Signals by Hubspot. The best!

[Mai72]

I love signals by hubspot! It's a Chrome plugin that gives you a notice whenever the person who received your email opens it. It gives you an immediate notification, time and location. Also, it will tell you how many times that person has opened your email.

I hate it when I send emails out to people/corporations and I don't get a response. Now I at least know that they received my email.