2.2.3.2.10 ReplyBy Time

To set the value of the PidTagReplyTime property ([MS-OXOFLAG] section 2.2.3.1), clients MUST set the Reply-By header value, as specified in [RFC2156].

MIME readers MUST set the value of the PidTagReplyTime property to the value of the Reply-By header, converted to UTC time.

When processing TNEF messages, MIME readers MUST use a Reply-By header value specified in the MIME message in preference to the value of the PidTagReplyTime property specified in a TNEF message.