To summarize:
DSN as of RFC 3461 is only recommended as internal status indicator for message relayed out of the own scope. End-to-end status is neither supported nor technical possible at the moment.
So with this DSN is useless for us, as we don't have a complex or unreliable internal network with many hops. If the first server accepted mail from the client and no bounce is coming back, the mail has left our scope for sure (thanks reliability of Postfix) and therefore notify the sender of the obvious is superfluous.
Many Thanks for sharing technical details Regards Andreas
smime.p7s
Description: S/MIME Cryptographic Signature
