2. Email


E-mail (electronic mail) is the exchange of computer-stored messages by telecommunication. (Some publications spell it email; we prefer the currently more established spelling of e-mail.) E-mail messages are usually encoded in ASCII text. 

However, you can also send non-text files, such as graphic images and sound files, as attachments sent in binary streams. 

E-mail was one of the first uses of the Internet and is still the most popular use. A large percentage of the total traffic over the Internet is e-mail. E-mail can also be exchanged between online service provider users and in networks other than the Internet, both public and private.


Short for electronic mail, e-mail or email is information stored on a computer that is exchanged between two users over telecommunications. More plainly, e-mail is a message that may contain text, files, images, or other attachments sent through a network to a specified individual or group of individuals. The first e-mail was sent by Ray Tomlinson in 1971. By 1996, more electronic mail was being sent than postal mail.

There are a number of advantages of e-mail and the usage of e-mail versus postal mail. Some of the main advantages are listed below.

  • Free delivery - Sending an e-mail is virtually free, outside the cost of Internet service. There is no need to buy a postage stamp to send a letter.
  • Global delivery - E-mail can be sent to nearly anywhere around the world, to any country.
  • Instant delivery - An e-mail can be instantly sent and received by the recipient over the Internet.
  • File attachment - An e-mail can include one or more file attachments, allowing a person to send documents, pictures, or other files with an e-mail.
  • Long-term storage - E-mails are stored electronically, which allows for storage and archival over long periods of time.
  • Environmentally friendly - Sending an e-mail does not require paper, cardboard, or packing tape, conserving paper resources.





imap vs pop - what do they do?


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If you've read How Web Servers Work, then you know that machines on the Internet can run software applications that act as servers. There are Web servers, FTP servers, telnet servers and e-mail servers running on millions of machines on the Internet right now. These applications run all the time on the server machine and they listen to specific ports, waiting for people or programs to attach to the port. The simplest possible e-mail server would work something like this:


As other people sent mail to mbrain, the server would simply append those messages to the bottom of the file in the order that they arrived. The text file would accumulate a series of five or 10 messages, and eventually I would log in to read them. When I wanted to look at my e-mail, my e-mail client would connect to the server machine. In the simplest possible system, it would:

  1. Ask the server to send a copy of the MBRAIN.TXT file
  2. Ask the server to erase and reset the MBRAIN.TXT file
  3. Save the MBRAIN.TXT file on my local machine
  4. Parse the file into the separate messages (using the word "From:" as the separator)
  5. Show me all of the message headers in a list


When I double-clicked on a message header, it would find that message in the text file and show me its body.


Whenever you send a piece of e-mail, your e-mail client interacts with the SMTP server to handle the sending. The SMTP server on your host may have conversations with other SMTP servers to deliver the e-mail.

Let's assume that I want to send a piece of e-mail. My e-mail ID is brain, and I have my account on howstuffworks.com. I want to send e-mail to [email protected]. I am using a stand-alone e-mail client like Outlook Express.

Student Activity
  • Explain the difference between how gmail or hotmail deals with emails and how a mail client like outlook deals with an email
  • Define the following terms including what each acronym actually stands for:
    • Email
    • POP3
    • SMTP
    • IMAP4
  • What is the advantage of POP3 over IMAP4 ?
  • What are 2 advantages of IMAP4 over POP3 ?
  • How does SMTP differ from both IMAP4 and POP3
  • Given the following email address 
    [email protected] 
    try to describe the various parts of this email and how they are used to locate where the email should be sent. Try to be as technical as possible.
  • Bonus chocolate if you can identify the actual physical location of the mail server.
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