node.js how to listen to port 25, 465 or 587 on MAC without error?

I'm trying to role my own SMTP server on node.js, however when I try to listen to port 25 I get:

    events.js:163
          throw er; // Unhandled 'error' event
          ^

    Error: listen EADDRINUSE :::25
        at Object.exports._errnoException (util.js:1034:11)
        at exports._exceptionWithHostPort (util.js:1057:20)
        at Server._listen2 (net.js:1265:14)
        at listen (net.js:1301:10)
        at Server.listen (net.js:1392:7)
        at Object.<anonymous> (/docfire/mailsvr.js:84:6)
        at Module._compile (module.js:571:32)
        at Object.Module._extensions..js (module.js:580:10)
        at Module.load (module.js:488:32)
        at tryModuleLoad (module.js:447:12)

I've tried launching node with 'sudo' and this worked once, but now it doesn't.

via SPlatten