If you want to remove a GMX account, you can easily do that in the Settings page of your account.
I’ll show you below how I managed to close my profile using a desktop computer:
1 Go to GMX.com
and log in by entering your email address and password on their site.
2 Select My account in the left menu
3 You’ll arrive in GMX’s self care center
where you will see a Delete account option.
4 Click on the Remove account link
5 Last step – Enter your password and Save changes
A message appears: Dear GMX customer, your account has successfully been deleted.
You’ll be logged out automatically and your account is gone. Mission accomplished!