I recently upgraded from Windows 7 to Windows 10. After upgrade, Outlook 2010 still asks "how do you want to open this" when I double-click to .PDF or URL.
I checked "Always use this app", but it didn't help. All other files (word, excel, pictures) open fine. I think Microsoft Edge is the problem, but don't know how to resolve it.
When I open .PDF from desktop or documents folder, it opens fine. The problem is in Outlook only.