Web Ticketing Application

Hi all,
I’m looking for a hosted customer support ticket application. I was wondering if anyone could recomend one. Ideally it’d have the following:

1.The service would be hosted by the supplier.

2.Users email email address and automatically receieve a response with a unique ticket number.

3. Ideally this would also automatically forwared the tickets or notify an administrator of the tickets.

4. Logging, reporting functionality

5. All settings can be modified, e.g. if the administrator changes, the email address can be changed.

The budget is fairly tight, so ideally I’m looking that hundrets of Euro (or dollars) rather than thousands. Does anyone have any other suggestions of functionality that is on offer?

Thanks,
chuck