What are some alternatives?
MailScanner - MailScanner is a open source email security system design for Linux-based email gateways.
Mailwasher - Over 8 million people use MailWasher as their spam filter
Altospam - Antispam and antivirus software on Cloud
Proxmox Mail Gateway - Protect mail server against spam, viruses and malware with Proxmox Mail Gateway security for businesses, government, education and non-profit organizations.
Spamihilator - The free Anti-Spam-Filter Spamihilator removes more than 98% of spam mails before they even get into your inbox.
amavisd-new - amavisd-new is a high-performance interface between mailer (MTA) and content checkers: virus...