Not the person you replied to, and it's impossible to know with certainty how often you're in someone else's spam, but very rarely.

I had an issue with yahoo a couple of years ago that's all. The "it read like there's a whole science" is sadly a trope mostly repeated by people who have never tried because it gets upvotes on Reedit.

There are some steps you have to take, but not many, and systems like Mox mailserver or stalwart guide you through it, and mail-tester will check if you got it right.

Email, other than tweaking spam filters, is one of my lowest maintenance systems. I can't remember the last time I touched Exim or Mox config