- Error when copying or moving stuff from the outlook.
- Outlook "inbox" is not visible to delegated user.

Issue -
Full Access permissions don't grant a user the ability to see private items. This issue occurs if the user has no specific delegation permission that is reserved for the mailbox owner.
To resolve -
To resolve this issue, Specifically, grant the user the "Delegate can see my private items" permission. To do this, click to select the Delegate can see my private items check box.
Click on Add and select the user from the AB, give appropriate permission to the user
tick "Delegate can see my private items"

-Thanks
@Roshan