Hi,
I *think* I fixed this. Moderate testing suggests it is fixed, but, you know, Murphy's law and all that.
As to this:
I note that the mail notifications I get claim that I can simply reply in order to discard the messages: that doesn't seem to work either.
the way this works is that the message you get when a new post is held has /as a mime part/ a message that, when you reply to /that one/, you get the desired behavior.
In my MUA (claws-mail) I can indeed select that mime part, hit reply, and have the correct reply address and confirmation code in the subject.
(Compare to the answers to this post: https://mail.python.org/pipermail/mailman-users/2011-July/071942.html)
I didn't know that either, btw :-)
If there are further problems, please let us know!
Regards, Mario