2.2.1.9 PidTagSearchKey Property
Type: PtypBinary ([MS-OXCDATA] section 2.11.1)
The PidTagSearchKey property ([MS-OXPROPS] section 2.998) contains a unique binary-comparable key that identifies an object for a search. Whenever a copy of an object is created, the key is also copied from the original object. This property does not apply to Folder objects and Logon objects. This property is read-only for clients.