Forum Discussion
Search in a shared mailbox still problematic
We've ran into the same issue at our organization. Unfortunately, we've tried all of the same actions as you without luck. We have a workaround in place that is a recommended "temporary" solution per Microsoft. It essentially disables FAST (Exchange online) search and tells the Outlook client to search local cache rather than look to the server. We've implemented it with users experiencing the search issue, and after a reboot, search is restored.
In Windows, right-click Start, and then select Run. In the Open: box type regedit, and then click OK. This will open the registry editor.
In the registry editor dialog box, find this subkey in the registry, and then click it:
HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Search
Click Edit > New > DWORD Value.
Type DisableServerAssistedSearch for the name of the DWORD, and then press Enter.
Right-click DisableServerAssistedSearch, and then click Modify.
In the Value data box, type 1 to enable the registry entry, and then click OK.
Close the registry editor, and then restart Windows.
Hope that helps until a permanent solution is released.