Base URL
The SendKit API is available at:
Authentication
All API requests require a Bearer token in the Authorization header. You can create API keys from the dashboard.
Authorization: Bearer sk_your_api_key
Keep your API key secret. Do not expose it in client-side code or public repositories.
Rate limiting
API requests are rate limited per team based on your plan. When you exceed the limit, the API returns a 429 status code with a Retry-After header indicating how many seconds to wait.
Send email — POST /emails
| Plan | Rate limit | Monthly quota |
|---|
| Free | 60 req/min | 3,000 emails |
| 10K | 120 req/min | 10,000 emails |
| 25K | 120 req/min | 25,000 emails |
| 50K | 300 req/min | 50,000 emails |
| 75K | 300 req/min | 75,000 emails |
| 100K | 600 req/min | 100,000 emails |
| 150K | 600 req/min | 150,000 emails |
| 250K | 600 req/min | 250,000 emails |
| 500K | 1,200 req/min | 500,000 emails |
| 750K | 1,200 req/min | 750,000 emails |
| 1M | 1,200 req/min | 1,000,000 emails |
| 2M | 1,200 req/min | 2,000,000 emails |
| 5M | 1,200 req/min | 5,000,000 emails |
Validate email — POST /emails/validate
Fixed at 60 requests per minute for all plans.
Rate limit error response
{
"name": "rate_limit_exceeded",
"message": "Rate limit exceeded. Please retry after 30 seconds."
}
Errors
The API uses conventional HTTP status codes. All error responses include a name and message field.
| Status | Description |
|---|
200 | Success |
202 | Accepted — request received and will be processed asynchronously |
401 | Missing or invalid API key |
422 | Validation error (invalid parameters, unverified domain, etc.) |
429 | Rate limit exceeded |
{
"name": "validation_error",
"message": "The from address domain is not verified."
}
Common validation errors
| Error message | Cause |
|---|
| The from address domain is not verified. | The domain in the from address is not verified in your account. |
| Monthly email quota exceeded. | Your team has reached its monthly sending limit. |
| Sending is paused for this account. | Sending has been paused for your account. Contact support. |
