Plain-language definition
The HLR's note that a message is waiting for an unreachable subscriber.
Technical definition
When MT delivery fails for absent-subscriber reasons, the SMSC sends ReportSM-DeliveryStatus and the HLR sets MWD with the SMSC address; when the subscriber reappears the HLR alerts that SMSC.
Why it matters
MWD and AlertSC together make store-and-forward reliable without blind retries.
Last reviewed 2026-09-12 by the Guardivia QoS Engineering Team. Product facts on this page describe current capabilities; items marked “where supported”, “optional”, “integration” or “consultancy” are confirmed per deployment.