After setting up Exchange Online (Office 365) with Exchange 2010 SP3 Hybrid, my migrated remote mailboxes will not receive external email. They can receive email from other Online, cloud users. All the mailboxes created in Office 365 can receive external email. In doing a mail trace, -EventID 'DSN' the Source shows 'Routing'. I eventually get 'Delivery is Delayed' message. Any thoughts?