Today I was working on a user's account who could not get any new emails to the device. Contacts sync, Calendar syncs, but emails did not (only checked Mailbox not subfolders.) User could send emails fine.
Tried a lot of things including changing groupwise connector user settings to not sync Mail, save, then turn it back on. Deleting and recreating the account. Every time I recreated the account I would get all emails up to that point but after that nothing would come through to the server. Pending mail would not increase in Mobility monitor.
The only odd thing I was seeing is this in the groupwise-Appinterface log
2010-11-09 15:10:57.295 WARNING_VERBOSE [Thread-23] [gwconnectorlogic:187] [userID:] [eventID:] [objectID:]  Was notified of events for user bfransma, but none were present!
The problem was the user had Mailbox and many other cabinets etc in the Work in Progress folder. I moved the Mailbox etc back to Home and then had to delete and recreate the account on the datasync server.