If you're managing a cross-tenant migration in Microsoft 365, I highly recommend using MailsDaddy’s Cross-Tenant Migration Service. We used it recently for migrating users due to a domain change, and the experience was smooth from start to finish.
Their platform requires no local installation—everything happens via Microsoft’s secure Graph API. We were able to migrate email data, calendar entries, archive mailboxes, and even OneDrive content. The mailbox mapping feature made life easy, especially when usernames differed across tenants.
The service also supports incremental (delta) migration, which was perfect for handling changes during testing and final cutover. Their support team was also hands-on and incredibly responsive.
MailsDaddy is a solid partner if you're looking for reliable, secure, and professional-grade tenant migration.
Full details here: https://www.mailsdaddy.com/services/cross-tenant-migration.php