Boomerang's email tracking software notifies you both when a recipient opens your email and when they click on any link in the message. It uses powerful, cross-platform tracking that works even when users open your message on mobile!
For email tracking in Gmail, I use Boomerang! I've had really good results.
You're a Boomerang install away from having powerful email tracking software accessible from your Gmail compose window. Once installed, you can enable read receipts or click tracking for any email you write by clicking the small envelope button that will appear at the bottom right side of your compose window. Turning on email tracking will add a image at the bottom of your email to let your recipient know that you've requested a read receipt. Unlike many email tracking tools, Boomerang’s read receipts respect privacy, building trust with your recipients.
Shortly after your tracking-enabled email is opened, Boomerang will send you a notification to let you know. You can get even more information by accessing your Boomerang manage page, where you can quickly see details of each message you tracked: how many times it has been opened, the approximate time it was first opened and last opened, which of its links have been clicked, how many times each link was clicked, and the first time and most recent time each link was clicked!