We had an issue this morning where our primary mail database went offline and no users could connect to Exchange. We bounced the server and everything appeared fine. Now one user cannot access his mailbox at all. I've tried to bounce the information store service and that didn’t resolve the issue. Exchange 2010 Version 14.0 Build 639.21, Single server all roles hosted on this server, on Server 2008 R2 Enterprise running on Hyper-V I see this in the Event Log The mailbox for user /o=Domain/ou=First Administrative Group/cn=Recipients/cn=UserName has been quarantined. Access to this mailbox will be restricted to administrative logons for the next 6 hours. I see this error when the user is logging in via OWA Exception type: Microsoft.Mapi.MapiExceptionMailboxQuarantined I see this in the event log after I try and open the users calendar tab in Exchange Management Console (PID 4608, Thread 22) Task Get-CalendarProcessing writing error when processing record of index 0. Error: Microsoft.Exchange.Data.Storage.StorageTransientException: Cannot open mailbox /o=Domain/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Configuration/cn=Servers/cn=SVTAMWORTH/cn=Microsoft System Attendant. ---> Microsoft.Mapi.MapiExceptionMailboxQuarantined: MapiExceptionMailboxQuarantined: Unable to open message store. (hr=0x80004005, ec=2611) Any help would sure be appreciated. Thanks!

OK I've got the issue resolved. Good info here http://social.technet.microsoft.com/Forums/en-US/exchange2010/thread/d9bb9ba7-537a-423a-95f9-a5c167aa7722/ and here http://blogs.technet.com/b/sjimmie/archive/2010/07/09/mailbox-quarantine.aspx I had to run this command in Power Shell get-mailbox -identity <user alias> |fl to find the mailbox GUID then I had to go into regedit to this location and remove the key that matched the mailbox GUID and then restart the Information Store HKLM\SYSTEM\CurrentControlSet\Services\MSexchangeIS\Servername\Private-dbguid\Quarantined Mailboxes\ {Mailbox guid}.