Exchange 2013 co-existence with Exchange 2010 proxying issue.

Hello,  

I am testing Exchange 2010 and Exchange 2013 co-existence in my test lab at the moment, with a view to migrating our production environment to 2013 later in the year.  

The lab is setup, and the problem I'm having is that internal Outlook clients cannot open their respective mailboxes once the 2013 CAS server is introduced into the mix.  

 The setup is listed below:  

EXCHANGE 2010 Servers  

TESTLABEXCH01 - CAS,HT,MBX - Exchange 2010 SP3  

TESTLABEXCH02 - CAS,HT,MBX - Exchange 2010 SP3  

Both servers are part of a CAS Array - casarray01.testlab.local  

Both servers are part of a DAG - DAG01.testlab.local  

RpcClientAccessServer on all 2010 databases set to casarray01.testlab.local  

The A record for casarray01.testlab.local points to the IP of the VIP of a load balancer.  

The loadbalancer serves the following ports: 25,80,443,143,993,110,995,135,60200,60201  

OutlookAnywhere is enabled on both servers:  

ClientAuthenticationMethod : Ntlm  

IISAuthenticationMethods   : {Basic, Ntlm}  

Internal and external mail flow works without issue before the 2013 server is introduced. 

Internal and external client access works without issue before the 2013 server is introduced. 

Part Two to follow.....