I got the idea while stumbling upon this site, which describes the setup of a scanning server:
This document describes how to install Postfix, Amavisd-new, SpamAssassin, Pyzor, Razor, and DCC on one box running Fedora Core 4. The installation assumes that Postfix will not be the final destination of incoming mail. Also, no e-mail is sent through it to the outside world. It is a simple MTA that receives e-mail, scans it, and moves it to another MTA for processing.
Does this seems like something that is compatible with Scalix? If so, how would one set it up?