setup_reply (TMail::Mail)

    # File lib/action_mailer/vendor/tmail-1.1.0/tmail/net.rb, line 140
        def setup_reply( m )
          if tmp = reply_addresses(nil)
            m.to_addrs = tmp
          end

          mid = message_id(nil)
          tmp = references(nil) || []
          tmp.push mid if mid
          m.in_reply_to = [mid] if mid
          m.references = tmp unless tmp.empty?
          m.subject = 'Re: ' + subject('').sub(/\A(?:\s*re:)+/i, '')

          m
        end