"Sweeping" means moving a whole bunch of clutter en masse to another. Set up a few new folders in your email program and name them by year, quarter, or month (excluding the current year, quarter or month; i.e., do not create a "2013" folder just yet), depending on the state of your inbox and how you tend to think about time.
If you have a crowded Inbox, and want to clear it, you can. I use a similar process to the "sweeping" mentioned in the article.
It works, and allows you to focus on the important stuff.
Result: Inbox mastery.