The IP address sending this message does not have a PTR record setup

ERROR : The IP address sending this message does not have a\n550-5.7.1 PTR record setup. As a policy, Gmail does not accept messages from\n550-5.7.1 IPs with missing PTR records.”
 
How to Fix the above error ?

The above error shows that your server IP doesn’t have a PTR record setup. Contact your hosting provider or datacenter and ask them to set the PTR record (reverse DNS) for your IP address.

After setting the rDNS it might take few hours for changes to update globally. You can contact the hosting company or datacenter to know about propagation delay after setting the rDNS.

For sending emails to hotmail, gmail etc rDNS is compulsory. Most of the internet service providers will block the email if PTR record is not set correctly for your domain.

Please try sending email to gmail.com after few hours and check whether you are still getting any errors

Refer the below link for more details :

https://support.google.com/mail/answer/81126#authentication

How to check whether rDNS is set correctly

Command to check rNDS : host IPADDRESS

IPADDRESS in the above command should be replaced with your server IP address.

An Example is given below :

host server.example.com
server.example.com has address 192.168.1.5

host 192.168.1.5
5.1.168.192.in-addr.arpa domain name pointer server.example.com.

PTR record resolve IP address to a server hostname. rDNS is set correctly for the above IP address.