Introduction - SendKit

Base URL

The SendKit API is available at:

https://api.sendkit.dev

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	Daily limit
Free	60 req/min	3,000 emails	100 emails
10K	120 req/min	10,000 emails	No limit
25K	120 req/min	25,000 emails	No limit
50K	300 req/min	50,000 emails	No limit
75K	300 req/min	75,000 emails	No limit
100K	600 req/min	100,000 emails	No limit
150K	600 req/min	150,000 emails	No limit
250K	600 req/min	250,000 emails	No limit
500K	1,200 req/min	500,000 emails	No limit
750K	1,200 req/min	750,000 emails	No limit
1M	1,200 req/min	1,000,000 emails	No limit
2M	1,200 req/min	2,000,000 emails	No limit
5M	1,200 req/min	5,000,000 emails	No limit

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.

Health check

​Base URL

​Authentication

​Rate limiting

​Send email — POST /emails

​Validate email — POST /emails/validate

​Rate limit error response

​Errors

​Common validation errors

Base URL

Authentication

Rate limiting

Send email — `POST /emails`

Validate email — `POST /emails/validate`

Rate limit error response

Errors

Common validation errors