First, you'll learn about using federation trust, organization relationships, and sharing policies to provide sharing of calendars and free/busy information between different Exchange organizations.Next, you'll you'll learn how to integrate an on-premises Exchange 2016 environment with Office 365 in a hybrid configuration.Some of them are now ready to upgrade the messaging services and use Exchange Online in Office 365.
So make sure the internal and external URL for OAB and Autodiscover virtual directory is configured properly.
As you begin to do your own upgrades (hopefully in a test environment before your production environment), keep Microsoft's definitions in mind.
Microsoft defines an upgrade as an increase in product version that can happen in place (that is, on the same server or workstation).
We will be setting up a hybrid configuration to allow for proper coexistence during the transition period to Exchange Online.
In order to accommodate for coexistence, the following components are required: Exchange 2013 cannot be used as the hybrid server as it cannot coexist in the same organization as Exchange 2003.