Polymail - Native email app for email productivity.

Nylas Mail - The Nylas Cloud API powers your application with email, calendar & contacts features. Built-in features for better email, calendar, and contact management.

Morning Mail - A new way to manage your mail. Tinder for email.

Hiver - Manage Customer Support, Sales and Projects right from your Gmail inbox. Collaborate with Shared Labels, Shared Contacts, email notes, email reminders and email templates

Airmail - Airmail is a lightweight and lightning fast mail client for Mac.

Clean Email - Clean Email is an online service that empowers you to take control of your mailbox.