E(asy) Mail
It drives me nutso when people complain about how many emails they receive and how their inbox is out of control. First, it’s a not-so subtle way of implying that you’re important. Second, it’s actually not that hard of a problem to rectify.
With a good system and a little bit of discipline you should never have to spend too much time digging though emails- even after a week or two of vacation from email.