If you make the list header say "Reply-To=list,respect", then each
submitter can override the default reply-to-list by including a Reply-to:
line in the header, which LISTSERV will "respect" (not replace).
This is the default, so you don't have to change anything unless the
list header has some other value for Reply-To=.
 
Mark R. Williamson, Rice U., Houston TX; [log in to unmask] or @RICEVM1