Linked by Jon Jensen on Tue 26th Aug 2008 02:53 UTC, submitted by Ryan Masters
The Book of IMAP: Building a Mail Server with Courier and Cyrus, by Peer Heinlein and Peer Hartleben, is a quality resource for any serious mail administrator. The approach taken is direct, but at the same time it's very expansive, setting this book apart from most others I have read. It's packed full of rich examples which are used to solidify the topic being covered. At several places the authors reach out to explain when the subject is addressing ambiguous or otherwise undocumented information which is to great advantage to the reader and worthy of recognition.