The Problem: E-mail takes too long to respond to, resulting in continuous inbox overflow for those who receive a lot of it.
The Solution: Treat all email responses like SMS text messages, using a set number of letters per response. Since it's too hard to count letters, we count sentences instead. five.sentenc.es is a personal policy that all email responses regardless of recipient or subject will be five sentences or less. It's that simple. (See also: two.sentenc.es, three.sentenc.es, and four.sentenc.es).