The Domain Name System (DNS) is the internet’s directory: it translates a domain name such as yourbusiness.co.uk into the numeric addresses of the servers that host its website, receive its email and run its other services. Every visit to a website and every email sent to your domain starts with a DNS lookup.
How DNS works
When someone types your domain, their device asks a resolver, usually run by their broadband provider or a public service, where to find it. The resolver works down the chain: starting from the root servers, it asks the servers responsible for the top-level domain which nameservers are authoritative for your domain, then asks those nameservers for the record it needs. The answer is cached for a set time so the next lookup is instant.
The nameservers hold your DNS zone, a list of records. The ones a business owner meets most often are:
- A and AAAA records Point the domain to the IPv4 or IPv6 address of the web server. An A record is what moves your website when you change host.
- CNAME Points one name at another, often used for www or for services such as a booking platform on a subdomain.
- MX records Say which servers accept email. Get an MX record wrong and mail stops arriving.
- TXT records Hold text used for verification and email authentication, including SPF, DKIM and DMARC, and site ownership checks for Google Search Console.
Each record has a TTL (time to live) in seconds, which tells resolvers how long they may cache it. A TTL of 3600 means a change can take up to an hour to reach everyone; some providers use 24 hours.
Why it matters
DNS sits underneath everything online, so mistakes have wide effects. A wrong A record takes the website offline. A deleted MX record stops email. Missing SPF, DKIM and DMARC records make it more likely that your emails land in spam, because the large mailbox providers now expect bulk senders to authenticate their mail. And during a website move, DNS is the switch that sends visitors and Googlebot to the new server.
It also matters who controls it. The DNS zone may be hosted by your registrar, your web host, a CDN provider such as Cloudflare or your email provider. Many UK small businesses do not know which, and only find out when something breaks.
Common mistakes
- Changing nameservers without copying records. Moving DNS to a new provider without recreating every existing record, especially MX and TXT, is the classic way email disappears during a website change.
- Forgetting the TTL. Making a big change with a 24-hour TTL means some visitors reach the old server for a day. Lower it a day or two before.
- Several SPF records. A domain should have one SPF record; adding a second for a new email tool breaks both.
- No record of who has access. DNS logins held by a departed developer leave the business unable to make urgent changes.
How to act on it
Find out where your DNS is hosted by looking up your nameservers, then make sure the business holds that login with two-factor authentication switched on. Export or screenshot the full list of records and keep it safe; that list is your recovery plan if anything goes wrong.
Before any website or email move, lower the TTL on the records you will change, make the change at a quiet time, and test the website and email immediately afterwards. A free DNS lookup tool shows what the rest of the internet currently sees. Timing the DNS switch and checking it afterwards is a standard step in my website migration SEO plans.