The Script itself works fine, but when you click X-notifier you'll be redirected to your GMX Dashboard. I'd prefer to get directly to the Mail section to see the inbox and the folders.
Therefore, the redirection link would only needed to be changed to https://navigator.gmx.net/navigator/show?sid=[...]#mail instead of sid=[...]#home
I tried to do it by myself, but I didn't get it working. :-/ Any suggestions?