Amazon SES — $0.10 per 1000 emails.
SES also monitors these signals, and if it detects signs of abuse, such as elevated bounces or spam complaints, then a sender's ability to send may be paused and the account's activity may be reviewed. FAQ on these processes [2]. Some of the tolerates are quite tight, and can result in action being taken even if much less than a percent of messages are getting these sorts of responses. There's a lot more that I can't describe in a short comment.
SES processes and reacts to spam reports sent in standard formats like the Abuse Reporting Format (ARF), and looks at signals like List-Unsubscribe and bounces, etc. But this does require the system to understand the format of the reports used by the feedback loops [3]. Do you happen to know if your feedback loop sent spam complaints in ARF format? If you'd like to discuss further, feel free to reach out to me directly.
[1] https://aws.amazon.com/blogs/messaging-and-targeting/announc...
[2] https://docs.aws.amazon.com/ses/latest/DeveloperGuide/e-faq....
[3] https://aws.amazon.com/blogs/messaging-and-targeting/email-d...
I think you've confirmed what I said in my parent comment...SES doesn't take a zero tolerance approach.
I think it is the shared IPs that I've blocked (54.240.27.189/24). You'll see they are on multiple blacklists.
If you really distrust mail from those IPs so much, why not just filter it straight to SPAM? At least you'd be delivering it and your users could whitelist senders (or domains) they trust.
For example, if you want a quota of 100 messages per day, you have to pay a one time fee of $.10 per message to get into the pool, so $10. If you want a quota of 50k messages per day you have to pay a one time fee of $.005 per message, so $250.
My good friend has worked on the email system for a mid-range consumer ISP for about the past 10 or so years. He told me 93% of all email they receive is spam. And they have a 60PB NAS for their mail store. So for every 1PB of storage they had to discard ~14PB of junk. And that’s just the stuff they summarily dismiss. Then some of the remaining 7% they accept makes it to your Junk folder.