We are migrating from Exchange 2010 to 2016 and are in a state of coexistence. I'm unable to launch any Exchange 2016 mailboxes from Outlook 2010 and 2016. I am able to open up the Exchange 2016 mailbox from Outlook Web Access. When I try to launch the mailbox from Outlook I get the error "Cannot open your default email folders. Microsoft Exchange is not available. Either there are network problems or the Exchange server is down for maintenance". Any suggestions? I have not cut over autodiscover to Exchange 2016 yet. Is there something I need to configure with Outlook Anywhere for Exchange 2016?