This help section describes the role of the ORF Transport Agents in the ORF system.
ORF Transport Agents are lightweight components that connect Microsoft® Exchange 2007/2010 to the ORF Service, the actual filtering component of ORF. Transport Agents hook specific events of the email transport and report these events to the ORF Service, which tells them what to do, e.g., to reject the email.
See the Filtering Architecture topic for more information.