Hey All, I tried to add this to the a Exchange 2003 forum but there doesn't appear to be one in the list. So sorry about that. I have built up a new Windows Server 2003 and installed SP2 with all updates. I installed Exchange 2003 ontop after installing SMTP, IIS, NNTP and ASP.NET We already have other Exchange 2003 servers in our environment. The rest of our Exchange servers are working fine. The only thing I should mentioned is we have updated our AD Schema to Exchange 2010. Also the Public Folder Store is mounted on this server. After I create a new mailbox store on the new Exchange 2003 server I go to mount it I get the following events in my application log. EventID 9546: Failed to create the Event Registration Mailbox for Database First Storage Group\Mailbox Store (SERVER). Error - 0xbf69 & EventID 9519: Error 0x80004005 starting database "First Storage Group\Mailbox Store (SERVER)" on the Microsoft Exchange Information Store. I have gone through the accepted solution on this post here http://www.experts-exchange.com/Software/Server_Software/Email_Servers/Exchange/Q_21928103.html But I have had no joy, I have even rebuild the server from scratch and still ran into the same issue. Hopefully I just need to check a checkbox or I just need a good old face palm. Any suggestions are welcome :)