Limited Root Authorities in Windows 2008 Server

I discovered a somewhat irritating issue with Windows 2008 today. I’m trying to build an OCS Access Edge (AE) and want to federate with another company running Windows 2008. I can connect remote access clients to the public Internet with no issues, but federation fails with no errors — except federated contacts display in MOC as “presence unknown.” How do I resolve this “presence unknown” display issue?

As many of you are probably aware, Windows 2003 comes with a larger number of root authorities (i.e., list of third-party certificates that the operating system will “trust”). Unlike Windows 2003, Windows 2008 has a much smaller list. Make sure that the root authority certificate from your AE that is running Windows 2008 is also in the trusted root authority list of the federated partner. For example, the root authority certificate for Comodo is NOT installed by default on Windows 2008.