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Chapter 5
CHAPTER 5
Mail
This chapter shows how to build an email service for a small- to medium-size site.
The elements of the service include:
• The Postfix server as the SMTP mail transfer agent (MTA), which accepts mail
from your users and interacts with other sites across the Internet to affect the
delivery of mail.
• Post Office Protocol (POP) and Interactive Mail Access Protocol (IMAP) servers,
to deliver mail at your site to your users.
• Simple Authentication and Security Layer (SASL) for authenticating mail, to pre-
vent spoofing.
We’ll configure Postfix to use traditional file-based authentication, which will scale
to thousands of users. Larger email installations might store email account names
and passwords in a relational database or an LDAP directory. For an example of an
extremely scalable email server based on Postfix with LDAP authentication, see
Zimbra (http://www.zimbra.com).
The solutions in this chapter bring diverse components together to make a robust,
secure, and efficient mail delivery system. Today, people like Wietse Venema (the
inventor of Postfix) have reduced much of the complexity and uncertainty involved
in configuring email systems. Instead of sweating over complex MTA configuration
of an email server, Linux system administrators have other interesting problems to
solve:
• How to secure email, a medium not designed with security in mind, against
spoofing attempts ...