填空题

One important use of Internet is communication between computer users by e-mail. E-mail (11) users to send and receive messages, text, or other information through Internet. E-mail is (12) like a mailbox: the user can send messages no matter whether the (13) is on the network or not. When a message arrives, it is stored in the e-mail address. If there is an e-mail, a signal will indicate that a message (14) to be read. Today e-mail has replaced the telephone for many messages. The user can read his message when it is (15) for him. He can read his message on the computer screen or print it out.