The problem: Email spam exists because sending is free. Every filter, blocklist, and ML model is just an arms race against something that costs nothing to send.
The fix: What if reaching someone's inbox cost a tiny amount — say 100 sats (~$0.08)?
I built https://tanstaafl.email to test this:
- Unknown sender emails me
- Auto-reply with a Lightning invoice for 100 sats
- They pay → email delivered. They don't → dropped
- Sats go to the recipient, not a middleman
Why it works:
- Bots can't pay Lightning invoices — spam is dead on arrival
- Zero false positives — if someone pays, they meant to reach you
- Negligible cost for humans, devastating for spam at scale
- Works with any email client — the gate is on the receiving side
Stack: Cloudflare Workers catch inbound SMTP, hold the email, fire a Lightning invoice via LND, auto-release on payment confirmation.
Try it live: Send an email to mailto:niko@tanstaafl.email — you'll get an auto-reply with a real Lightning invoice. 100 sats to prove the concept.
What's the right price floor? We settled on 100 sats — reliable routing across 95%+ of the network, filters bots, barely registers for humans. Curious what SN thinks.
TANSTAAFL = There Ain't No Such Thing As A Free Lunch. Your inbox shouldn't be free real estate.