OSS_Ja_JP

How do I move a mailbox from one Exchange account to another?
Exchange Mailbox Migration
Click on the Management tab.
Click on User Management --> Bulk User Modification --> Exchange Task --> Migrate Mailbox.
In the Migrate Mailbox page, select the Target Exchange Server.
Select a Mailbox Store from the options listed in the Target Mailbox Database.
Select the domain.

To know more about https://www.o365cloudexperts.com/blog/migrate-exchange-to-office-365-using-cutover-migration/