@James Chan_110, Thanks for posting in Q&A. Based on my researching, I find there's a setting in app protection policy may help. You can deploy app protection policy to outlook app and set "Sync policy managed app data with native apps or add-ins" to block to prevent policy managed apps from saving data to the device's native apps (Contacts,
https://learn.microsoft.com/en-us/mem/intune/apps/app-protection-policy-settings-ios
https://learn.microsoft.com/en-us/mem/intune/apps/app-protection-policy-settings-android
For BYOD device, you can consider creating Intune filter
https://learn.microsoft.com/en-us/mem/intune/fundamentals/filters
Hope the above information can help.
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