We had a strange problem where moving the mailbox solved the issue. What exactly happens when a mailbox is moved that could cause this? Is the mailbox re-created, re-indexed, etc? We're very curious as to why this resolved our problem. BTW: The problem was that our user could not receive email from a certain external email address (just one in particular). Moving the mailbox resolved the issue.

Could have been a corrupt mailbox rule that was dropped when the mailbox was moved.

Do you know if there is a white paper that describes in detail the process of what happens during a move?

The current one for 2010 is : http://technet.microsoft.com/en-us/library/dd298174.aspx and note: Corrupted mailboxes If you encounter corrupted mailboxes, you can move the mailboxes to a different server or database. The corrupted messages won't be moved. You can also get a detailed history of move request with: http://technet.microsoft.com/en-us/library/bb124612.aspx

Thanks