Hi,
I have Exchange 2010/2013 coexistence. DNS is now pointed to 2013. Users with mailbox on 2010 are unable to open shared 2013 mailboxes from within Outlook (2010,2013). I get 'The set of folders cannot be opened. Microsoft Exchange is unavailable. Either there are problems or the Exchange server is down for maintenance'
Any ideas how to start troubleshooting this? - Thanks