Office 365 to Office 365 Migration Between Microsoft 365 Tenants

What is Office 365 to Office 365 migration?

Office 365 to Office 365 migration is a Microsoft 365 tenant-to-tenant scenario in which supported mailbox data is moved from one Microsoft 365 tenant to another. The source and target are separate tenants, so administrators must prepare the target environment, map source mailboxes to the correct target recipients, run the migration in planned batches, and validate the target before completing the cutover.

When organizations use this Microsoft 365-to-Microsoft 365 scenario

• Tenant consolidation: Move users and mailbox data from one Microsoft 365 tenant into another tenant that will remain in service.
• Mergers and acquisitions: Move acquired users into the receiving organization's Microsoft 365 tenant.
• Divestitures and restructuring: Move selected users or business units into a separate Microsoft 365 tenant.
• Provider-hosted tenant changes: Include this scenario only when the project actually moves users and data into a different Microsoft 365 tenant. A billing, reseller, or CSP change by itself does not automatically require tenant-to-tenant migration.
• Domain changes: Users may move to different target addresses as part of the migration. If the same custom domain must be retained, use the dedicated same-domain migration guidance linked below.

What can EdbMails migrate in this Office 365-to-Office 365 scenario?

For this Office 365-to-Office 365 mailbox workflow, EdbMails can migrate primary mailbox data and supported mailbox item types between Microsoft 365 tenants, with related workflows for shared mailboxes, archive mailboxes and public folders. SharePoint, OneDrive, Microsoft Teams and Microsoft 365 Groups should be described as separate EdbMails migration capabilities rather than as part of the same mailbox migration job.

• Mailbox workflow: Primary mailbox data and supported mailbox item types such as email, contacts, calendars, tasks, notes, folders and subfolders.
• Related mailbox scenarios: Shared mailboxes, archive mailboxes, and public folders use supported EdbMails migration workflows, with prerequisites and procedures that can vary by workload.
• Separate EdbMails migration capabilities: SharePoint migration, OneDrive migration, Microsoft Teams migration, and Microsoft 365 Groups migration should be planned as separate workload workflows.

Before you start: source and target readiness

• Source and target access: Confirm the authorized accounts or app access required to connect both Microsoft 365 tenants with EdbMails.
• Mailbox readiness: Confirm the source mailboxes are accessible and prepare the target recipients or mailboxes according to the chosen migration workflow.
• Licensing: Keep the source environment active as required during migration and confirm the target has the Microsoft 365 licensing needed for the final mailbox and user setup.
• Mapping plan: Prepare the source user list and the corresponding target identities or addresses.
• Domain plan: Decide whether users will keep the same custom domain or move to different target addresses.
• Pilot and validation: Select representative pilot users, confirm the migration workstation can reach both tenants, and define the report, mailbox, sign-in and mail-flow checks that will be used before cutover.

High-level Office 365 to Office 365 migration workflow

1. Define the source and target Microsoft 365 tenants and decide which users or mailboxes are moving.
2. Prepare the target recipients and confirm the target licensing and domain approach.
3. Connect the source tenant in EdbMails using the verified authentication method.
4. Select the source mailboxes and supported data in scope.
5. Connect the target Microsoft 365 tenant.
6. Map source mailboxes to the correct target recipients using the supported automatic, CSV or manual method.
7. Run a pilot or initial production migration.
8. Review migration reports and resolve failed or skipped items.
9. Run the supported incremental or repeat migration for new or changed items before cutover.
10. Validate representative target mailboxes and complete the scenario-specific cutover.

For screenshots, button-level instructions and the complete procedure, follow the Office 365 tenant-to-tenant migration step-by-step guide.

Map source mailboxes to the correct target recipients

Before starting the migration, confirm that every source mailbox maps to the intended target recipient. EdbMails supports source-to-target mailbox mapping, with automatic mapping for matching recipients and manual or CSV-based mapping where addresses differ or accounts need explicit pairing. Review unmatched or changed-address users before starting a production batch. If the same custom domain will move between tenants, use the dedicated same-domain migration guidance because mapping and domain cutover become separate parts of the project.

Run incremental or repeat migration before final cutover

The initial EdbMails migration is a full migration. Subsequent migrations using the same source and target from the previous migration on the same computer are incremental, migrating supported new or modified items. Before final cutover, run the migration again to migrate any pending items and review the migration report.

See the current EdbMails incremental migration guidance for supported behavior.

Validate the target before completing the migration

• Review the migration report for completed, failed, skipped or warning items.
• Verify representative target mailboxes and the supported item types that were in scope.
• Confirm users can access the target tenant with the planned identities.
• Run the final incremental/repeat pass if source mailboxes changed after the initial migration.
• Test mail flow after the scenario-specific cutover.

Use the Step-by-Step Guide for the complete validation and post-migration procedure.

If the same custom domain must move to the target tenant

If users must keep the same custom domain after moving to the target tenant, treat domain transfer as a separate cutover activity. The custom domain must be released from the source tenant before it can be attached to the target tenant, and source references and DNS/mail-flow changes must be planned carefully. Use the dedicated Office 365 migration with the same domain guide for that sequence.

Advanced cross-tenant planning

For advanced cross-tenant planning topics such as coexistence, identity strategy, native Microsoft migration architecture, phased cutover and specialist migration challenges, use the cross-tenant Office 365 migration guide instead of expanding those topics on this scenario page. For broader planning concepts, see the Office 365 migration guide.

Related EdbMails migration capabilities

• Office 365 public folder migration
• Office 365 archive mailbox migration
• Microsoft 365 Groups migration
• SharePoint migration
• OneDrive migration
• Microsoft Teams migration

Office 365 to Office 365 migration FAQs