Barry Leiba writes:
Now write a spec for the "Sender" header field.
http://cr.yp.to/immhf/sender.html covers the 822 syntax and semantics,
the 2822 syntax and semantics, and what programs do in practice. But
people should not have to do this much work before reserving a name.
Some have capsized, and the Coast Guard is still unable to find any
survivors.
It would be interesting to understand how people managed to create the
current Sender situation.
RFC 822 4.4.2 makes Sender sound like the traditional secretary line in
memos. There are several examples of this later in the document. RFC 822
4.4.4 specifies Sender, defaulting to From, as the bounce target.
What was Crocker thinking? The envelope/message distinction was already
clear in SMTP. Why is Sender useful in a mail system that supports
envelope senders?
Pine and Eudora use Sender (or X-Sender or X-X-Sender) as a bogus
security mechanism, putting private login information into it and making
it difficult for novice users to change. What was Crispin thinking? What
were the Qualcomm people thinking?
The Pine people say that they use X-Sender/X-X-Sender because some
unidentified mailing-list programs look at Sender/X-Sender. If this is
true, what were the authors of those programs thinking?
---D. J. Bernstein, Associate Professor, Department of Mathematics,
Statistics, and Computer Science, University of Illinois at Chicago