Why aren’t my SMS messages delivered to one specific number and how do I fix it?
⚡Quick answer -
Most single-number SMS failures come down to one of five issues:
- DND or opt-out,
- DLT template/header mismatch,
- Wrong sender ID,
- Bad number format, or
- Promotional time-band restriction (10:00–21:00 IST). Run the five-step checklist below; you should see status = Delivered in SMS Logs after a resend.
When should I use this guide?
Use it if one customer isn’t receiving your SMS but other numbers work, and you want to isolate the cause in < 10 minutes.
1 — Prerequisites
Item | Where | Notes |
SMS Logs access | Dashboard → Logs → SMS | Need Status + Reason |
Template/Header IDs | Manage → SMS Templates | Check DLT mapping |
Recipient number | E.164 format | e.g., |
2 — Five-step quick diagnosis
- Open SMS Logs → filter by the recipient number; note Status + Reason.
- Validate number format → must be E.164 (
+91…). - Check DND/opt-out → if DND, switch to transactional route or WhatsApp.
- Verify DLT mapping → Header ↔ Template ↔ PE ID; variables exact.
- Time-band → For promotional SMS, send only 10:00-21:00 IST.
Resend the message; expect delivery within 2–5 minutes.
3 — Common causes & fixes
Cause | How to detect | Fix |
DND/opt-out | SMS Logs → Reason = | Use transactional route or WhatsApp with consent |
Template mismatch | Reason = | Map approved Header & Template; match variables |
Sender ID not allowed | Reason = | Choose permitted sender ID for route/geo |
Wrong number format | Reason = | Resend in |
Out-of-band time | Reason = | Schedule 10:00–21:00 IST |
Content filter | Reason = | Remove short-link / keyword; send again |
4 — Status/error code guide
SMS Logs Status | Carrier Code | Meaning | Next action |
Delivered |
| Handset confirmed | None |
Failed |
| Timed out after retries | Retry later |
Blocked – DLT |
| Template/header error | Fix DLT mapping |
Blocked – DND |
| Recipient opted-out | Use transactional route |
Undelivered |
| Generic failure | Check number & content |
Submitted |
| Awaiting DLR | Wait a few minutes |
5 — Workflow
Alt-text: “SMS passes DLT and carrier filters before reaching handset; blocks highlighted.”
6 — Confirm it worked
• Recent SMS shows Delivered in Logs.
• The recipient handset receives the message within 2–5 minutes.
7 — Troubleshooting matrix
Symptom | Check | Where | Fix |
No status / no log | API failure | Integration | Retry API; check key |
| Format or handset | Logs; phone | Use E.164; ask the user to restart |
| Opt-out | Logs | Switch to transactional template |
| Sender ID | SMS Templates | Map correct header |
8 — Escalate to Support
Send via Help → Chat or email support@myoperator.com
Keywords - SMS not delivered, DLT reject, DND block, sender ID mismatch, MyOperator SMS failure
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