Clients and service providers can update a property value by calling:
Use HrSetOneProp only if the target object is local; this function can cause performance degradation when used with remote objects.
The following procedure illustrates how to use SetProps to update the message class, or PR_MESSAGE_CLASS property, of a message.
SPropValue spvMsgClass;
spvMsgClass.ulPropTag = PR_MESSAGE_CLASS;
spvMsgClass.Value.lpszA = "IPM.NewClass";
hRes = lpMessage->SetProps(1, (LPSPropValue) &spvMsgClass, NULL);