This looks like another "reserved IP" issue, as discussed in this thread: http://thread.gmane.org/gmane.mail.spam.spamassassin.general/62078
If you look at the original received header, it shows an IP address of 71.8.202.198, which spamassassin sees as a reserved, and thus trusted, IP. The above-referenced thread includes a fix for this issue.
I don't believe that little bug (caused by assignment of that netblock, which is fixed in 3.1) will affect this case (since 71.8.202.198 is a remote sender's address). At least it doesn't if I run the message through my setup after adding
trusted_networks 143.210.8.56 internal_networks 143.210.8.56
to my setup.
Daryl
