Exchange 2003 SP2 IMF tuning

Okay, I should be working on the E2K7 book, but I'm playing. Sort of. I needed to tighten down my Exchange 2003 SP2 Intelligent Message Filter (IMF) a little more. All that holiday spam is creeping in my mailbox. And no one at work has time to manage an IMF archive. So, we started rejecting the mail that arrives with an SCL of 7 or above. But that is still quite a bit of spam that got through. Plus, the rejection message was not exactly friendly. If someone sends me a real message that just happens to get tagged as spam, this is included in the NDR:

This is an automatically generated Delivery Status Notification
Delivery to the following recipient failed permanently: jmcbee@domain.com
Technical details of permanent failure:
PERM_FAILURE: SMTP Error (state 12): 550 5.7.1 Requested action not taken: message refused

However, I was doing some research and found that you can customize this message. Locate the following Registry key:
HKLM\Software\Microsoft\Exchange\ContentFilter

In that Registry key, create a new REG_SZ value called CustomRejectResponse and then put the string you want to see in that value. Here is my new message:

This is an automatically generated Delivery Status Notification
Delivery to the following recipient failed permanently: jim@domain.com
Technical details of permanent failure:
PERM_FAILURE: SMTP Error (state 12): Your message looked like spam. Our filter rejected it. We are very sorry, but we hate spam. Please add some more text to your message or contact CTA support.

Actually, I will probably change that to have a URL once I can get someone to post me a page explaining why we rejected their mail and how they can fix it. The IMF is famous for rejecting very short mail, though. I might add to the Custom Weighting File something like CTACTACTA and say that if a message has that in the body it is never spam.

Anyway, if you are wondering how I'm testing the IMF to see the reject message, here is the easiest way. (I got this from the Exchange 2003 course #2400 class, by the way. Thanks David Elfassy!)

Go out to an external mail system such as GMail, create yourself a message, set the subject line to Low mortgage rates *** and set the message body to Cheap rates on your mortgage $$.