After successfully using Postfix on my Ubuntu machines, I decided to try Exim on a new server, based on some people commenting it's easier to set up and use.
Well I ran into issues with my Rails app right away, and, considering how easy Postfix had been to use, I decided to remove Exim and install Postfix instead.
However, how to cleanly remove it was hard to find...
Here's all you need to do to cleanly and easily get rid of Exim4:
apt-get remove exim4 exim4-base exim4-config exim4-daemon-light
You may have the exim4 logs directory left behind. Just get rid of it manually, if you do:
rm -r /var/log/exim4/