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/