@Tonito Dux, Thanks for posting in Q&A. Based as I know, it has some delay when apply the app configuration policy. If there's no app protection policy apply at the same time, it may need 24 hours to get his policy after the app is sign in with the user account.
For our issue, I think this can be when the contacts settings come during enrollment, the device has not received the app configuration policy yet. You can let it there and sign in outlook, then wait 1 day to see if the setting will be changed after the policy is received
Note: non-Microsoft link, just for the reference.
Hope the above information can help.
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