Microsoft has announced that the AdditionalStorageProvidersAvailable setting in OWA mailbox policies will now control access to both first-party and third-party storage providers. The new setting is now available and becomes active in August. Before then, you might want to adjust some of your OWA mailbox policies.
The new version of OWA (sometimes called Outlook on the Web, or Outlook Web Access) is now generally available to all Office 365 tenants. Although the new OWA has some nice features, you might want to turn off the user choice (toggle) to move the new UI until you’ve had time to prepare the help desk, documentation, and that sort of thing.