A new product family called Antigen will be added to your WSUS server in the next few days. The Antigen product category will include updates, including service packs, optional updates, and critical or security updates, for the Microsoft® Antigen 9 for Exchange and Microsoft® Antigen 9 for SMTP. Antigen product updates are going to be offered through Microsoft Update and WSUS. Updates offered through this category will apply only to computers running Antigen 9 for Exchange and SMTP with Service Pack 1 version or later. For additional information on Antigen product family, see http://go.microsoft.com/fwlink/?LinkId=181883.
The WSUS Team