# 21664: 'FallbackFrom' cannot be used with a 'From' sender

Log Type: APPLICATION

Log Level: ERROR

## Description

You can't use `FallbackFrom` when `From` is set to a specific phone number or RCS Sender. To use `FallbackFrom`, send the message with `MessagingServiceSid` so Twilio can select the RCS Sender from the Messaging Service's Sender Pool.

### Possible causes

* You sent both `FallbackFrom` and `From` in the same request, and `From` contains an `E.164` phone number such as `+15105550100`.
* You sent both `FallbackFrom` and `From` in the same request, and `From` contains an RCS Sender such as `rcs:sender_id`.
* You used `FallbackFrom` without routing the message through a Messaging Service. `FallbackFrom` only works with `MessagingServiceSid`.

### Possible solutions

* If you want native RCS fallback, remove `From` and send the message with `MessagingServiceSid` plus `FallbackFrom`.
* If you want to send without RCS fallback, remove `FallbackFrom` and use `From` only. For direct RCS sending without fallback, set `From` to the RCS Sender ID and set `To` to the recipient's `rcs:` address.
* If you need a specific fallback sender, provide it in `FallbackFrom` and make sure it belongs to the same Account SID. The fallback sender must be a Twilio phone number in `E.164` format, an alphanumeric sender ID, or a short code.
* If you are passing a Messaging Service SID in `From`, move that value to `MessagingServiceSid`. This is the recommended way to combine Messaging Service sender selection with `FallbackFrom`.

#### Additional resources

* [Messages resource](/docs/messaging/api/message-resource)
* [Messaging Services](/docs/messaging/services#specify-a-fallback-sms-or-mms-sender)
* [Send and receive RCS messages](/docs/rcs/send-an-rcs-message#send-an-rcs-message-without-automatic-fallback-to-sms-or-mms)