from on premise to the Cloud or vice versa.
This service enables you to also synchronize from a folder level like calendars, contacts, tasks, emails and other default elements of the Exchange server. It is able to migrate or sync on premise to cloud and vice versa as well. You can migrate between Office 365 accounts or between other Exchange online services with these Exchange versions: 2007, 2010, 2013, 2016 as well as Office 365.
As long as your migration is running you have co-existence between source and target Exchange.
Before you can start with ExMixedFolders you need to move the AcitveDirectory to the new Server. This can be done by Microsofts ADMT (Windows Server Active Directory Migration Tool).