This is an old problem but I have not been able to search emails and contacts recently.  I THINK it is related to the 14.5.4 update but do not have proof of this yet.  To troubleshoot, I have moved folders in and out of Private in Spotlight, rebuilt the Spotlight database, completely uninstalled Office and reinstalled it.  I have also rebuilt the Main Identity.  I am at a loss on what to do next.  Is anyone else having similar problems?  Any suggestions on a fix?