Keith Moore writes:
as I understand it, ARPAnet mail grew out of a practice of sending
messages by using FTP to append to a file on the recipient's
computer. the entire message (both header and body) was created by
the author, there were no intermediaries that were aware enough of
the message content to be able to modify the header. SMTP came along
and added Received fields and Return-Path. whether the original
practice was "intention" or just the way it happened to work is not
something I can comment on, since I wasn't there at the time. but I
have heard complaints since at least the mid-1980s that there was too
little separation between envelope and transport in Internet mail ,
even though Received and Return-Path were the only layering
violations in the design.
Didn't address fields need to be modified by email gateways in the
eighties? I only got internet access in 1989, so this is hearsay, but
wasn't there separate worlds called, uh, csnet, decnet, janet and
arpanet? (I think those were the names I saw in my first sendmail.cf.)
Such address rewriting would be a major layering violation.
Arnt
PS:
for various reasons, the situation is much worse now than it was then.
Isn't it always ;)