http://blogs.technet.com/b/ilvancri/archive/2010/08/10/ocs-2007-r2-and-exchange-2010-ru4-did-the-remote-peer-accept-our-certificate.aspx  Configuring the link between OCS 2007 R2 and Exchange 2007/Exchange 2010 seems pretty easy, and it all boils down to: Getting the rights certificates: does the Common Name match the FQDN of the Exchange UM server, and the one used by OCS, doesen-USTelligent Evolution Platform Developer Build (Build: 5.6.50428.7875)