I've sent twelve messages to the namedroppers mailing list this month.
Five of them have been silently discarded by the namedroppers censor,
Randy Bush. (See http://cr.yp.to/djbdns/namedroppers.html for previous
in my experience, if you send mail to the list administrator
and say "please add user(_at_)example(_dot_)com as an address that is allowed
to post to this list", the problem goes away - for that list.
and no, I don't think that one should have to "say the secret magic words"
to make the right thing happen. but it does seem to work in practice.