An index for a language contains information on sorting and searching orders for folder hierarchies and the directory. The index is based on the language's conventions.
Installing a language index can minimize the confusion caused by differences in sorting and searching orders between languages; however, using multiple indexes can decrease server performance. To minimize the impact of multiple indexes, you can dedicate a single server for each index. You can also choose not to install languages that are not often needed or those that have sorting and searching rules similar to languages you have already installed on the server.
If an index for a Microsoft Outlook language is not installed on the server, the server uses an existing index that is similar to either the language you are installing or to the Windows NT Server language.
To install a language index