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Introduction

Spam isn’t a filtering problem. It’s an economics problem, and email has never fixed it. Sending mail costs a spammer essentially nothing, so even a 1-in-12,500,000 response rate still nets about $7,000 USD/day at scale. Multiply that incentive across the internet and you get the numbers today: an estimated 362 billion emails sent daily, with 45-60% of it spam. No amount of machine-learning spam detection can win that fight permanently — filters treat the symptom, and the number of spam emails keeps climbing precisely because the incentive to send it was never touched.

The same free-to-send flaw now powers something worse than junk. The FBI’s 2025 Internet Crime Report counts business email compromise — the “our bank details have changed” message — at roughly $3 billion in reported losses in a single year, and phishing as the most-reported crime of all. And the filters are losing faster than they used to: security vendors now report that most phishing mail is written by AI, with click rates that match a human expert’s. A filter judges the content of a message, and content is exactly what a machine can now make indistinguishable from the real thing.

A price is different. Postage doesn’t care how well the message is written. That’s the whole idea behind SithBit: it charges the sender, not the recipient, and lets you set the price — content-blind, so there is nothing for a better forgery to get past. And it does so without asking you to abandon email itself: the reference servers speak standard SMTP, IMAP, and POP3 to the letter, so your existing mail client just works. See Standards and RFC coverage for exactly which RFCs each server implements.

Sender-pays postage

In the earliest days of U.S. postage, letters were paid for by the recipient, and the system was so inefficient it collapsed under its own volume. Email never got past that stage — you still bear the cost of your inbox, either directly through a subscription or indirectly through the ads and data-mining that fund “free” accounts. Stamps fixed postal mail over a century ago by putting the cost on the sender instead. SithBit does the same for email, and takes it a step further: instead of one central post office setting one universal price, every mailbox owner sets their own price, per sender if they want to.

That single change is what makes spam uneconomical rather than merely harder to get away with:

  • You price out spam, not guess at it. Every message to your mailbox costs the sender real SOL. A new mailbox starts at 1 SOL per message from anyone you haven’t priced yet — deliberately a wall, not a price list — and you lower it, per sender or for everyone, to whatever your attention is actually worth. Spam has to be profitable after your price, not just after a filter’s guess.
  • Strangers pay; friends don’t. Each correspondent gets their own prepaid postage balance for mail to you (a “frombox” — see Fromboxes). Allow-listing someone just means funding theirs yourself: the protocol waives its fee on that purchase, and the value round-trips back to you as their mail arrives, so recognizing someone you trust is free beyond ordinary transaction fees.
  • You only ever pay for mail you mean to send. As a sender, there’s no subscription and no ad-supported inbox trade-off — postage is the price of the message you chose to send, nothing more.

Get paid to be emailed

Postage from strangers doesn’t go to a provider. It goes to you.

  • You keep roughly 90 % of it. When a message settles, the postage lands in your wallet; the operator whose domain carried it takes a 10 % share by protocol default (see Economics for the exact split). You’re compensated for the inbox space you were already defending, instead of paying a provider or letting them monetize your data.
  • Advertisers pay you too — only if you ask them to. Publish a beacon naming topics you’ll hear about, and campaigns pay your postage to land in your inbox plus a bounty when you reply. You keep the postage whether or not you answer, and closing the beacon takes you out of the pool and returns its deposit.
  • You can see what your inbox made. sithbit earnings is the read-only snapshot of what your wallet holds and has taken in.

The sender’s side of the bargain is just as real. The big mailbox providers now reject bulk mail outright unless it clears an authentication and complaint-rate bar, and even fully compliant senders watch a share of legitimate mail land in spam. Delivery has become a reputation lottery, and a whole industry sells tickets to it.

A funded frombox is not a lottery. If the sender has postage for you, the message is delivered and recorded on-chain — there is no reputation score in the path to lose. Two things make that safe rather than a spammer’s dream:

  • Reputation lowers the price for the honest, not the wall for everyone. Under reputation-scaled first-contact pricing, a wallet that has paid and behaved pays less to reach someone new; a burner wallet pays your full default. An organization can go further and attest a verified sender — prove once, by DNS, who stands behind its wallet, and pay the floor price on first contact ever after.
  • Campaigns reach only people who opted in. An advertiser can quote the whole campaign before a lamport moves, and every recipient is a real, funded wallet — a bot farm costs real SOL to build.

