The Mail Transfer Agent (MTA) is perhaps the most important part of a mail system. It is responsible for receiving messages from the Internet or from your own users and doing what it can to make sure that the messages arrive at their destinations—other mail servers or mailboxes of your users.
Postfix has been chosen as the mail transfer agent to be covered in this book. Postfix has a large feature set, it has an excellent security track record, it is fast, easy to configure, and under active development.
This book assumes that you are running Postfix 2.0 or later. Any feature or behavior of Postfix that is specific to releases later than 2.0 will be noted.
This first section gives a brief introduction ...