How to Unblock Unsafe Attachments in Microsoft Outlook

This article was written in 2010 and remains one of our most popular posts. If you’re keen to learn more about email systems, you may find this recent article on taking control of your inbox of great interest.

There’s a vast range of desktop and online email clients but it’s hard to beat Microsoft Outlook. The application has been around since 1997 and, despite a few dodgy decisions regarding HTML rendering, it’s still the email client of choice for me and many others. Unfortunately, there’s an Outlook message web developers hate: Outlook blocked access to the following potentially unsafe attachments… Thanks Microsoft. I know why you’re blocking that JavaScript file, but I know what it is and I really, really want it. Outlook doesn’t allow you to unblock unsafe attachments. Fortunately, there is a way to obtain the file and prevent the embarrassment of requesting a renamed version. Before we start…

tip: BIG REGISTRY WARNING!

We’re about to delve into the Windows registry. Please move along if you don’t know what the registry is or have never dabbled with it before. It’s a dangerous place — once false move and your PC will explode.

The fix will also reduce Outlook security settings. That’s not a problem for someone with reasonable IT knowledge, but it’s not for everyone.

Still here? OK, here’s what you do: 1. Close Outlook 2. Run regedit.exe Navigate to:

HKEY_CURRENT_USERSoftwareMicrosoftOfficeXX.XOutlookSecurity

Where XX.X indicates your version of Outlook:

14.0 for Microsoft Office 2010
12.0 for Microsoft Office 2007
11.0 for Microsoft Office 2003
10.0 for Microsoft Office 2002
9.0 for Microsoft Office 2000

3. Create a new value Create a new string value key in that location named:

Level1Remove

4. Choose your ‘safe’ file types Edit the key and enter a list of attachment extensions you want to unblock. Each should start with a period and be separated with a semi-colon. For example… To unblock JavaScript files only, enter:

.js

To unblock JavaScript, VBScript, and exe files, enter:

.js;.vbs;.exe

Click OK to save the value then exit regedit. 5. Restart Outlook

The attachment should be magically unblocked. Try rebooting if that’s not the case. Microsoft provide a useful support page with alternative options and configuration advice for those using Exchange Server.

Frequently Asked Questions (FAQs) about Outlook’s Unsafe Attachments

Why does Outlook block certain attachments?

Outlook has a built-in security feature that automatically blocks access to attachments it deems potentially unsafe. This includes file types such as .exe, .bat, .vbs, and .js, among others. These file types are often used by malicious software, hence Outlook’s precautionary measure. The aim is to protect your computer and data from potential threats.

How can I unblock a safe attachment that Outlook has blocked?

If you’re certain that an attachment is safe but Outlook has blocked it, you can unblock it by changing the settings in the Registry Editor. However, this should be done with caution as incorrect changes in the Registry Editor can cause serious problems. Always ensure you have a backup of your data before making any changes.

Can I customize the types of attachments that Outlook blocks?

Yes, you can customize the types of attachments that Outlook blocks by modifying the Level1Add and Level1Remove registry entries. This allows you to add or remove specific file types from Outlook’s list of potentially unsafe attachments.

What should I do if I can’t access the Registry Editor to unblock attachments?

If you’re unable to access the Registry Editor, it’s recommended to contact your system administrator or IT support team. They have the necessary permissions and expertise to safely make changes to the system settings.

Is there a way to recover a blocked attachment?

If an attachment has been blocked by Outlook, it’s not deleted but simply inaccessible. You can recover it by changing the settings in the Registry Editor. However, if you’re not comfortable doing this, consider asking the sender to resend the file in a different format that’s not blocked by Outlook.

Are there any risks associated with unblocking attachments in Outlook?

Unblocking attachments in Outlook can expose your computer to potential threats. If you decide to unblock attachments, ensure you have a reliable antivirus software installed and always scan the attachments before opening them.

Can I unblock attachments in Outlook on a Mac?

The process of unblocking attachments in Outlook is different on a Mac compared to a Windows PC. On a Mac, you’ll need to use the Terminal application to make changes to Outlook’s settings.

Why does Outlook block attachments even from trusted senders?

Outlook’s security feature doesn’t distinguish between trusted and untrusted senders when blocking potentially unsafe attachments. It’s designed to protect against all potential threats, regardless of the source.

Can I disable Outlook’s attachment blocking feature?

While it’s possible to disable Outlook’s attachment blocking feature, it’s not recommended due to the potential security risks. If you frequently receive blocked attachments, consider asking the sender to use a different file format.

What alternatives are there to sending blocked attachments?

If you’re having trouble sending a blocked attachment, consider using a different file format or compressing the file into a .zip file. Alternatively, you can use a cloud storage service like OneDrive or Dropbox and share the link instead.