If you are the exchange administrator you will have rights to open that mailbox. If you are unable to do so you can grant yourself full access through the exchange managment console. I would work with the end user if at all possible. What do they mean by duplicates? It is possible they have rules set up and if an email meets the criteria of more than one rule it can create multiple copies in multiple folders. I have done this myself. If it is indeed multiple copies to the base inbox then you need to review that with the end user. If that is not possible then open their mailbox yourself in its own profile to troubleshoot. This is a legitimate reason to view their mailbox. Mailboxes on Exchange servers inside a company domain belong to the company not the user.