MicrosoftExchange Server 2010 provides a library of classes that support the extension of Exchange transport behavior. These classes require Microsoft.NET Framework version 2.0. You can implement transport agents based on these classes by using MicrosoftVisual Studio .NET.
The Exchange 2010 installer installs and registers in the global assembly cache (GAC) the assemblies that are required for the development of transport agents. To begin implementing a transport agent, create a reference to the Microsoft.Exchange.Data.Transport assembly in a class library project.