If your CAS fails due to an irreparable hardware problem; follow these steps to repair it:
- Reset the client access server’s computer account within the Active Directory Users and Computers console. Do not delete the account.
- Install Windows on the new server and then install the same OS version as the failed server.
- Rename the server to match the name the CAS used and join the server to your domain.
- Depending on the version of Exchange Server and service pack you were running, insert the corresponding installation media into the server and run the following command:
Setup /m:RecoverServer /installwindowscomponents
- After the command runs, Setup will install the Exchange binaries and use the information stored in Active Directory to rebuild your CAS.
Note: This technique can also be used to rebuild any other Exchange Server roles, except for the edge transport server.
These steps work well to rebuild a failed client access server; however, there is a major caveat. This method only works if the server is running a standard configuration, which is unlikely since many organizations personalize their Outlook Web Access interface.
Using these steps will rebuild the CAS to a functional state, but any OWA customizations will be lost. This happens because Setup copies the Exchange binaries from the installation media, not your customized files.This i have tested and working solution for CAS server Role.