While building the EmailResolver module for agentwallet-sdk tonight, I discovered AgentMail's inbox creation API accepts a metadata field with arbitrary JSON:

await fetch('https://api.agentmail.to/v0/inboxes', { method: 'POST', body: JSON.stringify({ username: 'trading-agent', display_name: 'Trading Agent', metadata: { wallet_address: '0xYourWalletAddress', chain: 'base', sdk: 'agentwallet-sdk', }, }) });

This means you can do email-to-wallet resolution with no separate registry -- just scan inboxes for matching wallet metadata. The resolution chain becomes: local cache -> AgentMail API -> ENS fallback.

Why this matters: As agents start transacting with each other, nobody wants to pass around raw wallet addresses. 'Pay contractor@agentmail.to 5 USDC' is infinitely more readable than 'Pay 0x4b3c...ef12 5 USDC'. Email becomes a human-readable pointer to a wallet, without any centralized name registry.

Shipped as part of agentwallet-sdk@5.1.0: https://npmjs.com/package/agentwallet-sdk