A delivery receipt (DLR), is a piece of information sent over the mobile network to the original sender of a message. This packet of information contains the delivery status of the message, whether it was successfully delivered or if the delivery failed. This makes delivery receipts invaluable in determining the status of your messages, as delivery receipts allow you to verify whether your SMS has been received at the destination phone.
1.1 - What are the most common delivery receipt status?
|Delivered||The message has been received at the destination phone and the operators have provided the information.|
|Sent||The message has been delivered to the carriers by PUSHTech, and PUSHTech is awaiting confirmation of message delivery from the relevant carrier.|
|Undelivered||After trying for a period of time, the operator was unable to deliver the message to the destination phone. Possibly caused by an invalid sender ID.
Confirm that the number is correct, that the phone is turned on and within reception range, and try again later or and within reception range, and try again later or with a different sender ID.
|Invalid Number||The destination number is invalid and our system cannot recognize it for delivery.
Common causes: the number is not in international format, entered incorrectly or is too short/long.
|Rejected||The message was successfully sent to the carrier for delivery, but was actively rejected. This is usually related to problems with an invalid sender ID in the destination network.|
|Expired||In the event that a mobile device is not reached, delivery will be reattempted for a period of time. Once the maximum retry period has been reached for the network to which the message is delivered, the status will be marked as expired and delivery will no longer be reattempted.|
|No Credits||Your account is out of credits. Buy more credits and send them again, or resend these messages from your outgoing message report.|
1.2 - How DLR works?
SMS messages are sent to network elements called Short Message Service Central (SMSC), which are responsible for final delivery to destination phones. When PUSHTech sends messages for delivery, they are sent with a delivery confirmation request for that message (when available).