---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/api/errors/21667#article
headline: "21667: 'FallbackFrom' requires the Messaging Service to have an RCS Sender"
url: https://www.twilio.com/docs/api/errors/21667
inLanguage: en
dateModified: 2026-03-20T19:05:11.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# 21667: 'FallbackFrom' requires the Messaging Service to have an RCS Sender

Log Type: APPLICATION

Log Level: ERROR

## Description

`FallbackFrom` requires the Messaging Service to have at least one RCS Sender in its sender pool. `FallbackFrom` identifies the SMS or MMS sender that Twilio uses if RCS delivery fails.

### Possible causes

* The Messaging Service referenced by `MessagingServiceSid` has no RCS Sender in its sender pool.
* An incorrect `MessagingServiceSid` was provided (e.g., a Messaging Service configured for SMS-only use).
* The RCS Sender was removed from the Messaging Service sender pool after the integration was set up.

### Possible solutions

* Add an RCS Sender to the Messaging Service sender pool in the [Twilio Console](https://console.twilio.com).
* Verify that the correct `MessagingServiceSid` is being used.
* If RCS is not needed, remove `FallbackFrom` and send using the Messaging Service or `From` parameter without it.