Greetings! I am in the process of standing up some Exchange 2013 hybrid servers in our Exchange 2010 environment. Both of these servers host both CAS and MBX roles. They are hybrid licensed which as I came to find out means they cannot host any mailboxes with this license mode; not an issue as we currently do not plan on migrating any users to Exchange 2013 on premise, just to O365.
Here is my issue. With my account only (so far), when I browse to mail.domain.com\autodiscover\autodiscover.xml I receive an error 400 - BAD REQUEST. This happens for both the internal and external URL. OWA and ECP both work fine. I tested with some other accounts and they get the expected 600 response. I have noticed that with my account, when using Outlook Anywhere off the network, this autodiscover issue results in free/busy not functioning.
When I browse to the autodiscover.xml on our current Exchange 2010 CAS server, I do not get this error 400 so it seems to be just with the new Exchange 2013 servers. I did research into this error and came across some suggestions to increase the MaxTokenSize in case it is an issue with large kerberos tickets for my account but this did not alleviate the issue.
Looking for some suggestions on where to look next. Thank you in advance!