The username is typically name.surname [at] unitn.it and it is used to login to access the services. The username is typically name.surname [at] unitn.it (or variations) in combination with the UniTrento password.
You can use the widget in the myunitn website, to easily access to the “Google Apps” services. The already recognised user may access without inserting your password again.
You can access directly using the link http://mail.g.unitn.it/ , browsing on Google. In this case pay attention to the field required by the application: to access Google you are often required to have an email address. Therefore you need to use your “main email address” (you cannot access using an alias), which can be different from your username.