[Mailman-Developers] anti-spam filter

[Stephen J. Turnbull]

Pratik Sarkar writes:

 > Coming back to the project,do we need to write patches for the
 > SpamAssassin or SpamBayes(which are integrated in Mailman)

No.  You write a Handler which delegates to those external packages.
A Handler is a sort of plug-in.

 > or do we need to start over and make a whole new filter and start
 > reinventing the wheels?

Don't do that unless you think you can write a filter that does a
significantly better job on some dimension than the existing ones.

 > And somewhere I read that the filtering of messages posted by
 > non-subscribed members are done manually.

That's incorrect.  Mailman's mail processing is architected as a
pipeline of Handlers.  Each Handler can act as a filter, or edit the
message, or perform a side effect (delivering the mail to subscribers
or saving it in an archive), then passes the message on to the next
Handler (unless it raises an exception).  Filters have a selection of
options: throw away the message silently (DISCARD), return to sender
(REJECT), quarantine (HOLD), or pass on for further processing.  (The
words in all uppercase are actually exception names.)  One of the
filters checks whether the mail is from a subscriber, but it is not
otherwise special, and in principle both subscribers and
non-subscribers may be subject to various filters.