The OneStopFactory function is implemented as the DLL entry point for creating custom transports. It is called by Messaging to create an instance of a custom transport and get the IMailSyncHandler interface for the transport. The ONESTOPFACTORYFUNC type defines a pointer to this function. OneStopFactory is a placeholder for the application-defined function name.
This function returns the standard values E_INVALIDARG, E_OUTOFMEMORY, E_UNEXPECTED, and E_FAIL, as well as the following:
The transport correctly initialized, and the function successfully returned a reference to the IMailSyncHandler interface.