX_SESSIONS_PER_CONNECTION
    (in ~mailman/Mailman/mm_cfg.py) to a smaller value than Exim's

  * Mailman should ignore Exim delay warning messages, even though
    Exim should never send this to list messages.  Mailman 2.1's
    general bounce detection and VERP support should greatly improve
    the bounce detector's hit rates.

  * List existence is checked on whether there is a config.pck file
    for a list.  If you delete lists by foul means, be aware of this.

  * If you are getting Exim or Mailman complaining about user ids
    when you send mail to a list, check that the MAILMAN_UID and
    MAILMAN_GID match those of Mailman itself (i.e. what were used
    in the configure script).  Also make sure you do not have
    aliases in the main alias file for the list.

Doing VERP with Exim and Mailman

VERP will send one email, with a separate envelope sender (return path),
for each of your subscribers -- read the information in
~mailman/Mailman/Default.py for the options that start with VERP.  In a
nutshell, all you need to do to enable VERP with Exim is to add these
lines to ~mailman/Mailman/mm_cfg.py:


(The directors/routers above are smart enough to deal with VERP

Virtual Domains

One approach to handling virtual domains is to use a separate Mailman
installation for each virtual domain.  (Currently, this is the only way
to have lists with the same name in different virtual domains handled by
the same machine.)

In this case, the MAILMAN_HOME and MAILMAN_WRAP macros are useless --
you can remove them.  Change your directors (routers) to something like

  require_files = /virtual/${domain}/mailman/lists/${lc:$local_part}/config.pck

and change your transport like this:

  command = /virtual/${domain}/mailman/mail/mailman \
            ${if def:local_part_suffix \
                 {post}} \
  current_directory = /virtual/${domain}/mailman
  home_directory = /virtual/${domain}/mailman

List Verification

This is how a set of address tests for the Exim lists look on a working
system for the quixote-users@mems-exchange.org list ("% " indicates the
Unix shell prompt):

  % exim -bt quixote-users
    router = mailman_main_router, transport = mailman_transport

  % exim -bt quixote-users-request
    router = mailman_router, transport = mailman_transport

  % exim -bt quixote-users-bounces
    router = mailman_router, transport = mailman_transport

  % exim -bt quixote-users-bounces+luser=example.com
    router = mailman_router, transport = mailman_transport

Document History

Originally written by Nigel Metheringham <postmaster@exim.org>.
Updated by Marc Merlin <marc_soft@merlins.org> for Mailman 2.1, Exim 4.
Overhauled/reformatted/clarified/simplified by Greg Ward <gward@python.net>.

Greg Ward - software developer                gward@mems-exchange.org
MEMS Exchange                            http://www.mems-exchange.org