Email (electronic mail) is a form of instant message delivery. You type a message, address it, and send it to the recipient. We use email daily, but we usually do not understand how it works.

Email History

The first versions of electronic mail date back to the 1960's, based on mainframe computers. Back then, there would typically be one large computer, and users would access them from "dumb terminals" (a monitor and keyboard), sometimes remotely. Messages could be shared between different users on the same computer.

Shortly after the Internet was created, Ray Tomlinson made a network-based email system, using the "at mark," @, to separate the name of the person and the name of the computer.

Just as the spreadsheet program VisiCalc would later become the killer app which made PCs commonplace, email was also considered a killer app, making use of the Internet more popular.

How Does Email Work?

Email is actually two systems: outgoing and incoming email. The two systems are, of course, linked, but different protocols and servers are used for each system.

Outgoing mail is sent using an outgoing mail server, using the SMTP protocol. SMTP servers are like public mailboxes, some allowing almost any sender to use them. SMTP, or outgoing mail servers usually have an address such as smtp.domain.com or the more general mail.domain.com.

Incoming mail is delivered by an incoming mail server, usually using the POP or IMAP protocols. These servers, more like home mailboxes, are the specific location for email accounts; whenever email addressed to a specific account is sent, it is received by the incoming mail server and is stored there until the user accesses them. Incoming mail servers usually have an address such as pop.domain.com, imap.domain.com, or the more general mail.domain.com.

When an email is sent, it goes to an outgoing (SMTP) server. It then locates the destination (incoming) server at the domain name in the address, and send it to that server. The incoming server then holds the email until the account owner logs in and check their mail. The account user might use the POP or IMAP protocols to access the email.

Protocol and server setup in an email client
Protocol and server setup in an email client

What Is the Difference between POP and IMAP?

From your perspective, the differences may not be very important. For example, POP accounts are simpler, and can only allow one user to connect to the maibox at one time. IMAP is more complex, and allows for multiple users to connect at the same time.

There are a few significant differences, however. The POP protocol downloads the email from the server and saves it on the user's computer, using an email client program, such as Outlook or Apple's Mail app. The server mostly just acts as a temporary storage area.

By default, POP will erase the message from the server when it is downloaded, so it is permanently stored only on the user's computer. This has some advantages, such as quick offline access and searching, but it means that you must always have access to that one computer.

Deleting mail from the server is not required, however; the email can be left on the server for a set period of time before erasure, or never erased from the server at all. This could allow access from another computer, but it would require having a client email app and downloading the email multiple times. If you change the status of a downloaded email on one machine, it will not change on any other machine.

The IMAP protocol, in comparison, leaves the email on the server. Folders can be created to organize mail, and mail can be tagged as "read," "unread," "flagged," or something else. The account's mail can be searched using the IMAP server. In short, it is like having the mail program on the server instead of on your computer. A big advantage is that you can log into the email account from any computer and access all of your mail; any changes you make will be visible on any other computer which logs in.

Client Mail and Webmail

An email client program is a program located on a user's computer which connects to an incoming email server to collect mail using either the POP or IMAP protocol. Typically, the client will store the email locally, on the user's computer. If it is using the POP protocol, it might erase the email from the server.

Webmail uses the IMAP protocol and allows account owners to access their email using a browser interface. The email stays on the server, and can be accessed from any computer connected to the Internet. Most webmail services include the ability to download mail to a client program in addition, using the POP or IMAP protocols.

Webmail began to appear in the mid-1990's as a free service, provided by various companies. Hotmail, now called Outlook, began in 1996; Yahoo Mail in 1997; Gmail in 2004.

Account Full: Delete Email!

A major problem with webmail for the first decade or so was storage capacity. Even as late as 2004, most webmail accounts had a storage limit of 2MB to 4MB. One could get a 10MB or larger account, but it usually cost an annual fee.

As you might imagine, webmail storage could very easily fill up. When it did, the account simply stopped working, and people trying to send mail to it would get error messages. As a result, users had to constantly watch their email storage and delete messages on a regular basis. If you sent someone a large attachment, it could make their email account stop!

This changed in 2004, when Gmail came out and offered 1GB of storage space to all users. Although it was an invitation-only service at first, it quickly became popular, and soon was made fully public. Other services soon began to offer similarly large storage amounts. Currently, Gmail offers 15GB of storage to normal users, and 30GB to educational users.

