What does MX stand for?

MX stands for Mail Exchanger. An MX record is a type of DNS record that tells other mail servers where to deliver email for a domain.

Can a domain have more than one MX record?

Yes. Most domains have at least two MX records for redundancy — a primary mail server and one or more backups. Priority values determine the order they're tried in.

Does every domain need an MX record?

Only if the domain needs to receive email. A domain used purely for a website, with no associated mailboxes, doesn't strictly need one, though many providers still recommend a placeholder record.

What Is an MX Record? A Complete Guide

By MXToolbox Team · August 10, 2026

If you’ve ever set up email for a domain — Google Workspace, Microsoft 365, or a self-hosted mail server — you’ve had to add an MX record. Here’s what it actually does.

The short version

An MX (Mail Exchanger) record is a DNS record that tells the internet which server is responsible for accepting email sent to addresses at your domain. When someone sends mail to you@yourdomain.com, the sending server doesn’t guess where to deliver it — it looks up your domain’s MX records first.

What an MX record looks like

A typical MX record has three parts: the domain, a priority number, and a mail server hostname.

yourdomain.com.   3600   IN   MX   10   mail.yourdomain.com.

Broken down:

yourdomain.com. — the domain the record applies to
3600 — the TTL (time to live), in seconds, before resolvers should re-check the record
MX — the record type
10 — the priority (also called “preference”)
mail.yourdomain.com. — the hostname of the mail server

How priority actually works

This trips people up constantly: lower priority numbers are preferred. A record with priority 10 is tried before one with priority 20.

yourdomain.com.   MX   10   mail1.yourdomain.com.
yourdomain.com.   MX   20   mail2.yourdomain.com.

Here, mail1 is the primary — sending servers try it first. If it’s unreachable, they fall back to mail2. This is how mail systems build in redundancy without any special configuration on the sending side; it’s purely a function of how MX priority is defined.

If two records share the same priority, sending servers are free to pick between them (often randomly, or round-robin), which is a simple way to spread load across multiple servers.

Why MX records point to hostnames, not IP addresses

An MX record’s value must be a hostname (like mail.yourdomain.com), never a raw IP address. That hostname then needs its own A (or AAAA) record pointing to an actual IP. This indirection means you can change your mail server’s IP address without touching the MX record itself — you just update the A record.

Common real-world MX setups

Google Workspace domains typically use a single MX record:

yourdomain.com.   MX   1   smtp.google.com.

(Older Google Workspace setups sometimes still show five aspmx.l.google.com records with priorities 1, 5, 10, 10, 10 — both are valid depending on when the domain was set up.)

Microsoft 365 domains typically look like:

yourdomain.com.   MX   0   yourdomain-com.mail.protection.outlook.com.

Checking your own MX records

You don’t need command-line tools to check this — use the free MX Lookup tool to see a domain’s MX records and priorities in your browser. For a step-by-step walkthrough of interpreting the results, see How to Check MX Records.

If you’re configuring outbound mail infrastructure alongside your MX setup — for example, warming up a new sending domain or mailbox before running cold email or sales outreach — MailPilot can help warm up mailboxes and monitor deliverability once your DNS is in place.