I'm more of a CentOS person, but after some issues on my new box I switched to Ubuntu server.
I am working on getting it setup as a mail server (mainly for testing at the moment and soon be live). I performed apt-get install sendmail then apt-get install exim4 and got the message:

Could not perform immediate configuration on 'exim4-daemon-light'. Please see man 5 apt.conf under APT:: Immediate-Configure for details.

I have Ubuntu Server 10.10 32-bit on a Dell Intel Poweredge.