Nir Eyal says the difference between work and distraction isn't what you do, it's whether you planned to do it. Checking email on purpose is fine. Checking it because you drifted there is a distraction, even if it's your job.
Chapters
Now, this is important for a few reasons. One, I think it frees us from this ridiculous moral hierarchy that what I do with my time is fine. But with what you do with your time, that's frivolous. So you spending time on Facebook or Candy Crush, no, that's a waste of time. But me watching football for three hours, that's okay. Why? If they're done with intent, if these are things that are consistent with your values that you plan to do with your time, they're both perfectly fine pastimes. The other thing that's important about this dichotomy is that we can realize that anything can become a distraction. For example, in my case, I would sit down at my desk and I would promise myself that, now I'm going to get to work. Now I'm going to do that thing that I'm procrastinating on. I'm going to finally do what it is I said I'm going to do. Right after I check email, right after I scroll that Slack channel. And something that felt worky. It felt like something I needed to do anyway for my work. We all have to check email. That's just part of our jobs. However, if it's not what you plan to do with your time, if it's something that you are not doing with intent, it is just as much of a distraction.