Twilio Error Code 30005

Twilio Error 30005 carries the message "Unknown destination handset." It is a delivery error (not a send-time validation rejection), meaning Twilio accepted your message and handed it to the carrier, but the carrier reported back that the destination number is unknown, no longer exists, or otherwise cannot receive your SMS. The message status ends as undelivered with ErrorCode 30005.

What causes Twilio Error 30005?

Per Twilio's error reference, 30005 is returned by the downstream carrier, not generated inside Twilio. The most common causes are:

• The number no longer exists or was deactivated. This is the single most frequent cause — the line has been disconnected or recycled and the carrier no longer recognizes it.
• The destination cannot receive SMS. Landlines, certain VoIP numbers, and some non-mobile numbers will fail with 30005 even though they look valid.
• The To number is malformed or wrong. A number not in E.164 format (+[country code][subscriber number]) or with a transposed digit can resolve to an unassigned handset.
• Carrier-side blocking or filtering. T-Mobile, for example, offers recipients a setting that blocks SMS from business/long-code senders; messages to recipients with that feature on commonly return 30005.

30005 vs. 30003: Both are delivery failures, but 30003 ("Unreachable destination handset") usually means a valid phone is temporarily off, out of coverage, or roaming, while 30005 means the number itself is unknown/invalid. If you see 30003, retrying later can succeed; with 30005, retrying the same number usually will not.

How do I fix Twilio Error 30005?

1. Validate the number with Twilio Lookup. Before (or after) a failure, run the Lookup API with the line_type_intelligence package to confirm the number is a mobile line and is currently assigned. Drop landlines, fixed VoIP, and non-existent numbers from your send list. Twilio's docs now lead with API Key auth for Lookup; Account SID/Auth Token (used below) still works and is offered as the simpler option for quick or local testing.

curl -X GET "https://lookups.twilio.com/v2/PhoneNumbers/+15108675310?Fields=line_type_intelligence" \
  -u "$TWILIO_ACCOUNT_SID:$TWILIO_AUTH_TOKEN"

2. Confirm E.164 formatting. Ensure every To value is + followed by country code and the full subscriber number, with no spaces, dashes, or leading zeros (e.g., +447911123456, not 07911 123456).

3. Send a controlled test. Resend to the same number via a REST API request or the Twilio Console to confirm the error reproduces. Test a known-good number on the same carrier to isolate whether the problem is the recipient or your sending number.

4. Don't blindly retry the same number. Because 30005 typically indicates a permanently invalid handset, retrying wastes spend and can hurt your sender reputation. Suppress numbers that repeatedly return 30005.

5. Rule out carrier filtering. If failures cluster on one carrier (often T-Mobile), the recipient may have business-sender blocking enabled, or your number/traffic may be filtered — consider a verified A2P 10DLC registration, a toll-free number, or short code for better deliverability.

6. Escalate to Twilio if valid numbers fail. If numbers you've confirmed are active mobiles still return 30005, collect three or more Message SIDs from the last 24 hours and open a Twilio support request.

If you send through Courier, the ErrorCode and final status surface in your message logs and provider response — use Lookup-based list hygiene upstream so invalid handsets never reach the Twilio channel.