DNS Records Explained: A, MX, TXT, CNAME and More

DNS is often described as 'the phonebook of the internet,' but in practice it's a set of different record types, each doing a specific job — and misunderstanding which one to use is one of the most common reasons a website or mailbox breaks after a change.

A / AAAA — Where Your Website Actually Lives

An A record points a domain to an IPv4 address; an AAAA record does the same for IPv6. This is the record that gets you from 'example.com' to the actual server hosting your site. Get this wrong and your entire site becomes unreachable.

CNAME — An Alias for Another Domain

A CNAME record points one domain to another domain name rather than an IP address directly — commonly used for subdomains pointing at a third-party service like a CDN or a hosted platform. A CNAME can't coexist with other records on the same name, which trips up a lot of people setting up subdomains.

MX — Where Email Should Be Delivered

MX (Mail Exchange) records tell the world which mail servers accept email for your domain, each with a priority number — lower numbers are tried first. A missing or misconfigured MX record is the single most common reason a domain's email suddenly stops arriving after a migration.

TXT — The Flexible, Catch-All Record

TXT records hold arbitrary text and are used for almost everything that isn't routing traffic: SPF and DMARC email authentication, domain ownership verification for services like Google Search Console, and general configuration data other systems look for.

NS — Who's Actually Answering DNS Queries

NS (Name Server) records declare which servers are authoritative for a domain's DNS. If these are wrong or inconsistent, changes you make elsewhere may simply never take effect, because the internet is still asking the wrong servers.

Common DNS mistakes

Setting a TTL (time-to-live) far too high before a planned migration, then discovering changes take hours to propagate everywhere exactly when speed matters most. Dropping the TTL to something short (like 300 seconds) a day or two before a planned change, then raising it again afterward, avoids this entirely.

Pointing an apex domain (like `example.com`, not `www.example.com`) at a CNAME record, which most DNS providers don't actually permit at the zone apex per the DNS specification — this is a frequent point of confusion when following generic hosting tutorials that assume a subdomain setup.

Check Your Setup

Nexora Shield's DNS Scanner pulls all of these record types for any domain in one lookup, making it easy to spot a stale record left over from an old host or a typo in an MX entry.