# 14101: Invalid "To" attribute

Log Level: WARNING

## Description

The To attribute does not appear to be a phone number that you can SMS

### Possible causes

* Invalid formatted number
* SMSing an un-validated number while using a Trial Account

### Possible solutions

* Check the number and make sure it is a valid 10 digit domestic phone number
* Confirm you have validated this number, if you are still using a Trial account, or upgrade your account
* Contact Twilio [customer support](/help/contact) to inquire further.