It's definitely a gray area. What if twitter sent you mails for each following account and you can't unsubscribe from them all? Or Amazon sent promos for different sellers and you can't unsubscribe from them all?
Anyway there's other stuff. Via CAN SPAM laws, companies cannot pre-check subscription boxes (Substack does this in onboarding as well as when you subscribe via browsing their site). [0][1]
Also their consent gathering is not up to par. The regulations "require that a request for consent must contain a statement indicating that the person whose consent is sought can withdraw their consent."
Last, there may be something about how Substack bundles subscribing to publication on their dashboard into emails. To me this isn't unlike how following on twitter can't automatically subscribe to newsletter emails. There's specific callouts in CAN SPAM about such bundling. Ie you can't bundle accepting terms of service with receiving emails.
The main difference between Substack and your examples, is that on Substack the email IS the content.
You’re not receiving a notifications for content to be consumed on Twitter or on Amazon.
As for the other things you mentioned, those are more legal things I know absolutely nothing about and so I won’t comment on them because I honestly don’t have anything to contribute.
What you’re saying is more true of something like mailchimp or sendgrid. Since substack hosts the blog post on their site (with recommendations and everything) to me it’s more akin to a FB/twitter situation requiring separate consent vs follow.
Anyway there's other stuff. Via CAN SPAM laws, companies cannot pre-check subscription boxes (Substack does this in onboarding as well as when you subscribe via browsing their site). [0][1]
Also their consent gathering is not up to par. The regulations "require that a request for consent must contain a statement indicating that the person whose consent is sought can withdraw their consent."
Last, there may be something about how Substack bundles subscribing to publication on their dashboard into emails. To me this isn't unlike how following on twitter can't automatically subscribe to newsletter emails. There's specific callouts in CAN SPAM about such bundling. Ie you can't bundle accepting terms of service with receiving emails.
[0]: https://crtc.gc.ca/eng/archive/2012/2012-549.htm
[1]: https://i.imgur.com/8tmDRGI.png
[2]: https://crtc.gc.ca/eng/archive/2012/2012-548.htm