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);
