public function mail($from)
    {
        if ($this->_helo == false) {
            throw new SMTPException(__('Must call EHLO (or HELO) before calling MAIL'));
        } elseif ($this->_mail !== false) {
            throw new SMTPException(__('Only one call to MAIL may be made at a time.'));
        }

        $this->_send('MAIL FROM:<' . $from . '>');
        $this->_expect(250, 300);

        $this->_from = $from;
        $this->_mail = true;
        $this->_rcpt = false;
        $this->_data = false;
    }