sudo apt-get install --reinstall exim4-config
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages were automatically installed and are no longer required:
  libgnomecupsui1.0-1c2a planner liblog4net1.2-cil dia-libs vorbis-tools libnet-daemon-perl g++-4.1 rhythmbox libxcb-xv0 libdbi-perl
  libdbd-mysql-perl libtext-glob-perl libdate-calc-perl mysql-client-5.0 libboost-thread1.34.1 libcarp-clan-perl libboost-date-time1.34.1
  libplrpc-perl libstdc++6-4.1-dev libx264-54 swftools dia-gnome libt1-5 eog libmono-cecil0.5-cil libxcb-shape0 libxul0d libiso9660-4
  libfile-find-rule-perl libmozjs0d libmono-peapi1.0-cil dia-common libboost-filesystem1.34.1 libmono-system-runtime1.0-cil
  libmono-relaxng1.0-cil libgecko2.0-cil libxul-common libxcb-shm0 inkscape youtube-dl libnumber-compare-perl gnome-cups-manager
  libbit-vector-perl libungif4g
Use 'apt-get autoremove' to remove them.
The following NEW packages will be installed:
  exim4-config
0 upgraded, 1 newly installed, 0 to remove and 1 not upgraded.
2 not fully installed or removed.
Need to get 0B/310kB of archives.
After this operation, 1053kB of additional disk space will be used.
Preconfiguring packages ...
(Reading database ... 150219 files and directories currently installed.)
Unpacking exim4-config (from .../exim4-config_4.69-2_all.deb) ...
dpkg: error processing /var/cache/apt/archives/exim4-config_4.69-2_all.deb (--unpack):
 unable to stat `./etc/exim4' (which I was about to install): Invalid argument
Errors were encountered while processing:
 /var/cache/apt/archives/exim4-config_4.69-2_all.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)