The administration of sendmail, the most widely used electronic mail server software on server computers, is known to be a very complex task, even for experienced system administrators. The software is very powerful and efficient in what it does, however, fulfilling email communication needs on any network, be it intranet or Internet.

Email has evolved to be the most important piece of the Internet, critical to any organization. While bits of information about tuning sendmail software were available over the Internet, there wasn’t a single resource covering all aspects of sendmail performance. Christenson has now filled that gap.

This book covers sendmail servers, as well as client programs such as post office protocol (POP) and Internet message access protocol (IMAP). While this book targets the open source (freeware) version of sendmail, it should also prove useful in Unix environments that are running commercial versions of the software, such as Sendmail Pro or Sendmail Switch. I haven’t found a single paragraph of boring irrelevant information anywhere in this book. The author covers sendmail 8.12, the latest version available today, although much of the information can be applied to older versions.

There are nine chapters in the book, as well as a bibliography and an index. Chapter 1 is a brief introduction, and includes some general tuning ideas, such as setting up a caching-only domain name system (DNS) server. Chapter 2 briefly covers installing and configuring the open source version of sendmail software. Chapters 3, 4, and 5 cover the tuning of email relaying, receiving, and sending, respectively. Chapter 6 covers sendmail configuration tuning, security, and mail filters (milters). Chapter 7 discusses how to find and remove performance bottlenecks. Chapter 8 discusses load generation and testing for sendmail, as well as email clients, POP, and IMAP. Chapter 9, the last chapter, lists some useful resources on system administration and sendmail topics.

The book focuses entirely on Unix operating system flavors, such as Sun Solaris, Linux, BSD, and so on. If you are one of the few users looking for performance tuning information on sendmail for Windows NT (or IndigoMail), this book is not for you. Most of the performance scenarios are discussed for the case of a CPU-bound Unix computer and an I/O-bound Unix computer.

Instead of a four-page bibliography at the end of the book, references should have been provided at the end of each chapter. There are no exercises provided anywhere in the book.

Undoubtedly, this book fulfills its purpose very well, and fills an important niche that simply hasn’t been addressed until now. The book is highly recommended for advanced Unix system administrators with a sendmail background, and for application developers working on email software projects.