http://blogs.technet.com/provtest/archive/2009/06/02/why-should-i-backup-my-oab-public-folder-server.aspxWe all know that in HMC environment has recommended that we should have dedicated Exchange Public Folder servers hosting purely just the Offline Address Books (OAB). You need the OAB Public Folder server in HMC 3.5 and HMC 4.0 if you want to allow youren-USCommunityServer 2.1 SP1 (Build: 61025.2)