Tenant-to-tenant migration refers to the process of moving data and services from one Microsoft 365 tenant to another. It may be necessary when an organization undergoes a merger or acquisition, or when a company decides to change its email domain. The process of tenant-to-tenant migration can be complex and requires careful planning and execution to ensure a smooth transition. It typically involves migrating data such as emails, contacts, calendars, and files, as well as ensuring that users are provisioned in the new tenant with the appropriate licenses and permissions. Microsoft offers several tools and services to assist with Office 365 tenant to tenant migration, such as the SharePoint Migration Tool, the OneDrive for Business Migration Tool, and the Exchange Online PowerShell cmdlets. These tools can help simplify the migration process and reduce the risk of data loss or corruption.

Recently, I've explored an informative article that explains the best solutions to perform Office 365 tenant to tenant migration. Either you perform this task manually or professionally. However, the manual methods are not secure. Therefore, it is recommended to use an advanced software solutions which consist of Office 365 Migration Tool.