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sendmail Performance Tuning


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  • Copyright 2003
  • Edition: 1st
  • Book
  • ISBN-10: 0-321-11570-8
  • ISBN-13: 978-0-321-11570-6

"This book is great. Nick covers a wide range of materials--everything from how to architect the mail system and what disks to buy to how to configure your router. This book should be a basic reference for anyone who needs to get down into the guts of a sendmail-based system and make it shine."

--Eric Allman, the creator of sendmail and Chief Technical Officer, Sendmail, Inc.

As email traffic continues to increase, system administrators must be able to guarantee that their email servers can deliver reliable performance today and bear larger loads tomorrow. sendmail Performance Tuning is a practical guide to building, tuning, and testing email servers based on sendmail to function more efficiently, handle more messages, and resist both accidental and malicious load-related incidents.

Featuring sendmail 8.12 (and earlier versions), the book begins with an introduction to sendmail and performance tuning. Author Nick Christenson then describes best practices for building, installing, and maintaining a system and details proven techniques for tuning email relaying, reception, and sending. This strategic guide to configuration and security is followed by precise directions for managing bottlenecks and load testing. By the book's end, readers should know exactly how to optimize system performance.

Key topic coverage includes:

  • A detailed description of the step-by-step operations that occur during email transmission and reception
  • How to send and store email most efficiently
  • What the performance characteristics of POP and IMAP are
  • How to determine which sendmail configuration parameters might improve performance
  • How to locate and eliminate bottlenecks
  • Methods and pitfalls in testing email servers before they are installed in a production environment

Whether you are looking to solve an immediate problem or gain a deeper understanding of email servers, sendmail Performance Tuning provides clear guidance and valuable insight.


Sample Content

Online Sample Chapter

Finding and Removing Bottlenecks

Downloadable Sample Chapter

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Sample Chapter 7

Table of Contents

(NOTE: Each chapter concludes with a Summary.)


1. Introduction.

Performance Tuning Examples.

sendmail Versions Covered.


Email Server Tasks.

Tuning Isn't Always Necessary.

Not So Fast.

Email System Profiling.

General Tuning Ideas.

2. sendmail Introduction.

Obtaining sendmail.

Building sendmail.

Creating a .cf file.

Why Use M4?

System Setup.

3. Tuning Email Relaying.

What Happens During Relaying.



File Space.


4. Tuning Email Reception.

What Happens During Email Reception.

Recipient Verification.

Storage Systems.


Solid State Disks.

POP Tuning Specifics.

Message Store Hashing.

IMAP Tuning Specifics.

5. Tuning Email Sending.

Mailing Lists.

Command-Line Message Generation.

Draining Queues.

Another Mailing List Strategy.


More Notes on Mass Mailing.

6. Configuration, Security, and Architecture.


Security and Performance.

Other General Strategies.

7. Finding and Removing Bottlenecks.

Kernel Parameters Run Amok.

The Quick Fix.



Removing Bottlenecks.

8. Load Generation and Testing.

Test System Setup.

Testing Tools.

Load Testing Pitfalls.

9. Conclusion.


Index. 0321115708T08292002


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 are going on behind the scenes on an email server, information about email software features along with how options for deploying this software might impact 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. However, other system administrators and email application developers may find many of the topics discussed here to be useful. While the thrust of this book revolves around the use of the Open Source sendmail software package, much of the information in these pages should be useful in non-sendmail environments. However, this is not a book on basic system administration, sendmail administration, or general UNIX performance tuning. It is assumed 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 book.

It is intended that this book be read sequentially. Chapters build on information found in pre-vious chapters, so skipping around may be a bit confusing. One exception to this is the sendmail introduction chapter 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 is a "Summary" section which lists what I believe are the key points discussed in the chapter. While these summaries are not a substitute for the information in the chapter, it is my hope that the reader will find these useful in reinforcing some of the more important points that have been discussed.



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