Introduction

Electronic mail (e-mail) has recently been reported to be the most widely used service on the Internet. It is no longer just a basic means of communication for use by educational, research, and government personnel. It's now a fast, convenient, and highly sophisticated messaging system. The purpose of this document is to introduce you to e-mail in general, and some of the more common e-mail applications.

E-mail has many advantages over traditional forms of communication such as postal services, telephones, and even fax machines. Since e-mail is created, transmitted, and stored entirely in electronic form, it does not require paper or pile up in landfills. It can be edited, copied, and shared with others with ease. And, unlike the postal services, there are no direct postal charges to send an e-mail message, no matter where or when you send it. Many people find it easier to respond to e-mail than conventional mail, simply because they don't like writing on paper!

E-mail is also faster than postal services and most fax machines. While not as immediate as a telephone conversation, it has its advantages over that technology as well. Unlike a request by phone, a request by e-mail can be answered at leisure. This can allow you to get all the information together and not give a hasty response. E-mail can be sent and received at any time of day or night. You don't have to worry about what time it is in Guam when you want to send a message there. There is no phone to ring and so you won't have to wake anybody up. When morning comes in Guam, your e-mail message will be waiting! Likewise, if you've been out of the office all day, your associates could still send you messages all day and you haven't missed out on anything. Hmmm. That could be a drawback!

In any case, many people all over the world and in many different situations have discovered the convenience and simplicity of communicating via e-mail. Hopefully after reading this document you will find e-mail to be an easy and effective method of communicating.

How E-mail Works - an Overview

E-mail is one of many services available on the Internet. It is functionally comparable to sending a letter through the postal services.

You create a message on a computer system by typing a message using special e-mail software. This message must be written in text only which includes all the normal 26 characters of the alphabet (both upper and lower case), plus numbers, punctuation, and other special characters. This character set is not limiting for normal communication using English, but it isn't adequate for some languages (like Chinese) and for binary data files (like pictures). However, most e-mail systems today have evolved to allow for such things as pictures by converting the binary data into encoded text files.

Once you have created a message using the e-mail software, you can send it to someone on the Internet. However, you can't just tell your computer to send the message to your friend John Doe. You have to give it a valid Internet address. A valid Internet e-mail address includes a username and the Domain name. See the section below entitled "E-mail Addresses" for a more detailed explanation of what a valid address is.

The system where you have an account will prepare your message and then transfer it over the Internet. The Internet uses the address to figure out the best route to get your message to its destination. This usually only takes a few seconds, but occasionally takes a few minutes to hours. In any case, the message will be delivered to the system where the receiver has an account and will wait until that user reads it.

The receiver will use a computer to access the message. Once the receiver has read the message it can be saved, deleted, forwarded, or even printed. The user can do whatever he/she wants with it.

E-mail Addresses

Each person who has an account on a system on the Internet has a username. Typically it's similar to their actual name or a nickname. For example, the user John Doe might have the username "jdoe" or "johndoe". That username will be unique on the system where he has an account, but not necessarily on the Internet.

The Domain name portion of the address is essentially the name of the system where the user has an account. For example, John Doe might have a student account on the system called "GROVE" at U.F. Since the GROVE system is actually a part of the entire CIRCA system, that will need to be indicated in the Domain name. So the Domain name for the GROVE system is "grove.circa.ufl.edu". Each section of the Domain name is separated by periods. This Domain could be translated as, "the machine named GROVE on the CIRCA system of the University of Florida, which is an educational institution". Domain names do not have to have four sections. Some have more and some less. However, they will all have at least two and the last section indicates what type of institution it is. Some of the most common types are educational (edu), commercial (com), military (mil), government (gov), misc. organization (org), and access providers (net).

So if John Doe has an account on GROVE, his complete e-mail address would be: "johndoe@grove.circa.ufl.edu". The "@" character can be read as "at".

Usernames are usually case-sensitive so "JohnDoe" is different from "johndoe".

Understanding E-mail Servers - POP & SMTP

The standard method of transferring e-mail over the Internet is the Simple Mail Transfer Protocol (SMTP). Each system on the Internet that acts as an e-mail server implements SMTP (and other mail protocols) to send your message on the Internet. See figure 1.

SMTP will place any outgoing messages in a queue. It then tries to forward the message from the queue to the destination system. It does this by establishing a connection with the receiving SMTP system and sends it basic information about the message. If the receiving SMTP system says it's okay, the sending system then transfers the message. The receiving system will then place the e-mail message in the receiver's "Inbox" or "Mailbox".

Post Office Protocol (POP) servers are programs running on the system where you have an account. Their function is to allow users with e-mail software running on a PC via a remote connection to receive their messages. The POP server will not let just anybody look at your mail. It has a log-in procedure with a username and password just like your regular account.

Your e-mail software will most likely allow you to input your username and password in order to log-in. Once it has logged-in, it will read all your incoming messages and present them to you at your PC. Essentially it acts as your agent by getting your messages for you and then giving them to you at your PC. See figure 2. Depending on the configuration and capabilities of the software, it may remove them from the server so that you don't have a copy on the PC and the server. Otherwise you would end up with a lot of old messages just sitting around taking up space on the server.

You normally only need to know your SMTP server and POP server Domain names if you are using software on a PC with a dial-up account to read and send mail. If you are simply using a terminal session to run e-mail software on the server, all of this is essentially transparent to you.

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