I am trying to install postfix on Ubuntu with bellow tutorial

https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-postfix-on-ubuntu-16-04

but while Initialize the Maildir and Test the Client i am getting below error

root@ubuntu-shm:~# ls -R ~/Maildir
ls: cannot access '/root/Maildir': No such file or directory

I havent created non root user.