[plug] sendmail + mailscanner RBL issue

[Ryan]

Hi PLUG,

At work I've set up sendmail and MailScanner (and spamassassin).  All
goes well, clients relay via the server when outside the network using
SASL authentication.

Sometimes a user dials up and gets an IP that is on an RBL list
(typically Telstra).  They send an email via the server and their
legitimate mail then gets quarantined as spam due to the RBL filters.

Does anyone else have this issue?  Does anyone know how I could
consistently bypass RBL checks for email that arrives via an
authenticated client?

White listing on addresses is not fool-proof and I can't white-list on
relay IP as they are random dialups from anywhere in the world.

Thanks,

Ryan