Error details: MapiExceptionNotFound: Unable to delete mailbox. (hr=0x8004010f, ec=-2147221233)
I am currently working on an Exchange 2003 to Exchange 2010 migration. During the migration I had an issue which caused that the old mailboxes were not cleaned up correctly and the user was not converted to a mail user. The first issue can happen even if everything is configured correctly. The only solution at this moment is to run the cleanup agent which can be found in the Exchange System Manager__.