I've already opened the port 80. It worked perfectly, but after some changes it left working. Webmin runs on a Raspberry Pi with Raspbian.
1. I tried to solve an ip issue, because my router changed my ip so quick that I had to update my ip on my Webmin server every time it changed. img1
2. So I decided to change the ip to 127.0.0.1 in all of my servers. Like this:
img2
3. Then, cause now I could't access to my server from outside of my LAN. I tried to reset my eth0 ip again as it was in all of my servers (as 192.168.1.89), but it didn't work. I still can't access my http from outside.
4. I waited my eth0 ip to change to update it again (to put it instead of 127.0.0.1), but didn't work. I tried to do it like this: img3
As I said, it worked perfectly before changing the ip to 127.0.0.1, because my normal ip changes too fast (every 7 or 10 mins). I can access to my http server but only from my LAN.
Well, finally I found the solution. The problem was nothing about my Apache or Webmin configuration. It was about a problem with my router. Apparently it had a bug: The DMZ seemed as activated, but it really didn't (my router is a HUAWEI HG659).
Also, if you get this kind of problem, you should first check what ports are being used by your computer, and check if you have any firewall or program blocking that port.
