public function mail($from)
    {
        if ($this->_sess !== true) {
            /**
             * @see Zend_Mail_Protocol_Exception
             */
            // require_once 'Zend/Mail/Protocol/Exception.php';
            throw new Zend_Mail_Protocol_Exception('A valid session has not been started');
        }

        $this->_send('MAIL FROM:<' . $from . '>');
        $this->_expect(250, 300); // Timeout set for 5 minutes as per RFC 2821 4.5.3.2

        // Set mail to true, clear recipients and any existing data flags as per 4.1.1.2 of RFC 2821
        $this->_mail = true;
        $this->_rcpt = false;
        $this->_data = false;
    }