Email

It all started at the start of the 1970's when DARPAnet was up and running, the geeks were playing with their new toy but nobody had any practical use for the internet.  Ray Tomlinson was hacking about with a communication program and looked at the keyboard on his terminal to look for a character to use to indicate that a user was associated with a particular computer domain.  He chose the @ sign, which actually was a symbol for the word about.  Once Ray started sending himself a few of his colleagues messages with the @ sign used to indicate the location of the user it stuck and very quickly the program took off and  it's use was spread across the internet.  It was the "killer app" that served to give usefulness to the internet to people other than geeks.

There are two protocols that are required for email to work, the first is SMTP(Short message transfer protocol).  This protocol takes the email header and fishes out the destination domain ( for example gmail.com) and then sends a DNS lookup request to find the IP address of the server.  SMTP will then connect to the host (gmail.com) and ask it the username is valid.  If the host has got a username that matches then the SMTP server will transfer the email and the host (gmail.com) will store that message in the inbox of that username. [this is a little over simplified but is gives you some idea of how it works]

The user who has been sent the email will use a protocol called POP3 (post office protocol 3).  The user will supply a username and password in order to gain access to the account, there will be an unread message in the inbox.... the user may still choose to mark it as trash...

There have been several different but compatible protocols and programs to manage email and these include IMAP and Microsoft exchange server.  All of these approaches must still be able to speak to and listen to SMTP server in order to be compatible with all email on the internet but how they handle the email after that may differ.

Email clients:  There are many hundreds of thousands of email clients, these are the programs that provide a user interface for the user to interact with the email server.  You may have used Microsoft Outlook or Thunderbird or Pegasus, in essence they all do the same thing.  You are probably more familiar with a web based email client like the ones used for gmail, hotmail, yahoo or exchange.  The advantage of the web based client is that you don't need to have any software installed on the computer that you are using as long as you have  a web browser.  It will even work on your phone.

Most smartphones support push mail where the phone has a built in app that acts as the email client and checks on a regular interval with the email server over the data link on the phone to see if you have received a new email... and then notifies you that somebody loves you.

GMail

Gmail is a term that is creeping in as a replacement for e-mail for users who are using Google’s free e-mail service. GMail is special because you have 5 GB (and continually increasing) of storage space that is indexed by Google, making your e-mail easily searchable. It does, however, display adverts related to the mail you are reading – and so raises privacy concerns. Gmail now includes the ability to read and work with mail whilst offline using ‘Google Gears’. 

Phishing

Phishing is the process of sending out e-mails that appear to come from legitimate websites such as eBay, PayPal, or other banking institutions. The e-mails state that your information needs to be updated or validated and ask that you enter your username and password, after clicking a link included in the e-mail.