REST API

The REST API allows you to send emails from any application using standard HTTP requests. Use it from any backend, serverless function, or CI/CD pipeline — no Cloudflare Workers binding is required.

For the full OpenAPI specification, refer to the Email Sending API reference ↗.

Endpoint

POST https://api.cloudflare.com/client/v4/accounts/{account_id}/email/sending/send

Authentication

Authenticate with a Cloudflare API token that has permission to send emails. Include it in the Authorization header:

Authorization: Bearer <API_TOKEN>

Send an email

Simple email

curl "https://api.cloudflare.com/client/v4/accounts/{account_id}/email/sending/send" \
  --header "Authorization: Bearer <API_TOKEN>" \
  --header "Content-Type: application/json" \
  --data '{
    "to": "recipient@example.com",
    "from": "welcome@yourdomain.com",
    "subject": "Welcome to our service!",
    "html": "<h1>Welcome!</h1><p>Thanks for signing up.</p>",
    "text": "Welcome! Thanks for signing up."
  }'

Explain Code

Multiple recipients

curl "https://api.cloudflare.com/client/v4/accounts/{account_id}/email/sending/send" \
  --header "Authorization: Bearer <API_TOKEN>" \
  --header "Content-Type: application/json" \
  --data '{
    "to": ["user1@example.com", "user2@example.com"],
    "from": { "address": "newsletter@yourdomain.com", "name": "Newsletter Team" },
    "subject": "Monthly Newsletter",
    "html": "<h1>This month'\''s updates</h1>",
    "text": "This month'\''s updates"
  }'

Explain Code

With CC and BCC

curl "https://api.cloudflare.com/client/v4/accounts/{account_id}/email/sending/send" \
  --header "Authorization: Bearer <API_TOKEN>" \
  --header "Content-Type: application/json" \
  --data '{
    "to": "customer@example.com",
    "cc": ["manager@company.com"],
    "bcc": ["archive@company.com"],
    "from": "orders@yourdomain.com",
    "reply_to": "support@yourdomain.com",
    "subject": "Order Confirmation #12345",
    "html": "<h1>Your order is confirmed</h1>",
    "text": "Your order is confirmed"
  }'

Explain Code

Attachments

Send files by including base64-encoded content in the attachments array:

curl "https://api.cloudflare.com/client/v4/accounts/{account_id}/email/sending/send" \
  --header "Authorization: Bearer <API_TOKEN>" \
  --header "Content-Type: application/json" \
  --data '{
    "to": "customer@example.com",
    "from": "invoices@yourdomain.com",
    "subject": "Your Invoice",
    "html": "<h1>Invoice attached</h1><p>Please find your invoice attached.</p>",
    "attachments": [
      {
        "content": "JVBERi0xLjQKJeLjz9MK...",
        "filename": "invoice-12345.pdf",
        "type": "application/pdf",
        "disposition": "attachment"
      }
    ]
  }'

Explain Code

Custom headers

Set custom headers for threading, list management, or tracking. Refer to the email headers reference for the full list of allowed headers.

curl "https://api.cloudflare.com/client/v4/accounts/{account_id}/email/sending/send" \
  --header "Authorization: Bearer <API_TOKEN>" \
  --header "Content-Type: application/json" \
  --data '{
    "to": "user@example.com",
    "from": "notifications@yourdomain.com",
    "subject": "Your weekly digest",
    "html": "<h1>Weekly Digest</h1>",
    "headers": {
      "List-Unsubscribe": "<https://yourdomain.com/unsubscribe?id=abc123>",
      "List-Unsubscribe-Post": "List-Unsubscribe=One-Click",
      "X-Campaign-ID": "weekly-digest-2026-03"
    }
  }'

Explain Code

Response

A successful response returns the delivery status for each recipient:

{
  "success": true,
  "errors": [],
  "messages": [],
  "result": {
    "delivered": ["recipient@example.com"],
    "permanent_bounces": [],
    "queued": []
  }
}

Explain Code

• delivered - Email addresses to which the message was delivered immediately
• permanent_bounces - Email addresses that permanently bounced
• queued - Email addresses for which delivery was queued for later

Error handling

The REST API returns standard Cloudflare API error responses. A failed request returns an errors array with numeric error codes and machine-readable messages:

{
  "success": false,
  "errors": [
    {
      "code": 10001,
      "message": "email.sending.error.invalid_request_schema"
    }
  ],
  "messages": [],
  "result": null
}

Explain Code

Common REST API error codes:

HTTP Status	Code	Message	Description
400	10001	email.sending.error.invalid_request_schema	Invalid request format
400	10200	email.sending.error.email.invalid	Invalid email content
400	10201	email.sending.error.email.no_content_length	Missing content length
400	10202	email.sending.error.email.too_big	Email exceeds size limit
403	10203	email.sending.error.email.sending_disabled	Sending disabled for this zone/account
429	10004	email.sending.error.throttled	Rate limit exceeded
500	10002	email.sending.error.internal_server	Internal server error

Workers binding vs REST API errors

The REST API returns standard Cloudflare API numeric error codes, while the Workers binding throws errors with string codes (for example, E_SENDER_NOT_VERIFIED). Refer to the Workers API error codes table for the string error codes.

Next steps

• Refer to the Email Sending API reference ↗ for the full request and response schemas.
• See the Workers API for sending emails directly from Cloudflare Workers using bindings.
• Review email headers for threading, list management, and custom tracking headers.