Microsoft Solutions Partner|Modern Work · Azure · Security · Business Apps
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Migration and Modernization

Microsoft 365 Tenant-to-Tenant Migration for Mergers, Acquisitions and Divestitures

When companies merge, split or rebrand, their Microsoft 365 environments have to follow. RHC moves users, mailboxes, files, sites and Teams from one tenant to another while people keep working. We have delivered tenant-to-tenant projects from a few hundred users to multi-country consolidations with Multi-Geo.

The challenges

  • A domain can live in only one tenant at a time, so the email cutover has to be planned to the hour.
  • Both companies usually need shared calendars, free/busy and Teams chat before the final switch.
  • Accounts, groups and licenses have to be recreated in the target tenant, often from a different Active Directory.
  • Terabytes of SharePoint and OneDrive data need to arrive with their permissions intact.
  • The deal sets the deadline: a Transition Service Agreement (TSA) gives a fixed date to leave the old tenant.

How we do it

  1. 1Assessment: inventory of users, mailboxes, sites, Teams, Power Platform and third-party apps in both tenants.
  2. 2Design: identity mapping, coexistence model, cutover strategy and wave plan.
  3. 3Target tenant preparation: identity, licensing, security baseline and domain plan.
  4. 4Pilot: a small group migrates first to validate tools, timing and user experience.
  5. 5Waves and delta syncs: content is pre-staged, then only changes are copied at cutover.
  6. 6Cutover: domain move, MX and DNS changes, profile reconfiguration and Outlook/Teams sign-in.
  7. 7Hypercare: support for users in the first days and decommissioning of the source tenant.

What’s included

Exchange Online mailboxes, archives and shared mailboxes
OneDrive and SharePoint sites with permissions and versions
Microsoft Teams, channels and files
Identity and group mapping, including hybrid Active Directory
Coexistence (free/busy, mail routing) during the transition
End-user communication kit and support during cutover

We use AvePoint Fly or Microsoft's native cross-tenant tools, depending on the workload.

Why RHC

15 years as a Microsoft partner, focused only on Microsoft cloud
Experience with acquisitions, carve-outs and multi-country consolidations
Fixed-scope proposals with a wave plan and a clear cutover date
Teams in the US and Brazil, with delivery in English, Portuguese and Spanish

Frequently asked questions

Most projects with 200 to 1,000 users take 6 to 12 weeks, including assessment and hypercare. The data volume and the coexistence needs define the final timeline.

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