When I said legit newsletters, I meant the sort you get from sites you've already signed up for. Newsletters that arrive out of the blue are not legit and you should of course never interact with those, but that's self-evident for the reasons you stated, and the whole point of me mentioning legit newsletters specifically was to point out that these shouldn't go in your spam folder because they tend to look too similar to legitimate notification emails, and you only end up skewing the filter toward false positives.