Mailbird - Mailbird is the best email client for Windows 7, 8 and 10
Polymail - Native email app for email productivity.
GrexIt - Manage Tasks, Customer Support and Sales right from your Gmail inbox. Turn your Gmail into a powerful collaboration tool.
Airmail - Airmail is a lightweight and lightning fast mail client for Mac.
New Gmail - The new version of Gmail web
Morning Mail - A new way to manage your mail. Tinder for email.