Helpdesk/Ticket System no login uses access key

Hi guys,

Can anyone recommend a script which houses an access key type system rather than the customer having to log in each time.

Ie. A ticket is created by the support department, the customer is emailed a dedicated access key link so they can access and respond to the ticket.

No log in or registration system at all, just a clean cut convenient ticketing system. - I use this and it works great.