E-Mail Security
Electronic mail systems, commonly called ‘e-mail’, are becoming the emthod of choice for
communication. With the advent of the internet, e-mail has become the most ubiquitous, most
well-known, easy to use and easily available application. E-mail (electronic mail) is the exchange
of computer-stored messages by telecommunication. 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.
Global electronic Mail usage Scenario
HOW E-MAIL WORKS
The main components of an e-mail system that facilitate sending and receiving of e-mails on
Internet are:
An e-mail client
An e-mail server (SMTP server)
POP and IMAP servers.
An Email Client
If you use e-mails for online communication the you would definitely be using an e-mail client. An e-mail
client provides you with the following capabilities :
Provides a list of messages that people have sent to you. Each entry in the list contains the name of
sender, a subject, a few words from the message body and the time/date on which it was received.
Provides the ability to read a complete message, reply to it or forward it to other people.
Provides the ability to compose a new message and send it to the desired recipients.
Delete a message.
The e-mail clients could be standalone (like Microsoft Outlook, Pegasus etc) or could be web based (like
gmail, yahoo etc).
An Email Server
Whenever you send a message from your e-mail client, it goes to an e-mail server. The e-mail server
manages the messages received by it. It forwards the message to a POP or IMAP service if the message is
to be sent to a recipient on the same subnet else it follows the standard procedure to send the message over
Internet to the destined person. The server looks at the e-mail address, then forwards it to the recipient's
mail server, where it's stored until the addressee retrieves it.SMTP servers are widely used as e-mail servers
all over the internet. An SMTP server is also known as Mail Transfer Agent (MTA).
Step by Step Working:
1. An e-mail client like Gmail, yahoo, outlook etc is used to create or reply to an e-mail.
2. Once the e-mail is drafted successfully, it is sent using the e-mail client.
3. This e-mail first goes to the SMTP server (also known as MTA (Mail transfer agent) ) to which the e-
mail client is connected.
4. The e-mail server looks out for the recipients address. The address is of the
form<name>@domain.com
5. The e-mail server first uses the DNS technique to resolve the domain name into a valid IP address.
6. Next it sends the e-mail to to this IP address over the Internet.
7. Now the e-mail traverses over the Internet in a series of IP packets and reaches the destination
SMTP server or the MTA.
8. This server collects all the e-mails and places them to appropriate location so that these are
accessible to your e-mail clients through POP or IMAP services.
