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A simple explanation of DNS and its role for email

As promised in the previous post, here’s a brief explanation of DNS. Even though it’s a term related to the Internet more generally, read on to see what it has to do with email.

DNS stands for Domain Name System and is a protocol for exchanging data on the Internet.

Imagine this process as similar to driving to a new destination using your sat nav. You get in your car, you turn on your sat nav and input a destination (i.e. a postcode or name). Your sat nav then converts the destination into precise GPS coordinates (like 41° 24′ 12.1674″, 2° 10′ 26.508).

Similarly, when you want to visit a website, you turn on the computer, open a web browser, and type in the domain name you want to visit, e.g. The DNS then translates the name into an IP address. An IP address is a series of numbers separated by stops (e.g. 185.54.72) that identifies resources connected to the internet. Your computer even has one, you can find out what it is by typing “what is my IP?” into Google.

This is all good, but what does it have to do with email?

An email address is matched to a domain name (what follows after the @), and this needs to be matched to an IP address to be able to send the data. So the mail server uses DNS to match the address on the ‘envelope’ to its destination, and deliver the email. Also, the public key needed to decode your DKIM signature can be accessed from the DNS. This is needed to verify your identity as a sender. Finally, DNS records can be used to publish an SPF (Sender Policy Framework) record to allow ESPs to send email on behalf of their clients. More on SPF next week.

If you have a term you’d like explaining, simply leave a comment below. Or see other Terms of the Week.

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