Office 365 - Tenant sync and mailbox migration

[gjuskrome]

Could anyone confirm the following is possible and supported?

Exchange 2010 (and AD environment, of course) synced to O365 tenant. Migration of all mailboxes into the cloud and then completely cut the connection between on-premise and O365, so that the mailboxes in the cloud are... in the cloud only.

And then, creating the sync with Azure AD of the same tenant with a completely new AD on-premise forest (that doesn't have Exchange server)... I guess up until here is OK right?

Now the problem is... that the tenant already IS SYNCED to the new on-premise AD... so can I sync it to Exchange and different on-premise AD at the same time, migrate mailboxes and cut the connections between Exchange (and AD) and leave only sync in place between tenant and new on-premise AD?

Thanks :)

[#2]

@gjuskrome 

Below article should help answer your question about having sync performed from different on-premises AD, you can look for the right scenario that matches your topology

https://docs.microsoft.com/en-us/azure/active-directory/hybrid/plan-connect-topologies

And I am not sure about your reason for syncing with new on-premises AD, but you can always leave the accounts as cloud only accounts.

https://techcommunity.microsoft.com/t5/Security-Identity/Convert-On-Prem-AD-Users-from-Office-365-Az...