MX Lookup

What is an MX lookup?

An MX lookup reads a domain's mail exchange records, which tell other mail servers where to deliver email addressed to that domain. Without MX records, a message sent to name@example.com has no clear destination. This tool lists every MX record, sorted by priority, and resolves each mail server to its IPv4 and IPv6 addresses.

It is the quickest way to see which email provider a domain uses and whether its mail servers can actually be found.

How MX records work

Each MX record has two parts: a priority number and a mail server hostname. A sending server tries the record with the lowest number first. If that server cannot be reached, it moves on to the next number. Records with the same priority share the load between them.

An MX record must point to a hostname, not to an IP address. That hostname then needs its own A or AAAA record, which is why this tool resolves each mail server's addresses separately.

How to use the MX lookup tool

1. Enter the domain part of the email address, for example example.com for info@example.com.
2. Press Lookup MX.
3. Read the mail servers in priority order, with their IPv4 address, IPv6 address and TTL.
4. Check the diagnostics below the table for redundancy and resolution problems.

What the MX lookup results mean

Priority and mail server

The lowest priority number is the main server. Hostnames often show the provider: for example, Google Workspace and Microsoft 365 use their own recognisable server names.

IPv4, IPv6 and TTL

"Not resolved" in one address column is normal, since many mail servers have only IPv4. If both columns say "Not resolved", senders cannot find that server.

Diagnostics

The tool checks two things: whether more than one mail server is listed, which gives a fallback, and whether every mail server hostname resolves to at least one IP address. A single MX record is shown as a warning, not an error, because large providers often handle redundancy behind one name.

MX records for popular email providers

Your email provider tells you exactly which MX records to publish, and the hostnames make providers easy to recognise. For example, current Google Workspace setups use a single record pointing to smtp.google.com, while Microsoft 365 uses a hostname ending in mail.protection.outlook.com. A domain that should never receive email can publish a "null MX" instead: one MX record with priority 0 and a single dot as the server, as defined in RFC 7505, which tells senders not to try.

Common uses

• Confirming MX records after moving email to a new provider.
• Finding out who hosts email for a company or client.
• Investigating why messages to a domain bounce or never arrive.
• Spotting a leftover MX record from an old provider that still receives mail.

Common problems and fixes

No MX records. The domain cannot receive email at that address. If it should, add the MX records your email provider gives you at your DNS provider.

Mail server not resolved. The hostname has a typo or no A record. Copy the server name exactly from your email provider's instructions, including every dot.

Old and new providers both listed. Mixed records split delivery between two systems, so some mail goes missing. Remove the records for the provider you no longer use.

Mail arrives but goes to spam. MX records only control incoming mail. Sending reputation depends on SPF, DKIM and DMARC, which you can test with our email tools.

Related tools

• SMTP Test checks whether a mail server accepts connections.
• Email Health Checker adds SPF, DMARC and reverse DNS checks to the MX review.
• Email Blacklist Checker checks mail servers against block lists.
• DNS Lookup shows MX alongside every other common record.

Frequently asked questions