A good way to deal with the busy work is in “batches.” Rather than reactively living in your inbox, schedule a few intervals when you process emails, return phone calls, and shuffle the papers that need shuffling. After that session is over, turn off notifications, silence the phone, and get back to important stuff. Three batches a day works for me, but a job that requires frequent interaction may need more. The point is to be able to control and schedule these periods as much as possible so they don’t creep into the time you’re doing deep work.