resend

Install the resend package, initialize it with your RESEND_API_KEY, and call resend.emails.send() with from, to, subject, and html. The SDK returns { data, error } instead of throwing, so check error explicitly and pass an idempotency key for safe retries.

Use batch sending for 2-100 distinct emails without attachments or scheduling, since batches are atomic and fail entirely if one email is invalid. Use single sends when you need attachments, scheduled delivery, or per-email isolation.

Resend webhook payloads contain metadata only to support large emails and serverless body-size limits. Call resend.emails.receiving.get() with the email_id from the event to retrieve the body, and the attachments API for download URLs, which expire after one hour.

Read the raw request body as text, then call resend.webhooks.verify() with the payload, the svix-id, svix-timestamp, and svix-signature headers, and your RESEND_WEBHOOK_SECRET. Parsing JSON before verification breaks the signature check.

No, the sending APIs covered here are for transactional email like receipts and notifications. For marketing campaigns with unsubscribe links and engagement tracking to large lists, use Resend Broadcasts instead of batch sending.

Templates are created as drafts and cannot send until published. Call resend.templates.publish() or chain .publish() after create; publishing is synchronous, so no delay is needed before sending.