There is a Swedish company (non profit? Activist group? IDK) called SpamHause. They partner with ISPs to help block spam. Their process is something along the lines of:

1) Inject fake email addresses into lists of email addresses that are bought/sold WITHOUT user consent

2) Wait until someone UNAUTHORIZED emails them spam

3) Tell the ISPs (and anyone else who will listen) to STOP processing emails from the companies that sent them spam.

4) The ISPs block the companies because SpamHause is reputable and REALLY good at finding spam, also the ISPs save money by "not having to process the spam

We accidentally got a hold of a bad batch of email addresses several years ago and we spent MONTHS trying to fishout and overhaul our email authorization process. It cost us $10s of millions.

Also, WHY were we sending that spam?!?

You serve a variety of email domains that validate as deliverable, then you accept emails and report the sender, which hurts their deliverability.

> If enough people do this the cost of those bouncing emails would become prohibitive.

This idea got a ton of attention in early days tech that led to what's known as proof of work: see bitcoin. The primitives of btc show up in a lot of interesting areas.