Mixmax - At Mixmax, our mission is to change how the world communicates. We’re an email productivity platform that helps sales, customer success, and recruiting teams do their jobs better.
ReadNotify - ReadNotify enables the user to know when email is sent and the reciever reads the email.
Yesware - Sell smarter with email tracking and more
GetNotify - GetNotify is a free email tracking software solution.
Intelliverse Email Tracker - Intelliverse Email Tracker provides insights to increase the productivity of your emails.
Mailtrack.io - The best email tracking solution I've found. Free