Recently had an issue with a customer who was in the middle of an Exchange 2007 to Exchange 2010 migration. After moving some test users, there was a bug exposed with a separate vendor’s (not Microsoft Exchange) unified messaging system. The UM vendor needed to apply a patch that had to be scheduled for a later date. The bug prevented users from receiving Voicemails on their desk phones and being able to call in and check their VM’s.
As a workaround, we moved the users who had been migrated to Exchange 2010, back to Exchange 2007. After the move, the UM worked fine, but the users rules were broken, all except for Client Side rules.
Turns out it is a bug with Exchange 2007 SP3, that is resolved in Exchange 2007 SP3 RU7 available here:
The workaround (not recommended) is to run isinteg on the specified database that contains users having the issue. This is ONLY if you do not want to install the update. Below is the specific KB page regarding the issue: