Apache SpamAssassin 3.3.0 offers a new way of updating rules for spam filtering. Now the rules database are separated from the main product and loaded through the automatic updates. This approach has been provided as an option in the previous versions.
SpamAssassin supports a huge number of filtration mechanisms, including text analysis, Bayesian filtering, DNS blocklists, collaborative filtering databases and much more. All these methods will help in the spam identification and reduce the false positive (ham incorrectly marked as spam).
You can download Apache SpamAssassin 3.3.0 here.