Scam-backscatter is a milter that prevents
backscatter on mail servers which don't host
mailboxes locally. It validates mailboxes by
verifying the recipient addresses hosted on a
different mail server.
Scam-grey is a milter that filters email
originating from MS Windows hosts. It provides you
the ability to mitigate the flow of unwanted email
from such hosts using greylisting.
Scam-protect is a milter which restricts the use
of your domain address in emails. Its aim is to
protect your users from phishing by rejecting mail
purporting to be from your domain.