But as a newsletter publisher they don't share that information with me. If I don't track it myself, eventually my engagement metrics will fall below a certain (undisclosed) level and everything goes to the spam folder.
That is surprising, and unfortunate. I believe this will ultimately have to change. The percentage of people blocking remote content will only go up. I block ALL remote content in my emails, and there is nothing that will convince me to stop doing that.
Can you imagine the comment threads if google was secretly sharing inbox engagement data with marketers?
Anyway, it's been like this for years and the overwhelming majority of email clients load images by default so everyone mostly works around it. I don't think it's changing any time soon.
All it would take is a single default configuration change by Apple, Microsoft, or Google. It is not crazy at all to think that Apple would change the default setting to block loading remote content.
They don't, but they also don't share that information with the sender. Gmail wants senders to be proactive and auto-unsubscribe disengaged recipients, which requires tracking open/click rates.