exchange 2013 hybrid, about 5 servers, installed 2019 and migrated all mailboxes to news servers after adding new servers to the hybrid setup as well
no i am not able to see the majority of the mailboxes under exchange admin center
old servers are decommissioned, trying to migrate mailboxes back on prem does not work because users are not mail enabled users anymore
when i try to enable-mailuser
It throws an error that this user does not support such format