public function getRecipients()
    {
        // get sender address
        $headers = $this->message->headers();
        $to      = rcube_mime::decode_address_list($headers['To'], null, false, null, true);
        $cc      = rcube_mime::decode_address_list($headers['Cc'], null, false, null, true);
        $bcc     = rcube_mime::decode_address_list($headers['Bcc'], null, false, null, true);

        $recipients = array_unique(array_merge($to, $cc, $bcc));
        $recipients = array_diff($recipients, array('undisclosed-recipients:'));

        return $recipients;
    }