# apt-get install -y msmtp-sendmail Reading Package Lists... Done Building Dependency Tree... Done The following NEW packages will be installed: msmtp-sendmail 0 upgraded, 1 newly installed, 0 removed and 50 not upgraded. Need to get 0B/2419B of archives. After unpacking 0B of additional disk space will be used. Committing changes... Preparing... #################################################################################################### [100%] file /usr/sbin/sendmail from install of msmtp-sendmail-1.6.6-alt1.1.noarch conflicts with file from package postfix-1:3.6.2-alt1.x86_64 E: Error while running transaction