SpamAssasin is email filtering system that attempts to identify spam messages in the emails headers and body. It can be enabled by going to SpamAssasin in the Mail section and clicking Enable SpamAssasin. Also, you can adjust how many hits is required before mail is considered as spam by selecting score number. Default value is 5. To delete spam automatically, click Auto-Delete Spam and to disable spam auto deletion, click Disbale Auto-Delete Spam.

You also can configure different settings for SpamAssasin. For example, you can add email addresses to blacklist and whitelist. Adjust how many hits is required before mail is marked as spam.