Removing and re-adding the account using the standard Sign In method will resolve this error. My concern is that MS will force modern authentication soon, and switch off basic authentication. expert Outlook tips by FixTechGuide Is there some kind of setting within O365 that’s forcing Outlook to use basic authentication ? Other apps are using modern authentication perfectly well, including Team The sync will fail if the groups you selected to load users from no longer exist in Azure AD. Typi...