Quote:
Originally Posted by hadaso
Actually the report about failure of delivery is sent to the address in the Return-path header, which is normally the same as the address in the From header, but not always. AFAIK an SMTP server adds the Return-path header and puts there the "envelope from" address (the one reported by the sender in the SMTP "From" command).
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Yes, of course you are correct. The delivery SMTP server (where the message is filed into the addressee mailbox) adds a Return-path header copied from the envelope FROM address. So it's not the header From address, but the envelope FROM which sets the error message destination target.
You can read all about this in section 4.4 (Trace Information) of RFC 5321 at:
https://datatracker.ietf.org/doc/htm...21#section-4.4
When auto forwarding, the system doing the forwarding (Yahoo in the example by the original poster in this thread) adds a Return-path header at the top, then uses that Return-path address as the new envelope FROM during the forwarding SMTP session. The new final forwarded destination server then uses the envelope FROM (which is the same as the Return-path header at the previous step, so comes from the original message originating system) to generate the error message.
This is all far too arcane for regular email users! The bottom line is that in nearly all cases, the From address used when you create an original email message is where any delivery error messages are sent.
Bill