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List:       postfix-users
Subject:    Re: Change status code for "Host not found"
From:       Wietse Venema <wietse () porcupine ! org>
Date:       2019-09-16 13:55:55
Message-ID: 46X77H0Yj6zJrNt () spike ! porcupine ! org
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Helmut Schneider:
[ Charset ISO-8859-1 converted... ]
> Hi,
> 
> I'm running postfix as a relay connected via VPN. If the VPN is down
> mails are rejected:
> 
> relay=none, delay=0.09, delays=0.06/0.02/0.01/0, dsn=5.4.4,
> status=bounced (Host or domain name not found. Name service error for
> name=EXCHANGE01 type=AAAA: Host not found)

It's status=bounced (dsn=5.4.4) because Postfix received a DNS
NXDOMAIN (name does not exist) response for the name 'EXCHANGE01'.

> Is there a way to change the dsn to 4xx and deliver it when the VPN is
> up again?

http://www.postfix.org/postconf.5.html#default_delivery_status_filter
Look under the examples for smtp_delivery_status_filter. Here is
an untested variant that should work.

/etc/postfix/main.cf:
   smtp_delivery_status_filter = pcre:/etc/postfix/smtp_dsn_filter

/etc/postfix/smtp_dsn_filter:
    /^5(\.\d+\.\d+ Name service error for name=EXCHANGE01/ 4$1

You can't use http://www.postfix.org/postconf.5.html#smtp_dns_reply_filter
because that feature requires that the server returns a reply, not
NXDOMAIN.

	Wietse
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