Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.
EmailTracker.cc - Free Email Tracker for Gmail. Close More Deals with Comprehensive Email Tracking, Automated Follow-up Reminders, and Detailed Click Insights
Mailbird - Mailbird is the best email client for Windows 7, 8 and 10
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
eM Client - eM Client is a fully-featured email client for Windows and macOS with a clean and easy-to-use interface. eM Client also offers features for calendars, tasks, contacts, notes, and chat.
MailTime - Go through your email as fast and easy as text-messaging