Many important Exchange 12 details where announced at the Los Angeles Microsoft Professional Developers Conference (PDC), and in a follow-up blog by Terry Myerson General Manager, Exchange Server (see references).

Most of the information concerns the interfaces (APIs) used by third-party vendors to extend Exchange. The announcements highlighted the new E12 APIs and the future of the current Exchange 200x APIs.

As expected E12 ties into .NET and in many cases requires third party extensions to follow suite. Added to this some of the most key Exchange 200x APIs won't be supported, breaking applications interfacing through them. Most notably is the discontinued support to Transport Event Sinks, through which many server-side extensions plug into Exchange. This includes most anti-spam, anti-virus and other email hygiene/management applications.

Other APIs on the way out include the Installable File System (M drive), the EDK Gateway Interface, CDOExM, WMI, CDOWF and WebForms. Ironically, but not surprisingly, MAPI stays on board. For those who like me worked on Exchange extensions for many years will certainly remember how MAPI was shadowed by the newer Exchange 200x interfaces. Today MAPI strikes back and will wave goodbye to the younger, flashier, but easier to dispose of APIs. The huge heritage of MAPI applications clearly secured its permanence.

E12 elects Web Services, Managed Agents and Monad as its core APIs. The news doesn't come as a big surprise as Microsoft moves forward to deliver on its .NET vision. Nevertheless these big changes will unavoidably bring new challenges to add-on vendors, most of whom will have plenty of recoding to do.

The first public beta is targeted for the first half of next year.

References

Terry Myerson's Posting

PDC Presentation Slides