How Stuff Works
Using an e-mail program, or client, you compose your message. Then you send it. Marshall says to think of your message as a little digital package of information. That package is sent through a cable from your computer to another computer maintained by your e-mail service provider, which is called a mail server. The mail server examines the recipient's address to decide how to route the message.
The message then travels over the Internet, arriving at the mail server of the recipient's e-mail service provider, where it is held in an electronic mailbox. When the recipient checks for new messages, their e-mail client communicates with their e-mail service provider's mail server and retrieves any new messages waiting in that electronic mailbox. In a process that typically takes less than a second—you've got mail!