Forum Discussion
Set up hybrid
What you want to do is referred to "offboarding", and with Hybrid in place it's almost the same process as moving mailboxes to ExO: https://docs.microsoft.com/en-us/exchange/hybrid-deployment/move-mailboxes#move-exchange-online-mailboxes-to-the-on-premises-organization
If you want a more detailed description on how the process works in general, refer to this article series from Steve: http://techgenix.com/migrating-standalone-office-365-tenant-exchange-2010-part1/
It's a bit outdated by now, but the overall process is more or less the same.
What you want to do is referred to "offboarding", and with Hybrid in place it's almost the same process as moving mailboxes to ExO: https://docs.microsoft.com/en-us/exchange/hybrid-deployment/move-mailboxes#move-exchange-online-mailboxes-to-the-on-premises-organization
If you want a more detailed description on how the process works in general, refer to this article series from Steve: http://techgenix.com/migrating-standalone-office-365-tenant-exchange-2010-part1/
It's a bit outdated by now, but the overall process is more or less the same.