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MX Lookup

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List a domain’s MX records in priority order, resolve each mail server to its IP addresses and check reverse DNS.

MX Lookup

Domain name

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How it works

The server queries the domain’s MX records through public resolvers, then resolves each mail exchanger to A/AAAA addresses and checks their PTR records.

Safeguards & responsible use

  • Only public domain names are accepted; internal names (.local, .internal, …) are rejected.
  • Queries go to public resolvers, never to internal DNS.
  • Per-client rate limiting and query timeouts.

Frequently asked questions

What does MX priority mean?

Senders try the lowest number first and fall back to higher numbers if it is unavailable. Equal priorities share the load.

What is a “null MX”?

An MX record of “0 .” (RFC 7505) states that the domain accepts no email at all.