Normal email validators check to see if the email address submitted is syntactically correct, but don't actually check to see if the address is real. Asking customers to confirm their email address is effective at weeding-out spam registrations, but has been proven to substantially reduce conversion rates. Spam registrations and bot signups can pollute your user-acquisition metrics, and spam newsletter signups can pollute your mail server IP space, leading to low deliverability or even service suspensions by your mailing list provider. https://goodforms.com/