public interface MessageSender
A minimal message server only needs to implement the MessageSender interface. Keeping the server API simple makes it easier for implementations to start up message servers.
The MessageSender service is queue or topic specific. So there's no need for a To header if there's no routing involved. In other words, the service URL generally includes the queue or topic identifier, e.g.
More complicated messaging topologies, including configurations with routing mesaging servers, will use the headers to define the final destination. The headers have the same functional purpose as RFC-822 mail headers.