danh Whether or not people can register themselves depends on Admin -> Settings -> Users, but if you're using AD it's probably better to leave the method at Private to avoid people registering with typos or their personal address. While you can do it manually, it's probably a bit of a faff. The method I used was to let people email the system for a while, and then 'register' them once the account had been created (as guest) from the email.
But yes, they need to be registered in order to log in... whether or not they can submit a ticket without registering depends on your settings.
