Plesk Email Security displays RDNS as not configured

Symptoms

• Plesk Email Security displays RDNS config in red:
  

• PTR record is properly configured and resolves to server hostname:

  # host 203.0.113.2
  2.113.0.203.in-addr.arpa domain name pointer plesk.example.com

  # host plesk.example.com
  plesk.example.com has address 203.0.113.2

• When running the command below, wrong public IP or localhost address is displayed:

  # plesk php -r “var_dump(gethostbynamel(‘<server_hostname>’));”
  array(2) {
  [0]=>
  string(9) “127.0.0.1”
  [1]=>
  string(13) “203.0.114.3”
  }

Cause

Plesk Email Security is checking RDNS for the server at the wrong IP address. One or several IP addresses have been added manually in /etc/hosts for plesk.example.com:

# grep plesk.example.com /etc/hosts
127.0.0.1 plesk.example.com
203.0.114.3 plesk.example.com

Resolution

1. Connect to the server via SSH.

2. Open /etc/hosts file in any text editor and comment lines with the server hostname and wrong public IP address:

   #127.0.0.1 plesk.example.com
   #203.0.114.3 plesk.example.com