Summarize what the company does in 1 short sentence as if you were a business analyst, removing all mentions to user volume / ratings / reviews, and removing all mentions to the company's team / founders / investors:

"Mailtrack is the #1 free email tracking and productivity tool for Gmail, with over 1.5 million active users on the Google Chrome Web Store, G Suite, iOS and Android. Thanks to its intuitive checkmarks (✓✓) for read receipts, Mailtrack allows its users to know if their emails have been opened, and how many times, either on desktop or mobile. The current 70,000 customers of Mailtrack Pro and Advanced also count with extra premium features, such as link tracking, full activity dashboard and Mailtrack Campaigns for group emailing. Mailtrack is among the best-reviewed solutions on the Chrome Web Store, with over 10,000 reviews and a 4.5 out of 5 evaluationn rate. For more information, visit mailtrack.io." Provide your response in exactly 5 paragraphs (separated nearby paragraphs with 3 aterisk symbols ***).
user