Free tool · MX record lookup
MX Record Lookup
Enter a domain to see the mail servers that receive its email, in the order senders try them — and whether each one actually works.
What an MX record does
An MX (mail exchanger) record tells the rest of the internet which server accepts email for a domain. When someone sends a message to you@example.com, their mail server looks up the MX records for example.com and delivers to the server listed there. Without working MX records, a domain can’t reliably receive email — whatever its website does.
Each MX record has two parts: a priority (sometimes called preference) and a host name:
example.com. MX 1 smtp.google.com.How priority works
Senders try the MX with the lowest number first. If it doesn’t answer, they move to the next. Records with the same number share the load. The numbers themselves don’t matter, only their order — 1 and 10 behave exactly like 10 and 20.
Hosted email often needs only one record. Google Workspace’s current setup is a single MX, smtp.google.com with priority 1, and Microsoft says a single MX record pointing to Exchange Online is best, because extra MX records left over from an old provider can cause delivery problems.
What this lookup checks
| Finding | What it means |
|---|---|
| MX host doesn’t resolve | The server named in the MX has no A or AAAA address, so senders can’t connect to it. Usually a typo or a server that was retired. |
| MX is an IP address | An MX must name a host, not an address. Some DNS panels accept an IP, but many senders won’t deliver to it. |
| MX points to an alias (CNAME) | RFC 2181 says an MX must point to a host’s real name. Most senders cope, some don’t — point it at the real name. |
| No MX records | Senders fall back to the domain’s own A/AAAA address (RFC 5321, section 5.1). That only works if a mail server runs there; normally it means mail is lost or bounced. |
| Null MX | A single MX of . with priority 0 says “this domain never receives email” (RFC 7505). It’s the right setting for domains that don’t use email, and makes mail to them bounce straight away. |
Changing MX records
MX records live wherever your domain’s DNS is hosted — usually your registrar or DNS provider, not your email provider. When you move email to a new service:
- Copy the exact MX values from your new provider’s setup page. Microsoft 365, for example, gives each domain its own target ending in
mail.protection.outlook.com. - Add the new records and remove the old provider’s MX records, so senders don’t keep delivering to the old mailbox.
- Wait for the change to spread. Google says new MX records can take up to 72 hours to be recognised.
- Run this lookup again to confirm only the new servers appear, then check SPF, DKIM and DMARC for the new provider.
Results here are cached for a few minutes, so a change you’ve just made may take a moment to show.
Questions
How do I find a domain’s mail server?
Look up its MX records. The host with the lowest priority number is the main mail server; others are backups or share the load.
Does a lower MX priority number mean higher priority?
Yes. Senders try the lowest number first and fall back to higher numbers only if it can’t be reached.
Can an MX record point to an IP address?
No. An MX must name a host that has its own A or AAAA record. Create a host name for the server and point the MX at that.
What is a Null MX record?
A single MX record of “.” with priority 0, defined in RFC 7505. It tells senders the domain accepts no email, so messages to it bounce immediately instead of being retried.
Why does my domain still get mail at the old provider?
The old MX records are probably still published, or DNS hasn’t caught up yet. Remove the old records and allow up to 72 hours.
How long do MX record changes take?
It depends on your DNS host and the old records’ TTL. Google says new MX records can take up to 72 hours to be recognised.
My domain never receives email. What MX should it have?
A Null MX: one record of “.” with priority 0. Senders then know straight away that mail to the domain can’t be delivered.
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