# 21604: The destination 'To' phone number is required to send an SMS

Log Type: APPLICATION

Log Level: ERROR

## Description

### 'To' phone number is required to send a Message

Make sure to specify a valid phone number as the recipient of the message.

### Possible causes

* 'To' phone number is not specified
* Your request is not formatted as `application/x-www-form-urlencoded`

### Possible solutions

* Make sure to include a 'To' phone number
* Check that you are submitting your request as `application/x-www-form-urlencoded` and not as `json`.