Pros and Cons

Webmail Advantages:

  • can be accessed from any computer or mobile device
  • reliable storage; data loss rare
  • does not take up space on your devices
  • it is free, easy to set up, and easy to use
  • usually allows client access as well

Webmail Disadvantages:

  • you must be connected to the Internet to use it
  • access and use is slower than with a client app
  • usually has advertisements, some based on your email content
  • can only check email within its own system; Gmail cannot check Hotmail accounts
  • can only search email within its own system

Client Mail Advantages:

  • it is very fast
  • can check multiple accounts all at once, including webmail accounts
  • no browser login required; can run all the time and alert you to emails as they arrive
  • can quickly search all email stored in all accounts in one search
  • storage is limited only by your local storage
  • your email address can more easily use your own domain name
  • can browse, search, and compose email when not connected to the Internet

Client Mail Disadvantages:

  • all mail is stored on a single computer
  • the computer could be damaged or lost; without backup, all emails could be lost
  • accounts can be hard to set up, and connection problems can be difficult to repair
  • Some ISPs block outgoing client email unless a special outgoing server is used, meaning that a portable computer might have to change SMTP servers a few times a day.


When you send an email, you often will want to include a file or a set of files. These are sent as attachments. Every email setup should have an option for attachments. Usually, you click a button, are asked to select a file using a navigation dialog box, and then you attach the file. Using an email client, you can usually drag and drop icons directly into the "compose email" window, or else copy and paste objects directly; this is usually not possible using web mail.

Attachments can either be viewed "inline" or separately. "Inline" attachments appear within the email text, either as photographs, PDF files, or icons which launch documents. Inline attachments can often be dragged and dropped onto the Desktop or into folders for saving.

Beware of Malware! Attachments can be an attack on your computer. Especially using Windows, you must never open an attachment unless you are CERTAIN that it is safe. Even if the email seems to come from a friend, you must be VERY cautious.

Know Your Filename Extensions! Look at the filename extension for the attachment. If the extension is .exe, .zip, .bat, .vbs, .pif, or .src, you should be especially careful, although other extensions can be malware also.

Only Open Safe Attachments! How do you know if it's safe?

First, it must be EXPECTED. In other words, the sender told you they would send it. If you receive an attachment that you did not know about previously, then it is probably a virus.

Second, it should be in a specific email—that is, the email message must have a message clearly written to you, and should make reference to a specific event or project the attachment is related to. DO NOT open attachments where the message just says "look at this!" or "very funny!" or "photos from the party." The message must be specific, for example, "Luis: This is the PDF of the schedule that you asked for two days ago at the meeting."

A very common form of malware received by email will open a victim's address book and send a copy to everyone on the list. The recipients, seeing the email as coming from a friend, will more often open the attachment.

It is important to know filename extensions! When you get an email, sometimes it has attachments. These attachments often contain malware (e.g., viruses), especially when they have certain filename extensions.

Filename extensions you should be very cautious about opening include:

  • .exe
  • .zip
  • .scr
  • .bat
  • .pif

IMPORTANT: you must remember that email is usually NOT very secure, and parts of it can be easily faked. If your email says it was sent from obama@whitehouse.gov, don't believe it. I have received spam email which says I sent it, or has an account name which does not even exist.

Similarly, other elements of an email can be faked. For example, you might see a link which seems to send you to an official site, but in fact, it sends you to a fake site. For example, if you click on this link which says http://cps100.lcjapan.com, you will be taken to a different site. Sometimes, hovering the cursor over a link, without clicking on it, will reveal the actual address.

a scam email with a fake link


Spam is any email which you do not want to receive, primarily advertisements and attempts to steal money from you. Perhaps 90% or more of all email is estimated to be spam (some estimates are as high as 97%). About 80% of spam is sent by computers owned by regular poeople which have been infected by malware and turned into "Zombie computers." About 80% of all spam advertises drugs. About 80% of spam is sent by just 200 spammers. Some people (usually spam advertisers) define spam as only harmful emails, claiming that spam advertising is a necessary part of business.

You might have run into spam before, although recently spam filters have become good enough that many people get hardly any. But spam is, unfortunately, a fact of life on the Internet. How do you avoid it?

(1) Spam Filters. This is usually included automatically in email setups; some are better than others. Some filters "learn" what is spam after you mark it as such. Others learn from general spam identification. Spam filters will usually let through email which is sent from anyone on your address book—but they will usually mark as spam email from someone you have never received email from before. So, it's a good idea to check your spam folder from time to time, and make sure no "real" email got sent there by mistake.

