Hi,

we have following problem. We have a mixed multi-domain one-forest AD environment. We also have still a mixed exchange 2007 / 2013 environment. We also have different CAS Servers for 2007 SP3 (RU15) and 2013 (CU8) in europe and one 2007 SP3 (RU15) CAS Server in China, because of bad connection to Europe. For the Migration to 2013 in Europe we installed a wildcard-certificate *.xyz.com and used the Set-OutlookProvider EXPR -CertPrincipalName msstd:*.xyz.com, so the wildcard certificate is accepted. Everything in Europe works fine, inside and outside also between exchange 2007 and 2013 (both CAS Server 2013 and 2007 use the same wildcard certificate). But since the change of the Set-OutlookProvider EXPR we are facing problems with our CAS Server in China, because this server has a different non-wildcard certificate and a different domain name (cas-server.xyz-china.com instead xyz.com). Now we have the problem that this Chinese CAS server the Outlook Anywhere does not work anymore and prompts always for the username. As I see it is because of the EXPR change. Is it possible to set the the Outlook-Provider EXPR per Cas-Server ? (They also have their own Autodiscover on this front-end server). Because I see that the Outlook-Provider can only be stored forest-wide.
If not the other solution would be to register the chinese cas server in our xyz.com domain and use the same wildcard certificate on this system right ?
Any help would be appreciate.

Yes setting the EXPR value is most likely the cause of your issue.  When you set this value you are telling Outlook to only accept connections from connections that have the cert with the subject name you specify here.

Unfortunately, based on my experience I believe this is an organization wide setting and cannot be configured on a CAS by CAS basis (If I'm wrong someone please keep me honest :)).  

So the only option would you have is to change all the URLs to be on *.xyz.com domain.  There's no need to change the domain the server actually resides on.  The other option would be to purchase a UCC Cert with all the names you need and apply to all your CAS servers and reset the EXPR value.