Ticksy is a very simple, straight-forward ticketing system, and it works like a charm.
In less than 30 minutes you could have your own ticketing system up and running. Don't expect a lot of options, customizations, workflows, etc. It just do exactly what they say: "Ticksy gives you all the tools you need—and nothing you don't—to provide top notch customer support."
Aside from the things that already cooking: Email Parsing & Cname, I would like to add to consider a simple review system to be included when a ticket is closed. That way we can know how satisfied our clients are. It could be something really simple like 3 options (good, regular, bad) and the ability to see the stats. Feedback is always important for any helpdesk department.