First of all, there's only one way to be sure. Create a testmailbox, send some big files to yourself and vice versa. Back it up, then delete everything in the mailbox (like a normal user would do), then restore, see if you're missing something.
When I get this error, the Exchange server normally hangs with no particular reason. CA told me to go to the vendor for support, vendor told me to go to CA or get a contract (wich is not an option because I refuse to pay for a full contract for just one issue).
The damned thing about CA is that you can get support for the usual stuff like rights, servicepacks and Micro$oft issues. When you get deeper into one of their problems they just stop calling back.
We're only talking about the brick level here, you can always restore the whole priv & pub (if you have a spare server wich is powerful enough to host a complete Exchange system).