Thomas.Poett@TEAMS (MVP Teams and Cross-Tenant M&A/D Migration Expert Lead)

Orchestrated migration is executed as a migration job (a batch). Microsoft states that the maximum batch size is 100 users and migrations are managed through Microsoft Graph APIs (beta) using PowerShell or Graph Explorer. Step 1: create a validation batch (recommended) Use standalone validation to confirm prerequisites before you submit an actual migration. Validation behaves like a what-if: it checks prerequisites at tenant and user levels (permissions, relationships, identity mapping, licensing, and more). Step 2: submit the migration batch and understand the stages ·        Validation: checks prerequisites; if checks fail, the user's migration does not begin. ·        Mailbox syncing: mailbox content is synced in the background while the user continues working in the source tenant. Microsoft strongly recommends submitting batches two weeks before the cutover date. ·        Cutover: a...

Dedicated cross-tenant SharePoint migration is the workload-specific method for moving SharePoint sites between tenants using SharePoint Online PowerShell. Use it when you need to migrate shared sites (including Teams-connected SharePoint sites), which are out of scope for Orchestrator. Scope and key constraints ·        Up to 4,000 SharePoint migrations can be scheduled at a time. ·        One-and-done: no incremental/delta passes; redirects are left behind. ·        Supported site types include group-connected sites (including those associated with Teams), modern non-group sites, classic sites, and communication sites. ·        This does not migrate Teams content, channels, or associated structure; for Teams-connected sites, only the SharePoint site content is migrated. ·        Do not precreate target SharePoint sites; if th...

Dedicated cross-tenant OneDrive migration is the workload-specific method for moving personal OneDrive accounts between tenants using SharePoint Online PowerShell. It is especially useful when you want a OneDrive-only runbook, or when you are not using the orchestrated workload chain. How it behaves (expectations to set) ·        Up to 4,000 OneDrive accounts can be scheduled at a time. ·        Migrations occur in the Microsoft 365 cloud with only a brief read-only window for the user. ·        A redirect is placed at the original OneDrive location so existing links keep working. ·        Cross-tenant moves are one-and-done: no incremental/delta passes. ·        Not supported for Government Cloud users (GCC, GCC High, DoD, etc.). Prerequisites that frequently block projects ·        Licensing:...

Cross-Tenant Identity Mapping (CTIM) is Microsoft's tool for mapping source users to target users one-to-one so content, permissions, and user experiences remain consistent. Running identity mapping is required when you migrate user data using the orchestrated method. What CTIM does (in practical terms) CTIM helps you: ·         Map users one-to-one between tenants and reduce manual errors. ·         Update properties so users have correct attributes for migration. ·         Maintain mapping data so the correct source content lands on the correct target user. When to run CTIM Microsoft recommends running CTIM after creating target users and before migrating data. This sequence improves accuracy and avoids manual cleanup work. Security and compliance note (data-at-rest and network) CTIM stores different categories of data in different regions (for example, reports in the tenants' Exch...

Orchestrated migration requires that both source user objects and target user objects exist. Your most important goal is to create target users in the right state so identity mapping and migration can run without failures. Non-negotiable rule: do not provision target mailboxes or OneDrive sites early Microsoft emphasizes an order of operations: complete identity mapping before assigning Exchange or OneDrive licenses to target users. If you license target users too early, they may provision mailboxes, breaking the required MailUser state. Create target MailUsers (MEUs) in Exchange Online A MailUser object (Mail-Enabled User / MEU) must exist in the target tenant for each migrating source user. CTIM stamps ExchangeGuid and other attributes later, so you do not need to pre-populate everything up front. Connect-ExchangeOnline New-MailUser -PrimarySmtpAddress username@targettenant.com -MicrosoftOnlineServicesID username@targettenant.com -ExternalEmailAddress username@sourcetenan...

Before you touch user objects or submit migration batches, you need to configure both the source and target tenants so the orchestrated tooling can validate prerequisites, access the right workloads, and run migrations securely. Mailbox migration: use cross-tenant mailbox migration setup For mailbox moves, Microsoft directs admins to complete the standard cross-tenant mailbox migration preparation steps (organization relationships, endpoints, and related Exchange Online configuration). Treat this as the foundation for the orchestrated chain. OneDrive: establish trust, then grant the OneDrive/SharePoint migration permissions Orchestrator uses the same trust model as the dedicated OneDrive migration approach: establish trust between the tenants using the published steps, then configure the OneDrive migration application permissions via a Microsoft-provided module. Connect-MgGraph  # as Global Administrator (run in both tenants) Import-Module <downloaded module path> ...

  In many tenant-to-tenant programs, the business need arrives before the migration plan: "We need to collaborate now." Microsoft's guidance reflects this reality by recommending that organizations establish a Multitenant Organization (MTO) for day-1 collaboration and then transition into migration readiness in a controlled way. Day-1 collaboration: what MTO enables MTO enables immediate cross-tenant collaboration without changing user credentials. Typical steps include: ·        Create the MTO in the Microsoft admin center. ·        Configure trust relationships and policies. ·        Sync users as B2B external members for cross-tenant collaboration. ·        Enable collaboration features (Teams, file sharing, profile cards). Moving from MTO to migration readiness: the key concept The transition from MTO collaboration to migration readiness is abo...

  Migration Orchestrator is Microsoft's tenant-to-tenant migration approach for moving personal user workloads between separate Microsoft 365 tenants (for example in mergers, acquisitions, divestitures, or internal reorganizations). It is designed to migrate workloads in an order that accounts for dependencies and aims to minimize end-user disruption. What Orchestrator migrates (and what it does not) Orchestrator supports the migration of personal, user-scoped workloads. In the current preview scope, it includes: ·        Exchange Online mailbox (user-visible content such as email, contacts, calendar, tasks, and notes). ·        OneDrive (personal) content, moved to the target with a redirect left in the source location (no incremental/delta passes). ·        Teams chats and Teams meetings (with dependency on mailbox success for meeting migration). Orchestrator does not migrate sha...

  This final post is a configuration-focused checklist for standing up enterprise voice capabilities end-to-end. It assumes you already decided your PSTN model and that Teams is deployed. Use it as a runbook skeleton you can adapt to your environment. Configuration guide: Operator Connect (high level) 1. In Teams admin center, go to Voice > Operators and enable your chosen operator (select countries/regions and accept the notice). 2. Work with the operator to acquire numbers; once uploaded, assign numbers in Voice > Phone numbers. 3. Coordinate emergency address handling with the operator (operator-managed vs tenant-managed addresses). Configuration guide: Direct Routing (high level) 1. Connect a certified SBC to Teams Phone and validate connectivity. 2. Enable users for Direct Routing and voice/voicemail. 3. Configure call routing and number normalization as required. 4. Define and assign voice routing policies (Voice > Voice routing policies). Configu...

  ‘Enterprise Voice’ in Teams typically means Teams Phone plus a PSTN connectivity model that fits your organization’s carrier strategy, geography, and operational maturity. Teams includes native calling between Teams users; adding Teams Phone licensing and a PSTN connection extends calling to external phone numbers and introduces enterprise telephony capabilities like auto attendants and call queues. The three most common PSTN models ·        Calling Plans: Microsoft acts as the PSTN carrier (simplest deployment model). ·        Operator Connect: a certified partner carrier integrates with your tenant via Teams admin center. ·        Direct Routing: you connect your chosen carrier via a certified Session Border Controller (SBC) that you manage. Configuration guide: choose the right model Use these criteria to drive a defensible decision: ·        Speed vs control...