Mailbox Management & SSO after Office 365 Hybrid Migration

So you are coming to the end of an Exchange Online Hybrid migration, and are considering decommissioning the on-premise Hybrid Exchange server.  Are there any considerations that need to be taken into account?

By the end of the mailbox migrations, you may have configured Azure AD Sync and made the on-premises Active Directory the source of authority. Therefore, going forward, you must perform any required changes on the objects in the on-premises Active Directory and not in Office 365, as most attributes on  are read only. read more