What we need is a better way to communicate. Where text messages and tweets encourage short, rapid-fire conversations, emails tend to be lengthier--and therein lies the problem. We put off responding because emails inherently require more time; even when a simple answer is all that's needed, we tend to labor over what we write.
Dart (Mac App Store link) tackles this problem head-on. With a refreshingly inventive concept that forces you to dramatically rethink how you approach your messages, Dart isn't so much about attaining Inbox zero as it is about using email in a quicker, more efficient manner. It won't replace your email client of choice or even notify you of every new message that arrives, but it will help you turn those rambling screeds into short, concise dispatches practically guaranteed to get a timely response.
Essentially, Dart offers a simple way to ask questions over email; when you compose one, you'll need to pose a question and offer a set of multiple-choice options that your recipient can select from. As it sends them, the app formats your query into clickable boxes that will in turn compose a message with the selected answer, ready to send from your default email client. Alternatively, you can use Dart to send regular messages, too, but the app imposes a Twitter-like 200-character limit to force brevity.
In each of its three forms--apps formatted for the iPhone, Mac menu bar, and Apple Watch--Dart is an extremely lightweight utility. There's no archive of sent messages or inbox of received ones; instead, as soon as you act on a Dart it disappears from the app (though it will stay in your regular inbox until deleted). But while the ephemeral simplicity is certainly refreshing when it comes to email, Dart needs a bit more refinement--and a whole lot more exposure--if it ever intends to catch on.
Unfortunately, Dart's greatest strength is also its biggest obstacle. As a menu bar utility, it takes a conscious effort to remember to use it, much more so than if it were a Mail plug-in or a standalone client. And when a message comes back, the starkness of it can be somewhat perplexing; for example, if you ask someone where they want to eat and supply a set of restaurant choices, the automatically-generated reply will simply contain the name of the restaurant. It would be better if Dart repeated the question in the return email or maybe resent the whole original email with the response highlighted in green.
The concept seems best-suited for Apple Watch, where seconds-long interactions are preferable, but I experienced issues with receiving them through the app. Notification alerts were spotty, and the app often failed to show any waiting Darts inside the app. But when it worked, it was fantastic, letting me respond to emails as quickly as if they were iMessages.