Wednesday, 24 July 2013

How E-mail Works

How E-mail Works

Just like airmail is sent through the air, 'e'-mail is sent through the 'e' – the 'e' in this case being
the web of electronic connections within and between the networks that make up the
Internet. When you send an e-mail from your computer, the data is sent from your computer
to an SMTP server. The SMTP server then searches for the correct POP3 server and sends your
e-mail to that server, where it waits until your intended recipient retrieves it.

E-mail Accounts

E-mail accounts are available through many different sources. You may get one through
school, through your work or through your ISP. When you get an e-mail account, you will be
given a two part e-mail address, in this form: The first part,
username identifies you on your network, differentiating you from all the other users on the
network. The second part, is used to identify your specific network. The
username must be unique within your network, just as the domain name must be unique
among all the other networks on the Internet. However, user names are not unique outside of
their networks; it is possible for two users on two different networks to share user names. For
example, if there is one user with the address, there will not be another
user on whose user name is bill. However, and are both valid e-mail addresses that can refer to different users.
One of the first things that you will do when you are setting up your e-mail is to enter your email
address into your e-mail client program. Your e-mail client is the program that you will use
to send and receive e-mails. Microsoft's Outlook Express may be the most widely known (since
it comes free with every copy of a Microsoft operating system), but there are many others
available for both Windows and Linux, including Mozilla, Eudora, Thunderbird and Pine.


After your e-mail client knows your e-mail address, it's going to need to know where to look for
incoming e-mail and where to send outgoing e-mail.
Your incoming e-mails are going to be on a computer called a POP server. The POP server –
usually named something like or – has a file on it
that is associated with your e-mail address and which contains e-mails that have been sent to
you from someone else. POP stands for post office protocol.
Your outgoing e-mails will be sent to a computer called a SMTP server. This server – named – will look at the domain name contained in the e-mail address of any
e-mails that you send, then will perform a DNS lookup to determine which POP3 server it
should send the e-mail to. SMTP stands for simple mail transfer protocol.
When you start up your e-mail client, a number of things happen:
1. the client opens up a network connection to the POP server
2. the client sends your secret password to the POP server
3. the POP server sends your incoming e-mail to your local computer
4. the client sends your outgoing e-mail to the SMTP server.
The first thing to note is that you do not send a password to the SMTP server. SMTP is an old
protocol, designed in the early days of e-mail, at a time when almost everyone on the
Internet knew each other personally. The protocol was written with the assumption that everyone who would be using it would be trustworthy, so SMTP doesn't check to ensure that
you are you. Most SMTP servers use other methods to authenticate users, but – in theory –
anyone can use any SMTP server to send e-mail.

Forged Headers.

The second thing to note is that, when you send your secret password to the POP server, you
send it in a plain-text format. It may be hidden by little asterisks on your computer screen, but
it is transmitted through the network in an easily readable format. Anyone who is monitoring
traffic on the network – using a packet sniffer, for instance – will be able to clearly see your
password. You may feel certain that your network is safe, but you have little control over what
might be happening on any other network through which your data may pass.
The third, and possibly most important thing that you need to know about your e-mails, is that
they are – just like your password – transmitted and stored in a plain-text format. It is possible
that they may be monitored any time they are transferred from the server to your computer.
This all adds up to one truth: e-mail is not a secure method of transferring information. Sure, it's
great for relaying jokes, and sending out spunkball warnings, but, if you're not comfortable
yelling something out through the window to your neighbor, then maybe you should think
twice about putting it in an e-mail.

Does that sound paranoid? Well, yeah, it is paranoid, but that doesn't necessarily make it
untrue. Much of our e-mail communications are about insignificant details. No one but you,
Bob and Alice, care about your dinner plans for next Tuesday. And, even if Carol desperately
wants to know where you and Bob and Alice are eating next Tuesday, the odds are slim that
she has a packet sniffer running on any of the networks your e-mail might pass through. But, if
a company is known to use e-mail to arrange for credit card transactions, it is not unlikely to
assume that someone has, or is trying to, set up a method to sniff those credit card numbers
out of the network traffic.

Web Mail

A second option for e-mail is to use a web based e-mail account. This will allow you to use a
web browser to check your e-mail. Since the e-mail for these accounts is normally stored on
the web e-mail server – not on your local computer – it is very convenient to use these
services from multiple computers. It is possible that your ISP will allow you to access your e-mail
through both POP and the web.

However, you must remember that web pages are cached or stored on local computers,
sometimes for significant lengths of time. If you check your e-mail through a web based
system on someone else's computer, there is a good chance that your e-mails will be
accessible to someone else who uses that computer.

Web based e-mail accounts are often free and easy to get. This means that they offer an
opportunity for you to have several identities online. You can, for instance, have one e-mail
address that you use only for friends and another that is only for relatives. This is usually
considered acceptable, as long as you are not intentionally intending to defraud anyone.

No comments:

Post a Comment