[mrWiz]

I've started using this approach to combat spam that ignores unsubscribe attempts:

1. Report each and every offending email to the FTC: https://reportfraud.ftc.gov/#/

2. Forward the "report received" email that the FTC sends you to support@spamming_domain.com and explain how and why you're reporting them

3. That's it. I've had a 100% success rate with this approach