On Monday, September 13, 2004 at 1:47:32 AM. William Leibzon quotes RFC
2822 and argues that SenderID's use of Resent-From is inconsistent with
RFC 2822. I disagree.
RFC 2822 specifies Resent-From is not for "forwarding", in either of the
following two senses:
1. Quoting from RFC 2822:
One sense of forwarding is that a mail reading program
can be told by a user to forward a copy of a message to
another person, making the forwarded message the body
of the new message. A forwarded message in this sense
does not appear to have come from the original sender,
but is an entirely new message from the forwarder of the
message.
This sense of "forwarding" is normally activated by a user
pressing a "Forward" button in a UI (or similar action.) I
completely agree that "Resent-From" has no place in this sense
of forwarding.
2. Quoting from RFC 2822 again:
On the other hand, forwarding is also used to mean when
a mail transport program gets a message and forwards it
on to a different destination for final delivery.
I believe that what RFC 2822 refers to here as "forwarding" is
what we today more commonly refer to as "relaying". That is,
when an MTA merely accepts a message destined for a particular
mailbox, and sends the message along to another MTA because
the first MTA doesn't own the mailbox.
The position that this sense of "forwarding" really means
"relaying" is bolstered by the fact that RFC 2822 nowhere
contains the words "relay" or "relaying".
I completely agree with RFC 2822 that "Resent-From" has no place
in this sense of forwarding.
So, what's Resent-From for? It's for when a message arrives at the
destination mailbox, and the owner of that mailbox gives instructions,
either manually or automatically, that the message should instead or
additionally be delivered to a different mailbox. A Unix ".forward"
file is the canonical example of such automated instruction.
It would probably be a good idea for Pete Resnick (editor of RFC 2822)
to chime in on this interpretation.
-- Jim Lyon
Internet commerce will never really take off until you can buy something
online without getting spammed by the vendor.