From: "Gary Feldman" <gaf(_at_)rtr(_dot_)com>
...
There is a difference between the From_ header and the From: header.
As suggested in my previous email, I find the use of the term "From_
header" confusing. I have a very simple view of the world: headers are
defined in RFC 2822 and related RFCs, and refers to the stuff at the
top of the message data (as message data is defined in 2821). Commands
are
defined in RFC 2821 and related RFCs. The use of "header" to describe
stuff sent in the message envelope triggers my "imprecise language"
alarm.
Such alarms are valuable because imprecise language often indicates
imprecise or simply wrong thinking.
I also have no idea where the underscore originates. Or perhaps are you
talking about something entirely separate from these two RFC sets?
...
I can't say what the other person meant, but:
- "_" has historically been used to indicate a single ASCII blank.
- "From_" tends to refer to the non-RFC 822 header historically and
optionally added to the start of messages by various mail systems.
This header tends (or tended) to contain the RFC 821 sender or
SMTP Mail_From value and the data. When UUCP is used, it tends to
contain the UUCP path, except when rmail has been hacked to recognize
when the last host is an FQDN and use that instead.
I think the sendmail "Ops" document calls this the "UNIX From" header.
Look for options controlling it in the "mailer" rules or control
lines in sendmail.cf.
Vernon Schryver vjs(_at_)rhyolite(_dot_)com
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