Transport assurance means the guarantees a communication system provides about delivery, integrity, or receipt while a message is in transit. It can show that a message reached a destination, was not altered during transfer, or was handled by a defined process such as certified delivery or receipt confirmation.
In cyber security, transport assurance matters because it is easy to mistake proof of delivery for proof of trust. Attackers abuse that confusion in phishing, business email compromise, and other social-engineering attacks, where a message arrives through a legitimate channel but still contains false instructions. Defenders use transport controls such as encryption, message authentication, signatures, and delivery receipts to reduce tampering and support audit trails, but these controls must be paired with sender verification and business-process checks.