Aw, jeez. I did miss that detail. Of course the system is messed up. Hosting providers are absolutely disastrously bad at preinstalled systems. I don’t know why, but they are incapable of installing anything correctly no matter how simple it is, and they’re going to break some other stuff in the process, too.
@rch7 please start with a freshly installed, supported, OS. Do not get the “preinstalled with Webmin” image. Get a freshly installed, supported, OS. Your hosting provider is not capable of installing software. I don’t know why. So don’t let them break your system before you even start.
I’m beginning to think they do this on purpose to intentionally make people think Webmin or Virtualmin is buggy and unreliable. It’s really easy to install, if you follow the docs. So, I can’t come up with an explanation for why every time someone says, “I got an image with Webmin/Virtualmin preinstalled” it’s always a mess. We’ve never seen that mentioned when the problem wasn’t related to something the hosting provider did weird.
Absolutely not. Installing Webmin does nothing to the system. It makes no changes to configuration files or anything else. It depends on a few other packages, but Postfix is not one of them.
But, if you let your hosting provider start messing about on the system, they are going to mess something up. They are incapable of doing otherwise.
So, we are back to: Start with a freshly installed, supported OS. Not a preconfigured image with whatever random stuff your hosting provider decided to do to the OS before calling it a “Webmin preinstalled” image.
Edit: I’ve marked this as the solution. Because we now know why it isn’t working. It’s not a freshly installed supported OS. Running the installer on a freshly installed supported OS will resolve this issue.