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Network Connection

By Dr. Philip Baczewski, Associate Director of Academic Computing

Back to the Basics: E-mail

What exactly is E-mail? It is, of course, a convenient shortening of "electronic mail." In searching for a definition, however, I found that there isn't a very good definition of E-mail published on the Web. Take, for example, the definition of E-mail provided by the "Computer User High-Tech Dictionary" :

"A service that sends messages on computers via local or global networks."

This is an awfully broad definition, which could include Web pages, instant messaging, and practically any other activity supported by the Internet. So perhaps Merriam-Webster's online dictionary will do better:

1 : a means or system for transmitting messages electronically (as between terminals linked by telephone lines or microwave relays).

That's a little more specific, but still not too helpful. In both definitions, the word "message" does not help narrow the meaning of E-mail, since a message can be spoken, written, symbolically represented, or even drawn. Still, if you take "terminal" in this context to mean a computer-connected console used to enter text and commands to a computer interface, then perhaps we're getting a bit closer to a more specific definition of E-mail.

This leads us to Philip Baczewski's definition of E-mail, a definition I think I'm qualified to make since I have been using, implementing, and supporting E-mail services for the last 20 years or so:

E-mail: written messages automatically transmitted via computer systems and computer networks in a standardized format allowing communication between disparate systems and diverse locations in geography and time.

An even more specific definition of E-mail can be understood by examining the key parts of the above.

Written messages

E-mail systems were designed and developed to transmit text. Text, in computer jargon, is representations of alpha-numeric characters like the ones that form the words you are now reading. Because characters take only small amounts of computer space to represent, text is still one of the fastest and most efficient ways of transmitting information and ideas via computer networks. Text is also still one of the most efficient ways to transmit human ideas and information. While E-mail can include various kinds of attachments, the message portion is text, even if that text includes HTML commands to make the words look pretty in Web-based E-mail interfaces. In fact, treating E-mail as something other than text can lead to problems such as the transmission of viruses or security breaches on a personal computer.

In recent years, the term E-mail virus has come into the jargon as the result of incidents such as the "Melissa" Virus. The Melissa virus would more accurately be characterized as a Microsoft virus, since it's method of propagation exploited features of Microsoft's software. The transmission was via E-mail, but the activation was caused by opening an E-mail attachment. The E-mail attachment would then execute computer commands via the MS Word program and replicate itself by using Microsoft's E-mail implementation which was (and still is) tightly integrated with it's office applications. Those using Microsoft's E-mail program were more prone to accept and propagate the virus, because that program would, by default, automatically open and display the attachment and execute its program commands without an explicit action by the person receiving the E-mail.

By going beyond the simple task of displaying the E-mail text message, Microsoft's software create a situation which allowed surreptitious control over a remote (maybe your) PC. This remains true if your E-mail program interprets the text content as commands to be acted upon. For example, using a Web browser as an E-mail program or even a Web-based E-mail program and allowing incoming messages to be interpreted as HTML content opens you up to anything that can be done via HTML. This could be just annoying behavior like displaying pop-up ads, but could be as sinister as using Web scripting to change settings or capture information in your browser. Treating E-mail as something other than a written message is just not a good idea.

Automatically Transmitted

The transmission of E-mail happens behind the scenes. You don't have to provide your E-mail program with instructions on how to deliver your message. You just supply the address and various computer systems between you and the destination take care of the routing. Furthermore, the process is automated. There isn't some great room where E-mail is sorted and nudged into different cubbyholes by human workers. Instead, the routing methodology is defined by entries in Domain Name Services (DNS) tables which tell what computer is able to accept mail for a particular address.

For example, you might send E-mail to Your E-mail program will usually use a local relay host computer, usually refereed to as your outgoing mail server. That computer will use DNS to find out what Internet address accepts mail for "" and will use Internet SMTP (Simple Mail Transfer Protocol) to communicate with the remote system and transfer your message. Once "'s" mail server accepts your message it will usually forward it to a destination mail server such as "" which will deliver that message to "Fred's" mailbox. All of that activity is done by computer programs which operate usually without human intervention.

The downside to automation is that there is not guarantee that E-mail will be able to be delivered. OK, just in case you didn't hear that I said, THERE IS NO GUARANTEE THAT E-MAIL WILL BE ABLE TO BE DELIVERED! E-mail server programs actually try pretty hard to deliver mail. They will hold a message if communication can't be established with the remote server. They will retry for hours and sometime days to establish a connection with the remote server. If all else fails, however, the message is returned to the sender with an indication of what kind of condition or error prevented delivery.

