No email is deleted from your mailbox, unless you configure it to do so through the cPanel control panel. Any email reported by the system as spam will have the subject line modified and header records added (tagged) to indicate them so that you can automatically filter them from your inbox and place them in a separate folder so that you can check them at a later time. You can configure MailScanner to delete email marked as Spam and/or Definitely Spam for you, but beware of the issues in the following answers to spam related questions.