From the ORF viewpoint, the most significant change that Exchange 2007 introduced is that it no longer relies on the Internet Information Services (IIS) SMTP Service for email delivery. Instead, it uses its own transport layer provided by the MSExchangeTransport service. As ORF integrates with IIS SMTP using a technology called SMTP Event Sinks, it cannot provide filtering for Exchange 2007 the same way it did previously.
Exchange 2007 uses a new integration technology called Transport Agents and ORF need to be changed significantly to be compatible with the new interface.
In this series series of articles I will talk about how the changes introduced by Exchange 2007 affect ORF and how do we deal with them.