This topic describes how to add function to a preexisting mediation handler to operate on the message header.
There are different types of field that you can set in message headers. Importantly, you can set the forward and return routing addresses for messages after they have been mediated at the current destination. In addition there are other fields that you can set, like priority and reliability gor the message and its reply, and the remaining time before the message (or the reply) expires.