function checkEmail(email)
{
  if ( email.indexOf(",") >= 0 ) { return false; }
  if ( email.indexOf(" ") >= 0 ) { return false; }
  if ( email.indexOf(".") < 0 ) { return false; }
  if ( email.indexOf("@") < 0 ) { return false; }
  if ( email.indexOf("@", email.indexOf("@")+1 ) >= 0 ) { return false; }
  return true;
}