Tenant to tenant mail migration from large to small organization

You’re correct the older guidance suggesting an “easy” tenant-to-tenant mail migration is no longer accurate for small organizations.

Microsoft’s native cross-tenant mailbox migration now requires Cross-Tenant User Data Migration, which is typically available only to Enterprise Agreement (EA) customers. Without EA and full admin access in the source tenant, the native method isn’t practical.

In scenarios like yours (splitting from a large organization with limited permissions), PST export/import is slow, manual, and risky, especially without admin rights.

In practice, many small organizations use third-party tools like CloudBik, which don’t require EA licensing and can migrate mail, calendar, and contacts directly between tenants with minimal disruption and no dependency on PSTs.

This is usually the fastest and least disruptive option for small-to-large tenant separation cases.

Migrating email from a large organization to a smaller one can be a complex process, but with proper planning and execution, it can be done seamlessly. Here's a general outline of the steps involved:

1. Assess and Plan:

• Evaluate the current environment: Understand the size, complexity, and infrastructure of the source tenant.
• Define the target environment: Determine the desired configuration and requirements of the smaller tenant.
• Identify migration scope: Decide which data and services will be migrated.
• Create a detailed migration plan: Outline the steps, timelines, and resources needed.

2. Prepare the Target Tenant:

• Create user accounts: Set up user accounts in the smaller tenant, matching the source tenant's structure.
• Configure email settings: Configure domain records, MX records, and other necessary settings.
• Set up mailboxes: Create mailboxes for each migrated user.

3. Select a Migration Tool:

• Evaluate options: Consider factors like cost, features, ease of use, and compatibility with the source and target environments.
• Popular tools: Some popular options include Microsoft 365 Migration Manager, Symantec Migration Manager, and third-party migration tools like Gs Richcopy 360 and Goodsync .

4. Prepare the Source Tenant:

• Export data: Export mailbox data from the source tenant, including emails, contacts, calendars, and other relevant information.
• Review and clean data: Identify and address any data quality issues.

5. Perform the Migration:

• Import data: Use the chosen migration tool to import the exported data into the target tenant.
• Monitor progress: Track the migration process and address any issues that arise.
• Test and validate: Verify that all data has been migrated correctly and that email is functioning properly.

6. Cutoff and Redirect:

• Set a cutoff date: Determine when to stop sending new emails to the source tenant.
• Redirect emails: Configure email forwarding rules to automatically redirect new emails from the source tenant to the target tenant.

7. Post-Migration Tasks:

• Verify completeness: Ensure that all data has been migrated successfully.
• Update DNS records: Update DNS records to point to the new email infrastructure.
• Provide user training: Educate users on the new email system and any changes in procedures.
• Monitor and troubleshoot: Continuously monitor the migrated environment and address any issues that may arise.

Additional Considerations:

• Data privacy and security: Ensure compliance with data protection regulations and implement appropriate security measures.
• Large-scale migrations: For very large organizations, consider a phased approach or utilizing specialized migration services.
• Hybrid environments: If you're migrating to a hybrid environment (on-premises and cloud), carefully plan the coexistence of both systems.

By following these steps and considering the specific requirements of your migration, you can successfully move your organization's email from a large to a small tenant.