Hi @EnterpriseArchitect ,
Supposing your organization has been running in a hybrid configuration, if you don't need to manage your users synced from on-premises, you can remove the Exchange server on-premise. Otherwise, you do need to remain at least one Exchange server on-premise. For more details, hopefully you can find the scenarios in the article below helpful:
How and when to decommission your on-premises Exchange servers in a hybrid deployment
(Note: if you just want to keep an on-prem Exchange for recipient management, you can be able to shut down the last Exchange server and manage recipients using Windows PowerShell, see Manage recipients in Exchange Hybrid environments using Management tools.)
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