(tdn@krusty) (08-06-12 8:56) (P:0 L:1) [0]                                     [ 08:56:55 up 6 min,  2 users,  load average: 0.64, 1.28, 0.74]
~ $ sudo aptitude install postfix
Reading package lists... Done
Building dependency tree
Reading state information... Done
Reading extended state information
Initializing package states... Done
Building tag database... Done
The following packages are BROKEN:
  exim4-config
The following NEW packages will be installed:
  postfix
The following packages will be REMOVED:
  exim4-daemon-light
0 packages upgraded, 1 newly installed, 1 to remove and 0 not upgraded.
Need to get 0B/1229kB of archives. After unpacking 2019kB will be used.
The following packages have unmet dependencies:
  exim4-config: Conflicts: postfix but 2.5.1-2ubuntu1 is to be installed.
Resolving dependencies...
The following actions will resolve these dependencies:

Remove the following packages:
exim4-base
exim4-config

Score is -528

Accept this solution? [Y/n/q/?]
The following packages will be automatically REMOVED:
  exim4-base exim4-config
The following NEW packages will be installed:
  postfix
The following packages will be REMOVED:
  exim4-base exim4-config exim4-daemon-light
0 packages upgraded, 1 newly installed, 3 to remove and 0 not upgraded.
Need to get 0B/1229kB of archives. After unpacking 709kB will be freed.
Do you want to continue? [Y/n/?]
Writing extended state information... Done
Preconfiguring packages ...
dpkg: exim4-base: dependency problems, but removing anyway as you request:
 exim4-daemon-light depends on exim4-base (>= 4.69).
(Reading database ... 244394 files and directories currently installed.)
Removing exim4-base ...
 * Stopping MTA                                                                                                                           [ OK ]
Removing exim4-config ...
dpkg: exim4-daemon-light: dependency problems, but removing anyway as you request:
 mailx depends on exim4 | mail-transport-agent; however:
  Package exim4 is not installed.
  Package mail-transport-agent is not installed.
  Package exim4-daemon-light which provides mail-transport-agent is to be removed.
 smokeping depends on exim4 | mail-transport-agent; however:
  Package exim4 is not installed.
  Package mail-transport-agent is not installed.
  Package exim4-daemon-light which provides mail-transport-agent is to be removed.
Removing exim4-daemon-light ...
 * Stopping MTA                                                                                                                                  /sbin/start-stop-daemon: warning: failed to kill 5762: No such process
invoke-rc.d: initscript exim4, action "stop" failed.
dpkg: error processing exim4-daemon-light (--remove):
 subprocess pre-removal script returned error exit status 3
Errors were encountered while processing:
 exim4-daemon-light
E: Sub-process /usr/bin/dpkg returned an error code (1)
A package failed to install.  Trying to recover:
Reading package lists... Done
Building dependency tree
Reading state information... Done
Reading extended state information
Initializing package states... Done
Writing extended state information... Done
Building tag database... Done