Tenant to Tenant Migration
This Explain how to perform a tenant to tenant migration in M365
M365 MIGRATIONS
Dhivagar Balaji
7/3/2026
A Phased Approach to Microsoft 365 Tenant-to-Tenant Migration
When consolidating IT infrastructure or merging organizations, migrating Microsoft 365 services from one tenant to another requires a strategic, carefully planned approach. To ensure minimal disruption and maximum data integrity, I recommend a structured, three-phase methodology for migrating services and data from a Source tenant to a Target tenant.
Here is my step-by-step roadmap for a successful migration.
Migration Approach:
Pilot Migration: Perform an initial migration with a small group of pilot users to validate migration performance, data fidelity, and overall process.
Batch-Based Migration: Migrate users and workloads in planned production batches according to the agreed migration schedule.
Batch Validation: Validate the successful migration of data, permissions, and configurations after each batch is completed.
Final Delta Synchronization: Synchronize any data changes that occurred between the initial migration and the final cutover.
Cutover: Complete the migration by updating mail flow, DNS records, and production routing to the Target tenant.
Post-Migration Support: Provide proactive user communications, issue resolution, and operational support following each migration wave.
Workloads can be Migrate:
Exchange Online: User Mailboxes, Shared Mailboxes, Distribution Lists, and Mail Contacts.
OneDrive for Business: User files and folders, along with sharing permissions (where applicable).
SharePoint Online: Sites, Document Libraries, and Permissions.
Microsoft Teams: Teams Structure, Channels, Files, and Memberships.
Phase 1 – Pre-Migration Readiness
Objectives: Prepare the both source and target Microsoft 635 environment for migration.
Key Activities:
Audit & Document: Thoroughly review and document the Source environment:
User accounts and Security Groups
User and Shared Mailboxes
Distribution Lists
Microsoft Teams and SharePoint Sites
OneDrive Data
License Details
Prep the Target: Validate licensing requirements in the Target tenant and the Tenant is set for user provisioning.
Consolidation and Batch Planning
Consolidate all users, groups, and sites that are listed for migration, and segregate them into batches. You may create as many batches as needed.Pilot Migration Batch
Create a separate pilot batch containing pilot users so that we can verify the migrated data before proceeding with the production migration. Once the pilot migration is validated, continue with the production batches.
Production Batch Prioritization
Prioritize users with larger mailbox sizes in the initial production batches to ensure they are migrated early in the process.
Phase 2 – Tenant-to-Tenant Data Migration
Objectives: Migrate all Source user identities and Microsoft 365 workloads to the Target tenant.
Key Activities:
Provision Users and Assign Licenses
Before migrating data, provision all users in the Target tenant and assign the appropriate Microsoft 365 licenses. Verify user identities, group memberships, and authentication methods to ensure users are ready to access their new environment.Configure Migration Tool
Configure the migration platform with connections to both Source and Target tenants.
This includes:Registering Azure AD applications (if required)
Granting administrative permissions
Creating migration projects
Mapping source users to target users
Configuring migration options and throttling settings
Popular migration tools include:
Microsoft Migration Manager
BitTitan MigrationWiz
Quest On Demand Migration
AvePoint Fly
CloudM Migrate
Execute the Pilot Migration
Run the pilot migration using the predefined pilot batch.Validate the following:
Mailbox data
Calendar items
Contacts
Tasks
OneDrive documents
SharePoint content
Teams files and memberships
Permissions and sharing links
Migration reports and error logs
Gather feedback from pilot users before proceeding with production migration.
Production Batch Migration
Once the pilot is approved, migrate production users according to the agreed migration schedule.Each migration wave should include:
User Mailboxes
Shared Mailboxes
Distribution Lists
Microsoft Teams
OneDrive
SharePoint Sites
Where possible, perform pre-stage migrations several days before cutover to reduce migration duration during the production window.
Batch Validation
Following every migration batch, perform validation activities including:Mailbox item counts
Folder verification
Calendar integrity
Mail permissions
Shared mailbox access
OneDrive synchronization
SharePoint document validation
Teams membership verification
Application functionality testing
Document any discrepancies and resolve issues before proceeding to the next batch.
Delta Synchronization
Perform incremental synchronization to capture any changes that occurred after the initial migration.
This ensures that:
Newly received emails
Calendar updates
Contact changes
OneDrive modifications
SharePoint document updates
are successfully synchronized to the Target tenant before final cutover.
Cutover Activities
Schedule the final cutover during an approved maintenance window.
Typical cutover activities include:
Stopping mail delivery to the Source tenant
Updating MX records
Updating Autodiscover records
Updating SPF, DKIM, and DMARC records (where applicable)
Redirecting mail flow
Enabling user sign-in to the Target tenant
Validating Outlook connectivity
Verifying Teams functionality
Confirming SharePoint and OneDrive accessibility
Once validation is complete, the Target tenant becomes the production environment.
Phase 3 – Validation & Source Tenant Decommissioning
Objectives: Verify the successful migration of all data and safely retire the Source tenant.
Validation Activities and Decommissioning:
Conduct User Acceptance Testing (UAT).
Perform comprehensive validation across workloads (Mailbox, OneDrive data, SharePoint sites, and Teams access).
Execute application integration testing for third-party apps tied to M365.
Complete a final security and compliance review.
Safely clean up and decommission the old Source tenant.
