Uninstall/Remove Old Exchange Server from AD

On Domain Controller, Open ADSIEDIT

Right Click on ADSIEdit and Click Connect to

Connect to Configuration and Ok

Navigate to the following objects and Delete them.

CN=Configuration,DC=Domain,DC=Com -> CN=Services -> CN=Microsoft Exchange

CN=Configuration,DC=Domain,DC=Com -> CN=Services -> CN=Microsoft Exchange Autodiscover

Force the Active directory Replication.