Here is an example of an Exim configuration file that will:

Accept messages FOR the domain example.com.

Accept messages FROM itself (127.0.0.1) and two other ranges of IP addresses (10.0.0.0/8 and 192.168.0.0/16).

This config has very few features but is still functional enough to work (on a test system that is not accesible from the Internet).

This config also assumes that if you wish to send an email to This e-mail address is being protected from spam bots, you need JavaScript enabled to view it , that alice has a valid account and mailbox on the Exim server itself. 

Here we use two additional files to store a list of local domains that we will accept messages for and a list of IP addresses that we will accept messages from. This is still avery simple configuration that does not have any specific sections to guard against spam and virues, however a complete full-blown configuration example would often be overewhelming for a new user. This config is made up of three seperate files:

/etc/exim/exim.conf

/etc/exim/exim-accept-mail-for-this-list-of-local-domains.txt

/etc/exim/exim-accept-mail-from-this-list-of-ip-addresses.tx

An Example configuration file taken from a defualt installation of Red Hat Enterprise Linux or CentOS.  This file is similar to the one you would find in the /etc/exim/ directory on a server running exim v4.43.

 An example of an advanced and extremely complicated Exim configuration file can be found here:

(I have no idea how it works but apparently it does. This is based on the Exim configuration used at Cambridge University, the birthplace of Exim) 

http://www-uxsup.csx.cam.ac.uk/~fanf2/hermes/doc/talks/2005-02-eximconf/