Meng,
MWW> I believe that the solution domain of designated sender schemes matches
MWW> the problem domain of RFC2821 MAIL FROM authentication, and that the
MWW> solution domain of crytographic signatures matches the problem domain of
MWW> RFC2822 header From: authentication.
The mail system use for RFC2821 Mail From has always been for bounces.
As I've been noting, this address can and does legitimately differ from
the standard array of RFC2822 addresses.
Using Mail From to authenticate a role involved with authorship or
posting (initial sending) will break those legitimate uses and will
remove an important capability from Internet mail.
d/
--
Dave Crocker <dcrocker-at-brandenburg-dot-com>
Brandenburg InternetWorking <www.brandenburg.com>
Sunnyvale, CA USA <tel:+1.408.246.8253>