public function getHeaders()
    {
        if ($this->_headers === null) {
            if (!$this->_mail) {
                $this->_headers = array();
            } else {
                $part = $this->_mail->getRawHeader($this->_messageNum);
                Zend_Mime_Decode::splitMessage($part, $this->_headers, $null);
            }
        }

        return $this->_headers;
    }