A question from a school in Utah:
The scenario was their Outlook Voice Access (OVA) was not correctly announcing the caller when the user was in a different dial plan defined in UM. This problem occurs if the voice mail message is from a user who is authenticated against a different dial plan. OVA announces "Unrecognized caller" even though the caller address is resolved correctly in Microsoft Office Outlook and in Microsoft Office Outlook Web Access.
I found the fix: download and install Update Rollup 3 for Exchange 2007 Service Pack 1. You can grab rollup3 here:
949870 Description of Update Rollup 3 for Exchange Server 2007 Service Pack 1