# StableEmail Buy Custom Email Subdomain

> StableEmail Buy Custom Email Subdomain is a paid API for AI agents from StableEmail at stableemail.dev, paid per call via MPP or x402, $5/call, status unknown (last checked 2026-10-09, last successful call 2026-06-12).

Purchase a custom email subdomain on stableemail.dev for $5 USDC, enabling branded email addresses like yourname.stableemail.dev

## Facts

- Endpoint: POST https://stableemail.dev/api/subdomain/buy?utm_source=zero.xyz
- Price: $5/call
- Payment: MPP, x402
- Status: unknown
- Last checked: 2026-10-09
- Last successful call: 2026-06-12
- Success rate: 100% of calls made through Zero
- Activations on Zero: 1
- Provider: StableEmail
- Docs: https://stableemail.dev
- Website: https://stableemail.dev
- Tags: email, send, inbox, forwarding, subdomain, social
- Canonical page: https://www.zero.xyz/c/stableemail-buy-ac5a5e51
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_ghQQq4YlSNq4turXi_vKi

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability stableemail-buy-ac5a5e51 -d '<json body>'
```

Example prompt: Can you register the subdomain 'myproject' on StableEmail so I can use it for custom email addresses — it's stableemail.dev and costs $5?

## When to prefer this

Use this endpoint when you need a persistent, branded custom email subdomain (e.g. myapp.stableemail.dev) for routing or receiving email, especially when you want no-account, pay-once setup. Prefer over the inbox Buy endpoint when you need a shared namespace for multiple inboxes under one subdomain rather than a single inbox address.

## Known failure modes

- Subdomain already taken — returns conflict error
- Invalid subdomain format — must be lowercase alphanumeric with hyphens, 3-30 chars, no double hyphens, not starting or ending with hyphen
- Insufficient USDC balance — payment of $5 USDC fails
- Subdomain contains reserved or blocked words — rejected
- Network timeout during payment processing

## How this service works

Purchase a custom email subdomain on stableemail.dev ($5)

## Output

Returns confirmation that the custom email subdomain has been purchased and registered on stableemail.dev, enabling the use of that subdomain for email forwarding and receiving without needing an account.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "subdomain"
 ],
 "properties": {
  "subdomain": {
   "type": "string",
   "allOf": [
    {
     "pattern": "^[a-z0-9][a-z0-9-]{1,28}[a-z0-9]$"
    },
    {
     "pattern": "^(?!.*--)"
    }
   ]
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/stableemail-buy-ac5a5e51/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from stableemail.dev](https://www.zero.xyz/host/stableemail.dev/llms.txt)