You can create an XML file that maps the user’s common name on the Exchange server to the user’s common name to be used on the ZCS server. When you run the migration wizard and prepare the source and destination mailboxes, you select
UserMap and select the XML file to be used.
The destination ZCS domain is configured on the Destination Domain dialog. During the migration, the destination account ID is created by appending this domain name to the <ZimbraAccount> value. For example, if the destination domain name is
zimbradomain.com, the above XML data would create an account ID called
zimbraexample1@zimbradomain.com, and the user’s Exchange mailbox is migrated.