spam false positives

The Multiple Listing Service of our real estate clients sends cc’s of listing emails to the client, using the client’s own email address as the sending email address. This certainly goes into the spam folder right away, as it looks like a fake sending address. Where would I put the sending servers ip address into a whitelist to prevent this from happening? I am assuming I can contact the MLS and get the address of the sending server(s).

If you haven’t already, you may want to take a peek at the spam headers to determine exactly which rule is being triggered.

However, you can setup whitelists in SpamAssassin’s file found under /etc.