Botnet is a major source to disseminate email spam. Botnet related devices including master, C&C servers and infected computers are decentralized in the Internet, which causes big challenges for any party to identify botnets and know specific botnet-related information. Therefore, information sharing becomes a crucial factor to counter email spam sent by botnet. This Supplement provides a reference model which can be applied to the interactive gateway system for countering spam, in accordance with Recommendation ITU-T X.1243. In this reference model, countering spam gateways can share botnet-related information with each other. This Supplement mainly focuses on countering email spam sent by a botnet.