What is the parent folder in Outlook Web? (Assigning retention policies)

[Mighty365]

Hi, I'm trying to assign a retention policy in Outlook Web to delete any received emails older than 1 month. Most folders (for instance, Deleted Items) are already set up to "use parent folder policy." Is the Inbox folder the parent folder to everything else? When I go to set a retention policy for the Inbox folder, it gives me various options for retention policies, including "use parent folder policy." Is there a parent folder to inbox?

[#2]

There is (the Root/Top of information store folder), however OWA does not expose it. You can use Outlook to assign a policy to it.