User intermittently can't open emailed Excel files on one specific computer

It sounds like the issue may be related to the specific configuration or settings on the user's computer. Here are a few troubleshooting steps you can consider:

1. Check for Updates: Ensure that the Office applications on the problematic computer are fully updated. Sometimes, updates can resolve compatibility issues.
2. Repair Office Installation: You can try repairing the Office installation on that computer. This can fix any corrupted files that might be causing the issue.
3. Disable Add-ins: Check if there are any add-ins enabled in Excel that might interfere with opening files. Disabling them temporarily can help identify if they are the cause.
4. Clear Office Document Cache: Sometimes, clearing the Office Document Cache can resolve issues with opening files. You can find instructions on how to do this in the Microsoft support documentation.
5. Check File Permissions: Although you mentioned that the file is unblocked, ensure that the user has the necessary permissions to open files from the senders. Sometimes, permissions can be set at the file or folder level that restrict access.
6. Test with Different User Profile: If possible, create a new user profile on the same computer and see if the issue persists when logged in with that profile. This can help determine if the problem is user-specific or system-wide.
7. Check Windows Firewall Settings: Since the issue might be related to network settings, ensure that the Windows Firewall is configured correctly and is not blocking any necessary connections.

If these steps do not resolve the issue, it may be beneficial to gather more details about any error messages or logs that occur when the user tries to open the file. This information can provide further insights into the problem.

References:

• Cannot open Word documents or Excel spreadsheets from an external source in Outlook
• You receive an error message when you try to open an Office document

Hi @Chris Dalton,

Welcome to the Microsoft Q&A forum.

Thank you for reaching out to us. Please allow me to provide you with the following information:

This issue often occurs because Outlook’s temporary folder (OutlookSecureTempFolder) becomes full or encounters filename conflicts, preventing Outlook from creating a new copy of the file to open it.

Step 1: Clear Outlook cache

If you are using Outlook Classic, please follow these steps:

1. Make sure Outlook is completely closed.
2. Press Windows + R.
3. Enter: %localappdata%\Microsoft\Outlook
4. Open the RoamCache folder
5. Delete all files inside this folder.

If you are using the New Outlook, please follow these steps:

1. Press Windows + R.
2. Enter the command: olk.exe --devtools

1. Select Application.

1. Under Local Storage and Cookie, choose outlook.office.com.
2. Right‑click and select Clear.

Step 2: Check Protected View settings in Excel

1. Open Excel → File → Options → Trust Center → Trust Center Settings → Protected View.

1. Temporarily uncheck all options in Protected View, then click OK.
2. Try opening the file again from Outlook.

(After testing, please re‑enable Protected View to ensure security.)

Step 3: Open Outlook in Safe Mode

1. Completely close Outlook.
2. Press Windows + R, then enter: outlook.exe /safe
3. Press Enter.
4. Try opening the attachment again.

If it opens successfully, the issue may be caused by an Add-in. Please disable Add-ins one by one under File → Options → Add-ins to identify the problematic one.

Step 4: Check your security software

• Temporarily disable your antivirus software and try opening the file again.
• If it works, please add Outlook and Excel to the antivirus software's Trusted List.

Since the problem only occurs on a specific machine, it is very likely related to that device’s configuration or settings. If the steps above still do not resolve the issue, I recommend creating a support ticket with Microsoft’s technical support team through the Microsoft 365 Admin Center.

As a moderator-level supporter, I do not have the tools needed to investigate deeper into your system. When you create a ticket, a live agent (technician) will contact you directly and assist with a more detailed check. This will not affect your personal or organizational data — it is simply to ensure no configuration or policy is unintentionally blocking Excel files from opening via Outlook.

 You can refer to the following document: https://dori-uw-1.kuma-moon.com/en-us/microsoft-365/admin/get-help-support?view=o365-worldwide

I hope the information above is helpful to you. Please try the steps and let me know the results. If the issue persists, I’m ready to assist you further.

Thank you for your patience and understanding. If you have additional questions, feel free to leave them in the comments under the post so I can continue supporting you.

I look forward to your response.

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