You may want to consider creating a superlist and defining all of the
alumni lists as sub-lists of that list. When there is a need to send a
message to all subscribers on all alumni lists, send the message to the
super-list. This will completely eliminate the spamtrap issue. If there
are individuals subscribed to two or more lists, the use of a super-list
will also eliminate the multiple copies which those individuals now
receive. We make extensive use of super-lists and sub-lists, particularly
for course-related lists.

See http://www.lsoft.com/manuals/1.8d/owner/owner.html#2.13.11 for a
discussion of super-lists and sub-lists.

--
Paul Russell (ND & BSU dad)
Senior System Administrator
University of Notre Dame