[Mailman-Users] Challenge/response

[Bob Morse]

I have a client who is concerned about his list subscriber addresses being
spoofed. In other words someone who knows the addresses of people on the
list can set up a mail server and spoof the subscriber so he can post nasty
things to the list. He would like to set up a challenge/response mechanism
so that when xyz at domain.com posts to the list, xyz at domain.com gets sent a
copy of the message and must confirm that he/she was the sender before it
gets posted. I don¹t see any configuration in Mailman for this. Is it
possible?

BTW, searching the archives at mail-arcihve.com gets a 404 error.