Using Exchange ActiveSync for Exchange client development. Exchange ActiveSync works well for mobile device sync of email, calendar, contacts, tasks, and notes. You can also use Exchange ActiveSync for some client integration with Exchange; however, it is not designed to be used for server-to-server communications.he Exchange ActiveSync protocol is designed for direct mobile device sync with Exchange, including lightweight clients, such as the Windows 8 Mail and Calendar application, that can be used in mobile scenarios.