MX lookup
See which mail servers receive email for a domain, in priority order, with each server's addresses.
Choosing a check opens its page. With the keyboard, use the arrow keys, then press Enter.
What we check
We look up the domain's MX records, which name the servers that receive its email, and then the IPv4 and IPv6 addresses of each server (the first eight, in priority order). We point out common mistakes: an MX record that names an alias or an IP address, a server with no address, or one with a private address. We never connect to the mail servers.
Special cases
- Null MX ("0 ."): the domain says it never accepts email (RFC 7505).
- No MX record: senders fall back to the domain's own address, which often isn't a mail server.
- Priority: lower numbers are tried first; equal numbers share the load.
Frequently asked questions
What does the MX priority number mean?
Lower numbers are tried first. Servers with the same number share the load. A higher number is usually a backup that receives mail only when the others can't.
What is a null MX?
A single MX record of "0 ." (RFC 7505). It says the domain never accepts email, so senders give up straight away instead of retrying for days.
What happens if a domain has no MX record?
Mail servers fall back to the domain's own address (an "implicit MX", RFC 5321). That often isn't a mail server, so mail may be lost. Publishing an MX record, or a null MX if the domain doesn't take mail, avoids this.
Why must an MX record not point to a CNAME or an IP address?
The standards require an MX record to name a host that has its own address records. Many mail servers still cope with an alias, but some don't, and an IP address in an MX record isn't valid at all.
Do you test whether the mail server is working?
No. This is a DNS check only. We don't connect to mail servers, so it can't tell whether a server accepts mail right now.
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