The SpamAssassin plugin provides anti-spam capabilities for Claws Mail. SpamAssassin is a complete spam checker, featuring local tests, remote tests, Bayesian filtering, and more. It is written in perl. This complete set of checks makes it really good at catching spam, at the expense of filtering rather slowly. Claws Mail also provides a Bogofilter anti-spam plugin, which does only Bayesian filtering, making it faster than SpamAssassin. The SpamAssassin plugin features are:

• Filtering spam when mail is received, and moving it to a specific folder or destroying it completely
• Learning what is spam and what is ham, in order to better filter your mailbox
• The ability to use a remote SpamAssassin server for filtering and learning

SpamAssassin can begin filtering your emails right away, as it isn't only a Bayesian filter; but you should correct it with the learning feature if you get false positives or false negatives.

SpamAssassin is required, http://spamassassin.apache.org/

Here are a few screenshots illustrating the features:

• Helping SpamAssassin learn from a missed spam:
  
   
   
• Checking for false positives in the Spam folder. It looks like SpamAssassin did a good job…