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
Birdly - Birdly is an expense management and expense report solution for SMBs.
Polymail - Native email app for email productivity.
PushMarket - Automate personalized emails for ecommerce (YC15)
Clean Email - Clean Email is an online service that empowers you to take control of your mailbox.
Dynamic Campaigns by Sigstr - Share the most relevant content in every email