I want to begin exploring moving myself away from google apps, because it's expensive, and it looks like citadel has all of the groupware functions I need. So I am trying to install citadel-suite with:apt-get install citadel-suiteBut it returns:citadel-suite: depends: citadel-mta but it is not going to be installedE: Unable to correct problems, you have held broken packages.Well, yes. It does require citadel-mta. That's half the point. So why is it not going to be installed?  What broken packages do I have held?  Why are they broken?  Why are they held? I didn't hold them. Or break them, for that matter.The problem with apt-get is that, for the 10 years I have been using it, it has, to borrow an Apple phrase, just worked.  Now that it isn't, I'm rather at a loss.  I did try the -f switch, but it didn't help.  I haven't made any modifications to /etc/apt/sources.list, so I can't revert them.  What should I try next?  
Fix held broken packages on debian?
debian;apt
... But it is not going to be installed generally means that a serious dependency conflict will ensue if it's allowed to go on.Try the following command: aptitude why-not citadel-mtawhy-not basically checks dependencies and returns the reasons it would have to not fill a particular dependency automatically. In the case of my system at home:shadur@leviathan:~$ aptitude why-not citadel-mtai   exim4-daemon-light Conflicts mail-transport-agentp   citadel-mta        Provides  mail-transport-agentApparently citadel-mta is a full-on MTA and will therefore replace whatever mail-transport-agent package you currently have installed. Explicitly telling it to install citadel-mta as well should be enough to break the deadlock.NOTE: Doing so means your current mail server software will be replaced by the one that comes with citadel. Make very sure that that's what you want before you do this.