DeliveryStatus

Message considered as read by a participant, if the message has been delivered and opened by the recipient in the conversation. The recipient must have enabled read receipts.

Message considered as undelivered to a participant, if Twilio has received a delivery receipt indicating that the message was not delivered. This can happen for many reasons including carrier content filtering and the availability of the destination handset.

Message considered as delivered to a participant, if Twilio has received confirmation of message delivery from the upstream carrier, and, where available, the destination handset.

Message considered as failed to be delivered to a participant if the message could not be sent. This can happen for various reasons including queue overflows, account suspensions and media errors (in the case of MMS for instance).

Message considered as sent to a participant, if the nearest upstream carrier accepted the message.

Message considered as queued, if it is waiting in a queue to be sent to an upstream carrier.