With most Exchange Organizations, we may be leveraging various types of resource mailboxes or Public folders. When you start migrating users to Office 365, your Office 365 users will lose access to these delegated resources. If the resource is a conference room, the user will still be able to book time on that conference room and view the existing schedules; however, that's the extent of management for those resource objects. Public folders are completely inaccessible from an Office 365 mailbox.
While you migrate on-premise mailboxes, you may need to consider moving these resources with the users moving to Office 365. Let's cover these various resources and how you need to prepare for their moves to Office 365. The resources we will cover are:
Shared mailboxes
Conference rooms
Public folders