Whether it’s Outlook, Word, or any other Office product in the 2010, 2013, or 2016 versions, if attempting to add an attachment causes the application to crash, the solution is a simple one, though likely not satisfying.
The issue first began after the Creators Update rolled out, otherwise known as Windows 10 version 1703. It’s still unknown why exactly this version is the cause of the issue, however merely having this version is not what’s causing the problem.
Chances are good you have created a “God Mode” shortcut somewhere on your computer, whether it’s the desktop, Documents, or anywhere else. Once you delete that shortcut, your problem will be fixed. Sorry about that, I know it’s handy. Better luck in future versions.