Rate limits

Rate limits are applied per API key using a sliding window. Each endpoint belongs to a tier that determines its quota.

Last updated April 19, 2026

Tiers

Tier	Limit	Description
read	1,000 / min	GET requests (list, retrieve).
write	200 / min	POST, PATCH, DELETE (create, update, delete).
send	100 / min	Sending email (POST /v1/messages, POST /v1/threads/:id/reply).
verification	1 / min	Domain verification (POST /v1/domains/:id/verification).

Response headers

Every authenticated response includes rate limit headers:

Header	Description
X-RateLimit-Limit	Maximum requests allowed in the current window.
X-RateLimit-Remaining	Requests remaining in the current window.
X-RateLimit-Reset	Unix timestamp (seconds) when the window resets.
Retry-After	Seconds to wait before retrying. Present on 429 responses only.

Handling 429 responses

When you exceed the limit, the API returns a 429 status with a Retry-After header containing the number of seconds to wait. Back off for that duration before retrying.