1)    E-mail (electronic mail) described as,its interchange of computer-stored

messages by telecommunication. 

2)      The model that works best for email is the Client-Server model.

3)      Clients carry out user interactions with the email server.

4)      Forms in which clients appear:

                  a)      Application based - these are installed onto user’s machines and include

Microsoft Outlook and the freely available Outlook Express and Eudora.

                 b)      Web based - these appear in a web browser’s window and include

Hotmail, Yahoo and Outlook web client.

5)      Basic functions include: (Services)

                 a)      Ability to create new emails.

                 b)      Display and store received emails.

                 c)       Hold address lists of contacts, a calendar, journal and other extra

functions that help organize the user’s working day.

                d)      The client is also configured with the account information and names or

IP addresses of the email servers with which it will be communicating.

6)      An email server is commonly a combination of processes running on a server

with a large storage capacity it comprise a list of users and rules, and the potential

to receive, send and store emails and attachments.

7)      Should process emails for months as sending, receiving and maintenance tasks

are carried out at scheduled times. The client only has to connect to the email

server when it sends and checks/receives new email.

8)      Sometimes it may be permanently connected to the server to allow access to

shared address books or calendar information – this is typical of a LAN-based email

server. 

9)      Most email servers conduct email services by running two distinguish processes

on the same machine.

10)   One process is the POP3 (Post Office protocol 3) server, which holds emails in a

queue and delivers emails to the client when they are requested.

11)   The other is the SMTP (simple mail transfer protocol) server that receives

outgoing emails from clients and sends and receives email from other SMTP

servers.

12)   These two processes are linked by an internal mail delivery mechanism that

moves mail between the POP3 and SMTP servers.

13)   When the client calls the email server to send or check for mail it connects to

the server on certain TCP/IP ports: 

                    a)      SMTP on port 25

                   b)      POP3 on port 110.

14)   MAIL PROTOCOLS

                   a)      SMTP - Simple Mail Transport Protocol is used on the internet, it is not a

transport layer protocol but is an application layer protocol.

                  b)      POP3 - Post Office Protocol version 3 is used by clients to access an

internet mail server to get mail. It is not a transport layer protocol.

                  c)       IMAP4 - Internet Mail Access Protocol version 4 is the replacement for POP3. 

                 d)      MIME – Mime (sort of Multipurpose Internet Mail Extension) is the

protocol that defines the way files are attached to SMTP messages.