Send a batch of emails

Send up to 100 transactional emails in a single request. Validation is all-or-nothing: if any item is invalid the whole batch is rejected and nothing is queued, so you never end up with a partial send. Pass an Idempotency-Key header to make retries safe — the same key replays the original result instead of re-sending. The response returns a batch_id; track the batch's per-status rollup with Retrieve a batch and stop the rest of it with Cancel a batch. To send one email, use Send or schedule an email. Requires the emails:send capability.