I once had a crack at building a sensible email validation library.

* Validate the string contains "@" and a "." to the right of it.

* Validate common typos

* Validate disposable emails

* Validate MX records

* Validate SMTP server and mailbox

https://github.com/mfbx9da4/deep-email-validator

I don't have the time to keep it maintained but it works for the most part!