The property gets or sets an enumeration value that describes how a message item is handled after it is updated. This property is required for message items, including meeting messages such as meeting cancellations, meeting requests, and meeting responses. This is a read/write property.
Assembly: EWS (in EWS.dll)
You must set the MessageDispositionSpecified property to true so that the property is serialized into the Simple Object Access Protocol (SOAP) request.