    # File lib/rmail/header.rb, line 430
        def to_string(mbox_from = false)
          s = ""
          if mbox_from && ! @mbox_from.nil?
            s << @mbox_from
            s << "\n" unless @mbox_from[-1] == ?\n
          end
          @fields.each { |field|
            if field.raw
              s << field.raw
            else
              s << field.name
              s << ': '
              s << field.value
            end
            s << "\n" unless s[-1] == ?\n
          }
          s
        end