rDNS is configured on a zone file. This zone file teaches our name servers to resolve a host from an IP address. The file will be called 10.10.10.10.db, where 10.10.10.10 is our server IP address. Also, save this zone file in path /var/named.

One of the foremost importances of reverse DNS or rDNS is spam filtering. A server that sends emails needs to have rDNS configured for it’s emails to be received by almost all other servers. If not, the emails will be treated as Spam and hence blocked or dumped to Spam.

The content of the file is as follows:

;
; BIND reverse data file for 0.10.10.in-addr.arpa
;
$TTL    604800
0.10.10.in-addr.arpa.      IN      SOA     ns1.example.com. 
admin.example.com. (
                          1         ; Serial
                          3h       ; Refresh after 3 hours
                          1h       ; Retry after 1 hour
                          1w       ; Expire after 1 week
                          1h )     ; Negative caching TTL of 1 day
;
0.10.10.in-addr.arpa.       IN      NS      ns1.example.com.
0.10.10.in-addr.arpa.       IN      NS      ns2.example.com.
10.10.10.10.in-addr.arpa.   IN      PTR     example.com.

NOTE: Make sure to replace 10.10.10.10 with your server IP and example.com, with your domain name.