There are also to help BPOS users shift to Office 365, but Microsoft is not allowing all BPOS customers to upgrade immediately. Instead, the transition will happen in phases. On-premises also won't be able to connect to Office 365 at launch.

"Transition to Office 365 will be available to existing BPOS customers soon after availability of Office 365," Microsoft says in an FAQ. "Microsoft will work with all existing BPOS customers to determine the best time for the customer's business to make the transition."