Sagator is an email antivirus/antispam gateway. It is an interface to the postfix, sendmail, or any other smtpd, which runs antivirus and/or spamchecker. It's modular architecture can use any combination of antivirus/spamchecker according to configuration.

https://www.salstar.sk/sagator/
http://www.tecmint.com/install-sagator-antivirus-antispam-protection-postfix-mail-server/