SalesLoft - The simpliest way to build the most accurate and targeted lists of leads on the internet
Mailtrack.io - The best email tracking solution I've found. Free
Streak - Manage customers inside Gmail
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
Bananatag - Find out what happens to your emails after you press send! Add email tracking, attachment tracking, email scheduling and templates to your daily emails.