Doubletick is a Free and Unlimited email tracking tool for Gmail and G-Suite, adds double checkmarks ✔✔ to your mail if it is read by the recipient (Just like WhatsApp) and notifies you with real-time notification.
A Mailgun email tracking and analytics platform for bloggers, developers and creators. Monitor your member email engagement without modifications to your application or website. Mail Flagger integrates directly with Mailgun via API.