On 1/20/2009 6:10 AM, Steffen Kaiser wrote:
Again... the only unit responsible for sending actual bounce messages is the SENDERS MTA. Your (receiving) MTA should only either ACCEPT (if so, NEVER generate a 'bounce' later), DEFER or REJECT.
That's wrong. To "accept" means to take over the responsibility to deliver the mail and/or notify the sender about its forthcoming. A failed delivery is just a DSN as read or delivered DSNs are.
Correct - this is what I said. Reject is a failed delivery, while a defer will be retried until max retires is reached.
either to deliver or to report failure. Once SMTP dialogue is over, "to report failure" means sent a DSN aka bounce message.
A DSN is NOT a bounce message - it is an smtp transaction. The actual BOUNCE message is GENERATED by the ORIGINATING server.
'Bounces' from servers other than the originating server (the server that the original sender used to send the message) are called BACKSCATTER.
RFC2821 sec 2.4 in context of garbled message content
"Delivery SMTP systems MAY reject ("bounce") such messages rather than deliver them." The MTA may decide to not deliver, but bounce in that case.
The word 'bounce' is NOT the primary word used - reject is. The word 'bounce' (in parenthesis), in my opinion, shouldn't be included here, as it is responsible for the confusion surrounding the difference between smtp transaction responses (ie reject or defer) and an actual EMAIL BONCE message, that many people confuse with it.
permanent failure => appropriate notification of sender
Correct... but the only responsibility of the receiving server is to reject the message appropriately. It is the responsibility of the originating (sending) server to inform the SENDER with the NDR/Bounce email.
Because no MTA I'm aware of delivers during SMTP DATA phase, permanently failed delivery attempts have to generate a bounce message per RFC.
But that is my point. The DESTINATION server does NOT generate THE BOUNCE - it only rejects the message with the appropriate smtp reject code. The ORIGINATING (SENDING) server generates the actual BOUNCE message (the email the sender gets informing them of the failed delivery).
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Best regards,
Charles