I've done no programming with Mailman. I have a question whose answer is, I suspect, uncontroversial and well-known. I don't know it, though, and don't find it in very quick sweeps through the archives or documents. I'd be happy to have someone just tell me it's already been done, and point me to a reference.

The question is this: what's a good place to intercept postings? I want to feed all Mailman traffic--that is, all postings to any of the Mailman-managed lists on my host, but not administrative requests--through an external process (while still having all the usual e-mail deliveries, archiving, ... proceed as always). Where can I best do this? There are lots of choices; I could slide into the "/usr/local/mailman/mail/wrapper post ..." branch, or several places deeper. By "good", I think what I most want is a place that's very loosely coupled with Mailman. Ideally, I could overlay a new release of Mailman, and keep all my functionality either with no change, or a one-liner.