I answer myself, hope it will help somebody else ...
@return true Returns true if message reached the **first stop ** on its way to destination.
indeed, it clarifies my question...

/**
	* Sends a message to gateway or one of the other nodes in the radio network
	*
	* @param msg Message to send
	* @param ack Set this to true if you want destination node to send ack back to this node. Default is not to request any ack.
	* @return true Returns true if message reached the first stop on its way to destination.
	*/
	bool send(MyMessage &msg, bool ack=false);