Install and configure directorysynchronization.
The DirectorySynctool must be running to perform a staged email migration.
The directorysynchronization tool creates the mail-enabled users in the organization’s tenant account that are converted to mailboxes during the migration.
Plan for useridentitymanagement.
After the onpremisesmailboxes are migrated to the cloud, the synchronization process continues to update the user attributes on the mailbox according to changes made in the on-premisesActiveDirectory.
Because of this, the “sourceofauthority” for managing user objects is the onpremisesdirectory; therefore, you cannot manage user mailbox properties in ExchangeOnline.
However, after running a stagedExchangemigration you can configure directory synchronization so that the source of authority is the Office365 directory, which will enable management of mailbox properties in ExchangeOnline.
Configure OutlookAnywhere on the onpremisesExchangeserver. As with a cutovermigration, the migration service uses RPC over HTTP, or OutlookAnywhere, to connect to the onpremisesExchange server.
Install trustedcertificates.
The OutlookAnywhere configuration must be configured with a certificate issued by a trusted third-partycertification authority (CA). It cannot be configured with a self-signedcertificate. Also, the principal name on the certificate must match the host name of the external IP for the on-premises server.
Prepare the CSV file.
Identify the group of users whose onpremises mailboxes are to be migrated to the cloud. Include these users in the CSV file that will make up the migration batch.
Mailboxes are migrated in the same sequence listed in the CSV file. The attributes in the CSV file are EmailAddress
(required), Password(optional), and ForceChangePassword(optional).