As the Internet of Things (IoT) develops and expands, management of IoT communications becomes a major challenge. A large number of IoT devices may be installed anywhere end users wish, then left unattended and be misused to attack others. In edge networks, it is difficult to properly prevent undesired communication without knowledge of the properties of an IoT service and its devices. In this paper, we argue that application service providers, developers, and network operators should 1) verify and know the authenticity of IoT services, devices, and their communications, and 2) prevent unwanted traffic from IoT devices in a trustworthy, scalable, and distributed manner. This paper proposes a Trust List that represents the distribution of trust among IoT-related stakeholders and provides autonomous enforcement of IoT traffic management at the edge networks by integrating blockchains and Software-Defined Networking (SDN). The principle of Trust List is automating the process of doubting, verifying, and trusting IoT services and devices to effectively prevent attacks and abuses. The proof of concept implementation and experiment of the Trust List using both public and private blockchains reveal its good practice and suggest studies for realistic deployment. © 2018 IEEE.