To replicate this problem:
- go to Virtualmin's configuration page and set "Yes" to the "Redirect HTTP to HTTPS by default?" option;
- create a virtual server and get on Google Chrome:
sub16.domain.com redirected you too many times.
and on FireFox:
The page isn’t redirecting properly
Firefox has detected that the server is redirecting the request for this address in a way that will never complete.