remove all mail services from ubuntu

remove sendmail ubuntu

$ sudo apt-get purge sendmail*
$ apt-get remove sendmail
$ apt-get purge sendmail

remove postfix ubuntu

$ sudo apt remove postfix && apt purge postfix
$ sudo autoremove

When I install Postfix again, the installation does not ask the questions like on the first installation. I still have my previous configuration. Why can not I reset the Postfix configuration ?

If I reconfigure Postfix, I still have the previous configuration :

$ sudo dpkg-reconfigure postfix

remove mailutils ubuntu

$ sudo apt-get remove  mailutils
$ sudo apt-get remove --auto-remove mailutils
$ sudo apt-get purge mailutils
$ sudo apt-get purge --auto-remove mailutils