The problem is that the responding UA can't obey both the originator's
recommendation and the responding user's instructions.
Huh? I'm talking about convenient _default_ recipient lists. The user is
of course free to send mail wherever he wants.
I expect MUAs to expand the `reply' function to mean `send to (Reply-To
OR From) + Reply-Cc'.
[ ... ]
I further expect MUAs to expand `reply-using-destination-fields' to mean
`send to (Reply-To OR From) + Reply-Cc + To + Cc'.
Okay, now I understand what you mean.
Your proposal does not solve the fundamental problem: the reply-to-all
addresses always include the reply-to-author addresses.
Think about the usual case of a subscriber sending a message to a
mailing list. He typically wants reply-to-all to go to the mailing list
alone, while reply-to-author goes to him alone. This is impossible if
the reply-to-author address is included in reply-to-all.
Let your users manage their own mailing lists. http://pobox.com/~djb/qmail.html