Free MX Lookup

What an MX record is

An MX (mail exchanger) record tells the world which servers accept email for a domain. When someone sends mail to you@example.com, their server asks DNS for the MX records of example.com, picks a host from the answer, then looks up that host's A record (or AAAA) to find an IP address to connect to.

Each MX record has two parts: a priority and a mail host. The host must be a hostname, never an IP address and never an alias. That's the whole record. It says nothing about who sent the mail. That's SPF, DKIM and DMARC.

If a domain has no MX records at all, senders fall back to its A or AAAA record and try delivering mail there. A domain that never receives mail can say so explicitly with a null MX, the record 0 . (RFC 7505).

How priority works

The number is a preference, and lower wins. A sender tries the lowest-numbered host first. If it can't connect, it moves to the next one up.

Priority	Host	Role
10	mx1.example.net	Primary
20	mx2.example.net	Backup, used when the primary is unreachable

Two things trip people up:

• The absolute number means nothing. 10 and 20 behaves the same as 1 and 2. Only the order counts.
• Equal priorities share the load. Two hosts both at 10 get mail in roughly equal measure. That's deliberate for hosted providers and a mistake if you wanted a backup.

Common provider MX values

Most mail providers publish the same hostnames for everyone. The tool above matches hostnames against these patterns to name the provider. Check your provider's own setup page for your exact values before you change anything.

Provider	Typical MX host	Typical priority
Google Workspace	smtp.google.com (older setups: aspmx.l.google.com plus alt1 to alt4)	1 (older: 1, 5, 5, 10, 10)
Microsoft 365	<your-domain>.mail.protection.outlook.com	0
Zoho Mail	mx.zoho.com, mx2.zoho.com, mx3.zoho.com	10, 20, 50
Fastmail	in1-smtp.messagingengine.com, in2-smtp.messagingengine.com	10, 20
Proton Mail	mail.protonmail.ch, mailsec.protonmail.ch	10, 20
iCloud Mail	mx01.mail.icloud.com, mx02.mail.icloud.com	10, 10
Amazon SES / WorkMail	inbound-smtp.<region>.amazonaws.com	10
Yandex	mx.yandex.net	10
Namecheap Private Email	mx1.privateemail.com, mx2.privateemail.com	10, 10
GoDaddy / Titan	mx1.titan.email, mx2.titan.email	10, 20
Mimecast, Proofpoint	Assigned per customer and region	Varies

Anything else shows up as "Other". That's not an error. It usually means a self-hosted mail server or a smaller provider.

Why MX and a root CNAME can't coexist

A CNAME record means "this name is an alias for another name". The DNS rules say that if a name has a CNAME, it can have no other records. No MX, no TXT, no NS, no SOA.

The root of your domain (the apex) always has NS and SOA records, and usually MX and TXT too. So a CNAME there collides with all of them. Some DNS providers refuse it. Some accept it and quietly break email. A few hide it behind CNAME flattening.

That's why apex setups for apps use an A record (a fixed IP) or an ALIAS record (your DNS provider resolves the target and serves its IPs as A records). Both leave the MX records alone.

The check in the tool above is the quick version of this: is there a CNAME at the name you entered, and what MX and TXT records would it step on?

More checks for the same domain

Mail setup is more than MX. Once the routing looks right, check who's allowed to send: the SPF checker, the DKIM checker and the DMARC checker. The TXT record lookup lists everything else at the root. Changed an MX record and don't see it yet? The DNS propagation checker compares resolvers, and DNS TTL explains the wait.

Want MX records in your own code? The free DNS record lookup API returns them along with every other record type. No key, CORS-enabled. The reference docs cover the response.