Most distributed systems are built on top of a message exchange infrastructure. Processes coordinate their execution by exchanging messages which are interpreted according to a pre-established set of protocols. We present in this paper a novel way of communicating which does not require the preconfiguration of protocol entities. The host initiating the communication has the ability to instruct the other host “how” the data exchange has to take place. We call this “communication by messengers”. The host that initiates the data exchange sends to the recipient a program called “messenger” which contains all or parts of the protocol logic. After it has been received by the recipient, the messenger is executed and can, if necessary, deliver its payload. Communication by messengers will change the way distributed systems are built. This paper discusses the impact of the messenger paradigm in various fields such as communication protocols, distributed operating systems and intelligent agents.