How to fix 'suexec command was not found on your system.' in Virtualmin

I ran into this error message in Virtualmin when I want to disable Bind and Mail for Domain, I searched around for answers and I couldn't find it.  Finally I found out that Suexec was not installed correctly, so I reinstalled again with the command

apt-get install apache2-suexec-custom

And then it changed to another error message, where it shows.

The Suexec command on your system is configured to only run scripts under /var/www, but the Virtualmin base directory is /home. CGI and PHP scripts run as domain owners will not be executed.

 The above  link also shows the solution to that problem.

Enjoy.