# StableEmail Forwarding Inbox Send

> StableEmail Forwarding Inbox Send is a paid API for AI agents from StableEmail at stableemail.dev, paid per call via x402 or MPP, $0.005/call, status unknown (last checked 2026-10-11, last successful call 2026-08-04).

Sends an email from the caller's own forwarding inbox username on stableemail.dev to one or more recipients

## Facts

- Endpoint: POST https://stableemail.dev/api/inbox/send?utm_source=zero.xyz
- Price: $0.005/call
- Payment: x402, MPP
- Status: unknown
- Last checked: 2026-10-11
- Last successful call: 2026-08-04
- Success rate: 96% of calls made through Zero
- Rating: 3.7 / 5 from 2 reviews
- Activations on Zero: 269
- 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-send-21e55982
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap__FdXLQpCFdUwPPsGHiN6p

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-send-21e55982 -d '<json body>'
```

Example prompt: Send an email from my stableemail inbox 'myproject' to alice@example.com with the subject 'Project Update' and the message body 'Hi Alice, just wanted to let you know the project is on track. Best, Bob.'

## When to prefer this

Choose this endpoint when you need to send email from a specific named forwarding inbox on stableemail.dev (i.e. username@stableemail.dev) rather than the generic relay address. At $0.005 per send it is cheaper than the generic Send endpoint ($0.02). Use it when the sender identity/username matters or when you want replies to go to the inbox you own.

## Known failure modes

- Invalid or unregistered username — inbox does not exist or has expired
- Invalid recipient email format — 400 validation error
- Missing required fields (username, to, subject) — 400 bad request
- Inbox not funded or expired — payment/authorization failure
- Attachment size or count exceeds limits (max 5 attachments, 5MB each) — 400 error
- Payment failure — insufficient USDC balance for $0.005 charge
- Too many recipients — to or cc array exceeds 50 items

## How this service works

Send email from your forwarding inbox on stableemail.dev ($0.005)

## Output

A confirmation that the email was sent from the specified stableemail.dev forwarding inbox to the listed recipients. No body payload is returned beyond a success acknowledgment.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "username",
  "to",
  "subject"
 ],
 "properties": {
  "cc": {
   "type": "array",
   "items": {
    "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,}$"
   },
   "maxItems": 50,
   "minItems": 1
  },
  "to": {
   "type": "array",
   "items": {
    "type": "string",
    "format": "email",
    "pattern": "^(?!\\.)(?!.*\\.\\.)([A-Za-z0-9_'+\\-\\.]*)[A-Za-z0-9_+-]@([A-Za-z0-9][A-Za-z0-9\\-]*\\.)+[A-Za-z]{2,}$"
   },
   "maxItems": 50,
   "minItems": 1
  },
  "html": {
   "type": "string",
   "maxLength": 256000
  },
  "text": {
   "type": "string",
   "maxLength": 256000
  },
  "replyTo": {
   "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,}$"
  },
  "subject": {
   "type": "string",
   "maxLength": 998,
   "minLength": 1
  },
  "username": {
   "type": "string",
   "allOf": [
    {
     "pattern": "^[a-z0-9][a-z0-9-]{1,28}[a-z0-9]$"
    },
    {
     "pattern": "^(?!.*--)"
    }
   ]
  },
  "attachments": {
   "type": "array",
   "items": {
    "type": "object",
    "required": [
     "content",
     "contentType",
     "filename"
    ],
    "properties": {
     "content": {
      "type": "string",
      "maxLength": 5000000
     },
     "filename": {
      "type": "string",
      "maxLength": 255,
      "minLength": 1
     },
     "contentType": {
      "type": "string",
      "maxLength": 255,
      "minLength": 1
     }
    }
   },
   "maxItems": 5
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/stableemail-send-21e55982/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)