Confusing UAs considered harmful (was *Reply-to* considered harmful)

On Mon June 6 2005 14:58, Keith Moore wrote:

> 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.

That's emphatically NOT the assumption behind the Reply-To field semantics.
"suggestion" != "change the behavior"

It appears to be the assumption behind "Mail-Followup-To", but then that's
not an official message header field and is implemented differently by
the few UAs that pay any attention to it.

Some UAs may in fact change behavior; blame the UAs and/or their authors
if you wish, don't blame the field.  Maybe blame RFC 724/822 authors for
the "If there is" sentences (absent from RFCs 733/2822).

[more complaints about particular types of UAs elided]

> 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.

Agreed.  Maybe UAs, when instructed to respond, should start with "Where
do you want your message to go today?" :-)

> To the [extent?] new fields can help 
> this process, they can only do so by providing more information to a recipient
> to inform that choice.

Maybe.  Sometimes too much information can make matters worse.  Ultimately
a respondent needs to give some thought to the matter, and neither a UA
nor a new header field is a substitute for thought.