Microsoft Exchange Server 2010 SP1 Beta Transport Agents SDK June 2010 Released
This release of the Exchange 2010 Service Pack 1 (SP1) Beta Transport Agents Software Development Kit (SDK) provides new and updated documentation and samples for building applications that use Exchange transport agents. Use this SDK to help you develop collaborative enterprise applications for Exchange transport.”
Go get it here.
MCM: Exchange 2007 | MVP: Exchange Architecture