The Exim SMTP Mail Server: Official Guide for Release 4
"so well written I learn new things every time I open it""The book exceeds my expectations.""an excellent book that is very well written""well presented and easy to follow""If there's even a whiff of a chance of you having to come into contact with Exim or its runtime configuration, then I can do nothing else but strongly recommend this book. The detail's there in spades, it reads very well, and is a fine complement to the reference manual." "the book is simply amazing. I find the format/style/whatever 100 times better than [other documentation]. Wish I had this thing a month ago."