DNS issue: Reverse MX A records (PTR) ERROR: No reverse DNS (PTR) entries

Symptoms

The https://intodns.com/ shows the following error for a domain:

PLESK_INFO: Reverse MX A records (PTR) ERROR: No reverse DNS (PTR) entries. The problem MX records are:
1.2.3.4.in-addr.arpa -> no reverse (PTR) detected
You should contact your ISP and ask him to add a PTR record for your ips

Or

The http://leafdns.com/ shows the following error for a domain:

PLESK_INFO: None of your MX record IP addresses have corresponding reverse DNS entries (PTR records). If these MX records are used to send outgoing mail this will cause them to trip anti spam filters. Many SMTP servers will not accept mail from an IP with no reverse DNS.

Or

Mail from the domain bounced by remote mail server with error:

PLESK_INFO: host mail.receiver.example.com[203.0.113.2] said: 550
inconsistent or no DNS PTR record for 203.0.113.3 (see RFC 1912 2.1) (in reply to RCPT TO command)

Cause

DNS misconfiguration.

Resolution

Contact your ISP and ask to add appropriate PTR record for IP. 

Note: it is required to wait for the DNS propagation period. It may take up 48 hours, but mostly faster.