PostArmor (formerly MailArmor) helps to keep your electronic mailbox free of spam: it looks at the relevant parts of your email before it leaves the mail server, and lets the legitimate messages pass through undisturbed, while leaving suspect messages on the server to be reexamined later or just deleted after a while. It works as a POP3 email proxy, with support for POP, APOP, and IMAP servers. It supports SpamCop reports and blacklist, and the ORDB and OSIRUSOFT blacklists.
fk_html is a standard filter for incoming mail. It runs on your local machine as a fake POP3 server that redirects your mail client connections to your real POP3 server. Doing that it can scan, filter, and convert your incoming emails and is totally independent from your mail client type or version It provides multiple account settings, conversion from HTML mail to plaintext mail, removal of scripts from HTML mail and attachments, address filtering based on blocklist and allowlist, the ability to apply different policies to different accounts, and SSL support (also for non-secure clients, in which case only the loopback connection is not encrypted).
MailStripper Pro is a mail scanner that aims to remove spam and viruses from incoming mail. It recognises and decodes many obfuscation techniques used by spammers and uses several different mechanisms to recognise spam which are immune to Bayes poisoning, and has achieved real-world success of over 99.8%. It is MTA-independent and does not implant itself into your mail server. Instead, it functions as a proxy, allowing the MTA to reside on a different server.
The Gordano Messaging Suite (GMS) is a highly flexible and reliable suite of messaging products. Customers can choose which components meet their needs from email, Webmail, collaboration, instant messaging, calendaring, SMS, and list server software all of which can be complimented by high level anti-spam, anti-virus, and archiving options.
P3Scan is a full transparent proxy server for email clients. It runs on a Linux box with iptables (for port redirection). It can be used to provide email scanning from the Internet to any internal network, and is ideal for helping to protect your "Other OS" LAN from harm, especially when used in conjunction with a firewall and other Internet proxy servers. It is designed to enable scanning of incoming email messages for viruses, worms, trojans, spam, and harmful attachments. Because viewing HTML email can enable a spammer to validate an email address (via Web bugs), it can also provide HTML stripping.