Generally it is not recommended to install anything along Mail-in-a-Box since it promises to work with one command which would become very complicated if everyone would have different configurated boxes. So if you are going to install anything along it you are on your own.
See this list for good VPN server software or this script for a one command OpenVPN installation.
You might want to consider using a different cloud server for things different from Mail-in-a-Box. I am also running Mail-in-a-Box on a separate server so it doesn’t break
There are very cheap ones out there. Maybe take a look at LowEndBox.
I must warnning you that adding additional apps. in your MiaB server if not officially supported hereI Then try it if you wish but after you have created an snapshot of your server and if finally you like to stay with, do it at your own risk!
Having that said I have OpenVPN installed in several MiaB servers from long time and no issues! and I’m extremely happy with that as save me of the cost and maintenace of an additional CLOUD server just for that.
Here you have some guidelines that will help you to easily build you own:
Double-check you have added a custom port for OpenVPN to your UFW table . By default 1194/udp
Reload UFW with sudo ufw reload
After having the first client working well you can run the script again to add more users, remove some of them or even completely uninstall OpenVPN.
Recommended to reboot the server when done.
Note: Some CLOUD server providers enable by default some kind of NAT, security groups, firewall … If that’s you case don’t forget to open the told OpenVPN port there, too.
Option 2)
Use dedicated server and use the told ‘script’ there. You can get an small one at VULTr for just 2.5 USD / mo.
Please, change this post to the Unsupported Modifications category (if possible)
Hope this helps!
Enjoy It!
Edited 170422 19:16 CEST: Noticed now that @pxl recommended you the same ‘script’. Nice!