Key Considerations for Office 365 Tenant to Tenant Migration
Same Domain Transfer

Transitioning between two Office 365 tenants that share the same domain can be quite intricate, particularly if you aim to keep the domain intact. This scenario often arises from mergers, acquisitions, or changes within an organization. To facilitate a seamless migration with minimal impact on everyday activities, careful planning and implementation are essential. Here are important factors and tactics to help achieve a successful migration.


Pre-Migration Planning


Assessing Migration Requirements

Before commencing the migration from one tenant to another, it is crucial to perform a thorough evaluation of the current environment. Begin by analyzing the amount of data, the user count, the types of licenses being utilized, and any supplementary features like email security configurations or third-party integrations. Review the usage of email, calendar, OneDrive, and SharePoint to guarantee that all important data is accounted for.

Furthermore, assess the setup of custom configurations such as shared mailboxes, distribution groups, and domain records. Creating a comprehensive inventory will enable you to foresee any possible issues that may arise during the migration.


Domain Ownership Verification

A domain can only be associated with a single tenant at any given moment. Consequently, before moving the domain from the source tenant to the destination tenant, it's essential to verify that all DNS records and services tied to the domain are ready for a smooth transition between tenants.


Downtime Considerations

Transferring a domain between two tenants necessitates a brief period of unavailability, particularly during the removal from the original tenant and the subsequent verification of the new tenant. To reduce disruption for end-users, it is crucial to schedule this migration during times of low activity, such as off-peak hours or weekends. 


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Key Migration Steps


Prepare Source and Target Tenants

It's essential to adequately prepare both the source and destination tenants. This includes:

  • Data Backup: Make sure to create backups for all critical information in the source tenant. While Microsoft provides strong data redundancy, having backups minimizes the chances of unintentional data loss. 

  • License Verification: Check that the destination tenant possesses enough licenses and comparable plans to support all users and services during the migration process. Differences in license levels could result in service disruptions.

  • Prepare the Target Tenant for Domain Migration: Before transferring the domain, confirm that the receiving tenant is properly configured. This involves establishing essential DNS records (such as MX, CNAME, and TXT) for email management and making sure that users can be linked to the domain after the migration is complete.


User and Mailbox Migration

Transferring user mailboxes is a fundamental aspect of this procedure. The duration of this task can vary based on the user count and the amount of mailbox data involved. Typical approaches for this migration consist of:

  • Cutover Migration: This technique involves transferring all mailboxes simultaneously, making it suitable for smaller organizations with fewer users. While it is quicker, it necessitates a longer period of downtime. 

  • Staged Migration: This strategy enables the migration of mailboxes in groups, reducing the impact on users by extending the process over multiple days or weeks. Read our guide.


Domain Removal and Re-verification

After successfully migrating user mailboxes and services, it is necessary to detach the domain from the original tenant. This action can only be carried out once all entities (including users, groups, or shared mailboxes) linked to that domain have been disassociated from the original tenant.

Once the removal is complete, confirm the domain in the intended tenant by adjusting the DNS records as needed. Keep in mind that it may take several minutes for the domain verification to propagate, depending on your DNS configuration.


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Post-Migration Steps


Testing and Validation

Once the migration is finished, perform a comprehensive validation to confirm that all systems are functioning properly in the new tenant. Check user mailboxes, calendar features, and shared resources such as OneDrive and SharePoint. Verify that all DNS records are correctly configured and that email communication is active in the new tenant.

Users are encouraged to review their mailboxes for any missing items, while IT administrators should conduct random audits on shared resources.


End-User Communication and Support

Successful tenant-to-tenant migration hinges on clear communication with end-users. It’s essential to keep users updated on the migration schedule, potential service interruptions, and any modifications in how they access services. Providing training or technical assistance after the migration can facilitate a smoother transition and help address any problems that may arise swiftly.