2.1.3.1.4 Sender

To generate a Sender header, clients set the value of the PidTagSender property group (section 2.6.4).

MIME writers generate a Sender header by using the values of the PidTagSender property group. The order of preference in that property group is as specified in section 2.1.3.1.1. MIME writers SHOULD NOT generate the Sender header if the PidTagSender property group and the PidTagSentRepresenting property group (section 2.6.5) represent the same user.

When generating a TNEF message, MIME writers SHOULD<14> also copy the values of the PidTagSender property group to the attFrom attribute, as specified in [MS-OXTNEF] section 2.1.3.3.3, and the attMsgProps attribute, as specified in [MS-OXTNEF] section 2.1.3.3.21, in the TNEF body part.