Using qmail in an RPM (or YUM) world...
I was trying to run 'yum update' on my webmail server, which runs the highly recommended qmailrocks.org distro. Well, to get it to stop trying to install exim / sendmail / postfix I was able to create a "fake_mta.spec" based on one I found online (but had to transcribe into a VM box):
# Use rpmbuild -bb to install this Buildarch: noarch Conflicts: sendmail, exim, postfix, qmail Group: Productivity/Networking/Email/Servers License: GPL Name: fake_mta Provides: smtp_daemon Release: 1adm Summary: Fake package to protect qmail's sendmail files. Version: 1 %description A fake package so that qmail won't get hosed, even tho RPM/YUM don't know about it. %changelog * Sun Sep 25 2005 Aaron D. Marasco - Shamelessly stolen from SuSE security list (Chris Mahmood) %files /usr/sbin/sendmail