If your job is being reactive and sending e-mails it can be the center of gravity. This is particularly true for investors, executives and sales people.

However, if your job requires you to "build" whether it's code, slides, designs, etc then proactive work planning is essential and turning emails into tasks to be deferred is essential. I think of these as people who teeter between the maker and managers schedule: http://www.paulgraham.com/makersschedule.html

Obviously, I'm biased because I build a Daily Planner: Sunsama (https://sunsama.com)