A DLR is generated when the recipient mobile device acknowledges that it has received the message.
Technically, DLRs are URL call-backs for Delivery Reports. Instead of the gateway logging the activity, it will call-back the provided URL using a query string (at the end) with the parameters of the delivery report itself.
Delivery reports are a key component of the reporting metrics for SMS marketing campaigns. They can be used to flag issues with SMS delivery (no delivery reports received) or bad data (lots of undeliverable messages).
However, they are not an exact science as in some cases network operators cannot transmit DLRs, or they are blocked for some reason.
What does a DLR report include?
Every DLR includes one of the following four flags that relate to the message status:
- Delivered: The message was successfully delivered to the recipient’s device (although not necessarily seen).
- Scheduled: The message is scheduled for delivery but has not yet been delivered.
- Pending: The delivery process is in progress with the mobile operator, or may have stalled for some reason, which could include the recipient not having a phone signal, network issues, an issue with their subscription, or their phone is simply switched off.
- Undeliverable: While pending messages may well get delivered sooner or later, messages that are undeliverable will not. The message could have been blocked by the operator’s spam filters, the number may not exist, or the recipient’s subscription may have been suspended for some reason.