The fact that mailing lists are a difficult problem is a matter of bad
choices throughout the history of e-mail. In the beginning, one couldn't
guess, but once it became clear, we should have put mailing-list-specific
fields in to solve the problem. We didn't. A pity.
well, we did put them in eventually. it just took awhile.
even now I'm not sure that list-specific fields solve those problems,
but I do like list-specific fields better than having lists rewrite
originator-supplied fields.
The problem is that all of this isn't clear, and that some of it
depends upon a human thinking about what the reply is and to whom it
should really be sent. And many/most humans can't be bothered, with
the result that replies often wind up going to *everyone* the MUA will
allow them to be sent to.
interesting that in the days of paper memos, people could be bothered
to think about such things.
part of the problem is probably (as you said) that the subtle
differences between return-path, from, reply-to, and sender
aren't clear to most email users - and there is a lot of
misunderstanding out there. (and if the protocol developers can't
agree on when to use each field, how can we expect users supposed to
behave uniformly?) still, if the protocol folks can come to agreement
there is some potential that improved user interfaces might help
this problem.
another part of the problem is probably that email has made it so
easy to send messages that we now have to deal with too many messages -
which is a clue as to why people "can't be bothered" to think about
where to send replies anymore. offhand, I don't see how to fix this one.
Keith