MX Lookup - Check MX Records for Any Domain
Find the mail servers that receive email for a domain, with priority, IP addresses, TTL and the detected email provider. Then test any of them with the SMTP tester in one click.
How to Read MX Lookup Results
Each row is one MX record. The priority decides the order senders try the servers, the mail server is the hostname that accepts SMTP connections on port 25, and the IP addresses are what that hostname resolves to. If a hostname does not resolve, mail to that server will fail.
The Test button opens the SMTP Test Tool with that server and port 25 filled in, so you can confirm it answers, offers STARTTLS and accepts mail.
Common MX records by provider
| Mail server | Provider |
|---|---|
| smtp.google.com | Google Workspace (current single-record setup) |
| aspmx.l.google.com | Google Workspace (legacy five-record setup) |
| <domain>.mail.protection.outlook.com | Microsoft 365 / Exchange Online |
| mx.zoho.com | Zoho Mail |
| mail.protonmail.ch | Proton Mail |
| in1-smtp.messagingengine.com | Fastmail |
| *.mimecast.com / *.pphosted.com | Mimecast / Proofpoint gateways |
Common MX Record Problems
- MX points to a CNAME or IP address. Both are invalid. Point MX at a hostname with an A/AAAA record.
- Old records left behind after a migration. Mail is split between the old and new provider. Remove every MX that no longer belongs to you.
- Backup MX that is not maintained. Spammers target low-priority backup servers that skip filtering. Only keep a backup MX if it applies the same checks.
- Mail server hostname does not resolve. A typo in the MX target makes delivery fail for every sender.
- MX is correct but mail still bounces. Check sender authentication with the SPF checker and DMARC checker, and test the server directly with the SMTP tester.
MX Record FAQ
What is an MX record?
An MX (Mail Exchanger) record is a DNS record that tells other mail servers where to deliver email for a domain. Each MX record has a priority number and a hostname. Sending servers try the host with the lowest number first and fall back to higher numbers if it is unavailable.
What does the MX priority number mean?
Lower numbers are preferred. With records at priority 10 and 20, senders deliver to the 10 server and only use the 20 server if the first one cannot be reached. Records with the same priority share the load roughly equally.
What happens if a domain has no MX record?
Under RFC 5321, senders fall back to the domain's A or AAAA record and try to deliver there. If there is no A record either, the domain cannot receive email. To state explicitly that a domain accepts no mail, publish a null MX record (priority 0, host ".") as defined in RFC 7505.
Can an MX record point to an IP address or a CNAME?
No. An MX record must point to a hostname that has its own A or AAAA record. Pointing MX at an IP address or at a CNAME breaks the standard and some senders will refuse to deliver.
How long do MX record changes take to apply?
Resolvers cache the old record for up to its TTL (shown in the results). Most providers use 300 to 3600 seconds, so changes are usually visible within an hour. Lower the TTL a day before a planned mail migration to make the switch faster.
How does this MX lookup work?
Your browser queries public DNS-over-HTTPS resolvers (Cloudflare, with Google as a fallback) for the domain's MX records, then resolves each mail server's A and AAAA records. Nothing is sent to smtp-test.com servers.
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