The EWS Managed API 2.1 package contains the EWS Managed API, a managed interface for developing client applications that use EWS. The EWS Managed API simplifies the implementation of applications that communicate with versions of Exchange starting with Exchange Server 2007 Service Pack 1 (SP1). Built on the EWS SOAP protocol and Autodiscover, the EWS Managed API provides a .NET interface to EWS that is easy to learn, use, and maintain.
For your convenience, the package also includes the Exchange Server 2013 token validation library. You can use the EWS Managed API and the library to build mail apps for Outlook that can be authenticated by the identity tokens issued by Exchange 2013.