LazyMAPI

MAPI Properties

MAPI Property: PR_SENDER_ENTRYID
Description: Contains the message sender's entry identifier.
Property ID: $0C19
Property type: PT_BINARY
Area: Address

Remarks:
This property is one of the address properties for the message sender. It must be set by the outgoing transport provider, which should never propagate any previously existing values.
If no transport provider has supplied any sender address properties, the MAPI spooler attempts to fill them in by calling the IMAPISession::QueryIdentity method for an entry identifier. If no entry identifiers have been provided, the MAPI spooler an identifier corresponding to the string "Unknown" in this property.