The Javascript library and jQuery plugin that suggests a right domain when your users misspell it in an email address.

When your user types in "[email protected]", Mailcheck will suggest "[email protected]".

Mailcheck will offer up suggestions for second and top level domains too. For example when a user types in "[email protected]" then "hotmail.com" will be suggested. Similarly if only the second level domain is miss-spelled then it will be corrected independently of the top level domain allowing for fine resolution tweaking if desired.

At Kicksend, we use Mailcheck to help reduce typos in email addresses during sign ups. It has reduced our sign up confirmation email bounces by 50%.

See it live in action here.

For instant use, download the minified library mailcheck.min.js into your javascripts directory. mailcheck.js is also available unminimised if you want to hack on it, or have your own minimizer.

> bower install --save mailcheck

> npm install --save mailcheck

First, include jQuery and Mailcheck into the page.

<script src="jquery.min.js"></script>
<script src="mailcheck.min.js"></script>

Have a text field.

<input id="email" name="email" type="email" />

Now, attach Mailcheck to the text field. You can declare an array of domains, second level domains and top level domains you want to check against.

<script>
var domains = ['gmail.com', 'aol.com'];
var secondLevelDomains = ['hotmail']
var topLevelDomains = ["com", "net", "org"];

var superStringDistance = function(string1, string2) {
  // a string distance algorithm of your choosing
}

$('#email').on('blur', function() {
  $(this).mailcheck({
    domains: domains,                       // optional
    secondLevelDomains: secondLevelDomains, // optional
    topLevelDomains: topLevelDomains,       // optional
    distanceFunction: superStringDistance,  // optional
    suggested: function(element, suggestion) {
      // callback code
    },
    empty: function(element) {
      // callback code
    }
  });
});
</script>

Mailcheck takes in two callbacks, suggested and empty. We recommend you supply both.

suggested is called when there's a suggestion. Mailcheck passes in the target element and the suggestion. The suggestion is an object with the following members:

{
  address: 'test',          // the address; part before the @ sign
  domain: 'gmail.com',    // the suggested domain
  full: '[email protected]'  // the full suggested email
}

Mailcheck does not want to get in the way of how you can show suggestions. Use the suggestion object to display suggestions in your preferred manner.

empty is called when there's no suggestion. Mailcheck just passes in the target element. It is a good idea to use this callback to clear an existing suggestion.

Mailcheck is decoupled from jQuery, so its usage without jQuery is almost identical.

Using the example from above, you would call Mailcheck.run instead.

<script>
Mailcheck.run({
  email: yourTextInput.value,
  domains: domains,                       // optional
  topLevelDomains: topLevelDomains,       // optional
  secondLevelDomains: secondLevelDomains, // optional
  distanceFunction: superStringDistance,  // optional
  suggested: function(suggestion) {
    // callback code
  },
  empty: function() {
    // callback code
  }
});
</script>

The rest works similarly. In fact, the Mailcheck jQuery plugin just wraps Mailcheck.run.

If you're running this on Node.js, you can just require('mailcheck') to get the mailcheck object, and call run on that:

var mailcheck = require('mailcheck');

mailcheck.run({
  // see 'usage without jQuery' above.
});

Mailcheck has inbuilt defaults if the domains, secondLevelDomains or topLevelDomains options aren't provided. We still recommend supplying your own domains based on the distribution of your users.

You can replace Mailcheck's default domain/TLD suggestions by supplying replacements to mailcheck.run:

Mailcheck.run({
  domains: ['customdomain.com', 'anotherdomain.net'], // replaces existing domains
  secondLevelDomains: ['domain', 'yetanotherdomain'], // replaces existing SLDs
  topLevelDomains: ['com.au', 'ru'] // replaces existing TLDs
});

Alternatively, you can extend Mailcheck's global set of default domains & TLDs by adding items to Mailcheck.defaultDomains and Mailcheck.defaultTopLevelDomains:

Mailcheck.defaultDomains.push('customdomain.com', 'anotherdomain.net') // extend existing domains
Mailcheck.defaultSecondLevelDomains.push('domain', 'yetanotherdomain') // extend existing SLDs
Mailcheck.defaultTopLevelDomains.push('com.au', 'ru') // extend existing TLDs

The Mailcheck jQuery plugin wraps Mailcheck. The prime candidates for customization are the methods Mailcheck.findClosestDomain and Mailcheck.stringDistance.

Mailcheck currently uses the sift3 string similarity algorithm by Siderite. You can modify the inbuilt string distance function, or pass in your own when calling Mailcheck.

Since Mailcheck runs client side, keep in mind file size, memory usage and performance.

Mailcheck is tested with Jasmine. Load spec/spec_runner.html in your browser to run the tests or run npm test from the command line to test in node.

Let's make Mailcheck awesome. We're on the lookout for maintainers and contributors.

And do send in those pull requests! To get them accepted, please:

• Test your code. Add test cases to spec/mailcheckSpec.js, and run it across browsers (yes, including IE).
• Minify the plugin by running grunt in the Mailcheck directory.

Upcoming features, bugs and feature requests are managed in Issues.

Start contributing to Mailcheck instantly on Nitrous.IO:

• Kicksend
• Dropbox
• Kickstarter
• Uber
• Khan Academy
• Minecraft
• Paperless Post
• The Verge
• SB Nation
• Kippt
• Shopify

Do you use Mailcheck? Tweet me your link.

• Official Mailcheck Ports
• Two ways to reduce bounced welcome emails by Postmark
• MooTools port by Dimitar Christoff
• WordPress Plugin by Drew Poland
• WordPress e-Commerce Plugin
• Mailcheck for Drupal by Martin Elvar

• Derrick Ko, Kicksend, @derrickko. Created Mailcheck.
• Wei Lu, Hive, @luweidewei.

Released under the MIT License.