DuckDuckGo is rolling out an email privacy feature that strips incoming messages of hidden trackers that can help profile you for better profiling and ad targeting. Users of the service get a free @duck.com email address that cleans messages of trackers and forwards them to your normal inbox. Trackers can let email senders know when you open their messages and help ad companies create a profile for you based on collected metadata such as device you used to read the email when you opened the message, and your general location.
Source: https://www.bleepingcomputer.com/news/security/duckduckgos-new-email-privacy-service-forwards-tracker-free-messages/