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.
Hunter - Find all the email addresses related to a domain
GetNotify - GetNotify is a free email tracking software solution.
Snov.io - Sales engagement on autopilot.
Mailtrack.io - The best email tracking solution I've found. Free
Apollo.io - Apollo’s predictive prospecting, sales engagement, and actionable analytics help the teams to reach its full revenue potential.