The line in your /etc/mail/spamassassin/local.cf is supposed to read:
You'll then need to run spamassassin --lint and restart qmail for the changes to take effect.
If you add the line to your tcp.smtp you can accept anything from the
server without checking it:
That should stop the server at address 18.104.22.168 from being run through the blacklists if that's where it's getting bounced, and you can then either whitelist it in spamassasin (above) or disable checks for it in simscan (http://wiki.qmailtoaster.com/index.php/Simscan)
Don't forget to restart QMail.
(Courtesy Jake Vickers)