Preface

Most people consider email to be the "killer application" of the Internet. An astounding amount of email crosses the globe every day. These messages flow from server to server in ever-increasing quantities. Some email servers originate email, some relay it from one network to another, some store email for later retrieval, and some perform all of these tasks. This book explores the intricacies of email communication, focusing on sendmail-based solutions, and suggests how one can build, design, and tune email servers that will accomplish each of these tasks more efficiently. Applying the suggestions in this book will help email servers perform better under increasing load, expedite the delivery of their messages, and make them more resistant to accidental and malicious load-related incidents. These pages contain detailed descriptions of precisely what actions go on behind the scenes on an email server, information about email software features and ways that options for deploying this software might affect performance, suggestions on methods and pitfalls to effectively test email server configurations, and actual test data to support the claims made in this book.

This book is intended to be read primarily by system administrators of UNIX-based email servers. Other system administrators and email application developers, however, may find many of the topics discussed here to be useful. While the thrust of this book targets the use of the Open Source sendmail software package, much of the information presented here should prove useful in non-sendmail environments as well. However, this is not a book on basic system administration, sendmail administration, or general UNIX performance tuning. I assume that the reader of the book either understands these issues, if only at a basic level, or knows where to look if clarification or more information about some point is necessary. While some duplication of material between this book and others is both necessary and beneficial, I've tried to repeat information that can be found in other books as little as possible. My recommendations on excellent books that provide this information are available in the concluding chapter, and I strongly recommend them to readers of this text.

This book is intended to be read sequentially. Chapters build on information found in previous chapters, so skipping around may prove confusing. One exception involves the sendmail introduction chapter (Chapter 2), which may be safely skipped by readers who are familiar with sendmail and especially comfortable with building version 8.12 sendmail.cf files using M4.

At the end of each chapter, a "Summary" section lists the key points discussed in the chapter. While these summaries are not substitutes for reading the chapter, the reader should find them useful in reinforcing some of the more important points that have been discussed.

In this book, literal information as it might be expressed on a computer system is rendered in a fixed-width Courier font. This includes actual file names, commands as they are typed into a computer, source code of any form, and variable names as they appear in configuration files. A variable is indicated by the use of Courier italic. For example, /var/mail/username would indicate a variable file name that should be replaced with a real username, and this file resides in the /var/mail directory.

Many people have helped make this a better book. I'd like to thank William von Hagen for his assistance on the topic of Linux filesystems. I couldn't have asked for a better team of reviewers, and this book was much improved by their contributions. These people were Claus Aßmann, Tim Bosserman, Scott Lystig Fritchie, Brad Knowles, Jim Larson, and Alan Strassberg. I'd also like to thank the editing team at Addison-Wesley, Karen Gettman and especially Jessica Goldstein, for making the process of writing this book much easier for me than I had feared. Also deserving of thanks are Tyrrell Albaugh for holding everything together, and Jill Hobbs for improving my sloppy writing. Finally, I'd like to single out the contribution of Gregory Neil Shapiro, who gets a "gold star" for the effort he put in to improve this book. If the reader happens across an especially interesting bit of sendmail information in these pages, there's a good chance it has been included because Greg suggested it to me. Of course, I take full responsibility for any errors or omissions that might have occurred.

I hope you enjoy this book.

Nick Christenson
El Cerrito, California



sendmail Performance Tuning
sendmail Performance Tuning
ISBN: 0321115708
EAN: 2147483647
Year: 2005
Pages: 67

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