MigrationPermanentException: Target user already has a primary mailbox in Office365 Exchange Online
In a Microsoft Office365 migration project, I faced the following error trying to migrate a mailbox from an on-premises Exchange 2013 database to Exchange Online: Error: MigrationPermanentException: Target user ’Doodle, Johnny’ already has a primary mailbox. –> Target user ’Doodle, Johnny’ already has a primary mailbox. I was sure I hadn’t migrated Johnny’s mailbox before. …