Wow, this brings back memories. Way back in the 2000 I worked on a concept to charge “postage“ to big senders and remit payments to receivers (hosts, not end users). I also looked at hashcash. I ultimately abandoned the project because I realized I would be spending all my time convincing big senders why they should pay and I knew I would hate that job.

Previously I was the spam cop for a big sender and saw up close all the ways our clients would try to weasel around it.