Michael Peddemors via mailop <[email protected]> (Mi 16 Nov 2022 16:55:58 CET): > > How can you tell that is was the sender who *forgot* to remove it? > > Maybe it was the recipient (or an intermediate system) who inserted it > > at the wrong place? > > > > It is just not the right place, it should be set at the beginning > > of the mail data, from the server doing the "final delivery" (RFC5321). > > That is the point.. if it isn't the final delivery, eg a mail server sees it > already set, then the server previous set it incorrectly, since it is still > in transit.
The server that set the header has probably no indication that its
delivery isn't the final one. (Or, is poorly configured, of course.)
I'm not sure one if the next hops should remove headers of previous
hops, IMHO this could be a bad move (w/ e.g. respect to DKIM
signatures, though I think, the Return-Path header isn't part of the
default set of signed headers).
IMHO each server, that feels its delivery is the final one, can set the
Return-Path header on top of the previous ones. (Which will again break DKIM,
in case the Return-Path header is part of the signed header set.)
So, still, I do not see any failure, it just doesn't feel perfect.
But we do not even know which server set this header. We can just
guess, that the one setting it, did so by prepending it. But any other
(broken) hop is able to set the header just somewhere in between the
other headers.
I can imagine forwarding, which keeps the complete header set intact.
Best regards from Dresden/Germany
Viele Grüße aus Dresden
Heiko Schlittermann
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