Receive real-time notification pop-ups when your emails are opened
Mailtrack is an email tracking extension for Gmail. When you sent a mail to anyone and you need to be sure that your mail have opened on time or not Mailtrack let you know if the emails you’ve sent have been read or not.
Single check means that the mail you have sent has delivered but not opened. Double Check means mail has delivered and opened by the recipient.
But if you sent mail to more than one person then free version of Mailtrack not provide notification for that mail, for that you have to take yearly subscription.