You click an email attachment in Outlook, but nothing happens or you see a security warning. This prevents you from accessing important documents and images. Outlook blocks certain file types by default to protect your computer from viruses. This article explains the security settings and provides steps to safely open blocked attachments.
Key Takeaways: Unblocking Outlook Attachments
- File > Options > Trust Center > Trust Center Settings > Attachment Handling: Controls which file types are blocked and allows you to temporarily unblock specific attachments.
- Save the attachment to your desktop: Bypasses Outlook’s preview block, allowing you to open the file directly from Windows File Explorer.
- Windows Security > Virus & threat protection > Manage settings > Controlled folder access: A Windows Defender feature that can block Outlook from saving attachments if it is turned on.
Why Outlook Blocks Certain Attachments
Outlook uses a list of potentially unsafe file types to prevent malware execution. Files like .exe, .js, or .vbs can contain harmful scripts. When you receive such a file, Outlook disables the direct open command and shows a warning. This is a default security measure in the Trust Center.
Your organization’s IT administrator can also enforce additional blocking rules via Group Policy. In these cases, the attachment may be completely removed from the message. Another common cause is Windows Defender’s Controlled folder access. This feature can stop Outlook from saving files to common folders like Documents or Desktop.
Steps to Open Blocked Attachments
Use these methods to access your files while understanding the security risks involved.
Method 1: Save the Attachment to Your Computer
- Right-click the blocked attachment
In the reading pane or opened email, right-click the file name you cannot open. - Select Save As
Choose this option from the context menu that appears. - Choose a safe save location
Navigate to your Desktop or a dedicated folder. Avoid saving directly to system folders. - Open the saved file
Open File Explorer, navigate to the saved file, and double-click it. Windows will apply its own security checks.
Method 2: Adjust Outlook’s Attachment Security Settings
- Open Outlook Trust Center
Go to File > Options > Trust Center. Click the Trust Center Settings button. - Navigate to Attachment Handling
In the left pane, select Attachment Handling. - Change the security level
Uncheck the box for ‘Turn off attachment preview’. For more control, click the ‘Attachment and Document Previewers’ button to manage specific file types. - Apply and restart
Click OK twice to close the dialog boxes. You must close and restart Outlook for changes to take effect.
Method 3: Check Windows Security Settings
- Open Windows Security
Click the Start menu, type Windows Security, and open the app. - Go to Virus & threat protection
Click this option in the sidebar, then click Manage settings. - Review Controlled folder access
Scroll to find this setting. If it is On, click it to see the protected folders list. - Add an exclusion if needed
If you cannot save attachments, you may need to add your download folder as an allowed location or temporarily turn the feature off.
If Attachments Are Still Blocked
Outlook Says “Your administrator has blocked this file type”
This message means a Group Policy is in place. Contact your IT help desk. They may need to send the file via a secure portal or adjust the policy for your role. Do not attempt to bypass corporate security policies.
The attachment icon is missing or shows a paperclip with a red X
The file was stripped by an email gateway or server-level rule. Ask the sender to confirm the file was attached. They may need to compress the file into a .zip archive or rename the file extension, like changing .exe to .ex_.
You receive a “This file can’t be previewed” error
The previewer for this specific file type is not installed or is corrupted. Use the Save As method. You can also try repairing your Office installation via Windows Settings > Apps > Microsoft 365 > Modify.
Attachment Security Methods Compared
| Item | Outlook Blocked File List | Windows Controlled Folder Access |
|---|---|---|
| Purpose | Prevents opening/running dangerous file types from within the email | Prevents unauthorized apps from modifying files in protected folders |
| Scope | Specific file extensions like .exe, .js, .vbs | Any program trying to write to Documents, Desktop, etc |
| User Control | Can be adjusted in Trust Center settings | Managed in Windows Security app |
| Typical Symptom | Attachment is visible but Open button is grayed out | Save As operation fails with an access denied error |
You can now access most blocked attachments by saving them to your computer first. Always scan downloaded files with your antivirus software before opening. For persistent issues, check the Windows Security settings for Controlled folder access. A useful advanced tip is to ask senders to use cloud storage links for very large or sensitive files instead of attachments.