Install Postfix using Mailutils on Ubuntu 19.04 server for sending out mail only

I followed this tutorial: https://computingforgeeks.com/how-to-install-and-configure-postfix-as-a-send-only-smtp-server-on-ubuntu-18-04-lts/ I'm trying to setup a send only mail from my Ubuntu 19 server. I followed the guide above and tried to install mailutils using:

apt install mailutils

It installed something but I'm not sure what as the mailutils command doesn't work as seen here: I then installed via the following command:

apt install libmailutils-dev

That worked as mailutils command now runs, but I didn't get a GUI interface to select like how the guide shows it: - What do I need to do now since the Postfix install GUI didn't popup according to the guide? - Also is it an issue if I installed mailutils and then libmailutils-dev?