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.
Sendmail Sender Address Validator is a lightweight, fast, and reliable Sendmail milter that implements a real-time Sender email Address Verification technology. This can stop some kinds of spam with a spoofed sender's email address. It also implements real-time Recipient email Address Verification, which can be useful if your machine is a backup MX for the recipient's domains, or if your machine forwards all email messages as a relay host for your domains to another internal or external email servers. It is a light alternative for the spamilter, milter-sender, and milter-ahead milters.
milter-spamassassin is a lightweight, reliable, and fast Sendmail plug-in for the SpamAssassin mail filter. It uses advanced statistical and heuristic tests to identify SPAM built into spamd (the SpamAssassin daemon program). This filter has a hosts/networks whitelist, scans messages less than a defined size, rejects SPAM messages at the DATA stage of SMTP session, copies SPAM messages into the special "garbage" mailbox, performs Subject tagging if SPAM is detected, and adds an information header to scanned messages.
milter-clamav is a lightweight, reliable, and fast Sendmail plug-in for the ClamAV antivirus scanner. It uses a mail scanning engine built into clamd (the ClamAV daemon program). This filter scans messages less than a defined size, rejects infected messages at the DATA stage of SMTP session, and adds an information header to scanned messages.
milter-spamblocker is a lightweight, reliable, and very fast Sendmail plug-in designed to reject spam and Internet worms. It blocks up to 99% of spam and up to 99.9% of Internet worms. You will not need to pay for the garbage traffic now. It has a flexible configuration, real-time sender and recipient email address verification technology with autowhitelist, smart anti zombie technology, safe anti backscattering technology, smart GreyListing technology with autowhitelist, and a low level of false positives.