What is an MX record?

An MX record is a DNS entry naming a mail server that accepts email for a domain, along with a priority number where lower values are tried first. A domain needs at least one to receive email; with none, every address at that domain is undeliverable.

How do I find a domain's mail server?

Look up its MX records: paste the domain into the tool above and it returns the mail servers in priority order. The hostname usually identifies the provider: aspmx.l.google.com for Google Workspace, a mail.protection.outlook.com host for Microsoft 365.

What is the MX record for Gmail?

Gmail.com's own MX records point at gmail-smtp-in.l.google.com and its alt1 to alt4 backups. For a Google Workspace domain, Google's current setup is a single record, smtp.google.com with priority 1; older setups use aspmx.l.google.com and its alternates, which still work.

What is an MX record used for?

It tells sending servers where to deliver email for a domain. Without one, mail to that domain has nowhere to go. MX records only affect incoming mail; outgoing mail is authorised by SPF, DKIM and DMARC.

Can a domain have more than one MX record?

Yes, and most do. Multiple records provide failover: the sending server tries the lowest priority value first and falls back to the next if it is unreachable. Records sharing the same priority value are used interchangeably to spread load.

Does a valid MX record mean an email address is real?

No. MX proves the domain can receive mail, nothing more. The specific mailbox may not exist. Confirming that requires an SMTP conversation with the server, which is what a mailbox check does. MX is the second of several steps, not the answer.

MX record lookup

In short: Free MX lookup: check the MX records for any domain and see which mail servers accept its email, in priority order, and which provider runs them. Limit: An MX record proves the domain can receive mail. It says nothing about whether a particular mailbox exists; that takes an SMTP check.

An MX lookup returns the mail servers that accept email for a domain, each with a priority number where lower is tried first. To check MX records, enter the domain above. A domain with no MX record cannot receive email, which makes this the fastest way to rule out addresses at dead or misspelled domains.

Free, no account. DNS only: nothing is sent to the domain's mail servers. Ten lookups a minute.

By SimpleVerifier Team · Last updated October 17, 2026

Also in: Português (Brasil) · Español

SimpleAPI

Sample result

acme.example can receive mail; its first-choice mail server is aspmx.l.google.com.

Domain: acme.example
Lowest MX: aspmx.l.google.com

What this means for you

The domain accepts email, so the next question is whether each address there exists.

Next step:Check an address there is real

Mail servers that accept the domain's email
Lower priority numbers are tried first
No MX means the domain can't receive mail
DNS only, nothing sent to the domain

MX
DNS
Mail servers

SimpleAPI

Sample result

acme.example can receive mail; its first-choice mail server is aspmx.l.google.com.

Domain: acme.example
Lowest MX: aspmx.l.google.com

What this means for you

The domain accepts email, so the next question is whether each address there exists.

Next step:Check an address there is real

Mail servers that accept the domain's email
Lower priority numbers are tried first
No MX means the domain can't receive mail
DNS only, nothing sent to the domain

MX
DNS
Mail servers

What does the MX priority number mean?

It sets the order servers are tried in: lowest first. Each MX record carries a preference value, and sending servers try the lowest first. A domain listing 1 aspmx.l.google.com and 5 alt1.aspmx.l.google.com will always attempt the first unless it is unreachable, at which point the second takes over. Equal values are load-balanced.

The numbers are relative, not absolute: 1 and 10 behave exactly like 10 and 20. Only the ordering matters, which is why comparing preference values between two different domains tells you nothing.

How do I tell the email provider from an MX record?

Read the hostname: MX hostnames give away who runs the mail, and that is often the most useful thing on this page. Google Workspace points at smtp.google.com on newer setups and aspmx.l.google.com on older ones (Google's MX values), Gmail itself at gmail-smtp-in.l.google.com, Microsoft 365 at a *.mail.protection.outlook.com host, Zoho at mx.zoho.com, Proton at *.protonmail.ch. A hostname on the domain's own name usually means self-hosted mail.

This matters for verification because providers differ in how they answer mailbox probes. Microsoft tenants reject unknown recipients crisply; some self-hosted servers accept everything; others greylist an unfamiliar sender on the first attempt regardless of the address.

What happens when a domain has no MX record?

