When information is received from a United States Postal customer concerning a possible mail fraud, it's reviewed to determin if a violation has occured. If the US Postal Inspection Service questions the legitimacy of a particular mailing or person(s), they have the authority to collect evidence from whomever to prove an intentional scheme to defraud. They base their evidence on a number of factors, including if whether use of the mail is part of a scheme. Evidence may then be presented to the United States Attorny for prosecutional consideration, or forwarded to the Postal Service General Counsel for additional prosecutional consideration.