The reason for the configuration failure is due to SMTP not being enabled for the sender address. Hence, we request you check the below,
>> Please log into the o365 account as the Admin and access the link, https://admin.microsoft.com/AdminPortal/Home#/users
>> Click on the user account -> click "Mail" -> under Email apps click on "Manage email apps"
>> Please check if SMTP is enabled or not. If not enabled please enable it. If already enabled, disable it once and enable it again.
After the above process, try the configuration in TeamInbox.