There are various status in the delivery report and their meanings are as follows:
Submitted- This status is displayed when SMS are submitted to our operator.
Sent/Pending- Sent/Pending is shown when SMS are forwarded from our operator but they still need approval from the operator on your end. If mobile is out of network till 4 hours until then the reports will be displayed as Pending.
Delivered- When the messages are received by the user successfully, delivered is displayed.
Blocked number- If a number is Black listed then the SMS will not be delivered to that number. You can see the blocked number in the section of Black listed number of Phonebook.
Opt-out- This is shown when an opt-out SMS is sent
Auto failed- If the messages are getting failed on the same number from a very long time then the system automatically fails it and added it to the AutoFailed directory and we don't charge for auto failed SMS.
NDNC- The NDNC status only comes under the promotional route as the Promotional route doesn’t allow sending SMS to DND number, so all DND numbers show this status and credits are also not deducted for the same.