Mailman -- The GNU Mailing List Management System --
is a mailing list management system written mostly in
Python. Features:

o Most standard mailing list features, including:
moderation, mail based commands, digests, etc...
o An extensive Web interface, customizable on a per-list basis.
o Web based list administration interface for *all* admin-type tasks
o Automatic Web based hypermail-style archives (using pipermail or
other external archiver), including provisions for private archives
o Integrated mail list to newsgroup gatewaying
o Integrated newsgroup to mail list gatewaying (polling-based... if you
have access to the nntp server, you should be able to easily do
non-polling based news->mail list gatewaying; email viega@list.org,
I'd like to help get that going and come up
with instructions)
o Smart bounce detection and correction
o Integrated fast bulk mailing
o Smart spam protection
o Extensible logging
o Multiple list owners and moderators are possible
o Optional MIME-compliant digests
o Nice about which machine you subscribed from if you're from the
right domain

Conditional build options:
mailman uid --with uid mail
mailman gid --with gid mail