Step-by-Step Guide to Migrating Shared Mailboxes Between Office 365 Tenants In Hindi

Migrating shared mailboxes between Office 365 tenants can seem daunting, especially for organizations with multiple mailboxes or complex setups. Whether you’re merging companies, restructuring your IT environment, or managing tenant-to-tenant migrations during a company acquisition, a clear, methodical approach is critical to avoid data loss and downtime. In this guide, we’ll walk you through the entire process of migrating shared mailboxes between Office 365 tenants step by step.

What Is a Shared Mailbox in Office 365?

A shared mailbox in Office 365 allows multiple users to access and send emails from a common email address. Shared mailboxes are typically used for departmental email addresses such as support@company.com, info@company.com, or sales@company.com. They do not require a separate license if the mailbox size is under 50 GB, making them a cost-effective collaboration tool.

Migrating shared mailboxes is slightly different from migrating user mailboxes because shared mailboxes do not have login credentials in the traditional sense. Instead, permissions are assigned to users who need access. This distinction affects how we approach migration.

Why Migrate Shared Mailboxes Between Tenants?

There are several scenarios where migrating shared mailboxes is necessary:

1. Company Mergers and Acquisitions: When two companies merge, IT administrators often need to consolidate tenants.

2. Tenant Restructuring: Organizations may consolidate Office 365 tenants to simplify management or reduce costs.

3. Regional or Departmental Changes: Companies may reorganize departments, requiring shared mailbox migration.

4. Compliance and Archiving: Certain industries require archiving or transferring historical emails to a new tenant.

Whatever the reason, careful planning ensures smooth migration without interrupting day-to-day operations.

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Prerequisites Before Migration

Before starting the migration process, ensure the following:

1. Admin Access: You must have Global Administrator rights in both the source and target tenants.

2. Licensing: Verify that the target tenant has enough licenses for any mailboxes exceeding shared mailbox limits.

3. Directory Sync: If using Azure AD Connect, ensure that your directory sync is configured correctly in both tenants.

4. Backup: Always back up the shared mailboxes using tools like Outlook PST export or third-party backup solutions.

5. Migration Tool: Consider using Microsoft-approved migration tools or third-party software that supports tenant-to-tenant migrations.

Having these prerequisites in place reduces the risk of errors and data loss.

Step 1: Assess Shared Mailboxes for Migration

Start by identifying the shared mailboxes you need to migrate. Use PowerShell to generate a list of shared mailboxes in the source tenant:

# Connect to Exchange Online
Connect-ExchangeOnline -UserPrincipalName admin@sourceTenant.com

# Get all shared mailboxes
Get-Mailbox -RecipientTypeDetails SharedMailbox | Select DisplayName, PrimarySmtpAddress

Review the list and confirm the mailbox size, number of items, and assigned permissions. Larger mailboxes may require extra planning, as migration could take longer.

Step 2: Prepare the Target Tenant

In the target Office 365 tenant, create corresponding shared mailboxes. Use the Exchange Admin Center (EAC) or PowerShell:

# Connect to Exchange Online on target tenant
Connect-ExchangeOnline -UserPrincipalName admin@targetTenant.com

# Create a shared mailbox
New-Mailbox -Shared -Name "Support" -PrimarySmtpAddress support@targetTenant.com

Assign permissions to users in the target tenant who need access. Ensure that users have at least Full Access and Send As permissions.

Step 3: Choose a Migration Method

There are multiple methods to migrate shared mailboxes:

3.1 Manual PST Export/Import

1. Use Outlook to export the shared mailbox to a PST file.

2. Import the PST file into the target tenant’s shared mailbox.

Pros: Simple for small mailboxes.
Cons: Time-consuming for large mailboxes, manual effort, and potential for errors.

3.2 PowerShell Cross-Tenant Migration

Microsoft supports tenant-to-tenant migrations using PowerShell scripts and Exchange Online PowerShell. This method is more efficient for medium to large environments.

3.3 Third-Party Migration Tools

Popular tools like BitTitan MigrationWiz, CodeTwo Office 365 Migration, or Quest On Demand Migration automate the process, handle permissions, and reduce downtime.

Pros: Automated, less error-prone, faster.
Cons: Requires licensing or subscription.

Step 4: Grant Source Tenant Permissions

To migrate mailbox content efficiently, you need to grant Full Access permissions to the migration account in the source tenant:

Add-MailboxPermission -Identity support@sourceTenant.com -User migrationadmin@sourceTenant.com -AccessRights FullAccess -InheritanceType All

This allows the migration tool or script to read mailbox content without interruptions.

Step 5: Migrate Mailbox Content

Depending on your chosen method:

• PST Import/Export: Use Outlook’s Import/Export Wizard. Open the PST file and copy data to the target shared mailbox.

• PowerShell Migration: Use New-MailboxExportRequest and New-MailboxImportRequest to move mailbox items.

• Migration Tools: Follow the tool’s wizard to select source and target mailboxes, configure filters, and start migration.

During migration, track progress and check for errors.

Step 6: Verify Permissions and Data Integrity

After migration:

1. Verify that the shared mailbox is visible to the intended users.

2. Check Full Access and Send As permissions.

3. Confirm that all emails, folders, and calendar items have been migrated successfully.

4. Test sending and receiving emails from the migrated shared mailbox.

Use PowerShell to verify permissions:

Get-MailboxPermission -Identity support@targetTenant.com

Step 7: Decommission Source Mailboxes

Once you confirm the migration is successful:

1. Notify users about the cutover.

2. Remove migration account permissions from the source mailbox.

3. Delete or archive the source shared mailbox to avoid duplication and confusion.

Always keep a backup for a few weeks in case you need to restore items.

Step 8: Post-Migration Cleanup

• Update distribution lists or email forwarding rules that reference the old mailbox.

• Reconfigure any automation or workflows tied to the shared mailbox.

• Inform users of any new URLs or login changes.

• Monitor mailbox performance for a few days to ensure smooth operation.

Best Practices for Tenant-to-Tenant Shared Mailbox Migration

1. Plan Ahead: Create a migration plan with timelines and milestones.

2. Communicate: Notify users about downtime or changes.

3. Test Migration: Always test with one shared mailbox before migrating all.

4. Backup First: Never skip the backup step.

5. Automate When Possible: For multiple mailboxes, third-party tools reduce errors and save time.

6. Document the Process: Keep a record for compliance or future reference.

Conclusion

Migrating shared mailboxes between Office 365 tenants may appear complex, but with a clear, step-by-step approach, it can be accomplished smoothly. From assessing mailbox size to verifying post-migration data integrity, each stage is critical for a successful transition. By following best practices and leveraging automation tools where appropriate, IT teams can minimize downtime, ensure compliance, and maintain seamless communication across the organization.

Tenant-to-tenant migrations are not just a technical task—they are an opportunity to streamline operations, optimize email management, and improve overall IT efficiency. With careful planning and execution, your shared mailbox migration can be completed efficiently and securely.