Generally acknowledged as being the 'killer-app' of the Internet, e-mail is more frequently used than even the Web. As more and more people rush online, e-mail will become, even more, the ubiquitous means of communication between individuals, for all sorts of purposes, in many different spheres of activity.

E-mail has achieved a phenomenally wide user base over the last few years, which is due in part to the power and design of the Internet mail protocols that we will be examining later in this chapter. Programming with those e-mail protocols is, however, a subject that has received surprisingly little attention from the mainstream programming textbooks.

One of the secrets of e-mail's amazing success with the general public is that it hides the underlying complexities and details of transmitting and retrieving electronic mail from the end user, allowing for low maintenance and ease of use. Mobile phones and PDAs have also been tremendously successful because, like e-mail, they provide a user-friendly interface to a powerful communication paradigm. These wireless consumer devices are likely to be far more quickly and widely adopted by the largely non-technical general public in the next few years, overtaking the more powerful and complex personal computer.

The market penetration of WAP-enabled mobile phone technology will bring with it greater demand for more flexible, and powerful, mobile computing applications. Wireless e-mail functionality will be at the core of this revolution.

E-mail and WAP are fast becoming the most demanded combinations of technology by both corporations and general consumers.

Within today's e-commerce computing systems, the ability to exchange messages is an important feature, and one which will be demanded far more frequently as the functionality provided by e-mail becomes a de-facto standard, replacing the outdated fax technology for most businesses, and being fully integrated with corporate voice mail systems.

In fact, the ultimate goal for messaging technology for many organizations is a universal inbox in which voice, fax, and email can be viewed in any format by a mobile communicator device. For example voice mail, email and faxes should be viewable as email, audible like a voice mail, or sent to a nearby fax machine or printer.

In this chapter we will:

• Review the history of e-mail and the current e-mail protocol standards
• Look at Sun's JavaMail API
• Build server-side Java programs to deliver e-mail messaging features for WAP-enabled devices
• Briefly examine how to use CDO and ASP to incorporate e-mail into web applications on the Microsoft platform

Introduction to E-Mail

E-mail is an asynchronous message exchange technology. This simply means that when you send an e-mail message the recipient(s) does not have to be available at that instant to receive the mail, but may collect the message at his or her own leisure.

E-mail was one of the first applications to be used on the Internet and has shown a remarkable amount of tenacity. The protocols used to transmit and deliver e-mail have been evolving and changing over the years, and we have seen a wide variety of proprietary protocols come and go. Most of these proprietary solutions are now either obsolete or have been adapted to the open standards adopted on the Internet at large.

The idea of proprietary e-mail systems is no longer feasible in the Internet computing world - systems must interconnect to benefit from the huge installed base of Personal Computers, Macs and workstations, interactive TVs and mobile devices, linked to the Internet.

The History of Internet E-Mail

The ARPANET (Advanced Research Projects Agency Network) was created in 1969 as an experimental project to enable communication between participants in the DARPA (Defense Advanced Research Projects Agency) community. Ray Tomlinson wrote SNDMSG, the first ARPANET e-mail system, in 1972, and e-mail protocols and systems have snowballed since then.

To gain an idea of the worldwide adoption of this technology, here are some figures detailing e-mail usage (taken from NUA Internet Surveys):

• In the early 1990s, there were only 15 million e-mail accounts in the world
• There were 569 million e-mail accounts globally at year-end 1999; this figure is up 83% on the previous year
• It is predicted that there will be in excess of one billion e-mail accounts worldwide by 2002

The International Standards Organization (ISO) spent many years working on the vast and complete X.400 protocol as the de-facto standard for electronic mail.

However, whilst waiting for the final published specification, many vendors developed proprietary e-mail systems that achieved a wide deployment. The ISO e-mail standard, along with X.500, its sister standard for directory services, was simply released too late to achieve market dominance. The PC revolution was in full swing, and other, less expensive implementations such as MS Mail, Lotus Notes and cc:Mail had achieved a critical market share. Despite the vast reach of the ISO and the comprehensiveness of the enterprise (the brief was to design a complete mail specification), the standard was unable to displace the mass of e-mail systems already firmly established.

Acceptance of X.400 was further hampered by the fact that the ISO had missed some fairly vital pieces of functionality, such as the ability to asynchronously access mail messages without a permanent connection to the Internet in a way we will discuss later using the Post Office Protocol (POP3).

Nevertheless, X.400 may see some sort of renaissance as a mail backbone to transfer mail messages between mail servers, and is actually being used as a standard mail backbone protocol by several of the major vendors, including Lotus, Microsoft, IBM, and HP.

X.400 does provide:

• Good support for Binary Large Objects (BLOBS)
• Support for Electronic Data Interchange (EDI)
• Security via X.509 certificates
• Well designed connectivity of mail functionality with the X.500 Directory Service specification

We are now seeing the emergence of devices that integrate the more traditional capabilities of e-mail with the telephony features available to mobile phones, and other wireless devices. These devices are able to leverage the functionality, and familiarity, of both e-mail and wireless technologies. They are also truly portable, unlike most mail-enabled devices that have been used previously.