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The book Postfix talks about configuring the Postfix mail server to deliver to Maildirs, for the Courier IMAP server.
Step-by-step instructions w/ screenshots for getting Mozilla 1.2.1, Outlook 2000, and Outlook Express 6 to work with the Courier IMAP server.
Courier-IMAP + Maildrop + QMail with Virtual Domains HOWTO - self explanatory.
Install and Test Qmail with POP, IMAP and WebMail - a step by step tutorial on setting up a turn-key mail server.
http://www.gallowglass.org - how to setup your own private CA and then generate signed SSL certs for POP and IMAP over SSL.
Qmail FreeBSD toaster - another step by step tutorial, this one is based on FreeBSD.
Qmail VMailMgr and Courier-IMAP HOWTO - extensive documentation on integrating the Courier IMAP server with the Qmail mail server and the VMailMgr virtual domain manager.
A patch to use DRAC with the Courier IMAP server is available at http://aelyn.hell-city.org/courier-imap-popd-drac.patch.
SecurityFocus's article titled "Clear Text Communication: Slaying the Beast Part II" talks about general issues concerning E-mail and security. the Courier IMAP server is briefly mentioned in this article.
A patch that logs additional accounting information to syslog: ftp://ftp.aerasec.de/pub/linux/courier-imap/.