Inspect any domain's mail servers

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MX lookup

Check any domain's MX records: every mail server, IP, and email provider

Free MX lookup for any domain. The check runs in your browser: it returns every mail server in priority order, resolves IPv4 and IPv6 addresses, looks up reverse DNS, detects the email provider behind each MX, and flags null MX records.

Enter a domain. The lookup runs in your browser via DNS-over-HTTPS.

How to use this MX records lookup

Four steps from a domain name to a confident answer about its mail servers.

  1. 1

    Enter a domain

    Type any domain into the form above. Apex domains and subdomains both work.

  2. 2

    Run the lookup

    The tool queries DNS-over-HTTPS from your browser in real time. Results appear inline below the form in a second or two.

  3. 3

    Read priorities, hosts, IPs, and providers

    Lower priority numbers are tried first. Each row shows the mail server, every resolved IPv4 and IPv6 address with its reverse DNS, and the detected email provider when we recognize one.

  4. 4

    Verify in your DNS provider

    If something is missing, open your DNS provider, find the MX records for the apex name, and confirm each entry matches what you expected to publish.

What you can learn from an MX records lookup

An MX records lookup is one of the fastest sanity checks for an email setup. Use it to:

  • Confirm Google Workspace or Microsoft 365 setup is complete after delegating mail to a new provider.
  • Spot a domain that explicitly accepts no email via a null MX record (RFC 7505).
  • Identify the email provider behind any sending domain by matching its MX hostnames to known providers.
  • Compare backup vs primary mail servers via priority numbers, and verify a failover path exists.
  • Cross-check MX hosts against MTA-STS, SPF, and DMARC on the same domain.
  • Audit a vendor or partner's email setup before sending high-volume mail to their addresses.

Understanding MX records

What is an MX record?

An MX (Mail Exchange) record is the DNS entry that tells the internet which mail servers receive email for a domain. Each MX record has two parts: a hostname that points to a mail server, and a numeric priority. When someone sends mail to an address on your domain, their server looks up your MX records, picks a mail server, resolves its IP address, and connects to it on port 25 over SMTP to deliver the message. The MX record points to a name, never an IP address directly, so the mail server also needs a matching A or AAAA record. Without a published MX record, sending servers have no destination for your mail and typically reject it.

How priority and failover work

The number in front of each MX host is its priority, also called its preference. Lower numbers are tried first. A sending server sorts your MX records by priority, connects to the lowest-numbered host, and only moves on to a higher-numbered one if the first is unreachable. That is how backup mail servers work: give a secondary server a higher priority number and it receives mail only when the primary is down. When two MX records share the same priority, sending servers spread delivery across them, which balances load between equivalent mail servers. Publishing more than one MX record, or one hostname that resolves to several addresses, is what keeps mail flowing when a single server fails.

MX records and email authentication

MX records control where inbound mail is delivered. They say nothing about who is allowed to send mail as your domain, and they do nothing to stop spoofing. That job belongs to email authentication: SPF lists the servers allowed to send for your domain, DKIM signs your messages, and DMARC tells receivers what to do when a message fails both. A domain can have perfect MX records and still be trivially spoofed if it has no DMARC policy. Build your records with the DMARC generator and the SPF generator, then run a full check with our free domain checker to see MX, SPF, DKIM, DMARC, and MTA-STS together.

Frequently asked questions

How do I look up MX records for a domain?
Enter the domain name into the form above and submit. The tool queries DNS-over-HTTPS from your browser, returns every MX record sorted by priority, resolves each mail server's IPv4 and IPv6 addresses, looks up reverse DNS, and identifies the email provider behind each MX host.
What is an MX record?
An MX (Mail Exchange) record is a DNS record that tells the rest of the internet which mail servers are responsible for receiving email for a domain. Without an MX record, mail sent to addresses on the domain has no defined destination and is typically rejected by sending servers.
What does MX record priority mean?
Each MX record has a numeric priority (also called preference). Lower numbers are tried first. If two MX records share the same priority, mail is load-balanced between them. Backup MX servers usually have higher priority numbers so they only receive mail when the primary servers are unreachable.
Can a domain have multiple MX records?
Yes. Many domains publish two or more MX records for redundancy, each with its own priority number. Mail servers try the lowest priority number first and fall back to higher numbers when a server is unreachable. Some large providers handle redundancy behind a single hostname instead: Google Workspace now recommends one MX record (smtp.google.com at priority 1), and Microsoft 365 uses one record (your-domain.mail.protection.outlook.com). Both still work whether you publish one MX or several.
Why does my domain have no MX records?
Three common reasons: the domain is configured for outbound email only and never receives mail, the MX record was never published in DNS (a misconfiguration), or the domain has a null MX record (a single MX with priority 0 and host '.') signalling that it explicitly does not accept email per RFC 7505.
What is a null MX record?
A null MX record (RFC 7505) is a single MX record of the form '0 .' that explicitly tells the internet a domain does not accept email. Sending mail servers see the null MX and immediately reject delivery rather than retrying for days. Use it on parked domains, brand-protection domains, and any domain that should never receive mail.
What does MX stand for?
MX stands for Mail Exchange (sometimes written Mail Exchanger). An MX record is the DNS record that names the mail servers responsible for receiving email for a domain. The receiving server is called the mail exchanger, which is where the name comes from.
What port does email delivery use?
Mail servers deliver email to each other over SMTP on port 25. After your MX lookup tells a sending server which mail server to contact, it connects to that host on port 25. Port 25 is for server-to-server delivery; email clients submit outgoing mail on port 587 or 465 instead, which is a separate step that MX records do not control.
Is this MX records lookup tool free?
Yes. The MX lookup tool is completely free with no signup required. The lookup runs in your browser using public DNS-over-HTTPS resolvers, so nothing about the domain you check is stored on our servers.