# StableEmail Send

> StableEmail Send is a paid API for AI agents from StableEmail at stableemail.dev, paid per call via MPP, $0.020000/call, status healthy (last checked 2026-10-12, last successful call 2026-10-12).

Sends an email from relay@stableemail.dev to one or more recipients with optional CC, reply-to, HTML/text body, and attachments

## Facts

- Endpoint: POST https://stableemail.dev/api/send?utm_source=zero.xyz
- Price: $0.020000/call
- Payment: MPP
- Status: healthy
- Last checked: 2026-10-12
- Last successful call: 2026-10-12
- Success rate: 99% of calls made through Zero
- Rating: 5.0 / 5 from 8 reviews
- Activations on Zero: 760
- 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-e2635eee
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_2qo7J9qhcZd50s5ctMjxw

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-e2635eee -d '<json body>'
```

Example prompt: Send an email to alice@example.com with the subject 'Your order has shipped' and a plain-text body saying 'Hi Alice, your order #12345 has been dispatched and will arrive in 3-5 days. Thanks for shopping with us!' — set the reply-to address to support@mystore.com.

## When to prefer this

Use this endpoint when you need to send a one-off or programmatic email without setting up SMTP credentials, API keys, or an account — ideal for AI agents, automation scripts, or serverless workflows that need pay-per-use email delivery billed in USDC. Prefer this over full email platforms (SendGrid, Mailgun) when you want zero onboarding friction and micropayment pricing.

## Known failure modes

- Invalid recipient email format returns a 400 validation error
- Missing required fields (to, subject) returns a 400 error
- Payment failure or insufficient USDC balance returns a 402
- Attachment too large (over 5MB per attachment or more than 5 attachments) returns a 400
- Recipient server rejects delivery — email may bounce silently after API returns success
- Rate limiting or abuse detection may block sending

## How this service works

Send an email from "StableEmail" <relay@stableemail.dev> ($0.02)

## Output

Confirmation that the email was dispatched from relay@stableemail.dev to the specified recipients; costs $0.02 USDC per call. No response body with tracking ID is expected — a 2xx status indicates successful delivery hand-off.

## Example request

```json
{
 "to": [
  "zero-qa@agentmail.to"
 ],
 "text": "This is a test email to verify the Send API is functioning correctly. This message contains plain text content only.",
 "subject": "Test Email - API Verification"
}
```

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "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
  },
  "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
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "from",
  "success",
  "messageId"
 ],
 "properties": {
  "from": {
   "type": "string"
  },
  "success": {
   "type": "boolean"
  },
  "messageId": {
   "type": "string"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/stableemail-send-e2635eee/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)