Where a DLR comes from
A delivery receipt is generated by the entity that last handled the message. On a direct operator route, the SMSC derives DELIVRD from the MAP delivery outcome returned by the serving MSC. On an aggregated route, the DLR you see may be generated by an intermediate supplier that received the message and forwarded it somewhere else. Some routes fabricate receipts entirely.
What a DLR cannot tell you
Even a genuine DELIVRD says nothing about what the handset displayed.
- Whether the sender ID was preserved, modified or replaced by a local number
- Whether the content, URL or encoding was altered
- Whether all parts of a multipart message arrived
- How long delivery actually took
- Which message centre delivered it and over which path
Measuring at the handset
Guardivia Honeypot SMS Testing and Route Assurance sends uniquely identified test messages to trap numbers on real SIMs and compares the received sender ID, content, encoding, parts, timing and message-centre information (where the device exposes it) with the submission and with gateway CDRs and firewall decisions. The result is a verdict backed by evidence rather than a status code.
A changed sender ID is treated as a strong indicator that must be correlated with route, GT and CDR data before the route is labelled grey; the platform is deliberate about the difference between what a handset can observe and what requires signaling records.
Related products
About the author: the Guardivia QoS Engineering Team is Guardivia’s internal group of telecom signaling engineers, SMSC and SMPP specialists, core-network engineers, security and fraud analysts, developers, DevOps, database, NOC, QA and interoperability specialists who design, build and support all Guardivia products.