Microsoft today announced availability of the public betas of Microsoft? Exchange Server 2007 and the new Forefront Security for Exchange Server (next generation of Microsoft Antigen for Exchange)
Exchange Server 2007 beta 2 is available for download at http://www.microsoft.com/exchange/beta2, and Forefront Security for Exchange Server beta can be downloaded from http://www.microsoft.com/forefront/serversecurity/exchange/download-beta.mspx.

Microsoft PR via TechMeme