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Twissell
Asked: 2018-05-12 07:07:53 +0800 CST

Postfix: forced reverse lookup for incoming connections

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I see following maillog records when new mail comes to server

connect from unknown [209.85.223.195]
client=unknown[209.85.223.195]

But that IP address is GMail IP and it has valid PTR-record which points to mail-io0-f195.google.com My main.cf is here

resolv.conf content for Postfix listed below

# Generated by NetworkManager
  nameserver 8.8.8.8
  nameserver 8.8.4.4
  nameserver [hosting_dns_servers_here]
 # NOTE: the libc resolver may not support more than 3 nameservers.
 # The nameservers listed below may not be recognized.
   nameserver 1.1.1.1
   nameserver 1.0.0.1
   nameserver 77.88.8.8
   nameserver 77.88.8.1

So, how can I force Postfix to make reverse lookup and logs a domain name of mailserver not IP address? I'm running CentOS 7.4

P.S. Postix "chained" in chroot

postfix

2 Answers

  1. Try changing smtp_host_lookup to dns instead of your current dns,native. I'd like to refer you to the manual for further information.

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  2. Best Answer

    The issue was caused by Postfix in chroot mode. Almost the same problem was described earlier for Ubuntu.

    You need to copy libraries needed for reverse lookup name resolution inside the chroot, e.g.

    sudo cp -vl /usr/lib64/libnss_* /var/spool/postfix/lib64
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