To access Cached Exchange Mode Settings:
- Open up your Outlook app.
- Click on "File" menu in the top left then click "Account Settings" then "Account Settings" again.
- Select your email account then click "Change...".
- Ensure "Use Cached Exchange Mode" is checked then click "Next".
- Use the slider to select what mail you want to keep cached on your computer.
- Click "Finish".
This will make Outlook store a local copy of your email on your computer. Keeping a local cache on the computer will improve your experience by providing quicker access to your most-accessed emails.