Contao\Validator::isEmail PHP Method

    public static function isEmail($varValue)
    {
        /*
         * The regex below is based on a regex by Michael Rushton adjusted by
         * Rasmus Lerdorf to to only consider routeable addresses as valid. We
         * have also added Unicode support for the local part.
         *
         * Michael's regex carries this copyright:
         *
         * Copyright © Michael Rushton 2009-10
         * http://squiloople.com/
         * Feel free to use and redistribute this code. But please keep this copyright notice.
         *
         * @see https://github.com/php/php-src/blob/master/ext/filter/logical_filters.c#L601
         */
        return preg_match('/^(?!(?:(?:\\x22?\\x5C[\\x00-\\x7E]\\x22?)|(?:\\x22?[^\\x5C\\x22]\\x22?)){255,})(?!(?:(?:\\x22?\\x5C[\\x00-\\x7E]\\x22?)|(?:\\x22?[^\\x5C\\x22]\\x22?)){65,}@)(?:(?:[\\x21\\x23-\\x27\\x2A\\x2B\\x2D\\x2F-\\x39\\x3D\\x3F\\x5E-\\x7E\\pL\\pN]+)|(?:\\x22(?:[\\x01-\\x08\\x0B\\x0C\\x0E-\\x1F\\x21\\x23-\\x5B\\x5D-\\x7F\\pL\\pN]|(?:\\x5C[\\x00-\\x7F]))*\\x22))(?:\\.(?:(?:[\\x21\\x23-\\x27\\x2A\\x2B\\x2D\\x2F-\\x39\\x3D\\x3F\\x5E-\\x7E\\pL\\pN]+)|(?:\\x22(?:[\\x01-\\x08\\x0B\\x0C\\x0E-\\x1F\\x21\\x23-\\x5B\\x5D-\\x7F\\pL\\pN]|(?:\\x5C[\\x00-\\x7F]))*\\x22)))*@(?:(?:(?!.*[^.]{64,})(?:(?:(?:xn--)?[a-z0-9]+(?:-+[a-z0-9]+)*\\.){1,126}){1,}(?:(?:[a-z][a-z0-9]*)|(?:(?:xn--)[a-z0-9]+))(?:-+[a-z0-9]+)*)|(?:\\[(?:(?:IPv6:(?:(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){7})|(?:(?!(?:.*[a-f0-9][:\\]]){7,})(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,5})?::(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,5})?)))|(?:(?:IPv6:(?:(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){5}:)|(?:(?!(?:.*[a-f0-9]:){5,})(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,3})?::(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,3}:)?)))?(?:(?:25[0-5])|(?:2[0-4][0-9])|(?:1[0-9]{2})|(?:[1-9]?[0-9]))(?:\\.(?:(?:25[0-5])|(?:2[0-4][0-9])|(?:1[0-9]{2})|(?:[1-9]?[0-9]))){3}))\\]))$/iDu', \Idna::encodeEmail($varValue));
    }

 /**
  * Remove the recipient
  */
 protected function removeSubscriber()
 {
     $varInput = Idna::encodeEmail(Input::get('email', true));
     // Validate e-mail address
     if (!Validator::isEmail($varInput)) {
         $_SESSION['UNSUBSCRIBE_ERROR'] = $GLOBALS['TL_LANG']['ERR']['email'];
         $this->redirect($this->generateFrontendUrl($this->objModel->getRelated('jumpTo')->row()));
     }
     $objCleverReach = new CleverReach();
     switch ($this->clr_unsubscribe) {
         case 'inactive':
             foreach ($this->clr_groups as $strGroupId) {
                 $objCleverReach->receiverSetInactive($varInput, $strGroupId);
             }
             break;
         case 'delete':
             foreach ($this->clr_groups as $strGroupId) {
                 $objCleverReach->receiverDelete($varInput, $strGroupId);
             }
             break;
         case 'email':
         default:
             $objCleverReach->sendUnsubscribeMail($varInput, $this->clr_form);
             break;
     }
     $this->redirect($this->generateFrontendUrl($this->objModel->getRelated('jumpTo')->row()));
 }