Technology Reference Guide

	Technology Reference Guide 5. Network Applications C. Electronic Mail

What is it?
Electronic mail is an application that lets users send messages and transfer files with each other. E-mail systems were available before the advent of the PC LAN, and were implemented on host systems between terminal-attached users. Examples of this are IBMs PROFS, and Digitals DecMail. Simple e-mail services have also been incorporated into host operating systems, such as UNIX. Electronic mail standards have been developed which are defined in the CCITT X.400 standard. Adherence to this standard allows mail systems from different vendors to interact. Within the context of the PC LAN, e-mail has evolved in ways that capitalize on the capabilities of this architecture. This type of e-mail will form the basis of our discussion.

What does it do?

There are various components that make up a PC-based e-mail system. The most visible is the user (mail client) agent. This runs on the local workstation, although it is often stored on a network drive. It provides the mechanism that retrieves and stores the messages for view. It enables the user to attach, detach, and view files. It provides a means of organizing and managing messages through folders and wastebaskets. It may include the ability to set up personal mailing lists, set message priorities, and other features.

Another component of an e-mail system is the centralized mail engine called the post office. It generally runs on a server, either a file server or a dedicated e-mail server, and provides the intelligence to store and forward messages. It incorporates the administrative utilities needed to manage the e-mail system, and is concerned with routing messages to the appropriate locations based on address. In conjunction with this, a directory service is necessary to translate the e-mail addresses into information that can be used to get the message to the right network, right server, and right directory so the recipient can read it. These directories may be local or global depending on whether the scope of the e-mail system is the local area network, or an internetwork. E-mail routers may be necessary to pass messages between networks, or wide-area connections. Taken together these components are called the message handling system (MHS).

To enable connections between dissimilar e-mail systems, e-mail gateways are sometimes needed. These may be used if the enterprise has both host-based and LAN-based e-mail systems, or several incompatible LAN-based systems.

How is it used?
From its humble beginnings as a way of sending short unformatted text messages between terminal users, e-mail has evolved into a powerful way to share information between local workgroups, as well as geographically dispersed users. It has all but obsoleted memo distribution, and allows users to transmit and receive complex files, such as formatted documents, spreadsheets, and graphics. It greatly simplifies the process of distributing information among large groups of users, and has been credited with influencing the change in corporate structures from the traditional hierarchical pyramid, to the flatter, more interactive structures typical of progressive modern companies.

Where do I get more information?
Contact your local CBV Office.