Account WEB.de Folder "unbekannt"

Hello, at the moment I am testing the Demo of eM Client. I have an email account from Web.de.
Everything works fine in eM Client. All folders from my Web.de account are shown in eM Client, also the folder “unbekannt” (I added the folder “unbekannt” to the Favorites too). EM Client checks all folder and I see the number of the new mails beside each folder. But since some days eM Client checks not automatically the “unbekannt” folder. It checks only the folder for new mails, when I click on it. Posteingang folder works finde, but “unbekannt” folder not. I don’t know what preference I should change, that eM Client checks this folder automatically again. I hope someone can help me.