Yahoo is constantly scanning users' emails, and then selling the data to advertisers. Yahoo reportedly only scans promotional emails from retailers. Yahoo says email is an expensive system, so people can't expect to use the service for free without the company getting anything out of it. But even emails in the premium tier, which users pay $3,49 per month, are subject to analytics unless they opt out. So if you use Yahoo Mail and want to opt out of analytics, you'll need to go to Ad Interest Manager and log out here. You won't find that option in Settings.
