From Huffington Post:

A new app called Crystal calls itself “the biggest improvement to email since spell-check.” Its goal is to help you write emails with empathy. How? By analyzing people’s personalities.

Crystal, which launched on Wednesday, exists in the form of a website and a Chrome extension, which integrates the service with your Gmail…

With the personality profile, you’ll see advice on how to speak to the person, email them, work with them and sell to them. You’ll even be told what comes naturally to them and what does not…

Here’s a screenshot: