RMS Shared Identity user FederatedEmail.4c1f4d8b-8179-4148-93bf-00a95fa1e042 Not Found

Having removed an Exchange Server (and arbitration mailboxes), reinstalling a second  Exchange 2010 can be problematic. The deletion of the discovery mailbox will mean that the reinstallation of your Exchange 2010 server will fail. Run the following command:

[PS] New-Mailbox -Arbitration -Name FederatedEmail.4c1f4d8b-8179-4148-93bf-00a95fa1e042 -UserPrincipalName FederatedEmail.4c1f4d8b-8179-4148-93bf-00a95fa1e042@<Default_Accepted_Domain>

This should allow you to now rerun the installation program without failure.