PixelBlock - Block email open tracking inside of Gmail
Ugly Email for FireFox - Get back your email privacy, block email tracking
Email Privacy Protector - Check the presence of email ids on your webpages using Email Privacy Checker tool and protect yourself from email spammers.
Privacy Badger - Privacy Badger blocks spying ads and invisible trackers. How is Privacy Badger different from Disconnect, Adblock Plus, Ghostery, and other blocking extensions?
MailTrackerBlocker - Developer solving interesting problems with APIs. OSS contributor (Slim Framework, rst2pdf, OpenWhisk) & amateur photographer. He/him.
uBlock Origin - Popular and efficient blocker for Chromium, Chrome, Edge, Firefox, Opera, Safari, Thunderbird.