Currently:- Two active directory sites.- AD Site 1: hubcasand mailbox - diferent servers.- AD Site 2: hubcasand mailbox - same server.- User1 has mailbox in AD-Site1- User2 has mailbox in AD-Site2Questions:1. When anUser2 logon in to OWA-AD-Site 2,is OK.2. When anUser2 logon in to OWA-AD-Site 1, we get the next message:Error: Outlook Web Access is not available. If the problem continues, contact technical support for your organization and tell them the following: There is no Microsoft Exchange Client Access server that has the necessary configuration in the Active Directory site where the mailbox is stored.any comments ?

Please see:http://msexchangeteam.com/archive/2007/09/10/446957.aspxHow Exchange Server 2007 CAS Proxying works for Outlook Web Access (OWA) If there is a Client Access server that is closer to the user's Mailbox server, Exchange 2007 determines whether the Client Access server has the InternalURL property configured on /owa virtual directory Exchange and if the authentication method is Integrated Windows authentication. If so, the user is proxied to the Client Access server specified by the InternalURL property. Otherwise will return an error message to the client if could not find the best CAS. Error: Outlook Web Access is not currently available for the user mailbox that you are trying to access. Please try again in a few minutes. If the problem continues, contact technical support for your organization and tell them the following: The available Microsoft Exchange Client Access servers in the target Active Directory site are not responding. If the Integrated Windows authentication is not set on the Second CAS, it will return an error message to the client. Error: Outlook Web Access is not available. If the problem continues, contact technical support for your organization and tell them the following: There is no Microsoft Exchange Client Access server that has the necessary configuration in the Active Directory site where the mailbox is stored.

Hi, Although Windows Authentication was enabled on both CAS-Sites the issue still appear. the solution is verify if KERBEROS authentication was enabled to the IIS web site. for IIS 6.0 or IIS 5 the solucion is in: http://support.microsoft.com/kb/215383 run the next command: cscript adsutil.vbs set w3svc/NTAuthenticationProviders "Kerberos" to Windows 2008 the solucion is on: http://technet.microsoft.com/en-us/library/cc754628(WS.10).aspx run command: appcmd set config /section:windowsAuthentication /-providers.[value='Kerberos'] Regards.

Hi Johan, Thank you for your sharing. It's great. By default,after you set the Integrated Windows authentication, the negotiate authentication is available, and the proxy should be work. But if it doesn't work, we could check the IIS authentication method as you just done. We also could use netmon to capture the network traffic to analyze the issue. A related article: IIS logging for Windows Integrated authentication http://support.microsoft.com/kb/969060/en-us Thanks for your feedback. :) -Elvis