Paul Wise writes:

A generic mailing-list-hoster hosting all 3 of those will want to allow most mail and add per-list filters.

Of course. SpamAssassin at least can already do that (it allows mailbox-specific rules).

A properly set up Bayesian filter will notice that certain criteria are associated with list addressees. (Not as effective as explicit training on each individual corpus, but I was never very good about that, and I doubt few list admins will bother.)

Can we really do better than those? If not, we should concentrate on (1) exporting policy based on Mailman databases to MTAs via milters, and/or (2) importing existing functionality from existing spam filters such as SpamAssassin to Mailman. The big problem with (2) is that it has already been done; it's only a few lines in a Handler.

Steve