# X_NOTIFY_SMS_NUMBER_INVALID

## Means

an SMS number is not E.164

## Typical cause

the number smsChannel() resolved for a recipient is not +, a country code and up to 15 digits in all (E.164) — a local spelling a provider guesses the country of is a message sent to a stranger

## Fix

`store numbers as E.164 (+4915112345678) and return that from smsChannel({ numberOf })`

[Notifications](/error-codes#notifications)