In order to make Virtualmin work you will most likely need to fix this error.
A problem was found with your Postfix Virtual Maps : No map sources were found in Postfix config.
Just add the following text in Postfix
Webmin > Servers > Postfix Mail Server > Virtual Domains >
Domain mapping lookup tables = hash:/etc/postfix/virtual
Once the line is added to Postfix, you should go back to Virtualmin module and re-check config. via JazzyMarketing