Enough of us doing this and I guess they'll get the message.
The reality here is that the free market rewards this awful behavior, so it won't be solved until regulation is applied.
From the sending side, I have one business right now where our outgoing emails are apparently being blocked or even silently dropped by at least three ISPs spread across two different continents. We have never sent anything even remotely spammy in our entire trading history. We have all the usual shouldn't-be-needed-but-are extras like SPF properly configured. The sending mail server hasn't found its way onto any of the big blacklists as far as we can tell. And the mails being blocked are actually quite important things like password reset requests, emails with copies of documentation that we are legally required to send attached, or even replies to customers contacting us to ask where their password reset emails are when they've been requesting them!
From the receiving side, I'm fed up with helping friends and family who are trying to work out why they aren't getting important messages, and with the ISPs who have screwed up their mail configuration or deliberately set up overly aggressive anti-spam policies but then have front-line support drones who just intone that you should check your junk mail folder as an instinctive reaction to any complaint about missing mail.
I think that with email now effectively being both the effective root password to so many online accounts and the primary means of communication between a lot of people and organisations with genuine reasons to contact them, the medium of email needs the same kinds of legal safeguards that other essential means of communications like postal mail have enjoyed for a long time. I don't think it should be left to big name mail services or some random ISP to decide whether or not their users are going to receive legitimate emails any more. Blocking false positives is far more damaging than missing false negatives when it comes to spam, and the situation is out of control. It's time to regulate.
They push the responsibility of getting rid of unwanted stuff in our mailboxes to us. It's not a single company doing this, but most of them. That's sometimes dozens of emails a week! We shouldn't waste our time reading, parsing and fighting the unsubscribe forms - many times fortified with cookie-consent walls!
The average internet user will not do that anyway, so the spammers rely on user's laziness and dulled senses, just like ad blindness, so they slowly start to accept this sick situation as the new normal. For us it becomes the new normal. For our children - the only normal.
In apple mail, even if you turn it off it will happily load the remote images if you try to forward the email.
I found this particularly troublesome when I wanted to forward a phishing attempt to IT, and Little Snitch showed mail trying to connect to the phishing site.
(this was not on catalina, maybe it is fixed?)
1. Spam from people who are just brute-forcing the space of possible email addresses. In this case, yes, clicking unsubscribe gives them information. But I will say, this spam is generally pretty well taken care of by existing spam filters, so personally I'm not concerned about this.
2. Spam from people who got your email address via some interaction. Maybe you bought something from them, for example. This sort of spam, they already have your email address and know it works. The upside here is that if you've made a purchase from them, it's much harder for them to avoid regulation due to the money trail, so if you unsubscribe, they have to actually unsubscribe you. There are loopholes in regulation, however.
How strong is the assumption that all users have only one email address and will keep that address long-term? I remember hearing that one could keep getting AWS free trials simply by signing up with a new email address.