Ugly Email claims to block tracking pixels from 58 domains. The Firefox addon was last updated in 2020, and the Github in 2022. Source: 12 months ago

There have been some attempts by Google to restrict the amount of information that can be transmitted this way. For example,since 2013, Google has served all images in Gmail through its own proxy servers, which could hide your location from at least some tracking applications. And extensions such as Ugly Email and Pixel Block have been developed to block trackers on Chrome and Firefox. Source: over 2 years ago

Implementing something like ugly email would be ideal, not just blocking remote content from auto loading. Source: almost 3 years ago

Disabling automatic image loading in your mail client settings or using extensions like Ugly Email can help preventing this. Source: about 3 years ago

I'll update this if I find more. For now, this seems to be a partial solution. It's a Gmail add on (except I don't use Gmail) that adds reminders. The options when setting reminders include cancelling it if someone replies, and to remind everyone in the thread. If you combine those two, it seems like — if you use Gmail's web client and have $23/month you're dying to get rid of — a decent way to add the feature. Source: over 1 year ago