SpamAssassin is an extensible email filter that is used to identify and mark (not delete) spam. SpamAssassin works by labelling spam, with the configuration option ‘rewrite_header subject’, any emails that fail the spam identification metrics, which are configured using the ‘required_score’ option. An email client can then create a new rule for emails that watches for a title with the keywords set in the rewire_header subject (such as [SPAM] and then forward those e