Microsoft releases so-called update rollups, which contain a number of fixes and modifications to make sure your Exchange servers are always up-to-date and error-free. You can download those update rollups yourself, or you can configure WSUS in your environment to get them automatically. If you want to know which update rollups have been installed on your Exchange server, you can go to Control Panel, Programs and Features, Select that you want to view installed updates, and you will see which update rollups have been deployed.