public function isValid($email)
    {
        if (false === $email = filter_var($email, FILTER_VALIDATE_EMAIL)) {
            return false;
        }

        try {
            list($local, $domain) = Utilities::parseEmailAddress($email);
        } catch (InvalidEmailException $e) {
            return false;
        }

        return !$this->adapter->isThrowawayDomain($domain);
    }