I am now well on my way through all of the comments, updates and corrections that other members of the Exim community have kindly made to my original draft.

I'm now two and a half years into a project I thought would only take six months. At one point I considered giving up... 

Part 1 has been revised somwhat and now contains the following sections:

• Overview of networks
• Overview of e-mail and how it works
• Overview of Exim
• Tools and testing techniques
• Preparing the server

Part 2 contains the following example configurations.

Configs are shown on the right hand page with the corresponding explanation shown opposite the code on the left-hand page. This is how I find it easiest to read configurations (side-by-side), and several other reviewers agreed so we kept the format. (PLEASE NOTE: These are subject to change at any time but have been unchanged for 8 months now)

Configuration C1
A very simple configuration to introduce Exim. A mail server that can be used to send e-mails to other people locally (within your site), or externally (sent out over the Internet).

Configuration C2
This works in exactly the same as Configuration 1, but all of the “scary” settings are hidden away in a master config file, and everything else is kept in two easy-to-understand files.  Normally you will only have to edit these subsidiary files, leaving the master untouched. This forms the initial config on which all the later ones build incrementally.

Configuration C3
Automatically redirects messages sent to one person to somebody else's mailbox. This is useful if some is on holiday or leaves the organization. Our redirect facility does not require any special permissions to read or modify the system “aliases” file. Includes some changes to make it easy to re-use the same set of configuration files for many e-mail servers without having to duplicate work – for example if you are setting up another site.

Configuration C4
We specify what to do if an e-mail can't be delivered the first time, and how often to keep trying to send e-mails before finally giving up. We also check that nobody is trying to deliberately send “rogue” emails that are designed to crash computers or slow other peoples networks down.

Configuration C5
The mail server now becomes a “mail-relay”. A “mail-relay” is often used to reduce the load on other mail servers, or to allow other mail servers containing sensitive information to be “hidden” behind them on private networks. We also begin to start using our own custom error messages that make it easier to identify what went wrong should an e-mail encounter delivery problems.

Configuration C6
The mail server now becomes a “mail-hub”. A “mail-hub” is often used to centralize sending, receiving and scanning e-mail messages in organizations with multiple mail servers. We also add an automated warning message  to users who send messages over a certain size limit. Several new custom error messages and replies are added. For local destination addresses we also check that the user exists before trying to deliver an e-mail to it.

Configuration C7
Support is added for third party mail scanning services and security appliances. Workarounds are shown for users on broadband connections that block “Home” e-mail servers. Simple e-mail address lists are also covered. An address list allows a single e-mail address to be used to send a message to several people at once. This configuration provides a solid platform for building further mail servers with Anti-Virus, Anti-Spam and LDAP facilities.

An example showing the style of the book can be found here:

http://www.exim-new-users.co.uk/How-Exim-processes-messages-example.pdf  

An example of the side-by-side configuration and explanation can be found here:

http://www.exim-new-users.co.uk/Side-by-side-config-example.pdf 

(Older versions of KGhostView do not display these PDFs correctly. if you experience problems please use KPDF, Gnome PDF or Acrobat instead)