I have created the app registration for Service Desk following the directions on this link https://help.servicedeskplus.com/configure-azure-as-authentication-server

When trying to click save on the incoming mail settings I keep getting error of One of the mandatory valure for mail serer details is set as NULL.  Hence the mail server settings cannot be updated.  It keeps removing the client secret every time I click save. Also an error about configure error folder to ensure uninterrupted mail fetching but nothing happens.  What am I doing wrong here?