This is an old revision of the document!
First join CACert.org.
Advice taken from:
http://wiki.cacert.org/wiki/Exim4Configuration http://wiki.exim.org/EximServerSslCertificate http://wiki.cacert.org/wiki/ThunderBirdAdvancedConfig http://edin.no-ip.com/content/exim4-courier-ssl-debian-etch-mini-howto