If you want an internal mail server for your business then Linux is an excellent choice. For a start, it's free. Not only the operating system but also the essential software components that make up an e-mail server can be acquired without expense.
For most purposes, e-mail is a mature technology. Your server requirements are unlikely to change significantly over time. While commercial servers make their money by introducing new features and forcing customers onto an upgrade path, Linux gives you no such pressure. Once the server is set up, it only needs to be maintained. Sweeping upgrades to the operating system and other software should not be necessary.
On the other hand, setting up a Linux e-mail server can be bewildering. There are many different components to consider, all of them with a wide variety of configuration options and their own unique approaches and terminologies. Which components should you choose, and how can they be made to work together?
This book provides you with one way to set up a fully working e-mail server. There are many other possible ways, and the options can be bewildering. The purpose of this book is to provide you with a path that will work, without bewildering you (too much!) with a massive array of confusing alternatives.
As you work your way through this book, your e-mail server will take shape. We'll start with the essentials—building an e-mail server that can send and receive messages using SMTP, POP, and IMAP. From then on, we'll supplement your configuration with extra features: webmail, anti-virus, anti-spam, and setting up e-mail processing rules. We'll also see how to protect an e-mail server from misuse, and finally learn how to develop and implement an e-mail server backup strategy.
Specifically, here's what we will cover in each chapter:
Chapter 1 takes you through the essential elements on a Linux e-mail server, and the network protocols that make e-mail possible. Like it or not, running a Linux e-mail server does require some understanding of the underlying networking—and this chapter is where you will start to get that understanding.
In Chapter 2, you'll learn about basic Postfix setup. Postfix is our chosen mail transfer agent (MTA), which forms the heart of any e-mail server. The MTA is responsible, among other things, for moving messages between the various mail servers on the Internet.
Chapter 3 covers what to do with incoming e-mail. It will show you how to setup IMAP and POP access to mailboxes. This means that users will be able to send and receive messages using their familiar e-mail clients.
Now the basics are covered, we can add some more advanced features. Chapter 4 shows how to set up webmail access using SquirrelMail. This will give users easy out-of-office access to their e-mail.
Chapter 5 looks at how your installation can be secured to prevent misuse of your users' data and the e-mail facility itself.
Chapter 6 and Chapter 7 introduce Procmail, an application for processing e-mail messages. For example, you can set up forwarding rules, so that messages meeting particular criteria can be forwarded to another user, or handled in some other way. You'll also see how to use Procmail to set up automatic replies to certain messages.
In Chapter 8 we'll use SpamAssassin in conjunction with Procmail to filter out the wide range of spam that afflicts the modern e-mail user. Then in Chapter 9 you'll see another way to protect users from rogue e-mail—this time the spread of e-mail viruses.
Finally in Chapter 10 you'll see how to protect all your hard work by backing up not only the e-mail itself, but also all of the configuration options that make up your e-mail server. Of course, you'll also learn how to restore data from these backups.
In this book you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meanings.
Code words in text are shown as follows: "The vacation.cache file is maintained by formail"
New terms and important words are introduced in a bold-type font. Words that you see on the screen—in menus or dialog boxes, for example—appear in the text as follows: Dragons are mystical monsters.
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