"He probably has been posting to the LISTSERV rather than the list.
You need to send a message
 
SERVE [log in to unmask]
 
to  LISTSERV so that the Listserver will start sending him notes
and allowing him to post."
 
 
I also follow-up with a note to the individual advising them what hapended and
how to prevent it in the future.
 
Rick Narad
Co-owner, Healthre