2.2.1.57 PidTagSentRepresentingName Property
Type: PtypString ([MS-OXCDATA] section 2.11.1)
The PidTagSentRepresentingName property ([MS-OXPROPS] section 2.1017) contains the display name for the end user who is represented by the sending mailbox owner. If a sending mailbox owner is sending on his or her own behalf, this property MUST be set to the value of the PidTagSenderName property (section 2.2.1.51).