Email verification is a way for us to help prevent spam.
If your user enters a bad email address, they won’t get the activation email and they’ll try to register again if they really care about using your site. Enterprising individuals will just copy and paste, but what it comes down to is this: if your user enters a bad email address, you shouldn’t make it more of a problem for yourself than you have to.
A complex regex validation on the email address doesn’t introduce an additional solution, it introduces an additional problem.
At this point, why keep parsing email addresses for their format?
The result of sending an email to a badly formatted email address would be the same: it’ll get bounced. If you really want to do checking of email addresses right on the signup page, include a confirmation field so they have to type it twice.
Thanks As an administrator who disables customer accounts, I would like to be prevented from disabling a customer account if the account has unpaid invoices so that customers have a chance to pay their invoices.