Linux Network Administrator's Guide, Second Edition

Chapter 19. Getting Exim Up and Running

This chapter gives you a quick introduction to setting up Exim and an overview of its functionality. Although Exim is largely compatible with sendmail in its behavior, its configuration files are completely different.

The main configuration file is usually called /etc/exim.conf or /etc/exim/config in most Linux distributions, or /usr/lib/exim/config in older configurations. You can find out where the configuration file is by running the command:

$ exim -bP configure_file

You may have to edit the configuration file to reflect values specific to your site. In most common configurations there isn’t a great deal to change, and a working configuration should rarely have to be modified.

By default, Exim processes and delivers all incoming mail immediately. If you have relatively high traffic, you may instead have Exim collect all messages in the so-called queue, and process them at regular intervals only.

When handling mail within a TCP/IP network, Exim is frequently run in daemon mode: at system boot time, it is invoked from /etc/init.d/exim ^[113] and puts itself in the background, where it waits for incoming TCP connections on the SMTP port (usually port 25). This is beneficial whenever you expect to have a significant amount of traffic because Exim doesn’t have to start up for every incoming connection. Alternatively, inetd could manage the SMTP port and have it spawn Exim whenever there is a connection on this port. This configuration might ...