    public function recipient($address)
    {
        return $this->sendCommand(
            'RCPT TO',
            'RCPT TO:<' . $address . '>',
            array(250, 251)
        );
    }
The product receives input or data, but it does
        not validate or incorrectly validates that the input has the
        properties that are required to process the data safely and
        correctly.