When you run the Hybrid Configuration wizard in Exchange Online or Exchange Server 2013, you receive the following error message:
HCW8025 You must remove any Exchange Server 2010 Hub Transport servers from the TransportServers parameter before you upgrade to a hybrid configuration in Exchange 2013.
When you run the Hybrid Configuration wizard in Exchange Server 2013 or a later version of Exchange, the Exchange 2010 servers must be removed from the hybrid object. The wizard should do this automatically. But if it doesn't, follow the steps in the Solution.
To resolve this issue, follow these steps:
Open the Exchange Management Shell.
Run the following command to clear the Exchange 2010 transport servers from the hybrid configuration: