Incoming and outgoing email can be automatically archived based on, say, the sender's or recipient's address. It is a simple matter to forward messages to third parties. Messages can be bulk mailed to many people as easily as to a single person. In addition, several services are being tried by which a message can be sent to a person who cannot receive email by sending the message to a nearby postal station where the message is printed and then delivered by conventional means. This system would reduce international delivery times from possibly weeks to a day or less.
Email also raises a problem about confidentiality.
Since an email message may pass through several intermediate systems and possibly traverse hundreds or thousands of miles through cables or satellite channels over which the sender has no control, securing the communication medium is not feasible so encryption must be used. Thus, the sender and the recipient of the message must have the same key. One cannot email the key to the other since the communication may be intercepted and a third party gain access to the key, and thus to any messages encrypted with the key. One solution to the problem is to use public key encryption , discussed in Section 6.4 .