Target Skills:

Ability to describe the basics of messaging, in terms of the protocols used to send and receive messages.

 
     

Messaging Basics

Let's examine the basics of messaging, in terms of the main components and the protocols they use to communicate with each other and process messages.
 

Main Components

The main components of a messaging system are the Clients, the Messaging Servers, and the Directory Server.
  • The Clients (such as Netscape Communicator) are used by users to send and retrieve messages from the Messaging Servers.

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  • The Messaging Servers are used to send and receive messages from other servers, store messages for local users, and allow users through their Clients to send and retrieve their messages. 

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  • The Directory Server is used to store all information about user accounts, and all the configuration information for the Messaging Servers.  It ultimately determines where a message goes once it has been sent to a Messaging Server.

Basic Messaging Flow

When a message is sent off from a client to a messaging server, the messaging server accepts it, examines the recipient's address, then looks in ("queries") the Directory Server to see which messaging server the recipient uses to store their messages. 
  • If the recipient uses this messaging server to store messages, the recipient is "local", and the server stores the message on its hard disk in the appropriate folder. 

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  • If the recipient does not use this messaging server, the recipient is "non-local", and the messaging server sends the message off to the recipient's messaging server, which will then accept it, repeat the query process, and eventually store the message.
The recipient then uses a client to access their messaging server, and retrieves the stored message.
 
 
     

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