Mail to it normally fails: no MX means the domain cannot receive mail, so every address at it is invalid. In a lead list the cause is often a typo in the domain rather than a domain that genuinely has no mail: gmial.com has no mail server, and the useful response is to suggest gmail.com rather than simply report a failure.

One edge case is worth knowing: RFC 5321 lets a domain with no MX but with an A record receive mail at that address, the "implicit MX". Few real mail domains rely on it, so treat a missing MX as a strong sign the address won't work. A domain that wants no mail at all should publish a null MX instead.

How do I look up MX records from the command line?

Use nslookup -type=mx example.com on Windows, Mac or Linux, dig mx example.com +short on Mac and Linux, or Resolve-DnsName example.com -Type MX in PowerShell. Each returns the same preference numbers and hostnames this page shows. The tool above is quicker when you also want the provider named and the result explained.

How do I look up a domain's MX records?

Type the domain, the part after the @, into the box. acme.com, not [email protected].
Press Check MX. The lookup runs on our server, up to ten a minute.
Read the mail servers in priority order. The lowest number is tried first.
Read the hostnames to see who runs the mail, such as Google Workspace or Microsoft 365. No MX usually means a typo in the domain.

Example

You enter: The domain acme.example.
You get: It can receive mail: 2 mail servers, and the first-choice (lowest priority) one is aspmx.l.google.com.
Limits: Ten lookups a minute per IP address, one domain at a time; a DNS lookup only.

Who uses this tool, and for what?

Cold emailers: Rule out dead domains in a lead list before paying to verify them. A domain with no MX can't receive mail, so every address at it bounces.
IT admins: Confirm a mail migration took effect: after a move to Microsoft 365 or Google Workspace, the MX should point at the new provider only.
Sales ops: See which provider a prospect's company uses. It tells you how their filters are likely to treat outreach, and is the same signal the email provider lookup uses.

What can’t this tool tell you?

An MX record proves the domain can receive mail. It says nothing about whether a particular mailbox exists; that takes an SMTP check.
DNS answers are cached. A record you changed a few minutes ago can still show its old value until the TTL expires.
A null MX (a single record pointing at .) means the domain publicly states it accepts no mail (RFC 7505).
Security gateways such as Mimecast or Proofpoint hide the mailbox provider behind them, so the hostname shows the gateway, not who hosts the inboxes.

Sources

Common questions

What is an MX record?: An MX record is a DNS entry naming a mail server that accepts email for a domain, along with a priority number where lower values are tried first. A domain needs at least one to receive email; with none, every address at that domain is undeliverable.
How do I find a domain's mail server?: Look up its MX records: paste the domain into the tool above and it returns the mail servers in priority order. The hostname usually identifies the provider: aspmx.l.google.com for Google Workspace, a mail.protection.outlook.com host for Microsoft 365.
What is the MX record for Gmail?: Gmail.com's own MX records point at gmail-smtp-in.l.google.com and its alt1 to alt4 backups. For a Google Workspace domain, Google's current setup is a single record, smtp.google.com with priority 1; older setups use aspmx.l.google.com and its alternates, which still work.
What is an MX record used for?: It tells sending servers where to deliver email for a domain. Without one, mail to that domain has nowhere to go. MX records only affect incoming mail; outgoing mail is authorised by SPF, DKIM and DMARC.
Can a domain have more than one MX record?: Yes, and most do. Multiple records provide failover: the sending server tries the lowest priority value first and falls back to the next if it is unreachable. Records sharing the same priority value are used interchangeably to spread load.
Does a valid MX record mean an email address is real?: No. MX proves the domain can receive mail, nothing more. The specific mailbox may not exist. Confirming that requires an SMTP conversation with the server, which is what a mailbox check does. MX is the second of several steps, not the answer.

How do I check MX, SPF, DKIM and DMARC at once?

Run the deliverability audit: this page covers one record, and the full deliverability audit runs MX, SPF, DKIM, DMARC and blocklists together and scores the domain. Just bought a domain to send from? The new domain email setup check checks up to 25 at once and gives the exact Google Workspace, Microsoft 365 or Zoho records to add, or read the glossary entry for the concept behind this check.

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<p style="margin:6px 0 0;font-size:13px"><a href="https://simpleverifier.com/tools/mx-lookup">Free MX record lookup by SimpleVerifier</a></p>
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