DNS is the quiet system that everything on the internet depends on, and almost nobody thinks about — until it breaks, at which point the entire business appears to be offline even though every server is running perfectly. Understanding the basics of DNS pays off enormously: it demystifies a whole category of “the internet is down” problems, makes email and website migrations far less frightening, and helps you avoid outages caused by a single mistyped record. This guide explains DNS for business owners and non-specialist admins.
What DNS actually does
DNS, the Domain Name System, is the internet’s address book. Humans remember names like coresectech.com; computers need numeric IP addresses to actually connect. DNS translates the name into the address, every time you visit a site or send an email. When you type a domain, your device asks a chain of DNS servers “what is the address for this name?” and uses the answer to make the connection — all in milliseconds.
The record types you’ll meet
| Record | What it does | Example use |
|---|---|---|
| A | Points a name to an IPv4 address | Website hosting |
| AAAA | Points a name to an IPv6 address | Modern hosting |
| CNAME | Aliases one name to another name | www pointing to root domain |
| MX | Directs email to your mail servers | Google Workspace, Microsoft 365 |
| TXT | Holds text data for verification/policy | SPF, DKIM, DMARC, domain verification |
| NS | Says which servers are authoritative | Delegating your DNS |
TTL and why changes aren’t instant
Every DNS record has a TTL (Time To Live) — how long other servers are allowed to cache the answer before checking again. This is why a DNS change is not instant: if the TTL is 24 hours, some systems may keep using the old value for up to a day. The practical tip is to lower the TTL a day or two before a planned migration, so when you flip the record the change propagates in minutes rather than hours, then raise it again afterwards for efficiency.
DNS and your email
A surprising amount of email trouble is really DNS trouble. Your MX records decide where incoming mail is delivered, and TXT records hold the SPF, DKIM, and DMARC entries that prove your mail is legitimate and stop it landing in spam. A single wrong character in these records can silently break delivery for the whole company, which is why email migrations should always be planned carefully with DNS in mind.
Common DNS problems and their causes
- “The site works for me but not for a colleague.” Usually caching and TTL — different systems are seeing old and new records during propagation.
- Email suddenly going to spam. Frequently a broken or missing SPF/DKIM/DMARC record.
- Website down after a host change. The A record still points at the old server, or NS delegation is misconfigured.
- Intermittent internal name failures. On business networks, often internal DNS, scavenging, or a domain controller issue rather than the public internet.
Best practices
- Document your records so you know what each one is for before changing it.
- Lower TTLs before migrations, raise them after.
- Use a reputable DNS provider with good uptime and DDoS resilience.
- Protect the registrar account with MFA — losing it can mean losing the domain.
- Keep SPF, DKIM, and DMARC correct to protect deliverability and your brand.
Frequently Asked Questions
How long does a DNS change take to work?
It depends on the record’s TTL and caching along the way — from a few minutes to 24–48 hours. Lowering the TTL in advance makes planned changes propagate quickly.
Should we run our own DNS servers?
For public DNS, a managed provider is usually more reliable and secure than self-hosting. Internally, businesses running Active Directory do operate internal DNS, which needs proper configuration and monitoring.
Keep the internet’s address book working for you
Well-managed DNS prevents outages, protects your email, and makes migrations painless. If you would like help auditing or migrating your DNS safely, contact our engineers, or explore our business networking guides.