When you enable this option, calendar actions are sent directly to the server instead of having to be synchronized from local storage. To fix performance issues that affect your Calendar, try the following methods. Also, determine whether any local network issues might be causing the problem. This includes issues that affect your local proxy server, firewall, or Internet service provider. Outlook uses an .ost file only if the Exchange email account is configured to use Cached Exchange Mode.

It also offers a filter option