I've been using DSPAM for some time now and have recently upgraded
to 3.2.3 from [old] ... at some point, they switched the default
storage backend from Berkeley DB which I hate more with each passing day to SQLite... it also supports various SQL (My, Postgres, Oracle) for big deployments.

I have been quite happy with it. It works really really well
once trained.

DSPAM 3.2.3 Release Notes