"Hosting server" is the unique name of the server where your hosting package is stored on. It always is designXX.letzebuerg.net
For some tasks and configuration you may need to access the hosting server directly and not via your domain name. To find out what it's name is, please follow one of the following methods:
Via billing system
In the left menu, click on "Services" and then select "Linux cPanel Hosting" in the dropdown list.
Select the corresponding hosting package from the listed services to open the "Details" page. At the top of the page you find a "Your hosting server is: " box with the server name.
In the welcome email
In the email with your cPanel login details the hosting server is listed several times. Generally the hosting server name does not change throughout your service's lifetime.
After logging into cPanel, in the left-hand "Statistics" menu you find "Servername". Add ".letzebuerg.net" to the listed name for the full web-accessible server address.