Microsoft has confirmed the problem, stating that it is working on a solution to fix the issue, and has released a workaround to address it which is similar to an earlier bug.
This workaround involves setting up a registry key to disable Windows Desktop Search and switching to Outlook’s search engine.
To disable the Windows Desktop Search service for Outlook, users should follow a few steps, including right-clicking Start in Windows and then selecting Run.
In the “Open:” box users are advised to type “Regedit” after which they click OK. This will open the registry editor and they will click a subkey in the registry.
Then click Edit > New > Key and name the new key “Windows Search.” Users then select the new “Windows Search” key.
In the next step, click Edit > New > DWORD Value. Type PreventIndexingOutlook for the name of the DWORD, and then press Enter. Right-click PreventIndexingOutlook, and then click “Modify.”
In the Value data box, type 1 to enable the registry entry, and then click “OK.” Finally, Exit Registry Editor, and then restart Outlook.