Recreate and enable missing arbitration user accounts and mailboxes in Exchange Serve These are a couple of article explaining the process of recreating and enable missing arbitration users and mailboxes. It addresses the issue of lost or deleted system mailboxes and how to get them back. How to recreate missing arbitration user accounts in 2010 http://social.technet.microsoft.com/wiki/contents/articles/5317.recreate-and-enable-missing-arbitration-user-accounts-and-mailboxes-in-exchange-server-2010.aspx How to recreate System Mailbox , FederatedEmail & DiscoverySearchMailbox in Exchange 2010 http://careexchange.in/how-to-recreate-system-mailbox-federatedemail-discoverysearchmailbox-in-exchange-2010/