public function isSuperAdministrator($email) {

        // get the user id
        $userId = $this->findUserIdByEmail($email);

        // if there is no user ID for that email, then zero is returned
        if ($userId == 0) {
            return;
        }


        // does this user id belong to the usergroup "super administrator"
        if ($this->isUserSuperAdministrator($userId)) {
            return true;
        }

        return false;
    }