Custom headers can be added using the 'Manage Transport Properties' assertion. In this example we have put in the Name as "pmf" and Value as "TOMBRADY"
The most common reasons the headers would not be returned are:
1) The wrong target message has been chosen. Ensure the assertion is using the target as the response object.
2) The 'send immediately' check box is selected in the requested template response
assertion. When this is selected the response headers will be ignored. You will need to remove the check box to add the custom headers