Programming Internet Email

Chapter 10. The Post Office Protocol

In this chapter:

• Using POP

• POP Commands

• POP Sessions

The Post Office Protocol (POP) is the older and simpler of the Internet’s two mechanisms for retrieving electronic mail from a remote server. The other, the Internet Message Access Protocol (IMAP) is discussed in Chapter 11, The Internet Message Access Protocol. POP and IMAP are both client/server systems that implement the concept of mail retrieval agents, as described in Chapter 1, Electronic Mail on the Internet.

POP is the most mature of these two mechanisms. The current version of POP is Version 3 (POP3), which is an Internet standard and has been assigned a designation of STD 53. IMAP, by comparison, is still a proposed standard.

This chapter describes POP3 in detail and provides information necessary to implement both POP servers and clients. Several enhancements have been proposed to extend POP’s security options, and these are also discussed.