Even outside the list world, there are scenarios where sending to the
reverse-path is inappropriate. EG, when the Sender/From construct is
actually used, the notification is returned to the Sender instead of
the From parties.
That's a bug in RFC 822. Nondelivery reports should always go to the
Return-path/MAIL FROM address, NEVER to the Sender address. The
contents of the Sender field aren't even required to be a legal address.
The reverse-path is almost always the same mailbox address as the message
sender (as specified in Sender, when it is actually present). In that
regard, the reverse-path will point to the Sender rather than From.
correct. but you get this address from the Return-Path field, not the
Sender field.
These examples are all really beside the ultimate point, however:
out-of-office notifications are an application of the messaging network
and not in-band management messages, so they really should use the
headers rather than the envelope.
That's precisely the reason that the MAIL FROM address is exposed in the
message header as return-path - so the address can be used for automatic
responses that are generated after the message leaves the
transport/delivery system.
We're not disagreeing here. Management messages should use the envelope,
and the reverse-path is provided to the application through Return-Path
header field. Meanwhile, application messages (replies, content filters,
and yes out-of-office notifications) should use the application headers,
(ala From/Reply-To).
no, "management" vs. "application" messages is not where the line should
be drawn. Return-Path is provided so that applications can use it when
it's appropriate. Most automatic responses should go to Return-Path.
Keith