Exchange Server Cookbook

Chapter 7. Transport, Routing, and SMTP

Introduction

Microsoft made a radical departure from the Exchange 5.5 architecture when they designed Exchange 2000. The first obvious difference to most experienced Exchange administrators was the removal of the Exchange-specific directory service in favor of Active Directory, which is provided by the underlying Windows operating system. Microsoft also switched the native transport from X.400 to SMTP. To implement this change, they followed the pattern of using components already provided by the operating system.

Windows 2000 and 2003 include Internet Information Services (IIS), a modular framework that provides support for many Internet protocols including HTTP, NNTP, and SMTP. Exchange makes use of the IIS framework by extending the SMTP service with additional capabilities not present in the base IIS installation. Many advanced aspects of the Exchange system are controlled through the various IIS management mechanisms such as the IIS Management MMC plug-in and the IIS metabase. It is important to understand how the reuse of the IIS architecture affects the design and function of Exchange.

In Exchange 5.5, the SMTP implementation was provided by the Internet Mail Service, an add-on component that performed all the necessary translations between the internal Exchange message transport (based on the X.400 protocol) and SMTP. This translation was imperfect, given the differences between the two protocols. Each IMS instance functioned as a separate ...