While an overflowing inbox is undoubtedly overwhelming, the emails it contains are not created equally, says organization expert Claire Diaz-Ortiz . In her book Design Your Day: Be More Productive, Set Better Goals, and Live Life on Purpose , she says creating a strategy and identifying the types of email you have can help you tame your inbox.

“At face value, it seems like email is the biggest blow to productivity the world has ever seen. But first impressions can be deceiving,” she writes. The first step is to know the two rules of email, and understanding these “truths” will explain why some email management systems work and some don’t.

Real productivity is about managing your energy, not your time.

1. Handle It In Bulk. Reading and responding to email in one sitting or at designated times of day helps you be as productive as possible, because switching between tasks robs you of 40% of your productivity, writes Diaz-Ortiz. Avoid the drain by doing it all at once. List “email” as a task on your schedule, checking it once a day or at two or three preplanned times, such as noon, 3 p.m. and 6 p.m.

2. Do It When You Have Low Energy. Real productivity is about managing your energy, not your time, says Diaz-Ortiz. “Times of peak energy should be used for the most difficult things on your plate, and those that require intense focus. The vast majority of the time, that is not email,” she writes. This means checking your email first thing in the morning is a bad idea; this time should be reserved for your most difficult tasks and those that require a fresh mind.

While email doesn’t produce tangible results, it is a necessary part of worklife. Once you understand the rules, Diaz-Ortiz says thinking of email in categories will help you handle each one accordingly:

Daily or urgent emails include live projects that require quick attention or urgent requests for help or information that directly impact your own workflow or productivity. Daily emails also include life-changing emails, such as a request from the media or an exciting business opportunity. “Inner circle emails” are messages from your friends or clients that give you energy, and these are also on the daily list. “We all need circles—and emails—like these,” Diaz-Ortiz writes.

“At face value, it seems like email is the biggest blow to productivity the world has ever seen. But first impressions can be deceiving.”

Handle daily emails in bulk and on the day they are received during one of your designated email periods. Be careful not to put all work projects into your daily list. “If a project is far off, in incubation stage, or on the back burner, it doesn’t require such vigilance in your life, or in your email inbox,” Diaz-Ortiz writes.