Keep in mind that some users almost certainly believe your email is spam. Even if they're explicitly paying you to send them that email.
For an end user "spam" is "email I don't want".
"But" I hear you screaming, "That's their credit card bill, they even confirmed their email address and specifically opted into receiving it by email - that's not spam". It's unwanted, they don't have $850 to pay off the balance and they don't want to think about the interest charges, so it's spam as far as the user is concerned, some non-trivial fraction of users will click "Spam".
You've probably seen people who have piles of unopened real world postal mail, they feel the same way about that. Unsolicited catalogue. Bank statement showing I am overdrawn. Nagging letter from my mother. All unwanted: Spam.
Worse, some of these same users will anyway be angry that the important message they marked as spam is treated as spam. Why are facts true? They shouldn't be true if I don't want them to be. Is that irrational? Sure, that's humans for you.
This is a losing proposition, and the end-user facing providers are aware of that, but "spam blocking" is something users demand from such providers even while being very angry that it doesn't do what they want. "Humans are irrational" is not actionable.
last time I checked (been a few years since I used Google) BigTech is perfectly able to distinguish a bad actor from an opt-in type of service. They even presented me with a little notification whenever I moved stuff into SPAM that didn't belong there asking "do you want Gmail to unsubscribe you from X" ... I can't exactly recall the text - but all their lofty claims about their "AI" should account for something?
I agree with you that the _user_ is the biggest wildcard. But it's not that we should allow Google/Microsoft get way with this as an excuse. They are currently right in the middle of killing open protocols like imap in favor of their own flavored shit (probably something AMP like but for email). They do not deserve the benefit of a doubt. They do not even deserve to have their side of the argument heard at this stage.
GMail prompting you to unsubscribe is because the email carries a standard [1] header (List-Unsubscribe) and GMail detects it. They may also be using some smarts to detect unsubscribable emails that don't have the header, but in general it's because of the header. It doesn't have anything to do with distinguishing between spam and legitimate subscriptions.
So if you mark a legitimate subscription as spam and don't unsubscribe when gmail prompts you to, it's likely that it'll get sent to your spam in the future, and perhaps contribute to the sender's spam score which affects other people's inboxes too.
[1]: de-facto standard? I can't find any RFC for it.
actually I wasn't talking about mailing lists (I'd never move something from majordomo or similar to spam since I 100% know why I received them). But I'm talking about corporate news letters delivered by services like MailChimp and other marketing tech. - No idea if these have a List-Unsubscribe header - but even if they do I shouldn't have received the message in the first place (in most cases).
For an end user "spam" is "email I don't want".
"But" I hear you screaming, "That's their credit card bill, they even confirmed their email address and specifically opted into receiving it by email - that's not spam". It's unwanted, they don't have $850 to pay off the balance and they don't want to think about the interest charges, so it's spam as far as the user is concerned, some non-trivial fraction of users will click "Spam".
You've probably seen people who have piles of unopened real world postal mail, they feel the same way about that. Unsolicited catalogue. Bank statement showing I am overdrawn. Nagging letter from my mother. All unwanted: Spam.
Worse, some of these same users will anyway be angry that the important message they marked as spam is treated as spam. Why are facts true? They shouldn't be true if I don't want them to be. Is that irrational? Sure, that's humans for you.
This is a losing proposition, and the end-user facing providers are aware of that, but "spam blocking" is something users demand from such providers even while being very angry that it doesn't do what they want. "Humans are irrational" is not actionable.