
This problem is not resolved by removing the outlook profile, clearing credentials from credentials manager I have even tried different machines and recreating user profiles.

Closing and reopening Outlook sometimes fixes the issue, other times its recovery is longer than the users patience at which point the user has normally given up and rebooted the machine. Most of the time this does not work and the user ends up locking themselves out of their AD account. Sometimes if the user waits a couple of minutes you can re authenticate, entering username&password or if already filled in pressing OK. I have not been able to find the cause as yet other than outlook is unable to recover/reconnect with exchange if the computer has been to sleep. In our environment, if the machine goes to sleep and is woken up ie comes back to computer after lunch break or a meeting, users are prompted with an Outlook authentication window (username + password prompt). I've been investigating possibly the same issue with my windows 10 desktops for a while now and we are also using Exchange on prem with Office 365 subscription(MS Office applications).
