Outlook anywhere, auto discover and multi CAS's that are not an array

Question

exchange forest: 4 X exchange 2010 SP3. root is HQ, sites are B, C & D.
I set up auto discover by a SRV record in DNS and auto discover works perfectly for HQ users. 
 But when a user from Site B  tries it, the delivered XML sent to  their Outlook will redirect that person up to the Site B's server where it fails due to a mutual
validation error. This is because Outlook is expecting the SSL cert from HQ but gets Site B's. 
In exchange 2007 this would not be a problem as there were no redirects, the  client access server that hosted the autodiscover service would fetch the email and send it onto outlook from Site B's mailbox. So what I am looking for is either a setting that
will stop this redirect or a work around, one that I can think of is to turn off Outlook Anywhere on other CAS’s, leaving it only running on the root, HQ.
I’m not worried about capacity we have at most at any one time 10 Windows Outlook users outside the office as all the rest the remote users are either using IMAP or ActiveSync.  So is shutting down outlook anywhere on B,C &D. Or is there a setting
that I can change on HQ to make it that it always goes through HQ.
thanks

Answer 1

Hi,
Firstly, I’d like to explain, internal users in site B can always find the CAS serve in site B. Because Outlook clients firstly find the SCP records of the in-site list.
To make them use HQ site SCP record for its Autodiscover requests, we can set Site Affinity: 
Set-ClientAccessServer -Identity "CAS in site HQ" –AutodiscoverServiceInternalURI "https://internalsitename/autodiscover/autodiscover.xml" -AutodiscoverSiteScope "site B",”site HQ”
http://technet.microsoft.com/en-us/library/aa998575(v=exchg.141).aspx
The previous command only ensures the following:
• If an Outlook client is a member of the HQ Active Directory site, it will use the HQ SCP record for its Autodiscover requests.
• If an Outlook client is a member of the Active Directory site B , it can use the HQ SCP record for its Autodiscover requests.
For more information, you can refer to the partition named configuring the Autodiscover service to use site affinity for internal communication in the following article:
http://technet.microsoft.com/en-us/library/jj591328(v=exchg.141).aspx#BKMK_ConfiguringSiteAffinityInternal
For external users, we can make the host name Autodisocver.domain.com points to the IP address of CAS sever in site HQ.
If you have any question, please feel free to let me know.
Thanks,
Angela Shi
TechNet Community Support