The 'mail server' group of packages does not mention Exim, and it appears to be
impossible to deselect sendmail even when one is installing Postfix or Exim instead.
Ok, I have added Exim in comps. It is an optional package in the mail server
group. Being able to deselect sendmail is not possible at this point. The user
will have to use the alternatives mechanism to change from sendmail to exim.
closing old bug...