https://www.sitepoint.com/outlook-unblock-unsafe-attachments/

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.