Wherever possible, you should use Internet Service Manager or Internet Service Manager (HTML) to make changes to your Microsoft SMTP Service settings. However, the service uses several configuration parameters that, although contained in the registry, are not configurable using either version of Internet Service Manager. The registry entries listed in this section are specific to Microsoft SMTP Service.
Warning Using the Registry Editor incorrectly can cause problems, including the failure of Microsoft SMTP Service. If you make a mistake, the result might be damage to the configuration of your service. Edit registry entries only for settings that you cannot adjust in the user interface, and be very careful when you do so.
Before you modify the registry, it is strongly recommended that you read Part III of the Microsoft Windows NT Server Resource Guide in the Microsoft Windows NT Server Resource Kit, which describes in detail how to use and change parameters in the registry.
Note that many of the registry keys that existed for previous versions of IIS and Microsoft SMTP Service have been migrated to a fast-access, hierarchical database called the metabase. To find out more about the metabase, see Configuring Metabase Properties for Microsoft SMTP Service.