No token

If you’ve been anywhere near crypto, you already know the pattern: a project launches its own token, and your upside depends on a team you don’t control — one that can pre-mine a chunk for themselves, unlock more supply later, or simply walk away with the liquidity. SithBit doesn’t ask you to take that bet. There is no SithBit token. Postage, stamps, and every payout described above move in native SOL — the same SOL you already hold to pay transaction fees on Solana for anything else. No mint anyone controls, no allocation for insiders to dump, nothing to “rug”: if you hold SOL, you already hold everything the protocol needs from you.

Note — only on Solana: pricing every message individually only works if the settlement layer can keep up. To support even a small fraction of global email traffic, an on-chain mail system needs to clear millions of transactions per second — throughput only the Solana blockchain provides today.

Your address is yours, and your mail is sealed

Fighting spam with filters costs you twice over. Your provider has to open and read every message to classify it, so you’re trusting a third party with your mail’s contents — and increasingly they do more than classify: regulators have fined the largest provider for advertising inside the inbox without consent.1 That provider usually also owns the domain your address lives on, so your identity on the internet is rented, not owned — and an automated “security hold” can take it away for days or months with no one to appeal to.

SithBit removes both dependencies:

  • Your address is your wallet. It’s not tied to a domain someone else controls, so nobody can revoke it out from under you. It’s not permanently tied to any one domain either — you can move it to a different domain at any time, keeping your wallet, mail history, and identity intact.
  • Your mail is sealed to your key. Message bodies are encrypted by the sender straight to your wallet and stored on the Interplanetary File System ( IPFS), so no central authority ever holds your mail in the clear — see IPFS storage: benefits to users. With Lockbox the seal is applied on your own device before a message leaves it, so even your operator only ever sees ciphertext. Taken together, two SithBit addresses can exchange mail using only the chain for settlement and IPFS for storage — bypassing the internet’s SMTP relay infrastructure entirely.
  • We tell you exactly what’s public. The envelope — who mailed whom, when, and for how much — lives on a public ledger and is permanent. That is a real trade-off, and What’s public and private spells it out rather than hiding it.

Anyone with a domain can run one

SithBit isn’t a single proprietary email service with one company behind it — it’s a protocol. Running the mail servers (sithbitd, the combined SMTP/IMAP/POP daemon — see Running a mail server) takes no special permission: authorize your own domain on-chain, point its MX record at your server, and you’re a first-class mail operator on the same footing as anyone else on the network.

Hosting isn’t charity, either — it’s the third profitable role in the system, alongside senders and recipients:

  • You earn a cut of every message you relay. For each mail settled on a mailbox under your domain, your operator wallet collects a share of that message’s postage — 10% by protocol default (see Economics for the exact split) — so the more mail your domain carries, the more it earns, turning what used to be a pure hosting cost into a revenue line that can offset it.
  • No permission needed — a DNS record and 0.01 SOL. Authorizing a domain costs 0.01 SOL paid on-chain once, verified against your domain’s DNS TXT record. No central provider decides who’s allowed to run a mail server.
  • Your outbound to other SithBit users never touches an IP blocklist. Self-hosting conventional mail has become effectively gated by IP reputation: a perfectly authenticated message from a rented server range is still refused on the address it came from. Mail between SithBit mailboxes settles on-chain and is stored on IPFS, with no IP reputation anywhere in the path; the domain’s on-chain authorization replaces the gatekeeper.
  • Names are assets, not rentals. A domain authorization and an alias never expire and carry no renewal fee; both can be transferred, listed, or auctioned on the name marketplace, and the seller keeps 90% of the proceeds.

Find your path

Everything above serves one of four kinds of reader. Start where you fit:

  1. The same report describes tracking pixels and the regulator’s proposal that tracking needs a consent of its own. SithBit’s answers — a reader that never fetches the pixel, an on-chain delivery record in place of an open receipt, a reply bounty in place of an engagement score, and a beacon as separate, revocable consent to advertising — are taken point by point in Tracking pixels, consent, and the paid inbox. ↩