> Likely they mostly have unsubscribe links; after a quick scroll down the list, I think it's nearly all from companies that I do have or had an existing relationship with.

At one point I decided to actually hit the unsubscribe links rather than just archiving these emails. Turns out I was subscribed to nearly 200 different mailing lists. But there were only 1 or 2 that wouldn't let me unsubscribe.