list-id header SHOULD be on pretty much any UserMessage

According to RFC 2919 the List-Id header SHOULD be present on any mail which is reasonably perceived as related to a given list.

I recently upgraded from mailman 2 to mailman 3 and my users are upset that they no longer have a List-Id header present in posting acknowledgement messages.

Is it reasonable for me to call rfc_2369.process() on the usermsg generated in acknowledge.py with the incoming mlist and msgdata?