root@dex:~# apt-get install sendmail
Reading package lists... Done
Building dependency tree... Done
The following extra packages will be installed:
  procmail rmail sendmail-base sendmail-bin sendmail-cf sensible-mda
Suggested packages:
  sendmail-doc logcheck sasl2-bin libsasl2-modules libsasl2-modules-plain libsasl2-digestmd5-plain libsasl2-digestmd5-des cyrus-common
Recommended packages:
  resolvconf
The following packages will be REMOVED:
  postfix
The following NEW packages will be installed:
  procmail rmail sendmail sendmail-base sendmail-bin sendmail-cf sensible-mda
0 upgraded, 7 newly installed, 1 to remove and 0 not upgraded.
Need to get 0B/2283kB of archives.
After unpacking 2830kB of additional disk space will be used.
Do you want to continue [Y/n]? Y
dpkg: postfix: 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 postfix which provides mail-transport-agent is to be removed.
(Reading database ... 68733 files and directories currently installed.)
Removing postfix ...
invoke-rc.d: unknown initscript, /etc/init.d/postfix not found.
dpkg: error processing postfix (--remove):
 subprocess pre-removal script returned error exit status 100
Errors were encountered while processing:
 postfix
E: Sub-process /usr/bin/dpkg returned an error code (1)
root@dex:~#