Do want to know when your emails in Gmail were read? MailTrack tells you when a user received and opened your email. After sending it, you’ll see a single check when your message is sent and a double-check whenever the recipient reads it. The service is free and only works with Gmail. You will continually get a pop-up asking to upgrade after each send which can get annoying. I have turned off the feature a few times because of the constant asking for upgrade. However it is nice to know that an individual got your email and read it.