I have been having a problem with Plesk 10.4.4 using Postfix and the Plesk Spamassassin:
Mails from SASL Authenticated local domain users was being tagged as Spam by Spamassassin, with, amongst others, RCVD_IN_PBL.

I fixed this by doing two things:

1) adding the following to the /etc/postfix/main.cf
smtpd_sasl_authenticated_header = yes


2) adding the following to /etc/mail/spamassassin/local.cf (replace your.host.name with your hosts FQDN that shows up in mail headers)
header SASL_AUTH_RCVD Received =~ /\(Authenticated sender: .*@.*\) by your.host.name \(Postfix\) with/
score SASL_AUTH_RCVD -10
describe SASL_AUTH_RCVD received from SASL authenticated user

Problem fixed :)