FAQ & Troubleshooting

Common issues

• I received a 401 Unauthorized — Verify your API key and ensure it's included as Authorization: Bearer YOUR_API_KEY.
• I received a 429 Too Many Requests — You've hit a rate limit. Implement exponential backoff and reduce parallel requests.
• Messages are marked as bounced — Check the bounce reason in the message status and ensure your sending domain's DNS (SPF/DKIM) is configured.

Debugging tips

• Use the message status endpoints to inspect delivery events.
• Check webhook logs in the dashboard to see inbound notifications.
• Review raw SMTP responses for email rejections.

Support

If you need help, open a support ticket from the dashboard or email support@castbrick.com. Include message IDs and timestamps for faster troubleshooting.