Shared Mailbox Tenant-to-Tenant Migration — Microsoft 365 Mailbox Transfer
Shared Mailbox Tenant-to-Tenant Migration transfers shared mailboxes — including emails, calendar items, contacts, and the related permissions, configurations, and settings — from one Microsoft 365 tenant to another, typically during mergers, acquisitions, divestitures, or tenant consolidations. Shared mailboxes move with the same Microsoft-native cross-tenant mailbox migration batches used for user mailboxes, so this service runs as part of an IT Partner tenant-to-tenant mailbox migration project: IT Partner plans, inventories, configures both tenants, runs and monitors the migration, verifies results, and completes post-migration tasks, at $35 per mailbox over 5 days.
What this engagement is
Shared mailboxes serve functions where multiple people work a common address — company inquiries, customer support, reception desks — with members sending as or on behalf of the mailbox. When Microsoft 365 environments consolidate or separate, those mailboxes must move too. Microsoft's native cross-tenant mailbox migration (Exchange Online Mailbox Replication Service batches) supports shared mailboxes, and that is the path this service uses: the cross-tenant relationship configured for the broader tenant-to-tenant mailbox migration project carries the shared mailboxes as well. Licensing has one nuance worth knowing: shared mailboxes are license-free at rest, but each migrating mailbox needs a Cross-Tenant User Data Migration add-on license for the move itself. IT Partner inventories the shared mailboxes with their sizes, permissions, and configurations, creates the target objects, runs and monitors the migration batches, verifies the migrated data, re-applies access permissions, and completes post-migration tasks.
Success criteria
What you receive
How the work unfolds
Confirm the shared mailbox migration scope, source and destination tenant details, mailbox counts, project contacts, access requirements, schedule, communications approach, and validation responsibilities. Review dependencies on the broader tenant-to-tenant mailbox migration project.
Review the source Microsoft 365 tenant readiness, shared mailbox inventory, mailbox sizes, permissions, delegation settings, send-as/send-on-behalf requirements, migration access, and any known Exchange Online issues that could affect migration.
Create or prepare the required shared mailboxes in the target tenant using the agreed naming, alias, and configuration approach. Align target objects with the migration plan and confirm that required permissions can be applied.
Configure the migration batch or migration tooling, start the shared mailbox data synchronization, and monitor initial progress for connectivity, throughput, authentication, and item-level errors.
Validate migrated mailbox content and representative mailbox functionality in the destination tenant, including folders, recent and historical mail, calendar items, contacts, and assigned access permissions where applicable.
Perform the final synchronization or cutover step after the initial migration is complete, confirm any remaining delta items are transferred, and align final timing with the tenant-to-tenant migration schedule.
Complete final validation, review migration results with the client, address migration exceptions within the agreed scope, confirm shared mailbox access from supported clients, and provide status information for project closure.
Prerequisites
Who does what
IT Partner
- Plan and prepare for the migration by assessing the environment and setting up the target tenant.
- Configure the source and target environments for migration, including setting up the necessary permissions and creating a migration batch.
- Detailed Inventory. Create a detailed inventory of all the shared mailboxes that includes their names, sizes, permissions, and any specific configurations.
- Monitor the progress of the migration.
- Verify that all data has been successfully migrated and perform any necessary post-migration tasks.
- Minimize user intervention during the migration process.
Your team
- Provide a dedicated point of contact responsible for working with IT Partner.
- Coordinate any outside vendor resources and schedules.
- Provide temporary access to the existing environment/IT Infrastructure.
What's not included
Limitations & technical notes
Frequently asked questions
What is the Shared Mailbox Tenant-to-Tenant Migration service?
It transfers shared mailboxes from one Microsoft 365 tenant to another — typically during mergers, acquisitions, divestitures, or tenant consolidations — using Microsoft's native cross-tenant mailbox migration batches, as part of an IT Partner tenant-to-tenant mailbox migration project.
What data is included in the shared mailbox migration?
Shared mailbox emails, folders, calendar items, contacts, and associated data, along with the related permissions, configurations, and settings. IT Partner verifies after migration that the data and settings have transferred to the destination tenant.
How do shared mailboxes actually move between tenants?
Through Exchange Online's cross-tenant mailbox migration — the same Microsoft-native Mailbox Replication Service batches used for user mailboxes. The cross-tenant setup (organization relationships and migration endpoints) established for the broader migration project carries the shared mailbox batches too.
Do shared mailboxes need licenses to migrate?
Shared mailboxes are license-free at rest within Microsoft's limits, but the cross-tenant move itself requires a Cross-Tenant User Data Migration add-on license per migrating mailbox, assigned per Microsoft's licensing requirements. IT Partner identifies the licensing needs during planning.
How much does the migration cost, and how long does it take?
The service is $35 per shared mailbox over a 5-day engagement, quoted in writing before work begins. Scheduling is coordinated with the broader tenant-to-tenant mailbox migration project.
What are the prerequisites for this service?
A tenant-to-tenant mailbox migration project from IT Partner — that project provides the cross-tenant migration configuration this service depends on. The client also provides a dedicated point of contact, coordinates any outside vendors, and provides temporary access to the existing environment.
What is included in IT Partner's shared mailbox migration work?
Migration planning and environment assessment, source and target configuration with required permissions, a detailed inventory of shared mailboxes (names, sizes, permissions, configurations), a pre-migration health check, target mailbox creation, migration batch execution and monitoring, verification, final migration, and post-migration tasks — designed to minimize user intervention.
Does the service migrate shared mailbox permissions, including Send As and Send on Behalf?
Yes. Permissions are captured in the pre-migration inventory and re-applied or validated in the target tenant, including Full Access, Send As, and Send on Behalf scenarios. Where a permission references a user not present in the target tenant, the mapping is decided during planning.
Will users still be able to access shared mailboxes after migration?
Yes — the success criterion is that users access the migrated shared mailboxes from desktop, mobile, and tablet clients as before. Access depends on the users themselves having been migrated or mapped in the target tenant, which the broader migration project handles.
Is downtime expected during the shared mailbox migration?
The migration batches synchronize data while the source stays in service, and the final cutover follows the mail-flow plan of the broader tenant-to-tenant project. The service does not guarantee a zero-impact cutover; expected timing and user impact are confirmed at kickoff.
What verification is performed after migration?
IT Partner verifies the migrated mailbox content and settings against the inventory — folders, mail, calendar items, contacts, and assigned permissions — and reviews results with your point of contact before closing out the migration.
What is not included in this service?
User mailboxes, archive mailboxes, public folders, Teams, OneDrive, SharePoint, and Microsoft 365 Groups migrate under their own scopes; also excluded are end-user device reconfiguration and Outlook profile rebuilds, remediation of pre-existing tenant issues beyond what the migration requires, new security or compliance policy design, changes to third-party applications that send from shared mailbox addresses, and long-term post-migration support.