protected function getSubscribedUserIdByEmail($email)
    {
        $database = \OxidEsales\Eshop\Core\DatabaseProvider::getDb();
        $sEmailAddressQuoted = $database->quote($email);
        $userOxid = $database->getOne("select oxid from oxnewssubscribed where oxemail = {$sEmailAddressQuoted} ");

        return $userOxid;
    }