---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/api/errors/21603#article
headline: "21603: A 'From' or 'MessagingServiceSid' parameter is required to send a message"
url: https://www.twilio.com/docs/api/errors/21603
inLanguage: en
dateModified: 2026-03-11T18:38:39.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# 21603: A 'From' or 'MessagingServiceSid' parameter is required to send a message

Log Type: APPLICATION

Log Level: ERROR

## Description

The 'From' parameter in your API request to send an outbound message did not include a valid [Twilio Number](/user/account/phone-numbers/), [Alphanumeric Sender ID](https://support.twilio.com/hc/en-us/articles/223181348-Alphanumeric-Sender-ID-for-Twilio-Programmable-SMS), or [Messaging Service SID](/docs/messaging/services).

You can provide any of the above sender types in your From parameter. You may also provide a Messaging Service SID using the dedicated 'MessagingServiceSid' parameter, either instead of or in addition to a specific 'From' parameter.

### Possible causes

* You did not specify a 'From' parameter in your API request

### Possible solutions

* Specify a valid [Twilio Number](/user/account/phone-numbers/), [Alphanumeric Sender ID](https://support.twilio.com/hc/en-us/articles/223181348-Alphanumeric-Sender-ID-for-Twilio-Programmable-SMS), or [Messaging Service SID](/docs/messaging/services) as the 'From' parameter in your API request
* Specify a valid Messaging Service SID as the 'MessagingServiceSid' parameter in your API request