There are a number of open source discussion lists I've been subscribed to over the past decade (usenet, then Google Groups) that have recently migrated to hosted Discourse boards because of Google's lack of spam fighting tools. Who cares about what the listservs UI looks like, the entire point is to receive and send email. Lets help build good spam fighting capabilities into mailman and others so all of our knowledge isn't locked into these walled-garden communities.

Actually mailman 3 can help fighting spam:

* Since data is now in SQL, it's easier to interact with the DB and have simple tools delete spammers. * Since there's an exposable API now, it's possible to develop systems that interact with mailman and help with the issue.