iTrackMail - Email Tracking

iTrackMail is a Chrome extension that tells you when your emails are opened. Just write your message as you normally would, add a subject, and send—iTrackMail will notify you via push when the recipient views your email. It also records the date and time of receipt and estimates the recipient’s country, region, platform, and browser, helping you see if more than one person has read your message.

The tool is free to use. Note that not every email client supports this method; in some cases, recipients may need to 'display images' for tracking to work. For more details, review the Terms of Use.