Please be informed that we encounter a issue that one of user unable to search email in Virtual Vault and reture "No matches found for xxx". As we check the configuring Windows search as follow link:
As the user is usning Win 10 and that is unable to expend Outlook then show "Vault - username" (as the attached Win_10) in indexing options under Control Panel.
May I know how to configuring Windows Search for Virtual Vault in Win 10
The short answer is that searching Virtual Vault items from outside of Outlook is not supported at all on Outlook 2013 and later, and only in certain circumstances on Outlook 2010. It's kind of a complicated intersection of Office version and Windows version, so I'll just link you to this article, where they made a pretty table of it.
Searching Virtual Vault items from Windows Search relies on the ability to search Outlook items more generally from Windows Search. Microsoft removed the ability to do this in Outlook 2013. Here is the document where Microsoft describes the change that removes the feature. CTRL-F for the phrase "Search Office items within the Office application." In short, Microsoft stopped letting you search Outlook stuff from outside of Outlook, and since Virtual Vault stuff is a subset of Outlook stuff, that stopped too.
You should still be able to search Outlook items, including Virtual Vault items, from the Search feature that is built into Outlook.
The most complete search of a user's archive will still be from the EV Search web page. Additionally, if you are content to search only among the archived items stored in the local Vault Cache/Virtual Vault, then you can use the built-in Search tool in Outlook, setting the scope to "All Outlook Items."