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How Email Works

Page 4 : Email Handling Before Sending

The email has already been prepared. Here's what happens when you click on the send button to deliver the email to your friend.

Email Packets Handling

Before the Email start the long journey, it need to do some procedures to ensure that it can arrive safely and accurately. Don't worry, the software in your PC will do it for you.

  • The email is broken up into a whole lot of same-sized packets. There's a parameter that controls the maximum-sized packet allowed in a transmission. It's usually set to somewhere around 1K bytes. Therefore, short email messages can often be handled as one packet only.
  • A header is added to each packet. Basically, the header will contain the information of the sender address, the destination address, and checking code, etc.

Take a similar example : You want to send a large wooden car model (Email) to a friend.

You know that the size of the car model exceed the size limit of postal regulation. So you buy some paper boxes of the same size (packets), probably just meet the size limit of the mailing protocol (TCP/IP) in order to save money. Then the car model is disasembly and pack into the paper boxes.

In order that all paper boxes can be sent to your friend, you stick a label (Header) to all boxes. The labels have the address of your friend. Your address is also included so your friend know who send the model or in case the model cannot be sent they can be returned to you.

The packing information is also included in the label, e.g. box 1 of 5, box 2 of 5, etc. to ensure that your friend receive all the boxes.

Sending the Email

Now, your email message is packed into a number of packets. They can start the journey right now! Firstly, the email message is transmitted by your computer's modem over standard analog telephone lines to your ISP mail server. Then the email was switching to the closest Router on the Internet. Once in the Router, the email find it's first difficulty - Woh, the world is so big, what way should I go ? While the email wondering, the Router talk to her "Don't worry, boy, I have a table that record down most of the addresses of my friends (other Routers)." The email is very happy and check with the table the destination address.

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