MX Record Lookup: 5 Simple Ways to Check MX Records

If email is not arriving at a domain, or you are verifying whether an address can receive mail at all, the first thing to check is its MX records. An MX record lookup tells you which mail servers a domain uses, whether they are configured correctly, and whether the domain can accept email in the first place. It takes seconds, requires no special software, and is the foundation of both email delivery and email verification.

Yet MX records are one of the most misunderstood parts of email infrastructure. People assume that if a domain has a website, it can receive email. That is not true: a domain can exist, resolve to a site, and still have no mail server configured at all, which means every email sent to it bounces. The only way to know is to look up the MX records.

This guide shows you exactly how to perform an MX record lookup using free built-in tools on Windows, Mac, and Linux, how to read the results including priority values, what common MX problems look like, and how MX records fit into email deliverability and verification. By the end, you will be able to check any domain's mail configuration in seconds and understand what the results mean.

What Is an MX Record?

An MX record, short for Mail Exchange record, is a type of DNS record that specifies the mail server responsible for receiving email for a domain. When someone sends an email to an address at a domain, the sending server looks up that domain's MX records to know where to deliver the message. Without an MX record, there is nowhere to route the mail, and it cannot be delivered. As Cloudflare explains, MX records are what make email routing possible across the internet.

MX records point to a hostname, not an IP

One important detail: MX records point to a hostname (a canonical name like mail.example.com), never directly to an IP address. That hostname then has its own A or AAAA record that resolves to the actual IP of the mail server. This two-step design, defined in the SMTP standard, lets domains change their mail server's IP without touching the MX record itself.

MX Records Explained Simply

If DNS and mail servers sound intimidating, here is the whole idea in one analogy. Think of the internet like a giant postal system, and a domain name like a company's street address. When you send a letter to a big company, it does not go straight to one person. It arrives at the company's mailroom, and the mailroom sorts it to the right desk.

An MX record is the sign on the building that tells the mail carrier where the mailroom is. Without that sign, the carrier has the street address (the domain) but no idea where to drop the mail, so the letter comes back undelivered. An MX record lookup is simply you walking up and reading that sign to see where a domain's mailroom is, or whether it has one at all.

What is DNS, in one sentence?

DNS (the Domain Name System) is the internet's address book. It translates human-friendly names like example.com into the technical information computers need, including which mail server handles the domain's email. An MX record is just one entry in that address book, the entry specifically for email. When you run an MX record lookup, you are asking the address book a simple question: "where does this domain receive its mail?"

Why MX Records Matter

MX records sit at the center of email delivery. If they are missing or misconfigured, email simply does not arrive, and the problems they cause are often invisible until mail starts bouncing. Here is why they matter in practice.

For anyone doing email outreach or marketing, MX records matter for a second reason: they are the first signal of whether an address is even reachable. An address on a domain with no MX records is guaranteed to bounce, which is why MX checking is a core step in verifying an email address before you send.

How to Do an MX Record Lookup

You do not need any special software to look up MX records. Every operating system ships with a built-in command-line tool that does it. Here are the methods for each platform, plus online options.

On Windows (nslookup)

Windows includes the nslookup tool. Open Command Prompt and run the command, replacing the domain with the one you want to check.

nslookup -type=mx example.com

# Example output
example.com    MX preference = 10, mail exchanger = mail1.example.com
example.com    MX preference = 20, mail exchanger = mail2.example.com

On Mac and Linux (dig)

macOS and Linux include the dig tool, which is the standard for DNS queries. Open Terminal and run:

dig example.com MX

# For a cleaner, answer-only view
dig example.com MX +short

# Example +short output
10 mail1.example.com.
20 mail2.example.com.

Using an online MX lookup tool

If you prefer not to use the command line, many free web-based MX lookup tools let you enter a domain and see its records in a browser. These are convenient for a quick check and often display the resolved IP addresses and additional DNS health information alongside the MX records.

How to Read MX Record Results

An MX record lookup returns two key pieces of information for each mail server: a priority number and a hostname. Reading them is straightforward once you know what each part means.

So a result like 10 mail1.example.com and 20 mail2.example.com tells you that mail is delivered to mail1 first, and if that server is unreachable, the sender falls back to mail2. Both belong to the same domain's mail setup. If the lookup returns nothing, the domain has no mail server, and any address there is undeliverable.

Understanding MX Priority Values

The priority value (sometimes called preference) is the part that confuses people most. The key rule is counterintuitive: a lower number means higher priority. The server with the lowest priority number is tried first.

Common MX Record Problems

Most email delivery issues that trace back to DNS come from a handful of recurring MX record problems. Here is what to look for when a lookup reveals something wrong. The good news is that an MX record lookup makes every one of them visible in seconds, so diagnosis is fast even when the underlying fix takes longer.

A simple way to diagnose any domain

When you run a lookup, this quick decision flow tells you what the result means and what to do about it. Follow the path that matches what your lookup returned.

MX Records and Email Verification

MX records are not just for diagnosing your own domain. They are a fundamental step in verifying whether someone else's email address can receive mail, which is why every serious email verification tool checks them.

The No MX verification result

When you verify an email address, the MX check is the second step, right after confirming the syntax is valid. The verifier looks up the domain's MX records to confirm a mail server exists before it even attempts to connect. If there are no MX records, the address is invalid immediately, with no need to go further. This is exactly the result MailTester.Ninja returns as No MX, meaning the domain has no mail server and the address cannot receive email. You can see how this fits alongside every other result in our guide to email verification statuses.

This is also why a domain can pass an MX check but still need deeper verification. The MX record confirms the domain can receive mail, but it does not confirm that a specific mailbox exists. A catch-all domain, for instance, has valid MX records and accepts all mail, yet individual mailboxes there cannot be confirmed by the MX check alone.

MX Records and Deliverability

Beyond verification, your own domain's MX records play a role in whether your outbound email reaches the inbox. They are one piece of the broader DNS configuration that mailbox providers inspect.

Correctly configured MX records are part of a healthy sending setup, working alongside your authentication records. While MX records govern incoming mail, they sit in the same DNS zone as the SPF, DKIM, and DMARC records that authenticate your outgoing mail, and a clean, consistent DNS configuration signals a legitimate sender. We cover the authentication side in depth in our SPF, DKIM, and DMARC guide.

Maintaining correct MX records is also part of protecting your sender reputation and keeping your bounce rate low. If you are verifying recipient addresses before sending, the MX check filters out domains that cannot receive mail at all, and combining that with full verification before each send is one of the most effective parts of a strong email deliverability strategy.

MX Lookup Glossary for Beginners

New to email infrastructure? Here are the key terms in plain language, so the rest of this guide (and any MX lookup result) makes sense.

Frequently Asked Questions

About the author

Danila Kozlov

COO at MailTester.Ninja

Danila has spent the last few years deep in email deliverability, helping SaaS companies and growth teams fix the infrastructure problems that silently kill their outbound results. As COO of MailTester.Ninja, he oversees product and operations with a single obsession: making email verification fast, accurate, and genuinely useful for the people who need it most.