---
page_type: error
code: 21603
message: >-
  21603: A 'From' or 'MessagingServiceSid' parameter is required to send a
  message
level: ERROR
product: Programmable SMS
---

## 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