Hi Salehice,
Thank you for your question.
I agree with Hinte, we could perform a disaster recovery by the following link:
https://technet.microsoft.com/en-us/library/dd876880%28v=exchg.150%29.aspx
In addition, if there are no effects when we remove it and we just want to move it from server menu, we could refer to the following steps:
1.Run ADsiedit.msc in RUN, then navigate
Configuration [<domainController>.contoso.com]> CN=Configuration,DC=contoso,DC=com> CN=Services> CN=Microsoft Exchange> CN=<OrganizationName> CN=Administrative Group> CN=Exchange Administrative Group>CN=Server
2.We could check if CAS server is existed in this container, we could remove it
Notice: when we run ADsiedit.msc, we should make sure another Exchange server are running without any problems. In addition, we should backup AD database before we modify AD configured information, I suggest we ask MS engineer for help.
If there are any questions regarding this issue, please be free to let me know.
Best Regard,
Jim