ReadNotify - ReadNotify enables the user to know when email is sent and the reciever reads the email.

EmailTracker.cc - Free Email Tracker for Gmail. Close More Deals with Comprehensive Email Tracking, Automated Follow-up Reminders, and Detailed Click Insights

Drip Drop Email - Reserve your spot today for the last email marketing and sales sequencing platform you will ever need. Track Views, create a Lead Magnets, clean an email list right.

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.

DidTheyReadIt - DidTheyReadIt e-mails that are sent will be invisibly tracked and the instant the recipient opens the message DidTheyReadIt automatically notifies the user.

Intelliverse Email Tracker - Intelliverse Email Tracker provides insights to increase the ​productivity of your emails.