e-mail recovery

Is there any way to recover sent items from an Exchange 5.5. The sent items are not in the sent items or deleted folder. The server is not configured to retain deleted items either. What made me ask these question is because I went to the mailbox resources and saw that I have 1000 number of items. Yet when I went back to my outlook and added all the items in the diffrent folders it came to 750 items. Any idea where the 300 items could be found?