Drupal email.validator service isValid accepts emails with no domain

Thanks @dmezquia

@andreasderijcke great module, thanks for your work! 🎉

IMO this issue should be reopened. Apart from https://www.drupal.org/project/commerce_paypal, there are / will be a lot of contrib modules, which require an e-mail adress to have a top-level-domain. And I don't think the modules itself should add this validation.

We should introduce a setting, to make the top-level domain optional for email validation. I adjusted the issue summary accordingly.

From my opiniton this would be a perfect example for a settings.php setting in core which can be overridden... but let's see what the others think.