We are not really experts on such specific configurations for SOGo but you could install an app and put it into debug mode if you are a developer using the cloudron cli tool with cloudron debug --app <appdomain> then login to the app with cloudron exec --app <appdomain> and start the app with /app/code/start.sh Then the whole filesystem becomes writeable and you can see how to tweak the configs as you want. If you have found a working combination, let us know and we can see how we can change the app package to allow such config to be persistent and updateable.
@nebulon Thanks guys, it works. Your support is good! I don't know how many people use cloudron as a private replacement of cloud services, but I think if you get all these details down and everything just works, there's a market for that 🙂