SA & amavisd & scanning attachments

Hi,

I'm not sure this is an SA question specifically, but perhaps an amavisd-new question that I hoped someone could help me to answer.

I'm using amavisd-new, postfix, and spamassassin for multiple domains. I'd like to know if it's possible to permit per-domain forwarding of certain attachment types while stripping others?

It appears $banned_filename_re is sitewide, but I thought there might be another way to permit attachments on a per-domain basis?

Thanks,
Alex