qmail-inject  sendmail
      \          /
       \        /
        \      /
    nullmailer-inject
            |
            |
            |
    nullmailer-queue
            |
            |
            |
        QUEUE/tmp -> QUEUE/queue
                         |
                         |
                         |
                  nullmailer-send
                         |
                         |
                         |
                    BIN/PROTOCOL