Courier is a suite of programs and includes a full-fledged MTA. This book assumes that the MTA used is Postfix. It is important that only the POP3 and IMAP components of Courier are installed and configured—an e-mail system would be very unstable if there were two MTAs operating at once.
Note
The term "Courier" is often used to refer to the complete suite of Courier software, including the MTA. Courier-IMAP is normally used to refer to the IMAP and POP3 portions of the server. The Courier Authentication Library is another Courier module that is required by Courier-IMAP. Ensure that you install only the Courier Authentication Library and Courier-IMAP.
There are a couple of ways to install Courier-IMAP. Courier-IMAP Redhat Package Managers (RPMs) for several different distributions of Linux are available. These will either be available from the manufacturer of the distribution, or may have been built by a third party, typically an enthusiast or developer...