Reverse DNS

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What Does Reverse DNS Mean?

Reverse DNS (rDNS or RDNS) is a Domain Name Service (DNS) lookup of a domain name from an IP address. A regular DNS request would resolve an IP address given a domain name; hence the name “reverse.”

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Reverse DNS is also known as Reverse DNS Lookup and Inverse DNS.

Techopedia Explains Reverse DNS

Reverse DNS requests are often used for filtering spam. Spammers can easily set the sending email address using any domain name they want, including legitimate domain names like those of banks or trusted organizations.

Receiving email servers can validate incoming messages by checking the sending IP address with a Reverse DNS request. If the email is legitimate, the rDNS resolver should match the domain of the email address. The downside with this technique is that some legitimate mail servers don’t have the proper rDNS records setup on their end to respond properly because in many cases their ISP has to set these records up.

Reverse DNS records can be set up for both ipV4 and ipV6 records.

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Margaret Rouse
Technology Expert
Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.