OTP (Transactional Code Emails)

What it is

OTP is a dedicated transactional endpoint designed for speed and safety. It supports:

• Redis rate limits per recipient and per org
• {{variables}} templating (including {{otp}})

Endpoint

POST /api/v1/emails/otp

Required headers

Create the key in the dashboard under API keys (not via Swagger). Then:

• X-API-Key: eg_... or Authorization: Bearer eg_...
• Content-Type: application/json

Do not use a dashboard JWT for this endpoint.

Required body fields

• to (recipient email)
• otp (code) or templateId + variables (depending on your template workflow)

Production notes (deliverability + safety)

• from must use a domain your org has verified; unverified domains are rejected (e.g. DOMAIN_NOT_VERIFIED).
• When rate limits are exceeded, the API returns 429 Too Many Requests.

Example (curl)

curl -X POST "$PUBLIC_API_URL/api/v1/emails/otp" \
  -H "X-API-Key: eg_••••" \
  -H "Content-Type: application/json" \
  -d '{
    "to": "user@gmail.com",
    "from": "noreply@yourdomain.com",
    "otp": "482913",
    "subject": "Your login code",
    "html": "<p>Code: <strong>{{otp}}</strong></p>"
  }'

Replace $PUBLIC_API_URL with your API origin (e.g. https://prod-api.mailchamp.org).