Attachment Issues

Fix OneDrive File in Use Error When Dragging Files to Outlook

Rana Garcia Oct 22, 2026 869 views

Question details

Users are encountering a File in Use error preventing them from attaching open OneDrive documents to emails via drag-and-drop, despite the manual attachment button working.

How to Fix the File in Use Error When Dragging OneDrive Files to Outlook

Product: Microsoft Outlook and OneDrive
Device & OS: not provided
Scenario: Dragging and dropping an open OneDrive file, such as an Excel spreadsheet, directly into a Microsoft Outlook desktop message.
Observed behavior: The system displays a File in Use error and blocks the drag-and-drop action, even though using the Attach File button from the Outlook ribbon works normally.

Before you start

Ensure your Outlook and OneDrive desktop applications are updated to the latest versions, and verify that you are signed into both applications using the exact same Microsoft account.

Solution 1Recommended

Disable File Collaboration in OneDrive Settings

Disabling the OneDrive file collaboration feature often removes the synchronization locks that cause conflicts with Outlook drag-and-drop actions.

Many users assume that disabling 'Files On-Demand' will fix this issue, but testing shows that 'File collaboration' is usually the culprit. Disabling this setting stops OneDrive from heavily locking the file for real-time co-authoring during background syncs.

Open OneDrive Settings

Click the OneDrive cloud icon in your system tray, click the gear icon (Help & Settings), and select Settings.

Navigate to Advanced Settings

Go to the Sync and backup tab and expand the Advanced settings section.

Turn off File Collaboration

Locate the 'File collaboration' toggle and turn it off. Restart Outlook and try dragging and dropping the file again.

Disable File Collaboration in OneDrive Settings

Effective Workaround: For most environments, this immediately restores normal drag-and-drop attachment functionality in the Outlook desktop app.

Solution 2

Set the File to 'Always Keep on This Device'

Ensuring the file is fully downloaded and available locally can prevent cloud sync delays that trigger the File in Use error.

Solution 3

Save, Close, and Use the Attach File Button

A quick manual workaround if you need to send your email immediately without altering OneDrive sync settings.

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Frequently Asked Questions

Why does disabling Files On-Demand not fix the attachment error?

Files On-Demand simply controls whether your files are stored locally on your hard drive or strictly in the cloud. The File in Use error is typically caused by OneDrive's File Collaboration feature, which locks the file for real-time co-authoring and background syncing. These are separate settings.

Can I attach a OneDrive file while it is still open in Excel?

Yes, but you generally need to use the Attach File button located in the Outlook ribbon. Dragging and dropping an open, syncing file directly from File Explorer often triggers a file lock error from the Windows file system to prevent data corruption.

What should I do if the error continues after changing my OneDrive settings?

If the problem remains after turning off File Collaboration, ensure both Microsoft Office and OneDrive are fully updated. If you are using a business account, the issue might require an investigation of your specific IT environment. You should contact your Microsoft 365 administrator to submit a support ticket.

Outlook & Email Problems