Depends on your configurations, but there are some default links for your users.
Both Nginx and Apache have the ability to access off port configurations on the normal port 443 and port 80 via what's call a reverse proxy. Check out the following directories to see examples
Nginx: /etc/nginx/conf.d/vhosts
Apache: /usr/local/apache/conf.d/vhosts
Pick a domain, and look for virtualhosts such as webmail. or panel.