Free Gmail tracking with geolocation. With GeoTrack, track if your emails were read, clicked, recipient's geolocation, device used and much more...
Mailtrack.io - The best email tracking solution I've found. Free
Yesware - Sell smarter with email tracking and more
iTrackmail - Want to know if people are reading the emails you send?
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.
Intelliverse Email Tracker - Intelliverse Email Tracker provides insights to increase the productivity of your emails.
SalesLoft - The simpliest way to build the most accurate and targeted lists of leads on the internet