Welcome @6hil Happy you are here
rDNS ptr record is only set for the VPS i.e. the record identified the ip address against the hsotname. e.g. 123.456.789 server with primary domain genghiskhan.com would have its hostname as mail.example.com and therefore its rDNS ptr record for both ipv4 and ipv6 ip addresses as mail.example.com
Note: if the server does not have a rDNS record, it cannot resolve a reverse lookup.
Contact your server provider for directions on how to set rDNS for your server. They must have a proper documentation for this.