During the installation of Essential Business server, in an Existing domain after unsucessful install if you try to change the names of the Management server during setup it gives you a message that the “old server name” could not be found.
Cause: this issue is caused due to the MMSconfiguration in AD stores the names of the Management, Messaging and the security server. You can try changing the entries there, however it may or may not work.
EBS team blog recommends the following. If you delete the management, messaging and the security server accounts from AD then use Adrestore to undelete those accounts and try either to remove EBS by running the wizard again. This should remove the server entries gracefully.
In cases where you cannot use Adrestore or it does not work. You could delete the MMSconfiguration container under Active directory.
CN=MMScontainer, CN=services, CN=Configuration,DC=domainname,DC=net
note: before you delete any container in AD make sure that you take a system statebackup and delete.