Verified-sender attestation

Every message a wallet sends is signed, but a signature only proves which wallet sent it — not who stands behind the wallet. For an organization that sends mail at any scale (receipts, notifications, a newsletter), that gap is a credibility problem: nothing on chain connects its sending wallet to the name its recipients actually recognize — and the same gap is what invoice fraud and lookalike-sender phishing live in, where a message that reads like the real company asks for a payment to go somewhere new. A verified-sender attestation closes the gap. It is an on-chain record in which a DNS domain vouches for a wallet address as a legitimate sender — “acme.com stands behind this wallet” — and anyone, MX operator or mail client alike, can look the binding up and verify it.

The vouching works the same way authorizing a domain by proof does: whoever controls the domain’s DNS generates a cryptographic proof of that control, and the chain checks the proof itself, on the spot — no administrator signs anything, and no delegate is in the loop. The organization proves domain control once, pays a one-time fee, and the attestation stands until revoked. The cost sits entirely on the sender’s side, matching the protocol’s positioning everywhere else: senders pay to be credible, recipients never pay anything. For a legitimate organization the payoff is delivery on its own terms — prove you’re you once, and pay the floor price on first contact under reputation-scaled pricing instead of a stranger’s full default, with no mailbox provider’s reputation score standing between you and the inbox.

An attestation is deliberately less than domain authorization, and independent of it. It confers no serving rights: an attested wallet gains no ability to route, inject, or operate mail for the domain, and the domain itself gains no standing as a mail suffix. It is a freestanding record — a domain that has never been registered as a SithBit mail domain at all can still attest its sending wallets, because attesting requires only proven DNS control, not an on-chain domain account. And it is not exclusive: a domain may attest any number of wallets, one record per (domain, wallet) pair, each independently revocable.

The fee is a flat, one-time charge to the postoffice — 0.01 SOL by default, tunable by the delegate up to a hard on-chain cap of 0.1 SOL (see the tunable-constants table). A proof that fails to verify charges nothing.

Revocation belongs to the attested wallet itself: it can close its own attestation at any time and reclaim the record’s rent. No other key — not even the domain’s — can reach the record, because its on-chain address derives from the attested wallet.

Since v0.39.0 an attestation also buys a concrete economic advantage: reputation-scaled first-contact pricing prices an attested sender’s first contact with any stranger at the discount floor immediately — the cheapest rate any reputation earns — instead of the mailbox’s full default postage. Proven domain control substitutes for a long postage spending record; a recipient-set price is never affected.

The binding is otherwise consumed from the terminal and by servers: the read-only sithbit domain attestation lookup and the gateway’s GetSenderAttestation call answer “is this wallet attested for this domain, and since when”. A verified-sender badge in the mail clients is planned but has not shipped yet.

For the commands — attesting, looking a record up, revoking, and tuning the fee — see Attest a verified sender.