More than 6000 contacts and having trouble synching with Exchange 2010

[ron_in_oc]

My situation: I use VPN to connect to a corporate network and synch contacts, calendar, and email with an Microsoft Exchange server (used to be the 2007 version, now the 2010 version). Total number of my contacts is something more than 6000 and emails number more than 500 per day.

My problem: my corporate contacts list is often incomplete and my calendar not updated. I also don't seem to be able to make email synch only when manually selected - it shows up whenever it wants. I've seen this on a Droid 2, Droid 2 Global, and Droid 3. I've tried fiddling with most of the possible settings for synching and nothing seems to make the problem go away.

My question: am I bumping into some limitation of Android? Verizon tech support has been very supportive but haven't been able to help. Does anyone have any insights?