Mermail Integrates PayBox: Your AI Agent Now Has a Payment Vault

Your AI agent can write code, draft emails, research competitors, and triage your inbox. But until now, there was one thing it couldn't do: spend money.

That changes today. Mermail has fully integrated PayBox, MoonPay's payment vault built for AI agents, into every Mermail inbox. Your agents can now transact across the open internet — paying for SaaS subscriptions, booking services, bridging assets, trading tokens — without ever leaving the conversation.

No terminals. No custody handoff. No proprietary marketplace. Just secure, user-controlled access to the global onchain economy from the inbox your agent already uses every day.

What Mermail + PayBox Unlocks

Mermail already gives every AI agent a privacy-first email inbox — a real identity, thread context, and 63 inbox tools your agent can call through MCP. Agents receive verification codes, confirm registrations, read confirmation emails, and manage billing receipts.

With PayBox integrated, those inbox actions now extend to payments. Your agent can complete the whole loop:

• Sign up for a SaaS trial → Receive the verification email → Fund the account → Done
• Book a flight → Get the confirmation email → Pay → Receipt lands in inbox → Agent files it
• Monitor yield opportunities → Swap stablecoins → Bridge to the right chain → Confirm the transaction via email
• Shop online → Pay with a card → Agent processes the order confirmation → Tracks the shipment

The inbox handles the communication. PayBox handles the money. Together, they close the gap between an agent that understands what to do and one that actually does it.

How the Integration Works

PayBox sits as a payment layer inside your Mermail agent's stack. When your agent needs to pay for something — a SaaS subscription, a marketplace purchase, a DeFi move — PayBox handles the transaction while Mermail handles the email lifecycle around it.

Here's the technical breakdown:

• Wallet keys are protected by MPC (threshold cryptography) and TEEs (secure enclaves). No single party — not Mermail, not PayBox, not the AI — ever holds a complete private key.
• Card payments run through Visa's agentic commerce protocol. PayBox transacts without ever seeing or storing the raw card number.
• Passkey approvals are scoped to a single action and expire after use. A captured approval can't be replayed or expanded.
• Every Mermail inbox already has user-controlled, encrypted storage. PayBox extends this model to payment credentials — cards and wallet fragments live in the same security boundary as your mailbox data.

PayBox launches with support for Solana and EVM-compatible chains including Ethereum, Hyperliquid, Base, Robinhood Chain, Arbitrum, and Polygon — with more chains rolling out steadily.

Two Control Models. You Choose.

Mermail currently supports the Always Ask model: every transaction requires your passkey approval. The agent can research, plan, and prepare all day — money only moves when you say so. An autonomous governance layer is under active development (see below).

Always Ask — Every single transaction requires your passkey approval. The agent can research, plan, and prepare all day. Money only moves when you say so.

Autonomous (coming soon) — We're building an open-source governance layer for agentic commerce called Qusto, a self-hosted control plane for x402 payments that evaluates buyer/seller policy before funds move, traces the full HTTP-to-chain lifecycle, and keeps you in control of keys, policy versions, and retention. Autonomous mode will ship once Qusto reaches community review. We'd love your help — star the repo and contribute

Changing permissions always requires a new passkey approval from you. Every authorization is scoped to a single action. Access can be revoked instantly, at any time.

Why This Matters for Agent Builders

For months, we've watched builders hit the same wall: their agent can do everything up to the payment step, then they need a human to pull out a credit card. That handoff is where autonomy dies.

Mermail + PayBox removes that handoff without removing your control. The key word is non-custodial. You're not handing your funds to a third-party custodian. You're not trusting an AI agent with unrestricted access. MPC splits the keys across hardware-isolated enclaves so that no single device, session, or party can sign alone. A compromised agent runtime doesn't give an attacker the ability to move funds — the missing key pieces simply aren't there.

This is backed by the same infrastructure that secures over $50 billion in assets and over 10 million wallets for leading crypto companies — MoonPay's platform of 1,700+ enterprise clients, strengthened by Sodot's key management technology.

Getting Started

If you already have a Mermail inbox for your agent, PayBox is available as an integrated payment layer. Here's what setup looks like:

1. Enable PayBox in your Mermail dashboard — it activates as a payment layer on your existing agent inbox.
2. Create or import a wallet (Solana, EVM chains) and optionally add payment cards.
3. Set your permission model — currently Always Ask (passkey approval for every transaction).
4. Register a passkey — this is your approval mechanism. One action, one approval, one use.

That's it. Your agent can now spend money. Every transaction confirmation lands in its Mermail inbox, keeping the full financial thread in one place.

What's Next

This integration is just the beginning. We're building deeper into the payment layer — enabling agents to route swaps, manage subscriptions autonomously, pay invoices on receipt, and act on financial opportunities across the open market. All governed by the same user-defined approval rules.

Mermail already lets your agent own the whole email conversation. Now it lets your agent own the transaction, too.

AI is moving from software that responds to software that acts. Mermail + PayBox is the infrastructure that lets it participate safely in the global economy.

→ Enable PayBox in your Mermail dashboard
→ Read the PayBox docs at paybox.sh
→ Explore the Mermail MCP tools