---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/api/errors/21601#article
headline: "21601: Phone number is not a valid SMS-capable inbound phone number"
url: https://www.twilio.com/docs/api/errors/21601
inLanguage: en
dateModified: 2025-12-18T21:40:49.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# 21601: Phone number is not a valid SMS-capable inbound phone number

Log Level: ERROR

## Description

The phone number you provided as the FROM field to initiate an outbound message is not an incoming phone number assigned to your account. Only phone numbers that you buy from Twilio can be used for outgoing messages. In particular, 3rd party phone numbers such as validated CallerIDs cannot be used to send messages.