why are the links not working in the dailyish email?

so we have had a few (two people) report that the links in the dailyish email were not working.. aka they were just showing up black, not as real links. so I created this thread so that we could explain the problem and direct people here in the future if they are having this problem.

I think there must be a setting in the application they use to read their emails that make them be displayed in plain text vs. html or rich-text.

What software do they use for reading their emails?