CallManager 4.x for interoperability with Exchange UM is now officially supported.
It will helps customers by not forcing an upgrade to CCM5+ and therefore locking the customer down to Cisco’s platform for a longer period of time.
Additionally, Cisco Unity is now not the only large platform that will support CCM4 for a voice mail in the inbox experience.
More details at http://technet.microsoft.com/en-us/library/cc164342.aspx