[Mailman-Users] Enable moderated list to always accept some emails?

[Matt England]

I want to enable a moderated list (that moderates emails from non 
subscribers) to always accept email that comes with a certain header 
attached (in this case, a header appended by http://mail2forum.com/ 
software) even if the sender's address is not subscribed to the email list.

Does GNUMailman some means to do this?

My apologies if this is a FAQ.

-Matt