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This update adds an option to enable new linguistics features and improves handling of Chinese, Japanese, and Korean (CJK) content for search.

More information

Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall the operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

Exchange Server 2016

This update applies only to Outlook Web Access (OWA) and Outlook 2016 in Cache mode only. This update is included in Cumulative Update 9 for Exchange Server 2016 and later cumulative updates for Exchange Server 2016.

A new language detector and improved processing of CJK content for search is available in this update, which is enabled by setting the following registry subkey to 1:


Word breakers perform linguistics analysis on all text for search. Language detection in search is used to select the best word breaker for the text that is being processed.

With this update a new and more precise language detector is available for indexing. In addition, text that contains a mix of CJK and other languages will have an increased chance of being detected and processed by a CJK word breaker. For example, an email message with 20-percent Chinese text and 80-percent English text should now be processed as Chinese as well as English.

There are two effects of this change:

  • The new language detector is more precise than the previous language detector, which improves word breaker selection for all items. This results in improved search recall.

  • Improved search results for CJK queries in mixed-language scenarios with CJK.

If the new option is enabled, it will only effect new items and email messages unless a mailbox move is completed.

Mailbox move example

In the Exchange Management shell, perform the following steps:

  1. Create a new mailbox.

    New-Mailbox -name user -UserPrincipalName
  2. Set up a new database.

    New-MailboxDatabase -Server contoso123 -Name DB1
    Mount-Database DB1
  3. Move a mailbox and re-word break.

    New-MoveRequest -TargetDatabase DB1 -Identity "user_name" -InternalFlags @("InvalidateContentIndexAnnotations")



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