We are currently in a Hybrid setup using Office 365 with Exchange 2010 SP3. Once all mailboxes are in the Cloud and On Prem Distribution Lists have been recreated in the Cloud, is it necessary to keep any footprint of an Exchange server On Prem? We are using AD Connect to sync new users to the Cloud. Management still thinks an On Prem Exchange server is still and will always be necessary in the Hybrid setup. Your thoughts please.