Domain users are unable to use the "Out of Office" Assistant for Outlook 2010/2013. Receiving "server unavailable errors". Also, receiving Certificate popups for previous Exchange server that crashed. Some users not able to "see" other users calenders. Need help resolving as the present Exchange server is a rebuild of the one that crashed and it is questionable whether the server was properly "stood up". Can I get some pointers on where to start looking please?