I eagerly installed the IMF into my production Exchange environment on the day it was released and unfortunately tripped over my own eagerness. I have 2 servers in a front/back-end setup and I applied SP1 to my front-end and installed IMF there and everything was okay and both installs went smoothly. My backend Server because I had clients connecting to it I wanted to wait until I could schedule an outage to apply SP1 so I didn't upgrade this straight away. Since the IMF installed okay and I couldn't find anything that told me I needed SP1 on all my Exchange servers I decided to turned it on and test it out. Well it worked "sort of" the SCL was being set fine on all the messages going though and my Back-End server was responding to this but instead of just junking all mail with the default SCL of 8 it was junking every email. Going back over all the doco I couldn't see any problems with my install so I put it down to not having SP1 on my Back-end Server. Last night I managed to get SP1 on my Back-End Server and this morning re-enabled the IMF and everything is now fine. The anti-spam Infrastructure has been around since the release of 2003 so I still find it a little weird that I had this problem but so far I like the IMF.