*Reply-to* considered harmful (was Re: Understanding response protocols)

> No! Reply-To is what you should use if you want to send a personal reply
> to the author of, the original message (which indeed you sometimes need to
> do if, for example, your reply is too complex/personal/whatever for
> sending to thje complete list).

That is completely incorrect.

"From" contains the author (or authors) of the original message.  If you 
want your reply to go to the author(s) of the original message, you need 
to send your message to the addresses in the From field.  As at least
one example in RFC 822 makes clear, it is not reasonable to assume that
sending to addresses in the Reply-To field will reach the author(s) of 
the original message.

> Therefore, it is evident that some further Reply-to-like header (MFT, MCT
> or something new) is needed for use with the "Reply-to-List" command (or
> Reply-to-All if Reply-to-list is not provided).

No, it doesn't follow - both because your premise is incorrect, and because
the absence of a field specifically intended for group replies is not an indicator
that some additional field is needed.  

Rather, the whole assumption that the author of a message should be able to
change the behavior of a recipient's user agent is very much in doubt.  Even
in the case of a single recipient message the behavior of Reply in the presence
of a Reply-To field is too often surprising for the responder.   It only becomes 
more surprising in the presence of additional recipients, reply to author /
reply to all choices, mailing lists, and/or multiple fields indicating how to reply -
_no matter how those new fields are defined_.

The only way to make Reply work better is to improve the user interfaces
of mail user agents so that recipients of messages are more easily able to 
explicitly choose where their replies go.   To the next new fields can help
this process, they can only do so by providing more information to a recipient
to inform that choice.

Keith