CAS Proxy problem

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I have a site-A and site-B. site-A has CAS/HT and mbx server and site-B has mbx/cas/ht. When i is enter the internal URL of site-B to access the mailbox host in site-b site, i could access it without a problem. so is the case in site-A.

Now i have set the site-b cas to authentication method to Integrated Windows Authentication. The internal owa URL on the site-B is unchanged.

Only siteA-CAS has external URL specified. it is set to, it's internal URL is set to as nearly 50% of the internal use use only OWA.

When a use from siteB access the mail thru either from siteA or from internet, i see the below info in the event viewer.

Log Name: Application

Source: MSExchange OWA

Date: 11/12/2010 2:43:20 PM

Event ID: 41

Task Category: Proxy

Level: Error

Keywords: Classic

User: N/A



The Client Access server "" attempted to proxy Outlook Web App traffic for mailbox " /o=Contoso/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=Test1" . This failed because no Client Access server with an Outlook Web App virtual directory configured for Kerberos authentication could be found in the Active Directory site of the mailbox. The simplest way to configure an Outlook Web App virtual directory for Kerberos authentication is to set it to use Integrated Windows authentication by using the Set-OwaVirtualDirectory cmdlet in the Exchange Management Shell, or by using the Exchange Management Console. If you already have a Client Access server deployed in the target Active Directory site with an Outlook Web App virtual directory configured for Kerberos authentication, the proxying Client Access server may not be finding that target Client Access server because it does not have an internalUrl parameter configured. You can configure the internalUrl parameter for the Outlook Web App virtual directory on the Client Access server in the target Active Directory site by using the Set-OwaVirtualDirectory cmdlet.

Event Xml:

<Event xmlns="" >
<Provider Name=" MSExchange OWA" />
<EventID Qualifiers=" 49152" >41</EventID>
<TimeCreated SystemTime=" 2010-11-12T09:13:20.000000000Z" />
<Security />
<Data>/o=Contoso/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=Test1</Data>


Busbar [MVP]

configure Site B to use windows integrated authentication and reset IIS, force AD replication and try againRegards, Mahmoud Magdy Watch Arabic Level 300 Videos about Exchange 2010 here: Read pretty advanced Exchange stuff I post here:, follow my blog: , corp blog:, Follow me on twitter and if you Liked my post please mark it as helpful and accept it as an answer


I believe this seeting is only for OWA? or for all Virtual Dir?. I have already set the windows integrated auth for the owa and reset the IIS but with not success !!


Create new New-ClientAccessArray for each CAS for Each site. Then assigned RpcClientAccessServer, for each Mailbox database. Set DNS record.

Then Run bottom task. Check Internal and External url, and be Shure, there is no basic authentication on proxy site:

Get-WebServicesVirtualDirectory | fl Server,Name,InternalUrl,InternalAuthenticationMethods,ExternalUrl,ExternalAuthenticationMethods

Get-OwaVirtualDirectory | fl Server,Name,InternalUrl,InternalAuthenticationMethods,ExternalUrl,ExternalAuthenticationMethods

Get-EcpVirtualDirectory | fl Server,Name,InternalUrl,InternalAuthenticationMethods,ExternalUrl,ExternalAuthenticationMethods

Get-AutodiscoverVirtualDirectory | fl Server,Name,InternalUrl,InternalAuthenticationMethods,ExternalUrl,ExternalAuthenticationMethods

Get-RpcClientAccess | fl Server,Responsibility,EncryptionRequired,

Get-ActiveSyncVirtualDirectory | fl Server,Name,InternalUrl,InternalAuthenticationMethods,ExternalUrl,ExternalAuthenticationMethods,BasicAuthEnabled,WindowsAuthEnabled

Brian Desmond -MVP-

OK so let's take a step back.

First, the InternalUrl for SiteA should be https://<server.fqdn>/owa as was the default. It has nothing to do with the location the user is accessing OWA from.

Second, can you please post the URL and AuthN configuration for Site B? You can do a Get-OwaVirtualDirectory | fl server,*authen*,*url*

My Book - Active Directory, 4th Edition
My Blog -

Allen Song


Is it the Exchange 2010 in each site? If it's Exchange 2007 in Site B, you have to copy the hightest-versioned folder from an Exchange 2007 CAS in the destination Active Directory site from the %installpath%\ClientAccess\OWA\ folder to the same path on the Exchange 2010 CAS to make the proxy work.


Allen Song
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