With the help of the python.org postmasters I figured something out about spam on the python-list@python.org mailing list over the weekend. I was confused that some seemingly obvious spams made it through to the mailing list subscribers. Then I noticed that it didn't appear these spams had even seen the spam filter. The headers the filter adds were missing and I could never find their Message-Id's in the spam filter's logs.
Mailman operates the bidirectional gateway between the Usenet newsgroup comp.lang.python and the python-list@python.org mailing list. When it sees a Usenet message on the one side it distributes the posting directly to its subscribers, and vice versa. Because Usenet postings don't arrive by email the spam filtering we have in place (which occurs before Mailman sees a mail message) is not done. Mailman happily passes such unfiltered mail on to the list.
I still haven't figured out quite how to solve the problem. In theory we could use some other tool to perform the gateway operation. Instead of passing Usenet postings directly to Mailman it would mail them to python-list@python.org where they would get the spam filter treatment before Mailman sees them. I'm still thinking about the full ramifications of that. It might be easier to get Mailman's news-to-mail gateway to mail incoming Usenet messages to the list address instead of directly distributing them to the subscribers though. I don't believe Mailman does that out of the box (but I would love to be wrong here). Has anyone tried implementing that? If so, got a patch or a recipe for how to configure Mailman to operate this way?
Thanks,
-- Skip Montanaro - skip@pobox.com - http://smontanaro.dyndns.org/