I have no idea whether Listserv changes its IP address, though it
sounds nuts to me: but we had McAfee here for some years and never had
the slightest trouble. If this is a school address, it's the network
administrator's responsibility to maintain the staff's access to
listservs. I recently had this problem with another spam filter at a
university ISP, regarding a list for university teachers I administer,
and the staff there was told something similar, until they raised hell
about it.
Go over the network administrator's head: she's not doing her job.
-- Russ
Russell Hunt
Department of English
St. Thomas University
http://www.stu.ca/~hunt/