If Outlook feels slow, it may be due to large amounts of email being loaded directly from the server. Cached Exchange Mode improves performance by storing a local copy of your mailbox on your computer, resulting in faster access and smoother operation.
1. Open Outlook and click on File in the top right.
2. Click Account Settings
3. Select Account Settings again
4. Select your email account and click Change.
5. Check “Use Cached Exchange Mode,” then select the time period of emails you want available offline under “Mail to keep offline.”
Note – Microsoft recommends setting “Mail to keep offline” to One Year in Outlook 2019 for most Exchange accounts, as this provides the best balance between Outlook performance, reliable and accurate email searching, and efficient disk space usage.
6. Select Next and Finish and restart Outlook.
Note - Please see attached instructions if you wish to save them to your device.