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MX record lookup

Shows which servers receive mail for a domain, in which order senders try them, and whether each of them can actually be reached.

A domain such as example.com. You can paste a URL or an email address.

How this check works

We query the domain’s MX records and resolve every mail server name to its IPv4 and IPv6 addresses. Senders try the server with the lowest preference number first and fall back to the others.

Each host is checked for problems that make delivery fail or behave unexpectedly: names that do not exist, CNAME aliases (not allowed as MX targets), IP addresses written as names, private or reserved addresses and conflicting null MX records (RFC 7505). If there are no MX records, we show the address senders fall back to.

Limitations

  • We do not connect to the mail servers, so we cannot tell whether they accept connections or which TLS settings they use. A domain that receives mail still says nothing about whether a particular mailbox exists.
  • Provider names are inferred from host names and are only shown for providers we recognize reliably.
  • Checked domains are not stored or logged.

Frequently asked questions

What does MX priority mean?

Each MX record has a preference number. Senders try the lowest number first; records with the same number share the load. Higher numbers are fallbacks used when the preferred servers are unavailable.

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

No. An MX record must point to a host name that has A or AAAA records. Pointing to a CNAME is forbidden (RFC 2181), and an IP address in the MX field is treated as a host name and fails.

What is a null MX?

A single MX record with preference 0 and target “.” (RFC 7505). It declares that the domain does not accept mail, so senders fail immediately instead of retrying for days. Use it for domains that only send or that are parked.

Do I need more than one MX record?

Not necessarily. Large providers such as Microsoft 365 publish a single, highly available host. Additional records only help if they point to servers that can really accept and deliver your mail.

How long does an MX change take to apply?

Until the TTL of the old record expires in resolvers that cached it, typically minutes to a few hours. Lower the TTL a day before a planned migration.