Hexamail Guard is a server based software antispam filter for the Windows and Linux platforms.
Acting as a gateway at the SMTP level or as a plugin for Microsoft Exchange Server, it supports most common anti spam filtering techniques including:
Bayesian pattern matching
DNS based blocklists
Hosted image blocking
Sender analysis using neural network
Automatic Internet updates to blocking features
IP Location Detection (geolocation detection of clients)
Detection of Spam NDRs
Sender Policy Framework
Optional antivirus scanning
In addition it supports external POP3 and IMAP 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.