Legit

BREAKING CHANGE NOTICE (v2.0.0): Legit has been migrated to TypeScript. This introduces a breaking change in how the module is imported. Please update your code to use ES module imports (import legit from 'legit') instead of require.

A wrapper for the NodeJS Dns.resolveMx method that checks the domain of an email address for valid/existence of MX records.

Installation

$ npm install legit

Usage

import legit from "legit";

legit("[email protected]")
  .then((result) => {
    result.isValid ? console.log("Valid!") : console.log("Invalid!");
    console.log(JSON.stringify(result));
  })
  .catch((err) => console.log(err));

If an email domain is legit then the object returned will include an isValid key that will be set to true as well as an mxArray key with all the MX record information for the valid domain.

If the domain has no MX or cannot resolve any MX then it will return isValid as false.

Anything else is considered an error and you'll get it in the .catch

Async/Await Usage

For a more modern approach using ES6, you can await the response before acting on it.

import legit from "legit";

(async () => {
  try {
    const response = await legit("[email protected]");
    response.isValid ? console.log("valid") : console.log("invalid");
  } catch (e) {
    console.log(e);
  }
})();

Example Response

For a valid email address, you'll get the following response object:

{
  "isValid": true,
  "mxArray": [
    {
      "exchange": "aspmx.l.google.com",
      "priority": 1
    },
    {
      "exchange": "alt1.aspmx.l.google.com",
      "priority": 5
    },
    {
      "exchange": "alt2.aspmx.l.google.com",
      "priority": 5
    },
    {
      "exchange": "alt3.aspmx.l.google.com",
      "priority": 10
    },
    {
      "exchange": "alt4.aspmx.l.google.com",
      "priority": 10
    }
  ]
}

License

(The MIT License)

Copyright (c) 2015-2025 Martyn Davies, and contributors.