osTicket is a popular and free licensed open source
ticketing system...
Support Ticketing SystemAt GlobeSign, osTicket is a popular and free licensed open source ticketing system. It enables inquiries by creating them in the form of Mail, telephone and online forms into a convenient multi-role web interface. Administer, put together and back-up all your support querries and feedback at one place, and at the same time providing your customers with accountability and responsiveness they deserve.