User Configuration > Administrative Templates > Microsoft Outlook 2016 > Outlook Options > Delegates
User
HKCU\software\policies\microsoft\office\16.0\outlook\options\general
This policy setting allows you to store deleted items in the owner's mailbox instead of the delegate's mailbox. If you enable this policy setting, deleted items are stored in the owner's Deleted Items folder. For this setting to work correctly, the owner must also give the delegate permission to write to the owner's Deleted Items folder. If you disable or do not configure this policy setting, items deleted by a delegate are stored in the delegate's Deleted Items Folder instead of the owner's Deleted Items folder.