Ask HN: Why is the email regex even required at the back end?

Wouldn't it suffice to just take the "email id" supplied by the user and send an email verification link? If it is a valid email id, then the user will receive the email verification link. And if the user verifies the email, then the backend will know it is a valid email. Otherwise the user does not get access to rest of the web app except for the option to change the email.

That will avoid having to parse the email id at the backend.