client & server email filter

I am looking for someone to build a rule-based email filter that is easy to install. It should work on client and server levels and let the person installing choose: run on the client or run on a server. Must run on Windows as a plug-in to Outlook and work on all major email servers (which should be automatic if we're modifying an existing open source email filter). We will want to expand this eventually to other client email programs and operating systems. This app does not to be (and should not be) built from scratch. The easiest approach will be to modify an open-source filter that runs on the client and/or server, such as SpamAssassin. Our product is not a spam filter but it is conceptually similar -- it simply has to grab an email and look at it before passing it along. (Sorry, but I can't describe the exact nature of the product here). Qualifications: experience with email filters, modifying open-source code (especially email/spam filters), Outlook plug-ins. The ruleset for the filter is simple. The most important feature is the install: it has to be easy for an ordinary consumer, with none of the open-source "guts" showing. In addition to being dirt simple to install, it must provoke minimal tech support calls and be easy and/or unnecessary for a server admin to get involved. I would like to find someone to start within 7 days and finish by the end of January. Pay is flexible depending on your expertise in this area.