Vote for GroupShield
GroupShield for Exchange attempts to detect both existing and new viruses in the Exchange environment by utilizing the VS-API from Microsoft. Functionality includes; Content Filtering - the ability to block or quarantine files based on the subject line as well as the file name, type and size, Multi-node Active-Active cluster support and integration with the Microsoft Management Console (MMC). Also included is McAfee Outbreak Manager, which looks for suspicious e-mail behavioral patterns to stop new e-mail borne threats.