Earlier quoted context omitted.
It's quite the juxtaposition seeing your post right next to https://news.ycombinator.com/item?id=26163842
As someone with a daily email "newsletter" of my own [1], I am aware of (many of) the vagaries of spam filters. I use plain text only, though, so I couldn't use tracking pixels even if I wanted to. I do unsubscribe users if messages start bouncing but I have no way of knowing if they get silently dropped or spamfoldered. As someone who subscribes to lots of newsletters, the "interact or we will auto-unsubscribe you"…
IF you get spamfoldered by enough people the provider will just start sending to the spam folder for everyone. Your newsletter is now useless