Privacy Badger - Privacy Badger blocks spying ads and invisible trackers. How is Privacy Badger different from Disconnect, Adblock Plus, Ghostery, and other blocking extensions?
PixelBlock - Block email open tracking inside of Gmail
Ghostery - Privacy tool for transparency and control
Ugly Email for FireFox - Get back your email privacy, block email tracking
DuckDuckGo Privacy App & Extension - Privacy, simplified. Available on all major platforms.
Email Privacy Protector - Check the presence of email ids on your webpages using Email Privacy Checker tool and protect yourself from email spammers.