A couple of months ago, we migrated from Exchange 2003 to Exchange 2010 and the 2003 has since been decommissioned. It wasn't an entirely smooth process because we've experienced some strange instances which most have been fixed. Otherwise, the server is running fairly smoothly now.
Ever since we migrated, at random periods, some of my local Outlook 2010 users reported Outlook stopped updating mail folders because they noticed they weren't getting any new messages in their Inbox. In the status bar, it shows a previous date/time when it was last updated instead of "All folders are up to date".
Closing Outlook and restarting it resolves the problem temporarily. Deleting the Mail Profile and re-creating it fixes it for a while. Turning off Cached Mode fixes it, too, but we've also had a couple of remote users who need Cached Mode turned on for better performance.
Any ideas on why this is happening?