Host computers, or servers, on the global Internet are all linked to one another, mainly by telephone wires. Each server has a unique address on the Internet. You can think of this address as being like the zip-code of a city. As an individual with an Internet account, you also receive a unique address, your user name, which is like your street address. Combine your unique address with the server's address and you have a mailing address to send and receive e-mail.
Individuals can dial from their phone line via a modem into an Internet server in their community.
Once connected, the user can send messages to anyone in the world who has a connection. Even if you use the Internet to send an e-mail message to Timbuktu, you won't be charged long distance telephone rates. E-Mail is not limited to the Internet. Companies, small computer networks and schools can receive Internet e-mail through something called a gateway. You can also subscribe to electronic mailing lists on the Internet and have documents about certain topics automatically sent to your e-mail address.