Very strange issue... Exchange 2013 CU8, Sharepoint 2013, Outlook 2013.

Exchange - 2 CAS, 2 MBX

Sharepoint - single server

We can successfully access OWA and Outlook is able to successfully configure itself. As soon as a site mailbox configuration is completed Outlook is no longer able to configure itself (can't contact Exchange server error). OWA/mail flow still works fine. Outlook that was configured prior to site mailboxes continues to work fine, however, all new Outlook configurations fail (manual or automatic). Site mailbox never shows up in OWA or Outlook, however, sync reports no errors and "show in outlook" is selected. Able to send mail to the site mailbox and access it from SP (but not OWA/Outlook). I believe the issue is due to authentication on virtual directories because when I attempt to configure Outlook on a CAS I receive a pwd prompt (that never accepts the pwd) and as soon as Virtual Directories are reset Outlook is able to configure itself but site mailboxes are then broken. Outlook on any other server/desktop just reports an error that it can't contact Exchange server.

MCA reports the following:

Autodiscover POST request to potential Autodiscover URLs: An HTTP 401 Unauthorized response was received from the remote Unknown server...

Password is correct, account is unlocked, etc. Not sure what do to here...