> There are two things that can create this kind of problem:
 
This implies, but does not state categorically, that *only* two things
could be the cause.
 
> 1. If the logs are edited,
 
Marty Hoag, who (re)opened this discussion, is the person who would have
edited the log if that had actually been done.  He implies that he didn't
do it.  Who else could have?  The list owners are on remote systems and
unlikely to tamper with nitty-gritty stuff.
 
>    detect the separation between messages, it has to rely on the presence
>    of a  separator line  followed by a  valid header. If  a user  posts a
>    message containing a separator line  and another valid message header,
 
This sounds bizarre.  Maybe Marty wasn't looking for this particular
problem, but he *did* mention noticing that the first three messages
of the aberrant index were (would have been) dated from the preceding
month and had apparently been delayed en route to LISTSERV.  Surely,
this is an interesting coincidence and worth considering as a possible
symptom of a *third* way of getting mismatched message numbers.
                                            John