18.104.22.168.1.1 To and Cc Recipients
To generate a To or Ccheader (2), clients add a recipient (2) to the Message object and set the PidTagRecipientType property ([MS-OXOMSG] section 22.214.171.124) to the value that corresponds to the individual recipient type, as specified by the table of PidTagRecipientType property values in section 126.96.36.199.1.
MIME writers map recipients (2) to the To or Cc headers (2) as requested by clients. An exceptional situation occurs when generating MIME for an attached DSN message. A DSN message is one that has the following value for the PidTagMessageClass property ([MS-OXCMSG] section 188.8.131.52).
; The most common values are "REPORT.IPM.Note.NDR" and "REPORT.IPM.Note.DR" ReportMsgClass = "REPORT" 1*("." MsgClassToken) (".NDR" / ".DR") MsgClassToken = ALPHA *(ALPHA / DIGIT)
In that case, MIME writers ignore the recipients (2) of the attached message and instead populate the To header (2) of the attached message by using the PidTagReceivedRepresenting property group (section 2.6.3) of the attached message. If the properties in the PidTagReceivedRepresenting property group are not present, MIME writers use the PidTagReceivedBy property group (section 2.6.2) of the attached message.
When generating TNEF messages, MIME writers SHOULD NOT generate the attRecipTable attribute, as specified in [MS-OXTNEF] section 184.108.40.206.22, for the top-level message but MAY<9> generate this attribute for the top-level summary and legacy TNEF messages as specified in [MS-OXTNEF] section 220.127.116.11.22. For attached messages, MIME writers MUST copy all recipients (2), along with all their properties, into the attRecipTable attribute in the TNEFbody part. This applies to attached DSN messages as well.