It verifies that OLSync or the DirectorySynchronization tool is enabled for your cloud-based organization.
It checks that a mail-enabled user exists in the cloud-based email organization for each entry in the CSV file.
It converts the mail-enabled user to a mailbox.
It configures mail forwarding by populating the TargetAddress property on the onpremises mailbox with the email address of the cloud-based mailbox.
This enables email sent to an on-premises mailbox to be forwarded to the corresponding cloud-based mailbox.
It migrates email messages, contacts, and calendar items from the Exchange mailboxes to the corresponding cloud-based mailboxes.
After mailbox items are migrated, the Exchange and cloudbased mailboxes are not synchronized. New email sent to the on-premises Exchange mailbox is forwarded to the corresponding cloud-based mailbox.
It sends an email message to the administrator when the migration batch is complete.
This message lists the number of mailboxes that were successfully migrated and how many could not be migrated.
The message also includes links to migration statistics and error reports that contain more detailed information.