OneDrive for Business file server migration breaks recent links for mergers: Fix Guide

When a company merges with or acquires another business, IT teams often migrate file server data into OneDrive for Business. After the migration, users discover that shared links to files and folders that were sent before the migration no longer open. These broken links return errors like “This item might not exist or is no longer available” or redirect to a blank page. This problem occurs because legacy file server paths do not map to the new OneDrive URLs, and the sharing permissions are not transferred during a standard file copy. This article explains why these links break and provides a structured fix to restore access to shared content after a merger migration.

Why File Server Migration Breaks Existing OneDrive Links

When you move files from an on-premises file server to OneDrive for Business, the underlying storage location changes completely. Each file in OneDrive gets a unique URL based on its site collection ID, folder path, and file name. The original file server path, such as \\fileserver\shared\project.xlsx, has no relationship to the new OneDrive URL. Any link that was created before the migration points to the old path or to a temporary location that no longer exists.

During a merger migration, IT teams often use tools like Microsoft Migration Manager or third-party utilities to copy data. These tools copy the file content but do not preserve the sharing links or the permissions associated with those links. The result is that every link sent before the migration becomes a dead link. Additionally, if the source file server is decommissioned after the copy, there is no fallback path to redirect users.

Another factor is that user identity mapping may not be complete. In a merger, users from the acquired company might have new Microsoft 365 accounts but their old file server permissions were mapped to their old domain accounts. If the migration tool does not correctly map the old security identifier to the new user principal name, the new OneDrive folder permissions are empty. This causes access denied errors even if the link itself is technically valid.

Steps to Fix Broken Links After a OneDrive Migration

The following steps assume that the file data has already been copied to OneDrive for Business and that the source file server is still available or at least the original link data can be retrieved. If the source server is gone, you will need to rebuild links manually from the OneDrive sharing history.

1. Identify all broken links from the merge period
   Use the Microsoft 365 admin center audit log to find sharing events. Go to Microsoft 365 admin center > Audit > Search. Set the date range to the migration period. Filter by activity “Shared file, folder, or link” and “Created link”. Export the results to a CSV file. This gives you a list of all links that were generated before the migration.
2. Map each broken link to the new OneDrive location
   Open the CSV file. Each row contains the target file path from the file server. For each file, locate its new OneDrive URL. You can find the new URL by going to the OneDrive web interface, navigating to the same file, and copying the address from the browser. Create a mapping table with the old path and the new URL.
3. Recreate the sharing links from the new OneDrive location
   For each file in the mapping table, generate a new link from OneDrive. Right-click the file in OneDrive and select Share. Choose the same link type that was used originally: Anyone, People in your organization, or Specific people. Copy the new link. Paste it into a new column in the mapping table next to the old link.
4. Notify affected users about the new links
   Use Microsoft 365 Groups or a distribution list to send an email to the users who originally shared the files. Include the old link and the new link in the email. Ask them to replace the old link in any shared documents, emails, or chat messages. You can automate this step by running a PowerShell script that sends emails from a shared mailbox.
5. Set up a URL redirect using SharePoint link forwarding
   If you have a large number of links, consider using SharePoint link forwarding. This feature is available in SharePoint Online and can redirect old file server URLs to new OneDrive URLs. Go to SharePoint admin center > Policies > Link forwarding. Add a forwarding rule that maps the old file server path prefix to the new OneDrive site collection URL. Note that this only works if the old links were in the format https://company.sharepoint.com/sites/oldpath, not \\fileserver paths.
6. Verify that permissions are correctly set on the new files
   After recreating links, check that the intended recipients have access. Open the new link in an incognito browser window. Sign in with a test account from the acquired company. Confirm that the file opens without errors. If access is denied, adjust the sharing permissions on the file in OneDrive by clicking Share and adding the missing users or groups.

If Broken Links Persist After the Main Fix

OneDrive shows “This item might not exist or is no longer available”

This error appears when the link points to a file that was deleted during the migration or moved to a different site collection. Check the OneDrive recycle bin for the affected user. Go to OneDrive > Recycle bin. If the file is there, select it and click Restore. Then recreate the link. If the file is not in the recycle bin, the file was permanently deleted. You must restore it from a backup or ask the user to re-upload the file.

Link works but the file opens with a blank page

A blank page usually indicates a permission mismatch. The user who opens the link does not have at least Read access to the file. To fix this, go to the file in OneDrive, click Share, and click the link settings icon. Under “Who can access”, select the appropriate option. If you need to grant access to all users in the acquired company, add their Microsoft 365 group to the file permissions. Do not use the “Anyone” link for sensitive data.

Link redirects to the old file server path

This happens when the link was generated by a migration tool that created a shortcut or a redirect page. The link itself is a URL that points to the old server. To resolve this, you must delete the old redirect and replace it with a direct link to the OneDrive file. Use SharePoint link forwarding to create a permanent redirect from the old URL to the new one. Test the redirect by opening the old link in a browser after the rule is active.

OneDrive Links Before and After Migration: Key Differences

Item	Pre-Migration Link (File Server)	Post-Migration Link (OneDrive)
Link format	\\server\share\folder\file.xlsx	https://tenant-my.sharepoint.com/personal/user/Documents/folder/file.xlsx
Access control	NTFS permissions on the file server	OneDrive sharing permissions and site permissions
Link expiration	No expiration unless explicitly set	Default 30 days for Anyone links; can be set to never expire
External sharing	Controlled by VPN or firewall rules	Controlled by OneDrive sharing policies in admin center
Link portability	Only accessible on the corporate network	Accessible from any device with internet and authentication

The table above shows that the link structure and access model change completely after migration. You cannot simply copy files and expect links to work. You must actively recreate or redirect each link. The most important change is the shift from network path-based access to URL-based access with cloud permissions. This requires a deliberate link migration plan before the cutover date.

You can now identify broken links from the audit log, map them to new OneDrive locations, recreate the sharing links, and notify users. Next, set up SharePoint link forwarding to automate redirects for common path patterns. An advanced tip is to use the Microsoft Graph API to programmatically recreate links in bulk. The Graph API endpoint /sites/{site-id}/drive/items/{item-id}/createLink can generate new links and return them in JSON format, which you can then merge into your mapping table.