Last summer I read Getting Things Done by David Allen. I was a ways into the book and was struggling to find much value in what I was reading. I was about to give up on the book when I suddenly encountered the idea of batching emails. What I read over the next several chapters has completely changed my approach and - more importantly - my efficiency when it comes to returning emails.
Allen suggests you have set times throughout the when you "batch" or answer many emails at once as opposed to intermittently throughout the day (this concept is also discussed in Tim Ferriss's The 4-Hour Workweek). When batching your emails you must immediately do one of the following with each email:
If it is trash, place it in "Trash"
If it is simply information for your reference, place it in a "Reference" folder
If it takes less than two minutes, do it right away
If it takes more than two minutes you have three options: 1) Delegate it, 2) Place it on your calendar, or 3) Place it in a "Next Actions" folder
Once your inbox is empty, you can then focus on your "Next Action" folder and take care of those emails. Completed "Next Action" emails can be moved to your "Reference" folder (if you have taken care of the email) or the "Waiting On Others" folder (if you are waiting to hear back from others). Once you have worked through every email in your "Next Action" folder you are done and you can return to your important work!
What is described above might initially sound complicated, but once you get the system down your email efficiency will increase dramatically! You will also discover your mind feels less "cluttered" because when you have a proven method for returning emails. Give it a try yourself - you won't be disappointed!