About the Metabase

This section contains the following conceptual information about the metabase:

• Metabase Keys
  
• IIS Admin Objects and ADs Paths
  
• Inheritance

Warning  Incorrectly configuring properties in the metabase can cause problems, including the failure of Microsoft SMTP Service. If you make mistakes, your mail serverÆs configuration could be damaged. Edit metabase properties only for the settings that you cannot adjust in the user interface, and be very careful whenever you edit the metabase directly.

Metabase Keys

The metabase hierarchy mirrors the structure of IIS and resembles a disk directory hierarchy in form. Each node in the metabase hierarchy is called a key, and each key contains subkeys, just as a directory contains files. Like a directory, each key has multiple properties (or configuration values) that are associated with it.

Key names in the metabase are not unique unless they are qualified by their metabase paths, just as different files with the same name are differentiated by the directories in which they exist. The keys are specified during programming or scripting using a metabase path and an object name; the syntax of the path and object name depends on the interface. To configure the properties stored at the keys related to Microsoft SMTP Service, use the ADSI path, called the ADsPath, and the IIS Admin Objects.

IIS Admin Objects and ADs Paths

An ADsPath points to an IIS Admin Object that is associated with a key. The ADsPath starts with IIS:// and then continues with either the term "LocalHost" or a specific computer name. It refers to the IIS Admin Object called IIsComputer, which is associated with the highest key in the metabase.

The path to an object associated with a metabase key lower in the hierarchy is an extension of the ADsPath to the computer key. For example, the ADsPath for Microsoft SMTP Service in your IIS installation would be IIS://LocalHost/SMTPSVC. The ADsPath for the first SMTP site in your IIS installation would be IIS://LocalHost/SMTPSVC/1. (You can also use the path IIS://MachineName/SMTPSVC/1 for access to the metabase on a different computer.)

The path syntax for IIS Admin Objects is as follows:

Note  For this version of Microsoft SMTP Service, there is only one instance of the service. Configuring properties at the SMTP service level has the same effect as configuring properties at the SMTP site n level (where n equals 1).

Inheritance

The hierarchy of Microsoft SMTP Service keys in the IIS metabase is as follows:

Note  Metabase keys are uniquely identified by ADsPath and IIS Admin Object; the names in this example of the hierarchy are not actual names of metabase keys.

The Machine key in the example above represents the IIS system executing on the computer. Properties set as this key, such as MaxBandwidth and MemoryCacheSize, affect overall operating parameters for IIS. The SMTP service key contains properties that affect all instances of the service (known as sites). The key for an individual SMTP site has properties specific to the SMTP site. Subordinate to each SMTP site key is a key that is associated with domains for that site.

When keys at different configuration levels share metabase properties, properties set at higher levels can be passed on to (or inherited by) lower configuration levels. All Microsoft SMTP Service metabase properties documented here are inheritable. However, inherited properties also can be edited individually at lower configuration levels. Changes made to property settings at a higher configuration level will not override changes made previously at the lower-level settings for an individual site or domain.

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