4.2.7. The To Field

You can specify a value for the message header's To field when you are about to send the message. This field should contain the address of the message recipient.
When using the ServiceInvoker, because it has already contacted the registry at construction time, the To field is unnecessary. In fact, when sending a Message through ServiceInvoker, the To field will be ignored in both the synchronous and asynchronous delivery modes.