The setup is as follows
Windows Server 2012 R2 running Exchange 2013 CU5 - CAS Role
Windows Server 2012 R2 Running Exchange 2013 CU5 - Mailbox Role
Published via Web Application Proxy, using ADFS on Server 2012 R2
The problem
Browse to https://webmail.contoso.com/owa - log into OWA as myself this works fine - try and open another users mailbox that i have full access to, i get HTTP 400 bad request
If i browse to https://servername and perform the same procedure it works. This leave me to the conclusion that the Web Application Proxy server / ADFS server is at fault
this KB article is not relevant in this instance, as I can resolve the names correctly;http://support.microsoft.com/kb/2770796/en-au
Any suggestions
Thank you.