Hexamail Guard is a server based software antispam filter for the Windows

Microsoft Windows

Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...

 and Linux

Linux

Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...

 platforms.

Acting as a gateway at the SMTP

Simple Mail Transfer Protocol

Simple Mail Transfer Protocol is an Internet standard for electronic mail transmission across Internet Protocol networks. SMTP was first defined by RFC 821 , and last updated by RFC 5321 which includes the extended SMTP additions, and is the protocol in widespread use today...

 level or as a plugin for Microsoft Exchange Server

Microsoft Exchange Server

Microsoft Exchange Server is the server side of a client–server, collaborative application product developed by Microsoft. It is part of the Microsoft Servers line of server products and is used by enterprises using Microsoft infrastructure products...

, it supports most common anti spam filtering techniques including:

• Bayesian pattern matching
• Keyword/String/Expression
• Header checks
• DNS based blocklists
• URL blocklists
• Image analysis
• Hosted image blocking
• Sender analysis using neural network
• Cloaking/Phishing detection
• Challenge-Response
• Blacklisting
• User-configurable whitelists
• Automatic Internet updates to blocking features
• Honeypot Matching
• Grey Listing
• IP Location Detection (geolocation detection of clients)
• Detection of Spam NDRs
• Domain Keys
• Sender Policy Framework
• Optional antivirus scanning

In addition it supports external POP3

Post Office Protocol

In computing, the Post Office Protocol is an application-layer Internet standard protocol used by local e-mail clients to retrieve e-mail from a remote server over a TCP/IP connection. POP and IMAP are the two most prevalent Internet standard protocols for e-mail retrieval. Virtually all modern...

account downloading and filtering, a spam quarantine with multiple options for processing including: listing, forwarding, blocking, marking/tagging and deletion. Users can review their own spam through a web-based quarantine view.