Sendmail is the Godfather of all email It is incredibly stable, resource-friendly, flexible and it has withstood the test of time. I read this book years ago, and have referred to it periodically over the past six or seven years. It was a great book to get you started with Sendmail, and help you realize that it is not as complicated as it is made out to be. It starts out assuming you know nothing, and by the end, you should be 99% prepared to administer your own server. (I say 99% because you will probably still want to learn a bit more about spam filtering and virus scrubbing). A great book for beginners, and a useful reference for experienced users.