From:, Mail, and sendmail

[roots at cbhydra.uucp]

This all assumes that the right thing to do is for each hop to update
the From: line from, say
	From: daemon!root
to
	From: tektronix!daemon!root
if your machine is called "tektronix".  However, nothing in RFC822
says this change is supposed to be made.  In fact, both of these
lines are illegal 822 because there is no @ in them.  If we were
conforming properly to 822, what we would do is
	From: root at daemon.tektronix.UUCP
to
	From: root at daemon.tektronix.UUCP
If it's done right, there's no need to change.  Furthermore, if I
send out a message with a from line like this and somebody turns it into
	From: tektronix!root at daemon.tektronix.UUCP
I'm going to get very upset - this is a blatent violation of 822 and
also breaks the message.

I don't understand why sendmail makes this change anyway.  The previous
system was that the From<space> line had the ! path and the From: line,
if any, was a legal RFC822 line.  Lines like
	From: tektronix!daemon!root
are not legal 822 lines.

Please do not take the above as picking on tektronix, I'm just grabbing
an example out of thin air.  It can probably be argued that tektronix
is one of the few machines on the UUCP net that conforms to RFC822 in
this respect.