We need to create a system where the user enters only an email address. For a specific domain user receives an email with a generated password, and for all other domain receives a notification email to contact support. Password used to access a protected area of the site that is not available to the public. Also, the password can be used only once, ie. each time a user enters an email address, get a new password.
Any ideas how to make this system to Drupal 7?