The good folks over at sourceforge do an excellent job providing a home for open source software. They have some excellent services as well.
However, of late I have been having a lot of problems with spam in the mailing lists. The user mailing list for the project that I administer there has been set to accept mail from non-subscribers. Sourceforge has SpamAssasin running on their servers which would correctly identify spam emails, but it would pass it through as would Sourceforge’s MTA and Mailman.
Not being an expert on Mailman, the first thing I did was to set up for administering all non-member posts, but this got to be a headache pretty soon.
That is till I discovered SPAM filters on Mailman (Privacy Options > Spam filters). I added the following header filter, and wallah my troubles were over!
These headers are set by SpamAssasin and other mail filters up the chain.