How to prevent users (including domain admins) from accessing other mailboxes

By default users cannot access others mail boxes. Now in case if you have given permissions to user to access other mail boxes, you need to remove them.Check the permissions on the mail boxes and see if every one is given some kind of permissions on the mail boxes.Raj

Yes, I agree with Rajnish. That is including Domain Admins, can't access other domain users mailboxes since Domain Admins group has Send-As and Receive-As deny permission inherited from the organizational level. Amit Tank MVP: Exchange Server | MCTS: Microsoft Exchange Server 2010, Configuration | MCITP: EMA | MCSA: M Blog: http://ExchangeShare.WordPress.com | User Group: http:/MUC-UG.org.in