Hi -
If you are referring to Unity's partner server, it doesn't do this automatically. You must run the Unity Message Store Configuration Wizard to select a new partner server for Unity. Also, before you do this, ensure the Unity permissions wizard has been run to include the information stores on the new Exchange server. Synchronization occurs normally with Unity 4.x and AD/Exchange. When I've run the Message Store config wizard, I've not needed to force synchronization. You may be thinking about Unity's DC/GC Reconnect tool, which automatically selects another available DC and GC (recommended), but does not apply to Exchange.
Ginger
