W2H alerts study staff if a text did not go through with the error we received from Twilio, our text messaging vendor. Here are some common errors from text messages failing to be delivered through Twilio and what they mean:

• Error 30008 "Message Delivery - Unknown error": The carrier has returned a generic error message.
• Error 30005 "Message Delivery - Unknown destination handset": The carrier has reported the 'To' number is unknown, or no longer in service.
• Error 30003 "Message Delivery - Unreachable destination handset": The carrier has reported the 'To' number is unreachable - the device is likely powered down, out of the service area, or may not accept your messages.
• Error 30007 "Message Delivery - Carrier Violation": The carrier has filtered out your messages for delivery.
• Error 30004 "Message Delivery - Message blocked": Your message has been blocked from reaching the destination.
• Error 30006 "Message Delivery - Landline or unreachable carrier": The destination is a landline phone, or the destination carrier can't be reached.

If you encounter a message failure incident from Twilio that isn't on this list, please visit their website https://www.twilio.com/docs/api/errors#3-anchor to find out more.