I cannot access OWA from a browser anymore. Accessing https://localhost/owa gives me HTTP error 404.0. I have tried re-creating the OWA virtual directory using ECP but this has not helped. Some other references suggest re-installing CAS role however our Mailbox and CAS are on one server and I believe a full re-install is the only way achive this. This seems like a massive job to be unless I am mistaken. I there another way to fix this?

Hello

tip: check in iis site ip and port binding.

Hi,

Make sure that you are not mistaken on any of the settings at IIS: https://technet.microsoft.com/en-us/library/gg247612%28v=exchg.150%29.aspx?f=255&MSPPError=-2147217396

Hi,

Please try the following steps:

1. Run the following cmdlet to change the authentication method of the "owa" virtual directory to Windows authentication:
set-Owavirtualdirectory -identity "E15MBX\owa (Exchange Back End)" -WindowsAuthentication $True -Basicauthentication $false -Formsauthentication $false

2.Run the following command on both the Client Access and Mailbox servers to restart Internet Information Services (IIS):
iisreset /noforce

For more information about this, please refer to:

https://support.microsoft.com/en-us/kb/2778897

Regards,

Have a look at the IIS logs to make sure that the requests are hitting the default web site.

Further to what Sneff_Gabor has already said:

See if the default web site is configured to listen to SSL/HTTPS requests on a particular IP address (if it is, then you can't use the name 'localhost', as this usually means 127.0.0.1).  It is usually configured to listen on 'All Unassigned' IP addresses.

Make sure that the SSL/HTTP port has not been changed to something other than 443.