# StableEmail Subdomain Inbox Create

> StableEmail Subdomain Inbox Create is a paid API for AI agents from StableEmail at stableemail.dev, paid per call via MPP or x402, $0.25/call, status unknown (last checked 2026-10-11, last successful call 2026-04-13).

Creates a new email inbox on a custom subdomain, optionally forwarding incoming mail to another address, for $0.25 USDC.

## Facts

- Endpoint: POST https://stableemail.dev/api/subdomain/inbox/create?utm_source=zero.xyz
- Price: $0.25/call
- Payment: MPP, x402
- Status: unknown
- Last checked: 2026-10-11
- Last successful call: 2026-04-13
- Success rate: 33% of calls made through Zero
- Activations on Zero: 3
- 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-create-0718fbda
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_B5iiVW7zF-soQj4PrhR4d

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-create-0718fbda -d '<json body>'
```

Example prompt: Create a new inbox called support@mycompany.stableemail.dev and forward any incoming mail to me@gmail.com.

## When to prefer this

Use this endpoint when you need to programmatically create a new receiving inbox on a subdomain you already own on StableEmail, with optional forwarding to a real address. Prefer this over the basic stableemail.dev inbox buy endpoint when you have a custom subdomain and want inbox addresses on that subdomain rather than the shared stableemail.dev domain.

## Known failure modes

- Subdomain not owned or not verified — inbox creation rejected
- localPart already exists on that subdomain — conflict error
- Subdomain inbox limit of 100 reached — creation blocked
- Invalid localPart format (must be lowercase alphanumeric with dots/dashes, 1-64 chars)
- Invalid subdomain format (must be lowercase alphanumeric with hyphens, no double hyphens)
- Invalid forwardTo email address format
- Insufficient USDC balance for $0.25 payment
- Payment failure or x402 protocol error

## How this service works

Create an inbox on your subdomain ($0.25). Max 100 inboxes, 500 messages each. Message content and attachments retained for 90 days.

## Output

Returns a confirmation that the inbox has been created on the specified subdomain with the given local part, along with inbox details such as the full email address and forwarding configuration. Up to 100 inboxes per subdomain, each storing up to 500 messages for 90 days.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "subdomain",
  "localPart"
 ],
 "properties": {
  "forwardTo": {
   "type": "string",
   "format": "email",
   "pattern": "^(?!\\.)(?!.*\\.\\.)([A-Za-z0-9_'+\\-\\.]*)[A-Za-z0-9_+-]@([A-Za-z0-9][A-Za-z0-9\\-]*\\.)+[A-Za-z]{2,}$"
  },
  "localPart": {
   "type": "string",
   "pattern": "^[a-z0-9][a-z0-9._+-]{0,62}[a-z0-9]$",
   "maxLength": 64,
   "minLength": 1
  },
  "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-create-0718fbda/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)