Patches, you say? Well, I'm glad you really like source code, because that's exactly what you'll be dealing with to get all of this up and running. I've done it many times before manually and it takes around ten hours to do it.
While Aaron's point is that djb's code, vision and discipline are possibly unmatched (I concur on all counts), the software (principally qmail) is antiquated in the sense that nobody needs just that one part in order to run a semi-modern email system.
So, as you start downloading the .tgz for qmail and begin studying it like good campers, remember that this wonderful code is, by itself, not up to the job that it purports to serve.
-- Lots of love,
Someone who currently runs two qmail systems and will never go to the trouble of setting one up again