How do you handle identity during Microsoft 365 tenant-to-tenant migrations?

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Identity is usually the hardest part of a Microsoft 365 tenant-to-tenant migration — more complex than moving mailboxes or files.

From what we’ve seen, successful migrations focus on identity planning first, not last.

Key identity challenges during tenant migrations

  • Mapping users between source and target tenants

  • Preserving UPNs, email aliases, and groups

  • Avoiding SSO breakage for apps relying on OAuth / SAML

  • Managing hybrid or federated identities

  • Ensuring users don’t lose access on Day-1

What works best in real projects

  1. Pre-migration identity assessment
    Audit users, domains, groups, and authentication methods before moving any data.

  2. Clear identity mapping strategy
    Decide early how users will be matched or recreated in the target tenant (same UPN vs new domain).

  3. Parallel identity + workload migration
    Identity should move alongside mailboxes, OneDrive, Teams, and SharePoint — not as a separate task.

  4. Use a dedicated tenant-to-tenant migration platform
    Tools built specifically for cross-tenant migrations reduce manual identity errors and help keep permissions, access, and user context intact.

In our experience, platforms like CloudBik help by orchestrating tenant-to-tenant migrations in a structured way — covering workloads while aligning user identities and access across tenants. This is especially helpful in M&A, tenant consolidation, divestiture, or rebranding scenarios.

Curious to hear from others:

  • How do you prevent identity or SSO issues during tenant migrations?

  • Any lessons learned or best practices you’d recommend?