Hi,
Do you mean Dynamics 365 App for Outlook? According to my research, this is a modern Office add-in for Outlook.
To disable certain add-in via GPO, we could go to User Configuration/Policies/Administrative Templates/Microsoft Outlook 2016/Miscellaneous/List of managed add-ins.
You could find more details under Help.

Hope this is helpful to you.
Regards,
Perry
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