I was having an error moving a mailbox from Microsoft Exchange 5.5 to 2003:
Unable to move mailbox ‘MyMailbox’.
Error: The MAPI call failed.
MAPI or an unspecified service provider.
ID no: 80004005-0000-00000000
The Move wizard would go through most of the user’s messages before returning the error. I checked the Active Directory account, and it was valid, with appropriate permissions for SELF. The cause of the error was that the user’s mailbox size was larger than the storage limit. I temporarily increased the storage limit, and the mailbox moved with no further difficulties.