Tools - Exim

David Williamson @ Varilink Computing Ltd

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This repository contains a Docker Compose project that facilitates easy testing on the desktop of configuration setups for the Exim Internet Mailer as packaged for Debian.

Setup

Before using this repository, you must do three things:

1. Create folder etc/ (file paths are relative to the project root) containing your Exim configuration under etc/exim4/ and your mailname file in etc/mailname
2. Create folder src/ containing any testing Helper Scripts you want to use.
3. Create file .env containing values for the UID and GID of your desktop user account.

Initialising your Exim configuration

A utility is provided to initialise the contents of your etc/ folder with the relevant files from the exim package in Debian:

docker-compose run --rm init

To ensure that the files created by this are owned by your desktop user on the host, your .env file must contain the correct UID and GID; for example, here are the contents of my .env file:

UID=1000
GID=1000

Keeping track of your Exim configuration changes

As you then make changes to the default Exim configuration provided via the Debian package, it's useful to be able to keep track of what you've changed. For this purpose, this repository provides a diff service:

docker-compose run --rm diff

This produces a report of any configuration files that you have added to or deleted from those provided by the package install. It also reports any changes that you have made to configuration files provided by the package install.

Testing your Exim configuration

When you've made your changes to customise Exim to your specific needs, you can test the results:

docker-compose run --rm test

This will take you into a bash shell in a container having first run update-exim4.conf to apply your customised configuration within that container. There you can use the standard Exim provided testing tools; for example:

exim -bt recipient@example.com

To test a recipient address for deliverability.

Any custom scripts that you've put into your src/ folder for testing purpose will also be available to use; for example, if you had a script test.sh in there, which looked something like this:

echo "Sending to recipient@example1.com from sender@example2.com"

/usr/sbin/exim -v $1 recipient@example1.com <<- EOM
	To: recipient@example1.com
	From: sender@example2.com
	Subject: Test
	Test sent via the Varilink Exim configuration testing tool.
EOM

Then you could run that script via:

. /usr/local/src/test.sh

I like to have one or more scripts like this, for different combinations of sender and recipient, which I can use to test send emails and if required pass an optional debugging flag; for example:

. /usr/local/src/test.sh -d-all+auth

This will give me debugging output for any custom authentication changes that I've made.