If your Outlook on Office 365 seems to run slowly, turning on the Outlook Cached Mode setting may improve performance. Cached mode creates a local copy (i.e., copy on your computer) of the data stored on the Office 365 cloud. Outlook accesses this cached copy for most operations, and that speeds up response times. If cached mode is turned off, all the data for operations is stored and retrieved from the cloud, and this potentially time-consuming process can cause sluggish performance. Another advantage of turning on cached mode is that you have access to downloaded data when you do not have a network connection. This means you can work on existing email offline until your network connection is restored.