2.2.1.50 PidTagSenderEntryId Property
Type: PtypBinary ([MS-OXCDATA] section 2.11.1)
The PidTagSenderEntryId property ([MS-OXPROPS] section 2.1003) identifies an address book EntryID that contains the sending mailbox owner's address book EntryID, as specified by the address book EntryID ([MS-OXCDATA] section 2.2.5.2).