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!

How did you increase the MaxTokenSize?

Generally you would add the following keys to the 2010 CAS  ( not the 2013) and reboot:

New-ItemProperty -Path HKLM:\System\CurrentControlSet\Services\HTTP\Parameters -Name "MaxFieldLength" -PropertyType DWORD -Value 65534

New-ItemProperty -Path HKLM:\System\CurrentControlSet\Services\HTTP\Parameters -Name "MaxRequestBytes" -PropertyType DWORD -Value 16777216

I added the keys you just listed to the Exch2013 CAS/MBX servers and rebooted.  I did not add anything to the 2010 CAS because if I go to that URL on the 2010 CAS I do not receive an error.

Another interesting thing is if I go to the autodiscover URL on the 2013 CAS like this:

https:\\2013cas.fqdn:444\autodiscover\autodiscover.xml, this works fine.  Port 444 appears to be the back end mbx virtual directory.

I added the keys you just listed to the Exch2013 CAS/MBX servers and rebooted.  I did not add anything to the 2010 CAS because if I go to that URL on the 2010 CAS I do not receive an error.

Another interesting thing is if I go to the autodiscover URL on the 2013 CAS like this:

https:\\2013cas.fqdn:444\autodiscover\autodiscover.xml, this works fine.  Port 444 appears to be the back end mbx virtual directory.

Right, but that's the issue. If you are proxied to the 2010 CAS from 2013, you see the error yes? If so, then I would set the reg keys on the 2010 CAS.

Now having said that, if OWA works, I am not confident this will work. Generally, the token bloat issue will afftect OWA as well, but worth testing.

If it doesn't solve it, then remove the keys if you want.

Greetings!  I will try this suggestion.  My reason for not focusing on the Exch 2010 CAS was that I do not have the issue if I connect directly to it.  It is only when I proxy through the Exch 2013 - leading me to believe the problem is with the 2013 servers.  I will add the entry to the 2010 CAS and see if this makes any difference.

Greetings!  I will try this suggestion.  My reason for not focusing on the Exch 2010 CAS was that I do not have the issue if I connect directly to it.  It is only when I proxy through the Exch 2013 - leading me to believe the problem is with the 2013 servers.  I will add the entry to the 2010 CAS and see if this makes any difference.

The real culprit is Windows 2012 versus 2008.  Hopefully the reg tweaks will make a difference. At a minimum, they wont hurt.

I was able to resolve this issue, as far as I can tell, by doing what you suggested as well as some other registry entries as outlined in this HP support document (of all places....):

http://support.hp.com/us-en/document/c04471829?openCLC=true

Thank you very much!

• Edited by JoeCastle 7 hours 9 minutes ago

I was able to resolve this issue, as far as I can tell, by doing what you suggested as well as some other registry entries as outlined in this HP support document (of all places....):

http://support.hp.com/us-en/document/c04471829?openCLC=true

Thank you very much!

• Edited by JoeCastle Sunday, February 22, 2015 4:42 AM
• Marked as answer by Andy DavidMVP, Moderator 22 hours 37 minutes ago