The header information contains requisite forwarding addresses and return addresses information that is required to complete the transaction. The e-mail address is made up of two parts. Electronic mail traditionally contains simple text. However, other information in the form of formatted documents, spreadsheets, pictures, sounds and video can as well be transmitted or included in a single message that is supported by the network interface protocols at both ends.
Electronic mail is a 'store and forward' system.
The incoming messages are held for you and relayed to you on your command. However, electronic mail does not have the same protection as the postal mail. The postal mail is protected by the U.S. Postal laws, while the protection of electronic mail is governed by the individual computer system administrators. They will continue to grow and become one of the primary means of communications globally. The transaction is generally accomplished between a desktop system connected to a network called the client, and the other computer system called the host connected to the Internet Network where the files are located.