I'm particularly fond of the senders who know there are nominally laws about spam, so they just label every piece of marketing and customer retention garbage as pertaining to your user account, or they layer some subscription-related language over a promotion al email. I uploaded photos to a printing service over a decade ago and long since unsubscribed from their marketing lists. Two months ago they started sending me bi-weekly "reminders" that my old photos would be purged soon but offering me a discount subscription to their cloud storage. They then sent me at least three weekly reminders. The thing is, none of the links in the email would send me to the page to download old information (which it turns out I had already done years ago, presumably on prompt of some other spam) or information on deleting that content myself.

The other classic of the genre is mailing list software that stores opt-out preferences separate of customer account data such that when they move to a different marketing service or their retention policy tolls out you start getting spam again, exactly 5 years after you opted out.