Spark Mail - Spark helps you take your inbox under control. Instantly see what’s important and quickly clean up the rest. Spark for Teams allows you to create, discuss, and share email with your colleagues

Amium - A collaboration app that brings conversation to your files

mlist - Email newsletters, outside of the inbox

Dropbox Paper - A collaborative document-editing service

TL;DR Email - Send short emails & read emails as fast as you read Facebook

Dropbox Paper Mobile - Organize your team’s knowledge in a single place