Spamihilator - The free Anti-Spam-Filter Spamihilator removes more than 98% of spam mails before they even get into your inbox.
SpamAssassin - Use this program to "Unspam" your mailbox(es).
Mailwasher - Over 8 million people use MailWasher as their spam filter
MailScanner - MailScanner is a open source email security system design for Linux-based email gateways.
Rspamd - Rspamd is an advanced spam filtering system that allows evaluation of messages by a number of rules...
Spam Reader - Spam Reader is a free anti-spam add-on for Microsoft Outlook.