Mastering a Tenant-to-tenant migration
Why Tenant Migration
Often, migrations are business driven; companies and their tenants get merged, aquired or rebranded. Microsoft has described a couple of tenant-to-tenant scenarios in their migration guides; the approach differs in the fact what should be achieved:
- Single-event Migration:
⊕ less complex («over night»), minimal tranisition
⊖ higher risk, not easy when migrating large amount of data, needs mor planning and testing as well as more IT resoureces during the migration itself - phased migration:
⊕ less risk no alternatives in large environments, easier to execute
⊖ more complex (in terms of planning and doing), difficult as process, co-existing tenants, often time consuming
Tenant Migration Scenarios
The general Process: Discovery — Planning — Design — Testing — Migration — Hypercare — Post Migration
Consider these migration decisions:
| Destination tenant | Migration type |
|---|---|
| New environment | Single-event Migration |
| Existing environment | Phased Migration / Co-Existence (balance the risk and business deadlines) |
Always do assessment with the aim to know your users and data (spend some time to “dive into” all the [old] data). ANY migration project is time consuming – you can only loose time, and not saving time when not cleaining up the data to be migrated.
Planning
A good plan is the key to success. Always put into consideration to identifiy these workloads:
- Microsoft Entra (MFA, App Registrations)
- Exchange Online
- OneDrive for Business
- SharePoint Online
- Teams
- Planner
Challenges
Data is often hard to migrate (because data locations are [mostly] not stored within your tenant) from:
- Online Services:
- Intune, Stream, Microsoft Forms, Viva Engage
- Azure (Entra ID App Registrations and 3rd Party Apps)
- Microsoft Information Protection (⚠️ always decrypt data before migration – and encrypt afterwords); Encrypted Data, Sensitivity Labels, Retention Policies, DLP Policies, Audit Logs (question: what are you going to do with these)
- Exchange Online:; Mail Flows (Partner Connectors, specialized mail flows), Meetings (old meetings sill work, existing meetings need to be deleted by users [cannot be recheduled], new meetings will need to be re-created by all users [replacing existing meetings])
- Teams & SharePoint: External Guests (how do we handle the invited users?)
- Power Platform: Power BI, PowerApps, Power Automate, Dataverse, Dynamics App
- What about on-premises legacy systems 👉 manual migration processes are necessary regarding these migration sources; consider to check for appropriate tooling support
It’s highly recommended that you put migration performance and bandwidth throttling into consideration.
Licensing and subscription
To avoid high licensing costs, alwasy ask Microsoft for leveraging licenses in both tenants for a defined period of time.
The Tenant Migration
Tooling
Check out these Microsoft Tools:
- Cross-tenant Mailbox Migration (PowerShell)
- Cross-tenant OneDrive Migration
- Cross-tenant SharePoint migration (preview)
- Cross-tenant Identity Mapping (preview / pulled back; at this time not available yet)
- Cross-tenant Domain Sharing (preview)
Put into consideration (highly recommended) to use som 3rd party tools (Quest On-Demand Migration, BitTitan MigrationWiz, ShareGate Migration, Skykick Migration Suite, Avepoint Migration Platform, CodeTwo Office 365 Migration). Every tool has its own benefits and limitations – know the difference and the limitations!
Specific questionss
E-Mail migration
- Do we need co-existence?
- Mail flows?
- Calendar federation? (fairly easy)
- Email domain? Moving the email domain has to be one of the last parts of the whole migration process (mail domain is often used in the user principal names)
- MX backup?
- What about Mailboxes, Shared Mailboxes, Rooms and Equipment, Groups, Meetings, Permissions and delegations?
OneDrive and SharePoint
- Data & Versioning (do we really need all versions?)
- checked in documents?
- Issues with user settings
Microsoft Teams
- Can be migrated: Teams files, team chats (conversations, 1:1 chats)
End users
- Communicate to the end users!! Tell them about the plan (how and when will be migrated? How will it affect them? What tasks might be required by them before / after the migration?)
👉 Find your “plan” how often and how detailed you will inform the users - Remember all stakeholders in the entire organization
The journey
Migration is complex. The migration journey always contains:
- Assessment
- Planning and (pre-) testing
- Migration
- Testing (is essential)
- Hypercare phase