Bounce email message received: your rDNS doesn't match with domain sending mail

Symptoms

• Bounce email message is received with following information:

  CONFIG_TEXT: your rDNS doesn't match with domain sending mail
  You IP address 203.0.113.2 is associated to domain mail.example.com.
  Howerver, your email has been sent from example.org.
  Maybe you might want to change DNS (PTR type) and your server hostname to same value.
  Here values used to make this test:
  IP: 203.0.113.2
  HELO: example.org
  rDNS: mail.example.com

• SMTP HELO greeting contains the Plesk hostname, which is configured in Tools & Settings > Server Settings > Full hostname:

  CONFIG_TEXT: example.org

• Sender domain example.com is hosted in Plesk and resolves to following IP address:

  # dig @8.8.8.8 example.com +short
  203.0.113.2

• PTR record for example.com IP resolves to mail.example.com:

  # dig @8.8.8.8 -x 203.0.113.2 +short
  mail.example.com.

• Tools & Settings > Mail Server Settings > Outgoing mail mode is set to Send from domain IP addresses

Cause

Plesk is configured to use Plesk hostname for SMTP greeting, therefore rDNS lookup on sender IP doesn't match because it resolves to a different domain.

Resolution

Warning: Selecting this option may result in mail sent from some or all domains being marked as spam if the destination mail server uses cbl and more than one domain on the Plesk server uses the same IP address.

1. Login into Plesk
2. Go to Tools & Settings > Mail Server Settings
3. Set Outgoing mail mode option to Send from domain IP addresses and use domain names in SMTP greeting and click OK to apply changes.