I have been investigating an issue where Outlook instant search is not working. The environment is a Windows 2012 remote desktop server with Outlook 2013 and Exchange 2016 on premise.
When you try to do a search nothing happens. The list of emails in the folder stays the same. After an intensive search, most of the results were for users getting limited results, but this was different.
If you use the “Search tools ” > “Advanced Find”, the searches work as expected.
I uninstalled Outlook, rebooted the server, and installed Outlook again, but the problem was the same.
The Exchange server was checked and the Content Index State was fine, which I expected, as the Advance Find was working.
I was running out of ideas, so I thought it was time to get Microsoft involved.
The solution, it turns out, is quite simple but is not something I would have found.
Open the registry editor (of the affected computer) and navigate to HKLM\SOFTWARE\Policies\Microsoft\Windows\Windows Search.
Add a REG_DWORD of PreventIndexingOutlook and set to a value of 1.
Outlook Instant Search started working straight away after adding this entry.
Microsoft told me there is a fix for this in the next round of updates, which will be the February 2019 releases. They offered the registry fix as an instant fix instead of waiting for the updates.