Mobile devices are supported in a hybrid deployment. If %BRAND_EXCHANGE_ONLINE_SHORT% ActiveSync is already enabled on Client ...

Mobile devices are supported in a hybrid deployment. If %BRAND_EXCHANGE_ONLINE_SHORT% ActiveSync is already enabled on Client Access servers, they'll continue to redirect requests from mobile devices to mailboxes located on the on-premises Mailbox server. For mobile devices connecting to existing mailboxes that are moved from the on-premises organization to %BRAND_OFFICE_365_SHORT%, the %BRAND_EXCHANGE_ONLINE_SHORT% ActiveSync partnership must be disabled and re-established before redirection requests are processed correctly. Learn more at Clients and mobile in %BRAND_EXCHANGE_ONLINE_SHORT% Online.