If you do not have your own domain within mail.com you should be able to use Login with Email and Password (be sure to generate an app password if you use 2FA).
Alternative setup method
If the above mentioned Login method does not work you can also use two separate DAVx⁵ accounts (one for CalDAV, another for CardDAV).
For CalDAV, use this Base URL:
For CardDAV, use this Base URL:
User name: your mail.com email address
Password: your mail.com password; if you use 2-factor authentication you have to generate app-specific passwords (one for CalDAV, an extra 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.
You can mount folders from the mail.com Cloud using the DAVx⁵ WebDAV mounts feature.
WebDAV URL: https://storage-file-us.mail.com/
User name and password: same as for CalDAV/CardDAV (in case of 2FA, you need to generate a separate app-specific password again)
Hint: Videos can't be directly streamed due to a limitation of the server