A user on the same computer goes between two different SP 2013 environments. When clicking "Download a copy" on a document item in one environment, Internet Explorer asks "Do you want to open or save [File Name] from [Domain Name]?" Clicking this same button in a different environment prompts Internet Explorer to ask "Do you want to save [File Name] from [Domain Name]?" with no option to just open.
What do I need to change in the second environment to allow the open as well as save option?