A message system for delivering data in the form messages between message clients comprises a server cluster with a group of client manager nodes and a group of independent message manager nodes. The client manager nodes have the function of managing client connections, whereas the message manager are configured to store and distribute messages. The system further comprising communication channel means in the form of a multicast messagebus for providing a multicast communication channel between said at least one client manager node and said at least one message manager node. The system guarantees delivery of a message by storing it until a receiver is ready to consume it.