In the latest version of CWP, when you create an email account, you will see message "email account created successfully", but nothing will be there in /var/vmail folder. It may be a bug or design decision.
To create folders and files in /var/vmail, use roundcube to log into your newly created email account. Once you are logged into your email account, you will see all the required folders and files were generated with correct owner and group in /var/vmail.
I also found this issue. I just logged into my email account using roundcube and it worked for me.