Why SMS Messages Fail to Deliver (and How to Fix It)
Why SMS Messages Fail to Deliver (and How to Fix It)
When a message fails, JustCall shows a delivery status in the conversation thread. This guide explains what each failure means and how to fix it.
Common Failure Reasons
1. Invalid or unreachable number
Status: Failed Cause: The recipient number is disconnected, incorrectly formatted, or is a landline that cannot receive SMS.
Fix:
- Verify the number format includes the country code (e.g., +1 for US/Canada).
- Confirm the number is a mobile or VoIP number that accepts SMS.
- Remove landline numbers from your contact lists.
2. Carrier filtering
Status: Failed or Undelivered Cause: The carrier flagged your message as spam. This happens when message content matches spam patterns, your sending volume is unusually high, or your 10DLC registration is missing or incomplete.
Fix:
- Complete your 10DLC registration if you haven't already.
- Avoid spam trigger words (FREE, WINNER, ACT NOW) in message content.
- Include your business name in messages so recipients recognize the sender.
- Ensure every recipient has opted in to receive your messages.
3. 10DLC not registered
Status: Failed Cause: US carriers require 10DLC registration for all business messaging on local (10-digit) numbers. Without it, carriers block messages outright.
Fix:
- Register your brand and campaign in JustCall's 10DLC settings. See 10DLC Registration Guide.
- Allow 1–7 business days for approval.
- Use a toll-free number as an interim solution while 10DLC registration is pending.
4. Toll-free number not verified
Status: Failed Cause: Toll-free numbers require verification before sending SMS. Unverified toll-free numbers are blocked by carriers.
Fix:
- Complete toll-free verification under Phone Numbers → Compliance Centre.
- Allow 5–10 business days for carrier review.
5. Recipient opted out
Status: Failed Cause: The recipient previously replied STOP to your number. Carriers enforce opt-outs at the network level.
Fix:
- You cannot message opted-out contacts. The recipient must reply START to re-subscribe.
- Check opt-out status in the contact's conversation history.
6. Daily sending limit reached
Status: Failed Cause: JustCall enforces daily SMS limits based on your plan and number type to prevent abuse and protect sender reputation.
Fix:
- Check your current limits under Settings → SMS Settings.
- Upgrade your plan or request a limit increase through support.
- See Managing Daily Calling and Texting Limits.
7. International messaging not enabled
Status: Failed Cause: International SMS requires explicit activation. By default, JustCall numbers only send to the number's home country.
Fix:
- Enable international messaging under Settings → Phone Numbers → [Your Number] → Messaging Permissions.
- Note: international SMS rates vary by destination country.
How to Check Delivery Status
- In the conversation: Each message shows a status icon (sent, delivered, failed).
- In SMS Logs: Go to Analytics → SMS Logs to filter by status, date range, and number.
- Via webhook: Configure SMS status webhooks under Settings → Webhooks to receive real-time delivery updates in your CRM or application.
When to Contact Support
Contact JustCall support if:
- Messages fail consistently to a specific carrier (AT&T, T-Mobile, Verizon).
- Your 10DLC registration was approved but messages still fail.
- You see a delivery error code not covered here.
Include your JustCall number, the recipient number, the timestamp, and the error message when opening a ticket.