BitDefender Mail Protection is a powerful mail filtering solution that provides antivirus and antispam capabilities to Linux mail servers. Both sent and received messages are scanned in real-time, avoiding possible infections and preventing anyone from sending an infected message. It claims a 100% detection rate for all viruses in the wild through its powerful scanning engines, which are certified by prestigious testing labs.
IVS Milter is a virus, spam, and content milter. It makes use of the antivirus package ClamAV, and can also seamlessly integrate SpamAssassin (either spamc or libspamc). IVS Milter is also plugin based and currently supports virus scanning, spam scanning, content-type matching, attachment type matching, and attachment filename matching.
MailScanner is an email virus scanner, vulnerability protector, and spam tagger. It supports the Postfix, Sendmail, Exim, Qmail, and ZMailer MTAs, and the Sophos, McAfee, F-Prot, F-Secure, CommandAV, InoculateIT, Inoculan, eTrust, Kaspersky, Nod32, AntiVir, BitDefender, RAV, Panda, DrWeb, ClamAV, and other anti-virus scanners. It uses SpamAssassin for highly successful spam identification, and is designed to handle denial of service attacks. It will detect password-protected zip files and apply filename checking to their contents. It is very easy to install, requires no changes at all to your sendmail.cf file, is designed to be lightweight, and won't grind your mail system to a halt with its load. It can be integrated into any email system, regardless of the software in use.
OpenFWTK is an application proxy toolkit which inherits the ideology of TIS fwtk and maintains API backwards compatibility. The design goal is to make it simple yet powerful; no performance hacks are allowed in the code and library dependencies are reduced to a minimum. It is a true application layer filter. It features unified pluggable content inspection for the most frequently used protocols, NAC (Network Admission Control), and the ability to define fine-grained Internet access policy based on browser identification.