Greetings,

I am in porcess of migrating my Exchange 2007 to Exchange 2013, Please find below the scenario.

Exchange 2007     Single server solution. Not published externally, only for internal emails only.

CAS URL: mail.abc.com

Have another email system hosted with ISP :     xyz.com

Objective: Migrate from Ex2007 to Ex2013

Want to publish externally xyz.com (not abc.com), will do cutover from ISP hosted to my premises, MX records will be pointed from ISP to on-premises

Exchange 2013

Configured 2 Mailbox and 2 CAS Server in Exchange 2013.

DNS: Created one split DNS for xyz.com (as the default domain is abc.com) and then configured A record for mail.xyz.com pinting to CAS NLB Virtual IP.

Virtual Directories Config: I have not done any changes to Ex2007 CAS URLs, as the old namespace is no longer required. And new namespace is configured in Ex2013.

For Ex2007 server have done only change in Autodiscover internal uri to https://mail.xyz.com/autodiscover/autodiscover.xml

Have configured below mentioned URL in Ex 2013.

owa (Internal/External) : https://mail.xyz.com/owa

ecp (Internal/External) : https://mail.xyz.com/ecp

oab (Internal/External) : https://mail.xyz.com/oab

Autodiscover (Internal uri) : https://mail.xyz.com/autodiscover/autodiscover.xml

Webservices (Internal/External) : https://mail.xyz.com/ews/exchange.asmx

ActiveSync (Internal/External): https://mail.xyz.ae/Microsoft-Server-ActiveSync

Test Scenarios:

The Autodiscover resolves if put the url in Expolrer https://mail.xyz.com/autodiscover/autodiscover.xml to the xml page, which i think is fine.

But when i run test-outlookwebservices it gives the error.

[PS] C:\Windows\system32>Get-ClientAccessServer | Test-OutlookWebServices -Identity ex2k7@abc.com -MailboxCredential
 (Get-Credential)

cmdlet Get-Credential at command pipeline position 1
Supply values for the following parameters:
Credential

Source                              ServiceEndpoint                     Scenario                       Result  Latency
                                                                                                                  (MS)
------                              ---------------                     --------                       ------  -------
2013MBX-2.bhgroup.com                mail.abc.com               Autodiscover: Outlook Provider Failure       3
2013MBX-2.bhgroup.com                mail.abc.com               Exchange Web Services          Failure       0
2013MBX-2.bhgroup.com                                                    Availability Service           Skipped       0
2013MBX-2.bhgroup.com                mail.abc.com               Offline Address Book           Failure   21010
The specified server, 2013CAS-2, isn't a Client Access server.
    + CategoryInfo          : InvalidArgument: (:) [Test-OutlookWebServices], TestWebServicesTaskException
    + FullyQualifiedErrorId : [Server=2013MBX-2,RequestId=904addf0-7e3d-4f1f-af13-ed23b8a43b54,TimeStamp=8/23/2015 8:54
   :09 PM] [FailureCategory=Cmdlet-TestWebServicesTaskException] 7394F15C,Microsoft.Exchange.Monitoring.TestOutlookWe
  bServicesTask
    + PSComputerName        : 2013cas-1.bhgroup.com

The specified server, 2013CAS-1, isn't a Client Access server.
    + CategoryInfo          : InvalidArgument: (:) [Test-OutlookWebServices], TestWebServicesTaskException
    + FullyQualifiedErrorId : [Server=2013MBX-2,RequestId=904addf0-7e3d-4f1f-af13-ed23b8a43b54,TimeStamp=8/23/2015 8:54
   :09 PM] [FailureCategory=Cmdlet-TestWebServicesTaskException] 9B8D136F,Microsoft.Exchange.Monitoring.TestOutlookWe
  bServicesTask
    + PSComputerName        : 2013CAS-1.abc.com

Also 2013 Exchange users are not able to see OAB, it is  failing while accessing Address book. Says Outlook is not connected or Offline. 

Certainly i have misconfigured the Virtaul Directoies.

Kindly suggest if the above config is fine or any inputs will be appreaciated.

Thanks in advance.