Another side-effect of automation is that unscrupulous individuals can take advantage of the E-mail network to send unsolicited E-mail that advertises some business (or scam) without revealing who the actual sender was. In case you don't recognize the description we usually call such unsolicited E-mail "spam." Because spammers are trying to hide their identity, they often make use of E-mail servers which are not registered in DNS or not fully registered in DNS. In order to guard against spam, most current E-mail delivery programs will refuse connections from Internet addresses that cannot be definitively identified via DNS. Once again, we see that E-mail delivery is not guaranteed, although in this case the blame can be laid at the feet of those who would abuse the openness of the Internet for their own selfish interests.

Computer Systems and Computer Networks

Many people don't realize that E-mail existed before computer networks were standard and world-wide. Back in the days when most computers were large-scale multi-user systems, E-mail was used to communicate with others who had login accounts on the same computer. As computers were able to communicate over networks, E-mail routing was extended to be able to travel over those networks. Still, most people using E-mail were doing so on those large multi-user systems.

Fifteen years ago, a large volume of E-mail (and almost all mail between colleges and universities) was carried on a network called BITNET which linked primarily IBM Mainframes and DEC VAX systems. DEC (Digital Equipment Corporation) is extinct, having been absorbed by Compaq which itself is trying to be absorbed by Hewlett-Packard. IBM mainframes are almost extinct, although some old systems still find obscure habitat in places such as university psychology departments.

Today's Internet ingenues think that E-mail is the entirely the province of Web pages. Hotmail, Yahoo, and even EagleMail make their presence felt in the browser window, turning the Web browser into the universal Internet tool for the present generation of Internet habitues. Anyone who's been around the Internet for more than 10 years or so remembers that it wasn't always so. In the brief paleosilicate history of the Internet, we can define an epochal separation laid out around the pre- or post-mosaic dividing line (that's the Netscape progenitor, if you didn't know).

E-mail is now mostly viewed on personal computers, but soon will be just as common on PDAs and cellular phones. PDAs and cell phones are just small computer systems that can be connected via electronic networks. What will remain constant with E-mail is that the message, no matter on what computer system or what network it is transmitted, will still primarily consist of text. If you don't believe that, then ask yourself why companies are scrambling to be able to deliver E-mail to cell phones when cell phones already have the capability to deliver v-mail.

Standardized Format -- Disparate Systems

E-mail works because the whole world has agreed upon some standards. The computer representation of text characters is an accepted standard. The way an E-mail addressing header is created is an accepted standard. The manner in which Internet mail transfer programs talk to each other is a standard. The way information travels across the Internet is a standard. These standards were not imposed by some grand inventor of the Internet. Instead they developed over time through a process of proposal, testing and evaluation, adoption of the useful ones, and the discontinuation of the less useful ones. The Internet is definitely a study in evolution.

Because there are accepted standards, any computer system can participate as long as it can implement those standards. That means you can send an E-mail from a PC to a Macintosh or from a PDA to a mainframe. E-mail is useful because the text and, more importantly, the ideas that the text represents can be transmitted and received on the most disparate collection of computer systems we've ever seen.

Diverse Locations in Geography and Time

As electronic networks become increasingly extended, the reach of E-mail throughout the world and in space increases. Did I say "space?" Yes, indeed. NASA Shuttle astronauts receive E-mail on laptops that travel with them to orbit. The reach of E-mail may be now greater than postal mail ever has been. We readily accept that geographical distance is no barrier to E-mail.

Locations in time are a bit trickier. E-mail is and always will be "out of time" communication. That doesn't mean that you only send it when your are out of time and can't write a letter (Webster: letter 2 a : a direct or personal written or printed message addressed to a person or organization). No, instead it means that E-mail communication occurs outside a specific context of time. In spite of the fact that there are occasional delivery problems, we've come to expect that E-mail delivery will be fast if not instantaneous. However, as the sender of E-mail, you have no control over when the recipient will read it. This is why you cannot rely on E-mail for broadcast messages of an urgent nature.

Some might see the lack of a time context for E-mail as a weakness, however, it is actually a strength of E-mail. By releasing the communication process from the constraints of two or more individuals being available at the same time (not to mention the same place), the communication process can be made more efficient by allowing those involved to participate when their own schedules allow. While it is polite to promptly answer E-mail directed to you personally, it is not always possible. In most cases the communication time frame will allow for a schedule that is not predetermined. By the way, if you do have a time-critical communication requirement, I suggest picking up the phone.

E-mail defined?

The one word implicit in the above discussion but not explicitly discussed is communication. E-mail, if nothing else, enables communication in an automated and, for the most part, efficient manner that could not be achieved via a human-delivered paper-based communication process. E-mail is written communication. If we develop a different paradigm in the future which does not use written communication, then it won't be E-mail. Somehow, I don't think that the power of thousands of years of written communication will be easily replaced soon. Have we finally defined E-mail? I think we're getting closer.