2.1.3.2.26 TNEF Correlation Key

When creating a new TNEF message, MIME writers choose a unique key relating the TNEF body part to its parent message. (MIME writers SHOULD use the value of the PidTagInternetMessageId property ([MS-OXOMSG] section 2.2.1.12) for this purpose.) The chosen value SHOULD<56> be written in the following two places:

• As the value of the X-MS-TNEF-Correlator header on the MIME message.

• As the value of the PidTagTnefCorrelationKey property ([MS-OXCMSG] section 2.2.1.29) in the attMsgProps attribute, as specified in [MS-OXTNEF] section 2.1.3.3.21, of the TNEF body part itself.

This pair of values SHOULD be used by MIME writers to validate that the top-level message and its TNEF body part do, in fact, belong to each other and are not (for example) the result of a non-TNEF-aware Mail User Agent (MUA) forwarding a message with an attached TNEF body part and retaining the attachment.