MX Lookup

MX record lookup guide

An MX (Mail Exchange) record tells other mail servers where to deliver email for a domain. This tool asks public DNS resolvers for the MX records a domain currently publishes and lists each mail server with its priority.

Supported inputs

• Domain name, for example example.com. Use the part after the @ in an email address, not a full URL.

How to read the output

• Priority (preference): A lower number is tried first. A server with priority 10 is tried before one with priority 20. Equal numbers share the load.
• Mail server host name: Must be a host name with its own A or AAAA record. An MX target should not be an IP address and should not point to a CNAME.
• Several records: Normal. The extra ones are backups or part of a hosted mail provider’s set.

Common problems

• No MX records: Senders may fall back to the domain’s A record, but most domains that want email should publish MX records explicitly. A domain that never receives mail can publish a “null MX” (a single record with priority 0 and a dot as the target, RFC 7505).
• MX points to a name that does not resolve: Mail bounces or is delayed. Check that the target host has an A or AAAA record.
• Records changed but old ones still show: Resolvers cache answers for the record’s TTL. Wait for the old TTL to expire before assuming the change failed.
• Mixed providers: MX records from two different mail providers at the same priority can split mail between them. Keep only the provider you use.

Limits

• This tool reads DNS only. It does not connect to the mail servers, so it cannot tell whether a listed server is online or accepting mail.
• Related checks: SPF, DKIM and DMARC records control who may send as your domain, and are checked separately in the Full Audit.