CHAPTER 35

Handling Email

IN THIS CHAPTER

How Email   Is  Sent    and Received

Basic   Postfix Configuration   and Operation

Using   Fetchmail   to  Retrieve    Mail

Choosing    a   Mail    Delivery    Agent

References

Email is still the dominant form of communication over the Internet. It is

fast, free, and easy to use. However, much of what goes on behind the scenes
is extremely complicated and would appear scary to anyone who does not
know much about how email is handled. Ubuntu comes equipped with a
number of powerful applications that will help you build anything from a
small email server, right through to large servers capable of handling
thousands of messages.

This chapter shows you how to configure Ubuntu to act as an email server.
We look at the options available in Ubuntu and examine the pros and cons of
each one. You also learn how mail is handled in Linux and, to a lesser extent,
in UNIX.

How Email Is Sent and Received

Email is transmitted as plain text across networks around the world using the
Simple Mail Transfer Protocol (SMTP). As the name implies, the protocol
itself is fairly basic, and it has been extended to add further authentication and
error reporting/messaging to satisfy the growing demands of modern email.
Mail transfer agents (MTAs) work in the background, transferring email from
server to server, allowing emails to be sent all over the world. You might have
come across such MTA software such as Sendmail, Postfix, Fetchmail, Exim,