21635: 'To' number cannot be a landline

You have attempted to send an SMS with a To number that is a landline.

The To number you provided is a landline number.

• Confirm that the number you are sending to is not a landline, using the Lookup API.
• Include ForceDelivery API parameter if you still want to send the message to this phone number. Please note that this does not guarantee the recipient number will be capable of receiving the message. Some international carriers may have a text-to-speech feature that converts the SMS to a voice call.