MailTrack.io shows you when someone has read your message — even in group emails
MailTrack.io is a Chrome extension that lets you know both when your email was sent (with one check mark), and when it was opened (with two check marks). Not only that, but MailTrack.io can tell you when someone has read your email even if the email itself was sent to multiple recipients. And for those who want real-time notifications, MailTrack.io has an option to have pop-up desktop alerts when someone opens one of your emails.
Get it here.
Does it really work? Did I made a mistake??