14101: Invalid "To" attribute

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

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

• 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 to inquire further.