MX lookup
Find the mail servers for any domain, in the order senders try them, and see which email provider hosts the mailbox.
Results appear here. Choose record types above, then press Look up.
How mail delivery uses MX records
When someone sends to you@example.com, their server looks up the MX records for example.com, sorts them by priority, resolves the first hostname to an IP and opens an SMTP connection on port 25. If that fails, it moves to the next priority and keeps retrying for up to several days before bouncing.
Checklist when mail isn't arriving
- Every MX target resolves to an A or AAAA record (click through with the DNS lookup).
- Port 25 on the mail server is reachable: test with the open port checker.
- The server's IP has a PTR record that points back to its name: check reverse DNS.
- SPF, DKIM and DMARC are published so receivers trust the domain's outgoing mail: SPF, DKIM, DMARC.
Questions people ask
What is an MX record?
A Mail Exchanger record tells other mail servers where to deliver email for a domain. Each has a priority number and a hostname; senders try the lowest number first and fall back to higher ones.
What if a domain has no MX record?
By RFC 5321, senders fall back to the domain's A/AAAA record. If the domain should never receive mail, publish a "null MX" instead:
0 . (RFC 7505).Can an MX record point to an IP address or a CNAME?
No. The target must be a hostname with its own A or AAAA record, and it must not be a CNAME (RFC 2181). Some servers tolerate it, many reject it.
Why do equal priorities appear?
Servers with the same priority share load: senders pick among them at random. Google Workspace and Microsoft 365 use this pattern.