MIDSIG / POST OFFICE PAY WITH CARD
A LITTLE POSTAGE. A BETTER INBOX.

Good mail.
Small change.

A nickel of intention behind every message.
Pick up some stamps. Get back to saying something.

01 Buy a bundle02 Sign your mail03 Make it count

Price: 5¢ per message, per recipient. Card minimum $10.
Pay like a normal checkout. No wallet. No crypto.

YOUR NEXT HELLO STARTS HERE

Pick your postage.

Pay with a card. Send better mail.Sign in, enter your sending domain, pay $10 or $25. Stamps are added automatically.
1 Your stamp book

Pay with a debit or credit card. Minimum $10.

Pay with crypto instead
USDC

Native USDC settles directly on Base and is verified before postage is credited.

Paying green-lights this From domain. Example: aisp.live

200 stamps$10.00
Card processingHandled by Square
Due today$10.00
No wallet needed to try it

No signature. No payment. No surprise approvals.

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What does one stamp cover?

One authenticated message to one envelope recipient. A message to three recipients uses three stamps. The planned price is 0.05 USDC per stamp, with no bundle discount that weakens the minimum. The payment ledger and paid SMTP enforcement are still being built.

Why buy a book instead of one stamp?

One deposit can fund many messages, spreading transaction costs across your postage. Once implemented, the gateway will debit credits automatically when accepting a valid signed message. You won't need to approve a wallet transaction for every email.

Where do payments go?

MidSig keeps fiat and crypto settlement separate. Card payments are processed in dollars through Square. Native USDC payments settle directly on Base.

Base · Native USDC0x47cf60BdD877203264921D05CE26F81f6d36Aa3E

Direct wallet transfers are not postage purchases unless they are attached to a MidSig order. Card-payment receipts are hashed locally, batched into a Merkle commitment, and anchored to Base without publishing card details on-chain. Read the payment architecture →

LIVE · PROVEN ON BASE

Email postage with a cryptographic receipt.

MidSig is no longer a payment mockup. The production gateway signs the message, binds the actual SMTP recipients and message content, charges postage, and can independently anchor fiat-settlement receipts to Base.

Domain-bound identity

An Ed25519 MidSig key published by the sending domain proves which domain authorized the message instead of trusting the visible From line alone.

Content + recipient binding

MidSig v2 commits to the message body and SMTP-envelope recipients. Changing the content or replaying the signature toward another recipient breaks verification.

Paid SMTP admission

Valid postage is charged per recipient only after cryptographic verification. A valid signature without sufficient postage does not buy delivery.

Fiat receipts anchored on-chain

Successful card-payment receipts stay private server-side. Their hashes are combined into deterministic Merkle batches and committed to Base using a dedicated gas wallet.

Square USD → Postage credit → Receipt hash → Merkle root → Base → Confirmed
First production anchor proof Base · Chain ID 8453
0x48cc213a1843a174665a5f15307b17526427ef996602e023da4f67c7556bb2e8 ↗
0xeddfa8f0efeb953b91e167790fd67608fd593584aa5913a45fe6308ca89cd0c8
0x216c81f25b7f4970dec1aab4e441189e66d03fcc345b1a55edb0a1c10bee3eda
0x44471Ee17397Bb565CE11E6d37cb98D98Cce3E5F ↗

No identity. No stamp. No inbox.

OPTIONAL · WALLET CONNECTION

Bring your wallet.

Connection shares your public address with MidSig so a live Base payment order can be matched to the correct payer.

 LIVE POSTAGE CHECKOUT

One last look.

Review the postage order before creating a live payment request.

Sending domain
Stamp book
Payment route
Postage value
Network fees
Quoted by your wallet for Base transactions
Settlement
Verified before postage is credited

MidSig verifies domain ownership and settlement before postage becomes spendable.

 ORDER CREATED

Your postage order is ready.

Settle the order. MidSig verifies it. Your postage balance updates.

Postage is credited only after verified settlement.