2003->2010 migration MapiExceptionLogonFailed
Ran across a problem this morning when trying to migrate mailboxes from Exchange 2003 to Exchange 2010. Kept getting an error stating the mailbox database was offline and it was unable to make a connection to the server.
To resolve this problem I just went to the Exchange 2003 mailbox store, opened the security tab, and added the new Exchange 2010 to have full control. Afterwards everything moved perfectly!