The key difference in our implementation is using Lightning micropayments instead of on-chain Bitcoin. A 100 sat payment (~$0.08) clears in under a second, costs almost nothing in fees, and the receiver actually keeps the money. It's not burned like hashcash PoW — it's a real economic transfer.

If you want to try it live: send any email to niko@tanstaafl.email. You'll get a payment link back, pay 100 sats, and watch the email land. The whole flow takes about 30 seconds.

Would genuinely love feedback from someone who's been thinking about this problem.

Though I don't quite remember if it was your comment exactly or if it was someone's elses comment which had the same idea as this.

TANSTAAFL flips this: the sender pays real money (Lightning sats), the receiver actually gets paid, and trusted contacts bypass the gate entirely. It's not proof-of-work, it's proof-of-value.

The other difference: hashcash couldn't scale with the sender's intent. A recruiter reaching out about a 00k job and a Nigerian prince both burned the same CPU cycles. With economic pricing, the gate amount signals how much the sender values reaching you.

The gate doesn't exist to let spammers pay to reach you. It exists to filter signal from noise. Spammers won't pay even $0.08 per message because their whole model depends on sending millions for free. A recruiter with a real $200k offer? They'll happily pay a few cents to prove they're not a bot.

And anyone you already trust (contacts, colleagues, existing correspondents) bypasses the gate entirely — zero friction for people you know.

With a pay-to-inbox gate, reputation doesn't matter. The payment IS the reputation signal. A self-hosted mail server with TANSTAAFL works just as well as Gmail because the economic proof replaces the reputation system entirely.

We're actually running on Cloudflare Email Routing + our own backend right now, so we know the pain firsthand.

You don't need to buy into the "Bitcoin will replace the U.S. dollar" narrative to buy $5 worth of bitcoin to send a few hundreds or thousands of emails..

No one goes to an arcade wanting to play a game and says "I don't know about these tokens, though..."

You buy bitcoin somewhere (if you can't figure this out yourself you arent trying)

And send it to whatever address this app provides to you..

I am unsure whether you could use e.g. Apple Pay to pay directly, or if you’d have to follow the microtransaction playbook to buy a greater amount of currency which you can spend.

Maybe a 3 to 4 tier inbox. Known and trusted user being able to contact you without paying, a high value inbox for the $1+ range, a low value inbox for the $.2 range emails wont be auto-deleted in and a very low value inbox emails will be deleted in depending on the amount paid, with free mails being gone within e.g. an hour, all the way up to e.g. a month for $.19 mails.

Then unify those inboxes and set up notifications to the users' likings.

Also, I'd normalize e.g. 10% going to the e-mail service providers and enshrine that amount into the protocol right away. Otherwise the protocol wont get a lot of attention from the major providers and if it does, the provider taking his share is going to become normalized anyway. But then the split isn't going to be in favor for the users. Which isn't negative per-se, but it'd be nice to have at least one type of service where this is split is reversed. And it is fair to assume whoever takes the larger split has more influence on the prices, potentially either making this feature useless or pricing very casual users out of the service.

It also adds to the adagium that all spam solutions ultimately do not work, and Bill Gates proposed all of them (a meme, too).

Furthermore, email is a broken protocol not because of federation (something alternatives usually lack) but because of lack of E2EE.

For legitimate senders, the attached fee would end up being spent by the receiver to send a reply, like a "refund", so it ends up zero-sum.

But for spammers it becomes an expensive option. Nobody is going to reply to the spam to "refund" their fee.