Barracuda Networks Spam Firewall
   The Barracuda Spam Firewall handles over 10 million messages a day, without bogging down your email servers. [Hardware]
   http://www.barracudanetworks.com

CanIt
   CanIt is a flexible server-based anti-spam solution built around SpamAssassin. [Unix]
   http://www.roaringpenguin.com/

Corvigo, Inc.
   Intent based filtering technology. Simply better e-mail. You plug it in, and all that junk email just goes away. [Hardware]
   http://www.corvigo.com

Debian open source gateway email spam filter
   Explains how to build a Debian anti-spam and anti-virus gateway E-mail server using Postfix, amavisd-new, SpamAssassin, Razor, DCC, Pyzor and ClamAV.[Unix]
   http://www200.pair.com/mecham/spam/

Declude JunkMail
   Advanced spam control using many different tests with a variety of possible actions to take on spam. [Windows]
   http://www.declude.com/

ESCOM Corporation
   The Active SMTP Appliance is a hardware appliance that dynamically filters and quarantines junk e-mail before it gets to the mail server. [Hardware]
   http://www.escom.com

Extensible Messaging Platform - Anti-Spam Firewall
   Software intercepts spam, email-borne viruses, and other objectionable content before reaching your organization's mail server by utilizing complex contextual signatures as opposed to simple keyword lists. [Unix, Windows]
   http://www.jak.com/spam-filter/spam-filter.htm

Filtering Spam with Spamassassin on Redhat 9
   How to filter spam with Spamassassin on Redhat 9. [Unix]
   http://evillair.netdojo.com/howto/spamassassin.html

Hamster RBL-Check for Windows
   Free open-source software for users of the free Windows Hamster local news and mail server, to filter out spam using any of the publicly available Realtime Block Lists (RBL). [Windows]
   http://leggewie.biz/hamster.htm

HartSoft Catch
   Advanced E-mail proxy incorporating Spamassassin. [Windows]
   http://www.hartsoft.com

Hijack Protection from anonymous Dial-in Access
   Prevents SMTP hijacking (outgoing spam) of the respective MX SMTP Server from anonymous Dial-In Users. [Unix]
   http://www.init7.net/anti-spam/

JSpamFilter
   JSpamFilter is Java-based, performs both source and content filtering, and provides a variety of treatment options. It is high-performance and highly customizable. [Java]
   http://www.modestsoftware.com/jspamfilter.cfm

Mail Warden Pro
   Mail Warden Pro is E-mail server security software with anti-spam, anti-virus and content filtering for any mailserver. [Windows]
   http://www.seattlelab.com/products/mailwardenpro/default.asp

MailChannels
   MailChannels eliminates false positives by using a new technique using subdomains in E-mail addresses. [Windows]
   http://www.mailchannels.com

MailFoundry Antispam Appliance
   A very effective anti-spam appliance. MailFoundry creates a spam firewall for effectively stopping spam. [hardware]
   http://www.solinus.com/mailfoundry/

MailFrontier
   An internet security company offering solutions to prevent spam, phishing, viruses, policy violations, and denial of service attacks. [Hardware]
   http://www.mailfrontier.com/

MailShield
   MailShield filters e-mail before it gets to the mail server. Customizable. Free trial available. [Unix,Windows]
   http://www.lyris.com/products/mailshield/

MailStripper
   MailStripper is an SMTP-level spam filter with antivirus capability for Linux, FreeBSD and Solaris. [Unix]
   http://www.eridani.co.uk/MailStripper/

Message Sniffer
   Accurate, multi-platform spam filter updated several times per day using 60,000+ heuristics. Typically scans messages in under 200 milliseconds on modest hardware. [Unix,Windows]
   http://www.sortmonster.com/MessageSniffer/

Pinjo
   Spam control using Blacklists, mark spam by modifying subject, anti relay possiblities. [Windows]
   http://www.pinjo.nl/

PowerElf II
   The PowerElf II anti-spam appliance uses several different techniques to help stop spam at its entry point, before it has a chance to travel to the end-user’s mailbox. [Hardware]
   http://www.greencomputer.com/products/powerelf2/features/antispam.shtml

RBL Spam Daemon
   A small, fast, open-source spam filter. Designed to work with or replace SpamAssassin. Uses DNSBL lookups to discriminate spam. [Unix]
   http://rblsd.sourceforge.net/

SMTPD Spammer Deterrent
   Patched version of Obtuse SMTPD that provides content filtering and tar pitting. [Unix]
   http://sd.inodes.org/

SMTPTrap.com
   Spam killer software. It blocks spam before it is even delivered to your mail server. [Windows]
   http://www.smtptrap.com

SPAMFilter ISP
   Anti-spam software that acts as a proxy to existing SMTP servers. Filters E-mail based on DNS blacklists and individual filters such as keywords, IP, From address. [Unix,Windows]
   http://www.logsat.com/sfi.asp

STAT AntiSpam Software Project
   Perl based spam and anti-virus filters. The content of individual messages and their attachments is analyzed across several broad categories. The program works with the Mercury32 email server. [Windows]
   http://www.stat-communications.com/antispam/

Spam Sleuth Enterprise
   Anti-spam software that filters spam, viruses, web bugs, and phishing scams. Eliminates unwanted junk e-mail from corporate servers. [Windows]
   http://www.bluesquirrel.com/products/spamsleuthenterprise/

Spam filters & email security - ePrism secure email filter & spam control filter
   ePrism is an email filter and spam filtering appliance that provides organizations with a total secure email perimeter defense solution. [Hardware]
   http://spam-filters.stbernard.com

Tethernet, Inc.
   Tethernet TetherFilter is an easy to deploy, affordable anti-spam and anti-virus appliance that can be used in front of any existing Internet email server. [Hardware]
   http://www.tethernet.com

Using Exim 4 ACLs
   This article explains how to set up ACLs in Exim 4 to reject spam.
   http://www.maretmanu.org/homepage/inform/exim-spam.html

White List Email (WLE)
   Challenge/response system. Multi-platform filtering free software written on Python. WLE requires a confirmation from unknown senders before delivering their mail in your mailbox. [Unix]
   http://www.rfc1149.net/devel/wle

jASEN
   A Java program using a Chi Square algorithm to detect spam. It is best suited to developers wishing to integrate anti-spam services into an existing server based java E-mail application, but can be used for client applications. [Java]
   http://jasen.sourceforge.net

mxGuard
   The purpose of this add-on is to intercept each message passing through the IMail server. It then runs a range of tests to determine if the message is unsolicited commercial e-mail (UCE), commonly referred to as junk mail or spam. [Windows]
   http://www.mxguard.com/postmaster

trimMail Inbox
   Appliance filters mail coming into your network for spam and dangerous content. [Hardware]
   http://www.trimmail.com