When you open a specific attachment in Outlook you might get the error saying Outlook blocked access to the following potentially unsafe attachments. Here’s a some solutions to help you unblock attachments in Outlook

Make sure that Outlook is closed. Open Registry and go to the below area depending on your office application version

Microsoft Office Outlook 2010
HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\Security
Microsoft Office Outlook 2007
HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Outlook\Security
Microsoft Office Outlook 2003
HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook\Security
Microsoft Outlook 2002
HKEY_CURRENT_USER\Software\Microsoft\Office\10.0\Outlook\Security
Microsoft Outlook 2000
HKEY_CURRENT_USER\Software\Microsoft\Office\9.0\Outlook\Security

Create a new String Value and enter Level1Remove
As the value enter the extension of the file example .pptx, if you want to add multiple extensions, seperate them with a semicolon like this, .pptx;.docx

Close regedit and open Outlook

If this doesn’t work then you might have an update that blocks as Microsoft have released a patch which blocks safe files.

If you do have the below updates according to the Office version, remove them.

Outlook 2007: KB3191898
Outlook 2010: KB3203467
Outlook 2013: KB3191938
Outlook 2016: KB3191932