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

ERROR: 21604

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ERROR

Description

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Error - 21604

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'To' phone number is required to send a Message

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

Possible Causes

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

Possible Solutions

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  • 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.