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

The record types you will actually use

  • A — hostname to IPv4 address. The record that puts your site on the internet.
  • AAAA — hostname to IPv6 address.
  • CNAME — an alias pointing one hostname at another. Cannot coexist with other records on the same name, and traditionally cannot be used on the root domain.
  • MX — mail exchangers with a priority number; lower numbers are tried first.
  • TXT — free-form text, used for SPF, DKIM, DMARC and ownership verification.
  • SRV — service location records used by VoIP, chat and Microsoft services.
  • NS — delegates a zone or subdomain to other nameservers.
  • CAA — restricts which certificate authorities may issue certificates for your domain.

Practical examples

; Website
@        A      3600   203.0.113.10
www      CNAME  3600   yourdomain.com.

; Mail with Google Workspace
@        MX     3600   1 smtp.google.com.

; SPF (only one SPF record per domain)
@        TXT    3600   "v=spf1 include:_spf.google.com ~all"

; DMARC
_dmarc   TXT     3600   "v=DMARC1; p=quarantine; rua=mailto:[email protected]; pct=100"

; Certificate authority restriction
@        CAA    3600   0 issue "letsencrypt.org"

TTL strategy

TTL controls how long resolvers cache an answer. Use 3600 seconds (one hour) as a default for stable records, and drop to 300 seconds a day before any planned change so the cutover is quick. Raise it again once the change is confirmed to reduce lookup latency.

Long TTLs are not a performance win worth chasing — the risk of a slow rollback during an incident is a bigger cost than a few milliseconds per lookup.

Debugging DNS problems

dig +short A yourdomain.com @8.8.8.8
dig +short MX yourdomain.com
dig TXT _dmarc.yourdomain.com +short
dig +trace yourdomain.com   # follow delegation from the root

If different resolvers disagree, you are looking at propagation. If every resolver agrees and the site is still wrong, the problem is on the server, not in DNS.

Frequently asked questions

Can I have two SPF records?

No. Multiple SPF TXT records invalidate each other. Merge all senders into one record using multiple include: statements.

Why can't I add a CNAME on my root domain?

The DNS specification forbids it alongside SOA and NS records. Use an A record, or an ALIAS/ANAME feature if your DNS provider offers one.

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