Email typo catcher

How it decides

• A short list of well-known domains: gmail.com, yahoo.com, outlook.com, hotmail.com, icloud.com and a dozen more, plus any you add above.
• Count the edits between the typed domain and each one on the list. A missing, extra or wrong letter is one edit, and so is a swap of two neighbours (gmial.com).
• One edit for short names, two for long ones. Domains of nine letters or more (hotmail.com, outlook.com) get two, shorter ones get one, so me.com and mac.com don't pull in every three-letter domain.
• A domain on the list is never corrected. ymail.com, mail.com, email.com and me.com are one edit from bigger names and are real. Add the providers your own users have, or they will be "corrected" too.
• Company domains are left alone. acme.co might be a typo of acme.com or might be the company. With nothing famous to compare to, there is nothing to say.

The tool can't see a slip before the @ (smaa@ for sam@). Only a code or a link sent to the address catches that one, which is why sign-up still ends with a confirmation.

Use it in your sign-up form

The same function, with your extra domains in the list. Run it when the field loses focus, show "Did you mean" as a button that fills the field, and let the person say no. It runs in Node too, so your API can return the suggestion for forms that skip your page.

Why a mail server check passes sam@gamil.com, what each kind of typo domain does to your email, and the input settings that stop typos before they happen: gmial.com: catching the mistyped email address before the first email goes astray.