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Our postfix setup uses recipient address verification. Obviously, postfix uses a special email address for this process, 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 [email protected] 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 [email protected], so it gets valid
  • set another valid email address/alias as double-bounce address

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

Richard Hansen
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Jürgen Gmach
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  • would it not be better being MAILER-DAEMON@domain? At least we already know what it is. – Rui F Ribeiro Dec 03 '16 at 15:41
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    You should leave `double-bounce` to the default. With `postfix`, setting it to a valid address would create transport loops. – Satō Katsura Dec 03 '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 03 '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? – Jürgen Gmach Dec 03 '16 at 18:48

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