Shift - Shift is the ultimate email client for managing Mail, Calendar, Drive, Slack, Asana, Jira, Evernote, and all your other favourite apps
Facebook Messenger Kids - Safer and More Fun Video Calls and Messaging
Mia for Gmail - A desktop email client for your Mac, without a browser !
Stack App - Stack is a Tweetdeck for your social apps
Mailplane - Mailplane is the best way to use Gmail on your Mac. Use an unlimited number of accounts, get new mail notifications, use plug-ins and much much more.
Caprine - Elegant Facebook Messenger desktop app