More than 20,000 copies of scaled-down beta versions of the new products have been downloaded from Microsoft's Web site over the past year, the company said.

The final version of each of the new packages will be available through volume licensing programs starting July 1, Microsoft said.

Antigen for Exchange starts at US$10.50 per user annually for subscriptions of 250 users or fewer, and subscriptions for the Messaging Security suite start at $14.50 per user for similar volumes, Microsoft said.

A key feature of the Antigen antivirus products is support for multiple scanning engines from vendors such as Sophos PLC, Norman Data Defense Systems Inc. and CA Inc. to help users detect viruses, spam and other malware, said Joe Licari, director of product management at Microsoft. The latest Microsoft tools also include a scanning engine, he noted.

Dan Blum, an analyst at Burton Group in Midvale, Utah, said the use of multiple engines at the server or gateway level could prove interesting to enterprise customers.