CEO of LinkedIn Jeff Weiner follows four clear cut rules when it comes to managing email mayhem.
The first is rule is to ramp up a routine. If email won't structure itself (and no, it never never never will) then structure your own email routine. Weiner's routine looks like this:
Wake between 5am and 5:30am; spend roughly an hour on my inbox; catch up on the day's news; have breakfast and play with the kids; workout; go to the office; carve out roughly two hours for buffers each workday; come home; put the girls to bed; have dinner with my wife; and then decompress, typically while watching tv (sporadically cleaning up my inbox via mobile during commercials and the boring parts of whatever we're watching.)
Since technology erodes structure, we need to create rituals to create structure--and productivity--in our days.
The second rule is to write with extreme clarity. "Vague emails beget clarifying follow-ups, further crowding your inbox." Put another way, the best shortcut is to not take one the first time around.
The third rule is to pay attention to the To: and the CC: fields. The former is inteded for whoever needs to respond. The latter is for context.
The fourth rule, according to Weiner, is to use "email to communicate highly nuanced, sensitive subjects that are bound to generate controversy if not a flat out aggressive response."
This echoes the advice old-school adman David Ogilvy gave regarding preventing communication stagnation in his self-same office:
Crusade against paper warfare. Encourage your people to air their disagreements face-to-face.
My only addition to Weiner's four rules: don't strive for the zero unread inbox. For many of us, its an unrealistic possibility. Striving for the zero unread inbox can often interfere with Weiner's first rule - creating rituals - if it means breaking dinner time to clean up your inbox. The value added from a pleasant meal (and thirty minutes without looking at a screen) is much more rejuvenating than the value added from a 13 unread count down from 14.