SlateMail is an experimental email client. It runs on Node using nw.js. I wrote about the project on Slate.com. Under the hood, it's cobbled together using various Node modules, including node-imap, mailparser, and nodemailer. Over the hood, it's cobbled together using features from various email clients, including Apple Mail, Gmail, Mail Pilot, and Dropbox's Mailbox.

Currently, SlateMail is not in active development. It's not nearly stable enough for me to even suggest that you try to install it. If you are interested in the idea of an extensible Web client based on Web technology, check out Nylas N1.