To migrate a mailbox larger than 50GB into Office 365, follow these steps:
1. Open MigrationWiz and create a mailbox migration project.
2. Configure the Source and Destination Endpoints.
3. Add the users to the project.
4. Within the Advanced Options section, configure the destination settings to migrate to the Archive mailbox for the users. For guidance, see What are my mailbox or archive migration options?
5. Set a date range filter within the project to migrate items older than a specific date. For example, migrate all items a year old or older to the Archive mailbox. For guidance, see How do I set a date range filter in MigrationWiz?
6. Submit a Full migration pass that migrates only mail items. Monitor the migration until it is successful.
7. Once the migrations to the archive mailboxes are complete, change the setting in the Advanced Options to now migrate to the primary mailbox instead of the archive mailbox.
8. Remove the date range filter.
9. Perform either a Pre-Stage migration or a Full migration pass to the primary mailbox.