Calendar functionality was integrated into Thunderbird with version 78.0. If
you don't see any options to add or view a calendar, please make sure to update
Thunderbird to the latest version.
Click on the menu icon in the top right corner of the
In the New submenu, select
Select the On the Network option and then
Next to continue.
In the User name field, enter your GMX address.
In the Location field, enter the path https://caldav.gmx.com/begenda/dav/your GMX email
Example: For the email address email@example.com, you enter https://firstname.lastname@example.org/calendar/ as the
Your GMX "My Calendar"
default calendar is now synchronized with Mozilla Thunderbird.
Click Find Calendars.
Enter the password for your GMX
Account and click on Sign in.
Under Calendar Type choose CalDAV.
Under Properties give the GMX
Organizer a name and, if applicable, a color. Appointments
from this calendar will later be displayed in the color. Click