I'm currently using SpamAssassin on a couple of mail servers that I look after. SpamAssassin runs in the context of amavisd-new on those servers and with the usual bunch of plugins (FuzzyOCR, DCC, pyzor, razor). Currently the servers are getting their rule updates from the default SpamAssassin update channel (updates.spamassassin.org). Overall the setup seems to be reasonably effective but some types of spam seem to wander right through it even though I've made repeated attempts at training spamassassin. My guesstimate is that about 85%-90% of the spam that gets through policyd-weight makes it through the filters and it's been getting a lot worse recently as spammers are getting better at working their way through filters.

Can someone recommend additional sources of filters to make SpamAssassin more effective? So far I've found OpenProtect's update channel but are there others worth looking at?