apt-get error message

root@libertas:/home/tekth# apt-get install aide
Reading package lists... Done
Building dependency tree
Reading state information... Done
aide is already the newest version.
You might want to run 'apt-get -f install' to correct these:
The following packages have unmet dependencies:
 bsd-mailx : Depends: default-mta or
                      mail-transport-agent
E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).