Plain-language definition
A message delivered to an application rather than a handset.
Technical definition
AT SMS is the SMSC leg that delivers MO or routed traffic to an ESME, typically via SMPP deliver_sm; in firewall architectures the AT leg is inspected alongside MO and MT.
Why it matters
AT inspection closes the gap where application-bound traffic could bypass content and policy controls.
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.