Swift_Transport_AbstractSmtpTransport::_getReversePath PHP Method

    protected function _getReversePath(Swift_Mime_Message $message)
    {
        $return = $message->getReturnPath();
        $sender = $message->getSender();
        $from = $message->getFrom();
        $path = null;
        if (!empty($return)) {
            $path = $return;
        } elseif (!empty($sender)) {
            // Don't use array_keys
            reset($sender);
            // Reset Pointer to first pos
            $path = key($sender);
            // Get key
        } elseif (!empty($from)) {
            reset($from);
            // Reset Pointer to first pos
            $path = key($from);
            // Get key
        }
        return $path;
    }