The invention provides a method of transmitting a message from a first computer (1, 2, 3) to at least one second computer (3, 2, 1), the method comprising the step in the first computer of introducing transmission information into a message header, and further comprising the step, in the first computer, of introducing into the message header at least one management instruction for managing a filing space and suitable for execution by the second computer. The invention also provides a corresponding messaging system.