Skip to main content
The POST /v1/inboxes/{id}/send endpoint requires an Idempotency-Key header. If you retry with the same key, we return the original response without sending a duplicate email.

​
Usage

​
Rules

  • Unique per send - Generate a new UUID for each distinct send (e.g. uuidgen, crypto.randomUUID()).
  • Scoped to account - Keys are per-account, not global.
  • 24-hour expiry - Keys expire after 24 hours. Reusing an expired key creates a new send.
  • Same body - Retries must use the same request body. Changing the body with the same key returns an error.

​
Webhook idempotency

For webhooks, use event_id to deduplicate. We may deliver the same event more than once; your handler should be idempotent.