My friend got charges with mail fraud when he mailed forged checks. What is mail fraud and what are the penalties?

Yes– using the mail in connection with a scheme to defraud is the crime of mail fraud.  Mail fraud is exclusively a federal offense.  It has two simple elements–  (1) intention to perform a fraudulent act, e.g., passing forged checks; and (2) using the mail to implement the fraudulent scheme. However, because mail fraud is a federal crime and forgery is a crime under state law it is somewhat unusual that the authorities are charging your son with both offenses. The forgery offense is prosecuted in state court and mail fraud  is prosecuted in federal court. Is there perhaps a prior history or pattern of conduct on your son’s part that has prompted the authorities to file the mail fraud charge?  On conviction a mail fraud penalty can range from probation to imprisonment in a federal facility and/or a substantial fine. It is essential that you have an experienced criminal defense attorney represent your son and ensure an appropriate resolution.