communications
Twilio Errors
Twilio errors are 5-digit codes (e.g., 21211 invalid 'To' number, 30003 unreachable destination, 20003 authentication error). SMS delivery failures (3xxxx) are the most common production issue.
Twilio error codes group by domain: 1xxxx = REST API, 2xxxx = TwiML/voice, 3xxxx = messaging, 4xxxx = video, 5xxxx = chat. SMS delivery: 30003 (unreachable), 30005 (unknown destination), 30006 (landline), 30007 (carrier filtered). Always check Twilio Console → Logs → Messaging for the exact failure reason on a per-message basis.
Official docs
https://www.twilio.com/docs/api/errors
Status page
https://status.twilio.com/
Support
https://support.twilio.com/