I have Windows 10, cant remember if this happened before I upgraded. When processing email, it often freezes for a little while. I may have highlighted several emails to delete, or I may be doing something else, and it will freeze. Up at the top, it will say Mozilla Not Responding. I looked in help and found a thread where the same thing was occurring and the final solution which worked was to stop the Windows search service. I want to try that, but I don;t know where to find the setting to do that.