Your website and your email both depend on a short list of settings that most business owners never see. That list is your DNS, short for domain name system. It decides where your website lives and where your email goes. When it is right, nobody notices it. When one line is wrong, the website disappears or the email stops arriving, and it is rarely obvious why.
This piece explains what DNS does, what is in it, and how to check yours in about ten minutes.
The internet's address book
Computers do not find each other by name. They find each other by number, called an IP address: a string of digits such as 192.0.2.10 that identifies one machine on the internet. People are bad at remembering numbers, so we use names like example.co.uk instead.
DNS is the address book that connects the two. You look up a name, and it gives you the number. Every time someone visits your website or sends you an email, their computer checks the address book first. It takes a fraction of a second, and it happens billions of times a day.
The entries in the book
Your DNS is a list of entries called records. Each record answers one question about your domain. Four kinds matter to most businesses.
- A record. Points your domain at the server your website runs on, by its IP address. This is the entry that says "the website lives here".
- CNAME record. Points one name at another name instead of a number. A CNAME (canonical name) is an alias. It is often used for "www", so www.example.co.uk follows wherever example.co.uk goes.
- MX record. Says which service receives email for your domain. MX stands for mail exchange. If this points at Microsoft 365, your email goes to Microsoft 365. If it is missing or wrong, your email cannot be delivered.
- TXT record. A note that other services read. TXT (text) records prove you own the domain, and they tell the world which services may send email in your name. Without them, your email is more likely to land in spam.
A typical small business has between five and twenty of these records. Each one was added by someone, usually for a good reason, and often years ago.
Who holds the book
Two separate jobs are involved, and they are often done by two separate companies.
The registrar is the company you rent your domain from, such as GoDaddy, 123 Reg, or Namecheap. You pay them each year to keep the name. The DNS host is the service that holds your records and answers the lookups. It is often the registrar, but it can be your website host, your email provider, or a service such as Cloudflare.
Your domain's nameservers decide which of these is in charge. The nameservers are a setting at the registrar that says "the records for this domain are kept over there". Change the nameservers, and you hand the whole address book to someone else. Any record the new holder does not have stops working at that moment.
Why one wrong line breaks things
Most DNS problems come from a change made for one reason that breaks something else.
- A new website goes live and the developer changes the nameservers to the new host. The new host has the website record, but not the email records. Email stops.
- Email moves to a new provider and the MX record is updated, but the old TXT records stay. Messages start landing in spam.
- The domain renewal fails because the card on file expired. The website and email both go offline together.
Changes also take time to reach everyone. Each record has a TTL, short for time to live: how long other computers may keep a copy before checking again. A TTL of one hour means some visitors see the old answer for up to an hour after a change. People call this delay propagation. It is the reason a fix can work for you and not yet for a customer.
How to check yours
You do not need technical skill for this. You need ten minutes and a note of what you find.
- Find your registrar. Search your email for the renewal invoice. Log in and check that auto-renew is on and the card is current.
- Find your nameservers. They are shown in the registrar's domain settings. Note which company they belong to.
- List your records. Log in to whoever runs the nameservers and export or screenshot the records. Keep the copy somewhere safe.
- Check the email records. A free lookup tool such as MXToolbox will show your MX and TXT records and flag common problems.
- Write down who has access. Note every person and company with a login. Remove anyone who has left.
If you prefer the command line, nslookup -type=mx example.co.uk shows your email records on both Windows and Mac.
When to bring someone in
Get help before moving your website, changing email provider, or changing nameservers. Those are the three moments when things break. A short check beforehand takes minutes. Fixing a broken email setup after the fact can take a day, plus the messages lost in between.
We check DNS at the start of every website and email project. If you would like someone to look over yours, get in touch.
Glossary
- DNS (domain name system): the internet's address book. It points your domain at the right website and email.
- Domain: your address on the internet, such as example.co.uk. You rent it each year.
- IP address: the number that identifies one machine on the internet.
- Record: one entry in your DNS, answering one question about your domain.
- A record: points your domain at your website's server.
- CNAME: an alias that points one name at another name.
- MX record: says which service receives your email.
- TXT record: a note other services read, used to prove ownership and protect your email.
- Registrar: the company you rent your domain from.
- DNS host: the service that holds your records and answers lookups.
- Nameservers: the setting that says which DNS host is in charge of your domain.
- TTL (time to live): how long other computers keep a copy of a record before checking again.
- Propagation: the delay while old copies of a record expire around the internet.