4.4.4. AUTOMATIC USE OF FROM / SENDER / REPLY-TO
For systems which automatically generate address lists for replies to messages, the following recommendations are made:
This relates to automates like autoresponders (vacation mail etc) that process the mail at it's destination. The envelope sender may not available there. All MTA's (qmail, postfix, exim, sendmail, smail, ...) that transport the mail (MTA = mail transport agent) nearer to it's final destination bounce undeliverable messages to the envelope sender.
So according to the spec I should use "Sender: <dtml-var OurBounceProcessingAccount>" in our DTML-Method that uses dtml-sendmail, no?
To handle autoresponders etc. that's ok. It doesn't handle delivery failures. You HAVE TO set the envelope sender accordingly (I think for Postfix it's the -f switch like for sendmail). To do that you have to generate a new method - possibly as external Python method.
envelope-sender ... Is the envelope-sender then the user that is passed to postfix when doing the SMTP connection and giving the mail from: command? Exactly that is the envelope sender.
Maybe my mistake is in the term "envelope-sender"? Maybe you confuse heders and envelope in general (don't worry, that's common). To understand it simply think about traditional letters: If you put a letter that has to be sent from 'A' to 'B' in an envelope that states a sender 'X' and a receiver 'Y' the delivery service will also return it to 'Y' regardless what the "headers" on the letter say. The only criterium is the envelope. If 'Y' is not reachable the letter will return to 'X', not to 'A'.
Regards, Frank