Chapter 1. E-Mail Services

The use of e-mail has grown significantly over the past few years. What was once considered a luxury item now is almost a necessity, especially in the corporate environment. When personal e-mail use in the home became popular, an entire new industry of Internet service providers (ISPs) was created to provide e-mail services to home Internet users.

As e-mail usage grew, so did e-mail systems. What was once a simple mainframe application suddenly became a monster application that required dedicated hardware and high-speed Internet connectivity. Often large corporations purchased expensive e-mail software packages to support the e-mail environment within the corporation. In addition to complicated server software, many e-mail packages require complicated client software so users can access their mail on servers located on the corporate network.

The increasing demand and complexity of e-mail systems brought about advancements in e-mail protocols. The Simple Mail Transfer Protocol (SMTP) was designed to efficiently transfer messages between remote computers. The Post Office Protocol (POP) and Interactive Mail Access Protocol (IMAP) were designed so that users located remotely from their mail hosts could access messages in their mailboxes.

This chapter describes the history of e-mail services and functions, outlining the functional requirements that have grown as e-mail has matured. Also, this chapter describes the many protocols and software packages used to implement e-mail on the Internet.