mailinglists spread SPAM

[cewi]

Hi,
we're using cpves since a couple of years and are very happy! But last months we got blacklisted a couple of times. Looking a bit deeper into it, I figured out that it has something to do with the Mailing-List feature of cpves. We have configured the mailing-list feature like described here: https://github.com/hggh/cpves/wiki/CpVES-MailingLists
We've lists with a mix of internal and also some external users (e.g. web.de, gmx, gmail). If the Mailing-List-E-Mail-Address receives SPAM, it seems that these mails were redistributed to the "external" List-members without SPAM-checking them before. Therefore gmx and gmail think were sending SPAM (what we in fact do).
Is there a way to route all incoming Mail through SPAMAssassin?
Thanks in advance!