The PidTagAddressBookParentEntryId property ([MS-OXPROPS] section 2.550) is the entry ID of the parent container in a hierarchy of address book containers. This property is not present if no parent container exists. Messaging clients use this property to expand and collapse a hierarchy of address book containers in an address book hierarchy table.
Because this property applies to a container in the hierarchy table, it is not present on objects in an offline address book (OAB). An OAB has its own structure for maintaining the hierarchy, using the OAB Public Folder Retrieval Protocol, as specified in [MS-OXPFOAB].