Dňa 16. novembra 2022 17:45:19 UTC používateľ Heiko Schlittermann via mailop <[email protected]> napísal:
>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). Ignoring DKIM for now, the RFC 5321, sect 4.4 (numbered by me): 1. A message-originating SMTP system SHOULD NOT send a message that already contains a Return-path header field 2. SMTP servers performing a relay function MUST NOT inspect the message data, and especially not to the extent needed to determine if Return-path header fields are present 3. SMTP servers making final delivery MAY remove Return- path header fields before adding their own. My understanding of this is, that Return-path header **can** exist on transport if it was added on sending system (which is not strictly forbidden) or **by mistake** on any relay. But then it must not be removed (even nor inspected its presence) on transport, until it reach final delivery, where it can be replaced/removed. I can imagine situation, eg. when final delivery adds it and then user forward message without headers modification. And i believe, that this example can be reason of that "SHOULD NOT" (but not adding it). Now back to DKIM, IMO it have to not sign it (nor its non-existence) as it is expected to be added latter. As intermediate relays have to ignore it, they cannot affect DKIM by this. IMO, if any system signs it, it does it wrong. regards -- Slavko https://www.slavino.sk/ _______________________________________________ mailop mailing list [email protected] https://list.mailop.org/listinfo/mailop
