The most persistent emails I’ve gotten are from being Mormon at some point in my life, and familysearch.com has some special Mormons only mailing list that you’ll get re added to no matter how many times you unsubscribe. It’s kind of hilarious in a way to speculate why (Mormon church actually has a pretty good IT team in my experience, my guess is some automated system syncs over emails from Mormon church roles to the familysearch website which I think is owned by the church) but also irritating. I finally had to mark it as spam.