X-MS-TNEF-Correlator mail header

TNEF Correlator
It is not always safe to assume that a TNEF stream found in a message belongs with that message and should be decoded. Many foreign messaging systems return the contents of a message along with nondelivery reports. Also, if a recipient is on a system that does not support TNEF replies to a message, the original TNEF stream will no longer be valid. To avoid this problem, some piece of information found in both the TNEF stream and the message header must be used to correlate them.

The Internet Mail Service adds a MAPI property, PR_TNEF_CORRELATION_KEY, to each outgoing message before converting it to TNEF format. The value stored in PR_TNEF_CORRELATION_KEY is also placed in a header in the SMTP message, called X-MS-TNEF-Correlator.

When the Internet Mail Service receives a message with a TNEF attachment, it looks for PR_TNEF_CORRELATION_KEY in the TNEF attachment. If it exists and matches the value of X-MS-TNEF-Correlator, then the TNEF is decoded. If they do not match or if X-MS-TNEF-Correlator is missing, then the TNEF stream is ignored.

If the PR_TNEF_CORRELATION_KEY property is not present, then the TNEF is decoded. This is necessary to retain compatibility with the Microsoft Mail SMTP Gateway and the Exchange Internet Mail Client, which do not use PR_TNEF_CORRELATION_KEY.

Support for the X-MS-TNEF-Correlator header field is not mandatory, but SMTP gateways that generate TNEF format can use PR_TNEF_CORRELATION_KEY and X-MS-TNEF-Correlator to detect cases where message contents are returned in reports. Your software should never require PR_TNEF_CORRELATION_KEY on messages it receives.

More info at http://msdn.microsoft.com/library/psdk/exchserv/backbone_767n.htm
http://linux.codemeta.com/archives/gnhlug_1999a_archive/0777.html

http://www.ccsf.cc.ca.us/Services/Help_Desk/handouts/howtotnef.htm

http://www.bugnet.com/alerts/bugalert_000719.html

Thanks alot...all my questions are answered.

Sorry I took so long getting back to you