Many errors since I use the soft, they come every day

Since I am working with EMClient, I keep receiving these error messages ?

[CardDAV] Subfolder synchronization for folder “renaud@online.de” failed due to the following error: LGI-0003 Categories=ERROR Message=‘Unknown problem: “renaud@online.de”.’ exceptionID=-1148541999-35981143

It is not making the software not work, its works properly, so why those warnings ?

Thank you.