Purchase a custom email subdomain (yourname.stableemail.dev) for $5 USDC via MPP/x402 micropayment.
What it does
This endpoint lets you purchase a custom email subdomain under stableemail.dev for a one-time payment of $5 USDC. You POST a JSON body with your desired subdomain name (3–30 characters, lowercase alphanumeric plus hyphens), pay via the x402/MPP micropayment protocol, and receive a confirmed subdomain like `yourname.stableemail.dev`. DNS verification completes within approximately 5 minutes after purchase. Once active, you can send email from any address on that subdomain at $0.005 per message, add up to 50 authorized wallet signers, create per-address inboxes ($0.25 each, up to 100), and configure catch-all forwarding.
The endpoint is part of StableEmail, a pay-per-use email platform that requires no API keys or accounts. Payment settles in USDC on Base (eip155:8453), Solana, or Tempo. The standard x402/MPP flow applies: send your request, receive a 402 with payment challenge, sign the payment, and resend. Wallet ownership from the payment header establishes you as the subdomain owner for all subsequent management operations (sending, signers, inbox creation, settings updates via SIWX authentication).
The endpoint accepts only POST requests. The OpenAPI spec provides a full JSON schema for the request body. AI agents can integrate via the agentcash-skills MCP server (`npx -y agentcash@latest`) or any x402/MPP-compatible client.
Capabilities
Use cases
- —AI agents purchasing branded email subdomains programmatically for outbound communication
- —Developers setting up project-specific email domains without traditional registrar workflows
- —Creating disposable or purpose-specific email subdomains with wallet-based ownership
- —Building multi-tenant email systems where each tenant gets their own subdomain
Fit
Best for
- —Agents or bots that need to send email from a branded subdomain without account setup
- —Developers wanting instant email subdomain provisioning via a single API call
- —Crypto-native workflows where wallet-based identity replaces traditional accounts
Not for
- —Sending email from fully custom top-level domains (only *.stableemail.dev subdomains)
- —High-volume bulk email campaigns (subdomain sending is $0.005/email, no bulk pricing disclosed)
- —Users without a crypto wallet or x402/MPP-compatible client
Quick start
# Purchase a subdomain via agentcash CLI
npx agentcash fetch POST https://stableemail.dev/api/subdomain/buy \
--body '{"subdomain": "myproject"}'Example
Request
{
"subdomain": "myproject"
}Response
{
"success": true,
"dnsStatus": "pending",
"subdomain": "myproject.stableemail.dev"
}Endpoint
Quality
Full OpenAPI 3.1 schema with detailed x-guidance documentation, clear pricing ($5 USDC), well-defined request/response shapes, and comprehensive endpoint coverage. The probe returned 405 because the endpoint only accepts POST (not HEAD/GET), which is expected behavior. The root landing page loads successfully (200). Minor deductions: no live 402 challenge was captured for this specific endpoint, and response schemas lack formal OpenAPI definitions (only described in guidance text).
Warnings
- —Probe returned 405 because HEAD/GET were tried but endpoint only accepts POST — this is expected, not an outage
- —No live 402 payment challenge was captured in the probe for this specific endpoint
- —Response schema is documented only in x-guidance text, not as formal OpenAPI response schemas
Citations
- —Subdomain purchase costs $5 USDChttps://stableemail.dev
- —Subdomain names must be 3-30 chars, lowercase alphanumeric + hyphenshttps://stableemail.dev/.well-known/x402
- —DNS verification takes ~5 minutes after purchasehttps://stableemail.dev/.well-known/x402
- —Payment settles in USDC on Base, Solana, or Tempo via x402/MPPhttps://stableemail.dev
- —Up to 50 authorized wallet signers per subdomainhttps://stableemail.dev
- —Agent integration available via agentcash-skills MCP serverhttps://stableemail.dev