File Sharing Problems

Fix Word Mail Merge Data Source Open in Another Application Error

John Wilson Oct 22, 2026 868 views

Question details

Users are unable to complete a mail merge because Word incorrectly detects that the recipient list or data source file is already in use by another program.

How to Fix Word Mail Merge Data Source Open in Another Application

Product: Microsoft Word
Device & OS: not provided
Scenario: Attempting to link a recipient data source (like an Excel spreadsheet) to a mail-merge document, especially when files are stored in OneDrive or other synchronized folders.
Observed behavior: Word blocks the mail merge and displays an error message stating that the data source is open in another application, even when the file appears to be closed.

Before you start

Ensure that the data source file (such as your Excel spreadsheet) is completely closed and not currently opened in any other window or application before attempting the mail merge.

Solution 1Recommended

Move Files to a Local Non-Synced Folder

Bypass background sync locks caused by OneDrive or network drives by moving your mail merge files to a simple local directory.

Cloud synchronization services like OneDrive continuously scan and upload file changes. This background activity can place a temporary lock on your data source, causing Word to believe the file is open in another application.

Create a new local folder

Open File Explorer, navigate to your local C: drive, and create a new folder. Name it something simple like 'C:\Merge Files'.

Relocate your files

Copy and paste both your main Word mail-merge document and your recipient data source (e.g., Excel list) into this newly created folder.

Reattach the data source

Open the Word document from the new folder. Go to the 'Mailings' tab on the ribbon, click 'Select Recipients', and choose 'Use an Existing List'.

Select the local file

Browse to 'C:\Merge Files', select your data source, and proceed with your mail merge.

Workaround Successful: Moving files to a non-synced local folder is the most reliable way to prevent background synchronization tools from locking your mail merge data.

Solution 2

Force Close Hidden Office Processes

End background instances of Microsoft Excel or Word that might be silently holding the data source open.

Solution 3

Check File Properties and Remove Restrictions

Verify that your data source is not marked as read-only or blocked by system security settings.

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Frequently Asked Questions

Why does Word think my Excel data source is open when it is clearly closed?

This typically occurs because a background syncing service like OneDrive is actively scanning or uploading the file, placing a temporary lock on it. It can also happen if a hidden background process of Excel is still running in your Task Manager.

Can I perform a mail merge with a data source stored directly on OneDrive?

Yes, but if you encounter file lock errors, you will need to temporarily pause OneDrive syncing. Click the OneDrive cloud icon in your system tray, click the Settings gear icon, and select 'Pause syncing' before starting your mail merge in Word.

Does the 'Data Source Is Open' error affect older versions of Microsoft Office?

While it is most common in Microsoft 365 due to tight integration with cloud services, this error can also occur in older versions like Office 2016 or 2019 if the data file is locked by another user on a shared network drive or marked as read-only.

Document & File Issues