Our postfix setup uses recipient address verification. Obviously, postfix uses for this process a special email address, defined right here.

$ /usr/sbin/postconf | grep double_bounce_sender
address_verify_sender = $double_bounce_sender
double_bounce_sender = double-bounce

Last week we got a problem with this setup, as our smtp asked the target smtp about the recipient address, the target smtp on the other hand, asked our smtp, whether double-bounce@mydomain.com is valid, which it neglected.

So, that email could not be delivered, although both the original sender and the recipient are valid email addresses.

Now, I have different options: - deactivate address verification - create an alias for double-bounce@mydomain.com, so it gets valid - set another valid email address/alias as double-bounce address

I can't forsee the outcome of these actions. Any thoughts?

  • would it not be better being MAILER-DAEMON@domain? At least we already know what it is. – Rui F Ribeiro Dec 3 '16 at 15:41
  • 1
    You should leave double-bounce to the default. With postfix, setting it to a valid address would create transport loops. – Satō Katsura Dec 3 '16 at 15:47
  • I agree, changing the default breaks internal workings and spam filters, spamassassin rules among others. It can also potentially land you in more blacklists. – Rui F Ribeiro Dec 3 '16 at 16:06
  • So, if I do not touch the double_bounce_sender, my only chance to get the process working would be to deactivate recipient verification. Is it possible to keep recipient address verification for our own domains, but deactivate for all others? And does reject_unverified_recipient only affect outgoing emails or also incoming? ie when I'd deactivate it, does postfix then also accept emails for addresses @mydomain which do not exist? – jugmac00 Dec 3 '16 at 18:48

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