&LISTNAME is either the short or long name based on the value of
"List-Address=" and/or its system default. By default the long
("List-ID=") name is used if present. Typically on non-VM systems you
don't bother with "List-ID=" and only have one list name.
You can replace &MYNAMES et al with an arbitrary value using the .SE
instruction (which should be in the list owner's guide). This only lasts
for the duration of the particular message you are sending, of course.
Eric