Microsoft Exchange ActiveSync (commonly known as EAS) is a communications protocol designed for the synchronization of email, contacts, calendar, tasks, and notes from a messaging server to a smartphone or other mobile devices. The protocol also provides mobile device management and policy controls.AS 2.0 shipped in Exchange Server 2003. This version of the protocol was developed by the Microsoft Windows Mobile team and was delivered as a binary drop (massync.dll) to the Exchange Server team.