error message when refreshing - concerns calender synch (which I do not use)

Everytime when pressing refresh to receive new messages emClient always shows an error message stating that the refreshing concerning My Calender has failed. The thing is I don’t even use the calender and could go well without the functionality as a whole. 
Can I disable it or somehow get rid of that error message?

Translation of picture:
[CalDAV] Synchronising Calender has with the following error: ()

Yes, go to Menu > Tools > Accounts and click on your GMX email account. In the General tab scroll down to Services and untick CalDAV.

Thanks a ton, that worked perfectly!!!