On Sun January 30 2005 01:47, Frank Ellermann wrote:
that happens not to match the intended original use (prior
to DSNs) for delivery trouble notifications.
IBTD. The original use of a "Return-Path" was a reverse path,
the same path backwards.
Even if one goes back to the original SMTP specification,
RFC 788, the purpose is "to return non-delivery notices".
For a direct message from an individual to a set of
recipients, sending such notices to the originating
individual makes sense. But for cases such as a message
sent via a mailing list expander (introduced in RFC 822),
the non-delivery notices would simply be annoying if sent
to the message author, and can only be usefully acted upon
if sent to the mailing list maintainer.
So for early SMTP documents, which didn't consider mailing
lists as we now know them (those documents discuss expansion
of lists by assuming that the originator would issue EXPN
commands, collect the responses, then issue corresponding
multiple RCPT TO commands in a subsequent session), the
originator would appear in the return path. But that has
turned out to be impractical (due to list maintenance
issues as well as the fact that many sites have chosen to
violate RFC 821 by disabling the EXPN command (subsequently
doing so was sanctioned by RFC 1123)).