I have Unified Messaging setup between Unity Connection 8.6(2) and Exchange 2010 SP1. When a voicemail is left in the subscribers UC box, it is delivered to exchange and the MWI light comes on as it should. However, when the users views the email in Outlook, and it becomes read, the MWI light stays on. It seems as if exchange is unable to communicate to UC that the message as been read or even deleted.
I am not sure where to look next to see why exchange won't synchronize with UC.