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

Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.

mlist - Email newsletters, outside of the inbox

tawk.to - tawk.to is a free live chat app that lets you monitor and chat with visitors on your website or from a free customizable page

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

JivoChat - JivoChat is a live chat that enables you to talk to visitors on your website