Rules
- Resend + React Email for transactional emails — JSX templates, type-safe
- Template pattern: one React component per email type, props for dynamic content
- Queue long-running sends — don't block API response waiting for email delivery
- Bounce handling: monitor bounces, remove invalid addresses, update user records
- Unsubscribe link: required by law (CAN-SPAM, GDPR) — one-click unsubscribe
- SPF/DKIM/DMARC: configure DNS records for deliverability
- Test emails: use Resend test mode or Ethereal for development
- Plain text fallback: always provide text version alongside HTML