Corporate Antispam Solutions

Linux Mail Servers or other SMTP servers

Hexamail Guard
Kaspersky Anti-Spam Enterprise Edition
Declude MailProtector
Ruckus MailFILTER
Vorras Classifier
GWAVA for Novell GroupWise
Trend Micro

Exchange

MailSite MP Email Gateway Software
Symantec Premium AntiSpam
Hexamail Guard
MailFender for Exchange Server
iQ.Suite
Pro Exchange Spam Smacker
XWall
modusGate™ MS Exchange Anti-Spam Gateway
GWAVA for Microsoft Exchange
Trend Micro

Windows

BCware NoSpam
Pinjo
DynaComm i:mail
MAILsweeper Business Suite
SpamBolt
Surf Control
AlliGate
Spam Sleuth Enterprise
NetIQ MailMarshal
Visnetic MailScan
Omniquad Mailwall
Lightspeed Total Traffic Control
SMTPTrap
Philter
Fluffy the SMTPGuardDog
Catch!
IDRSMTPProxy
Spam Manager Professional
MailMax
eTrust Secure Content Manager
Leon
mxORB
GWGuardian
Rockliffe MailSite MP
ADVmserve

Gateway (Appliance or Installable Software)

Astaro Security Gateway
Alligate (Windows)
IMGate (FreeBSD 7)
Symantec Brightmail Gateway
iQ.Suite (Windows \ ISA)
Axway MailGate (Linux)
XWall
Active SMTP
ModusGate Antispam Appliance
MXtreme
Cloudmark Authority
SpamTitan
MailFoundry
iForce Mail Firewall
Barracuda Networks
Roaring Penguin CanIt Appliance
SpamKiller 3000 series Appliances
Watchguard Spamscreen
Arska Mailwall
Bizanga

Domino

M-Switch Anti-Spam
Symantec Premium AntiSpam (Exchange and Domino)
SpamSentinel
MIMEShield    

Service (Third party Hosted MX) – Subscription Based

SpamSentinel
MailSite MP Email Gateway Software
Declude MailProtector
Postini (Now a Google service)
Mxpolice
SPAMfighter
MXGuarddog
CudaMail
Remote Anti Spam
GFI MAX MailProtection