If you're in the enterprise space and need to perform a Microsoft 365 cross-tenant migration, let me save you the trial-and-error. After evaluating multiple options and even attempting manual PowerShell scripts, we finally landed on MailsDaddy Cross-Tenant Migration Service, and the results were outstanding.

We had to migrate over 800 users due to a merger, including primary mailboxes, archives, calendars, and OneDrive. The tool’s dashboard allowed us to map users through CSV, apply filters by date and folder, and monitor progress in real-time. We especially loved the delta migration feature, which allowed us to sync only the updated data before go-live—saving a huge amount of bandwidth and time.

Another standout feature was the secure OAuth 2.0 login and encryption protocols that ensured our compliance team signed off quickly. There’s also no need to install anything locally; the entire service is cloud-driven and safe.

The support team was also fantastic—they were there throughout pre-migration setup, test migrations, and even during final cutover. We completed the migration ahead of schedule with zero downtime.

If you’re looking for a tried-and-tested solution for large-scale Office 365 tenant migrations, this is the one to go with: https://www.mailsdaddy.com/services/cross-tenant-migration.php