send-email

To send transactional emails with the Resend API, install the appropriate SDK for your language, such as the Resend Node.js or Python package, and implement a POST request to the /emails endpoint. Include an idempotency key to prevent duplicate sends.

Batch sending is supported by making a POST request to the Resend API /emails/batch endpoint. You can send up to 100 emails per request, but you must perform per-email input validation before sending the payload.

Idempotency keys prevent duplicate transactional emails by ensuring the API treats repeated requests as a single operation. You include a unique idempotency key in your request header so transient failures or retries do not result in multiple identical emails.

The recommended retry strategy for Resend API 429 and 500 errors is implementing exponential backoff. This approach systematically increases the delay between retry attempts to handle transient failures without overwhelming the API.

Yes, the Resend API supports integration with Go and curl workflows. You can install the Go SDK or use curl commands directly to quickly test sending transactional emails to safe addresses and review delivery settings.

Per-email validation is required for batch sending because the Resend API processes up to 100 emails in a single request. Validating each email individually before sending ensures your payload is correctly formatted and prevents batch failures.