Explanation of POP3 (Post Office Protocol version 3) and SMTP (Simple Mail Transfer Protocol).

This information was provided by Claris Corporation on 16 March 1998, and incorporated into Apple Computer's Tech Info Library.

POP3 Server Description

The POP3 (Post Office Protocol version 3) server component allows e-mail messages to be stored on the server and retrieved by e-mail client software. A POP3 server performs user authentication (checking user name and password) to prevent unauthorized access to users' mail. Each user has a unique name and password. Basically, POP3 handles only incoming mail.

For more information on the POP3 specification, see RFC 1725 available on the Internet.

SMTP Server Description

The SMTP (Simple Mail Transfer Protocol) server component handles outgoing mail requests. SMTP servers do not perform any type of user authentication, so there is no way to prevent unwanted use of an SMTP server except through the implementation of firewalls. Although this means that any user can send mail through any SMTP server, it does not mean that they can retrieve e-mail or access other users' messages. This is a limitation of the SMTP specification, not of the AppleShare IP Mail Server.

For more information on the SMTP specification, see RFC 821 available on the Internet.