[otrs] Are there safeguards to prevent multiple customer signups?

Hello. Are there safeguards to prevent multiple customer signups via customer.pl? If so, how to enable them? I just want to set the system up so no one can 'play' with the system e.g. making several submissions with fake e-mails, etc.. Also, will new signups be re-sent if someone uses the 'refresh' button? Thanks.