Why setting reverse DNS for your email?

Jun

Why setting reverse DNS for your email?

What is reverse DNS?

Well, it’s more logic to define first the DNS and then “reverse” the definition.

DNS: Domain Name System. It’s like an address book, when you enter a domain name or it’s easier to say a “link “over the internet, this domain name is sent to the DNS in order to find the matching IP address record for this domain name and help users to find a specific website or help computers to communicate when sending emails. So the role of DNS is to convert domain names into IPs.

Now it’s easier for you to define “Reverse DNS” which role is to convert the IPs into domain names. The Reverse DNS lookup to match the received IP address with a domain name for the intended link

 

 

 

Why setting reverse DNS for your email?

Setting reverse DNS means that you will have all of the domain names for all IPs you have, which means that it could work as spam filter by making sure that the IP used is really corresponding to this domain name and it’s not a fake one.

Let me explain this in a simpler way if someone is trying to send you an email from [email protected]. Before delivering this email to your email server, the reverse DNS could retrieve the IP address of the sender while he made his first handshake. Using this IP address and the sender domain name the rDNS could make sure of the sender identity in order to allow message delivery or deny it or mark it as spam.

How to configure the reverse DNS?

Configuring reverse DNS require to enter a PTR record over the DNS server.

What is PTR record?

It is a Pointer Record that resolves an IP address to a qualified domain name.

It consists of the IP address entered in a reverse way followed by “in-addr.arpa” where in-addr.arpa is where the PTR record is stored over DNS.

The one responsible to manage this PTR is the internet service provider (ISP) which is the entity that owns your IP address and some other IPs in your zone, so you should contact your ISP so they could delegate the reverse DNS for your IP zone.

If you are the one responsible then you should first create a reverse DNS zone by dropping the last digit of your IP address, reverse it and then follow it by “in-addr.arpa”

for example, if your IP address is: 197.133.44.128, then your DNS zone will be 44.133.197.in-addr.arpa.

after creating your zone file, now you can create your PTR record with it right format, for our example, it will be: 128.44.133.197.in-addr.arpa, et voilà you have created the Reverse DNS.