It's a SCAM! If he sent you a check it is not real. DO NOT CASH IT!! You have several choices 1) send the check back to him; 2) take the check and envelope and anything else you have like emails or information on where to wire the excess money to your local Post Office and report it as mail fraud; 3) do the same as 2) but instead take it all you your bank and speak to whoever handles check fraud and ask them to investigate; 4) destroy the check and ignore any further contact from him.