Hi,
As far as I know, this issue might be caused by word breaking behavior in Chinese Simplified wordbreaker. Such as "Tan Ah Kow" is broke into 'Tan' and 'AhKow'. Please try use fuzzy query for testing.
Moreover, which Outlook and Windows version are you used? Since this issue is related to Outlook client, we recommend contact Outlook IT Pro team so that you can get more professional suggestion. For your reference:
https://social.technet.microsoft.com/Forums/office/en-US/home?forum=outlook&filter=alltypes&sort=lastpostdesc
Hi Allen,
We are using a few versions of Windows, from XP to 8.1, and also Outlook, from 2007 to 2013, all same issues.
What is fuzzy query? I am not familiar. Is it a setting in Exchange or client?