Messages marked as "unknown" are those that are successfully sent but failed to receive a delivery receipt from the recipient's mobile carrier. If a message doesn't receive a delivery receipt after a specific amount of time, the message status switches to Unknown.

Delivery receipts are not always guaranteed from carriers. Typically when you see an Unknown message status, your message has been received by the recipient. It is normal to see this happen every once in a while, but if you are seeing it on every message this could be an indication that there is an issue with your phone number or our provider. If you have any concerns, contact TextUs Support for assistance.