2.2.1.61 PidTagTransportMessageHeaders Property
Type: PtypString ([MS-OXCDATA] section 2.11.1)
The PidTagTransportMessageHeaders property ([MS-OXPROPS] section 2.1051) contains transport-specific message envelope information for e-mail, as specified in [RFC2821]. For outgoing messages with recipients (1) who have an SMTP address type, and for incoming messages from a sender who has an SMTP address type, the client and server respectively MUST set this property to a copy of the beginning of the message stream as received from SMTP, up to the first blank line (double CRLF, as specified in [RFC5234].).