There should be an unsubscribe email header for newsletters. Then it could even be a feature for mail clients.
It is unfortunately not implemented by most email clients.
AFAIK, Gmail does as well.
Better email clients know to use the header, and e.g. gmail even asks about properly unsubscribing when marking a newsletter with that header as spam iirc.
Spam companies often use this to check if the email address they've targeted is real because they get callbacks from legitimate users. I've only seen one or two legitimate uses of the header as far as I can remember.
As if gmail ui wasn’t already obscure af. They could make “don’t want this anymore” button that uses unsubscribe header first and if it doesn’t work, mark it as spam automatically. Many shady practices would disappear at that same moment, but who cares when making six figures a year.
If only email could work as a modern instant messenger - no spam, reacting to explicit and well-defined user intents, allowing file transfer without limitations that render that function useless, and delivering messages in less than a second.