Rebooting the  computer should not affect  LISTSERV in any way  as far as
these messages are concerned. I only see two explanations:

1. The reboot causes the mail server to resubmit these messages somehow.

2. The  messages were in  hold status (jobh) and  you have a  script that
   renames *.jobh to *.job before restarting LISTSERV.

Or of course they came back from the usenet gateway another time, etc.

LISTSERV should be stopped before a system reboot for a number of reasons
ranging from minor  (gives it a chance to checkpoint  statistics to disk,
etc) to  more important  (makes sure  no activity  is interrupted  in the
middle - you could end up with a posting processed twice, once to half of
the members and then once to everyone).

  Eric