Unable to send an email from Plesk server: SMTP service 554 invalid DNS PTR resource record

Symptoms

• Unable to send an email from a Plesk server, the delivery fails with one of the following error messages:

  554-example.com (hostname) ESMTP Service not available
  554-No SMTP service
  554 invalid DNS PTR resource record, IP=203.0.113.2

  554-Bad DNS PTR resource record.

  21 Temporarily rejected. Reverse DNS for this IP failed. IB108 The IP address attempting to send mail does not have reverse DNS setup, or the DNS lookup failed. Verify the sending IP address has reverse DNS setup before resending the email.

  550-5.7.1 [203.0.113.2] The IP address sending this message does not have a PTR

  (host example.info[203.0.113.111] refused to talk to me: Service not available - no PTR record for 203.0.113.2)

  550 No rDNS entry for

  status=bounced (host gmail-smtp-in.l.google.com[2a00:1450:400c:c0b::1b] said: 550-5.7.1 [2001:db8:f61:a1ff:0:0:0:80] Our system has detected that this message does 550-5.7.1 not meet IPv6 sending guidelines regarding PTR records and 550-5.7.1 authentication. Please review 550-5.7.1 https://support.google.com/mail/?p=IPv6AuthError for more information

  X-Host-Lookup-Failed: Reverse DNS lookup failed for 203.0.113.2

• There is no DNS PTR record for the sender's IP address:

  # dig @8.8.8.8 +short example.com
  203.0.113.2
  # dig -x 203.0.113.2 +short
  (Empty output or it resolves to a domain that doesn't resolve to the sender's IP address)

  Note: Where example.com is a domain hosted on a Plesk server and 203.0.113.2 is the Plesk IP address assigned to the domain in Plesk

Cause

The mail message is rejected due to security policy on the recipient side.

Resolution

Note: DNS propagation usually takes 24-48 hours.

• Contact the IP address provider or the Internet Service Provider (ISP) in order to add an appropriate PTR record to the IP addresses configured on the Plesk server.
• In case of Plesk is installed on a Cloud Server, check the article: How to add PTR record to Cloud Server with installed Plesk?
  

Additional information

How to specify the hostname used by MailEnable for sending outbound mail

How to change Postfix SMTP banner?