I know this, but I do not understand what kind of integration is necessary between Unity Connection and Lotus Notes.
Unity connection is a Voice Mail solution and it does not integrate with Lotus, the only possible integration is when you configure IMAP, but it does not depend on the mail server (Exchage or Microsot). Isn't it?
Unity is a Unified Messaging solution and in this case it integrate the mail box with Exchange of Lotus. I this case it make sense to chosse between Domino and Exchange. Isn't it?
Can you give me more information?