It is apparent that in the transmission of email, just having the sender’s machine and the recipient’s machine is not enough. When the sender sends a message, what happens if the recipient is off line? Who receives the message for the recipient, and hold it until the recipient is ready to read the message?
We need at least one server (the third) machine in this transaction. This third machine acts as a “middle-person”. When a sender sends a message, it is transmitted to this server. The message is stored on this server until the recipient goes online to retrieve it (from the server).
Sounds like this should solve the problem, right?
Well, there is one minor detail to work out. Who owns this server? That’s a simple question, but there is no easy answer. Let us consider the following scenario.
John is a customer of Comcast, and he wants to send a message to Jennifer. Jennifer is a customer of Surewest. Which company should run the server that receives the message from John and in return delivers it to Jennifer?
This is a tricky question, by the way.