GMX

CalDAV/CardDAV setup

Two separate DAVx⁵ accounts are required (one for CalDAV, another for CardDAV) because there are no SRV records for all GMX domains. If your email address ends with .com please use the respective Base URLs below

For CalDAV, use this base URL: https://caldav.gmx.net | https://caldav.gmx.[com|de|co.uk|es|fr]

For CardDAV, use this base URL: https://carddav.gmx.net | https://carddav.gmx.[com|de|co.uk|es|fr]

Note: For .gmx email addresses please use the .net Base URL variant above.

User name: your GMX email address
Password: your GMX password; if you use 2-factor authentication you have to generate app-specific passwords (one for CalDAV, one for CardDAV) and use those instead of your normal password

Contact group method: vCard contact groups are not supported. Choose the method used by your other clients or "per-contact categories" to minimize potential problems.

WebDAV setup

You can mount folders from the GMX Cloud (formerly MediaCenter) using the DAVx⁵ WebDAV mounts feature.

WebDAV URL: https://webdav.mc.gmx.net

User name and password: same as for CalDAV/CardDAV (in case of 2FA, you need to generate a separate app-specific password again)

Some operations like video streaming won't work because the server doesn't support range requests.