class Mail::Message

def add_charset
  if !body.empty?
    # Only give a warning if this isn't an attachment, has non US-ASCII and the user
    # has not specified an encoding explicitly.
    if @defaulted_charset && !body.raw_source.ascii_only? && !self.attachment?
      warning = "Non US-ASCII detected and no charset defined.\nDefaulting to UTF-8, set your own if this is incorrect.\n"
      warn(warning)
    end
    if @charset
      header[:content_type].parameters['charset'] = @charset
    end
  end
end