James,
There are two stages of filters:
- Front-door filters - these filters apply during SMTP envelope conversation. GreyListing happens at this stage.
- Downstream filters - these filters come into the picture once the entire email has been received and the Rules Engine starts assigning scores.
The concept of "Trusted SPF" does not exist until the second stage. Significant time-consuming processing occurs on the message before the second stage start. Many connecting clients will end-up in Timeout errors if this processing is done at the envelope level.
By the way, you can always add these domains in $INSTALL_DIR\config\ExcludedDomainsForGreyListing.dat . See http://xeams.com/GreyListing.htm for details
