If you get five hundred e-mails per day and many of them need replies on a timescale shorter than a few hours, presumably replying to e-mail is (a large part of how you do) your job. Which is fine; that means if you spend a few hours a day replying to e-mail, you're spending a few hours a day doing your job, which is as it should be. Articles like this one are addressed to people for whom e-mail is a distraction from their jobs.