Fix: Outlook blocked access to the following potentially unsafe attachments…

How to Unblock Unsafe Attachments in Microsoft Outlook

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…

WARNING: YOU’LL NEED TO EDIT THE REGISTRY!

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 stop working...
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.

DO THIS AT YOUR OWN RISK!

If you still want to proceed, below are the steps to take:

1. Close Outlook

2. Run regedit.exe (Start -> cmd.exe, then type regedit [ENTER])
Navigate to:

HKEY_CURRENT_USER\Software\Microsoft\OfficeXX.X\Outlook\Security

Where XX.X indicates your version of Outlook:

·         15.0 for Microsoft Office / Outlook 2013

·         14.0 for Microsoft Office / Outlook 2010

·         12.0 for Microsoft Office / Outlook 2007

·         11.0 for Microsoft Office / Outlook 2003

·         10.0 for Microsoft Office / Outlook 2002

·         9.0 for Microsoft Office / Outlook 2000

3. Create a new STRING 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, shortcuts, VBScript, and exe files, enter:

.js;.lnk;.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.