Using SBS2008 (Exchange 2007). We have a user who is missing all sent email more than a few days old, when using Outlook 2010. I've tried logging onto another PC, and without offline mode, but the same issue.
When using cached mode, "Sync Issues" shows a lot errors. These are a few of them:
21:07:04 Error synchronizing folder
21:07:04 The client operation failed.
21:07:04 Microsoft Exchange Information Store
When not using cached mode, then there are no sent emails at all. The Sent folder remains empty.
However, when using OWA, the email is present.
Also, there are Calendar sync failures, so when dismissing an event, the event is never dismissed, and returns a few moments later.