Hi, I recieve the above subject error when accessing the CAS server on the Exch 2010 box. After searching the resolution is to add the “Exchange Trusted Subsystem” group to the local admins group on the exch 2007 box. But Exchange 2007 is installed on the DC and obviously you cant achieve this. Any ideas would be appreciated - thanks. Also added rights for “Exchange Trusted Subsystem” in IIS Default website still no joy.

Hi, Yes, add “Exchange Trusted Subsystem” group to the local admins group on all the Exchange 2007 Servers. For this issue, I recommend you to install another Exchange 2007 Server and then move all the mailbox and data to the newly installed computer. We need to dismiss the Exchange on domain controller. Besides, I recommend you to run ExBPA to have a health scan and then post the error information here for further troubleshooting. Regards, Xiu