Microsoft 365 Migration

How to Preserve OneDrive Data and Migrate Large Files to SharePoint

Maira Mehtab Sep 22, 2026 869 views

Question details

The user needs to understand how to retain OneDrive data associated with converted shared mailbox users and plan a large-scale migration of 6 TB to SharePoint within a tight timeframe.

Product: Microsoft 365
Device & OS: not provided
Scenario: Converting a user account to a shared mailbox, removing the license, and migrating a massive volume of data (6 TB) to SharePoint within three days.
Observed behavior: Without proper policies, OneDrive data may be permanently deleted when licenses are removed, and manual 'Move to' operations are impractical for massive 6 TB data transfers.

Before you start

Ensure you have Global Administrator or SharePoint Administrator privileges in Microsoft 365, and verify your destination SharePoint site has adequate storage quotas to accommodate the 6 TB of incoming data.

Solution 1Recommended

Configure Microsoft Purview Retention Policies to Preserve Data

Apply retention policies before removing licenses to ensure OneDrive data is not deleted when a user account is converted to a shared mailbox.

When a user account is converted to a shared mailbox and its license is removed, their OneDrive data is only retained for a limited grace period (usually 30 days). To prevent data loss, administrators must configure retention policies before taking away the user's license.

Access the Microsoft Purview Compliance Portal

Navigate to Data Lifecycle Management

In the left-hand navigation menu, select 'Data lifecycle management', click on 'Microsoft 365', and then go to the 'Retention policies' tab.

Create a New Retention Policy

Click 'New retention policy'. Name your policy and choose to apply it specifically to the OneDrive accounts of the users being converted to shared mailboxes.

Set the Retention Period

Specify how long you want to retain the data (e.g., indefinitely or for a specific number of years) and save the policy.

Verify and Remove License

Wait for the policy to take effect across the tenant, then proceed to safely remove the Microsoft 365 license from the converted user.

Data Secured: Once the retention policy is active, the OneDrive data will remain accessible to eDiscovery and administrators even after the account loses its active license.

Solution 2

Migrate 6 TB of Data Using Microsoft Migration Tools

For moving massive amounts of data within a tight three-day window, manual 'Move to' options are insufficient and specialized Microsoft migration tools are required.

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Frequently Asked Questions

What happens to OneDrive data when a Microsoft 365 user license is removed?

If a user account is converted to a shared mailbox and their license is removed without an active retention policy, their OneDrive data enters a grace period (typically 30 days) before being permanently deleted from the system.

Can I manually move 6 TB of data using the 'Move to' feature in OneDrive?

No, using the manual 'Move to' option in the web interface is highly impractical for massive transfers like 6 TB. It is prone to failure due to browser timeouts, network interruptions, and Microsoft 365 throttling limits. You should use the SharePoint Migration Tool (SPMT) instead.

How can I avoid throttling during a massive SharePoint migration?

To minimize throttling limits imposed by Microsoft, utilize official Microsoft Migration Tools or Migration Manager, schedule heavy data transfers during off-peak hours or weekends, and ensure data is packaged appropriately rather than sending large bursts of traffic.

Do shared mailboxes include their own OneDrive storage?

No, shared mailboxes do not inherently include their own OneDrive storage. Any OneDrive data originally associated with the user account must be secured using Purview retention policies or actively migrated to a shared SharePoint site.

Migration & Recovery