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What Is a DNS MX Record, in Plain English?

An MX record tells the internet which server handles email for a domain. Here's how it works, why it has a priority number, and how to check yours.

Zro7 MX Lookup queries Cloudflare DNS-over-HTTPS directly from your browser — no server-side proxy sees the domain you look up.

An MX (Mail Exchanger) record is a DNS entry that says: 'to deliver email for example.com, connect to this mail server.' Without it, no inbound email reaches you — the sender's server queries DNS, finds no MX, and bounces. Check any domain's MX in a second with Zro7 MX Lookup.

The 30-second mental model

  1. You send mail to [email protected].
  2. Your outgoing server asks DNS: 'MX for example.com?'
  3. DNS answers with a list of hostnames + priorities, e.g. '10 aspmx.l.google.com'.
  4. Your server connects to the lowest-priority (highest preference) host and delivers the message.

Anatomy of an MX record

  • Priority: lower = tried first. Ties are load-balanced.
  • Exchange: a hostname (not an IP). That hostname must have its own A/AAAA records.
  • TTL: how long resolvers cache it. Lower TTLs make migrations faster.

Typical MX configurations

  • Google Workspace: single line, 1 smtp.google.com (new style) or five aspmx entries (legacy).
  • Microsoft 365: 0 example-com.mail.protection.outlook.com.
  • Fastmail: two records, priority 10 and 20.
  • Self-hosted: usually 10 mail.example.com.

MX alone isn't enough — the deliverability trio

  • SPF (TXT): which servers may send as your domain.
  • DKIM (TXT): cryptographic signature proving the message wasn't tampered.
  • DMARC (TXT): what to do when SPF/DKIM fails.

Common MX mistakes

  1. Pointing MX at an IP address — invalid, must be a hostname.
  2. Missing A record for the MX hostname.
  3. Trailing dot confusion — cPanel and Cloudflare handle it differently.
  4. Two identical priorities when only one is intended.

How to check yours

  1. Open Zro7 MX Lookup.
  2. Enter your domain (no @, no www).
  3. Confirm the hostname matches your email provider's documentation.
  4. Cross-check SPF/DKIM/DMARC with DNS Lookup.

Updated December 28, 2026 · Zro7 editorial team.

Frequently asked questions

How many MX records should I have?

At least two, on different infrastructure if possible — but your provider dictates it. Google Workspace's new-style single record is fine because Google handles failover internally.

How long does an MX change take?

Up to the record's TTL. Set TTL to 300s a day before migrating.

Can I have MX and no A record on the same domain?

Yes — many domains have MX pointing to Google/Microsoft while the apex serves nothing.

Does MX affect outgoing mail?

No — outbound uses the destination's MX, not yours. SPF governs outbound.

What's a null MX?

'0 .' declares the domain accepts no mail — a recognized signal that stops backscatter.

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