The class represents a generic item in the Exchange store.
Assembly: EWS (in EWS.dll)
MessageType objects represent e-mail messages and all other items that are not strongly typed by the Exchange Web Services (EWS) schema. Items such as IPM.Sharing and IPM.InfoPath are returned as MessageType objects. Versions of Exchange starting with Exchange Server 2010 and Exchange Online do not return the base object in responses.