(2) Use "Junk" Accounts for "Signing Up" or "Registering." So many sites on the web require you to enter an email address. Want to join a forum? Enter your email address. Want to use this cool web-based service? Email address, please. You usually cannot enter a fake address, because they will send you an email and require you to follow a link in the email to complete the registration. However, most of these sites want the email address for a reason: so they can sell the addresses and make money. You get spam.

So, what can you do? Easy: create a junk account. Accounts from GMail, Hotmail, and Yahoo are free, so make one up just for this purpose. Make an account such as "luissignup@gmail.com" and don't bother to log in except when you need to see the confirmation email. If you do this, then most of the spam that would normally attack your main account gets sent here instead.

If that's too hard, try a cool service: 10minutemail.com, which creates an email account for you to use for ten minutes, usually enough time to sign up for something and get the email you must respond to.

(3) Don't Publish Your Main Address on the Internet. Don't write your email address on a web page, or even on a file on a web site. Do not include it in forums, even private ones. Spammers have automated programs which search every file they find for email addresses.

To test this, I created a "virgin" email account which was never used before. No one knew the address. I then put the address up on my blog, but I disguised it: I made the text color the same as the background color. As a result, it was there, but it was "invisible" to humans. Within a few days, I started getting spam at the address.

If you absolutely MUST publish an address for some reason, try to spell it out in a way that automated programs won't catch. For example, if your address is "myname@domain.com", then spell it "myname followed by an at-mark and then domain-dot-com" or some other way that humans can understand, but software probably cannot.

(4) Never Answer Spam. No matter what, never reply to a spam email. If possible, don't even look at it, but you should never, for any reason, reply to it. Doing so will alert the spammers that your email account is active and you read the spam that comes in.

When spammers send spam, they know that most of they addresses they have are not active. The thing is, they don't know which ones. The most valuable thing to a spammer is an email address they know is in use. Better, if the person actually opens spam email. Or best, someone who is foolish enough to answer the spam email.

Many spam emails include an "opt out" message. They claim that you "requested" or "signed up for" the spam, but if you don't want to get more spam, then click the link they give and request to stop the spam. DON'T DO IT. It's almost always a trick to see if you are reading their email and are foolish enough to fall for their trick.

I tested this as well: I went to several such "opt out" sites and entered another "virgin" email account. Again, within days, spam started pouring in.

(5) And, of course, NEVER BUY ANYTHING from a spammer. NEVER.

(6) Turn off HTML graphics. Some spam includes pictures. Some of these pictures are not in the email; instead, they are on the spammer's web site. The email has HTML code which tells your email program to go to the spammer's web site, get the image, and display it in the email message. The problem: if this happens, then the spammer knows that you looked at the email! They can see which address was used, and they will start sending much more spam to that address.

To turn off HTML graphics, go into the "Settings" ("preferences," or "options") of your email program/web page and try to find the option for HTML images. In LCJ Mail, go to "Settings," click on "General," and under "External Content," set it to "Ask before displaying external content."

(7) Protect Others from Spam: Be Considerate. Years ago, a cousin of mine signed me up for a service he thought I would like. It turned out that they were spammers, and I started getting lots of spam as a result. NEVER enter another person's email address anywhere without their express permission. If you think they will like something, then tell them directly.

Many web sites have a "Tell a Friend" option. Don't use it. Once, a friend sent me such a notce through a popular news web site, for an article about a new electronic watch. Within minutes after I got his email, I started getting spam for similar watches. if you see a news story or other web content you think they will enjoy, then copy the URL, and send your friend an email directly, pasting the URL into the email.

If you follow these rules, then you have a good chance of avoiding the worst of the spam. It is sometimes impossible to avoid spam completely, but you can do it for years. One teacher at LCJ used email without any spam filter, and for years had no spam. But then suddenly, the teacher started to receive so much spam that they had to abandon their account.

Terms to Know

incoming emailemail which is sent to you; you can access it using the POP or IMAP protocols, or by your web mail account
outgoing emailUses an SMTP server; it can be any SMTP server so long as (1) the server allows any connections, and (2) your email app/account allows you to set the SMTP server.
web mailemail which is accessed via a web page (many also allow client access), such as GMail, Yahoo Mail, and Hotmail
email clientan application on a computer which manages one or more email accounts using the POP or IMAP protocols
POPan incoming email protocol which allows a client to receive email; usually the email is kept on the client and the email on the server is regularly erased
IMAPan incoming email protocol which allows a client to receive email; usually the email is kept on the server and the email on the client app is considered temporary
SMTPthe protocol for sending email; this may be different from the POP and IMAP server domains
attachmentsa file sent along with an email
spamemail which you do not want to receive, primarily advertisements and attempts to steal money from you.

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