When Twilio SMS fails, developers rightly inspect requests and error codes. A cheaper check is often skipped: does the destination number meet the most basic sending conditions? Check that first, so a formatting issue does not become hours of API debugging.
SMS failures have three layers
| Layer | Typical issue |
|---|---|
| Contact data | Missing country code, abnormal length, truncated field, duplicate |
| Sending setup | Sender, destination support, messaging service, or app configuration |
| Consent and user state | Missing permission, opt-out, regulation, or carrier rule |
Check phone data before the API
Use international format
For cross-border SMS, keep the country code. Do not assume a system can infer a local number's country.
Compare original and normalized values
Forms and spreadsheets can remove plus signs or leading zeros. Keep both values to locate where the data changed.
Flag duplicates and abnormal input
Repeated sends distort results. Move obviously malformed values to a review queue.
A practical Twilio order
- Confirm suitable SMS-contact permission.
- Check format, country code, and completeness.
- Use LeadsAI or your approved phone-data workflow.
- Review Twilio error codes and sender configuration.
- Test the fix with a small compliant list.
Validation narrows the problem; it does not guarantee delivery. If the list starts in a sheet, use the Excel cleanup workflow first.
Excel Phone Numbers Are a Mess? Clean Them Before CRM Import
A phone column can quietly break CRM deduplication and sales assignment. Fix the format before it enters your system.
Phone Number Validation vs HLR Lookup: Do Not Pay for the Wrong Check
A correctly formatted number is not automatically ready for calling or messaging. Choose checking depth by the decision you need to make.