3.2.4.5 Resending a Message

If a message fails to be delivered to all recipients (1), a client can mark this message as a resend message by setting mfResend in the PidTagMessageFlags property ([MS-OXCMSG] section 2.2.1.6). A client MUST also set the value of the PidTagOriginalMessageClass property (section 2.2.1.86) to resend the message.

The client sets the flags in the PidTagRecipientType property (section 2.2.3.1) of a recipient (1) to indicate whether that recipient is to receive the resend message. The server will attempt to redeliver the message only to the recipients (1) indicated.