For Exchange 2007/2010, is there a header I can set outside of the Exchange organization, that once that message reaches the Exchange org, it will automatically be classified as spam?
The use case is such that an upstream system determined a message to be spam, but I'd prefer for it to go to a user's Junk E-Mail folder instead of being dropped.
Transport rule? IMF?
Thanks in advance
Messages are placed into the "Junk E-Mail" folder by the Information Store based on the Spam Confidence Level (SCL) assigned to the message.
You can use a transport rule to set the SCL as described in this article. Exchange doesn't "trust" SCL headers received in messages from third-party servers but the transport rule strategy, as described in this article, will cause Exchange to set the SCL based on another header value. Because you can do regex matching in transport rules you can get pretty flexible in how you interpret the information coming from the third-party filtering system.