panaro

Thanks a lot, but it’s working now without this solution. Definition update for sure.

Same here. Win 10 Home 21H1 19043.1055 Kaspersky Internet Security 21.3.10.391(b) Mail and Calendar app can’t sync outlook.com and Office 365 accounts. Gmail and Exchange ActiveSync works. If I turn off KIS Web Anti-virus, everything works fine. It started today or just a few days ago. I can sync these accounts on another PC, where I use Windows Defender instead of KIS.