Phone System · 1 min read
Understanding Common SMS Delivery Errors
A failed SMS or MMS usually includes an error code showing where delivery stopped. Find the failed message in Conversations, note the code and use this guide.
Don't keep resending a failed message without fixing the cause. Repeated sends to opted-out, invalid or filtered numbers can hurt your reputation.
Quick reference
| Code | Meaning | What to do | | --- | --- | --- | | 21211 | Invalid "To" number | Fix the number and use the country code | | 21408 | Country not enabled | Enable the region or check the country code | | 21610 | Recipient opted out | Don't text until they opt back in | | 21614 | Not a mobile number | Call instead, or get a mobile number | | 30003 | Handset unreachable | Try later; the phone may be off | | 30004 | Message blocked | The recipient or carrier blocked it | | 30005 | Unknown or inactive number | Remove or update the number | | 30006 | Landline or unreachable carrier | Use another channel | | 30007 | Carrier filtering | Review content, consent and registration | | 30008 | Unknown error | Retry later; contact support if repeated | | 30032 | Toll-free number not verified | Complete toll-free verification | | 30034 | Number not linked to an A2P campaign | Link the number to an approved campaign |
Each code has its own article with more detail.
If the code doesn't explain it
Check whether the issue affects one contact, one carrier, one number or every message. That points to whether the cause is the contact, the carrier, your number's registration or your content.