01-07-2013, 04:54 PM
Email Systems
Email Systems.ppt (Size: 152 KB / Downloads: 288)
Email Basics
What is an Email – an electronic message transmitted over a network from one user to another.
Can be as simple as a few lines of text, or include attachments such as pictures or documents.
Email made up 75% of network traffic soon after the introduction of the internet.
What Makes Up An Email
The Header
Who sent the email.
To whom the mail is sent.
When the email was sent.
The email subject.
The size of the email.
The Body
Contains the message.
May also contain an attachment.
Attachments
If not embedded within the body, attachments are sent along with the email.
How Email Works
Different Architectural Models exist for constructing computer systems.
Some models include:
Peer-Peer
Pipe and Filter
Implicit Invocation
Client-Server
How Email WorksClients
Forms in which clients appear:
Application based - these are installed onto user’s machines and include Microsoft Outlook and the freely available Outlook Express and Eudora.
Web based - these appear in a web browser’s window and include Hotmail, Yahoo and Outlook web client.
Clients vary greatly in functionality, but all provide a basic level of functionality that assists the user.
Basic functions include:
Ability to create new emails.
Display and store received emails.
Hold address lists of contacts, a calendar, journal and other extra functions that help organize the user’s working day.
The client is also configured with the account information and names or IP addresses of the email servers with which it will be communicating.
What Are TCP/IP Ports
Most email servers run on a web server platform with email services installed.
Each server has one or more unique TCP/IP (transmission control protocol/internet protocol) addresses. Attached to all TCP/IP addresses are many ports that range from 0 to 65,535.
TCP/IP uses ports to allocate different jobs to different services. The server will listen for a client or application to call it on a port and direct traffic from that port to the required service.