No. Absolutely beginner level blog post. You would use a third party tool like http://www.datavalidation.com/ or mailgun's email validation service or BriteVerify etc etc. There are a ton of validation services now. We are living in a time when trillions of email addresses have been tried, entered and deployed to. So why reinvent the wheel on your website? 3rd party services are based not only on parsing the string but also on literally billions of emails actually deployed through various ESP's to tell you up front whether the email address entered by a user is correct. I could use a trashmail email address and it would validate by the OP's standards. First validate using a third party service and then send the double opt-in email to get a user click.