Exchange 2007 SP1 RU8 has been validated for HMC 4.0 and HMC 4.5http://blogs.technet.com/provtest/archive/2009/06/19/exchange-2007-sp1-ru8-has-been-validated-for-hmc-4-0-and-hmc-4-5.aspxOn a monthly basis, the HMC test team will conduct a Windows update compatibility test (where the major roll-ups and updates will be tested) on different versions of HMC environment. Windows update compatibility tests (Exchange 2007 SP1 RU8 was includeden-USCommunityServer 2.1 SP1 (Build: 61025.2)