with all of the unreachable ( bogus or otherwise ) addresses that we see
these days, could/should messages sent in acknowledgement:
 
Your command / message has been forwarded to the owner of <listname>
 
be sent out with a FROM/ERRORS-to/Return-path pointing to owner(listname ) ?
 
Seems that the owner, not the postmaster/listserv-maint, is the person
who needs to know message was undeliverable .....
 
?? - mike