You seem to have two issues here:
a) He cannot view sent items folder
b) He cannot write sent items folder. (This is probably why the mail stays in outbox.)
This suggests that either the user does not own his mailbox (or at least the Sent Itemsfolder), or he has been put into the permissions list and locked out of it.
Have the user log in as himself, and then let you drive. Check out the following:
1. In the folder list, right-click on his Sent Items folder, and select properties. Someone may have accidently changed some settings. Especially check the permissions tab, and make sure that the user is NOT in the premission list (he should own the folder, and thus have permissions).
You may get an error when you try to view permissions. If so, this is a sure sign that the user is not the owner of the folder. You may need to correct this in the Exchange Server manager program.
You might try deleting his Sent Items folder as the admin, and then have him log in as himselfand create a new folder called Sent Items. (I have not tried this.)
Worst case, you may have to have him copy all his mail to local folders, then you delete his entire mail box and recreate it.
2. As the user, check the preferences to make sure that the "Keep a copy in Sent Items" box is checked.
Good luck.
