Interestingly enough, since posting last, McAfee has contacted me a few times because they are getting more organizations reporting the same issue. McAfee has had me try to apply a test patch and when that didn't work, they started asking additional information on the problem and how our Exchange server and Outlook clients were configure. There is still no resolution.
We have a ticket open with Microsoft to investigate this performance symptom.
What we know is -
- it involves Outlook 2010 (if you have a different version you are experiencing a different problem).
- the larger a User's calendar the more exaggerated the lag/delay
- disabling our EmailScan feature provides a workaround/relief to the symptom
We are currently reviewing code to determine if there's an opportunity for optimization.
A note about EmailScan:
If the Exchange is already protected by an AV solution then the client-side VSE feature of EmailScan is redundant.
EmailScan works by copying the mail+attachments to a temporary local folder for scanning. All-the-while, the Outlook client is "locked" until the scan is complete, to prevent Users gaining access to infected items. This potential lag can be particularly painful for remote users and large attachments.