Chapter 1 explained that POP and IMAP are protocols that deal with how users retrieve their email messages from message stores. Postfix is a mail transfer agent and does not implement POP or IMAP. This chapter looks at how Postfix delivers messages and how they are read by POP/IMAP servers. There are many POP/IMAP servers available, and the information presented here should be applicable to any standards-conforming server. The last part of this chapter deals with configuring Postfix to work with the Cyrus IMAP server. Before we look at local delivery, we’ll first discuss more broadly the different delivery transports Postfix uses. Transports other than local are discussed in subsequent chapters.