LISTSERV was looping on a bad return code from WAKEUP.  It seems that
following a system crash, a bad file showed up in a list and LISTSERV
grabbed it but WAKEUP or something was unable to process it.  LISTSERV
repeatedly sent over a hundred mail files and MSGNOH's to me and DANNO.
I was lucky to have been here and see it happen.  If I had not, it would
have surely filled the 9900 files maximum soon as it was generating mail
every second or two.  This would be in 82 minutes or less.  I purged the
offending file and everything is now OK.
 
Whenever WAKEUP returns an unknown return code, LISTSERV should keep
track of how often this happens in a certain period, and shutdown if
they occur too frequently, sending a final notice of such to the
postmaster(s).  No more that 2 such events per hour should be allowed
as just strange glitches.  Any more than that represents a problem.