What is PTR record?
A PTR (pointer) record maps an IP address to the domain name. It’s often called a "Reverse DNS Record" because it converts an IP address to a name. PTR records are mostly used as a security and anti-spam measure, to verify that a mail server address is allowed to send an email to a particular hostname. The reverse DNS entry checks if a server name is indeed associated with an IP address from where the connection was initiated.
Where PTR records is used for?