What happens if a mailbox migration/synchronization is restarted after it has been cancelled or has failed?
Exchange Migrator 1.x
Exchange Migrator 2.x
Exchange Migrator (EM) stamps a Last Migration Time when migrating and synchronizing mailboxes. Therefore, if you restart a failed synch, EM will attempt to synchronize messages from the beginning. However, since the Last Migration Time on the successful mailboxes is later than the time stamp on the mailbox messages, those mailbox messages will not be synched. When EM encounters the first mailbox where the Last Migration Time is not later than the time stamp on the email messages, it will then begin actively synching again at those messages.