GMX
From dmfswiki
Setup
Select the "GMX" option when setting up a new account.
CalDAV-Sync
- Username: your gmx mail address (example@gmx.net)
- Password: your password
CardDAV-Sync
- Server URL: https://carddav.gmx.net
- Use SSL: check accordingly
- Username: your gmx mail address (example@gmx.net)
- Password: your password