I am having an issue with one users mailbox taht will not open. I moved it from 2003 to 2010 a couple of months ago and it just started to act up. I couldn't get it to connect anymore to Outlook so I tried to export the mailbox to a pst so I could delete the mailbox and recreate it. When I go to export I get this message. I only get it with this one user. VERBOSE: [14:43:20.207 GMT] New-MailboxExportRequest : Couldn't connect to the source mailbox. --> MapiExceptionNetworkError: Unable to open message store. (hr=0x80004005, ec=2423)

Hi Ronald, Can you see below thread where several suggestion have given for this error in move mailbox. http://social.technet.microsoft.com/Forums/en-GB/exchange2010/thread/c0cb3ed8-f964-4c63-acd2-344a26088d39 Anil

Hello Ronald, Does this issue occur when exporting the mailbox for other users? Try moving the problematic mailbox to another mailbox store and it will fix the potential corruption automatically. Thanks, Simon