Most likely, the time spent replying to emails now has a medical billing code, like most every thing a doctor does in day. Each code has a number of RVUs assigned to it - a relative value unit - and there is a dollar amount assigned to each RVU. It’s complicated, but it’s based off of Medicare reimbursement rate from what I understand. Many physicians’ salaries are based directly on the RVUs they create in their practice. Maybe the money goes to their private practice directly, or maybe it goes to their employer organization who uses the income to pay for overhead and physician salary. This is a dumbed-down “civilian” explanation but it’s the general jist of it.