A Step-by-Step Guide to Merging Multiple Microsoft 365 Tenants into One

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Merging multiple Microsoft 365 tenants into a single, cohesive environment can be a complex and challenging task. This guide provides a structured approach to migrating users, mailboxes, and resources, ensuring a smooth transition while minimizing disruptions to your organization. From planning to post-migration support, this article covers the essential steps for a successful tenant consolidation.

Introduction

Consolidating multiple Microsoft 365 tenants into a single tenant can be an essential move for organizations seeking to streamline their operations, reduce costs, and simplify administration. However, this process is far from straightforward. Unlike some other platforms, Microsoft 365 does not offer a built-in mechanism for merging tenants directly. Instead, organizations must rely on careful planning and a methodical approach to migrate data, users, and resources from secondary tenants into a primary one.

This guide walks through the key steps involved in this migration process, providing practical advice on how to prepare your target tenant, plan the migration, and ensure that the transition is as smooth as possible for end-users. Whether you’re dealing with mailboxes, SharePoint sites, or Microsoft Teams data, this guide will help you navigate the complexities of tenant consolidation.

The Guide

Merging multiple Microsoft 365 tenants (like those associated with @webinar.onmicrosoft.com, @webinarlimited.onmicrosoft.com, and @webinarlimitedproject.onmicrosoft.com) into a single tenant (@webinar.onmicrosoft.com) is a complex process. Unfortunately, Microsoft does not provide a direct method to merge tenants. However, you can achieve the same outcome by migrating resources, data, and users from the secondary tenants into the primary one.

Here’s an outline of the steps you can take:

1. Prepare the Target Tenant (@webinar.onmicrosoft.com)

  • Ensure that your target tenant is properly configured to receive users, mailboxes, and other resources.
  • Verify that you have sufficient licenses to accommodate all users and services from the other tenants.

2. Plan the Migration

  • Create a comprehensive migration plan, including timelines, user communication, and fallback strategies.
  • Identify all the resources that need to be migrated, such as user accounts, mailboxes, SharePoint sites, OneDrive files, and Teams data.

3. Migrate Users and Mailboxes

  • Option A: Manual Migration
    • For each user, create new user accounts in the target tenant.
    • Export mailboxes from the source tenants and import them into the target tenant using PST files or a third-party tool.
  • Option B: Third-Party Tools
    • Use third-party tools such as BitTitan MigrationWiz or Quest On Demand Migration to automate the migration of users and mailboxes.
  • Option C: Hybrid Configuration
    • For Exchange Online migrations, you can set up a hybrid configuration, which allows you to migrate mailboxes in batches.

4. Migrate Other Resources

  • SharePoint and OneDrive: Use the SharePoint Migration Tool (SPMT) or a third-party tool to move SharePoint sites and OneDrive files.
  • Teams: If you use Microsoft Teams, consider third-party tools like AvePoint or Quest to migrate Teams data, including chat history, channels, and files.

5. DNS and Domain Configuration

  • If custom domains are used in the secondary tenants (@webinarlimited.onmicrosoft.com and @webinarlimitedproject.onmicrosoft.com), remove them from these tenants and add them to the target tenant (@webinar.onmicrosoft.com).
  • Update DNS records accordingly.

6. Verify and Test

  • After the migration, thoroughly test to ensure that all data has been successfully transferred.
  • Ensure that users can access their data and services as expected.

7. Decommission the Old Tenants

  • Once you have verified that all data and services have been successfully migrated, you can proceed to decommission the old tenants.
  • Cancel subscriptions and ensure that no residual data remains in the old tenants.

8. Communicate with Users

  • Keep users informed throughout the migration process, especially if there will be any expected downtime or changes in how they access their services.

9. Post-Migration Support

  • Provide support to users after the migration in case they encounter any issues.
  • Monitor the system to ensure everything is functioning smoothly.

Considerations:

  • Licensing: Ensure that the target tenant has the appropriate licenses for all users and services.
  • Compliance: Be mindful of any regulatory or compliance requirements that may affect the migration.
  • Third-Party Tools: Depending on the complexity of your environment, third-party tools may be necessary to facilitate the migration.

Because this is a complex and potentially disruptive process, you might want to consider engaging with a Microsoft Certified Partner or a migration specialist to assist with the project, especially if the tenants are large or have significant amounts of data.

Conclusion

Merging multiple Microsoft 365 tenants into a single environment is a complex process that requires careful planning, thorough testing, and a structured approach to migration. While the absence of a direct merging tool from Microsoft adds to the challenge, by following a detailed plan and utilizing the appropriate tools, organizations can successfully consolidate their tenants with minimal disruption. The key to a successful migration lies in meticulous preparation, clear communication with users, and ongoing support after the transition. For organizations with large or complex environments, engaging with a Microsoft Certified Partner or migration specialist may be a prudent step to ensure a seamless integration.

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