2.1.3.1.1.1 To and Cc Recipients

To generate a To or Cc header, clients add a recipient (2) to the Message object and set the PidTagRecipientType property ([MS-OXOMSG] section 2.2.3.1) to the value that corresponds to the individual recipient type, as specified by the table of PidTagRecipientType property values in section 2.1.3.1.1.

MIME writers map recipients (2) to the To or Cc headers 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 2.2.1.3).

 ; 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 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 2.1.3.3.22, 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 2.1.3.3.22. For attached messages, MIME writers MUST copy all recipients (2), along with all their properties, into the attRecipTable attribute in the TNEF body part. This applies to attached DSN messages as well.