Hi -

Seeing as this post has gone unanswered, I can give you my thoughts on your post. 

1. The ViewMail for Outlook form is installed in an organizational forms library/personal Outlook forms cache.  Organizational forms library is implemented differently in Exchange 2003 than in 2007.  I'm also thinking that Unity needs the Offline Address Book, which resides in Public Folders.  This is the step that is referenced in the Unity reconfiguration guide when moving from Exchange 2003 to Exchange 2007.  New Exchange 2007 organizations by default do not install Public Folders.

2. The typical procedure is to join a new Exchange 2007 server to an existing Exchange 2003 organization.  This allows Exchange 2003 servers to remain.  Some legacy integrations with Unity and other voicemail systems (Octel, AMIS, or VPIM), require the installation of a voice connector - which is only supported on Exchange 2003 servers.  New Exchange 2007 organizations do not allow Exchange 2003 servers to be added.  This configuration may not impact your deployment.

This may be a useful link from Microsoft on the architectural differences - http://technet.microsoft.com/en-us/library/bb397221.aspx

Before posting, I tried searching Cisco's knowledgebase and NetPro forum that confirms Unity's dependencies or use of the Offline Address Book, but I couldn't find anything specific.

Regards, Ginger