Hello, all! It's thread here with a quick description of how I have Mixxx stream out to dnbradio.com's shoutcast servers every Tuesday.
I run mixxx under the Ubuntu-based linux distribution, Crunchbang Linux. Using Jack, I feed Mixxx's main L/R outputs to the simple, console-based edcast (http://www.oddsock.org/tools/edcast_jack/), which is then able to encode the audio to mp3 in realtime and feed it up to the remote server.
I fire up Jack using the very simple frontend, qjackctl. Then I start Mixxx and set it to output its audio via Jack. After some straightforward editing of the edcast configuration file, I launch it, specifying the configuration file and the jack sockets to stream from, with something like this:
~/apps/edcast$ bin/edcast -c etc/edcast.conf PortAudio:out_0 PortAudio:out_1
And if all goes well, edcast will start telling you how many kilobits were sent up every second, until it is killed with ctrl+c.