MX Lookup

What does the result table contain?

One row per MX record, sorted from the lowest priority number to the highest, with the columns Priority, Mail Server and TTL. A summary below it gives the count of mail servers found and the "Lowest priority" host, which is the one senders try first. Trailing dots on host names are removed for display.

What does the priority number mean?

It is a preference value, not a count. Sending servers try the lowest number first and move to higher numbers if that host does not respond. Records with the same number are equally preferred, and senders typically spread delivery among them. The actual numbers carry no meaning beyond their order, so 10 and 20 behave the same as 1 and 2.

What if the lookup says no MX records were found?

Then the resolver returned no MX data for exactly the name you typed. Under the SMTP standard (RFC 5321), a sender with no MX record falls back to the domain’s own address record, so mail may still be attempted, but a domain that is meant to receive mail should publish MX records. Also check that you entered the domain that appears after the @, not a web host name like www.

A domain shows a priority of 0 and an empty mail server. Why?

That is probably a "null MX" (RFC 7505), where the host is a single dot meaning the domain deliberately accepts no mail. The tool strips trailing dots from host names, so the dot disappears and the cell looks empty. It is a valid configuration for domains that never receive email.

How can I tell which email provider a domain uses?

Read the host names. Hosts under google.com, such as aspmx.l.google.com, indicate Google Workspace or Gmail, and hosts ending in mail.protection.outlook.com indicate Microsoft 365 (Exchange Online). Other providers use their own domains. If several providers appear, or a security gateway sits first, the first-priority host may be a filtering service rather than the mailbox host.

Can an MX record point to an IP address or a CNAME?

An MX target must be a host name that has its own A or AAAA record. IP addresses are not valid targets, and RFC 2181 says an MX must not point at an alias (CNAME). This tool shows the target but does not check either rule, nor whether the target host resolves.

Does it test whether the mail servers actually work?

No. It reads the MX records only. It does not connect to port 25, test delivery, check for open relays or blocklists, or look at SPF, DKIM and DMARC. A correct-looking list says only that the DNS side is published.

Why might my new MX records not appear?

The query goes to Cloudflare’s public resolver, which may still hold the previous answer until its TTL expires, and the web service adds a short 60-second cache on top. Compare the TTL column with when you made the change before assuming the edit failed.