Microsoft Outlook 2010 introduced several new features.  Unfortunately, it removed one feature that many organizations utilize: sent items & deleted items support for shared mailboxes.  By default, Outlook 2010 will place all sent items and deleted items in the user's mailbox.  The issue with this is that users of a shared mailbox cannot see what emails have been sent out or deleted.  In Outlook 2007, you could manually enable this feature by adding a registry key.  This doesn't work the same way in Outlook 2010.  There is a fix though.