I am experiencing similar issue with delayed UDP notifications when using a MAPI application connecting to Exchange 2007 on Windows Server 2008 . Do you have a reference number / KB number to the MS hotfix that corrected the Unity issue? The same application works fine on Exchange 2003 / Windows Server 2003.
What version of BES are you running? The Exchange hotfix I applied because of my Unity issue did not resolve the Outlook sent items delay on BB issue. When I installed SP6 for BES 4.1 that resolved my issue.