What is reverse DNS lookup?
Reverse DNS lookup is used when you want to resolve an IP address to a host name. This is the opposite of normal DNS look up, which is also called forward DNS lookup.
Example:
Forward DNS lookup:
Smtp1.mail.example.net resolves to 80.80.20.42
Reverse DNS lookup:
80.80.20.42 resolves to Smtp1.mail.example.net
Why is reverse DNS lookup important?
Some mail servers will, when you send e-mails to them, look up your mail servers’ IP address to see if it can look up a valid hostname from the IP address. If it cannot look up and resolve your mail servers' IP to a valid host name it might refuse to receive e-mails from your mail server.
Please contact your Internet provider for reverse zone updates