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Microsoft 365 Tenant-to-Tenant Cutover Email Migration
IT Partner provides planning, design, and migration of email service from one Microsoft 365 tenant to another.
$35 per mailbox + $3,500 tenant fee5 weeks
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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.
01 — Overview
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.
02 — Outcomes
Success criteria
01Users can access Shared Mailboxes on their desktop PCs, mobile phones and tablets from any place, any time.
02The migration of shared mailboxes has been completed successfully, ensuring that all data and settings from the source tenant have been transferred to the destination tenant.
03 — Deliverables
What you receive
✓Migration planning and preparation by assessing the environment and setting up the target tenant.
✓Source and target environments configured for migration, including the necessary permissions.
✓Migration batch created.
✓Detailed inventory of all the shared mailboxes that includes their names, sizes, permissions, and any specific configurations.
✓Pre-migration source system health check performed.
✓Shared Mailboxes created.
✓Shared mailbox migration started.
✓Migration progress monitored.
✓Verification of email migration performed.
✓Final email migration performed.
✓Verification that all data has been successfully migrated.
✓Post-migration tasks performed.
04 — Plan
How the work unfolds
Kickoff meeting.
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.
Pre-migration source system health check.
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.
Creating Shared Mailboxes.
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.
Mailboxes migration start.
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.
Verification of email migration.
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.
Final email migration.
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.
Post-migration tasks.
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.
05 — Before we start
Prerequisites
→Tenant to tenant mailbox migration project from IT Partner.
06 — Working together
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.
07 — Scope
What's not included
✕Migration of user mailboxes, archive mailboxes, public folders, Microsoft Teams, OneDrive, SharePoint, Groups, or other Microsoft 365 workloads unless included under a separate tenant-to-tenant migration scope.
✕End-user device reconfiguration, Outlook profile rebuilds, mobile device re-enrollment, or hands-on desktop support unless separately agreed.
✕Remediation of pre-existing Exchange Online, identity, licensing, DNS, compliance, retention, or mail flow issues outside what is required to complete the shared mailbox migration.
✕Design or implementation of new Microsoft 365 security, compliance, retention, eDiscovery, DLP, or governance policies.
✕Custom application remediation, third-party integration updates, SMTP relay reconfiguration, or line-of-business application changes that depend on shared mailbox addresses.
✕Long-term post-migration support, managed services, or ongoing administration after project closure.
✕Legal hold, eDiscovery export, backup, or independent archival services unless separately scoped.
✕Mailbox cleanup, deduplication, corruption repair, or content restructuring beyond standard migration handling.
08 — Fine print
Limitations & technical notes
!This service runs as part of an IT Partner tenant-to-tenant mailbox migration project, which provides the cross-tenant migration configuration (organization relationships and migration endpoints) that shared mailbox batches depend on.
!Cross-tenant mailbox moves require a Cross-Tenant User Data Migration add-on license per migrating mailbox, assigned in accordance with Microsoft's licensing requirements; shared mailboxes themselves remain license-free at rest within Microsoft's limits.
!Migration timing and throughput depend on Microsoft 365 service health, tenant throttling, mailbox size, item count, and source tenant condition; the service does not state a migration throughput SLA.
!Send As, Send on Behalf, and Full Access permissions are inventoried before migration and re-applied or validated in the target tenant; permissions referencing users that do not exist in the target tenant require mapping decisions during planning.
!Some mailbox settings or client-side behaviors may require post-migration validation or adjustment depending on how they are represented in the source tenant and supported in the target tenant.
!Cutover behavior and mail flow for the shared mailbox addresses follow the broader tenant-to-tenant migration plan's domain and MX cutover sequencing, confirmed at kickoff.
09 — Questions
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.
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$35 per mailbox + $500 tenant fee
5 days